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ENVIRONMENTAL ASSESSMENT FOR REHABILITATION OF
PIMBURATHTHEWA DAM
DAM SAFETY AND WATER RESOURCES PLANNING PROJECT
DSWRPP-AF/CS/QCBS/03-02
FINAL REPORT
OCTOBER 2015
MG CONSULTANTS (PVT) LTD
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TABLE OF CONTENTS
LIST OF FIGURES ........................................................................................................................... v
LIST OF TABLES .......................................................................................................................... vii
ABREVIATIONS .......................................................................................................................... viii
TEAM OF CONSULTANTS FOR EA STUDY ....................................................................................... x
1. INTRODUCTION ........................................................................................................................ 1
1.1 PROJECT DESCRIPTION AND JUSTIFICATION ......................................................................... 1
1.1.1 Background of the Project ..................................................................................................... 1
1.1.2 Project Location ..................................................................................................................... 4
1.2 SCOPE OF THE PROJECT AND ENVIRONMENTAL ASSESSMENT .............................................. 9
1.2.1 Scope of the Project ............................................................................................................... 9
1.2.2 Environmental Assessment Requirements ............................................................................ 9
1.3 OBJECTIVES OF THE STUDY ................................................................................................ 10
1.4 METHODOLOGY ................................................................................................................ 11
1.4.1 Mobilization ......................................................................................................................... 11
1.4.2 Scoping Meetings and Reconnaissance Visits ...................................................................... 11
1.4.3 Data and Information Collection .......................................................................................... 12
1.4.4 Baseline Surveys ................................................................................................................... 12
1.4.5 Identification and assessment of impacts, nature and magnitude ..................................... 13
1.4.6 Institutional Arrangements .................................................................................................. 13
1.4.7 Environmental Impact Analysis, Proposed Mitigatory Strategies and preparation of the
Environmental Management Plan (EMP) ..................................................................................... 14
1.4.8 Preparation of the Environmental Monitoring Plan (EoMP) ............................................... 15
1.4.9 Preparation of the cost estimate for implementation of the EMP and EMoP .................... 16
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1.4.10 Recommendations and Conclusions .................................................................................. 16
1.4.11 Documentation Procedure ................................................................................................ 16
1.5 EXPECTED OUTCOMES OF THE REPORT .............................................................................. 19
1.6 WORK PLAN ...................................................................................................................... 20
2. DESCRIPTION OF THE EXISTING ENVIRONMENT ...................................................................... 22
2.1 OVERVIEW ........................................................................................................................ 22
2.2 PHYSICAL ENVIRONMENT .................................................................................................. 22
2.3 BIOLOGICAL ENVIRONMENT WITH FLORA AND FAUNA ...................................................... 34
2.3.1 Existing Habitats and ecological significance ....................................................................... 34
2.3.2 Flora ..................................................................................................................................... 34
2.3.3 Invasive Species ................................................................................................................... 35
2.3.4 Fauna .................................................................................................................................... 35
2.3.5 Rare, Threatened and Endemic Flora and Fauna ................................................................. 35
2.3.6 Migratory Paths.................................................................................................................... 36
2.3.7 Proposed borrow area ......................................................................................................... 36
2.4 SOCIOECONOMIC ENVIRONMENT ..................................................................................... 37
2.4.1 Local Administrative Units in the Project Area .................................................................... 37
2.4.2 Land Use in Different Areas of the Irrigation Schemes ........................................................ 39
2.4.3 Demographic Data Relevant to the Project Area ................................................................. 39
2.4.4 Economic Activities of Project Related Population .............................................................. 40
2.5 OTHER WATER USES .......................................................................................................... 41
2.6 CURRENT ENVIRONMENTAL ISSUES OF THE PROJECT AREA ................................................ 42
2.6.1 Physical Issues ...................................................................................................................... 42
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2.6.2 Ecological Issues ................................................................................................................... 42
2.6.3 Socioeconomic Issues .......................................................................................................... 42
3. PROPOSED INTERVENTIONS ................................................................................................... 44
3.1 PROPOSED ENGINEERING INTERVENTIONS ........................................................................ 44
3.1.1 Resource and Material Requirements for Proposed Interventions of Pimburaththewa
Reservoir ....................................................................................................................................... 49
3.2 PROPOSED BORROWING ACTIVITIES AND IDENTIFIED BORROW SITES ................................ 54
3.2.1 Turfing Materials .................................................................................................................. 54
3.2.2 Earth ..................................................................................................................................... 54
3.2.3 Metal .................................................................................................................................... 54
3.2.4 Sand ...................................................................................................................................... 54
3.2.5 Gravel ................................................................................................................................... 54
3.3 PROPOSED INTERVENTIONS THAT COULD AFFECT NEIGHBORING COMMUNITIES ............... 54
3.4 PROPOSED INTERVENTIONS THAT COULD AFFECT THE NATURAL HABITATS ........................ 55
4. PROJECT INDUCED IMPACTS ................................................................................................... 56
4.1 IDENTIFICATION OF PROJECT INDUCED IMPACTS ............................................................... 56
4.2 QUANTIFICATION OF THEIR SIGNIFICANCE ......................................................................... 67
5. ENVIRONMENTAL MANAGEMENT PLAN ................................................................................. 68
5.1 GENERAL OVERVIEW ......................................................................................................... 68
5.2 IDENTIFICATION OF IMPACTS AND THEIR MITIGATIONS ..................................................... 68
5.3 PROCUREMENT OF MATERIAL NEEDED FOR IMPLEMENTING THE PROPOSED INTERVENTIONS
.............................................................................................................................................. 88
5.3.1 Material Sourcing ................................................................................................................. 88
5.3.2 Management of Borrow Sites .............................................................................................. 88
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5.3.3 Quarry Operations and Management of Quarry Sites ......................................................... 89
5.4 SAFETY ISSUES .................................................................................................................. 89
5.5 OPERATION OF LABOUR CAMPS ........................................................................................ 90
5.6 IMPLEMENTATION PROCEDURES OF PROPOSED MITIGATION ............................................ 91
5.7 INFORMATION DISCLOSURE AMONG STAKEHOLDERS ........................................................ 92
5.8 POST-CONSTRUCTION ACTIVITIES ...................................................................................... 92
5.9 FORMAL CLEARANCES AND APPROVAL NEEDED................................................................. 93
5.10 PROCEDURES FOR DEALING WITH CHANCE FINDS ............................................................ 94
5.10.1 Chance found Flora and Fauna .......................................................................................... 94
5.10.2 Chance found Archaeological Property ............................................................................. 94
6. MONITORING PLAN ................................................................................................................ 95
6.1 ENVIRONMENTAL COMPLIANCE AND MONITORING .......................................................... 95
7. COST ESTIMATION FOR ENVIRONMENTAL MANAGEMENT PLAN ............................................. 98
7.1 COST ESTIMATE OF ENVIRONMENTAL MANAGEMENT PLAN .............................................. 98
8. CONCLUSIONS AND RECOMMENDATIONS ............................................................................ 101
8.1 CONCLUSIONS ................................................................................................................. 101
8.2 RECOMMENDATIONS ...................................................................................................... 102
ANNEXURES ............................................................................................................................. 104
ANNEX 1: DETAILS OF THE FARMING COMMUNITY ................................................................ 104
ANNEX 2: DETAILS OF THE COST BENEFIT OF AN ACRE OF PADDY LAND IN PIMBURATTEWA .. 105
ANNEX 3: LOCATION MAP FOR THE IDENTIFIED QUARRY AND BORROW SITES FOR
PIMBURATHTHEWA TANK .................................................................................................... 106
ANNEX 4: FAUNA RECORDED FROM PIMBURATTEWA SITES................................................... 107
ANNEX 5: PHOTOGRAPHS – SOCIO ECONOMIC SURVEY ......................................................... 112
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LIST OF FIGURES
Figure 1.1: The seven reservoirs focused for the present cluster under the DSWRPP .......................... 3
Figure 1.2: Location map of the Pimburaththewa Dam (Close-up view from Topo sheet) ................... 5
Figure 1.3: Map of System B. Pimburaththewa is fed directly by the Maduru Oya LB main canal.
Pimburaththewa Reservoir is highlighted............................................................................................... 6
Figure 1.4: Location Map of Pimburaththewa Reservoir ........................................................................ 7
Figure 1.5: Land use of the area where Pimburaththewa Reservoir is located ...................................... 8
Figure 1.6: Proposed Approach and Methodology for the Study ......................................................... 18
Figure 2.1: Monthly average, high and low temperature in Aralaganvila near Pimburaththewa tank
area ....................................................................................................................................................... 23
Figure 2.2: Monthly average rainfall in Aralaganvila near Pimburaththewa tank area........................ 24
Figure 2.3: Topography of the Area (Note: Pimburaththewa and Maduru Oya (South of
Pimburaththewa) are both located below the 100 m contour line) .................................................... 26
Figure 2.4: Distribution of Soil Groups (Panabokke, 1975) ................................................................... 28
Figure 2.5: The catchment areas of the Reservoirs/Tanks considered for the present EA ................. 30
Figure 2.6: The satellite view of the catchment areas of the Reservoirs/Tanks considered for the
present EA ............................................................................................................................................. 31
Figure 2.7: Main Pimburaththewa Catchment ..................................................................................... 32
Figure 2.8: Pimburaththawa spill .......................................................................................................... 36
Figure 2.9: Rubble storage site ............................................................................................................. 37
Figure 3.1: Damages to the Spillway ..................................................................................................... 47
Figure 3.2: Erosion in spillway side ways .............................................................................................. 47
Figure 3.3: Damaged Spillway ............................................................................................................... 47
Figure 3.4. Spill tail areas collapsed completely ................................................................................... 47
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Figure 3.5: Damaged spillway ............................................................................................................... 47
Figure 3.6: Damaged Spillway ............................................................................................................... 47
Figure 3.7: Completely eroded parts of the Spillway ............................................................................ 48
Figure 3.8: Completely eroded parts of the Spillway ............................................................................ 48
Figure 3.9: Removal of shrubs needed on the rip rap rip rap in some areas ....................................... 48
Figure 3.10: Riprap damaged at some places ....................................................................................... 48
Figure 3.11: Seepages at D/S areas ....................................................................................................... 48
Figure 3.12: Seepage at D/S areas ........................................................................................................ 48
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LIST OF TABLES
Table 1.1: Data that need to be collected during the detailed study ................................................... 13
Table 1.2: Work plan for the proposed environmental study .............................................................. 20
Table 1.3: Tasks assigned to each team member and the responsibility ............................................. 21
Table 2.1: Summary of the fauna recorded in the rubble storage site and Pimburaththewa spillway site
.............................................................................................................................................................. 35
Table 2.2: Details of the local administrative units related to the project area ................................... 38
Table 2.3: Details of Project Relevant Population ............................................................................... 39
Table 2.4: Distribution of income generation activities among families in project related villages .... 40
Table 2.5: Details Expressed by the Farmer Leaders/Block Officers .................................................... 41
Table 3.1: Current issues at Pimburaththewa Tank .............................................................................. 44
Table 3.2: Photographic evidence for the identified issues .................................................................. 47
Table 3.3: Material Requirements for the repairs at the spillway and construction of the bridge across
the spillway ........................................................................................................................................... 49
Table 4.1: Possible impacts due to the proposed interventions and their significance ....................... 57
Table 5.1: Proposed mitigatory measures for the identified impacts .................................................. 69
Table 5.2: General safety issues that need to be addressed ................................................................ 89
Table 5.3: Formal clearances and approval needed ............................................................................. 93
Table 6.1: Summary of monitoring requirement .................................................................................. 96
Table 7.1: Cost Estimate of EMP ........................................................................................................... 98
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ABREVIATIONS
AMSL - Average Mean Sea Level
BPL - Below Poverty Level
CEA - Central Environment Authority
D/S - Downstream
DBH - Diameter at Breast Height
DEM - Digital Elevation Model
DS Division - Divisional Secretariat Division
DSWRPP - Dam Safety & Water Resources Planning Project
EA - Environmental Assessment
EMP - Environmental Management Plan
EN - Species - Endangered Species
EPL - Environmental Protection License
FD - Forest Department
FFPO - Fauna and Flora Protection Act
GND - Grama Niladari Division
GoSL - Government of Sri Lanka
GPS - Global Positioning System
GSMB - Geological Survey and Mines Bureau
GTOP030 - Global 30 Arc-Second Elevation Data-Set
ICTAD - Institute for Construction Training and Development
ID - Irrigation Department
IDF - Intensify Durative Frequency Curve
IDF Curves - Intensity Duration Curves
IEE - Initial Environmental Examination
IML - Industrial Mining License
IUCN - International Union for Conservation of Nature
KPI - Key Performance Indicators
MSL - Mean Sea Level
NEA - National Environmental Act
PM - Project Manager
PO - Project Office
PS - Pradeshiya Sabha
RB - Right Bank
STRM - Global Multi Resolution Terrain Elevation Data
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TEC - Technical Evaluation Committee
ToR - Terms of Reference
U/S - Upstream
VU Species - Vulnerable Species
WB – The World Bank
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TEAM OF CONSULTANTS FOR EA STUDY
Position Name Contact Details
Team Leader/Environmental
Engineer
Dr. Jagath Manatunge Mobile: 0718045546
e-mail: [email protected]
Natural Resource
Management Specialist
Prof. B. M. P.
Singhakumara
Mobile: 0714439300
e-mail: [email protected]
Ecologist Dr. Bandara Digana Mobile: 0777519671
e-mail: [email protected]
Socio-economist Mr. K. Jinapala Mobile: 0776595800
e-mail: [email protected]
Zoologist Prof. K. B. Ranawana Mobile: 0777356436
e-mail: [email protected]
Project Management MG Consultants (Pvt)
Ltd.
Address : 2nd Floor, 3, Swarna Place,
Nawala Road, Rajagiriya
Telephone: +94 11 2806028-9
Fax: +94 11 2806030
Mobile: +94 772 375822
e-mail : [email protected]
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1. INTRODUCTION
1.1 PROJECT DESCRIPTION AND JUSTIFICATION
1.1.1 Background of the Project
Recent studies have revealed that major dams of the country are aging and suffering from various
structural deficiencies and short comings in operation and monitoring facilities. This situation
threatens the safety and operational efficiency of the dams and their appurtenant structures and as
a result increases the vulnerability of downstream populations and socio-economic infrastructure if
breached. The Dam Safety & Water Resources Planning Project (DSWRPP) intends to address these
issues through its dam safety and operational improvement component with financing from the
World Bank. One of the development objectives of the proposed project is to improve the
development and management of water resources within the country, reduce water induced
hazards to public, and enhance the effectiveness of water related investments. The proposed project
intends to address this issue in 29 dams through its dam safety and operational improvement
component. These dams have been identified as high risk with respect to their appurtenant
structures and operational efficiency. Those dams are required to have immediate interventions so
as to decrease the vulnerability of downstream populations and socioeconomic infrastructure if
breached. This situation threatens the safety and operational efficiency of the dams and their
appurtenant structures and as a result increases the vulnerability of breaching.
The Dam Safety & Water Resources Planning Project (DSWRPP) intends to address these issues
through its dam safety and operational improvement component with financing from the World
Bank. The main objectives of the proposed project are to improve the development and
management of water resources within the country, reduce water induced hazards to public, and
enhance the effectiveness of water related investments. The proposed project intends to address
these objectives in 29 dams through its dam safety and operational improvement component.
For these objectives are to be met, there will be some interventions to be carried out. These
interventions may bring about environmental degradations, environmental issues in terms of
physical, ecological or/and social changes, alterations or irreparable losses. Hence, the project needs
to identify such environmental issues that are very likely and they should be reduced or curtailed as
practical as possible. This Term of Reference (TOR) sets out the problems associated with four dams
which are operated by the MASL and proposes remedial works. The dams have been selected based
on comprehensive risk assessment studies carried out as part of project preparation from a list of
vulnerable dams in order to ensure their structural and functional safety. Under this TOR it is
expected to carry out Environmental Assessments for the proposed interventions under the
DSWRPP for Ulhitiya-Rathkinda, Henanigala, Pimburaththewa, Bambarawana, Pussalavinna and
Moogammana (See Figure 1.1).
This report is prepared with the objective of assessing the environmental impacts due to the
proposed interventions proposed for Pimburaththewa Tank under the DSWRPP.
The World Bank (funding Agency) and Dam Safety & Water Resources Planning Project (DSWRPP)
have agreed that the five dams earmarked for rehabilitation under this study need only an
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Environmental Assessment (EA) together with an Environmental Management Plan (EMP) as the
proposed rehabilitation works do not entail any significant civil works.
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Figure 1.1: The seven reservoirs focused for the present cluster under the DSWRPP
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1.1.2 Project Location
This dam is located in System B agricultural zone managed by the MASL and is fed by Maduru Oya
LB main canal.
The administrative boundaries are:
District: Pollonnaruwa
Province: North Central Province
DS Division: Dimbulagala
The irrigable area under Pimburaththewa Dam is 6,516 acres and it is cultivated in both Yala and
Maha seasons. Fishing is the second most important livelihood activity that is based on water in the
Pimburaththewa reservoir.
The farmers in the irrigation system are organized in to organizations .The fishermen in the area also
have formed an organization for common benefits.
Water uses of Pimburaththewa Dam are:
Irrigation
Fishing - Fish production in system B is approximately, 5,000 ha of reservoir area: Maduru Oya Reservoir: 3,900 ha and Pimburaththewa Tank: 580 ha and the rest from smaller tanks.
Water for domestic purposes (bathing, washing, etc.)
A water supply scheme has been established in the immediate vicinity of the reservoir based on ground water
Figures 1.2-1.5 show the location of Pimburaththewa Reservoir.
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Figure 1.2: Location map of the Pimburaththewa Dam (Close-up view from Topo sheet)
Pimburaththewa Dam
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Figure 1.3: Map of System B. Pimburaththewa is fed directly by the Maduru Oya LB main canal. Pimburaththewa Reservoir is highlighted
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Figure 1.4: Location Map of Pimburaththewa Reservoir
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Figure 1.5: Land use of the area where Pimburaththewa Reservoir is located
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1.2 SCOPE OF THE PROJECT AND ENVIRONMENTAL ASSESSMENT
1.2.1 Scope of the Project
The technical scope of the study was to carry out environmental assessment based on the identified
interventions and their associated issues for the Pimburaththewa dam. The interventions to be
carried out during the rehabilitation work was defined at the inception stage of the project based on
the conceptual designs done by respective engineers and the environmental assessment related to
physical, ecological and socioeconomic environment will then be carried out.
1.2.2 Environmental Assessment Requirements
The strategies on which the environmental assessment conducted was based on the World Bank
Safeguard Policies and the National Environmental Regulations.
The World Bank Requirements
This environmental assessment was prepared pursuant to the World Bank’s Environmental
Safeguard Policies OP/BP 4.01 and that of Safety of Dams OP/BP 4.37.
The overall objective of the proposed environmental assessment was to carry out the following
conforming to the World Bank’s Environmental Safeguard Policies and Procedures. For each dam,
an Environmental Management Plan was prepared to address the objectives specified as given
below.
The World Bank Policies and Guidelines, pertaining to environmental safeguards that require
consideration under this project, as these will most likely be triggered, are as follows:
OP/BP/GP 4.01 Environmental Assessment
OP/BP/GP 4.37 Safety of Dams
OP/BP/GP 4.11 Physical Cultural Resources
OP/BP/GP 4.04 Natural Habitats
In addition, GP 4.11 is particularly applicable which details out the procedures to be followed for
chance find of physical cultural property. OP/BP 4.37 requires that the dam upgrading be designed
and its civil works be supervised by experienced and competent professionals.
Requirements under Environmental Regulations in Sri Lanka
The National Environmental Act (NEA) has made Environmental Assessments (EA) a legal
requirement for a range of development projects. A list of projects requiring an EA is prescribed in
Gazette (Extra Ordinary) No. 772/22 dated June 24, 1993. Accordingly, all river basin development
and irrigation projects excluding minor irrigation works requires an EIA, the guidelines are
ambiguous about the EIA requirement for upgrading and rehabilitation of existing dams. However,
agreement has been reached with the Central Environmental Authority (CEA) and Ministry of
Agriculture, Irrigation and Mahaweli Development that all dam upgrading and rehabilitation and
related activities financed under this project as well as any other activities that may lead to potential
adverse environmental impacts will be required to undertake an environmental impact assessment,
commensurate with the potential for environmental impacts and prepare detailed EMPs (including
a dam safety plan, where applicable) that will be included for implementation as part of the civil
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works Contractor’s contract documents.
The Fauna & Flora Protection Ordinance Act No. 49 of 1993 & its amendments: This Act provides
the protection, conservation and preservation of the fauna and flora of Sri Lanka. Under the Fauna
and Flora Protection Ordinance (FFPO), five categories of protected areas are established viz. Strict
Nature Reserves, National Parks, Nature Reserves, Jungle Corridors and Intermediate Zones
including sanctuaries. According to this Act, any development activity of any description what so
ever proposed to be established within a national reserve or within one mile from the boundary of
any national reserve, is required to be subjected to EIA/IEE, and written approval should be obtained
from the Director General, Department of Wildlife Conservation prior to implementation of such
projects. The FFPO follows a similar process as the NEA in conducting scoping, setting the TOR,
preparation of EA, review of EA and public consultation and disclosure. The decision of project
approval or disapproval is finally granted by the Director General of the Department of Wildlife
Conservation.
Forest Ordinance No. 17 of 1907 and subsequent amendments: The Forest Ordinance of Sri Lanka
is the law for conservation, protection and management of forest and forest resources for the
control of felling and transport of timber and forest related matters. The Forest Ordinance of No. 17
of 1907 amended by several Acts up to 1995 – Act 34 of 1951, No. 49 of 1954, No. 13 of 1966, No.
56 of 1979, No. 13 of 1982, No. 84 of 1988, and the new Act No. 23 of 1995.Under Section 4 of Act
No. 23 of 1995, the Minister is in charge of forests, has special powers to order and declare any
specified area of State land or the whole or any specified part of any reserve forest which has unique
ecosystems, genetic resources or a habitat or rare and endemic species of flora , fauna, micro-
organisms and of threatened species which need to be preserved in order to achieve an ecological
balance in the area by preventing landslides and fire hazards to human life, as a Conservation forest.
Under Section 5 of the Act, a Forest Officer of a specified area has special power to stop any public
or private way or watercourse in a reserved forest. It shall be lawful for the District Secretary to
determine the amount of compensation to be paid, in case that the water course injuriously affects
the interests or one or more individuals to whom on that account compensation should be paid.
1.3 OBJECTIVES OF THE STUDY
The objectives of this assignment are:
i. Identify and evaluate the potential environmental impacts that would arise as a result of the
proposed interventions
ii. Recommend appropriate mitigation measures to avoid, minimize, remedy or compensate for the
predicted negative impacts; and
iii. Provide a site-specific Environmental Management Plan that would give adequate project options
in terms of mitigation measures, project alternatives and a monitoring program to achieve overall
environmental sustainability of the project.
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1.4 METHODOLOGY
1.4.1 Mobilization
The team of consultants appointed by MG Consultants (Pvt) Ltd. commenced work on 10th February,
2015 with a meeting of team members where the Team Leader briefed the others regarding the
methodology for executing the consulting services. Documents required for the study were also
identified and team members requested to collect those pertaining to their areas of expertise. The
team leader thereafter prepared the Scope of Work for all team members to ensure that the
quantum of work to be carried out will be done in a uniform manner.
The requirement outlined in the TOR and the methodology was studied in depth and responsibilities
of each team member were identified. Topographic sheet were studied to observe the current land
use and the geographical features of the area.
Subsequent to the meeting, the Team Leader consulted the DSWRPP officials and obtained the
contact details of technical personnel who are in charge of respective dams. These technical
personnel were contacted appointment were made to meet them at respective offices and
requested them to facilitate the field visits and the reconnaissance field visit. The team visited all the
dams and their project areas. The team visited on individual capacity several times to gather and
collate necessary data from time to time.
1.4.2 Scoping Meetings and Reconnaissance Visits
The reconnaissance survey to Pimburaththewa Dam was carried out on 19th of February, 2015. The
team visited the dam and its project areas, accompanied by Mr. A. D. Wijeratne, who is the Block
Manager of Wijayabapura Block Office.
The main issues and the proposed interventions were identified during the reconnaissance survey
by having several meetings with key stakeholders in order to reach consensus on the issues and
mitigation measures required. Meetings were held with DSWRPP and MASL officials, farmer /
residents / in the project vicinity and fishermen engaged in inland fishery activities. Findings
gathered during these meetings helped to refine our approach to the study and to focus on the
following:
a. Proposed physical intervention – scale and nature of the intervention: Identification of physical
interventions including field inspections with the officers to assess the issues and magnitude of the
interventions.
b. Review of the work plan and Implementation schedule, including the time frame; Discussion with
relevant officers/engineers at the MASL and other relevant stakeholders at the site to familiarize
with the critical issues that are affecting the safety of the dams.
The details of the potential impacts due to proposed development interventions will be collected in
the follow up field studies to the reservoir area. The client’s confirmed list of development
interventions will be used for the impact identification with their magnitude in the next field studies
after Inception report is accepted by the client.
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1.4.3 Data and Information Collection
A detailed literature review of available data was done by the team of consultants at the project
initiation. Relevant data to identify impacts were collected during a reconnaissance visit as and when
available, and also desk studies. The data gaps were identified and the detailed field plan was
prepared to carry out baseline surveys.
1.4.4 Baseline Surveys
This basically dealt with collection of background data through primary and secondary sources.
However, where appropriate, surveys, investigations both in situ and ex situ were undertaken. The
study area for the assessment included the dam and bund area, peripheral area (500 m minimum),
burrow areas, work site and any area beyond the project site where there is potential for
environmental impacts and off site locations affected by construction activities. In this context, the
details of water users (agriculture and other such as fishing, domestic etc.) were collected to review
the diversity and magnitude of multiple water users in the Pimburaththewa reservoir.
Establishment of baseline conditions included establishment of present and future state of the
environment, in the absence of the project, taking into account the changes resulting from natural
events, and from any disaster that can take place due to dilapidated condition of dams and related
infrastructure.
An ecological survey was carried out to describe the existing baseline conditions to evaluate and
illustrate the magnitude of the problem. This identified major habitats / flora and fauna including
communities in and around the sites and to assess possible ecological impacts, existing
environmental problems within the proposed project areas. The study area confined to the specific
locations and immediate surroundings directly affected by the activities.
Fauna and flora found in all habitats of the project area were recorded by walking along transects to
get a rapid assessment of the species diversity. The conservation status of the species was
determined according to the National Red List of Sri Lanka (2012).
Social surveys and related studies were carried out covering all the stakeholders, especially the
farmer and fishing communities in addition to other water users (e.g., villagers who use the water
for day-to-day activities, and/or other purposes). Grama Niladharis, Economic Development Officers,
Samurdhi Niyamakas, officials of the farmer organizations, and any other governmental officers who
are directly or indirectly involved with the functioning of the dam and its water resources (such as
the Divisional Secretariat, MASL). The data on number of different water users such as farmers,
fishermen, families depending on tank water for domestic purposes (drinking, bathing and washing
etc.) were collected. Data and information gathered from such social surveys were used to identify
and assess social impacts. Mitigation measures were proposed with clear justifications based on the
expectations of the stakeholders.
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1.4.5 Identification and assessment of impacts, nature and magnitude
The EA identified environmental issues that may arise as a result of project activities especially
considering impacts that can arise affecting natural habitats, natural resources and also on the social
environment (especially, water users in the tank). Impacts can be classified into several categories
depending on the nature of impacts.
(a) Interventions that will cause moderate to significant impacts (if not mitigated)
(b) Interventions that will cause impacts that are direct, while some other may have indirect
impacts.
(c) Interventions that will cause impacts in the longer term rather than immediately following
the intervention:
(d) Activities of certain interventions will yield only minor impacts that are short term and easily
mitigated;
All the interventions and their implementation (Table 3.1) were closely studied and compared with
environmental elements in order to find out the impact caused by every activity on the every
environmental element. Physical, biological and social including socio-economic parameters were
considered for environmental elements. Some of the socio-economic parameters that were used for
monitoring the impacts are included below (Table 1.1) and there can be changes on these depending
on the findings of the detail field studies.
Table 1.1: Data that need to be collected during the detailed study
Criteria Indicators Data need
Livelihoods of the
farming community
No of farmers/ families to be affected
The land area affected ( encroached
land in the downstream and
upstream of the reservoir)
Details of cultivators under
the tank, yield and income,
details on encroachments of
the reservations.
Other indirect
livelihoods
No of drinking water users affected
No of fishing families affected
No of families used tank water for
bathing and washing
Data on the other water
uses in the tank
Disturbances to
other routine
activities of the
communities in the
project area
No of families in villages used the
tank bund top as access
Data on users of the tank
bund top as access road
1.4.6 Institutional Arrangements
The Acts, regulations, licenses, permits and other approvals that may be necessary for the
implementation of the proposed interventions were identified. These may include;
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(a) Irrigation Ordinance No. 32 of 1946 Irrigation (Amendment) No. 1 of 1951 Irrigation
(Amendment) No. 48 of 1968 Irrigation (Amendment) No. 37 of 1973 Agrarian Development
Act, No. 40 of 2002
(b) The National Environmental Act (NEA) No. 47 enacted in 1980 and NEA Amendment Act No.
56 of 1988
(c) National Environmental Protection and Quality Regulations under extraordinary gazette
notification No. 1534/18 and No. 1533/16 of 2008 under NEA section 32 & 23A, 23B
(d) Fauna and Flora Protection Act (FFPO) No.2 of 1937 amended in 1993 and 2009
(e) Felling of Trees Control Act No. 9 of 1951 as amended through Act No. 30 of 1953
(f) Water Resources Board Act, No. 29 of 1964 and (Amendment) Act, No. 42 of 1999
(g) Soil Conservation Act, No. 25 of 1951 and Amended No. 24 of 1996
(h) Agrarian Development Act No. 46 of 2000 (Section 32)
(i) Antiquities Ordinance No. 9 of 1940 and amendments
(j) Mines And Minerals Act (No. 33 of 1992)
(k) Mahaweli Authority of Sri Lanka Act of 1979
(l) World Bank Guidelines pertaining to Dam Safety & Environment Assessment Guidelines
It is also imperative that the proper institutional arrangement be made available for smooth
operations of the EMP. It is the Project Office that is in charge of the entire project and the client,
Irrigation Department would be solely responsible in getting the project implemented with a
selected contractor.
The contractor will be selected through a bidding process and the contractor is responsible in
implementing the EMP delineated herein this report. During the project implementation period, the
World Bank and the Project Office will evaluate the implementation of the EMP. Once the EMP is
implemented as per the World Bank Safeguard Policy Documents, review of implementation of EMP
would be done in order to ensure that all negative impacts are addressed successfully.
1.4.7 Environmental Impact Analysis, Proposed Mitigatory Strategies and preparation of the
Environmental Management Plan (EMP)
The objective of preparing the EMP is:
(i) To propose appropriate mitigation measures to reduce or minimize any adverse impacts
that have been identified, taking into account any associated constraints or consequential
environmental or social implications of such measures;
(ii) To identify, predict and evaluate the acceptability of the residual impact of the project after
the implementation of selected mitigation measures and to estimate and evaluate any
cumulative environmental impacts to which the project may contribute;
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(iii) To identify, develop and specify methods, measures and standards to be included in the
operational phases of the project to reduce environmental impacts to acceptable levels;
Appropriate mitigation will be proposed to ensure the identification of potential environmental
issues and social concerns early in the implementation of a proposed project to incorporate
necessary safeguards in project design in order to prevent potential adverse impacts by determining
appropriate mitigation.
A site-specific EMP that will provide mitigation strategies, project alternatives and a plan for
monitoring programme will be prepared. Proper management of the catchment and the watershed
is essential for ensuring continued economic benefits envisioned from the dam are met. These will
also be considered in the EMP.
1.4.8 Preparation of the Environmental Monitoring Plan (EoMP)
The Project Proponent needs to implement a comprehensive environmental monitoring programme
soon after implementation of proposed interventions. This is very crucial in order to assess the
performance or success of the implemented mitigatory measures. There are 3 basic environmental
monitoring tasks to assess the success of mitigation and identifying residual impacts. They are;
Pre-construction monitoring to determine the baseline conditions in detail to identify impacts and
mitigation measures and costs
Construction compliance monitoring, and
Post construction monitoring of maintenance and operational project activities.
It should be noted that during the construction phase both the contractor and the Project Proponent
should accept a major responsibility in undertaking the monitoring aspects with assistance from
competent authorities. With reference to undertaking environmental management issues,
monitoring aspects and implementation of mitigatory measures to prevent environmental impacts
an Environmental Monitoring Unit (EMU) should be established. This study will identify the
composition of this unit, its role and responsibilities etc.
In addition, for each significant impact, the environmental monitoring plan (EoMP) will propose:
- Mitigation measure
- Indicators/parameters to be monitored
- Frequency of monitoring – Time bounded monitoring
- Responsible entity for monitoring – institutional arrangements
- Responsible entity for supervising – institutional arrangements
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1.4.9 Preparation of the cost estimate for implementation of the EMP and EMoP
Cost estimates for implementing the EMP and the EoMP will be prepared.
1.4.10 Recommendations and Conclusions
Findings and suggestions of the EA Report will assist the Project Proponent in formulating an
environmentally friendly and a socially acceptable project and to achieve the broader objectives of
the proposed project.
1.4.11 Documentation Procedure
Draft final reports EMP for each Dam will be submitted summarizing the findings of the study and
will be finalized after incorporating the comments.
1. Inception Reports for each Dam
Including the Physical Interventions finally proposed to be carried out at the site (project activities),
Construction Methodology, Equipment to be used, Pre construction activities, etc., outline of the
Potential Environmental Impact on Physical and Social Environmental and outline of the proposed
Mitigation Measures. The inception report will also highlight the areas where impacts may be
possible due to proposed Dam safety project in Pimburaththewa Dam. The areas of impact will be
studied in detail in the follow-up field studies after Inception report is accepted by the client.
2. Draft Final Reports for each Dam
The Final Report will include the following:
A comprehensive Environmental Management Plan (EMP) to manage the onsite as well as offsite
environmental impact comprising the following.
(i) Mitigation strategies for each impact identified
(ii) Appropriate institutional arrangement to implement the proposed measures
(iii) Implementing schedule
(iv) Reporting procedures
(v) Cost estimates for implementing mitigation measures
- Environmental monitoring plan that will specify monitoring indicators to measure the
performance of the each mitigatory measure, monitoring mechanism and frequency.
- Clearance approvals needed by the project prior to its implementation
- Recommendations on the adequacy of the assessment
- Final Conclusions and recommendations regarding environmental viability, of the
project based on the findings
- Annexures and Appendices
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3. Submission of Final Reports
The Final Report will be submitted within two weeks after receiving comments from the client once
the TEC evaluates and reviews the Draft Final Report. The final report will be reviewed by the World
Bank as well.
The main activities to be followed to complete above deliverables are summarized in Work Plan
given below (Table 1.2).
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Figure 1.6: Proposed Approach and Methodology for the Study
Establishment of the baseline:
(i) Physical Environment (Topography, Geology and Soil, Meteorology, Hydrology, Land use and Water and Air Quality etc.)
(ii) Social surveys (iii) Ecological Surveys including
migratory paths
Collection of data and information (mainly from MASL);
Clarification sessions with the Client; Meetings with other
Stakeholders
Identification of proposed project interventions / Activities as
outlined in the TOR for the Study
Report
Identification of potential impacts during:(i) Project
Preparation, (ii) Implementation of individual interventions,
both identified and proposed (iii) resource consumption, (iv)
handling and disposal of waste, (iv) implementation schedule
Assessment of magnitudes of impacts and interventions and
evaluation of the impact significance
Identification and development of mitigation measures and
preparation of the Environmental Management Plan (EMP)
plan
Preparation of the Environmental Monitoring Plan (EMoP)
Preparation of Cost estimates for implementation of the
EMP and EMoP
Conclusions and Recommendations
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1.5 EXPECTED OUTCOMES OF THE REPORT
The expected outcomes are categorized as follows.
(a) Comprehensive Environmental Management Plan (EMP) to manage the on-site as well as
off-site environmental impacts
(b) An environmental monitoring plan that will specify the monitoring indicators to measure
the performance of the each mitigatory measure, monitoring mechanism and frequency
(c) Clearance approvals needed by the project prior to its implementation
(d) Recommendations on the adequacy of the assessment
(e) Recommendations regarding the environmental viability of the project based findings
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1.6 WORK PLAN
The steps described above can be summarized as a work plan as follows (Table 1.2)
Table 1.2: Work plan for the proposed environmental study
ACTIVITY
Month 1 2 3 4
Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1. Project initiation, Meetings with
DSWRPP and Engineers of MASL
2. Data and Information Collection
3. Reconnaissance surveys and field
visits
4. Preparation of Detailed
Methodology and Scoping of
environmental issues
5. Establishment of the baseline
environment
6. Identification and assessment of
impacts, nature and magnitude
7. Identification of Mitigation
Strategies and preparation of the
EMP
8. Preparation of the Environmental
Monitoring Plan (EoMP)
9. Preparation of the cost estimate
for implementation of the EMP
and EMoP
10. Recommendations and
Conclusions
11. Receiving Client’s comments
12. Drafting and Submission of Reports
1 2 3
Note: Submission of Reports:
1. Inception Report – at the end of Week 2
2. Draft Final Report – at the end of Week 10
3. Final Report – at the end of Week 14
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Table 1.3 provides the details of the tasks assigned for each team member including the team leader.
All the key experts in the Consultancy Team have the qualifications and the experiences as stipulated
in the TOR.
Table 1.3: Tasks assigned to each team member and the responsibility
Main Discipline/Task Key Expert Responsible
Coordination of the entire assignment Team Leader and Support staff
Preparation of overall methodology Team Leader
Detailing the interventions and Scoping of environmental
issues to identify impacts
Activities related to environmental (physical) aspects
Environmental Engineer/ Natural
Resources Management
Specialist/Chartered Civil Engineer
Meeting with stakeholders, including officials from
DSWRPP and MASL (including TEC meetings)
The entire team led by the Team
Leader
Description of the baseline:
- Physical environmental aspects
- Ecological/Biological impacts including migratory
mechanisms
- Sociological aspects
Environmental Engineer
Ecologist and Zoologist/ Faunal
Specialist
Sociologist
Drafting EMP and EoMP:
- Physical environmental aspects
- Ecological/Biological impacts
- Sociological/Economic aspects
Environmental Engineer
Ecologist and Zoologist/Faunal
Specialist
Sociologist
(input from Natural Resources
Management Specialist as needed)
Calculation of costs; Drafting Conclusions and
Recommendations
Team Leader with inputs from
other key experts
Drafting of the reports Team Leader with contribution
from other team members
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2. DESCRIPTION OF THE EXISTING ENVIRONMENT
2.1 OVERVIEW
It is imperative that the existing environment in the project area and the borrow areas are identified
in terms of different environmental elements. In order to perceive the likely alterations of the
existing environment due to the proposed interventions present status of the existing environment
needs to be recorded and then the impacts on such elements need to be discussed.
In general, the entire existing environment is described in three main components, namely, physical,
ecological and socioeconomic environments respectively. Data were collected focusing on these
three components and are presented below.
2.2 PHYSICAL ENVIRONMENT
The south part of the project area, occupied by that portion of the Maduru Oya basin which drains
to the Maduru Oya reservoir, is separated from the Mahaweli Ganga valley by a north–south line of
hills of height up to about 670 m above sea level. These hills are Precambrian in origin, in common
with the underlying formations throughout the project area. The link tunnel that diverts water from
the Mahaweli Ganga into the Maduru Oya reservoir, and the subsequent cascade system (to which
Pimburaththewa tank belongs to) penetrates this line of hills. A spur from the northern end of this
range traverses the Maduru Oya valley in a generally southeasterly direction.
a. Climate
The Pimburaththewa tank is located in the Maduru Oya basin, which falls within the dry zone of Sri
Lanka, where notable dry season occurs with an annual rainfall under 1,900 mm. The dry climatic
conditions are said to be prevailing most of the time where cooler climate is expected only in the
northeast monsoon period.
b. Temperature
At an average temperature of 28.7 °C, May is the hottest month of the year. In January, the average
temperature is 25.1 °C. It is the lowest average temperature of the whole year. Relatively minor
temperature fluctuations are normally experienced compared with wider fluctuations in
precipitation and streamflow. The variation in annual temperature is around 3.6 °C.
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Figure 2.1: Monthly average, high and low temperature in Aralaganvila near Pimburaththewa tank area
(Source: http://en.climate-data.org/location/765864/)
c. Rainfall
The Maduru Oya basin experiences a tropical climate, falling under the influence of the northeast
[December to February] and southwest [May to September] monsoons. The northeast monsoon
(Maha) brings most of the annual rainfall, and therefore runoff, in the catchment area. The
southwest monsoon (Yala) is typically dry due to the orographic effect of the Central Highlands of
Sri Lanka. Rainfall in the inter-monsoon periods can be caused by either convective or cyclonic
storms. Relatively minor temperature fluctuations are normally experienced compared with wider
fluctuations in precipitation and streamflow. The latter fluctuations have important implications for
the development of rain fed and irrigated agriculture.
It is envisaged from the Figure 2.2 that the substantial rainfall in the project area occurs in the first
and second inter-monsoon periods falling in between March to April and October to November,
respectively. The highest average monthly rainfall recorded during last 5 years ranged between 380
- 420 mm. Precipitation is the lowest in June, with an average of 18 mm. Most precipitation falls in
December, with an average of 412 mm. Annual average rainfall is around 1,900 mm. Between the
driest and wettest months, the difference in precipitation is 394 mm.
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Figure 2.2: Monthly average rainfall in Aralaganvila near Pimburaththewa tank area
(Source: http://en.climate-data.org/location/765864/)
d. Wind
Wind data has not been recorded continuously in the vicinity. The Welikanda Meteorological Station
has no data collected for Wind after 1979.
The average wind patterns on a typical day would be between 5 – 20 km/h. However, this can rise
to about 30 – 35 km/h during the north east monsoon periods. Occasional high winds can be
expected any time during September – November and during mild troughs or cyclonic circulations
e. Topography
The general topography of Sri Lanka comprises of three distinctive peneplains or erosion plains made
up of a central highland massif rising above 2,500 meters in altitude and a low gently undulating
plain surrounding it and extending to the sea. The lowest peneplain extends from the coastline to
approximately 20-30 kilometres inland in a steep step of about 300 meters above mean sea (MSL).
Maduru Oya basin is located in the Eastern Province, lies within this lowermost peneplain. The
landscape in the vicinity of the site is characterized by flatlands with almost no altitude changes
partly due to the fact that the land has already been cleared and prepared for the cultivation,
secondary development with people in-migrating to these areas recently. There are stepped lands
of 2~3 meters in height and exposure of reddish soil in some parts of the area. It is evident from the
location and contour maps that Pimburaththewa is aligned in the northeastern direction, in parallel
to the pre-existed (natural) flow direction of Maduru Oya.
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According to the present topographical variation, the downstream of the tank is characterized by
undulating slopes with 2.5% – 4.5% surface gradient in north-west direction. There are isolated
hillocks which have altitudes upto of 210 m MSL. According to the pre-existed topography, the
elevation in the area is approximately 60 – 80 m MSL with a gently sloping landscape in the north-
west direction and also towards the southeastern direction.
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Figure 2.3: Topography of the Area (Note: Pimburaththewa and Maduru Oya (South of Pimburaththewa) are both located below the 100 m contour line)
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f. Soil and Geology
The geology of the area is characterized by Precambrian rocks. They have given rise to a mature,
mantled and undulating peneplain which mere imperceptibly to the north and northeast into the
pleistocene and Miocene sediments of the coastal plain. Large, prominent and isolated erosion
remnants and prominent rides rise to heights of over 400 m [Gunner’s Quoin] above the general
level of the surrounding plain. The elevation of the latter varies from about 80m above sea level in
the south to under 30 m in the extreme north. The mantle covering the peneplain rock is generally
thin and sometimes nonexistent, as in areas of rock knob plain and outcropping flat rock.
Two very different soils have developed on the Precambrian rocks. On those rice in ferromagnesian
minerals, moderately deep to shallow (100 cm), reddish to brown, sandy clay loam soils have
developed, on slopes which often exceed 2 percent and sometimes 4 percent. These soils normally
occur in association with prominent rock outcrops. On the rocks relatively poor in ferromagnesian
minerals but rich in quartz, moderately deep to shallow, grey brown, loamy sand and sandy loam
soils occur. These overlie impermeable rocks and usually occur on slopes not exceeding 4 percent.
The soils of the upper slopes tend to be ‘moderately well’ to ‘well drained’ while those of the lower
slopes tend to be ‘imperfectly drained’.
Associated with these soils are ‘imperfectly’ to ‘poorly drained’ bottomland and old alluvial soils of
variable but usually sandy texture. These old alluvial soils are not necessarily associated with the
present – day drainage. A relatively wide band of ‘imperfectly’ to very poorly drained’ recent
alluvium [with the exception of a low, narrow, moderately freely draining levee soil occurs along the
Maduru Oya and the Mahaweli Ganga.
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Figure 2.4: Distribution of Soil Groups (Panabokke, 1975)
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g. Hydrology
The Pimburaththewa sub-catchment and the stream network contributing to the flows are located
within the Agro-ecological Region DL2, in the Hydrological Region 2.
Pimburaththewa Tank is located in the Northern part of the main catchment Maduru Oya Basin
(Figures 2.5, 2.6 and 2.7). The main basin consist of a catchment of 1,452 km2, and characterized by
a series of reservoirs in a cascade pattern along main channels and their tributaries, associated main
supply, distributary and return flow canals and their flow control structures including slices, gates
and minor anicuts.
The main hydrologic data required for the hydrological and hydraulic assessments apart from the
topographic information are;
Rainfall Intensity-Duration-Frequency Curves (IDF Curves) for catchment areas
Information on runoff coefficients and time of concentration
The site is situated in the belt of monsoon climates and governed by its tropical location as well by
the monsoonal regime, thus rainfall exhibits a strong seasonal variation. More than 50% of the total
rainfall is received during the Second Inter Monsoon and North-Eastern Monsoon (October to
December).
Except for the low-lying downstream catchment sections (60 - 80 m AMSL) in the most downstream
of the Maduru Oya Basin, the majority of the eastern coastline is covered with a narrow ridge of
mountain protruding above 200 m rising out of flat terrain leading to invert/reverse flow conditions
at several sections south-east. However, the Pimburaththewa sub-catchment is located in the
further upstream (80-100 m AMSL) and away from the downstream regional floodplain. Therefore,
the sub-catchment area is presumably not subjected to any flooding under seasonal monsoonal
storm event, except for extreme events where backwater flows from downstream accumulation due
to flow constrictions may cause localized temporary inundation in some areas. Historical flood data
are not available in the area.
The topographic data with contours and road layout has been obtained from the Survey
Department. Topographic maps with 1: 50,000 scale were primarily used (1: 10,000 maps were not
available) together with the collected Global Positioning System (GPS) coordinates to locate the
manor canals and structures while supplementary topo - and land use information from Google Earth
maps, Google terrain data and other relevant images have also been obtained as required. The
SRTM/GTOPO30 (USGS) global raster satellite DEM (Digital Elevation Model) data were downloaded
and used in identifying sub-/major catchments in the region. These maps and terrain data in
combination with identified land use data were used to distinguish and demarcate respective
catchment areas for the tank under consideration. In the present version of the analysis, a 5.0-m
interval contour map in the coast of upstream region, developed based on DEM data from GTOPO30
and modified with SRTM (Refined) arc 3.0 data has been used in initial catchment demarcation.
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Figure 2.5: The catchment areas of the Reservoirs/Tanks considered for the present EA
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Figure 2.6: The satellite view of the catchment areas of the Reservoirs/Tanks considered for the present EA
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Figure 2.7: Main Pimburaththewa Catchment
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h. Flooding
Past flooding records indicated that the project area was inundated with the flood received in
January 2013 but damages were not significant. The flood water level had receded within a short
period of time, hence no significant flood damage was recorded. All seven sluice gates of the Ulhitiya
Rathkinda reservoir have been opened both in 2013 and 2014. The water is being released to the
Mahaweli River. The Rathkinda-Hobariyawa and Mahiyangana-Dehiattakandiya roads were flooded.
Even the floodwaters have damaged the Ulhitiya Oya Bridge.
The Maduru Oya floodplain, when it was in the unregulated state before early 1980s, experienced
short duration flooding during the Maha season. For example, the cyclone of November 23/24, 1978
caused widespread flooding. Substantial flood control benefits have been derived from the flow
regulation of the Mahaweli River in the floodplain area, particularly in the reduction of the
magnitude and duration of persistent flooding during the Maha season. More intense flood peaks
have affected less, since the effects of an intense storm event than smaller watershed area
downstream from the dam has causes a larger peak flow per unit area than would have resulted
from the same storm over the entire catchment.
Therefore, no flood damages were recorded in the recent past, at least for last 30 years.
i. Noise and Vibration
Background noise levels in the area were found to be very low varying in the range of 45 – 58 dB (A)
during the site visit, indicating that no any artificial noise levels is generated in the project area. The
existing noise levels are attributed by the noise generated from the rattling of leaves of trees by the
wind and the occasional screech of birds passing and roosting in the area.
No significant vibration levels were perceived during the field visit indicating that vibration induced
activities were almost absent.
j. Air Quality
Occasional wind blows were observed during the site visit, which have been a common site in the
bund area. Such sporadic wind blowing has brought about airborne suspended particles, but, this
scenario was not significant enough to be reckoned as an issue. The canopy trees that have rooted
down in the vicinity of the bund have sheltered the bund area from escaping the airborne particles
hence, no air quality issues were found. Occasional vehicular movements were recorded along the
bund, which sometimes causes the airborne particles to be locally present. However, during the
windy periods, one has to be aware of airborne particles causing inconvenience to the pedestrians.
k. Water Quality
The water quality of the tank seems to be not degraded as relatively less anthropogenic activities
are found to be operating in the surrounding of the tank. It has been consistently observed that the
average pH is 8.4, which shows slight alkalinity in water (average: 5.5 meq/l), probably due to the
geological formations. Chlorophyll concentrations are moderate with an average value of 58.5 mg/l,
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which shows slight eutrophic conditions. Apart from the algal growth, slight turbidity issues were
seen during the site visit, particularly in the area of rip rap as the soil underneath was stirred up due
to wind induced currents striking the rip rap. This issue was very much localized and was not
considered to be an adverse issue for aquatic ecosystems.
2.3 BIOLOGICAL ENVIRONMENT WITH FLORA AND FAUNA
2.3.1 Existing Habitats and ecological significance
Pimburaththewa tank is located within the dry zone of the island in Polonnaruwa district. Natural
vegetation types in this area belongs to the ‘Dry and Arid Lowlands’ floristic region. The typical
natural climax vegetation types expected to be found in this zone are tropical dry-mixed evergreen
forests (Manilkara and mixed community) tropical thorn forest, damana and villu grasslands, flood
plain wetlands and riverine and gallery forests. However, these habitats are not found in the area
where the project interventions are planned. Agro-ecologically this area is classified as DL1c- low
country dry zone with undulating terrain and Reddish Brown Earth and Low Humic Gley as typical
soil types. The land use includes paddy lands, rain-fed upland crops, mixed home gardens,
scrublands, and natural forests. This tank is found in Mahaweli system B close to the Aralaganwila
town. Maduru oya National Park is the nearest protected area. Ecologically sensitive habitats such
as natural undisturbed forests or wetlands are not found where the proposed intervention will be
implimented. Both aquatic and terrestrial habitats are found in the project area. The aquatic habitats
are the tank and water stagnated habitats below the dam. Two main terrestrial habitats based on
the floristic composition are cultivated lands, and tank bund/ reservation. The tank reservations are
properly maintained without any encrochments. Seapage area of the downstream include severl
stagnated water pools with extensively growth green algae. Shallow areas of the tank has been
colonized by Japan jabara (Eichhornia crassipes). Large extents of paddy fields are located
downstream area away from the tank.
2.3.2 Flora
Tree species such as Milla (Vitex altissima), Ehela (Cassia fistula), Kohomba (Azadirachta indica) Kon
(Schleichera oleosa), Helamba (Mitragyna tubulosa), Ehatu (Ficus tinctoria), Rukattana (Alstonia
scholaris), Kumbuk (Terminalia arjuna), Nuga (Ficus benghalensis) Bo (Ficus religiosa), Ipil ipil
(Leucaena leucocephala), and Damba (Syzygium cumini) are found in the reservation of the dam.
The common herbs, shrubs and climbers found on the tank bund are Lantana (Lantana camara), Katu
pila (Flueggea leucopyrus), Iluk (Imperata cylindrica), Podisinnomaran (Eupatorium odoratum), Epala
(Urena lobata), Rata tana (Panicum maximum), Bevila (Urena lobata), Nidi kumba (Mimisa pudica),
Pani thora (Cenchrus echinatus), Wal Aba (Cleome viscosa), Kuwani (Cenchrus echinatus), Eraminiya
(Ziziphus oenoplia), Kala wel (Derris parviflora), Gas Karal Heba (Achyranthes aspera), Heen eraminiya
(Ziziphus oenoplia), Bowitiya (Osbeckia aspera), Monara Kudumbiya (Vernonia cinerea), Kappetiya
(Croton laccifer), Karamba (Carissa spinarum), Ranawara (Cassia auriculata), Bo kala wel (Derris
scandens), Maduru thala (Ocimum tenuiflorum), Wara (Calotropis gigantean), and Hulan Tala
(Ageratum conyzoides).
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Home gardens and residences located away from the tank include several species of trees such as
Amba (Mangifera indica), Kos (Artocarpus heterophyllus), Siyambala (Tamarindus indica), Tekka
(Tectona grandis), Coconut (Cocos nucifere), Halmilla (Berrya cordifolia) Kohomba (Azadirachta
indica), and Acacia (Acacia melanoxylon).
2.3.3 Invasive Species
Two species of invasive plants were observed from the tank and surrounding habitats include aquatic
plant, Japan jabara (Eichhornia crassipes) and terrestrial species Lantana ( )aLacLaLatLaLL ).
aLacLaLatLaLrL is curently spreads in tank bunk, tank reservation and surrounding habitats. Since
periodic removal of weeds from tank bund, distribution of aLacLaLa tLaLrL is controlled to some
extent. A few bushes of Lantana can be seen in fences around the cultivations and uncultivated lands.
An invasive aquatic species Japan Jabara (Eichhornia crassipes) can be seen as small patches in shallow
areas of the tank.
2.3.4 Fauna
Pimburaththawa spillway could be considered as an artificial habitat. The spillway is concrete lined
and reinforced with boulders and iron mesh. Therefore, the spill way is not a preferred wildlife
habitat. Shallow reservoir side near the spillway support a luxuriant growth of water hyacinth
(Eichhornia crassipes). This is a favorable habitat for some water birds such as Indian Pond Heron
(Ardeola grayii) and Little Egret (Egretta garzetta). Summary of the fauna recorded in the spillway
area is given in the Table 2.1.
Table 2.1: Summary of the fauna recorded in the rubble storage site and Pimburaththewa
spillway site
GROUP Species Endemic CR EN VU
DRAGONFLIES 3 - - - -
BUTTERFLIES 32 1 - - -
AMPHIBIANS 3 - - - -
REPTILES 6 - - - -
BIRDS 30 2 1 - -
MAMMALS 6 2 - 1 -
CR- Critically endangered ; EN- Endangered; VU-Vulnerable
List of fauna recorded in Pimburaththewa site is given in the Annex 4.
2.3.5 Rare, Threatened and Endemic Flora and Fauna
The habitats in the project area are degraded due to human influence. Therefore, plant and animal
communities found in natural undisturbed habitats are not represented in these areas. Only two
threatened species namely the Rock Pigeon (Columba livia – critically endangered) and Elephant
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(Elephas maximus – endangered) were recorded from the project site. Further, five endemic animal
species namely one butterfly species (Sri Lanka Lesser Albatross- Appias galena), two birds (Sri Lanka
Junglefowl - Gallus lafayetii and Sri Lanka Lesser Flameback -Dinopium sarodes), and two mammals
(toque monkey -Macaca sinica and Sri Lanka pigmy mouse deer- Moschiola meminna) were also
recorded.
2.3.6 Migratory Paths
There are evidences (dung piles, tree branch damages etc.) to prove that elephants frequent the
spillway area probably for drinking and bathing in the shallow reservoir area near the spillway.
Elephants may be moving to the area from the forests bordering the reservoir which is connected to
the Maduru Oya National Park (Figure 2.8). Although, the spillway proper is not a preferred elephant
habitat, the areas bordering the spillway would be providing the suitable cover for the elephants
visiting the reservoir.
Figure 2.8: Pimburaththawa spill
2.3.7 Proposed borrow area
In the past the site has been used for solid extraction and hence still carries some open patches
(Plate 2.3.2). Invasive shrub Lantana camera (gandapana) dominate the open area while a good
tree cover exists along the border of the site. The tree covered areas of the site is a quality bird
habitat as evidenced by presences of large number of birds in the area. Thirty species of birds have
been recorded from trees surrounding the site (Table 2.1). There are indirect evidences (tree &
branch damage, signs of antler rubbing, and fecal pellets etc.) to prove this tree cover is regularly
used by the large herbivores such as elephants and spotted deer which visit the spill area for drinking
purposes.
Elep
han
t mo
vem
en
ts
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Figure 2.9: Rubble storage site
2.4 SOCIOECONOMIC ENVIRONMENT
2.4.1 Local Administrative Units in the Project Area
The Pimburaththewa Dam is the reservoir located in Mahaweli System B. The Pimburaththewa
reservoir and it is related other features are located in Dimbulagala Divisional Secretariat of
Polonnaruwe District in North Central province. The irrigation Dam is administrated by Welikanda
Resident Project Manager's (RPM) office and Wijayabapura Block Managers’ (BM) office. The specific
details of the local administrative units related to the project are mentioned below:
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Table 2.2: Details of the local administrative units related to the project area
Part of the dam Province District Relevant RPM
Relevant BM Relevant DS Relevant GN Relevant villages
Tank and Tank catchment
North central
Polonnaruwa Walikanda Wijayabapura Dimbulagala 236, Pimburattawa East
238, Pimburattawa west
Pimburattawa
Command area North central
Polonnaruwa Walikanda Wijayabapura Dimbulagala 236, Pimburattawa East
238, Pimburattawa west
245, Aralaganwila west
246, Aralaganwila east
247, Rathmaltanna
248 track 5
254 Wijayabapura
255 Gomathiyaya
256, Madagama
257, Jayapura
Pimburattawa
Aralaganwila
Rathmaltanna
track 5
Wijayabapura
Gomathiyaya
Madagama
Jayapura
Deagama
Bamunakotuwa
Sudupalama
Chethiya pitiya
Madurutenna
Galthalawa
Farmers -do- -do- -do- -do- -do- -do- -do-
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2.4.2 Land Use in Different Areas of the Irrigation Schemes
Catchment Area
The catchment area of this reservoir has not been encroached and developed for any economic
activities. The catchment is in Maduru Oya reserved forest area. The extent of Catchment of this
reservoir including its water spread areas is about 1784 ha.
Downstream of the Dams
Downstream of the Dam has not been encroached by anybody for any economic or social activity.
Command Area
The total command area of the reservoir is 2724 ha with distribution among 63 Farmer organizations
(FOs). The cultivation activities of this command area are managed by 8 Unit Managers’ offices.
These 8 Unit Managers’ areas fall under 10 Grama Niladhari divisions for other civil administrative
purposes.
The entire command is cultivated with paddy in both Maha and Yala seasons (100% cropping
intensity).
2.4.3 Demographic Data Relevant to the Project Area
Table 2.3: Details of Project Relevant Population
Relevant GN Units No of FOs
No of families
Land owning families
Families not owning land
Pimburattawa East
8 63 410 360 50
Pimburattawa West
357 303 54
Aralaganwila East 430 270 160
Aralaganwila West
833 678 155
Rathmaltanna 413 250 153
track 5 288 216 72
Wijayabapura 589 310 279
Gomathiyaya 251 190 61
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Madagama 436 223 213
Jayapura 378 201 177
Total 1 63 4385 3011 1374
There are no human settlements in catchment areas or downstream areas of the Dam. The farmers
have not established any houses in the paddy land areas. All the farming families of the two
reservoirs are residing in settlement areas/hamlets (highlands) falling under Kadirapura Grama
Niladhari division.
2.4.4 Economic Activities of Project Related Population
The distribution of income generation activities among families in the project related 10 GN divisions
is given in Table below
Table 2.4: Distribution of income generation activities among families in project related villages
Economic Activity Percentage of Families
Farming 70
Government employment 15
Private sector employment 10
Others (fishery, small business & foreign employment) 5
Source: FO leaders, GNs
2.4.4.1 Yield and Income from Agriculture
Paddy farming is the main source of income of the project relevant families in Pimburaththawa
Irrigation scheme. According to the leaders of the farmer organizations and the officers of
Mahawanawala Block Office interviewed (Annex 5) yield of the farmers in the scheme are fairly
homogeneous. Therefore, the information related to one farmer on yield and income of an acre
cultivated with paddy is mentioned below as representative case of Pimburaththawa irrigation
scheme.
Yield – 2,420 kg per acre per season (110 Bushels x 22 kg)
Selling price and the gross income – 2,420 kg * Rs 36/- = Rs 87,120/-
Average expenditure – Rs. 46,600/-
Net income – Rs 40,520/- per season (Rs. 87,120 – Rs.46,600)
Further details of the calculation of cost benefit are shown in Annex 2.
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2.4.4.2 Cost Benefit Analysis of the Yield and Income from the entire irrigation scheme
The team further worked out the cost benefit of the entire Pimburaththewa irrigation scheme with
the experience of the leaders of farmer organizations and the Officers of Wijayabapura Block Office.
The details expressed by them are summarized below:
Table 2.5: Details Expressed by the Farmer Leaders/Block Officers
Yield Gross income Rs. Expenditure items Expenditure Rs.
Total land area = 6,810 acres
Yield of an acre = 2,420 Kg
Total Yield = 2,420 * 6,810= 16,480,200 kg
Rs. 593,287,200
(16,480,200 kg * Rs. 36/-)
Total land area 6,810 acres, expenditure of 1 acre per season Rs. 46,600/-,
Total expenditure of the entire scheme 317,346,000 (6,810 * 46,600)
Note:
Total gross income – Rs. 593,287,200/-
Total expenditure – Rs. 317,346,000 /-
Net income – Rs. 275,941,200/-
2.5 OTHER WATER USES
Three other (other than agriculture) direct and 1 indirect water uses and users of Bund top as access
are reported in Pimburaththewa irrigation scheme areas. The details of these water uses are
described below:
Fishing Activities
Fishing is a significant economic activity taking place in Pimburaththewa tank. About 105 persons
actively involved in catching fish in the tank. They have 105 boats used for fishing. The 105 fishermen
have formed an association called “Lihini Inland fishery cooperative “. About 20 persons are full time
fishermen and they solely depend on this activity for their livelihoods. They earn about Rs. 1,000 to
1,200 /day and about 20 days /month they go for fishing in the tank. The other persons perform
agriculture activities in the irrigation scheme as part time income generation activity. They too earn
about Rs. 1,000 but they spend only about 10 days for fishing during agriculture season and they
have freedom to go for fishing for about 20 days/month during off agriculture season. The 105
fishermen use 3 locations as boat landing sites. The 3 boat landing sites include:
Mulgalpedesa- 70 boats
Alawakumbura – 30 boats
Talawe- 5 boats
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Drinking water use
A community water supply scheme has been recently established but house connections have not
yet been given. It has been planned to provide water to 500 families.
Bathing and Washing
About 25 to 30 families use the tank for bathing and washing. Others in the pimburattawe area use
irrigation canals for this purpose. When the irrigation canals are closed (during August and
September) the communities in the area use the tank for bathing and washing.
Small Industries
About 26 rice mills are available in the project area and their performance is completely depended
on the agriculture (1 large scale mill and 25 minor scale mills). Another about 20 mills use for rice
processing and grain milling are also available.
Use the bund top as access road
The bund top is not used as a permanent road. Some families, about 15 to 20 use the bund top as
temporary/by pass access to reach Chenas (Chenas in Sadunpura, Lihiniyagama and Weheragala
areas).
2.6 CURRENT ENVIRONMENTAL ISSUES OF THE PROJECT AREA
This subsection discusses the other issues pertaining to the area other than those to be caused by
the project activities. The project activities may trigger some of them, resulting in adverse impacts.
Hence it is of paramount to mention such issues in brief in order to lessen such impacts, if envisaged.
2.6.1 Physical Issues
The runoff from the agricultural fields enters the reservoir. Villagers may use this nutrient loaded
water (including heavy metals) for drinking and bathing purposes. Excessive nutrients entering the
reservoir may lead to eutrophication and appearance of algal blooms.
2.6.2 Ecological Issues
There are no significant ecological issues identified in the proposed project area. Some invasive plant
species such as Lantana, Japan Jabara and guinea grass are found in the natural habitats, tank and
tank bund/ toe areas. The periodic cutting of Lantana and guinea grass controls their colonization in
the terrestrial habitats. Presence of invasive species prevents the establishment of indigenous herbs,
shrub and some tree species in these habitats. Human elephant complicit is not a major issue in the
Pimbureththewa tank and surrounding habitats. Herds of elephants frequently visit the spillway and
surrounding area and occasionally raid the crops and damage the properties of the people.
2.6.3 Socioeconomic Issues
One of the most serious problems faced by the communities, especially farmers is the frequent
entering of wild elephants to the area. These elephants come to the residential and agriculture areas
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from the Maduru Oya reserved forest. The crops in the areas such as Pimburaththawe East,
Pimburaththawe West, Aluth Oya, Aralaganwila East and Aralaganwila West are frequently
destroyed by wild elephants.
Lack of land resources (both irrigated and high lands) is another serious and also long term problem
related to the livelihood of the people. A family has been allocated with 1 ha of irrigated land and
0.25ha of highland. These extents are not at all adequate to divide among children (average family
size is 5 to 6). A plot of land belongs to a family can be divided in to two parts but if there are more
than one child it would be a serious problem for land distribution among all the children.
Lack of opportunities for non-agriculture employments and also fluctuation of paddy selling prices
are also viewed as problems in the area.
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3. PROPOSED INTERVENTIONS
3.1 PROPOSED ENGINEERING INTERVENTIONS
A list of current structural and operational issues of the dam was given to the consultants for
verification during the reconnaissance field visit. The consultants verified the issues in the provided
list to them and also included other issues not yet included in the original list. The issues verified by
the consultants and also the new issues identified with the assistance of MASL officers of the Dam
are summarized in Table 3.1.
Table 0.1: Current issues at Pimburaththewa Tank
Issues identified as per the ToR
Issue Intervention Construction methodology
1. Inadequate
capacity of
the spillway
canal
2. Erosion in
spillway side
ways
3. Deficiencies
in spillway
(Figures 3.1 – 3.8)
Removal of existing gabion structure
Excavation of spillway approach channel
Repair to the spillway side walls
Repair of spillway bed and stilling basin
Removal of the existing concrete road
Excavations for spill way construction
Construction of embankments to support the bridge deck
Construction of the bridge over the spillway
Construction of the road on the bridge and on either sides of the bridge
Painting of the bridge
Slope protection
Site Clearing
Clearing and uprooting of secondary growth jungle including
removal of all trees
Demolishing, removing of existing concrete road and cut off
wall
Removing of gabion boxes
Stripping top soil, haul 1 km
Earth works
Common excavation for structures, approach canal and
disposal of waste material or used for fill
Common excavation for foundation and use for backfilling or
disposal of waste material
Construction of coffer dam and removing after construction
Filling of bund FSL to bund top
Borrow earth from borrow areas, cut 0-10 ft lift up to 10 ft,
any haul
Placing and compacting earth in embankment & in trench
including watering
Rock excavation
Soft rock excavation and spoil to waste, haul 1 km
Rock excavation and spoil to waste/ Quarry product, haul 1
km
Slope protection
Furnishing, Planting and watering turf, haul 1.6 km including
loading
Furnishing and placing gravel bedding, haul 1.6 km including
loading
Furnishing and placing 450 mm rip-rap, haul 1.6 km including
loading
Concreting
Grade 15 concrete (1:3:6 (40 mm) for screed concrete in
structures excluding form work
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Grade15 concrete (1:3:6 (40 mm) for screed concrete in
structures including formwork
Grade 20 concrete (1:2:4 (20 mm) in structures including
formwork
Grade 20 concrete (1:2:4 (20 mm) in structures including
formwork
Grade 25 concrete (1:11/2:3 (20 mm) in structures including
formwork
Grade 30 concrete in structures including formwork
Grade 40 concrete in structures including formwork
Reinforcement
Furnishing, cutting, bending and placing toe steel
reinforcement
Furnishing, cutting, bending and placing mild steel
reinforcement
Precast concrete Units
Furnishing and install bridge beams 32’×2.59t & transport
200 miles, installation crane travel 200 miles
Furnish and install kerb slab 3’×1.08 cwt, transport 200 miles,
installation crane travel 200 miles
Furnish and install uprights for hand rails of 3’3”×1.09cwt,
transport 200 miles, installation crane travel 200 miles
Furnish and install hand rails of 3” dia×7’81/2”×0.94cwt,
transport 200 miles, installation crane travel 200 miles.
PC concrete coupling pairs for hand rails of bridge supplying
and fixing
Water Stop
Supplying and laying of 225 mm width center bulb rubber
water stop at construction joints
Miscellaneous Works
Supplying and laying approved hard rubber bearing pads 75
mm × 12 mm over capping beams
Supplying and fixing M.S. Angle Iron and hard rubber
expansion joints as per drawing.
Supplying and fixing 110 mm dia PVC extended pipe type 250
through deck rain water outlets as per drawing
Supplying and placing asphalt wearing surface at bridge deck
and approaches
Painting with two coats of enamel paint on kerbs, uprights,
hand rails and parapet walls of bridge
Supplying and fixing 25 mm dia 400 mm long stainless steel
dowel bars.
Bituminous sealing material supplied and laid under beam
ends to prevent Grout leak on to.
230 mm dia. polythene displacers supplied and filled with
saw dust or similar light material in deck.
Forming weep holes using PVC pipes of int. diameter not less
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than 100 mm, complete with drip ledge and surround finish
smooth
Slope protection with 9” thick pitching in 6’’×9” rubble in
1:5ct. mt. on rubble pitching faces
4. Damage in
the rip rap in
some areas
(Figure 3.9 and 3.10)
Placing rip rap
Removing of existing riprap and pilling of riprap rubble
manually
Transport of riprap rubble (about 16 km) to the site and
piling
Packing of removed or additional new ruble to a thickness of
375 mm manually
Placing and packing riprap to a thickness of 450 mm
Issues identified during the initial site visit
Issue Intervention Construction methodology
5. Seepage
areas along
the
downstream
toes (Figure
3.11 & 3.12)
Construction of Toe road and toe drain
Construction of V-notches
Weeding along the tank bund
Removing of embankment unsuitable material, including
stripping of top soil on dam slope and dam toe, cut and lift
up to 1.5 m, haul 30 m
Furnishing and laying of a geo textile cloth in toe drain
Furnishing, placing, spreading, watering and compaction of
20-37.5 mm well graded aggregate layer as the bottom layer
of toe filter
Furnishing, placing and packing 150-300 mm of well graded
rubble in toe drain
Furnishing, placing, spreading, watering and compaction of
gravel as fill material for access road by machinery
Full turfing to newly filled earth in canal bund slopes
Furnishing and installation of V-Notch and Culvert across
the road in toe filter
Note : Apart from the development interventions initially proposed and also observed in the
consultants' field visits the farmer leaders met during the detailed filed studies mentioned about
their concerns to get the tank bed desilted. The tank bed is silted up seriously (about 5 feet depth
with sediments).
Photographic evidence for the identified issues in Table 3.2 is given in figures below.
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Table 3.2: Photographic evidence for the identified issues
Figure 3.1: Damages to the Spillway Figure 3.2: Erosion in spillway side ways
Figure 3.3: Damaged Spillway
Figure 3.4. Spill tail areas collapsed completely
Figure 3.5: Damaged spillway Figure 3.6: Damaged Spillway
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Figure 3.7: Completely eroded parts of the Spillway
Figure 3.8: Completely eroded parts of the Spillway
Figure 3.9: Removal of shrubs needed on the rip rap rip rap in some areas
Figure 3.10: Riprap damaged at some places
Figure 3.11: Seepages at D/S areas Figure 3.12: Seepage at D/S areas
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3.1.1 Resource and Material Requirements for Proposed Interventions of Pimburaththewa Reservoir
Table 3.3: Material Requirements for the repairs at the spillway and construction of the bridge across the spillway
Item of work
Clearing
(m2/Ha)
Excavation/ Removal Earth/Sand/Rubble (m3)
Material Need
Nos. Gravel/Earth/ Sand (m3)
Rubble/ Aggregate (m3)
Concrete (m3)
Linear meters (m)
Square meters (m2)
Site Clearing
Clearing and uprooting of secondary growth jungle including removal of all trees
0.53
Ha
Demolishing, removing of existing concrete road and cut off wall
468.5 m3
Removing of gabion boxes 480 m3
Stripping top soil, haul 1 km 340 m3
Earth works
Excavation for structures, approach canal and disposal of waste material or used for fill
38,043.9 m3
Common excavation for foundation and use for backfilling or disposal of waste material
2,971.8 m3
Construction of coffer dam and removing after construction
01
Nos.
Filling of bund FSL to bund top
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Item of work
Clearing
(m2/Ha)
Excavation/ Removal Earth/Sand/Rubble (m3)
Material Need
Nos. Gravel/Earth/ Sand (m3)
Rubble/ Aggregate (m3)
Concrete (m3)
Linear meters (m)
Square meters (m2)
Borrow earth from borrow areas, cut 0-10 ft lift up to 10 ft, any haul & Placing and compacting earth including watering
7,915.5 m3
Rock excavation
Soft rock excavation & spoil to waste, haul 1 km 50 m3
Rock excavation and spoil to waste/Quarry product, haul 1 km
90 m3
Slope protection
Furnishing, planting & watering turf, haul 1 km 2,099 m2
Furnishing & placing gravel bedding, haul 1 km 120.8 m3
Furnishing & placing 450 mm rip-rap, haul 1 km
310.5
m3
Concreting
Grade 15 concrete (1:3:6 (40 mm) for screed concrete in structures
289.9
m3
Grade15 concrete (1:3:6 (40 mm) for screed concrete in structures
1,175
m3
Grade 20 concrete (1:2:4 (20 mm)
2,454
m3
Grade 20 concrete (1:2:4 (20 mm)
296
m3
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Item of work
Clearing
(m2/Ha)
Excavation/ Removal Earth/Sand/Rubble (m3)
Material Need
Nos. Gravel/Earth/ Sand (m3)
Rubble/ Aggregate (m3)
Concrete (m3)
Linear meters (m)
Square meters (m2)
Grade 25 concrete (1:1½:3 (20 mm)
950
m3
Grade 30 concrete in structures
124
m3
Grade 40 concrete in structures
261
m3
Reinforcement
Furnishing, cutting, bending and placing toe steel reinforcement
222 t
Furnishing, cutting, bending and placing mild steel reinforcement
6 t
Precast concrete Units
Furnishing and install bridge beams 32’×2.59t & transport 200 miles, installation crane travel 200 miles
168
Nos.
Furnish and install kerb slab 3’×1.08cwt, transport 200 miles, installation crane travel 200 miles
292
Nos.
Furnish and install uprights for hand rails of 3’3”×1.09cwt, transport 200 miles, installation crane travel 200 miles
236
Nos.
Furnish and install hand rails of 3” dia×7’81/2”×.94cwt, transport 200miles, installation crane travel 200 miles.
342
Nos.
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Item of work
Clearing
(m2/Ha)
Excavation/ Removal Earth/Sand/Rubble (m3)
Material Need
Nos. Gravel/Earth/ Sand (m3)
Rubble/ Aggregate (m3)
Concrete (m3)
Linear meters (m)
Square meters (m2)
PC concrete coupling pairs for hand rails of bridge supplying and fixing
348
Nos.
Water Stop
Supplying and laying of 225 mm width center bulb rubber water stop at construction joints
434 m
Miscellaneous Works
Supplying and laying hard rubber bearing pads 75 mm × 12 mm over capping beams
97.5 m
Supplying and fixing M.S. Angle Iron and hard rubber expansion joints
97.5 m
Supplying and fixing 110 mm dia PVC extended pipe type 250 through deck rain water outlets
56 m
Supplying and placing asphalt wearing surface at bridge deck and approaches
61
Mt
Painting with two coats of enamel paint on kerbs, uprights, hand rails and parapet walls of bridge
190 m2
Supplying and fixing 25 mm dia 400 mm long stainless steel dowel bars.
154
Nos.
Bituminous sealing material supplied and laid under beam ends to prevent Grout leak on to.
182 m
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Item of work
Clearing
(m2/Ha)
Excavation/ Removal Earth/Sand/Rubble (m3)
Material Need
Nos. Gravel/Earth/ Sand (m3)
Rubble/ Aggregate (m3)
Concrete (m3)
Linear meters (m)
Square meters (m2)
230 mm dia. Polythene displacers supplied and filled with saw dust or similar light material in deck.
1,232 m
Forming weep holes using PVC pipes of int. diameter not less than 100 mm, complete with drip ledge and surround finish smooth
42 m
Slope protection with 9” thick pitching in 6’’×9” rubble in 1:5ct. mt. on rubble pitching faces
1,170 m2
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3.2 PROPOSED BORROWING ACTIVITIES AND IDENTIFIED BORROW SITES
3.2.1 Turfing Materials
The turfing materials are required to prevent the soil erosion in slopes during the rainy season. The
grasses suitable for turfing are available in tank beds and in open grounds close to the tanks.
3.2.2 Earth
A site located near southern end of the pimburaththawa dam spill has been selected as a borrow
area to extract soil for the construction work of Pimbureththewa dam site.
3.2.3 Metal
The metal would be obtained from a private metal quarry in Siripura area.
3.2.4 Sand
Sand mining of Mahaweli river is carried out by the GSMB at Manampitiya. Sand could be purchased
at Manamptiya or if another location is selected a permit for extracting sand from the river would
be required from the Geological Survey and Mines Bureau (GSMB).
3.2.5 Gravel
A site located at Devagama has been selected as borrow area to extract soil and gravel for the
construction work of Pimbureththewa dam site.
The location for the above identified burrow and quarry sites are given in Annex 3.
3.3 PROPOSED INTERVENTIONS THAT COULD AFFECT NEIGHBORING COMMUNITIES
The design engineering team of Dam safety project assume that proposed development
interventions to repair the rip rap will be implemented during water low period of the tank ( just
after Yala season harvesting ). If the contractor cannot complete the proposed sensitive
development interventions within the short dry sell there may be need to keep the tank with low
water levels or postpone the sensitive construction work to the next season where tank would
experience low water levels. If water level is lowered there will be disturbances to the cultivation
planning in the irrigation scheme. Rehabilitation of spillway is the most essential need under the
proposed dam safety development interventions. The engineers of the project assume that
rehabilitation of spillway can be completed without lowering of the tank water levels. There can be
some temporary disturbances to the local communities who use to access their villages/Chena
through an informal road falling across the existing spillway.
Almost all the interventions will affect the neighboring communities for a certain extent; however,
they are not significant. Following interventions that have been proposed can be listed as
interventions that could affect neighboring communities:
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Material transport, stockpiling especially for graveling the bund road, rip rap construction,
correcting the slopes of the bund etc.
Constructing the rip rap, providing clay cutoff wall, etc. will obstruct the movements along
the bund
Providing toe filters, toe drain and the toe road along the toe area of the dam
Rehabilitating the bund (including construction of the rip rap) will prevent access to the tank
3.4 PROPOSED INTERVENTIONS THAT COULD AFFECT THE NATURAL HABITATS
The natural habitats found in the proposed project area and the identified borrow site are highly
degraded. The natural undisturbed habitats or vegetation formations are not found in the project
site or in the borrow site. The existing degraded habitats do not contain critical elements of
biodiversity such as endemic or threatened species confined to the dry zone of Sri Lanka. The plant
species found in these habitats mainly represented by the pioneer/ secondary species, exotic weeds
and invasive species. Threatened and endemic species do not encounter in these degraded habitats.
The proposed project interventions such as pilling of riprap rubble, packing of removed or additional
new ruble, do not make major disturbances to the existing habitats. Removal of trees is minimal for
any of the activities. Uprooting of herbs, shrubs and climbers in the rip rap area should be carried
out before repairing the rip rap. The clearing of herbs and shrubs will have temporary impacts on
some faunal species, e.g. butterflies and birds, since they depend on nectar of flowers and fruits of
these species. However, individuals of these plant species are found in the nearby habitats and
therefore the impacts would be negligible.
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4. PROJECT INDUCED IMPACTS
4.1 IDENTIFICATION OF PROJECT INDUCED IMPACTS
Note: The anticipated impacts described under this section are mainly for the construction phase only.
However, any impacts that are induced during operational stages (if any) are also presented where
applicable. The impacts are confined to negative impacts, as the positive impacts as a result of
improved dam safety and improved operational capacities of Head works are obvious and perceived.
Impacts were classified into three categories:
No: Environmental effects are perceived to have been no change at all.
Low: Environmental effects are not detectable or are so minor that they will neither destabilize nor
noticeably alter any important attribute of the resource.
Moderate: Environmental effects are sufficient to noticeably alter important attributes of the
resource, but not to destabilize them.
High: Environmental effects are clearly noticeable and are sufficient to destabilize the resource.
Table 4.1 depicts the possible impacts together with their significance on each intervention
proposed.
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Table 4.1: Possible impacts due to the proposed interventions and their significance
Issues identified as per the ToR
Issue Intervention Anticipated Impacts Significance
1. Inadequate
capacity of the
spillway canal
2. Erosion in
spillway side
ways
3. Deficiencies in
spillway
Removal of existing gabion structures
Excavation of spillway approach channel
Repair to the spillway side walls
Repair of spillway bed and stilling basin
Excavations for spillway construction
Removal of the existing concrete road
Construction of embankments to support the bridge deck
Construction of the bridge over the spillway
Construction of the road over the bridge and on either side of the bridge
Painting of the bridge
Slope protection
Impact on ecological environment:
Adverse Impact of the nearby habitats in spillway area will occur during the
construction phase. Removal and uprooting of trees and secondary growth
vegetation is essential for the proposed repair work to the spillway. Majority
of trees trees in spilway area ara planted trees belongs to exotic species
Acacia (Acacia melanoxylon). Since these trees have been used by the
avifaunal species this will create habitat loss for water birds roosting in these
these trees. Also negative impacts in borrow sites due to the removal of soil/
gravel would be expected. Excavated pits need to be filled to prevent
accidental damage to the wild animals, collecting rain water, and creating a
habitat for mosquito breeding during the rainy season.
Low Moderate
Impact on social environment:
This will be fairly significant and time consuming construction activity in this
dam. If it gets delays there can be some implications to fill the tank up to its
FSL level. Some community members’ access their villages/chenas through
an informal road across the spill way and there can be some disturbances to
these community members during construction period.
Moderate
Impacts on physical environment:
Removal and disposal of debris and excavated material
This activity involves the clearing of about 0.53 Ha of land and demolition of
the existing concrete road (469 m3) and stripping of top soil (340 m3). The
existing gabion boxes will be removed (480 m3), which will be part of the
Moderate
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construction material (this will partially satisfy the need of requirement of
rubble). Part of the existing riprap will be completely removed and the
surface has to be prepared for subsequent re-laying of the riprap. The
surface preparation will produce significant amounts of soil material which
need disposal.
Increasing the possibilities of erosion
The proposed construction need significant amounts of soil excavation
(38,043 m3 of excavation for structures and 2.971 m3 for foundations)
before construction of the spillway, spillway bed and the stilling bed.
Embankment construction and road construction involved in the bridge
construction need stripping of top soil, excavation of embankments, filling
and compaction. Such earth work will lead to soil erosion, slope erosion and
erosion of the road surfaces.
Raw water quality of surface water bodies
Raw water quality of surface water bodies can be affected due to soil
erosion. Soil particles that enter nearby water bodies, such as the tank and
canals etc., can result in temporary turbidity problems. However, the
duration of this exposure is short in duration and hence adverse impacts
anticipated would be not be significant.
Hindrance to vehicular movements, damage to the crest road surface
due to movement of heavy vehicles, temporary storage of earth along
the crest road and elsewhere
The earthwork involved in the construction work is large (41,000 m3).
Borrow material once brought to the site (7,915 m3) has to be unloaded and
stockpiled for subsequent use. This might block the existing run on and off
paths which may create erosion problems elsewhere.
Material transport (7,915 m3 of earth; approx. 5,000 m3 of concrete) may
Moderate
Moderate
Moderate
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result in congestion of local roads. There are dwelling units along haulage
routes and elevated levels of traffic matter can become a minor temporary
adverse impact during the construction period. Movement of heavy vehicles
will damage the crest road and access roads in the vicinity.
Noise and vibration
Large amounts of earth work (more than 41,000 m3 of earth excavation,
demolition of the existing road surface (468 m3), stripping of the top soil (340
m3) and most of the other activities will generate noise. Compacting large
areas and large amounts of concrete will generate significant amounts of
noise. Much of the proposed work will be carried out using machinery.
However, small machinery will be used for excavating and rubble and earth
transport. Noise and vibration is expected to be significantly high due to the
large-scale nature of construction.
Dust generation
Large amounts of earth work (more than 41,000 m3 of earth excavation,
demolition of the existing road surface (468 m3), stripping of the top soil (340
m3) and most of the other activities would produce airborne dust, which are
temporary and limited to short durations and will be restricted to a small
area. Therefore, air pollution due to the proposed work can be considered
not significant.
Pollution of Soil and Water via Fuel and Lubricants
The earthwork, large amounts of concrete work, and erection of the bridge
need a large fleet of heavy vehicles and heavy machinery. Activities such as
operation of construction vehicles, parking areas, fuel/lubricants spills
storage sites, machinery and equipment maintenance and refueling will
generate pollutants that have the potential to pollute soil and water.
Moderate
Moderate
Low
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Construction and removal of coffer dams
Transport of sheet piles, driving and removing of the sheet piles cause
numerous impacts. Noise and dust can result from transportation activities.
Noise and vibration due to pile driving and removing can cause disturbance
to neighboring community and the wildlife.
Sheet piles should be able to cutoff water movements across the coffer dam
for facilitating the construction activities.
(It is assumed that construction of the coffer dam would be done only after
a thorough hydrological and geological study. This should aim at prevention
accidental damage of the coffer dam structure due to predictable water
level fluctuations and the bottom geology would be capable enough to
support the sheet piles in withstanding hydraulic pressures.)
Health and sanitation of worker’s camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Management of waste (other than construction and excavated material)
and wastewater
Significant quantities of construction waste (e.g., during stripping of top soil)
are expected. In contrast, food items even in small quantities may attract
stray animals. However, the overall impact is very low.
Safety of workers at work
The earthwork involved in the construction work is large (41,000 m3).
Borrow material once brought to the site (7,915 m3) has to be unloaded and
stockpiled for subsequent use. The prestressed concrete sections have to be
Moderate
Low - moderate
Low
Moderate
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unloaded, and subsequently handled carefully to erect the bridge. These
activities pose a severe hazard and potential to cause physical injury to
workers during moving heavy loads downhill/uphill.
4. Damage in
the rip rap
in some
areas
Placing rip rap
Impacts on ecological environment:
Removal of existing vegetation in the rip rap, mainly herbs and shrubs will have some impact on butterflies and birds. However the impact will be low due to availability of similar habitats in surrounding area.
Low
Impacts on social environment:
If rip rap rehabilitation cannot be completed within the water low period in
the tank there may be need to lowering the water level or to postpone the
work to the next water low period of the tank
Low
Impacts on physical environment:
Increasing the possibilities of erosion of the U/S slopes
Exposed areas of the bund are susceptible to erosion.
Hindrance to surface runoff, hindrance to vehicular movements during
temporary storage of material along the crest road and elsewhere
Borrow material once brought to the site has to be unloaded and stockpiled
for subsequent use. This might block the existing run on and off paths which
may create erosion problems elsewhere.
The quantity to be handled seems to be large hence the impact may be
relatively significant (exact quantity to be determined)
Raw water quality of surface water bodies
Runoff through material borrow areas and unloading sites could lead to
wash off of soil particles to nearby water bodies such as canals, tanks
streams etc. resulting in temporary turbidity problems. However, the
Low
Low
Low
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quantity to be handled seems to be very low, hence adverse impacts
anticipated would be insignificant.
Hindrance to vehicular movements, damage to the crest road surface
due to temporary storage of rubble among the crest road and elsewhere
Material transport may result in air pollution through giving rise to elevated
levels of airborne dust. There are dwelling units along haulage routes and
elevated levels of airborne particulate matter can become a minor
temporary adverse impact during the construction period.
Health and sanitation of worker’s camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Management of waste (other than construction and excavated material)
and wastewater
No significant quantities of construction waste are expected. In contrast,
food items even in small quantities may attract stray animals. However, the
overall impact is very low.
Generation of noise, vibration and dust affecting the social and biological
environment
Noise and vibration can occur during compaction of the aggregate layer and
related activities. Activities that would produce airborne dust are temporary
and limited to short durations and will be restricted to a small area.
Low
Low
Low
Low
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Pollution of Soil and Water via Fuel and Lubricants
Activities such as operation of construction vehicles, parking areas, fuel/lubricants spills storage sites, machinery and equipment maintenance and refueling will generate pollutants that have the potential to pollute soil and water.
Safety of workers at work
Placing the rubble for the riprap will be done manually. Placing and moving
rubble from the bund crest towards the bund slopes involve extensive
amount of manual labour work. These activities pose a severe hazard and
potential to cause physical injury to workers during moving heavy loads
downhill/uphill.
Low
Moderate
Issues identified during the initial site visit
Issue Intervention Anticipated Impacts Significance
5. Seepage areas
along the
downstream
toes
Construction of Toe road and toe drain
Construction of V-notches
Impacts on ecological environment:
Removal of existing vegetation in the toe area, herbs, shrubs and few trees. The impact will be low due to availability of similar habitats in downstream area of the tank.
Low
Impacts on social environment:
No impacts are expected because there is adequate land area that can be used to establish the toe road and other infrastructure facilities required in the downstream of the Dam
Low
Impacts on physical environment:
Need to dispose debris and excavated material away from the site
Construction of the toe filter and drain include removing the existing toe
drain, excavation and removal of unsuitable soil material, bed formation
and stripping of soil. Further, construction of the toe road also involves
stripping of top soil and exaction of soil. These are significant amount that
Moderate
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has to be disposed properly (quantities of these material have to be
determined after designs are completed).
Increasing the possibilities of erosion of the toe areas in the D/S
Construction of the toe drain, filter and the tow road involve stripping of top
soil and loose rubble in the filter. Such exposed areas of the bund toe area
are susceptible to erosion.
Hindrance to surface runoff
Construction of the toe filter and drain include removing the existing toe
drain, excavation and removal of unsuitable soil material, bed formation
and stripping of soil. Construction of the toe road also involves stripping of
top soil and exaction of soil. These will pile up at the construction site, which
will hinder surface drainage.
Construction of the toe filter and drain need sand, graded gravel, and
rubble. Toe road construction needs earth and gravel. These materials once
brought to the site have to be unloaded and stockpiled for subsequent use.
This might block the existing run on and off paths which may create erosion
problems elsewhere (quantities of this material have to be determined after
designs are completed).
The quantity to be handled seems to be fairly large hence the impact may
be moderately significant.
Raw water quality of surface water bodies
Runoff through material borrow areas and unloading sites could lead to
wash off of soil particles to nearby water bodies such as canals, tanks
streams etc. resulting in temporary turbidity problems. However, the
quantity to be handled seems to be very low, hence adverse impacts
anticipated would be insignificant.
Low
Low
Low
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Increase in vehicular traffic during transport of construction materials
Material transport may result in air pollution through giving rise to elevated
levels of airborne dust. There are dwelling units along haulage routes and
elevated levels of airborne particulate matter can become a minor
temporary adverse impact during the construction period.
Health and sanitation of workers’ camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Management of waste (other than construction and excavated
material) and wastewater
No significant quantities of construction waste (other than the excavated
material as described above) are expected. In contrast, food items even in
small quantities may attract stray animals. However, the overall impact is
very low.
Generation of noise, vibration and dust affecting the social and
biological environment
Noise and vibration can occur during compaction of the gavel bedding for
the toe road, loading berm, drains etc. and compacting the aggregate layers.
Activities that would produce airborne dust are temporary and limited to
short durations and will be restricted to a small area.
Pollution of Soil and Water via Fuel and Lubricants
Activities such as operation of construction vehicles, parking areas, fuel/lubricants spills storage sites, machinery and equipment maintenance
Moderate
Low
Low
Low
Low
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and refueling will generate pollutants that have the potential to pollute soil and water.
Safety of workers at work
Placing the rubble for the toe filter will be done manually. Placing and
moving rubble towards the bund slopes involve extensive amount of
manual labour work. These activities pose a severe hazard and potential to
cause physical injury to workers during moving heavy loads downhill/uphill.
Installation of the V-notches and three piezometers will have very minor
environmental impacts.
Low
Low
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4.2 QUANTIFICATION OF THEIR SIGNIFICANCE
Determining the significance of impacts places value on impact magnitude. It relates to the
importance society places on the resources affected, the importance of the impact to system
stability and sustainability.
Quantification of impact magnitude in this study has been objective-based backed by prior
experience of the team of consultants, rather than applying numerical and/or scientific principles
and theories. Once the impact magnitude was determined based on the proposed construction
methodology for each intervention, each expert has decided on the significance of the impacts based
on their area of expertise. Significant impacts will be the focus of mitigation measures and
subsequent monitoring, as outlined in the report.
Factors that have been considered in determining of impact significance include (but are not limited
to):
Area of Influence: Impact significance is often directly related to the size of the area affected.
Amount of Resource Usage: The greater the amount of resource usage, the more significant
the impact.
Status of Resources: Impacts due to usage of limited resources are usually considered more
significant than impacts to common or abundant resources.
Persistence of Impacts: Permanent or long-term changes are usually more significant than
temporary ones. The ability of the resource to recover, after the activities are complete, is
related to this effect.
Sensitivity of Resources: Impacts to sensitive resources are usually more significant than
impacts to those that are relatively resilient to impacts.
Regulatory Status: Impacts to resources that are protected (e.g., endangered species, air
quality, cultural resources, water quality) typically are considered more significant than
impacts to those without regulatory status.
Societal Value: Some resources have societal value, such as archaeological, cultural and
sacred sites, traditional practices, and recreational areas.
Hence, quantification of impacts was done based on the above-mentioned criteria only for the
impacts that are perceived to be either moderate or high.
There will be no negative social impacts if the contractors could complete the spillway rehabilitation
and rip rap rehabilitation within the planned period in which water levels of the tank is low.
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5. ENVIRONMENTAL MANAGEMENT PLAN
5.1 GENERAL OVERVIEW
The purpose of this Environmental Management Plan (EMP) is to manage the anticipated on and off-
site environmental impacts due to the interventions proposed to remedy identified issues of the
dam. Therefore, it is necessary to first scan the issues that have arisen to compromise the safety and
operational efficiency of the Pimburaththewa Reservoir. The following issues and their mitigation
measures were identified and presented in the EMP.
5.2 IDENTIFICATION OF IMPACTS AND THEIR MITIGATIONS
This section summarizes the mitigation measures to be implemented for the identified
environmental impacts that can potentially occur predominantly during the construction phase of
the proposed interventions (Table 5.1). This table indicates only the ones that need mitigation
measures and those that are not listed here would not require any mitigation measures.
The DSWRPP has a strong focus on proper environmental management. Therefore, the focus of
environmental management of the project has not been limited to managing those impacts arising
due to the proposed interventions but also to improve adverse environmental conditions that will
prevail during rehabilitation work by applying proper mitigation strategies.
As a part of the EMP, appropriate institutional arrangements to implement the proposed measures
and clearances and/or approvals needed by the project prior to its implementation have been
proposed after discussing with the responsible authorities (Table 5.2). For each proposed
intervention, the EMP defines the technical content, roles and responsibilities of stakeholders,
schedule of implementation and methods of monitoring etc.
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Table 5.1: Proposed mitigatory measures for the identified impacts
Issues identified as per the ToR
Issue
Inadequate capacity of the spillway canal
Erosion in spillway side ways
Deficiencies in spillway
Intervention
Removal of existing gabion structures
Excavation of spillway approach channel
Repair to the spillway side walls
Repair of spillway bed and stilling basin
Excavations for spillway construction
Removal of the existing concrete road
Construction of embankments to support the bridge deck
Construction of the bridge over the spillway
Construction of the road over the bridge and on either side of the bridge
Painting of the bridge
Slope protection
Anticipated Impacts Mitigation measure
Impact on ecological environment:
Adverse impacts on the habitats in borrow sites due to the removal of soil/ gravel. Excavated pits would be filled with rain water, creating a habitat for mosquito breeding during the rainy season. Also these pits act as a dangerous location for wild animals such as wild elephants and create accidental damage to them.
Construction materials should only obtain from licence quarries and material extraction sites. Rehabilitation/ replanting of the borrow areas with indigenous plant species after the extraction is completed. The pits should be filled and the layer of top soil is required for the growth and establishment of plants. Natural regeneration of plants mainly grasses, herbs, shrubs are expected soon after the excavation is completed.
Impact on social environment:
This will be fairly significant and time consuming construction activity in
Contractors must be get in to strict agreement to complete the work within the planned time period. The need of this work should be better convinced to the farming community through farmer leaders attended at the Block meetings, The PMU of Dam
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this dam. If it gets delays there can be some implications to fill the tank up
it its FSL level. Some community members access their villages through an
informal road across the spill way and there can be some disturbances to
these community members during construction period.
safety project and also the PMC of the irrigation scheme should closely monitor the process of spillway construction work.
Impacts on physical environment:
Removal and disposal of debris and excavated material
This activity involves the clearing of about 0.53 Ha of land and demolition
of the existing concrete road (469 m3) and stripping of top soil (340 m3).
The existing gabion boxes will be removed (480 m3), which will be part of
the construction material (this will partially satisfy the need of requirement
of rubble). Part of the existing riprap will be completely removed and the
surface has to be prepared for subsequent re-laying of the riprap. The
surface preparation will produce significant amounts of soil material which
need disposal.
Increasing the possibilities of erosion
The proposed construction need significant amounts of soil excavation
During site clearance activities, removal of spoil and debris must be carried out swiftly
and in well-planned manner.
Identify the sites for disposal of material cleared is needed prior to commencement of
the work.
Plants, shrubs and other vegetation cleared should not be burned on site.
Debris, spoil and other disposal materials should only be dumped at sites for which prior
approval from relevant authorities such as the LA has been obtained. Taking into account
the following
- The dumping does not impact natural drainage courses
- No endangered / rare flora is impacted by such dumping
- Should be located in non-residential areas located in the downwind side
- Located at least 100 m from the designated forest land.
- Avoid disposal on productive land.
- should be located with the consensus of the local community, in consultation
with the engineer and shall be approved by the highways department
- Minimize the construction debris by balancing the cut and fill requirements.
The contractor should avoid any spillage of spoil when transporting such materials to
the approved material dumping sites.
Debris material shall be disposed in such a manner that the tank, canals and other
existing drainage paths are not blocked (as described above)
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(38,043 m3 of excavation for structures and 2.971 m3 for foundations)
before construction of the spillway, spillway bed and the stilling bed.
Embankment construction and road construction involved in the bridge
construction need stripping of top soil, excavation of embankments, filling
and compaction. Such earth work will lead to soil erosion, slope erosion
and erosion of the road surfaces.
Raw water quality of surface water bodies
Raw water quality of surface water bodies can be affected due to soil
erosion. Soil particles that enter nearby water bodies, such as the tank and
canals etc., can result in temporary turbidity problems. However, the
duration of this exposure is short in duration and hence adverse impacts
anticipated would be not be significant.
Hindrance to vehicular movements, damage to the crest road surface
due to movement of heavy vehicles, temporary storage of earth along
the crest road and elsewhere
Drainage paths associated with the dam and other irrigation structures should be
improved / erected to drain rain water properly.
Silt traps will be constructed to avoid siltation into the water ways, the tank and canals,
where necessary.
To avoid siltation, drainage paths should not be directed to the tank and irrigation canals
and they should be separated from these water bodies
Bund Embankment slopes, slopes of cuts, etc. shall not be unduly exposed to erosive
forces. These exposed slopes shall be graded and covered by grass or other suitable
materials per the specifications.
All fills, back fills and slopes should be compacted immediately to reach the specified
degree of compaction and establishment of proper mulch.
Work that lead to heavy erosion shall be avoided during the raining season. If such
activities need to be continued during rainy season prior approval must be obtained
from the Engineer by submitting a proposal on actions that will be undertaken by the
contractor to prevent erosion.
The work, permanent or temporary shall consist of measures as per design or as directed
by the engineer to control soil erosion, sedimentation and water pollution to the
satisfaction of the engineer. Typical measures include the use of berms, dikes sediment
basins, fiber mats, mulches, grasses, slope drains and other devices. All sedimentation
and pollution control works and maintenance thereof are deemed, as incidental to the
earthwork or other items of work and no separate payment will be made for their
implementation.
The excavation, earthwork transportation, piling of earth, removal of spoil and debris,
removal of the existing riprap and piling of rubble along the crest road should be planned
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The earthwork involved in the construction work is large (41,000 m3).
Borrow material once brought to the site (7,915 m3) has to be unloaded
and stockpiled for subsequent use. This might block the existing run on and
off paths which may create erosion problems elsewhere.
Material transport (7,915 m3 of earth; approx. 5,000 m3 of concrete) may
result in congestion of local roads. There are dwelling units along haulage
routes and elevated levels of traffic matter can become a minor temporary
adverse impact during the construction period. Movement of heavy
vehicles will damage the crest road and access roads in the vicinity.
Noise and vibration
Large amounts of earth work (more than 41,000 m3 of earth excavation,
demolition of the existing road surface (468 m3), stripping of the top soil
(340 m3) and most of the other activities will generate noise. Compacting
large areas and large amounts of concrete will generate significant
amounts of noise. Much of the proposed work will be carried out using
machinery. However, small machinery will be used for excavating and
rubble and earth transport. Noise and vibration is expected to be
significantly high due to the large-scale nature of construction.
carefully. One half along the road can be used for piling of earth and rubble.
Vehicle movement along the crest road should be restricted. Axial loads of the vehicles
travelling along the crest road should be limited (based on the bearing capacity of the
bund).
Vehicular movements along the local roads should be planned based on a proper traffic
study. Proper signage should be erected for safety.
Noise from vehicles, machinery and equipment
Hydraulically driven machinery is preferred over Pneumatic machinery to minimize vibrations
Noise generating work should be limited to day time (6:00 AM to 6:00 PM). No work that
generates excessive noise should be carried out during night hours where in close
proximity (from 6:00 PM to 6:00 AM on the following day).
All equipment and machinery should be operated at noise levels that do not exceed the
permissible level of 75 dB (during construction) for the day time. For all construction
activities undertaken during the night time, it is necessary to maintain the noise level at
below 50 dB as per the Central Environmental Authority (CEA) noise control regulations
All equipment should be in good serviced condition. Regular maintenance of all
construction vehicles and machinery to meet noise control regulations stipulated by the
CEA in 1996 (Gazette Extra Ordinary, No 924/12) must be conducted for
vehicles/machinery that will be used in construction on site and for transport.
Ideally noise generating work should not be carried out during public holidays and
religious days. Special care should be taken as there is a temple nearby.
Labor gangs should be warned to work with minimum noise. Strict labor supervision
should be undertaken in this respect. Number of night time resident laborers should be
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Dust generation
Large amounts of earth work (more than 41,000 m3 of earth excavation,
demolition of the existing road surface (468 m3), stripping of the top soil
(340 m3) and most of the other activities would produce airborne dust,
which are temporary and limited to short durations and will be restricted
to a small area. Therefore, air pollution due to the proposed work can be
considered not significant.
minimized.
Vehicular noise pollution at residential / sensitive receptors
Idling of temporary trucks or other equipment should not be permitted during periods
of loading / unloading or when they are not in active use. The practice must be ensured
especially near residential / commercial / sensitive areas.
Stationary construction equipment will be kept at least 500m away from sensitive
receptors, where possible. These include places of worship and households.
All possible and practical measures to control noise emissions during drilling shall be
employed.
Contractor shall submit the list of high noise/vibration generating machinery &
equipment to the engineer for approval.
Servicing of all construction vehicles and machinery must be done regularly and during
routine servicing operations, the effectiveness of exhaust silencers will be checked and
if found defective will be replaced.
Maintenance of vehicles, equipment and machinery shall be regular and up to the
satisfaction of the Engineer to keep noise levels at the minimum.
All construction materials such as sand, metal, lime, bricks etc. should be transported
under cover to the site and stored under cover at the sight. Plastic sheeting (of about 6
mm minimum thickness) can be used and held in place with weights, such as old tires or
cinder blocks, with the edges of the sheeting buried, or by the use of other anchoring
systems. This will minimize the levels of airborne dust.
Mud patches caused by material transporting vehicles in the access road should be
immediately cleaned.
Continual water sprinkling should be carried out in the work and fill areas and the access
road if dust stir is observed. Water sprinkling should be done more frequently on days
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Pollution of Soil and Water via Fuel and Lubricants
The earthwork, large amounts of concrete work, and erection of the bridge
need a large fleet of heavy vehicles and heavy machinery. Activities such as
operation of construction vehicles, parking areas, fuel/lubricants spills
storage sites, machinery and equipment maintenance and refueling will
generate pollutants that have the potential to pollute soil and water.
Construction and removal of coffer dams
Transport of sheet piles, driving and removing of the sheet piles cause
numerous impacts. Noise and dust can result from transportation
activities. Noise and vibration due to pile driving and removing can cause
disturbance to neighboring community and the wildlife.
Sheet piles should be able to cutoff water movements across the coffer
dam for facilitating the construction activities.
that are dry and windy (at least four time’s day) as the levels of dust can be elevated
during dry periods.
Dust masks should be provided to the laborers for the use at required times.
All construction vehicle parking location, fuel/lubricants storage sites, vehicle, machinery and equipment maintenance and refueling sites shall be located away from the reservoir, at least 200 m away, and irrigation canal/ponds.
All vehicle/machinery and equipment operation, maintenance and refueling will be carried out in such a fashion that spillage of fuels and lubricants does not contaminate the ground.
Collect, store and dispose oily wastes to the pre-identified disposal sites approved by the Engineer. All spills and collected petroleum products will be disposed of in accordance with standards set by the CEA/MoE, certified by the Engineer.
Transport of sheet piles, conveyance of machinery etc. will cause impacts due to
transportation as described above (noise, dust, impacts related to parking, congestion,
damage of the bund road, oil and grease spills etc.). Mitigation of such impacts are
needed.
Sheet pile driving for the coffer dams involves generation of high levels of noise and
vibration. Therefore, construction should proceed with caution and with least damage
to adjacent structures and minimum disturbance to the community and wildlife.
Driving and removing sheet piles will temporarily increase turbidity and will cause
disturbance to the bottom sediments. However, this will be temporary. No mitigation is
required other than following good construction practices.
Construction and subsequent removal of the cofferdam must be planned and executed
with the same degree of care as its installation, on a stage by stage basis as per the
approved Method statement by the engineer.
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Health and sanitation of worker’s camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
Safety requires that every cofferdam and every part thereof shall be of suitable design
and construction, of suitable and sound materials and of Sufficient strength and capacity
for the purpose for which it is used.
Thus all material used will be pre assessed by the engineer prior to use and cleared in
writing as suitable for the purpose.
As the effect of the removal on the permanent structure must also be considered. For
this reason, it may be advisable that sheet piles extending below the permanent
structure are cut off and left in place, since their removal may damage the foundation
soils adjacent to the structure.
Stringent supervision of respective loads on coffer dams at operation should be done in
order to avoid accidents and ensure worker safety
(It is assumed that construction of the coffer dam would be done only after a thorough
hydrological and geological study. This should aim at prevention accidental damage of
the coffer dam structure due to predictable water level fluctuations and the bottom
geology would be capable enough to support the sheet piles in withstanding hydraulic
pressures.)
IT is very important that the construction is carried out during the dry season, thereby
ensuring that there is no spill take place during the construction. It has to ensure that
any excess water be released only through the sluices. If there is rains during the
construction period, it is very important to control the water level continuously to
ensure that there is no need for spilling of excess water from the reservoir. Water level
raw down to an appropriate level prior to construction is recommended.
The mitigation measures and general conditions are described in Section 5.5 (Operation
of labour camps).
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hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Management of waste (other than construction and excavated
material) and wastewater
Significant quantities of construction waste (e.g., during stripping of top
soil) are expected. In contrast, food items even in small quantities may
attract stray animals. However, the overall impact is very low.
Safety of workers at work
The earthwork involved in the construction work is large (41,000 m3).
Borrow material once brought to the site (7,915 m3) has to be unloaded
and stockpiled for subsequent use. The prestressed concrete sections have
to be unloaded, and subsequently handled carefully to erect the bridge.
These activities pose a severe hazard and potential to cause physical injury
to workers during moving heavy loads downhill/uphill.
Construction waste shall be collected regularly and disposed of periodically in an environmentally safe and nuisance free manner.
Wastewater will be disposed, by way of a pit latrine/soakage arrangement. This measure
too will be common and valid for the entire construction period.
The mitigation measures and general conditions are described in Section 5.4 (Safety at
work)
Issue
Damage in the rip rap in some areas
Intervention
Placing rip rap
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Anticipated Impacts Mitigation measure
Impact on ecological environment:
Removal of vegetation, mainly the herbs and shrubs close to the water level, disturbances to the habitats due to the removal of vegetation. Significant impact are not envisage during the construction.
Site specific mitigatory measures are not required. Once the construction of rip rap is completed natural regeneration of plants, mainly the grasses and herbs will take place.
Impact on social environment:
If rip rap rehabilitation cannot be completed within the water low period
in the tank there may be need to lowering the water level or to postpone
the woRk to the next water low period of the tank
The contractors will be encouraged to complete the work during water low period of the
tank and also continues monitoring of the contractors' progress on completion of rip rap
rehabilitation within the planned period of time.
Impacts on physical environment:
Increasing the possibilities of erosion of the U/S slopes
Exposed areas of the bund are susceptible to erosion.
Hindrance to surface runoff, hindrance to vehicular movements during
temporary storage of material along the crest road and elsewhere
Borrow material once brought to the site has to be unloaded and stockpiled
for subsequent use. This might block the existing run on and off paths
which may create erosion problems elsewhere.
The quantity to be handled seems to be large hence the impact may be
relatively significant (exact quantity to be determined)
Raw water quality of surface water bodies
Runoff through material borrow areas and unloading sites could lead to
wash off of soil particles to nearby water bodies such as canals, tanks
streams etc. resulting in temporary turbidity problems. However, the
quantity to be handled seems to be very low, hence adverse impacts
anticipated would be insignificant.
There will be 3,575 m3 of rubble removed from the existing riprap, which will be piled
along the crest road. In addition, 3,050 m3 of rubble is needed for the construction of
the rip rap. In addition to the more than 6,000 m3 of rubble, 1,650 m3 of gravel and 970
m3 of well-graded aggregate are required for the base construction of the rip rap.
Debris material shall be disposed in such a manner that the tank, canals and other
existing drainage paths are not blocked (as described above)
Drainage paths associated with the dam and other irrigation structures should be
improved / erected to drain rain water properly.
Silt traps will be constructed to avoid siltation into the water ways, the tank and canals,
where necessary.
To avoid siltation, drainage paths should not be directed to the tank and irrigation canals
and they should be separated from these water bodies
Bund Embankment slopes, slopes of cuts, etc. shall not be unduly exposed to erosive
forces. These exposed slopes shall be graded and covered by grass or other suitable
materials per the specifications.
All fills, back fills and slopes should be compacted immediately to reach the specified
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Hindrance to vehicular movements, damage to the crest road surface
due to temporary storage of rubble among the crest road and
elsewhere
Material transport may result in air pollution through giving rise to
elevated levels of airborne dust. There are dwelling units along haulage
routes and elevated levels of airborne particulate matter can become a
minor temporary adverse impact during the construction period.
Generation of noise, vibration and dust affecting the social and
biological environment
Noise and vibration can occur during compaction of the aggregate layer
and related activities. Activities that would produce airborne dust are
temporary and limited to short durations and will be restricted to a small
area.
Pollution of Soil and Water via Fuel and Lubricants
Activities such as operation of construction vehicles, parking areas, fuel/lubricants spills storage sites, machinery and equipment maintenance and refueling will generate pollutants that have the potential to pollute soil and water.
degree of compaction and establishment of proper mulch.
Work that lead to heavy erosion shall be avoided during the raining season. If such
activities need to be continued during rainy season prior approval must be obtained
from the Engineer by submitting a proposal on actions that will be undertaken by the
contractor to prevent erosion.
The work, permanent or temporary shall consist of measures as per design or as directed
by the engineer to control soil erosion, sedimentation and water pollution to the
satisfaction of the engineer. Typical measures include the use of berms, dikes sediment
basins, fiber mats, mulches, grasses, slope drains and other devices. All sedimentation
and pollution control works and maintenance thereof are deemed, as incidental to the
earthwork or other items of work and no separate payment will be made for their
implementation.
The material transportation, and storage of this material should be planned carefully.
One half along the road can be used for piling the rubble removed from the existing rip
rap. Other material should be stored appropriately, avoiding any erosion of stored earth
and gravel, not obstructing drainage pathways etc.
The work can proceed phase by phase, each phase restricted to about 50-75 m. The
surface of the slope can be prepared for subsequent laying of the new rip rap without
delay, using the removed rubble and replenishing new material as needed. If such a
procedure is followed, the need for large amounts of handling rubble at one occasion
can be avoided, thus not requiring large storage areas for piling material, especially along
the crest road.
Noise from vehicles, machinery and equipment
Hydraulically driven machinery is preferred over Pneumatic machinery to minimize vibrations
Noise generating work should be limited to day time (6:00 AM to 6:00 PM). No work that
generates excessive noise should be carried out during night hours where in close
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proximity (from 6:00 PM to 6:00 AM on the following day).
All equipment and machinery should be operated at noise levels that do not exceed the
permissible level of 75 dB (during construction) for the day time. For all construction
activities undertaken during the night time, it is necessary to maintain the noise level at
below 50 dB as per the Central Environmental Authority (CEA) noise control regulations
All equipment should be in good serviced condition. Regular maintenance of all
construction vehicles and machinery to meet noise control regulations stipulated by the
CEA in 1996 (Gazette Extra Ordinary, No 924/12) must be conducted for
vehicles/machinery that will be used in construction on site and for transport.
Ideally noise generating work should not be carried out during public holidays and
religious days. Special care should be taken as there is a temple nearby.
Labor gangs should be warned to work with minimum noise. Strict labor supervision
should be undertaken in this respect. Number of night time resident laborers should be
minimized.
Vehicular noise pollution at residential / sensitive receptors
Idling of temporary trucks or other equipment should not be permitted during periods
of loading / unloading or when they are not in active use. The practice must be ensured
especially near residential / commercial / sensitive areas.
Stationary construction equipment will be kept at least 500m away from sensitive
receptors, where possible. These include places of worship and households.
All possible and practical measures to control noise emissions during drilling shall be
employed.
Contractor shall submit the list of high noise/vibration generating machinery &
equipment to the engineer for approval.
Servicing of all construction vehicles and machinery must be done regularly and during
routine servicing operations, the effectiveness of exhaust silencers will be checked and
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if found defective will be replaced.
Maintenance of vehicles, equipment and machinery shall be regular and up to the
satisfaction of the Engineer to keep noise levels at the minimum.
Dust Control
All construction materials such as sand, metal, lime, bricks etc. should be transported
under cover to the site and stored under cover at the sight. Plastic sheeting (of about 6
mm minimum thickness) can be used and held in place with weights, such as old tires or
cinder blocks, with the edges of the sheeting buried, or by the use of other anchoring
systems. This will minimize the levels of airborne dust.
Mud patches caused by material transporting vehicles in the access road should be
immediately cleaned.
Continual water sprinkling should be carried out in the work and fill areas and the access
road if dust stir is observed. Water sprinkling should be done more frequently on days
that are dry and windy (at least four time’s day) as the levels of dust can be elevated
during dry periods.
Dust masks should be provided to the laborers for the use at required times.
All construction vehicle parking location, fuel/lubricants storage sites, vehicle, machinery and equipment maintenance and refueling sites shall be located away from the reservoir, at least 200 m away, and irrigation canal/ponds.
All vehicle/machinery and equipment operation, maintenance and refueling will be carried out in such a fashion that spillage of fuels and lubricants does not contaminate the ground.
Collect, store and dispose oily wastes to the pre-identified disposal sites approved by the Engineer. All spills and collected petroleum products will be disposed of in accordance with standards set by the CEA/MoE, certified by the Engineer.
Construction waste shall be collected regularly and disposed of periodically in an
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Management of waste (other than construction and excavated
material) and wastewater
No significant quantities of construction waste are expected. In contrast,
food items even in small quantities may attract stray animals. However,
the overall impact is very low.
Health and sanitation of worker’s camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Safety of workers at work
Placing the rubble for the riprap will be done manually. Placing and
moving rubble from the bund crest towards the bund slopes involve
extensive amount of manual labour work. These activities pose a severe
hazard and potential to cause physical injury to workers during moving
heavy loads downhill/uphill.
environmentally safe and nuisance free manner.
Wastewater will be disposed, by way of a pit latrine/soakage arrangement. This measure
too will be common and valid for the entire construction period.
The mitigation measures and general conditions are described in Section 5.5 (Operation
of labour camps).
The mitigation measures and general conditions are described in Section 5.4 (Safety at
work)
Work should proceed phase by phase, each phase involving the work of about 50-75 m. This will prevent huge amount of rubble handling and storing along the crest, minimizing the safety issues. Laborers should be instructed to coordinate properly while carrying heavy loads. Any injuries should be attend to complying with emergency procedures.
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Issues identified during the initial site visit
Issue
Seepage areas along the downstream toes
Intervention
Construction of Toe road and toe drain
Construction of V-notches
Anticipated Impacts Mitigation measure
Impacts on ecological environment:
Removal of vegetation, disturbances to the habitats
The vegetation removal will take place during the construction of toe road and toe filter. Fauna found in the toe area of the bund would move to other habitats during the construction of the toe road. So other habitats in the vicinity of tank should not be disturbed. Habitat or species specific mitigation measures are not required. To increase the vegetation cover it is recommended to plant indigenous plant species in the project affected area once the construction is completed.
Impacts on social environment:
No impacts are expected because there is adequate land area that can be
used to establish the toe road and other infrastructure facilities required
in the downstream of the Dam
No specific mitigation measures are required.
Impacts on physical environment:
Need to dispose debris and excavated material away from the site
Construction of the toe filter and drain include removing the existing toe
drain, excavation and removal of unsuitable soil material, bed formation
and stripping of soil. Further, construction of the toe road also involves
stripping of top soil and exaction of soil. These are significant amount that
has to be disposed properly (quantities of these material have to be
determined after designs are completed).
During site clearance activities, removal of vegetation and debris must be carried out
swiftly and in well-planned manner.
Identify the sites for disposal of material cleared is needed prior to commencement of
the work.
Plants, shrubs and other vegetation cleared should not be burned on site.
Spoil and other disposal materials should only be dumped at sites for which prior
approval from relevant authorities such as the LA has been obtained. Taking into account
the following
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Increasing the possibilities of erosion of the toe areas in the D/S
Construction of the toe drain, filter and the tow road involve stripping of
top soil and loose rubble in the filter. Such exposed areas of the bund toe
area are susceptible to erosion.
Hindrance to surface runoff
Construction of the toe filter and drain include removing the existing toe
drain, excavation and removal of unsuitable soil material, bed formation
and stripping of soil. Construction of the toe road also involves stripping of
top soil and exaction of soil. These will pile up at the construction site,
which will hinder surface drainage.
Construction of the toe filter and drain need sand, graded gravel, and
rubble. Toe road construction need earth and gravel. These materials once
brought to the site have to be unloaded and stockpiled for subsequent use.
This might block the existing run on and off paths which may create erosion
problems elsewhere (quantities of these material have to be determined
after designs are completed).
The quantity to be handled seems to be fairly large hence the impact may
be moderately significant.
Raw water quality of surface water bodies
Runoff through material borrow areas and unloading sites could lead to
wash off of soil particles to nearby water bodies such as canals, tanks
streams etc. resulting in temporary turbidity problems. However, the
quantity to be handled seems to be very low, hence adverse impacts
anticipated would be insignificant.
Increase in vehicular traffic during transport of construction materials
Material transport may result in air pollution through giving rise to
elevated levels of airborne dust. There are dwelling units along haulage
- The dumping does not impact natural drainage courses
- No endangered / rare flora is impacted by such dumping
- Should be located in non-residential areas located in the downwind side
- Located at least 100 m from the designated forest land.
- Avoid disposal on productive land.
- should be located with the consensus of the local community, in consultation
with the engineer and shall be approved by the highways department
- Minimize the construction debris by balancing the cut and fill requirements.
The contractor should avoid any spillage of spoil when transporting such
materials to the approved material dumping sites.
Debris material shall be disposed in such a manner that the tank, canals and other
existing drainage paths are not blocked (as described above)
Drainage paths associated with the dam and other irrigation structures should be
improved / erected to drain rain water properly.
Silt traps will be constructed to avoid siltation into the water ways, the tank and canals,
where necessary.
To avoid siltation, drainage paths should not be directed to the tank and irrigation canals
and they should be separated from these water bodies
Bund Embankment slopes, slopes of cuts, etc. shall not be unduly exposed to erosive
forces. These exposed slopes shall be graded and covered by grass or other suitable
materials per the specifications.
All fills, back fills and slopes should be compacted immediately to reach the specified
degree of compaction and establishment of proper mulch.
Work that lead to heavy erosion shall be avoided during the raining season. If such
activities need to be continued during rainy season prior approval must be obtained
from the Engineer by submitting a proposal on actions that will be undertaken by the
contractor to prevent erosion.
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routes and elevated levels of airborne particulate matter can become a
minor temporary adverse impact during the construction period.
Health and sanitation of workers’ camps
This impact is common for all the activities. The temporary camps, if not
managed properly, may create an unhealthy environment causing health
hazards to both workers and nearby residents. However, the number of
workers to be employed seems not many. Hence the impact is insignificant.
Management of waste (other than construction and excavated
material) and wastewater
No significant quantities of construction waste (other than the excavated
material as described above) are expected. In contrast, food items even in
small quantities may attract stray animals. However, the overall impact is
very low.
Generation of noise, vibration and dust affecting the social and
biological environment
Noise and vibration can occur during compaction of the gavel bedding for
the toe road, loading berm, drains etc. and compacting the aggregate
layers. Activities that would produce airborne dust are temporary and
limited to short durations and will be restricted to a small area.
Pollution of Soil and Water via Fuel and Lubricants
Activities such as operation of construction vehicles, parking areas, fuel/lubricants spills storage sites, machinery and equipment maintenance and refueling will generate pollutants that have the potential to pollute soil and water.
Safety of workers at work
The work, permanent or temporary shall consist of measures as per design or as directed
by the engineer to control soil erosion, sedimentation and water pollution to the
satisfaction of the engineer. Typical measures include the use of berms, dikes sediment
basins, fiber mats, mulches, grasses, slope drains and other devices. All sedimentation
and pollution control works and maintenance thereof are deemed, as incidental to the
earthwork or other items of work and no separate payment will be made for their
implementation.
Noise from vehicles, machinery and equipment
Hydraulically driven machinery is preferred over Pneumatic machinery to minimize vibrations
Noise generating work should be limited to day time (6:00 AM to 6:00 PM). No work that
generates excessive noise should be carried out during night hours where in close
proximity (from 6:00 PM to 6:00 AM on the following day).
All equipment and machinery should be operated at noise levels that do not exceed the
permissible level of 75 dB (during construction) for the day time. For all construction
activities undertaken during the night time, it is necessary to maintain the noise level at
below 50 dB as per the Central Environmental Authority (CEA) noise control regulations
All equipment should be in good serviced condition. Regular maintenance of all
construction vehicles and machinery to meet noise control regulations stipulated by the
CEA in 1996 (Gazette Extra Ordinary, No 924/12) must be conducted for
vehicles/machinery that will be used in construction on site and for transport.
Ideally noise generating work should not be carried out during public holidays and
religious days. Special care should be taken as there is a temple nearby.
Labor gangs should be warned to work with minimum noise. Strict labor supervision
should be undertaken in this respect. Number of night time resident laborers should be
minimized.
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Placing the rubble for the toe filter will be done manually. Placing and
moving rubble towards the bund slopes involve extensive amount of
manual labour work. These activities pose a severe hazard and potential to
cause physical injury to workers during moving heavy loads
downhill/uphill.
Installation of the V-notches and three piezometers will have very minor
environmental impacts.
Vehicular noise pollution at residential / sensitive receptors
Idling of temporary trucks or other equipment should not be permitted during periods
of loading / unloading or when they are not in active use. The practice must be ensured
especially near residential / commercial / sensitive areas.
Stationary construction equipment will be kept at least 500m away from sensitive
receptors, where possible. These include places of worship and households.
All possible and practical measures to control noise emissions during drilling shall be
employed.
Contractor shall submit the list of high noise/vibration generating machinery &
equipment to the engineer for approval.
Servicing of all construction vehicles and machinery must be done regularly and during
routine servicing operations, the effectiveness of exhaust silencers will be checked and
if found defective will be replaced.
Maintenance of vehicles, equipment and machinery shall be regular and up to the
satisfaction of the Engineer to keep noise levels at the minimum.
Dust Control
All construction materials such as sand, metal, lime, bricks etc. should be transported
under cover to the site and stored under cover at the sight. Plastic sheeting (of about 6
mm minimum thickness) can be used and held in place with weights, such as old tires or
cinder blocks, with the edges of the sheeting buried, or by the use of other anchoring
systems. This will minimize the levels of airborne dust.
Mud patches caused by material transporting vehicles in the access road should be
immediately cleaned.
Continual water sprinkling should be carried out in the work and fill areas and the access
road if dust stir is observed. Water sprinkling should be done more frequently on days
that are dry and windy (at least four time’s day) as the levels of dust can be elevated
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during dry periods.
Dust masks should be provided to the laborers for the use at required times.
All construction vehicle parking location, fuel/lubricants storage sites, vehicle, machinery and equipment maintenance and refueling sites shall be located away from the reservoir, at least 200 m away, and irrigation canal/ponds.
All vehicle/machinery and equipment operation, maintenance and refueling will be carried out in such a fashion that spillage of fuels and lubricants does not contaminate the ground.
Collect, store and dispose oily wastes to the pre-identified disposal sites approved by the Engineer. All spills and collected petroleum products will be disposed of in accordance with standards set by the CEA/MoE, certified by the Engineer.
The mitigation measures and general conditions are described in Section 5.5 (Operation
of labour camps).
Construction waste shall be collected regularly and disposed of periodically in an environmentally safe and nuisance free manner.
Wastewater will be disposed, by way of a pit latrine/soakage arrangement. This measure
too will be common and valid for the entire construction period.
The mitigation measures and general conditions are described in Section 5.4 (Safety at
work)
Work should proceed phase by phase, each phase involving the work of about 100 m. This will prevent huge amount of rubble handling and storing along the sloping areas of the toe of the bund, minimizing the safety issues. Laborers should be instructed to coordinate properly while carrying heavy loads. Any injuries should be attended to
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complying with emergency procedures.
No mitigation needed.
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5.3 PROCUREMENT OF MATERIAL NEEDED FOR IMPLEMENTING THE PROPOSED
INTERVENTIONS
5.3.1 Material Sourcing
The proposed interventions for Pimburaththewa Reservoir need significant amounts of ruble (about
6,500 m3), gravel and earth (about 4,500 m3) and aggregates (about 1,000 m3) sand (80 m3).
Therefore, significant impacts on geological resources is anticipated at quarry sites and borrow
areas, and therefore the contractors should ensure that sand, aggregates and other quarry material
is sourced from licensed sources.
The contractor is required to maintain the necessary licenses and environmental clearances for all
borrow and quarry material they are sourcing to obtain soil , fine aggregate and coarse aggregate.
Sourcing of any material from protected areas and/or designated natural areas are strictly
prohibited.
If the contractor uses non-commercial burrow/quarry sites, the sites should be remediated
accordingly once material sourcing has been completed. The Project Supervision Engineer will
require maintaining the numbers and relevant details of all necessary licenses etc. and report of their
status accordingly.
5.3.2 Management of Borrow Sites
- Any earth excavated within the project area arising from construction works may be used as fill
material if properties of the soil are suitable for such filling. At Pimburaththewa, the excavated
soil (about 1,250 m3) can be used for filling if the Engineer finds approves its use.
- The material supplier and/or the contractor shall comply with the environmental
requirements/guidelines issued by the CEA and the respective local authorities with respect of
locating borrow areas and with regard to all operations related to excavation and transportation
of earth from such sites.
- The material supplier and/or the contractor can also find suitable soil/earth materials from
currently operated licensed burrow pits in the surrounding area, subject to approval of the
Engineer
- No borrow-sites be used (current approved) or newly established within areas protected under
FFPO and FO, especially within the Maduru Oya National Park.
- Borrow areas shall not be opened without having a valid mining license from the GSMB. The
location, depth of excavation and the extent of the pit or open cut area shall be as approved by
the engineer.
- All borrow pits/areas should be rehabilitated at the end of their use by the contractor in
accordance with the requirements/guidelines issued by the CEA and the respective local
authority.
- Establishment of borrow pits/areas and its operational activities shall not cause any adverse
impact to the near-by properties. Also shall not be a danger of health hazard to the people.
Contractor shall take all steps necessary to ensure the stability of slopes including those related to
temporary works and burrow pits.
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5.3.3 Quarry Operations and Management of Quarry Sites
- Utilizing the existing quarry sites available in the project influential area as much as possible
which are approved by GSMB with valid EPL and Industrial Mining Licenses;
- If new quarries are to be opened, prior approval should be obtained from GSMB, CEA and
local authorities such as Pradeshiya Sabha.
- Selected quarry sites should have proper safety measures such as warnings, safety nets etc.,
and third party insurance cover to protect external parties that may be affected due to
blasting.
- Quarry sites should not be established within protected sites identified under the FFPO and
FO
- It is recommended not to seek material from quarries that have ongoing disputes with
community.
- The maintenance and rehabilitation of the access roads in the event of damage by the
contractors operations shall be a responsibility of the contractor.
Copies of all relevant licenses should be maintained by the contractor for review and documentation
by the Engineer.
5.4 SAFETY ISSUES
Table 5.2: General safety issues that need to be addressed
Public and Worker
Safety
The construction site should be barricaded at all time in a day with adequate
marking, safety tape, flags, reflectors etc. for safety of individuals using the
site daily basis. (Items such as parking cones, lights, tubular markers, orange
and white strips and barricades of a luminous nature for night visibility shall
be procured where deemed necessary).
At all times, the Contractor shall provide safe and convenient passage for
vehicles, pedestrians and livestock. Work that affects the use of existing
accesses shall not be undertaken without providing adequate provisions to the
prior satisfaction of the Engineer.
The construction site should be clearly demarcated by the above means and
restriction of access to public to the site will help the safety of public.
Safety signboards should be displayed at all necessary locations.
The contractor should obtain a Third Party Insurance to compensate any
damages, injuries caused to the public or laborers during the construction
period.
All construction vehicles should be operated by experienced and trained
operators under supervision.
Basic onsite safety training should be conducted for all laborers during the
EMP training prior to the start of the construction activities.
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All digging and installation work should be completed in one go, if this task is
not accomplished the area should be isolated using luminous safety tape and
barricading structures surrounding the whole area.
Trenches should be progressively rehabilitated once work is completed.
Material loading and unloading should be done in an area, well away from
traffic and barricaded
Construction wastes should be removed within 24 hours from the site to
ensure public safety.
Safety Gear for
Labors
Protective footwear and protective goggles should be provided to all workers
employed on mixing of materials like cement, concrete etc.
Welder's protective eye-shields shall be provided to workers who are engaged
in welding works.
Earplugs shall be provided to workers exposed to loud noise, and workers
working in crushing, compaction, or concrete mixing operation.
The contractor shall supply all necessary safety appliances such as safety
goggles, helmets, safety belts, ear plugs, mask etc. to workers and staffs.
In addition, the contractor shall maintained in stock at the site office, gloves,
ear muffs, goggles, dust masks, safety harness and any other equipment
considered necessary.
A safety inspection checklist should be prepared taking into consideration
what the workers are supposed to be wearing and monitored on a monthly
basis and recorded.
Prevention of
accidents
Prevention of accidents involving human beings, animals or vehicles falling or
accidents due to open trenches/manholes during construction period. This
needs to be ensured with proper barricading, signage boards and lighting etc.
A readily available first aid unit including an adequate supply of sterilized
dressing materials and appliances should be available at the site office at all
times
Availability of suitable transport at all times to take injured or sick person(s) to
the nearest hospital should also be insured.
Names and contact information for emergency services such as Ambulance
services, hospitals, police and the fire brigade should be prepared as a sign
board and displayed at the work site.
5.5 OPERATION OF LABOUR CAMPS
The following aspects are important to follow when constructing of labor camps
The location, layout and basic facility provision of labor camp must be submitted to Engineer
prior to their construction.
The construction will commence only upon the written approval of the Engineer.
The contractor shall maintain necessary living accommodation and ancillary facilities in
functional and hygienic manner and as approved by the Engineer.
All temporary accommodation must be constructed and maintained in such a fashion that
uncontaminated water is available for drinking, cooking and washing. The sewage system for
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the camp must be planned and implemented with concurrence from the Local Public Health
Officer (PHI)
Adequate health care is to be provided for the work force. The layout of the construction
camp and details of the facilities provided should be prepared and shall be approved by the
engineer.
Labor camp sites after use should be cleared and the site should be reinstated to previous
condition at the close of the construction work.
The following aspects have to be looked into when operating labor camps.
The Contractor shall construct and maintain all labor accommodation in such a fashion that
uncontaminated water is available for drinking, cooking and washing.
Supply of sufficient quantity of potable water (as per SLS) in every workplace/labor camp site
at suitable and easily accessible places and regular maintenance of such facilities.
The sewage system for the camp are designed, built and operated in such a fashion that no
health hazards occurs and no pollution to the air, ground water or adjacent water courses
take place. Ensure adequate water supply is to be provided in all toilets and urinals.
The contractor shall provide garbage bins in the camps and ensure that these are regularly
emptied and disposed of in a hygienic manner
5.6 IMPLEMENTATION PROCEDURES OF PROPOSED MITIGATION
The specific mitigation measures given in the Table 5.1 should be implemented by the contractor
when each and every intervention is done. In addition to the specific measures, the contractor must
adhere to the civil engineering best practices as practical as possible. Most of such practices are
described in ICTAD specifications and the contractor is recommended to follow them when
appropriate.
Time of the implementation of mitigation measures should be decided by the contractor and they
should be informed to the Project Engineer in advance and his approval should be obtained. The key
performing indicators (KPIs) for every mitigation measure carried out must be worked out and
should be informed to the PM for subsequent checks and balances. Once the KPIs are accepted such
indicators should be monitored by the PM to ensure that measures are taken to minimize or avoid
environmental degradation or pollution that is very likely due to the said project.
It should be necessary that all mitigation measures mentioned in the report be implemented by the
contractor and for such implementation budgetary allocation must be set aside. It has to be done
during the bidding process and the allocation so kept must be utilized by the contractor in an
efficient manner.
Implementation responsibility: for all tasks identified below fall under the purview of the contractor.
The contractor is contractually bound to implement the activities outlined in the EMP during the
implementation of the physical works outlined in the work plan
Supervision responsibility: The Project Proponent, i.e. the project engineer, technical officers of the
respective project management units and Dam safety PMUs environmental unit will be responsible
for the monitoring of all activities and reporting on compliance of implementation as well as
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providing technical guidance to the contractor and staff on ensuring field level implementation is
achieved in a satisfactory manner.
5.7 INFORMATION DISCLOSURE AMONG STAKEHOLDERS
Discussions should be conducted with the residents who reside around the immediate vicinity
of the construction site; provide them with information on the project activities muster their
views for possible impact mitigation as this will also ensure a good rapport and fewer
complaints. This should be done immediately once the contractor is mobilized.
The contractor will maintain a log of any grievances/complains and actions taken to resolve
them.
A copy of the EMP should be available at all times at the project supervision office on site.
5.8 POST-CONSTRUCTION ACTIVITIES
Clearing/Closure of Construction Site/Labor Camps
Site restoration plans have to be formulated for approval by the engineer. The plan is to be
implemented by the contractor prior to demobilization. This includes borrow sites and
storage yards as well.
On completion of the works, all temporary structures will be cleared away, all rubbish cleared,
excreta or other disposal pits or trenches filled in and effectively sealed off and the site left
clean and tidy, at the contractor’s expenses, to the entire satisfaction of the engineer.
Environmental Enhancement/Landscaping
Landscape plantation, including turfing of bund walls, re-vegetation of embankments and
other slopes, edge treatment of water bodies shall be taken up as per either detailed design
or typical design guidelines given as part of the Bid Documents.
The contactor also shall remove all debris, piles of unwanted earth, spoil material, away from
the dam site and from other work places and disposed at locations designated or acceptable
to the Engineer.
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5.9 FORMAL CLEARANCES AND APPROVAL NEEDED
Table 5.3 gives the details of the clearances and approvals for the project
Table 5.3: Formal clearances and approval needed
No Issues / Activity / Intervention needing the permit or approval
The Reasons for the Approval (Law, act or enforcements etc)
Authority from which permit or approval or Clarence is required
Prior Approval and Acts
1 National Environmental Protection and Quality Regulations under Extraordinary Gazette notification No. 1534/18 and No. 1533/16 of 2008 under NEA section 32 & 23A, 23B
Environmental Protection License (EPL) from CEA, in particular prescribed activities in gazette No. 1533/16 of 2008 (i.e., Concrete batching plants, treatment plants, sewerage networks, mechanized mining activities etc.) is required during construction period and license need to be obtained to collect, transport, store, recover, recycle or dispose waste or establish any site or facility for the disposal of any waste during the construction and operation period.
CEA and The Local Authority (Dehiattakandiya Pradeshiya Sabha)
Environmental Protection License (EPL) from CEA/ Divisional Secretariat - Dehiattakandiya for identifying waste dumping sites /Local Authority (Dehiattakandiya Pradeshiya sabha) for waste collection and to issue machinery permits
2 Mines & Minerals Act No. 33 of 1992 The Act regulates the process of approval required for exploration, mining, trading and transport of geological material (sand, earth, gravel, metal etc.)
Geological Survey and Mines Bureau Industrial Mining License (IML) from Geological Survey and Mines Bureau
Note: Refer Section 1.1.2: Environmental Assessment Requirements for further details on The World Bank Requirements, and National Environmental
Legislation framework relevant to this Project.
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5.10 PROCEDURES FOR DEALING WITH CHANCE FINDS
5.10.1 Chance found Flora and Fauna
The contractor will take reasonable precaution to prevent workmen or any other persons
from removing and damaging any flora (plant/vegetation) and fauna (animal) including
fishing in any water body and hunting of any animal.
If any wild animal is found near the construction site at any point of time, the contractor
will immediately upon discovery thereof acquaint the Engineer and carry out the
Engineer's instructions for dealing with the same.
The Engineer will report to the nearby Forest Department /Department of Wildlife
Conservation (range office or divisional office) and will take appropriate steps/ measures,
if required in consultation with the forest officials.
5.10.2 Chance found Archaeological Property
All fossils, coins, articles of value of antiquity, structures and other remains or things of
geological or archaeological interest discovered on the site shall be the property of the
Government and shall be dealt with as per provisions of the relevant legislation.
The contractor will take reasonable precautions to prevent his workmen or any other
persons from removing and damaging any such article or thing. He will, immediately upon
discovery thereof and before removal acquaint the Engineer of such discovery and carry
out the instructions for dealing with the same, waiting which all work shall be stopped.
The Engineer will seek direction from the Archaeological Department of Sri Lanka and
inform the project EO to follow the Chance Find Procedures set forth.
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6. MONITORING PLAN
6.1 ENVIRONMENTAL COMPLIANCE AND MONITORING
Environmental monitoring is required in order to make sure that the anticipated adverse impacts
are kept minimal with the implementation of mitigation measures as and when required. The
monitoring objectives are therefore focused on the mitigation of likely impacts. In addition,
compliance with the existing regulations and legislation is also guaranteed. Table 6.1 enumerates
the summary of monitoring plan (MP) required for the entire project.
The monitoring will be required to record the stakeholder complaints/concerns to the delays of the
contractors on completing the riprap rehabilitation, sluice gates repairs of the tank. The Dam safety
project’s PMU has comprehensive monitoring mechanism on the contractors progress on the
construction contract packages offered to them but specific monitoring will be required to verify the
implementation of mitigatory measures recommended in this EA report. The most required
mitigatory measure is contractors’’ performance to complete the critical work that need to be
completed during water low period of the tank.
The process of implementing the mitigatory measures and other recommendations in the EA report
will be monitored through the existing committee system of MASL. These committees include three-
tiered institutions from bottom level to upper level. The Unit Management committee (UMC) is the
lower level one and Block Management committee (BMC) is the middle level and Project
Management committee (PMC) is the upper level one. The Dam safety project and the impacts of its
implementation in the irrigation scheme can be included as new discussion item in the agenda of
the three committee meetings. These committees meet once a month in such a way to discuss the
issues and problems in the entire irrigation scheme. The Unit committee brings the issues to the
Block committee and the Block committee forwards the issues to the project committee and
therefore, it covers the discussions of the issues in the entire irrigation scheme. This system can be
used for the monitoring system of the proposed dam safety activities and the Project committee
(PMC) will be attended by the representatives of PMU of Dam safety project and contractors as
new participants.
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Table 6.1: Summary of monitoring requirement
Specific intervention
Monitoring Parameters
Monitoring Frequency
Total Time Period Months
Responsible
Institution/ person for implementation
Responsible Key Persons for supervision
Framework of the Institutional Arrangement to incorporate the Findings of MP to Project implementation
Rehabilitation of the spillway
Provide rip rap at U/S face of the dam
Construction of toe filter and toe road
Turbidity in the working section of the tank
When such incidents occur
During the whole activity
Contractor
Project Manager or his nominee
PM to inform the contractor of the monitoring and the contractor to submit the reports as agreed;
Reports to be submitted to the Project Office (PO) and then the reports to be evaluated by the World Bank (WB) and PO for approval.
Airborne dust
(along haulage routes)
When complaints are received or dust found in dwelling units
During the whole intervention
Contractor Project Manager or his nominee
Stock piling plan
At the beginning of the intervention
During the whole intervention
Contractor Project Manager or his nominee
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Material haulage from borrow areas
Noise levels
Vibration levels
Airborne dust levels
Presence of invasive species
When a complaint is received
When a complaint is received
When a complaint is received
One in 10 vehicles of borrow martials brought in to the site
During the material transport
During the material transport
During the material transport
During the material transport
Contractor
Contractor
Contractor
Contractor
Project Manager or his nominee
Project Manager or his nominee
Project Manager or his nominee
Project Manager or his nominee
As mentioned above
As mentioned above
As mentioned above
As mentioned above
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7. COST ESTIMATION FOR ENVIRONMENTAL MANAGEMENT PLAN
7.1 COST ESTIMATE OF ENVIRONMENTAL MANAGEMENT PLAN
General costs to be incurred in implementing the EMP is given in Table 7.1
Table 0.1: Cost Estimate of EMP
Issue Mitigation Details of Costing Itemized Cost
Activities such as material transport,
soil stockpiling, etc. may result in air
pollution through airborne dust. If
there are dwelling units along haulage
routes there may be a minor
temporary adverse impact during this
period.
Dust emission due to transport
operations should be controlled by wet
spraying and tarpaulin covering in
mandatory on trucks/lorries which are
used for transporting materials
particularly in built up areas.
Sprinkling of water has to be carried out
using bowsers, or tractors where there
are dwelling unit only when necessary.
Lorries and trucks should be covered
(with tarpaulin sheets) when
transporting earth and gravel.
Sprinkling of water:
- Bowser: Rs. 5,000 -6,000 per
bowser
- Tractor: Rs. 2,500 per tractor
Covering with tarpaulin sheets:
Rs. 200/m2
Health and sanitation of worker’s
camps and that of residents in the
adjoining areas:
The temporary camps if not managed
properly may create an unhealthy
environment causing health hazards
to both workers and nearby residents.
(see section 5.4)
Proper sanitation facilities should be
provided on-site for the workforce.
Ideally, this can be a pit latrine in which
the pit is located above the ground water
table. Covering the deposit (with earth or
sawdust) is necessary to prevent smells
and to discourage flies.
Costs involved in providing pit latrines
Cost in providing provisions for proper
waste management
Rs. 10,000 – 15,000
Nominal costs
Operation of borrow areas causes
Erosion and slides in borrowing areas
occurring in hillocks would lead to loss
of topsoil and vegetation loss, hence
habitat loss.
After borrowing the slope/gradient of the
area should be graded to match or blend
with the existing terrain.
Plant the area with native trees and water
regularly
The costs that may incur involve grading
of borrow pit edges
Cost of construction depends on
the scale of the borrow pit.
The cost of the rehabilitation of
the borrowing area with turfing
will be Rs. 500 per 1 m2.
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Issue Mitigation Details of Costing Itemized Cost
Re-establishment of vegetation would
be hindered due to loss of fertile soil
Any borrow pits on the tank bed also
should be graded properly.
Replanting/ rehabilitation of
habitats (e.g. in borrow sites)
need a budget of Rs. 400,000 /ha
for replanting.
Safety of Workers and Public
(as outlined in Table 5.2)
Provision of proper safety equipment,
safety gear, taking precautions and
preventive measures etc. as outlined in
Table 5.2
Safety gear, appliances and equipment,
signage and warning signs, third party
insurance and worker liability insurance,
cost of training provided to workers
Nominal sums to be included in
the engineering estimates to be
borne by the Contractor
Closure of Construction Site/Labor
Camps
Environmental
Enhancement/Landscaping
Site restoration plans have to be
formulated for the construction site
All temporary structures shall be cleared
away, all rubbish cleared, excreta or
other disposal pits or trenches filled in
and effectively sealed off and the site left
clean and tidy.
Remove all debris, piles of unwanted
earth, spoil material and disposed at
designated locations.
Landscape plantation, including turfing
of bund walls, re-vegetation of
embankments and other slopes, etc.
Nominal sums to be included in
the engineering estimates to be
borne by the Contractor.
Nominal sums to be included in
the engineering estimates to be
borne by the Contractor.
Rs. 40/m2 for turfing
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Major issues that need mitigation and the related costs are provided in Table 7.1. Most of the
mitigation measures are related to good construction practices and related mitigation costs for most
of the items are embedded in the Engineering Cost Items. However, if the following items are not
directly given under the Engineering Cost, the construction contractor should make necessary
provisions to undertake the relevant items and costs should be included in contractor’s rates.
Salary for officer to monitor environmental management plan implementation (as provided
in Table 6.1)
Costs for environmental monitoring for specific interventions and measuring parameters as
stipulated in project specific environmental assessment (See Table 5.1 and 6.1)
Miscellaneous fees for the organizations involving in monitoring activities.
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8. CONCLUSIONS AND RECOMMENDATIONS
8.1 CONCLUSIONS
The proposed interventions for the repair work of the spillway, and the approach channel together
with the bridge construction involve major construction activities. Removal of existing gabion
structures, excavation of spillway approach channel, repair to the spillway side walls, bed and the
stilling basin, excavations for spillway construction are major construction activities which will cause
moderately significant impacts. Removal of the existing concrete road, construction of
embankments to support the bridge deck, construction of the bridge over the spillway and
construction of the road over the bridge and on either side of the bridge is also interventions which
will cause moderately significant impacts.
Removal and disposal of debris and excavated material, and increasing the possibilities of erosion
can deteriorate water quality of surface water bodies. Hindrance to vehicular movements, damage
to the crest road surface due to movement of heavy vehicles, temporary storage of earth along the
crest road and elsewhere, impacts due to parking of vehicles and machinery have to be monitored
closely. Noise and vibration and dust generation also can occur due to large-scale construction using
heavy machinery.
Construction and removal of coffer dams is one of the major interventions which need careful
attention. It is assumed that construction of the coffer dam would be done only after a thorough
hydrological and geological study. This should aim at prevention accidental damage of the coffer
dam structure due to predictable water level fluctuations and the bottom geology would be capable
enough to support the sheet piles in withstanding hydraulic pressures. Also, the work has to be
carried out during the dry season only, when the water level can be controlled. Always, the water
level fluctuations (especially rising water levels) have to be monitored during and after rainfalls. If
needed, the sluice gates can be opened sufficiently to draw down the water levels appropriately.
The Pimbureththewa tank project area can be categorized mainly as having human-influenced-
habitats. This is amply reflected by the habitats and species assemblages recorded during the survey.
The areas identified for project interventions do not contain any critical habitats or restricted or
endangered species. The main impact anticipated in these habitats includes the habitat degradation,
fragmentation and loss of habitat. There will not be a total loss of habitat for any animal or plant
species in the project area. Therefore, habitat or species specific mitigatory measures are not
required. No specific migratory paths or routes were identified within the project area. The proposed
development will not have an impact on migratory birds. The proposed project will not impair animal
movements in the project area, and it will not have a significant impact on any known critical animal
migration paths.
The rip rap and spillway rehabilitation in the Dam are the sensitive work items from the social impact
point of view. Low water levels will be a requirement to complete these activities. The water level in
the tank goes down for short period just after the Yala harvesting. This is the period to be used for
the completion of these sensitive construction activities proposed.
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If the contractors fail to complete the sensitive work items during the short dry spell in which water
level is naturally low there will be negative implications on seasonal agriculture in the scheme.
Therefore, this crucial issue should be considered as most priority activity to be monitored by PMU
and also RPM's office in System C through its existing joint management committee system ( UMCs,
BMC and PMC) where farmer representatives and agency officers sit together to discuss the
problems in their irrigation scheme in every month.
Other interventions are accepted and the project can go ahead without any specific environmental
mitigation measures. Nevertheless, best practices listed on the EMP should be practiced as practical
as possible. ICTAD specifications on civil engineering practices must be followed as and when
applicable.
All the borrow sites need better managements in order to avoid or minimize pollution potential and
best practices for managing sites should be adopted.
The proposed project will therefore be carried out together with the implementation of mitigation
measures stated in this report.
8.2 RECOMMENDATIONS
The project area is situated in the dry zone of the country. Compared to the wet zone habitats the
dry zone does not support critical elements of Sri Lanka’s biodiversity such as endemic and
threatened species as was observed during the field study. The habitats present in the project site
are highly degraded. The majority of habitats and species that are affected by the proposed project
are found commonly throughout the dry zone and therefore the overall impact is not significant
considering the extent and magnitude of the impact. It is recommended that project proponent
develop and execute an environmental management plan to ensure best practices during the
implementation of the project. It is also recommended that project proponent undertake to restore
the habitats with indigenous species in order to partially compensate for the loss of habitats due to
the implementation of the proposed project. Finally it is recommended that an appropriate
independent monitoring mechanism with relevant funds be established to ensure that the project
proponent complies with the proposed mitigation measures.
Removal and disposal of debris and excavated material, and increasing the possibilities of erosion
can deteriorate water quality of surface water bodies. Hindrance to vehicular movements, damage
to the crest road surface due to movement of heavy vehicles, temporary storage of earth along the
crest road and elsewhere, impacts due to parking of vehicles and machinery have to be monitored
closely. Noise and vibration and dust generation also can occur due to large-scale construction using
heavy machinery.
Construction and removal of coffer dams is one of the major interventions which need careful
attention
Engineering best practices must be recommended to be adopted by the contractor for the sound
engineering work.
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Borrow sites must be utilized with a proper rehabilitation and safety plan for the protection of fauna
inhabiting the area. All the borrow/quarry areas should be accepted for material exploitation only if
proper approvals from the relevant authorities are obtained.
When complaints are received from the neighbourhood on the environmental issues, immediate
attention and solutions to such issues are recommended.
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ANNEXURES
ANNEX 1: DETAILS OF THE FARMING COMMUNITY
List of person consulted
No Name Position Address Telephone
1 A.D.Wijerathna Block Manager Wijayabapura, Block office 071-8281903
2 K.Wijerathna D.R.P.M D.R.P.M Office, Walikanda 071-2080161
3 E.M.Chandratilaka President Lihini inland fisheries association
137,Dambasewana,Track 1, Pimburattawa
072-42620991
4 D.M.Kulatunga Community Leader No 61,Track 1, Pimburattawa
5 W.A.Tilakarathna President Aralaganwila, Wijayaba FO, Aralaganwila
072-42621148
6 S.A. Indrani Secretary Pimburattawa Parakum FO, Pimburattawa
7 E.A.Ariyawansha President Pimburattawa Parakum FO, Pimburattawa
072-9390440
8 B.M.Basnayaka President Madagama ,Saruketha FO, Madagama
078-9000255
9 Anoma Damayanthi Treasurer Madagama ,Saruketha FO, Madagama
10 K.H.B.Gunarathna President Pimburattawa Ekamuthu FO, Pimburattawa
072-4069380
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ANNEX 2: DETAILS OF THE COST BENEFIT OF AN ACRE OF PADDY LAND IN PIMBURATTEWA
Yield /acre/season Gross Income- Rs. Expenditure item Rs.
2,420 kg (110 bushel * 22kg)
87,120/- (2,420*36) Ploughing (tractor) 8,500.00
Preparation of field bank (activity 1)
3,600.00
Preparation of field bank (activity 2)
4,800.00
Seed paddy 3,500.00
Basel fertilizer 600.00
sowing 3,600.00
Agrochemical 1 3,500.00
Agrochemical 2 1,200.00
Second application of fertilizer
600.00
Agrochemical 3 800.00
Agrochemical 4 1,200.00
Third application of fertilizer
600.00
Harvesting 8,500.00
Transport of paddy 2,000.00
Drying of paddy 3,600.00
TOTAL 46,600.00
Note: Gross income Rs. 87,120/-, total expenditure Rs. 46,600/- therefore net income Rs. 40,520 /=
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ANNEX 3: LOCATION MAP FOR THE IDENTIFIED QUARRY AND BORROW SITES FOR PIMBURATHTHEWA TANK
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ANNEX 4: FAUNA RECORDED FROM PIMBURATTEWA SITES
GROUP Family Species English Name NCS1 Spillway Rubble Storage site
DRAGONFLIES
Libellulidae
Acisoma panorpoides Asian Pintail + -
Orthetrum glaucum Asian Skimmer + +
Orthetrum pruinosum Pink Skimmer + -
Orthetrum sabina Green Skimmer + +
Neurothemis tullia Pied Parasol + -
Rhyothemis variegata Variegate Flutterer - + BUTTERFLIES
Papilionidae
Graphium agamemnon Tailed Jay - +
Pachliopta aristolochiae Common Rose + +
Papilio demoleus Lime Butterfly + +
Papilio polytes Common Mormon + +
Pieridae
Appias albina Common Albatross + +
Appias galene* Sri Lanka Lesser Albatross + +
Catopsilia pyranthe Mottled emigrant + +
Catopsilia pomona Lemon emigrant + +
Delias eucharis Jezebel + +
Eurema hecabe Common grass yellow + +
Leptosia nina Psyche + +
Nymphalidae
Acraea violae Tawny costor - +
Ariadne ariadne Angled castor - +
Danaus chrysippus Plain tiger + +
Danaus genutia Common tiger + +
Elymnias hypermnestra Common palmfly + +
Euploea core Common crow + +
Junonia atlites Grey pansy + +
Junonia iphita Chocolate Soldier + +
Melanitis leda Common evening brown + +
Mycalesis perseus Common bushbrown - +
Neptis hylas Common sailor + +
Parantica aglea Glassy tiger + +
Ypthima ceylonica White Four-ring + +
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GROUP Family Species English Name NCS1 Spillway Rubble Storage site
BUTTERFLIES
Lycaenidae
Caleta decidia Angled Pierrot + +
Castalius rosimon Common Pierrot + +
Chilades pandava Plains Cupid + +
Jamides bochus Dark Cerulean - +
Jamides celeno Common Cerulean + +
Zizeeria karsandra Dark Grass Blue + +
Zizina otis Lesser Grass Blue + +
Hesperiidae
Iambrix salsala Chestnut Bob - + AMPHIBIANS
Ranidae
Euphlyctis cyanophlyctis Skipper frog + +
Euphlyctis hexadactylus Indian green frog + -
Fejervarya limnocharis Common paddy field frog + +
Hoplobatrachus crassus Jurdon's bullfrog - + REPTILES
Agamidae
Calotes calotes Green garden lizard - +
Calotes versicolor Common garden lizard - +
Scincidae
Eutropis carinata Common skink - +
Varanidae
Varanus bengalensis Land monitor + -
Varanus salvator Water monitor - +
Colubridae
Ptyas mucosa Rat snake - +
Natricidae
Xenochrophis piscator Checkered Keelback - + BIRDS
Phasianidae
Gallus lafayetii* Sri Lanka Junglefowl - +
Picidae
Dinopium psarodes* Sri Lanka Lesser Flameback - +
Ramphastidae
Megalaima zeylanica Brown-headed Barbet + +
Megalaima haemacephala Coppersmith Barbet - +
Alcedinidae
Halcyon smyrnensis White-throated Kingfisher + +
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Meropidae
Merops orientalis Green Bee-eater + +
Merops leschenaulti Chestnut-headed Bee-eater - +
Cuculidae
Clamator jacobinus Pied Cuckoo + -
Eudynamys scolopacea Asian Koel - +
Phaenicophaeus viridirostris Blue-faced Malkoha - +
Psittacidae
Psittacula krameri Rose-ringed Parakeet + +
Apodidae
Cypsiurus balasiensis Asian Palm Swift + +
Columbidae
Columba livia Rock Pigeon CR - +
Streptopelia chinensis Spotted Dove + +
Charadriidae
Vanellus indicus Red-Wattled Lapwing + -
Accipitridae
Haliastur indus Brahminy Kite - +
Ichthyophaga ichthyaetus Grey-Headed Fish-eagle - +
Spilornis cheela Crested Serpent Eagle + -
Ardeidae
Ardeola grayii Indian Pond Heron - +
Egretta garzetta Little Egret + -
Laniidae
Lanius cristatus Brown Shrike - +
Oriolidae
Oriolus xanthornus Black-hooded Oriole + +
Dicruidae
Dicrurus caerulescens White-bellied Drongo + +
Sturnidae
Acridotheres tristis Common Myna + +
Campephagidae
Pericrocotus flammeus Scarlet Minivet - +
Rhipiduridae
Rhipidura aureola White-browed Fantail + -
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GROUP Family Species English Name NCS1 Spillway Rubble Storage site
BIRDS
Aegithinidae
Aegithina tiphia Common Iora - +
Pycnonotidae
Pycnonotus cafer Red-vented Bulbul + +
Pycnonotus luteolus White-browed Bulbul + +
Cisticolidae
Prinia inornata Plain Prinia + +
Sylviidae
Orthotomus sutorius Common Tailorbird + -
Timalidae
Turdoides affinis Yellow-billed Babbler + +
Dicaeidae
Dicaeum erythrorhynchos Pale-billed Flowerpecker - +
Nectariniidae
Nectarinia zeylonica Purple-rumped Sunbird + +
Nectarinia lotenia Loten’s Sunbird - +
Estrididae
Lonchura striata White-rumped Munia - + MAMMALS
Cercopithecidae
Macaca sinica* toque monkey - +
Hystricidae
Hystrix indica Porcupine - +
Herpestidae
Herpestes brachyurus Brown mongoose + +
Elephantidae
Elephas maximus Elephant EN - +
Cervidae
Axis axis Spotted Deer - +
Canidae
Canis familiaris Domestic Dog + -
Sciuridae
Funambulus palmarum Palm squirrel + +
Leporidae
Lepus nigricollis Black-naped hare + +
Suidae
Sus scrofa Wild boar + +
Tragulidae
Moschiola meminna* Sri Lanka pigmy mouse-deer - +
NCS1 - National Conservation Status (MOE, 2012)
CR - Critically Endangered, EN - Endangered, VU - Vulnerable, * Endemic
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Reference MOE 2012. The National Red List 2012 of Sri Lanka; Conservation Status of the Fauna and Flora. Ministry of Environment, Colombo, Sri Lanka. viii + 476pp.
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ANNEX 5: PHOTOGRAPHS – SOCIO ECONOMIC SURVEY
Discussion with Block Manager, A.D.Wijerathna, Wijayabapura, Block Office
Collecting socio-economic data from a community member