Itojo-Sempaya Road Project-Final Report-Edited (03-02-08).pdf

7/30/2019 Itojo-Sempaya Road Project-Final Report-Edited (03-02-08).pdf

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ROAD SECTOR PROJECT 2: FORTPORTAL-BUNDIBUGYO-LAMIA ROADDETAILED DESIGN FOR THE UPGRADING OF ITOJO-SEMPAYA ROAD (ALTERNATIVE 2A) FINAL DESIGN REPORT

February 2008 - i -

EXECUTIVE SUMMARY

1.0 GeneralA detailed engineering design for Fortportal-Bundibugyo road was undertaken by M/S

Tecnica y Proyectos S.A. in association with M/S PROME Consultants Ltd. However itwas established that the existing route between Itojo and Sempaya comprises severalsharp bends that cannot accommodate articulated trucks. As a consequence,Government engaged M/s TYPSA in association with PROME Consultants Ltd to carry-out a desk study with the objective of investigating the economic, environmental andengineering feasibility of a possible deviation from the existing road betweenKichwamba and Karugutu and between Sempaya and Itojo. No diversion wasestablished between Kichwamba and Karugutu. However, regarding the Itojo Sempaya section, a possible route from Itojo traversing through Kibuku, Rwamabaleand Burondo trading centres and connecting with the main Fort Portal Bundibugyo Lamia road at Sempaya close to the Semliki hot springs was established (refered to asAlternative 2A).This alternative route is approximately 24.477 Km while the existing

route (along the Fortportal_bundibugyo road) is 13.82 Km. Ministry of Works andTransport (MoWT) represented by Road Agency Formation Unit (RAFU), engaged M/SPROME Consultants Ltd to carry out a detailed engineering design for the above Itojo-Sempaya Road (Alternative 2A) which design upon approval shall be incorporated intothe main design of the Fort Portal Bundibugyo Lamia road by replacing the existingItojo Sempaya road link (along the Fortportal-Bundibugyo-Lamia) thus forming thefinal design of the entire road project.

2.0 The Project Road

The project road diverges from the existing road near a military post at about Km 34 +800 (Itojo trading centre) from Fort Portal town and descends towards a low-lying area

which extends towards River Semliki and further on to Lake Albert. The routetraverses through Kibuku, Rwamabale and Burondo trading centres and joins theRwebisengo to Sempaya road before continuing to Sempaya. This existing Rwebisengo -Sempaya road is an earth road with an approximate width of 4.5 m while the sectionfrom Itojo is mostly an existing earth track traversing uninhabited land and the routecovers a total length of approximately 24.477 Km.

3.0 Traffic Surveys and Forecasts

A manual traffic survey was carried out along Fort-Portal Bundibugyo - Lamia roadbetween 6th Dec, 2006 and 12th Dec, 2006. A twenty four (24) hour count was done fortwo days; one on a weekend night, and the other on a neutral week day (Thursday).Average Daily Traffic (ADT) was computed and Average Annual Daily Traffic (AADT)was derived. The calculation adopted a seasonal conversion factor of 1.0 assumingthat ADT approximately represents the AADT. The total combined AADT wasestablished to be 244.

The following traffic forecast rates were agreed upon with the Client (RAFU) to beadopted for the Fortportal-Bundibugyo-Lamia upgrading project for a design period of


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20 years. i.e. 7.5% - 0-7yrs, 6.5% - 7-15yrs and 5.0% - 15-20yrs and were adopted forthis design.

4.0 Topographic Survey

A topographical survey was carried out. One hundred sixty three (163) survey controls

were established. See Annex 2

5.0 Drainage and Hydrological Investigations

New forty eight (48) cross drainage culverts (including box culverts) have beenidentified. In accordance with the guidelines of the Road Design Manual, the 25 yearsreturn period is the recommended design period for fixing culvert sizes. TRRL EastAfrican Flood model was used to estimate the design discharge of the culverts.

6.0 Pavement Design

The pavement has been designed according to TRL Overseas Road Note 31. The designhas also been checked by alternative methods of pavement design, namely.

Uganda Road Design Manual (1994 and Road Safety Revision-2004), and

Kenya Road Design Manual Part III 1981.

The design ESA was established to be 1.729 Million.

The tables below shows the design CBR values adopted and the resulting pavementthicknesses for the respective sections.

Design CBR adopted

Section Design strength (CBR %)Km 34+800 - 40+800 5Km 40+800 - 43+800 10Km 43+800 - 47+300 5Km 47+300 - 59+275 8

Recommended Pavement Structure

Pavement Layer Thickness (mm)

Road-base: Graded Crushed Stone 150

Sub-base: Lime Stabilized Gravel 175

Improved Sub-grade 150


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Summary of Recommended Pavement Design

Road Section Km KmPavement

layers34+800-40+800 40+800-43+800 43+800-47+300 47+300-59+275

Surf acing:

Carriage way DBST DBST DBST DBST

Shoulders SSD SSD SSD SSD

Pavement :

CrushedStone Base

150 150 150 150

LimeStabilisedSubbase

175 175 175 175

ImprovedSubgrade

150 150 150 150

7.0 Geomet r ic Design

The geometric design has been carried out using Micropiste road software. The designwas based on geometric design standards contained in Ugandan Road Design Manual(RDM), 1994. Other design standards like AASHTOsA policy on Geometric DesignStandards of Highway and Streets 2001 edition and TRRL Road Note 31 have alsobeen taken into consideration while formulating the design criteria. The terrain of theroad is generally mountainous.

Various design speeds were adopted since the terrain varied from mountainous torolling. Table below shows the various speeds adopted for the respective sections.

Design Speed

Design Speed

Km/phRoad Section

Length of RoadSection Km

% of TotalLength

Remarks

60 34+800-45+500 10.7 45.1 Terrain ismountainous

80 45+500-59+275 13.775 54.9 Terrain is gentlyrolling

The horizontal alignment has been designed to follow the existing track alignment tothe extent possible without compromising on design standards. Various bus stops have


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been provided for around commercial centres as well as schools. The width of thecarriage way is 6.0m and 1.5m for each of the shoulders. The table below shows thecriteria adopted in the design of the horizontal alignment curves.

Horizontal Alignment Criteria

Minimum Radiusor Max Super elevation of 7%DesignSpeed

Km/hr Absolute Minimum, mm Desirable, mm

Minimum Radiuswith normalcamber, mm

60 125 165 1200

70 180 225 1500

80 240 310 2000

Considering the design speeds of 60-80 kmph and the fact that the terrain ismountainous, a maximum gradient of 10% has been adopted. The table summariesthe stopping sight distances and the K-values for crest and sag locations.

Stopping Sight Distances and K-values

Uganda RDMDesign speed

Kmph SSD, m K -Crest K - Sag

60 80 16-17 16-24

70 95-110 20-30 20-30

80 115-140 35-45 25-40

The table below shows the criteria adopted in the design of the horizontal alignmentcurves.

Vertical Alignment Criteria

K Value for Stopping SightDistance

Crest Sag

MinimumLength ofcurve (m)

Maximum GradientDesign

Speed

Km/hrMin. Des. Min. Des. Min Des. Flat Rolling Mount.

60 16 17 16 24 45 120 4(6) 6(8) 8(10)

70 20 30 20 30 50 140 4 (6) 6 (8) 7 (9)

80 35 45 25 40 60 160 3 (5) 5 (7) 7 (9)

8.0 Tr af f i c Saf ety and Road Furni t ure

Contained in this chapter in the report is design for; road markings, speed limitationsigns, overtaking prohibition signs, and safety barriers at embankment high fillsections, sharp bends and at water crossings.


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9.0 Unit Rat es and Cost Est i mat es

The Unit rates are based on the assumption that the contract for the work will beawarded by end of 2008 adopting the International Competitive Bidding method andhighly experienced and well equipped contractors will undertake the work.

In deriving the Consultant has considered a Contractors Mark Up of 44% distributed asfollows: profit 10%; Overheads 15%; Nature of Terrain 14%; and Remoteness 5%.

The rate per kilometre of construction Itojo-Sempaya road (24.477Km) is estimated atUS$ 1,008,441/=. The total earthwork quantities are summarized in the table below.

Summary of Earth Work Quantities

Road Section Volume Cut(m3)

Volume Fill(m3)

km 34+800 to Km 59+275 669,472 367,573

Grand Total 669,472 367,573

Detailed quantity breakdown per kilometre is attached in Annex 3.


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TABLE OF CONTENTS

EXECUTIVE SUMMARY ...................................................................................................................i

1.0 INTRODUCTION.................................................................................................................11.1 Background.........................................................................................................................1

1.2 Objectives ...........................................................................................................................1

1.3 Scope of Consultancy Services............................................................................................2

1.4 Project Road.......................................................................................................................2

1.5 Organization of the Report ................................................................................................31.5.1 Purpose of this Report ............................................................................................................ 31.5.2 Contents of this Report .......................................................................................................... 3

2.0 SURVEYS AND INVESTIGATIONS .......................................................................................5

2.1 Background.........................................................................................................................5

2.2 Traverse observations ........................................................................................................5

2.3 Spirit Leveling. ...................................................................................................................5

2.4 Traverse Adjustment ..........................................................................................................5

2.5 Topographical Surveys and DTM Creation .......................................................................... 5

2.6 List of Permanent /Reference Marks .................................................................................6

3.0 TRAFFIC SURVEY AND FORECAST....................................................................................7

3.1 Background.........................................................................................................................7

3.2 Normal Daily Traffic...........................................................................................................7

3.3 Adjustment Factors ............................................................................................................73.3.1 Night Expansion Factor........................................................................................................... 73.3.2 Seasonal Factors...................................................................................................................... 8

3.4 Diverted Daily Traffic.........................................................................................................8

3.5 Generated Daily Traffic .....................................................................................................9

3.6 Combined Average Daily Traffic ........................................................................................9

3.7 Average Annual Daily Traffic (AADT)............................................................................... 10

3.8 Traffic Growth and Traffic Growth Forecasts .................................................................10

3.9 Average Daily Traffic in Equivalent Standard Axles ........................................................11

3.10 Cumulative Equivalent Standard Axles, or Design Traffic...............................................11

4.0 DRAINAGE INVESTIGATION AND HYDROLOGICAL ANALYSIS.........................................13

4.1 Background.......................................................................................................................13


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4.2 Hydrological Study............................................................................................................14

4.3 Catchment Delineation.....................................................................................................14

4.4 Culvert Sizing and Assessment of Hydraulic Capacity.....................................................16

4.5 Design Flow Volumes ........................................................................................................16

5.0 SOILS AND CONSTRUCTION MATERIALS INVESTIGATIONS............................................19

5.1 Background.......................................................................................................................19

5.2 Geology and Soils..............................................................................................................19

5.3 Climate .............................................................................................................................22

5.4 Existing Conditions along the Proposed Alignment.......................................................... 22

5.5 Site Investigations ............................................................................................................225.4.1 Subgrade Soils ....................................................................................................................... 225.4.2 Construction materials ......................................................................................................... 23

5.5 Laboratory Testing ...........................................................................................................24

5.5.1 Test Results for Subgrade soils............................................................................................. 255.5.2 Test Results for Granular Materials ..................................................................................... 265.5.3 Test Results for Sand and Rock............................................................................................. 26

5.6 Construction Strategies....................................................................................................265.6.1 General.................................................................................................................................. 265.6.2 Modification of Clayey Gravels............................................................................................. 27

6.0 PAVEMENT DESIGN .........................................................................................................28

6.1 General .............................................................................................................................28

6.2 Design Approach ...............................................................................................................286.2.1 Calculation of Design Traffic................................................................................................ 28

6.2.2 Assessment of Climate Conditions ....................................................................................... 286.2.3 Assessment of Design Strength of Subgrade ........................................................................ 286.2.4 Availability of Construction Materials ................................................................................. 296.2.5 Selection of Alternative Pavement Structures .................................................................... 30

6.3 Design of Layer Thicknesses- Alternative 1 .....................................................................316.3.1 Road Note 31-Design Method................................................................................................ 316.3.2 Uganda Road Design Manual - Design Method...................................................................... 326.3.3 Kenya Road Design Manual Design Method........................................................................ 34

6.4 Design of Layer Thicknesses Alternative 2 ....................................................................356.4.1 Evaluation of Layer Thicknesses........................................................................................... 356.4.2 Surface Dressing Design ........................................................................................................ 366.4.3 Recommended Pavement Design .......................................................................................... 38

7.0 GEOMETRIC DESIGN .............................................................................................................40

7.1 General .............................................................................................................................40

7.2 Design Criteria.................................................................................................................. 407.2.1 Terrain Classification............................................................................................................ 407.2.2 Classification of Road........................................................................................................... 40


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7.2.3 Design Speed......................................................................................................................... 41

7.3 Horizontal Alignment .......................................................................................................41

7.4 Vertical Alignment .......................................................................................................43

7.5 Climbing Lanes .................................................................................................................44

8.0 TRAFFIC SAFETY AND ROAD FURNITURE ......................................................................46

8.1 General .............................................................................................................................46

8.2 Horizontal signaling..........................................................................................................468.2.1 Description and use............................................................................................................... 46

8.3 Vertical signaling..............................................................................................................478.3.1 Description and sizes ............................................................................................................ 47

8.4 Limits and prohibitions ....................................................................................................478.4.1 Speed limitation.................................................................................................................... 478.4.2 Road Signs.............................................................................................................................. 50The following road signs have been envisaged. ................................................................................ 50

8.4.3 Overtaking prohibition ......................................................................................................... 51

8.5 Traffic guidance equipment............................................................................................. 518.5.1 General.................................................................................................................................. 518.5.2 Projected elements and placing criteria.............................................................................. 51

8.6 Safety Barriers.................................................................................................................. 52

9.0 UNIT RATES AND COST ESTIMATES ...............................................................................54

9.1 Unit Rates .........................................................................................................................54

9.2 Taxes................................................................................................................................. 54

9.3 Quantities .........................................................................................................................55

9.4 Other items ......................................................................................................................55


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LIST OF TABLESPgNo.

Table 3.1 Summary of manual traffic counts, December 2006............... 7

Table 3.2 Night traffic counts, December 2006 8Table 3.3 Average normal daily traffic 8

Table 3.4 Diverted traffic from Karugutu-Ntoroko. 9

Table 3.5 Generated traffic. 9

Table 3.6 Combined average daily traffic............... 10

Table 3.7 GDP growth, demand ratios & vehicle fleet forecast (2005-20017). 10

Table 3.8 Equivalent Standard Axles, ESA. 11

Table 3.9 Design traffic 12

Table 4.1 Head water/ depth ratio. 16

Table 4.2 Summary of flow regimes and schedule of culverts. 16

Table 4.3 Exit Velocities of Culverts. 17

Table 4.4 Summary of proposed culvert sizes vs design peak discharge 17

Table 6.1 Design Strength for Subgrade Soils. 29

Table 6.2 Summary of layer thickness alternative 1. 34

Table 6.3 Summary of layer thicknesses alternative 2 35

Table 6.4 Resulting pavement thicknesses 36

Table 6.5 Condition factors.................... 36

Table 6.6 Summary of Surface Dressing Rates 38

Table 6.7 Summary of recommended pavement design. 38

Table 7.1 Design of parameters as per RDM. 40

Table 7.2 Design speed. 41

Table 7.3 Horizontal alignment criteria. 41

Table 7.4 Super elevation & minimum lengths of transition. 42

Table 7.5 Stopping sight distances and K-values. 44

Table 7.6 Vertical alignment criteria 44


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Table 8.1 Guardrail locations 52

Table 9.1 Summary of earth work quantities. 55

LIST OF FIGURES

Figure 1.1 Location map 3

Figure 4.1 Layout of proposed alternative route. 13

Figure 4.2 Catchment delineation of major tributaries for Itojo to Sempaya. 15

Figure 5.1 Soils map....................... 20

Figure 5.2 Geology map 21

LIST OF ANNEXES

Annex 1 Terms of Reference

Annex 2 List of Survey Controls

Annex 3 Manual Traffic Counts

Annex 4 Hydrological Calculations

Annex 5 Earthworks Quantities

Annex 6 Setting out Data (Horizontal and Vertical)


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LIST OF ABBREVIATIONS

AASHTO American Association of State Highway Transportation Officials

BS British Standard

TRL Transport Research Laboratory, UKESA Equivalent Standard Axles

SN Structural Number

DSN Design Structural Number

ADT Average Daily Traffic

AADT Average Annual Daily Traffic

DT Design Traffic

CBR California Bearing Ratio

MDD Maximum Dry DensityPI Plasticity Index

SSD Single Surface Dressing

DSD Double Surface Dressing

ALD Average Least Dimension

URDM Uganda Road Design Manual

ORN31 Overseas Road Note 31

KRDM81 Kenya Road Design Manual 1981

TP Trial PitsLL Liquid Limit

PL Plastic Limit

PI Plastic Index

LS Linear Shrinkage

PM Plasticity Modules

GM Grading Modules

OMC Optimum Moisture Content

LHS Left Hand SideRHS Right Hand Side


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1.0 INTRODUCTION

1.1 Background

The Government of Ugandas medium term transport sector policy aims at promotingefficient and effective transport services as a means of providing effective support toincreased agricultural and industrial production, trade, social and administrativeservices. This strategy is aimed at ensuring an efficient transport sector that will playa critical role in the development of an integrated and self-sustaining economy whichwill result in the eradication of poverty, economic integration of the country andenhancement of regional integration.

As part of the above objectives, Government in 2006, engaged M/s Tecnica yProyectos S.A. (TYPSA) of Spain in association with M/S Project Management andEngineering ( PROME) Consultants Ltd of Uganda to undertake a review of the originalfeasibility study and detailed engineering design prepared by M/s Sabbour Associatesin association with Mott MacDonald and Serefaco Consultants LTD in 1996 and carry outa detailed engineering design for upgrading of the Fort Portal Bundibugyo Lamiaroad to bituminous standards. The road is expected to form an international cross-border link between Uganda and the Democratic Republic of Congo (DRC) and beyondthus fostering regional integration as well as enhancing economic development

However, following the initial route selection and the associated geotechnicalinvestigations, it was established that the existing route between Itojo and Sempayacomprises several sharp bends that cannot accommodate articulated trucks. Thisparticular section has always experienced land slides due to the nature of the terrainthus resulting in frequent road closures. These bottlenecks undermine Governmentsdesire to transform the existing road into an international transit route. As aconsequence of this, Government engaged M/s TYPSA in association with M/S PROMEConsultants Ltd to carry-out a desktop study with the objective of investigating theeconomic, environmental and engineering feasibility of a possible deviation from theexisting road between Kichwamba and Karugutu and between Sempaya and Itojo. Thedesktop study established that with regard to Kichwamba Karugutu, the existingalignment should be retained because all other possible options are either expensiveor not technically feasible. Regarding the Itojo Sempaya section, a possible routefrom Itojo traversing through Kibuku, Rwamabale and Burondo trading centres andconnecting with the main Fort Portal Bundibugyo Lamia road at Sempaya close tothe Semliki hot springs was established through a reconnaissance survey. Thealternative route referred to as Alternative 2A in the desktop study report, isapproximately 24.477 Km while the existing route is 13.82 Km.

In light of the above, Ministry of Works and Transport (MoWT) represented by RoadAgency Formation Unit (RAFU), engaged M/S PROME Consultants Ltd to carry out adetailed engineering design for the above Itojo-Sempaya Road (Alternative 2A).

1.2 Object ives

The main objectives of the assignment are as outlined below:


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i) To review the desktop study report prepared by M/s TYPSA in July 2007 toobtain further information on the major features located along the possiblealternative route.

ii) To carry out the necessary field surveys in order to establish the road

alignment and determine the accurate centerline;iii) To prepare a detailed engineering design of a class II bitumen road as well as

confidential cost estimates and tender documents suitable for internationalcompetitive bidding.

It should be noted that design of Itojo-Sempaya road section on approval shall beincorporated into the main design of the Fort Portal Bundibugyo Lamia road designprepared by M/s TYPSA in association with PROME Consultants Ltd by replacing theexisting Itojo Sempaya road link, thus forming the final design of the entire roadproject. Detailed terms of reference are herewith attached in Annex 1.

1.3 Scope of Consult ancy Serv ices

The scope of the consultancy assignment includes but not limited to the following;

i) Establish and fix traverse stations (beacons) along the entire road section at2km apart with orientation beacons that must be visible from the traversestations and at approximately 200m from each traverse stations fully securedand protected,

ii) Perform a detailed topographical survey along the proposed alignment,iii) Carryout the following engineering investigations,

a) Soils and construction material investigations,b) Hydrological investigations,

iv) Carryout a detailed engineering design for the following;a) Geometric Highway Design,b) Pavement/ Structural Design,c) Structural Design for Bridges and Drainage Structures,d) Road Safety Audit,e) Road Furniture, and

v) Produce design drawings for the following;a) Plan and Profile of the Proposed Alignment,b) Typical Cross-sections,c) Typical Culvert Drawings,d) Bridge Structure Details,e) Soils Plan, and

f) Ancillary Worksvi) Preparation of the Bills of Quantities and Cost Estimate

1.4 Proj ect Road

The possible deviation diverges from the existing road near a military post at about Km34 + 800 (Itojo trading centre) from Fort Portal and descends towards a low-lying areawhich extends towards River Semliki and further on to Lake Albert the route traverses


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through Kibuku, Rwamabale and Burondo trading centres and joins the Rwebisengo toSempaya road before continuing to Sempaya. This existing Rwebisengo to Sempayaroad is an earth road with an approximate width of 4.5 m while the section from Itojois mostly an existing earth track traversing uninhabited land and the route covers atotal length of approximately 24.477 Km.

Figure 1.1: Location Map

1.5 Organizat ion of t he Repor t

1.5. 1 Purpose of thi s Report

This report is aimed at giving a detailed analysis, description and documentation of allthe design aspects for the upgrading of Itojo-Sempaya Road (Alternative 2A).

1.5. 2 Cont ents of t his Report

The report comprises the following documents:

Document 1: Detailed Engineering Report

The detailed engineering report comprises the following volumes;

Volume I Main Engineering Report comprising the following:Executive Summary

Chapter 1 Introduction

Chapter 2 Surveys and Investigations

Chapter 3 Traffic Surveys and Forecast


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Chapter 4 Drainage and Hydrological Investigations

Chapter 5 Soils and Construction Materials Investigations

Chapter 6 Pavement Design

Chapter 7 Geometric DesignChapter 8 Traffic Safety and Road Furniture

Cahpter 9 Cost Estimates

Volume II Engineering Drawings (A3 Size)

Volume III Confidential Cost Estimate

Volume IV Soils and Materials Report

Document 2: Tender Documents

The International Bidding Documents are also enclosed with the Design Report. Various

sections of bidding documents are compiled in four volumes (excluding the soils &materials report) as hereunder.Volume I

Section I: Invitation of Bids

Volume IISection II Instructions to Bidders (ITB)

Section III Bidding Data and Qualification Information

Volume III

Section IV General Conditions of Contract

Section V Conditions of Particular Application (COPA)

Volume IV

Section VI Technical Specifications

Section VII Form of Bid, Appendix to Bid and Bid Security, Form of Bid, Appendix toBid, Form of Bid Security (Bank Guarantee)

Section VIII Bill of Quantities

Section IX Form of Agreement, Forms of Performance Security and Bank guarantee

for Advance PaymentSection X Annexures

Annexure A: Locality Map

Annexure B: Notice Board

Section XI Drawings


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2.0 SURVEYS AND INVESTIGATIONS

2.1 Background

The Terms of Reference (ToR), require the Consultant to establish traverse stationstogether with orientation, establish X, Y, and Z coordinates related to the NationalSurvey Grid and tie them into the control survey for the remainder of the project(Fortportal-Bundibugyo-Lamia), carry out a detailed topographic survey of the roadright of way, selected alignment, cross-sections and develop a Digital Terrain Model(DTM).

The survey exercise involved; Traverse observations and adjustment to determinehorizontal control and spirit leveling to determine heights of controls above mean sealevel and afterwards , topographical surveys were carried out to generate the DigitalTerrain Model.

2.2 Tr averse observat ions

The traverse opened from an old GPS FB07 at Itojo, where the alternative route leavesthe existing road with orientations to G01 and F31 all being old controls and closed onFB10 with orientation to I44 at Sempaya where it joins again the existing road(Fortportal Bundibugyo road). The traverse stations were observed using a Sokkiatotal station. The method of forced centering was employed per station. At everytraverse station two zeros and two rounds were being emphasized. Both angular andlinear observations conformed to international standards.

2.3 Spir i t Level i ng.

The method of two way leveling was employed on all traverse stations. The relativeheights between stations were accepted so long as the difference between the two

runs did not exceed 3mm. The mean between the two runs was accepted as the truedifference in height between the two stations. All heights along this route werereferenced to FB07 at Itojo and closed to FB10 at Sempaya with misclosures below10mm. Leveling computations were always being done in the field in order to avoidunnecessary occurring errors.

2.4 Tr averse Adj ust ment

Traverse adjustment was carried out using the software that employs LSA by variationof coordinates. The intermediate traverse stations did not have the orientations; assuch, the traverses were computed using ray trace method to compute both linear andangular mis-closures. Both angular and linear misclosures conformed to internationalstandards.

2.5 Top ographi cal Survey s and DTM Cr eat ion

Longitudinal section profile was observed for points every 25m along the centerline.However, this interval reduced to 12.5m or less depending on the terrain. For examplesome curves were being observed at 6.25m. All features were being coded e.g. cl for


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centerline and RE for road edge, etc. Using a self recording total station all data werebeing captured automatically and downloaded into the PC, in a CSV format compatiblewith most of the design software. Transversely, the data was being captured in therange of 60m to 200m wide. For example, from Itojo the first one and half km, theband was 200m.

The data was processed using various in-house software which include Autocad LandDevelopment, MX road and Micropiste. The data was organized in layers and finally theDTM was processed.

2.6 List of Permanent /Reference Marks

The list which contains 163 survey controls is organized in such a way that it gives thepoint number, Eastings, Northings, Height and description that gives the location interms of a chainage and side of the road where it is located (RHS or LHS). See Annex 2


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3.0 TRAFFIC SURVEY AND FORECAST

3.1 Background

A traffic survey was carried out along Fort-Portal Bundibugyo - Lamia road between6th Dec, 2006 and 12th Dec, 2006. A twenty four (24) hour count was done for two days;one on a weekend night, and the other on a neutral week day (Thursday). Three linkswere considered i.e. from Fort-Portal to Karugutu, Karugutu to Bundibugyo andBundibugyo to Lamia (a town near the Congo-Uganda border). Along the identifiedthree (3) road links, suitable traffic sections were chosen to act as vintage points andthey include; Fort-Portal Karugutu, Karugutu Bundibugyo and Bundibugyo Lamia.The Consultant has assumed the traffic between Karugutu and Bundibugyo to be thetraffic that shall plyi the Itojo-Sempaya alternative route.

3.2 Normal Da i l y Tr a f f i c

Considering the Itojo-Sempaya road section, and for the purpose of this design, the

Consultant has considered the traffic between Karugutu and Bundibugyo to be thedesign traffic since all this traffic shall be diverted on this alternative route.

Table 3.1: Summary of Manual Traffic Counts, December 2006Link: Karugutu-BundibugyoVehicle TypeTotal ADT Percent

Cars 3 1.00%Pick-ups, 4WDs 71 24.23%Mini-Buses 18 6.29%Medium Buses 2 0.70%Buses 2 0.70%Light Trucks 8 2.80%

Medium Trucks 11 3.85%Artic/ Draw Bar Trailers 1 0.35%Motorcycles 86 30.07%Bicycles 84 29.37%Daily Traffic December 2006 286 100.00%

Note: Details of the manual traffic counts carried out between the dates of 6th December,2006 and 12th December, 2006 are contained in an annex 3 to this report.

3.3 Adj ust ment Fact ors

3.3. 1 Night Expa nsion Factor

Two night counts were carried out on 7/12/06 & 10/12/06 to establish a NightExpansion Factor (NEF).


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Table 3.2 Night Traffic Counts, December 2006Date

Link: Karugutu-Bundibugyo7/12/06 12/12/06

24 Hour Day Count (A) 309 27912 Hour Day Count (B) 256 244Night Expansion Factor (NEF=A/B) 1.21 1.14Average NEF 1.175

Using the NEF obtained from table 3.2 above, the 5 day-12 hour counts wereconverted to 24-hour counts as shown in the table below;

Table 3.3: Average Normal Daily Traffic, December 2006Link: Karugutu-BundibugyoVehicle TypeTotal ADT Percent

CompositionCars 4 1.19%

Pick-ups, 4WDs 83 24.78%Mini-Buses 21 6.27%Medium Buses 2 0.60%Buses 2 0.60%Light Trucks 10 2.99%Medium Trucks 13 3.88%Artic/ Draw Bar Trailers 1 0.30%Motorcycles 101 30.15%Bicycles 98 29.25%Daily Traffic December 2006 335 100.00%

3.3. 2 Seasonal Fact ors

Due to the unavailability of consistent historic annual daily traffic counts, it was notpossible to adopt seasonal factors to compute Annual Average Daily Traffic. We havetherefore adopted a seasonal conversion factor of 1.0 assuming that the above ADTapproximately represents the AADT using the road.

3.4 Diver t ed Da i l y Tr a f f i c

The road link that presents a possibility of traffic changing route is Karugutu-Ntorokoroad. This road acts as an access to the Democratic Republic of Congo through theborder town of Ntoroko along the shores of L. Albert. An O-D survey was carried out.Basing on the Normal Traffic Count, the total number of vehicles (bicycles &motorcycles exclusive) that used this road on this day was 74 (excluding motorcycles &

bicycles). This equaled the number of vehicles (excluding bicycles & motorcycles)interviewed during the O-D survey. The Consultant was also able to categorize thetraffic in relation to the purpose of the journey into; Business, Tourist and Local.


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February 2008 - 9 -

Table 3.4: Diverted Traffic from Karugutu-NtorokoDiverted Traffic CountsVehicle TypeBusiness Tourist Local

Cars 8 0 0Pick-ups, 4WDs 30 12 0Mini-Buses 7 3 0Medium Buses 2 1 0Buses 0 0 0Light Trucks 6 0 0Medium Trucks 3 1 0Artic/ Draw Bar Trailers 1 0 0Motorcycles 86 0 28Bicycles 25 0 91Daily Diverted Traffic December 2006

168 17 119

Diverted traffic is assessed in terms of the advantages associated with the diversion,i.e. time and other cost savings related to taking up the diversion as opposed to theother alternative route.

The Diverted Traffic was computed as the sum of the traffic in the business and touristcategory because all this traffic will prefer the project road upon completion. This isbecause most vehicle operators will experience a lower cost in vehicle maintenancewhen they use the project road, in comparison to using the Karugutu Ntoroko as anaccess to Congo. Hence Diverted traffic = 74 vehicles (excluding motorcycles &bicycles).

3.5 Generat ed Dai ly Tr af f ic

For purposes of this design, it was agreed with the Client (RAFU) to adopt a factor of25% to establish the generated traffic for all classes of vehicles.

Table 3.5: Generated Traffic during the 1st Year after ConstructionVehicle Type Normal Traffic Generated Traffic

Light Vehicles 87 22Mini & Medium Buses 25 6Light & Medium Trucks 23 6Artic/ Draw Bar Trailers 1 0

3.6 Combined Average Dai ly Tr af f ic

The combined average daily traffic becomes the sum of Normal traffic, Divertedtraffic, and Generated traffic.


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February 2008 - 10 -

Table 3.6: Combined Average Daily Traffic during the 1st Year afterConstruction

Link Name Normal ADT DivertedADT

GeneratedADT

CombinedADT

Karugutu-Bundibugyo 136 74 34 244

3.7 Aver age Annual Dai l y Tr af f ic (AADT)

As explained in section 3.3.2, the Consultant has adopted the Average Daily Traffic(ADT) to be the Average Annual Daily Traffic (AADT) to be used for design purposes.Therefore the total AADT is 244 Vehicles.

3.8 Tr a f f i c Growt h and Tr a f f i c Growt h Forecast s

From 1989 to 2002 the countrys GDP grew by an average of 6.3 percent per annum. Inthe same period the 4-wheel vehicle fleet (i.e., excluding motorcycles) grew by anaverage 13.1 percent per year; again quite remarkable, but also from a very low base only just over 27,000 registered vehicles in 1989. The implied elasticity ratio - of

vehicle ownership with respect to total GDP - was thus 2.08, being fairly typical ofcountries at early stages of motorization growth. From 1989-2002 the motorcycle parkincreased by more than 24 percent per year to a total of over 71,000 units, just overone-third of all registered motor vehicles. The implied demand elasticity (1989-2002)for motorcycles was 3.84 - however it is unlikely that such rapid growth will besustained for much longer in the future. Considering only the period 1995-2002, thegrowth rate for motorcycles was 18.3 percent, for average GDP growth of 6.0 percent,giving a rather lower elasticity, of 3.05. Demand elasticity ratios for all vehicle typescan be expected to decline as the motorized fleet grows, in common with theexperience in many other countries. The estimated demand elasticities (E) for theperiod 2005-2017 are 1.33 for trucks and 1.45 for all other 4-wheel vehicles buses,minibuses, pickups, and cars, being some ten percent lower than the estimated

elasticities in the 1995-2002 period.Table 3.7 below gives the growth rates for trucks and other vehicles, and the implieddemand ratios for 1989-94 and 1995-2002. Based on the previous traffic growth rates,together with the growth rates of the motor fleet for 2005-2017.

Table 3.7: GDP Growth, Demand Ratios and Vehicle Fleet forecast

GDP growth TrucksOther 4-wheel

vehiclesPeriod

(% p.a.) Growth E Growth E

2005-17 standard forecast 5.50% 7.32% 1.33 7.98% 1.45

2005-17 lower GDP 4.13% 5.49% 1.33 5.98% 1.45

In light of the above, we haveadopted the following traffic growth rates for the Itojo-Sempaya upgrading project for a design period of 20 years. i.e. 7.5% - 0-7yrs, 6.5% -


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7-15yrs and 5.0% - 15-20yrs. These were the same growth factors that had beenestablished and agreed to by the Client for the Fortportal-Bundibugyo-Lamia road.

3.9 Average Dai ly Tr af f ic in Equivalent St andard Axles

Based on the Average Annual Daily Traffic and the Equivalency Factors, the EquivalentStandard Axles (ESA) have been established and presented in the table 3.8 below.

The Average Daily Traffic in ESA, Td is computed from the formula below

1

n

i i

i

V C

=

Where V Traffic volume for each Vehicle Type and C Equivalent axle load factor.

Note: the contribution to the axle loading from private cars and light goods vehicleshas been ignored since these do not cause a significant loading on to the pavement.

Table 3.8: Equivalent Standard Axles

Vehicle TypeNumber ofVehicles, AADT

Equivalent AxleLoad Factor, C

EquivalentStandard Axles(ESA)

Cars 13 - -Pick-ups, 4WDs 144 - -Mini-Buses 36 - -Medium Buses 6 - -Buses 3 3.0 9.0Light Trucks (


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[ ]

100

1100

1

365r

r

TD

N

dT

+=

Source: U-RDM94

WhereDT = Design traffic as cumulative number of 80 kN ESATd = Average daily number of ESA in the first year after openingr = Average growth rate for the design period in percent per annum

N = Design period in years

Table 3.9: Design Traffic in 80kN ESAPeriod Time,Yrs Traffic Growth

Rate, %Design Traffic(80kN ESA)

2006 2013 (A) 7 7.5 368,4332013 2021 (B) 8 6.5 713,542

2021 2026 (C) 5 5.0 647,4102006 2026 (A+B+C) 20 - 1,729,385


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4.0 DRAINAGE INVESTIGATION AND HYDROLOGICAL ANALYSIS

4.1 Background

The Terms of Reference (ToR), require the Consultant to carry out a hydrologicalanalysis on the area affecting the road; determine for each drainage structurecatchment areas, run-off factors and design discharge flows; analyze all existing dataand results of field investigations for soils, foundations and hydrology.

Figure 4.1: Layout of proposed alternative route Itojo to Sempaya

Km43+800

Km47+800km 48+800

Km54+800

Km34+800

RIVER SEMPAYA

SEMPAYA

BURONDO

RWAMABALE

KIBUKU

TO BUNDIBUGYO

Km59+000

FORTPORTAL-BUNDIBUGYO RD

ITOJO-SEMPAYA (ALTERNATIVE ROUTE) 24.47KM

FROM FORTPORTAL


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4.2 Hydrol ogical St udy

The preliminary hydrological analysis for the proposed route alignment, Itojo toSempaya was performed using the TRRL East African Flood Model. Briefly summarisedin the following steps.

Establish the drainage area, land slope and catchments slope.

From site inspection establish catchments type and hence lag time as tabulatedunder table 7 of Fiddes (1976).

Determine soil type as determined by geo-technical investigations and with landslope estimate the standard contributing area coefficient (Cs) in table 4 of Fiddes(1975).

Check in Table 3 of Fiddes (1976) to determine whether zone is wet, dry or semiarid and estimated catchments wetness factor (Cw) from Table 5 of Fiddes (1976).

From site inspection reports, deduce vegetation cover, paying particular attention

to areas close to the stream and use table 6 of Fiddes (1976) to estimate the landuse factor (CL).

Set up the methodology for determining the design peak flow in a spreadsheet anduse the same to compute the 25 year recurrence flood flow for each of theselected streams.

The Original Design obtained an anticipated 25-Year Storm Of 79mm per day at FortPortal and applied a Weighted Average Design Rainfall Depth of 107.6 mm/day. Theirresults are within the range of our findings but are slightly below the RecommendedDesign Value of 122 mm for the 25-year Design Rainfall Recommended by the TRRLFlood Model which has been assumed in this Analysis. This Intensity of 122mm for the25 Year Return Period was considered conservative and adopted for Further Design.

In light of the above, and taking into consideration the guidelines set by the UgandaRoad Design Manual 94, the following return periods were selected:

Small Culverts with catchment areas less than 0.1 km2 10 yearsLarge Culverts 25 years

For details of hydrological calculations see attachment to this report. Also attached isthe hydrological analysis of selected culverts sizes.

4.3 Cat chment Del ineat ion

Catchment areas at each location for which a cross drainage structure is required were

determined using topographical maps of 1: 50 000 scale; supplemented with fieldinvestigations that were conducted along the proposed alternative route. From theabove exercise, 48No. points along the alignment were identified as requiring crossdrainage structures. The catchment areas for the 48No. drainage crossings werecomputed from hydrological maps. Figure 4.2 overleaf shows the delineation of thecatchment areas used for detailed hydrological analysis.


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Figure 4.2: Catchment Delineation of Major Tributaries Itojo to Sempaya


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4.4 Culvert Sizi ng and Assessment of Hydra ul ic Capacit y

Culverts were sized with the assumption that the controlling flow type will be inletcontrol, i.e. the culvert is flowing part full, with critical depth at inlet. When aculvert operates under inlet control, the roughness and length of the culvert andoutlet condition (including tail water) do not affect hydraulic performance. Headwaterdepth and the inlet edge configuration determine the culvert capacity with the barrelusually flowing only partially full. Whereas it is accepted that the barrel slope has onlya minor, negligible effect on the culvert capacity, this flow condition has been testedwith robust culvert analysis software for a range of discharges and found to beacceptable.

In general, a headwater / depth ratio of between 1 and 1.3 has been optimized byanalysis software, the worksheets of which are attached, also summarized in the tablebelow. These ratios take into account the depth of road pavement layers to finallevel.

Table 4.1: Head water/ depth ratioCulvert Size Optimized Head Water Ratio

Armco 900 1.3

Armco 1200 1

BC 1500 x 1500 1.4

Table 4.2 below gives the Summary of Culvert Sizes derived from Hydraulic CapacityAssessment for the range of Q25 Design Peak Flow Volumes. From the hydraulicassessment of typical culverts sizes for the derived flow regimes, it can be noted thatthe smallest size of culvert that can be installed has a discharge capacity of 0.5m3/s.

Table 4.2: Summary of Proposed Culvert sizes vs. Design Peak DischargeDesign Peak Flow Proposed Culvert Size (mm)

0.5 CP 600

1.0 2No CP 600 or 1No 900 Armco

2.0 2No 900 Armco

3.0 2No 1200 Armco

6.0 3 No 1200 Armco

7.0 2No BC 1500 x 1500

8.0 3No BC 1500 x 1500

4.5 Design Flow Volumes

All analyzed culverts are assumed to flow full at ultimate capacity. Therefore outletworks for all culverts in the list of remedial actions were proposed. Exit velocities forthe various culvert sizes range from 1.7 to 4.7m/s which all require downstream scour


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protection works. The table below summarizes the analyzed exit velocities, which arealso indicated in the attached worksheet calculations, Culvert Calculator Report

Table 4.3: Exit Velocities of Culverts

Culvert Size Exit Velocity (m/s)Armco 900 2.0Armco 1200 1.3BC 1500 x 1500 4.7

Results of the hydrological analysis are summarized in Table 4.1 below. The Q25 designflow volume is shown against corresponding chainages. From results of theHydrological Analysis; the following trends in the Flow Regimes can be observed assummarized in Table 4.2 below.

Table 4.4: Summary of Flow Regimes and Schedule of Culverts

Peak Discharge Q25,m3/sCatchmentNumber

ChainageActual

RoundedOff

CulvertType

CulvertSize

1 34+950 2.2 2.0 MPC 2x(900)

2 35+275 0.9 1.0 MPC 1x(900)

3 35+532 8.1 8.0 BOX 3x(1.5x1.5)

4 35+575 1.9 2.0 MPC 2x(900)

5 36+363 1.8 2.0 CPC 2x(900)

6 36+525 2.4 2.0 CPC 2x(900)

7 37+075 2.1 2.0 CPC 2x(900)

8 37+325 2.4 2.0 CPC 2x(900)

9 37+875 1.4 1.0 CPC 1x(900)

10 38+400 1.0 1.0 CPC 1x(900)

11 38+200 6.5 7.0 BOX 2x(1.5x1.5)

12 39+675 1.8 2.0 CPC 2x(900)

13 39+975 1.6 2.0 CPC 2x(900)

14 40+375 7.4 7.0 BOX 2x(1.5x1.5)

15 40+675 2.3 2.0 CPC 1x(1200)

16 41+150 1.2 1.0 CPC 1x900

17 42+363 0.8 1.0 CPC 1x(900)

18 42+675 1.3 1.0 CPC 1x(900)

19 43+274 2.2 2.0 CPC 2x(900)

20 43+750 1.1 1.0 CPC 1x(900)

21 44+750 2.1 2.0 CPC 2x(900)


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Peak Discharge Q25,m3/sCatchment

NumberChainage

ActualRounded

Off

CulvertType

CulvertSize

22 46+300 6.3 6.0 CPC 3x(1200)

23 47+000 5.8 6.0 CPC 3x(1200)

24 47+425 5.7 6.0 CPC 3x(1200)

25 47+887 0.8 1.0 CPC 1x(900)

26 48+550 0.9 1.0 MPC 1x(900)

27 48+725 2.2 2.0 MPC 2x(900)

28 49+175 1.7 2.0 MPC 2x(900)

29 49+600 2.4 2.0 MPC 2x(900)

30 49+875 2.1 2.0 MPC 2x(900)

31 50+175 1.6 2.0 MPC 2x(900)

32 50+650 1.7 2.0 MPC 2x(900)33 51+050 7.6 8.0 BOX 3x(1.5x1.5)

34 51+825 2.6 3.0 MPC 2x(1200)

35 52+650 3.2 3.0 MPC 2x(1200)

36 52+800 7.8 8.0 BOX 3x(1.5x1.5)

37 53+150 1.4 1.0 MPC 1x(900)

38 53+475 1.9 2.0 MPC 1x(1200)

39 54+150 2.4 2.0 MPC 2x(900)

40 54+500 1.3 1.0 MPC 1x(900)

41 54+775 2.8 3.0 MPC 2x(1200)

42 55+548 2.4 2.0 MPC 2x(900)

43 55+775 6.8 7.0 BOX 2x(1.5x1.5)

44 56+925 0.8 1.0 MPC 2x(1200)

45 57+375 2.3 2.0 MPC 2x(1200)

46 58+065 6.7 7.0 BOX 2X(1.5X1.5)

47 58+725 0.9 1.0 MPC 1X900

48 59+175 1.98 2.0 MPC 2X900

Note: A headwater /depth ration of between 1 and 1.3 has been optimized by analysis

software, the worksheets of which are attached. These ratios take into account thedepth of road pavement layers to final level which was assumed as 500mm from subbase to surfacing.


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5.0 SOILS AND CONSTRUCTION MATERIALS INVESTIGATIONS

5.1 Background

The Terms of Reference (ToR), require of the Consultant to carry out an investigationof the soils and potential sources of construction materials along the entire section ofthe project road, testing and analysis of the alignment soils to determine theirproperties and suitability to act as foundation for embankments, geotechnicalinvestigations at each of the proposed bridge sites for purposes of obtaininginformation required for the selection and design of foundations for the bridgestructures and locate, test and assess the quality and available quantity of potentialconstruction materials.

The soils and materials investigations were carried out during the month of September2007 and the detailed results of these investigations have been compiled in thematerials report.

The site investigations comprised initially a reconnaissance survey with visualinspection and examination of materials along the proposed route. This was followedby a detailed investigation of the conditions of the soils found along the alignment bydigging trial pits and samples of the soils were sent to the laboratory for testing. Theresults of the laboratory tests have formed the basis for the pavement design.

The investigations comprised also prospection for suitable construction materials i.e.granular materials for pavement layers, sand for concrete and hard rock for productionof aggregates for concrete, surfacing works and stone base.

5.2 Geology and Soil s

The geological classification and types of soils in the project area is presented on theGeological map and soils map shown on next page.

The Rwenzori Mountain belongs to the Precambrian geological period and has beenseverely deformed and metamorphosed during the recent cainozoic geological periodinto acid and basic gneisses. Weathered products from these gneisses have later beendeposited in the areas where this road passes.

According to the soils map the soils along the first 10 kms of the road are dominatedby brown or black sandy loams often very stony originating from parent gneisses. Thesoils along the rest of the road are dominated by grey sands and sandy clay loams.


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MAPPING UNIT DOMINANT SOILS PARENT MATERIAL

87

93

123

Grey clays andsandy clay loams

Dark grey claysoccasionally saline

Shallow dark brown orblack sandy loams oftenvery stone

Rift valley sediments

Recent lake andriver alluvium

Granite, gneisses,schist, amphibolites

Figure 5.1: Soils Map


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Swamp deposits, alluvialand lacustrine deposits Un differentiated acidand basic gneisses

Fig. 5.2 Geology Map


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5.3 Cl imate

The climate in the project area is wet tropical with temperature averaging about 26o Cduring the day and 16o C at night. The hottest months are December to February withtemperatures up to 30o C.

The rainy seasons are generally from March to May and October to November. Theannual rainfall is 1300 1500 mm.

5.4 Exi st ing Condit ions along t he Prop osed Al i gnment

The proposed alignment commences a few hundred meters east of Itojo TradingCentre and runs through open farmland over the first 3 kms, then it joins the existingearth track originating from the west side of Itojo and continues over gentlyundulating terrain following the existing track up to approximately km 42+800, whereit is reduced to a path which is no longer motorable. Up to this point the track ismotorable by 4 wheel drive vehicles, but at two places where the road is crossed by

two seasonable rivers, having steep banks, the places are difficult to pass for even 4wheel drive vehicles during rains due to a slippery surface.

High ground is lightly forested and valleys are densely forested.

The soils at the surface over the first 8 kms are dominated by blackish clayeysilty/sandy soils, which at some places becomes slippery during rains and other placesare covered with stones and gravel. Rock outcrops have only been seen at high groundat Km 41+800 to Km 42+800 and these rocks are highly weathered and contain somemica. Rocks are also seen in the bed of some rivers, but again they are weathered toa certain degree and are not considered suitable for construction purposes. After thedescent at Kibuku the terrain is mostly flat although the ground is raised at some

places where ridges of coarse materials from the mountain are crossing the road.Otherwise the soils along the earth road following the foot of the mountain aredominated by clayey sand/silty soils all the way up to the end at Sempaya.

5.5 Sit e Invest igat ions

Site investigations were carried out to obtain data for detailed pavement design i.e. toobtain data on the strength of the sub-soils along the road and data on the quality andavailability of construction materials in order to achieve the most practical andeconomical solution to the design of the pavement layers.

5.4 .1 Subgra de Soil s

A total number of 50 trial pits were dug along the road alignment at maximumintervals of 500 m and dug to a depth of 0.7 1.0 m. The position of the trial pits isshown on the soils and materials plan, enclosed in the materials report.

At each trial pit test log pits were prepared and disturbed samples were extracted andtaken to the laboratory for classification and strength testing.


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The data recorded for the trial pits have been compiled in the materials report and asummary of the results from the laboratory tests have been enclosed.

5.4.2 Const ruct i on Mater i a ls

During the digging of trial pits some granular materials were discovered in a few trialpits. Some of these places were investigated further by digging additional pits in orderto confirm the quality and quantities which could be obtained in these places.

Representative samples of these materials were taken to the laboratory for testing.

The results from laboratory tests have been compiled in the materials report.

Ordinary fill and subgrade materialsInvestigations have indicated that ordinary fill and subgrade materials shall beimported solely from the road corridor i.e. from cuts in road sides and from major cutsin the roadline.

Meanwhile the best materials should be reserved for use as improved subgradematerials.

Improved subgrade materialsBesides the granular materials found at various points along the road line othersources have been identified at short distances off the road line. These sources werefound at km 37+800 LHS, km 41+000 RHS and at km 47+800 LHS and they consist ofweathered gravels, which are too weak for subbase construction, but suitable forconstruction of improved subgrade.

Natural gravels for subbase

One major source of quartzitic gravels has been found at Km 39+500 LHS close to theroadline. This deposit has an average thickness of only 1m underlain by soft weatheredsandy rocks, but the area is at least 30,000 m2 covering two shallow hills. Alsolaboratory testing has been carried out on this material and test results are attachedto the materials report.

Another source of gravel suitable for subbase construction is located along the FortPortal Bundibugyo Lamia Road, 1.4 km LHS off Km 58+500 of the Itojo SempayaRoad. This source contains oversized particles, which need to be separated, crushedand returned to the mix in order to enhance the grading of the materials. Further thesource materials have a plasticity, which needs to be reduced by chemical ormechanical stabilization.

It is practical to separate oversized particles from coarse materials. If the portion ofoversized particles are limited e.g. 5-10% these particles (stones) can easily beremoved by hand in the borrow pit or on the road when being graded. If the portion ishigh it is advisable to screen and crush these oversized particles and include thecrushed materials in the final mix as proven in the Hoima road project. Such


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processing will lead to extra cost. However, it is believed to be a cheap solution thanstabilizing the materials with lime or cement as the case might require.

Natural SandsNatural sands suitable for concrete works have been found at km 57 + 300 LHS. These

materials might need to be screened in order to satisfy the requirements to grading asthey also contain some gravel.

Fine sands have been found near Kibuku suitable for mechanical modification of clayeygravels to reduce excess plasticity. These sands may not be required for this sectionof road, but might be needed for construction of the sub base on the main road toBundibugyo.

This source of fine sand is available in a small hill at Km 44+100 LHS and is originatingfrom weathered sandstone which crushes to sand during excavation.

Hard rockMost of the rocks found along the road are weak weathered rocks and are seen in theriver beds.

Mean while a hard rock suitable for construction works were found at Sempaya Riverat km 57+300 LHS. It is available in kind of stones and boulders exposed in the riverbed and buried in soils at higher ground. However, huge masses of this rock areavailable near to the place where the river emerges at the foothill of the mountain. Itis estimated that sufficient quantities can be obtained from this source. Otherwisehard rocks are also available at Ntandi and Kichwamba.

WaterAll rivers in the project area are seasonable, except Semliki River at km 57 +350which can supply small quantities of water almost the year round. At km 47+800 RHSthere is another source of water, a small lake on the right side of the road which canprovide bigger quantities of water through most of the year.

5.5 Labora to ry Test ing

The following types of tests were performed on soils and granular materials;

i) Natural Moisture Content (NMC), BS 1377:1975, test (A)ii) Grain Size Analysis (GSA) BS 1377:1975, test 7A wet sievingiii) Liquid Limit (LL), Cone Penetration Method, BS 1377: 1975, Test 2(A)iv) Plastic Limit (PL), BS 1377: 1975, Test 3

v) Plasticity Index (PI) BS 1377: 1975, Test 4vi) Linear Shrinkage, BS 1377: 1975, Test 5vii) Plasticity Modulus, (PM), i.e. Plasticity Index (PI) multiplied by the passing on

0.425 mm sieve.viii) Plasticity Product, (PP), i.e. Plasticity Index (PI) multiplied by the passing on

0.075 mm sieve


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ix) Compaction: British Standard (BS) Heavy Compaction BS 1377: 1975, test 13 orAASHTO, T.180, The result is reported as Maximum Dry Density (MDD) in kg/m3and Optimum Moisture Content (OMC) in%.

x) Strength California Bearing Ratio (CBR) BS1377: 1975, test 16 or AASHTO,T.193.

xi) Samples were soaked in water for four days before penetration

Coarse materials were broken down to a maximum size of 37.5 mm before compactionand CBR testing and the mass of 20 37.5 mm was replaced with a similar mass of 5 20 mm size materials.

The following tests were performed on hard rock:

- Ten percent Fineness Value (TPF), wet/dry BS.812

- Los Angeles Abrasion (LAA) ASTM CBI

- Aggregate Crushing Value (ACV) BS.812

-

Aggregate Impact Value (AIV)BS.812

- Bitumen Affinity (BA) AASHATO, T.182

- Sodium Sulphate Soundness (SSS) BS.812

- Specific Gravity/Water Absorption BS.812

- Chloride and sulphate content BS.812

5.5. 1 Test Result s f or Subgrade soi l s

The alignment soils are dominated by clayey silts and sands, however silty clay wasencountered in a few places e.g. at km 44+100 and at Km 47+300 to km 48 + 800. Onthe average the subgrade soils have a Plasticity Index (PI) of 20% and a CBR strengthof 10% at 93% MDD at BS Heavy compaction.

Low CBR values in the range of 4 - 7% were found at 9 places along the roadline andthe highest values of swell in the CBR test were found for the same soils. Themeasured swell is in the range of 0.8 -1.25% and this degree of swell is within theallowable limit being max 2% for subgrade soils as per the general specifications andthey are far from being expansive in nature.

In several trial pits along km 34+800 Km 42+800 clayey gravels were found at depthof 0.2 0.6 m. These gravels have medium plasticity and CBR strength in the range of20 30% at 95% MDD at BS heavy compaction. They are suitable for improvedsubgrade layers. These gravels found in the trial pits along km 34+800 Km 42+800indicate that additional sources of improved subgrade materials can be found adjacentto the roadline.

The summary of laboratory test results are compiled in Materials Report. The variationof subgrade soil types and their CBR strength has been illustrated in Schedule ofsubgrade soils enclosed in the materials report.


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5.5.2 Test Resul t s f or Granular Mater i a ls

The clayey gravels found at km 37+800 LHS, KM 41+000 RHS and km 47+800 LHS havemedium plasticity with a Plasticity index (PI) in the range of 15 19% and a CBR strength of 20 24% at 95% MDD at BS Heavy Compaction. These gravels can satisfy the

requirements to improved subgrade but are too week for use in subbase layers.Deposits of good subbase materials are available at km 40+800 LHS,

Another source of subbase materials is available at km 58+500 1.4 km LHS locatedalong the Fort Portal Bundibugyo Lamia Road. This source has a CBR strength of 30 32% at 95% MDD at BS Heavy compaction, which is satisfactory for subbaseconstruction, but the Plasticity Index (PI) is higher than specified for subbase.Therefore it is necessary to stabilize these materials either chemically with lime ormechanically with fine sand.

It is estimated that mechanical modification with fine sand is the most economicalsolution and experiments show that 10 20% of fine sand added to the gravels will

reduce the plasticity sufficiently. However, given the limited supply of fine sand inthe area, we adopted stabilization using lime for the subbase.

It is foreseen that some of the gravels cannot achieve the required CBR strength fullywhen compacted to 95% of MDD, however, the test results show that the CBR strength can be increased considerably by increasing the degree of compaction a fewpercentage points.

The summary of laboratory test results are enclosed in the materials report.

5.5 .3 Test Result s f or Sand and Rock

The result of grading tests for sands and for hard rock at Sempaya River is enclosed inthe materials report . All test results satisfy the specified requirements.

5.6 Const r uct i on St ra t egies

5.6.1 General

After removal of unsuitable materials i.e. top soil and very soft soils it might benecessary to make further testing of the exposed subsoils to verify the quality of soilsat the lower strata.

During excavation of ditches and planned cuts more granular materials might beexposed and at such places further investigations should be executed to verify if new

borrow areas could be opened in order to reduce hauls.

The granular materials proposed for construction of the improved subgrade arepreferred because it will provide a stable running surface for the construction traffic.

Angles of slope


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The high slopes in cuts do not require to be protected with grass against erosion;however, the slopes of embankments require to be protected with grassing. Based onA practical guide to pavement design for tropical countries Ministry of Co-operation,France, the following slope angles are recommended;

Angles of slope in cuts:-

In clayey soils: 3 V: 1 H V =VerticalIn weathered rocks: 5V: 1 H H =Horizontal

Angles of slope in embankments in clayey soils:-

For heights less than 1 m: 1V: 1.5 HFor heights more than 1 m: 1V: 1.2 H

5.6.2 Modi f icat ion of Clayey Gravels

Some of the natural gravels proposed for construction of subbase have higher plasticitythan allowed in the general specifications although the CBR strength is satisfactory.

This plasticity can be reduced by addition of fine sands, which are available in twoplaces along the road.


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6.0 PAVEMENT DESIGN

6.1 General

The Terms of Reference (TOR) for this project requires the pavement design to be

initially made in accordance with Overseas Road Note 31 (ORN 31) published by theTransport Research Laboratory (TRL), UK, 1993.

It is further required that the resulting design should be verified with otherinternationally accepted methods in order to provide an optimum design for theproject. In this respect it has been decided to compare the design result from ORN31with design results from the Uganda Road Design Manual 1994 (URDM94) and the KenyaRoad Design Manual 1981 (KRDM81).

6.2 Design Appr oach

The design approach used in all of the above mentioned three design methods hasfollowed the below steps.

Calculation of the Design Traffic Assessment of climatic conditions Assessment of design strength of subgrade. Assessment of the availability of suitable construction materials. Selection of alternative pavement structures.

6.2.1 Calculat i on of Design Tr af f i c

The design traffic has been calculated based on a Traffic survey carried out at the FortPortal Bundibugyo Lamia Road during December 2006 and a detailed analysis of thetraffic and calculation of design traffic are given in Chapter 3; Traffic Survey &

Forecast.6.2. 2 Assessment of Cl i mat e Condit ions

The project is located in a wet tropical climate with two rainy seasons annually and ithas been established that the subgrade will be in saturated conditions over a total of 5months in one year.

6.2 .3 Assessment of Design St r ength of Subgra de

During the field investigations 50 No. trial pits were dug along the approximately 24Km long road and samples were taken at all trial pits and sent to Teclab laboratory fordetermination of soil characteristics and the CBR strength of the soils.

According to ORN31, Section 3, page 10, the strength of the subgrade for purpose ofpavement design shall be tested at moisture content equal to the wettest conditionlikely to occur in the subgrade after the road is opened to traffic. Most of the projectroad is running along the foothills of mountain Rwenzori and the subgrade is thussubjected to underground seepage of water during most of the year. Further, the


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silty/sandy soils in the subgrade will facilitate both direct seepage of water andindirect raising of water as a result of high capillarity in these soils.

The result of the strength testing has been shown as attachment in the Soils andMaterials Report.

The design CBR value has been derived from laboratory CBR testing on fully soakedsamples compacted to 93% MDD at BS heavy compaction which equals the in-situ CBRvalue attained in the subgrade after compaction to 93% MDD during constructionworks.

According to ORN 31, TRL, 1993, section 3.2 page 11, it has been recommended not toperform direct measurements of the in-situ CBR value e.g. by the use of DCP tests inthe subgrade soils due to the difficulties of ensuring that the moisture and densitiesconditions at the time of test are representative of those expected under thecompleted pavement. The CBR value determined in the laboratory under controlledconditions is therefore considered to be the most appropriate design CBR value.

In this schedule the road has been divided into four uniform sections and for each ofthese sections the CBR design strength was determined as the ten percentile value,which is exceeded by 90 percent of the CBR values. The result of the abovecalculations has been shown in Table 6.1 below.

Table: 6.1 Design Strength for Subgrade SoilsSection Design strength (CBR %)Km 34+800 - 40+800 5Km 40+800 - 43+800 10Km 43+800 - 47+300 5Km 47+300 - 59+300 8

There will therefore be two levels of design strengths namely:-- Subgrade with CBR 5%- Subgrade with CBR (8-10%)

6.2.4 Avai l ab i l i t y of Const ruct i on Mater i a ls

During recent field investigations following potential sources of construction materialswere found available in the vicinity of the road:

i. Weathered granular materials: having medium plasticity and CBR- strength inthe range of 15-25% at 95% MDD at BS Heavy compaction. These materialscannot meet the requirements to subbase, but they are very suitable for

construction of capping layer (improved subgrade) and are available insufficient quantities.

ii. Natural quartzitic granular materials having medium plasticity and CBR-strength of approximately 60% at 95% MDD at BS Heavy Compaction. Thesematerials are suitable for construction of subbase and are available at km


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40+800LHS close to the road line. Although these materials could be suitablefor base layers if stabilized with cement, however the quantities may not besufficient.

iii. Clayey granular materials: are available in an existing borrow pit along the

existing road Fort Portal-Bundibugyo, i.e 1.4km from the end of the projectroad at Sempaya. These materials can be used for improved subgrade layersand for subbase layers if modified with fine sand. The quantities available aresubstantial.

iv. Hard rock: suitable for production of aggregates for crushed stonebase,surfacing and concrete works are available at Sempaya River in sufficientquantities.

6.2.5 Select ion of Al t ernat ive Pavement St ructur es

Considering the availability of the above mentioned construction materials thefollowing two alternative pavement structures are possible.

Alternative 1

Surfacing : Bituminous Double surface dressingBase : Graded crushed stoneSubbase : Natural gravelsImproved subgrade : Natural gravels

Alternative 2

Surfacing : Bituminous Double surface dressing

Base : Graded crushed stoneSubbase : Natural gravels stabilized with limeImproved subgrade : Natural gravels

Since the Itojo Sempaya road link is part of the Fort Portal-Bundibugyo-Lamia roadDBST has been adopted as the surfacing as already agreed with the Client.

Subbase layer constructed with lime stabilized natural gravels might not be the moreeconomical solution, but is the only alternative for the section of road running alongthe mountain foothill between Kibuku and Sempaya if the source of quartzite gravelslocated at Km 40+800 is not enough for the full length of the subbase layer. Thesource of gravels located at 1.4 Km LHS off the Sempaya junction is the nearest source

of gravels suitable for Subbase stabilization.


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6.3 Design of Layer Thi cknesses- Alt ernat iv e 1

6.3 .1 Road Not e 31-Design Met hod

The design method in ORN 31 is considered to be the most suitable guide to thestructural design of light trafficked roads in the tropical and sub-tropical countries and

provides the most economical design for flexible pavements. A surfacing of DoubleSurface Dressing is recommended for such pavements.

The design method in ORN 31 is presented as design charts in a catalogue of a numberof different pavement structures.

Thicknesses for Subgrade with CBR = 5%

The design traffic was calculated in Section 3.10 of this report and is 1.729 x106 ESALs

As shown above, the design traffic falls under Traffic Class T.4 (1.5-3.0 x 106 ESA).The design strength of subgrade with CBR 5% was establish to belong to Class S3 (CBR

of 5-7%).

In the structural catalogue of ORN31 Chart 1 shall be used which gives thesethicknesses:

Road base : 200 mmSubbase : 275 mm

This Type of Pavement is not considered very economical and the RN 31, recommendsto use Selected Subgrade Materials on weak Sub grades as a substitute for a thickSubbase, ref. section 6.3 at page 26 of the RN31. Further, it is highlighted on Page 53of the ORN31 that up to 100mm of subbase may be substituted with selected fill

provided the subbase is not reduced to less than the roadbase thickness or 200mmwhich ever is greater. In this regard it is possible to reduce the subbase to 200mm andprovide for a selected subgrade of 75mm. Such Selected Subgrade or ImprovedSubgrade Materials shall have a minimum soaked CBR of 15%, however in this projectwas found sufficient quantities of granular material having a soaked CBR of 20% havingalmost subbase-quality.

The resulting pavement structure is therefore as depicted below:

CrushedStone Base

: 200 mm

Natrual

GravelSubbase

: 200 mm

ImprovedSubgrade 75mm

Thickness for Subgrade CBR = 8%