Geotechnical & Geo-environmental Site Investigation Report ...€¦ · Trivallis Limited have requested that a Geoenvironmental Site Assessment (GSA) and Geotechnical Investigation

Geotechnical & Geo-environmental Site Investigation Report: Proposed Residential Development, Penygraig Junior School, Hendrecafn Road, Tonypandy PREPARED FOR: Trivallis March 2019 Job No: 15212

March 2019 15212

REPORT TITLE : Geotechnical and Geoenvironmental Report Site Investigation Report: Proposed Residential Development, Penygraig Junior School, Hendrecafn Road, Tonypandy

REPORT STATUS : Final JOB NUMBER : 15212 DATE : March 2019 PREPARED BY : ……………………..

Mr Alan Beattie

REVIEWED BY : …………………………..

Mrs Ruth Howells

APPROVED BY : …………………………..

Dr Gwyn C Lake

March 2019 15212

Executive Summary

Proposed Development and Site Location

Trivallis Limited are proposing a residential development comprising 12 houses, 14 flats and 2 bungalows with associated access road, car parking areas and hard and soft landscaped and garden areas. The land is located at Penygraig Junior School, Hendrecafn Road, Tonypandy.

Site History The earliest edition shows the site to fall in an area of field land with a number of field boundaries crossing the site. The site is then developed by the 1920s with the construction of the school. Two further buildings are added in the 1970s and 1980’s and are subsequently removed in the 2019 edition.

Ground Conditions

VARIABLE MADE GROUND: Tarmac / (medium dense), reddish brown, slightly clayey SAND and GRAVEL with occasional ceramic and timber / (medium dense), dark grey and brown, slightly clayey sandy GRAVEL with slag and occasional brick / Soft, orange brown, sandy gravelly CLAY

Soft, dark brown, organic rich silty CLAY

Soft to firm / grey brown, silty very sandy CLAY / Soft becoming firm, light grey brown, sandy gravelly CLAY / Firm to stiff, orange brown and grey, slightly sandy gravelly CLAY / Medium dense, orange brown and grey / clayey gravelly SAND with occasional cobble

Radon No radon protection is required for the proposed buildings.

Laboratory Chemical Testing

Laboratory chemical testing has found a number of substances including Lead, PAH determinants and TPH above their respective guideline values in WS02 and WS03. It is considered that the PAH and TPH is from tarmac fragments from the surface that found their way into the sample.

Mitigation / Remediation

Due to the contamination identified on the site mitigation measures will be required. It is therefore recommended the north western quarter of the site is capped to break the source, pathway, receptor linkage. The area which requires capping can be seen in Drawing 02. The capping should comprise the proposed buildings, access road and hard standings. In soft landscaped and garden areas 600mm of suitable inert topsoil and subsoil should be used.

Gas Protection Measures

Gas monitoring has found elevated concentrations of Carbon Dioxide and gas characteristic situation 2 protection measures are required.

Foundation Solution

At present the foundation recommendations are preliminary and may need to be amended depending on the findings of the recommended site investigation into the shallow mining beneath the site. For the new development traditional concrete strip/trench foundations, founded within the underlying firm, grey and brown, sandy gravelly CLAY are recommended. Based upon the site investigation the depth to the in-situ founding horizon will be between 0.05m and 2.80m depth below the existing ground level. The founding horizon will be shallower towards the southern boundary of the site. It may be necessary to bench foundation if the founding horizon is seen to be deeper across a plot. The foundations should penetrate at least 200mm into the founding horizon and in order to prevent any effects from frost heave the foundations should extend to a minimum depth of 450mm. An allowable bearing pressure of 75kN/m2 may be used for design purposes. For the given foundation solution and bearing pressure, maximum total settlements of 30mm should result with differential movements of the superstructure not exceeding 1:750. The floor slabs should be designed and constructed as suspended. The prevailing ground conditions under the existing building should be confirmed by an appropriately qualified person once it has been demolished.

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TABLE OF CONTENTS SECTION 1 Introduction and Proposed Development

1.1 Introduction 1.2 Limitations and Exceptions of Investigation

SECTION 2 Review of Existing Data

2.1 Physical Setting and Current Site Use 2.2 Site History 2.3 Geological Setting

2.3.1 Geology 2.3.2 Mining 2.3.3 Radon

2.4 Environmental Setting 2.4.1 Hydrogeology and Hydrology 2.4.2 Groundwater 2.4.3 Flooding 2.4.4 Landfills and Infilled Land 2.4.5 Recorded Mineral Sites 2.4.6 Pollution 2.4.7 BGS Estimated Soil Chemistry 2.4.8 Sensitive Land Use

2.5 Japanese Knotweed SECTION 3 Preliminary Human Health and Environmental Risk Assessment

3.1 General 3.2 Preliminary Site Conceptual Model 3.3 Potential Sources of Contamination and Gas 3.4 Potential Receptors and Pollution Pathways 3.5 Preliminary Human Health and Environmental Risk Assessment 3.6 Preliminary Illustrative Site Conceptual Model

SECTION 4 Field Investigation

4.1 Site Works 4.2 Exploration Strategy 4.3 Ground Conditions 4.4 Water Strikes 4.5 Stability and Obstructions 4.6 Laboratory Chemical Testing 4.6.1 Quality Assurance 4.6.2 Sampling Regime 4.6.3 Laboratory Soil Analysis 4.7 Soil Property Testing 4.7.1 In-situ Gas Monitoring 4.7.2 Soil Plasticity Testing 4.7.3 In-situ Permeability Testing

SECTION 5 Soil Analytical Results

5.1 Soil Assessment Methodology 5.2 Soil Test Results

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TABLE OF CONTENTS (Continued) SECTION 6 Gas Monitoring SECTION 7 Quantitative Risk Assessment

7.1 Contaminants of Concern 7.2 Potential Receptors and Pathways 7.2.1 Human Receptors 7.2.2 Aquatic Environment 7.3 Mitigation and Remedial Measures 7.3.1 Human Health 7.3.2 Aquatic Environment 7.4 Refined Illustrative Site Conceptual Model

SECTION 8 Engineering Recommendations

8.1 Preparation of Site 8.2 Foundation and Floor Slab Solution 8.3 Excavations and Formations 8.4 Retaining Walls 8.5 Protection of Buried Concrete 8.6 Access Roads and Car Parking Areas 8.7 Storm Water Drainage

SECTION 9 Recommended Further Works Tables Table 2.1 Summary of Historical Map Information Table 3.1 Preliminary Human Health Risk Assessment Table 3.2 Preliminary Environmental Risk Assessment Table 4.1 Summary of Ground Conditions Table 4.2 Sample Locations and Depths Table 5.1 Summary of Soil Chemical Test Results: Standard Suite Table 5.2 Summary of Soil Chemical Test Results: Speciated PAH Table 5.3 Summary of Soil Chemical Test Results: Petroleum Hydrocarbons Table 5.4 Summary of Soil Chemical Test Results: Asbestos Screen Table 6.1 Measured Gas Concentrations Table 7.1 Summary of Contaminants of Concern in Soils Table 8.1 Plasticity Test Results Table 8.2 Effective Shear Stress Parameters Figures Figure 2.1 Site Location Figure 2.2 No 2 Rhondda Abandoned Mining Plan Extract Figure 3.1 Preliminary Illustrative Site Conceptual Model (not to scale) Figure 7.1 Refined Illustrative Site Conceptual Model (not to scale)

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TABLE OF CONTENTS (Continued) Annexes Annex A Envirocheck History Report Annex B Envirocheck Datasheet and Maps Annex C Coal Authority Mining Report Annex D Risk Assessment Definitions Annex E Mini Percussive Borehole Logs Annex F Laboratory Soil Chemical Test Results Annex G In-situ Gas Monitoring Results Annex H Laboratory Plasticity Test Results Drawings Drawing 01 Current Site Layout Drawing 02 Proposed Site Layout

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SECTION 1 Introduction and Proposed Development

1.1 Introduction Trivallis Limited are proposing a residential development comprising 12 houses, 14 flats and 2 bungalows with associated access road, car parking areas and hard and soft landscaped and garden areas. The land is located at Penygraig Junior School, Hendrecafn Road, Tonypandy. Terra Firma (Wales) Limited have been commissioned to undertake a geo-environmental assessment and geotechnical investigation of the site. The main objectives of the geo-environmental assessment programme were to:

Investigate the potential environmental liabilities at the site associated with any soil contamination

Provide a summary of the environmental conditions at the site, together with any necessary further intrusive works and / or remediation works to render the site fit for its intended use

The main objectives of the geotechnical site investigation were to:

Determine the type, strength and bearing characteristics of the shallow superficial and underlying solid geology

Provide engineering foundation and floor slab recommendations for the development

Provide recommendations with regard to any other geotechnical aspects pertaining to the development

In order to achieve the above objectives, Terra Firma (Wales) Limited carried out an assessment programme including a review of existing data, followed by a field investigation to collect geotechnical and environmental data from selected locations.

1.2 Limitations and Exceptions of Investigation Trivallis Limited have requested that a Geoenvironmental Site Assessment (GSA) and Geotechnical Investigation (GI) be performed in order to determine if contamination is present beneath the site and to determine an appropriate foundation and floor slab solution for the proposed development. The GSA and GI were conducted and this report has been prepared for the sole internal reliance of Trivallis Limited and their design and construction team. This report shall not be relied upon or transferred to any other parties without the express written authorisation of Terra Firma (Wales) Limited. If an unauthorised third party comes into possession of this report they rely on it at their peril and the authors owe them no duty of care and skill. The report represents the findings and opinions of experienced geo-environmental and geotechnical consultants. Terra Firma (Wales) Limited does not provide legal advice and the advice of lawyers may be required. The subsurface geological profiles, any contamination and other plots are generalised by necessity and have been based on the information found at the locations of the exploratory holes and depths sampled and tested. The site investigation was limited by:

Underground services

Existing buildings, structures and walls

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SECTION 2 Review of Existing Data

2.1 Physical Setting and Current Site Use The site is rectangular in shape and centres on a National Grid Reference of 299540 191930 occupying a plan area of approximately 0.61 Hectares / 6,100m². The site is currently occupied by the existing school building which locates in the south western corner. The north west and south eastern corner are playground areas and the north eastern corner is a grassed area. The site location is shown on Figure 2.1.

Figure 2.1 Site Location The northern boundary of the site is marked by a retaining wall below which is land behind the houses on Nantgwyn Street. The eastern boundary is marked by the property boundaries of the houses on Hill Street. The southern and western boundaries are marked by Hendrecafn Road and Brynderyn Road respectively. The site slopes to the north east and sits below a large retaining wall on the southern boundary. The site is then retained above the lane on the northern boundary. The surrounding area falls in elevation to the north east. Current and proposed site layouts are presented at the rear of the report in Drawing 01 and Drawing 02 respectively.

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2.2 Site History Historical maps of the site have been obtained in an Envirocheck History Report, provided by Landmark Information Group. The history plans are supplied in Annex A of this report, and the most relevant editions are summarised below in Table 2.1. Distances are approximate, and any changes occurring completely between map editions may not be recorded.

Table 2.1 Summary of Historical Map Information

Map Date and Scale

Key Features on Site Key Features off Site

1879-1881 (1:2,500)

The site falls in an area of field land and is crossed by a number of field boundaries. The western end of the site is also crossed by a track.

A small stream locates 160m to the west of the site. It flows in a northerly direction and converges with the large east west trending stream which flows to the east and is 60m from the site. An east west trending tramway is located 60m to the north of the site. A number of small quarries also locate in the area surrounding the site the closest of which locates 120m south east. An old coal level locates 160m north of the site and Adare Colliery is 220m to the north east.

1900 (1:2,500)

The field boundaries have been modified and the track now takes a different route across the site.

The surrounding area has seen significant development with many rows of terrace houses constructed to the north, south and south east of the site. Located immediately to the west of the north western corner is a quarry. A large quarry also locates 50m to the north of the site and 160m west of the site. Adare Colliery is no longer present and Pandy Coal Pit now locates 250m north east of the site. A north west to south east trending rail line locates 90m west of the site. The larger stream is identified as the Nant Gwyn.

1920 (1:2,500)

The site is now occupied by the school building which locates in the south western corner.

The surrounding area has seen further development and the site boundaries now take their present day form. The quarry immediately to the north west of the site is no longer present and appears to have been filled.

1938-1947 (1:10,560)

No significant changes. No significant changes.

1960-1961 (1:2,500)

The topography of the southern half of the site appears to have been modified.

The tramway to the north of the site has been dismantled.

1970-1974 (1:1,250)

Another large rectangular building is present in the south eastern corner of the site and is associated with the school.

The rail line to the west of the site has been dismantled.

1980-1989 (1:1,250)

A rectangular structure is located in the north western corner of the site.

No significant changes.

1993 (1:1,250)

No significant changes. The areas of the quarry immediately next to the north western corner has been developed and is now occupied by a large house.

1999 & 2006 (1:10,000)

No significant changes. No significant changes.

2019 (1:10,000)

The building in the north western corner and south eastern corner have been removed.

No significant changes.

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2.3 Geological Setting

2.3.1 Geology The 1:10,560 scale geological maps of the area (Sheet Glamorgan 27 NE and Envirocheck map) were consulted for geology underlying the site. The site is shown to be underlain by the Rhondda Beds of the Pennant Sandstone Formation, which are Carboniferous in age. The formation comprises “Green-grey, lithic arenites ("Pennant sandstones") with thin mudstone/siltstone and seatearth interbeds and mainly thin coals”. In the area of the site the dip of the bedrock is seen to be dipping between 5-15° north east. The north west to south east orientated conjectured outcrop of the No 2 Rhondda coal seam is seen approximately 170m to the north east of the site. Given the dip of the bedrock geology and slope of the area it is likely to underlie the site at shallow depth beneath the site. The bedrock geology is seen to be overlain by superficial deposits of boulder clay (glacial till). This is likely to comprise clay and silt with varying quantities of sand, gravel, cobbles and boulders. The historic maps have shown the site to be occupied by a school and an exercise of cut and fill may have been undertaken. Made ground may therefore be present on the site and is likely to be thicker closer to the northern boundary. The underlying geology is not prone to dissolution and the risk of natural cavities in the bedrock is considered negligible. The Envirocheck geological map can be found in Annex B.

2.3.2 Mining Terra Firma (Wales) Limited obtained a Coal Authority Mining report for the site. The property is in a surface area that could be affected by underground mining in 12 seams of coal at shallow to 530m depth, last worked in 1949. Where coal is recorded as shallow it is within 30m of the surface. The report also concludes that there are no known coal mine entries within, or within 20m, of the boundary of the property. The location of the No 2 Rhondda Coal Seam to the north east of the site (topographically lower) and the dip of the bedrock means that it will underlie the site. The stratigraphic column also shows the Forest Fach, a thin coal seam, above the No 2 Rhondda. This is not shown on the geological map but may also underlie the site.

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2.3.2 Mining (Continued) The abandoned mining plans for the No 2 Rhondda Coal Seam were obtained for the site from the Coal Authority. The plan was positioned by correlating the rivers in the area with a historic map from which the site boundary could be transferred. An extract can be seen below and shows the site to underlain by an area of workings associated with the Adare Colliery.

Figure 2.2 No. 2 Rhondda Abandoned Mining Plan Extract

There is no record of a mine gas emission requiring action. It is therefore considered that there is a risk from past underground mining and intrusive works will be required, these are detailed in Section 9. The Coal Authority Mining report can be found in Annex C.

2.3.3 Radon The Envirocheck datasheet (Annex B) details that the site is in a lower probability radon area as less than 1% of homes are estimated to be at or above the action level. NO radon protection measures are required for new development on the site.

2.4 Environmental Setting The following sections have been compiled using the Envirocheck datasheet and maps which can be found in Annex B.

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2.4.1 Hydrogeology and Hydrology The Envirocheck data shows the nearest surface water feature 59m to the north of the site this corresponds with the Nant Gwyn. The Nant Gwyn flows in a westerly direction and converges with the Rhondda River at a distance of 260m from the site. The site falls on an east facing slope and the site and surrounding area fall in this direction. Shallow groundwater is anticipated to flow in this direction. Given the urban nature of the site and surrounding area surface water is likely to be collected by surface water drainage systems. Deep groundwater flow within the underlying bedrock will be controlled by the strata dip and any fractures or bedding planes within the rock units. The hydraulic gradient will be at its steepest during periods of heavy rainfall and aquifer recharge. The bedrock beneath the site has an aquifer designation of ‘Secondary A’. These are “permeable layers capable of supporting water supplies at a local rather than strategic scale, and in some cases forming an important source of base flow to rivers. These are generally aquifers formerly classified as minor aquifers”. The superficial deposits are classed as a ‘Secondary Undifferentiated’ aquifer. This has been assigned in cases where it has not been possible to attribute either category A or B to a rock type. In most cases, this means that the layer in question has previously been designated as both minor and non-aquifer in different locations due to the variable characteristics of the rock type.

2.4.2 Groundwater There are no groundwater source protection zones within 1km of the site. There are no groundwater abstraction points within 1km of the site.

2.4.3 Flooding The maps show that the site does not fall in an area at risk of flooding from rivers or the sea. The north eastern corner of the site is close to an area at risk of flooding from surface water. The site falls in an area where there is limited potential for groundwater flooding to occur.

2.4.4 Landfills and Infilled Land There are no recorded landfill sites (historic or current) within a 250m radius of the site. An area of potentially infilled land is recorded 6m to the north of the site. This corresponds to the quarry that was seen on the historical maps.

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2.4.5 Recorded Mineral Sites There are three recorded mineral sites within 250m of the site, the closest of which locates 50m north. All three were extracting Rhondda Member Sandstone by opencast methods. The operations have now ceased.

2.4.6 Pollution There are no entries on the contaminated land register within 1km of the site. There have been no recorded pollution incidents to controlled waters within a 250m radius of the site. There are no records on the substantiated pollution incident register within 250m of the site.

2.4.7 BGS Estimated Soil Chemistry The BGS have published anticipated soil concentrations for a number of common contaminants, i.e. arsenic, cadmium, chromium, lead and nickel. The estimated concentrations of the contaminants for the site are listed as below: Arsenic: 15-25 mg/kg Cadmium <1.8 mg/kg Chromium 60 – 90 mg/kg Lead <100 mg/kg Nickel 15 – 30 mg/kg The estimated concentrations are below the residential guidelines with plant uptake.

2.4.8 Sensitive Land Use There are 4 areas of ancient woodland located within 1km of the site. The closest occurrence locates 331m to the east of the site.

2.5 Japanese Knotweed A site walk over was undertaken to identify any potential occurrences of Japanese Knotweed. No Japanese Knotweed was identified on the site however the site was visited outside of the active growing season. Further information on Japanese Knotweed can be found in the Environment Agency’s document Managing Japanese Knotweed on Development Sites (The Knotweed Code of Practice). Please note that Terra Firma (Wales) Limited are not specialists in this field and the advice of experts may be required.

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SECTION 3 Preliminary Human Health and Environmental Risk Assessment

3.1 General The contaminated land regime is set out in Part IIA of the Environmental Protection Act (EPA) 1990 and was introduced on the 1st April 2000 in England and 1st July 2001 in Wales. A similar regime was introduced in Scotland on 14th July 2000. Part IIA was introduced to achieve two aims: (1) The identification of contaminated land (2) The remediation of contaminated land that poses an unacceptable risk to

human health and/or the environment Under Part IIA the statutory definition of ‘contaminated land’ is: any land which appears to the local authority in whose area it is situated, to be in such a condition, by reason of substances in, on, or under the land, that: (a) Significant harm is being caused or there is a significant possibility of such

harm being caused; or (b) Pollution of controlled waters is being, or is likely to be, caused.” For land to be classified as ‘Contaminated Land’ there must be a ‘pollutant linkage’. For our definitions of pollution linkage and how we define risk please refer to Annex D which includes our classifications of consequence and probability and risk assessment matrix.

3.2 Preliminary Site Conceptual Model The preceding sections enable a preliminary conceptual model of the site to be drawn up, to illustrate the likely ground conditions beneath the site together with a preliminary assessment of the nature of any underlying aquifers and groundwater movement. The preliminary site conceptual model is used as a model for the design and implementation of the site investigation, whereby areas of potential contamination can be targeted as well as investigating the site as a whole.

3.3 Potential Sources of Contamination and Gas The potential contamination beneath the site, whether in the matrix of soil or groundwater is related to the sites past use. The site has been occupied by a school and two associated buildings have been added and removed from the site. Where buildings have been present there is the potential for asbestos containing materials (ACMs) to have been used. Any made ground encountered should therefore be subject to asbestos testing. A portion of the playground also appears to have been used for car parking and it would therefore be prudent to undertake some petroleum hydrocarbon testing. No potential sources of landfill gas and volatiles has been identified. Ground gas may be present from the infilled quarry to the north of the site. Made ground is also anticipated on the site associated with the supposed cut and fill exercise previously undertaken. The risk of ground gas is considered moderate.

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3.4 Potential Receptors and Pollution Pathways There are human and hydrological receptors to any contamination that may be present on site. Construction workers will be excavating in soils and will be exposed via dermal contact with soils and dust, ingestion of soil dust and inhalation of soil dust. A residential end use is proposed. Once developed, future site users (residents and visitors) will potentially be at risk from contaminated soils through the same pathways as well as though consumption of site grown produce and potable drinking water. Landfill gas, ground gas and radon gas may also present a risk to site end users through inhalation or from the risk of explosion of gases in confined spaces. Neighbouring site users and passers-by may potentially be exposed to soil dust. If contamination is identified it may be leachable, enabling it to mobilise through perched groundwater within site soils and impact on deeper groundwater or surface water. A Preliminary Human Health and Environmental Risk Assessment summarises the above and is detailed in the Table 3.1 below and on the following pages.

3.5 Preliminary Human Health and Environmental Risk Assessment

Table 3.1 Preliminary Human Health Risk Assessment

Potential Source

Potential Pathway Potential Target

Preliminary Risk Assessment

Human Health Site Soil Dermal contact with

soil, ingestion of soil/soil dust, inhalation of soil dust

Construction workers

Low to Moderate Risk

COSHH assessment and good level of PPE/ hygiene by site workers/ staff; dust suppression measures if required.

Site Soil Dermal contact with soil, ingestion of soil/soil dust inhalation of soil dust

Passers -by/neighbouring site users

Low Risk

Made ground is anticipated.

Site Soil Dermal contact with soil, ingestion of soil/soil dust or site grown vegetables, inhalation of soil dust

Site End Users – Residents and visitors.

Low Risk

Made ground is anticipated.

Radon Gas from underlying bedrock

Migration into indoor air Site End Users – Residents and visitors

Negligible Risk BGS Radon Report confirms NO radon

protection measures required.

Landfill gas Migration through superficial deposits and bedrock and accumulation indoors

Site End Users – Residents and visitors

Negligible Risk

There are no historic or active landfills within influencing distance of the site.

Ground gas Direct from any made ground/buried organic matter on site and accumulation indoors


Moderate Risk

An infilled quarry locates in close proximity to the site and made ground is anticipated.

Vapours Migration into indoor air Site End Users – Residents and visitors

Low Risk

No source of vapours has been identified on the site.

Site Soils Permeation of drinking water pipes


Low Risk

Correct pipe material to be used.

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3.5 Preliminary Human Health and Environmental Risk Assessment (Continued)

Table 3.2 Preliminary Environmental Risk Assessment

Aquatic Environment

Site Soils Surface runoff and leaching of contamination into the perched groundwater

Perched groundwater beneath the site

Low Risk

Significant leachable contamination is not anticipated at this stage

Site Soils Groundwater transport Surface water features (Nant Gwyn and Rhondda River)

Low Risk


Site Soils Groundwater transport Underlying Bedrock: Secondary A Aquifer (Pennant Sandstone Formation)

Low Risk


Building Materials

Site Soils Damage of building materials

New buildings Very Low Risk

Correct class of concrete to be chosen

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3.6 Preliminary Illustrative Site Conceptual Model The following illustration represents a theorised cross section through the site. The drawing is generalised and not to scale.

Figure 3.1 Preliminary Illustrative Site Conceptual Model (not to scale)

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SECTION 4 Field Investigation

4.1 Site Works A geotechnical and geo-environmental site investigation comprising nine mini percussive boreholes including three soakaway tests was undertaken on 7th February 2019. The boreholes were sunk with a Dando Terrier Mini Percussive Drilling Rig and a breaker was used to facilitate drilling through hard standing. The proposed locations of the boreholes was determined by Terra Firma (Wales) Limited. The fieldworks were also supervised by Terra Firma (Wales) Limited, who logged the exploratory holes to the requirements of BS5930:2015. The mini percussive borehole logs are presented in Annex E and their locations are shown on Drawing 01 and Drawing 02.

4.2 Exploratory Strategy It is considered that the number and spacing of exploratory holes was adequate to: • Investigate the presence, nature and distribution of contamination on site in an

efficient but cost effective manner. • Optimise the chances of finding contamination hot spots of various sizes and

orientations. • Provide good representation of the ground conditions beneath the site. • Provide sufficient data to determine suitable remedial measures if necessary.

4.3 Ground Conditions The ground conditions encountered by the exploratory holes can in general be summarised as shown in Table 4.1. The detailed trial pit logs should also be consulted.

Table 4.1 Summary of Ground Conditions

Depth (m) Thickness (m) Stratum

GL 0.05/1.30 1.50

- - -

0.05/1.30

1.50

>1.40/4.00

0.05/1.30

0.30 -

VARIABLE MADE GROUND: Tarmac / (medium dense), reddish brown, slightly clayey SAND and GRAVEL with occasional ceramic and timber / (medium dense), dark grey and brown, slightly clayey sandy GRAVEL with slag and occasional brick / Soft, orange brown, sandy gravelly CLAY Soft, dark brown, organic rich silty CLAY Soft to firm / grey brown, silty very sandy CLAY / Soft becoming firm, light grey brown, sandy gravelly CLAY / Firm to stiff, orange brown and grey, slightly sandy gravelly CLAY / Medium dense, orange brown and grey / clayey gravelly SAND with occasional cobble

An obstruction was encountered in TP07 and TP07A and the hold could not be advanced beyond 0.60m.

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4.4 Water Strikes Groundwater was seen to be standing in the base of WS02 and WS03 the soil samples recovered were also seen to be wet at these depths. The remaining boreholes were dry for the duration they were open.

4.5 Stability and Obstructions Short term instabilities were seen in the made ground. WS07 and WS07A were unable to be advance beyond 0.60m. The obstruction was could not be identified however large cobbles were encountered. Obstructions may also be present where the former buildings have stood.

4.6 Laboratory Chemical Testing

4.6.1 Quality Assurance During the intrusive investigation, 8 small disturbed soil samples were collected. Care was taken to ensure that sampling quality assurance occurred during site works. This included the following measures: • Soil samples were collected by hand with nitrile gloves. • Clean gloves were used for each sample. • Soil samples were stored at a temperature below 4 degrees. • No head space was left in sample containers. • Appropriate sample containers were used. • Samples were submitted for laboratory testing within holding times.

4.6.2 Sampling Regime The sampling regime was conducted in accordance with BS5930:2015 in order to satisfy the following criteria: • Investigate suspected sources of contamination • Investigate type and concentration of contamination • Ensure good representation of the site • Provide data to advise on remedial measures if necessary The sample locations and depths are illustrated in the following table:

Table 4.2 Sample Locations and Depths

Sample Depth (m) Lab Description

WS01 0.30 Brown sandy with stones



WS04 0.50 Brown clay with stones



WS08 0.60 Brown clay with stones


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4.6.3 Laboratory Soil Analysis During the site works a number of soil samples were taken and despatched to the laboratories of Derwentside Environmental Testing Services (DETS) for laboratory chemical testing; Metals and Metalloids In-Organics Others Lead Cyanide pH (acidity) Arsenic Sulphate Asbestos Screen Mercury Cadmium Chromium III Organic Chemicals Chromium VI Phenols Copper Polyaromatic Hydrocarbons (PAH) Nickel Petroleum Hydrocarbons (TPH CWG) Zinc Selenium The results are discussed in detail in Section 5 and the laboratory test results certificates may be found in Annex F.

4.7 Soil Property Testing

4.7.1 In-situ Gas Monitoring During the site investigation works three gas monitoring wells were installed in the mini percussive boreholes, WS01, WS04 and WS06. The details of the installation can be found on the borehole logs. The sections of slotted pipe were covered with a geosock and surrounded by gravel. The plain sections were surrounded with a bentonite seal. The boreholes were then monitored for concentrations of methane, carbon dioxide, oxygen, hydrogen sulphide and carbon monoxide. The barometric pressure and flow rate from the boreholes was also recorded. The results are discussed in Section 6 and the detailed results sheets can be found in Annex G.

4.7.2 Soil Plasticity Testing During the fieldworks three small disturbed soil samples of the in-situ materials were taken and despatched to the laboratories of GEO Site and Testing Solutions Limited in Llanelli for plasticity testing. The tests were undertaken to the appropriate British standards. The test results are presented in Annex H and discussed in detail in Section 8.2 of this report.

4.7.3 In-situ Permeability Testing During the site investigation three soakage tests were undertaken in WS02, WS05 and WS08. The tests were undertaken to the requirements of BS5930: 2015 The test results are discussed in Section 8.6.

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SECTION 5 Evaluation of Soil Analytical Results

5.1 Soil Assessment Methodology Comparison of the analytical results has been made with Soil Guideline Values (SGVs) for a residential scenario (with plant uptake), sourced from The Environment Agency Contaminated Land Exposure Assessment (CLEA). Where SGV values are not available reference has been made to the 2015 residential Suitable 4 Use Levels (S4ULs) provided by Land Quality Management Limited and the Chartered Institute of Environmental Health (CIEH) or Category 4 Screening Levels (C4SLs). Sulphate results have been compared to British Research Establishment (BRE) guidelines as sulphate levels need only be considered for buried concrete risk assessment only, not human health related.

5.2 Soil Test Results A summary of the chemical test results which include the regulatory soil guideline values used in the Tier 1 assessment are given in Table 5.1 to Table 5.4 and can be found in Annex E. Standard Suite

Table 5.1 Summary of Soil Chemical Test Results: Standard Suite

Substance SGV/GAC

(mg/kg)

Source Measured Concentrations

(mg/kg)

Number of Exceedences

Minimum Maximum

Arsenic 37 CIEH 3.6 20 0

Cadmium 11 CIEH <0.1 0.30 0

Chromium III 910 CIEH 9.9 17 0

Chromium VI 6 CIEH <0.50 <0.50 0

Copper 2400 CIEH 5.2 81 0

Lead 200 C4SL 9.5 270 1

Mercury 40 CIEH <0.05 0.11 0

Nickel 180 CIEH 9.9 58 0

Selenium 250 CIEH <0.20 0.88 0

Zinc 3700 CIEH 40 91 0

Cyanide 8 CLEA <0.50 1.6 0

Phenols 120 CIEH <0.30 <0.30 0

Sulphate 2400 - <100 1200 -

Organic Matter - - 0.60 3.5 -

pH - - 6.5 10.3 -

Total PAH 0.1 - <2.0 44 See Table 5.2

Notes:

CLEA-Soil guideline values for a residential development with plant uptake

LQM/CIEH - Generic Assessment Criteria for a residential development with plant uptake

C4SL - Category four screening level for a residential development with plant uptake

BRE - British Research Establishment

LDL - Laboratory Detection Limit

A total of 8 samples were tested

- no available guideline

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5.2 Soil Test Results (Continued) Speciated PAH

Table 5.2 Summary of Soil Chemical Test Results: Speciated PAH Substance GAC

(mg/kg) Source Measured Concentrations

(mg/kg) Number of

Exceedences

Minimum Maximum

Naphthalene 2.3 LQM/CIEH <0.10 0.34 0

Acenaphthylene 170 LQM/CIEH <0.10 0.44 0

Acenaphthene 210 LQM/CIEH <0.10 0.34 0

Fluorene 170 LQM/CIEH <0.10 0.58 0

Phenanthrene 95 LQM/CIEH <0.10 3.6 0

Anthracene 2400 LQM/CIEH <0.10 3.3 0

Fluoranthene 280 LQM/CIEH <0.10 5.5 0

Pyrene 620 LQM/CIEH <0.10 5.3 0

Benzo(a)anthracene 7.2 LQM/CIEH <0.10 3.5 0

Chrysene 15 LQM/CIEH <0.10 3.4 0

Benzo(b)fluoranthene 3.3 LQM/CIEH <0.10 4.4 2

Benzo(k)fluoranthene 77 LQM/CIEH <0.10 2.2 0

Benzo(a)pyrene 2.2 LQM/CIEH <0.10 4.7 2

Indeno(123cd)pyrene 27 LQM/CIEH <0.10 4.3 0

Dibenzo(ah)anthracene 0.24 LQM/CIEH <0.10 1.1 1

Benzo(ghi)perylene 320 LQM/CIEH <0.10 4.1 0

Total PAH - - <2.0 44 -

Notes:

LQM/CIEH - Generic Assessment Criteria for a residential development with plant uptake.

Guidelines for a residential land use with plant uptake.

Thresholds based on 1.0% SOM 8 samples were tested for Speciated PAH

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5.2 Soil Test Results (Continued) Petroleum Hydrocarbons

Table 5.3 Summary of Soil Test Results: Petroleum Hydrocarbons Substance SGV/GAC

(mg/kg) Source Measured Concentrations

(mg/kg) Number of

Exceedences

Minimum Maximum

Aliphatic

PH C5 – C6 Ali 42 LQM/CEIH <1.0 <1.0 0

PH C6 – C8 Ali 100 LQM/CEIH <1.0 <1.0 0

PH C8 – C10 Ali 27 LQM/CEIH <1.0 9.2 0

PH C10 – C12 Ali 130 LQM/CEIH <1.0 22 0

PH C12 – C16 Ali 1100 LQM/CEIH 4.6 56 0

PH C16 – C21 Ali 65000# LQM/CEIH 1.9 100 0

PH C21 – C35 Ali 65000# LQM/CEIH 18 160 0

PH C35 – C44 Ali 65000 LQM/CIEH <1.0 66 0

Aromatic

PH C5 – C7 Arom 70 LQM/CEIH <1.0 <1.0 0

PH C7 – C8 Arom 130 LQM/CEIH <1.0 <1.0 0

PH C8 – C10 Arom 34 LQM/CEIH <1.0 6.4 0

PH C10 – C12 Arom 74 LQM/CEIH <1.0 16 0

PH C12 – C16 Arom 140 LQM/CEIH 3.1 230 1



PH C35 – C44 Arom 1100 LQM/CIEH <1.0 440 0

Notes:

LQM/CIEH - Generic Assessment Criteria for a residential development with plant uptake

A total of 4 soil samples were tested for Petroleum Hydrocarbons

Ali - Aliphatic Hydrocarbon

Arom - Aromatic Hydrocarbon

LQM/CEIH Based on 1.0% SOM # - LQM for Ali C16 - 21 and C21 - C35 based on LQM for EC >16 - 35

Asbestos Screen Asbestos testing was undertaken all five samples taken from the site. Table 5.3 below summarises the findings:

Table 5.4 Summary of Soil Test Results: Asbestos Screen

Substance Location Depth (m) Result Comment

Asbestos

WS01 0.30 NAD -

WS02 0.40 NAD -

WS03 0.50 NAD -

WS04 0.50 NAD -

WS05 0.30 NAD -

WS06 0.80 NAD -

WS08 0.60 NAD -

WS09 0.40 NAD -

Notes:

NAD – No Asbestos Detected

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SECTION 6 Gas Monitoring Three gas wells were installed to assess if there are any risks from ground / landfilll / mine gas on site. The wells were installed in WS01, WS04 and WS06. One round of gas monitoring has been completed to date. The following minimum and maximum gas concentrations have been recorded:

Table 6.1 Measured Gas Concentrations

Gas Minimum (% V/V)

Maximum (% V/V)

Methane Not Detected Not Detected

Oxygen 8.2 18.9

Carbon Dioxide 0.1 6.1

The gas flow rate from the boreholes was also assessed. No positive flow rate was recorded during the first round of monitoring and the detection limit of the gas analyser has been utilised. Based on the detection limit of 0.1l/hr and the highest recorded carbon dioxide concentration of 6.1% V/V, a gas screening value of 0.0061l/hr is calculated, as follows: (6.1/100) x 0.1 = 0.0061l/hr When this result is compared with Table 8.5 of CIRIA report C665, the site is classified as ‘gas characteristic situation 1’ (GCS1). However as the concentration of carbon dioxide has exceeded 5% the classification will need to be increased to ‘gas characteristic situation 2’ (GSC2). For sites which are GSC2, Table 8.6 of CIRIA Report C665, details that the following precautions are required for a residential development:

Reinforced concrete cast in-situ floor slab (suspended, non-suspended or raft) with at least 1200 g DPM2 and underfloor venting.

Beam and block or pre-cast concrete and 2000 g DPM / reinforced gas membrane and underfloor venting

All joints and penetrations sealed On completion of the full six rounds of gas monitoring the above recommendations will be reviewed and if necessary amended. The gas monitoring results are presented in Annex G.

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SECTION 7 Quantitative Risk Assessment

7.1 Contaminants of Concern Soil The following contaminants of concern have been identified in soils:

Table 7.1 Summary of Contaminants of Concern in Soils

Location and Depth (m) Substance GAC

(mg/kg) Measured Concentrations

(mg/kg)

WS02 at 0.40m

Lead 200 270

Benzo(b)fluoranthene 3.3 4.4

Benzo(a)pyrene 2.2 4.7

Dibenzo(ah)anthracene 0.24 1.1

Aromatic C12 – C16 140 230

Aromatic C16 – C21 260 820

Aromatic C21 – C35 1100 2800

WS03 at 0.50m Benzo(a)pyrene 2.2 3.0

Leachate The above determinants are not considered to pose a risk through leaching and this is discussed further in Section 7.3.2. Gas and Vapours Gas monitoring has found elevated concentrations of Carbon Dioxide and gas characteristic situation 2 protection measures are required. No source of vapours has been identified on the site.

7.2 Potential Receptors and Pathways

7.2.1 Human Receptors The potential receptors at the site are construction workers, neighbouring site users and passers-by and site end users. They are potentially at risk from dermal contact with soils, inhalation and ingestion of soil and soil dust and site end users are also at risk from the consumption of home grown produce.

7.2 2 Aquatic Environment The underlying bedrock has been classed as a ‘Secondary A’ Aquifer. The superficial deposits are classed as a ‘Secondary Undifferentiated’ aquifer. The site does not situate within a groundwater source protection zone and there are no groundwater abstraction points within 1km of the site. Shallow groundwater flow in the area will be towards the east following the topography of the area.

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7.3 Mitigation and Remedial Measures

7.3.1 Human Health Due to the contamination identified on the site mitigation measures will be required. It is therefore recommended the north western quarter of the site is capped to break the source, pathway, receptor linkage. The area which requires capping can be seen in Drawing 02. The capping should comprise the proposed buildings, access road and hard standings. In soft landscaped and garden areas 600mm of suitable inert topsoil and subsoil should be used. As good practise, construction workers should adhere to good site management, COSHH, good standards of hygiene and appropriate health & safety on site, with personal protection equipment (PPE) and dust suppression where appropriate. If during development works any other unexpected ground conditions or evidence of contamination is found, inspection by a geo-environmental engineer should be made, and any required testing or investigation carried out prior to continuation of works. For proposed new supply water pipes, the UK Water Industry Research publication ‘Guidance for the Selection of Water Supply Pipes to be used in Brownfield Sites (Report 10/WM/03/21)’ should be consulted. The capping material and thickness should be confirmed and any imported soils and aggregates should be tested and validated as suitable prior to use on site in accordance with the ‘Requirements for the Chemical Testing of Imported material for Various End Uses and Validation of Cover Systems’ prepared by the Welsh Land Contamination Working Group.

7.3.2 Aquatic Environment Lead and a number of PAH and PH speciates have been found to be above guideline values. It is suspected that these hydrocarbon determinants are from fragments of tarmac which has been included in the sample. This is supported by the determinants in exceedence falling at the heavier end of the hydrocarbon banding. The aquatic environment is not considered to be at risk from the PAH and PH contamination identified on the site as according to the CL:aire publication titled Petroleum Hydrocarbons in Groundwater, the determinants in exceedence have very low relative mobility in groundwater. The underlying materials are also clayey in nature and soakaway testing has shown the soils to have a low permeability. In addition to this capping of the site with the proposed development will reduce the available water for infiltration into the ground. The aquatic environment is therefore not considered to be a risk from the determinants identified above and any contaminants would soon be rendered insignificant through the effects of dilution and attenuation given the distance to the nearest surface water feature. During the construction period, there is a risk to the environment/adjacent sites from de-watering, digging foundations, moving contaminated soil, drainage misconnections, discharges to local surface waters or the ground, runoff from construction materials and/or exposed ground, wheel washings and oil or chemical spills.

March 2019 15212

7.3.2 Aquatic Environment (Continued) The risk is considered to be negligible as any adverse effects will be easily preventable by due diligence to good construction practise and housekeeping in preventing surface runoff and the spillage of materials. The basic measures that should be taken are as follows:

Prepare a drainage plan and mark the manholes to prevent pollutants accidently reaching the surface water sewers;

Carry out any activities that could cause pollution in a designated, bunded area, away from rivers. Where possible it should drain to the foul sewer;

Use settlement ponds to remove silty water;

Store all oils and chemicals in a fully bunded area to prevent leaks or spills;

Get advice on whether you need an environmental permit and apply in good time

7.4 Refined Illustrative Site Conceptual Model

Figure 7.1: Refined Illustrative Site Conceptual Model (not to scale)

March 2019 15212

SECTION 8 Engineering Recommendations

8.1 Preparation of Site Prior to demolition of the existing building an appropriate asbestos survey should be undertaken including full pictorial records. Any deleterious material identified should then be removed by a suitably qualified person and disposed of to a suitably licenced landfill facility prior to the start of works. A structural survey of the existing retaining walls should be undertaken by a structural and civil engineer prior to the commencement of works. All existing hard standings, top soil, scrub vegetation including all roots should be stripped and removed from beneath the proposed buildings and areas of hard standing. Contingencies should be made for the protection/diversion any underground/overhead services present beneath the site brought about as a result of the proposed works. Allowances should be made for the excavation of any soft spots/areas and their replacement with well compacted imported granular materials. Allowances should also be made for the temporary or permanent support of existing structures. Any reduced levels should be brought up to the required levels with suitable inert mainly granular materials. Department of Transport (DoT) type 2 sub base or similar should be used and should be compacted in layers to the requirements of the Specification for Highway works. In accordance with EC Regulation 1272/2008 and Environment Agency Guidance WM3 soils and other materials destined for off-site disposal should be classified on the basis of their hazard phrases prior to disposal. Soils are classified as a mirror entry waste and should be classified on the basis of their specific chemical properties. Terra Firma (Wales) Ltd offer this service if required.

8.2 Foundation and Floor Slab Solution At present the foundation recommendations are preliminary and may need to be amended depending on the findings of the recommended site investigation into the shallow mining beneath the site. For the new development traditional concrete strip/trench foundations, founded within the underlying firm, grey and brown, sandy gravelly CLAY are recommended. Based upon the site investigation the depth to the in-situ founding horizon will be between 1.00m and 2.80m depth below the existing ground level. The founding horizon will be shallower towards the southern boundary of the site. It may be necessary to bench foundation if the founding horizon is seen to be deeper across a plot. The foundations should penetrate at least 200mm into the founding horizon and in order to prevent any effects from frost heave the foundations should extend to a minimum depth of 450mm. An allowable bearing pressure of 75kN/m2 may be used for design purposes. For the given foundation solution and bearing pressure, maximum total settlements of 30mm should result with differential movements of the superstructure not exceeding 1:750.

March 2019 15212

8.2 Foundation and Floor Slab Solution (Continued) The floor slabs should be designed and constructed as suspended. To maintain stability a 45° line struck from the outermost edge of the foundation should not impinge on the face of an existing retaining wall or slope. Additionally the same should apply to new retaining walls unless it has been specifically designed to withstand the additional loads. The prevailing ground conditions under the existing building should be confirmed by an appropriately qualified person once it has been demolished. Allowances should be made for the removal of any ‘soft spots’ and their replacement with well-compacted granular materials. Department of Transport (DoT) Type 2 materials or similar could be used and should be compacted in layers to the specification for Highway Works. The National House Building Council (NHBC) Chapter 4.2 gives guidelines as to the appropriate type of floor slab and void based on the type of tree, distance of the foundation from the tree and the plasticity index of the in-situ materials. During the investigation samples of the in-situ clay was taken and submitted for plasticity testing (Annex F). In line with the NHBC (Chapter 4.2), the modified plasticity index for the sample was calculated.

Table 8.1 Plasticity Test Results

Sample Depth (m)

Soil Type Plasticity Index (%)

Passing 425µm

Sieve (%)

Modified Plasticity Index (%)

Volume Change Potential

WS01 2.00 Grey, gravelly

sandy clayey SILT 5 68 3.4 Very Low

WS04 1.00 Grey, gravelly

sandy clayey SILT 7 70 4.9 Very Low

WS06 1.20 Brown, silty clayey

gravelly SAND Non Plastic 65 - Non Plastic

Based on the above the soils on site should be assumed to have a low volume change potential and the foundations will need to penetrate a minimum of 750mm below ground level. All foundation formations should be inspected by a suitably qualified Engineer before being concreted. This is of added importance in the area of the bungalow where foundations may need to be deeper.

8.3 Excavations and Formations Excavations will be possible with normal soil excavating machinery however when dealing with historic foundations and areas of hard standing a mechanical breaker attachment will be required. Any water inflows together with rainwater infiltration should be dealt with by conventional pumping techniques. It should be noted that during times of heavy rainfall a higher water table will be encountered. Short term instabilities were seen in the boreholes and collapses of the made ground were observed. The sides of any excavations deeper than 1.0m, or shallower if unstable, should be supported by planking and strutting or other proprietary means.

March 2019 15212

8.3 Excavations and Formations (Continued) In addition to this running sand conditions may be present in more sandy deposits and allowances should be made for dealing with this scenario. The sub-formations/formations are likely to be susceptible to loosening, softening and deterioration by exposure to weather (rain, frost and drying conditions), the action of water (flood water or removal of groundwater) and site traffic. Formations should never be left unprotected and continuously exposed to rain causing degradation, or left exposed/uncovered overnight, unless permitted by a qualified engineer. Construction plant and other vehicular traffic should not be operated on unprotected formations. As a minimum the formation/excavation surfaces must be protected by blinding concrete immediately after exposure. Once again this does not apply to areas of bedrock. Allowances should be made for the removal of soft spots/areas and their replacement with well compacted granular materials.

8.4 Retaining Walls Due to the tiered nature of the site retaining walls will be required. The stability of the existing retaining walls should also be assessed by a structural engineer. This is of critical importance to the south where the wall retains Hendrecafn Road. The effective angles of shearing resistance of the materials likely to be encountered have been determined based upon past experience of the materials and are presented in Table 8.2:

Table 8.2 Effective Shear Stress Parameters Stratum Description Bulk Unit Weight

() kN/m3

Effective Cohesion

(c) kN/m2

Effective Angle of Shearing Resistance

() degrees

Soft to firm cohesive soils 18 0 20 – 25

Firm to stiff cohesive soils 18 0 30

Loose granular soils 18 0 22

Medium dense granular soils 18 0 30

Well compacted, granular materials, compacted as per Specification for Highway Works and other relevant guidance such as British Standards (BS) 6031: 1981. Code of Practise for Earthworks.

19 – 20 0 30 - 35

Fresh/slightly weathered mudstone/siltstone bedrock

19-24 5 35 - 40

Moderately / highly weathered Mudstone/siltstone bedrock

19-24 0 30 – 35

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8.4 Retaining Walls (Continued) The design and construction of the retaining walls and cut and fill should be in accordance with BS 6031: 1981 Code of Practise for Earthworks and other relevant guidance. A 45° line taken from the outermost edge of the proposed foundation should not impinge on the face of the retaining walls unless they have been specifically designed to with stand these forces. It is recommended that the construction of retaining walls be carried out in small sections. The cut face should be inspected by a suitably qualified engineer during the works to determine if any additional precautions are required. Groundwater was not encountered in the trial pits however appropriate drainage measures should be constructed behind the walls to prevent the build-up of hydrostatic pressure. If any wall is to be incorporated as part of the proposed building then suitable ‘tanking’ should be incorporated in its construction. Allowances should also be made for the removal of soft spots and their replacement with imported suitable selected inert granular materials or suitable inert site won materials. It is recommended that the temporary cut face is covered with polythene sheeting to protect the face from weathering and also to prevent any minor debris falls impacting upon the site operatives. The general condition of the temporary cut face should also be inspected on a regular basis. In addition the boundary walls and vicinity behind should be inspected for tension cracks indicative of movement of the temporary cut face.

8.5 Protection of Buried Concrete Levels of total sulphate within the in-situ materials measured between <100mg/kg to 1200mg/kg and the pH varied between 6.5 and 10.3.

When these results are compared with Table C2 of BRE Digest 1:2005, it indicates that all buried concrete should as a minimum conform to Class AC-1.

8.6 Access Roads and Car Parking Areas For access roads and car parking areas, formations within the soft shallow in-situ soils / made ground a CBR value of 1% may be used for design purposes. Where the ground conditions are more favourable and firm shallow in-situ soils were encountered a CBR value of 5% may be used. Allowances should be made for the removal of any ‘soft spots/areas’ and their replacement with well-compacted granular materials as previously described. Please note that prior to the adoption of a road the council may require in-situ CBR testing.

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8.7 Storm Water Drainage During the site investigation three soakaway tests were undertaken to the general requirements of BS 5930:2015. Due to the clayey nature of the soils negligible infiltration was observed. Irrespective of the above the addition of water into the ground on a sloping site of this nature could lead to instability issues. Soakaways may also impact the houses to the north of the site as these would be ‘downstream’ and are topographically lower than the site Soakaway drainage systems are therefore not possible or recommended on the site.

March 2019 15212

SECTION 9 Recommended Further Works The desk study has identified the potential for shallow mining to be present across the site in the No 2 Rhondda Coal Seam. To quantify the risk to the proposed development intrusive investigations will be required. It is therefore recommended that rotary boreholes are sunk across the site to confirm the underlying bedrock geology. The boreholes should be sunk to confirm a minimum of 30m bedrock. Where thick superficial deposits are encountered the boreholes may need to be taken to a greater depth. Given the proximity of neighbouring houses the works should be undertaken using water as the flushing medium. A permit from the Coal Authority for the works will also be required and this can take 4 weeks to obtain.

March 2019 15212

ANNEX A Envirocheck History Report

Order Details

Site Details

Full Terms and Conditions can be found on the following link:

Penygraig Junior School, Hendrecafn Road, Tonypandy, CF40 1LW

http://www.landmarkinfo.co.uk/Terms/Show/515

Order Number:Customer Ref:National Grid Reference:Site Area (Ha):Search Buffer (m):

192601208_1_115212 - Penygraig Junior School299540, 1919300.611000

Tel:Fax:Web:

0844 844 99520844 844 9951www.envirocheck.co.uk

Page 1 of 1A Landmark Information Group Service v50.0 30-Jan-2019

Index Map

Slice

Segment

Quadrant

Client Details

For ease of identification, your site and buffer have been split into Slices, Segments and Quadrants. These are illustrated on the Index Map opposite and explained further below.

Each slice represents a 1:10,000 plot area (2.7km x 2.7km) for your site and buffer. A large site and buffer may be made up of several slices (representedby a red outline), that are referenced by letters of the alphabet, starting from the bottom left corner of the slice "grid". This grid does not relate to National Grid lines but is designed to give best fit over the site and buffer.

A segment represents a 1:2,500 plot area. Segments that have plot files associated with them are shown in dark green, others in light blue. These arenumbered from the bottom left hand corner within each slice.

A quadrant is a quarter of a segment. These are labelled as NW, NE, SW, SE and are referenced in the datasheet to allow features to be quickly locatedon plots. Therefore a feature that has a quadrant reference of A7NW will be in Slice A, Segment 7 and the NW Quadrant.

A selection of organisations who provide data within this report:

Envirocheck reports are compiled from 136 different sources of data.

Mr A Beattie, Terra Firma (Wales) Ltd, 5 Deryn Court, Wharfdale Road, Pentwyn, Cardiff, CF23 7HB

Documents

Geotechnical & Geo-environmental Site Investigation Report ...€¦ · Trivallis Limited have requested that a Geoenvironmental Site Assessment (GSA) and Geotechnical Investigation