Proposed Residential Development East Street, Dowlais

PROPOSED RESIDENTIAL DEVELOPMENT EAST STREET, DOWLAIS

MERTHYR TYDFIL HOUSING ASSOCIATION

DESK STUDY AND PRELIMINARY RISK ASSESSMENT

Prepared for: Merthyr Tydfil Housing Association c/o Expedite Project Services 8 Village Way Greenmeadow Springs Business Park Cardiff CF15 7NE

Prepared by: Earth Science Partnership Document Ref. 6626e/2885 33 Cardiff Road Date: June 2017 Taff’s Well Status: Final Report Cardiff Revision: 0 CF15 7RB

Tel: 029 2081 3385 Fax: 029 2081 3386 e-mail: [email protected] Website: www.earthsciencepartnership.com Earth Science Partnership

PROPOSED RESIDENTIAL DEVELOPMENT EAST STREET, DOWLAIS

MERTHYR TYDFIL HOUSING ASSOCIATION

DESK STUDY AND PRELIMINARY RISK ASSESSMENT

Date Status Written By Checked and Approved By Danilo Bettosi Matthew Eynon BSc (Hons) MSc CGeol EurGeol June 2017 First Issue – Final BSc (Hons) MSc CGeol FGS FGS UK Registered Ground Engineering Specialist

Signature

ESP.6626e.2285 2 June 2017 East Street, Dowlais Earth Science Partnership PROPOSED RESIDENTIAL DEVELOPMENT EAST STREET, DOWLAIS

GEO-ENVIRONMENTAL DESK STUDY ASSESSMENT

CONTENTS

1.0 INTRODUCTION AND OBJECTIVES...... 5 2.0 DESK STUDY AND FIELD RECONNAISSANCE VISIT ...... 7 2.1 Site Location and Description ...... 7 2.2 Site History ...... 8 2.3 Previous Investigations and Assessments ...... 9 2.4 Contact with Regulatory Bodies & Local Information Sources ...... 9 2.5 Hydrology ...... 10 2.6 Geology ...... 10 2.7 Hydrogeology ...... 11 2.8 Environmental Setting ...... 12 2.9 Preliminary Geotechnical Risk Register ...... 13 3.0 PRELIMINARY GEO-ENVIRONMENTAL RISK ASSESSMENT ...... 18 3.1 Phase One Conceptual Site Model ...... 18 3.2 Preliminary Risk Evaluation & Plausible Pollutant Linkages ...... 20 4.0 PRELIMINARY GEOTECHNICAL RISK ASSESSMENT ...... 22 4.1 Anticipated Geotechnical Hazards ...... 22 5.0 RECOMMENDATIONS ...... 24 5.1 Proposed Development ...... 24 5.2 Exploratory Ground Investigation ...... 24 6.0 REFERENCES ...... 25

ESP.6626e.2285 3 June 2017 East Street, Dowlais Earth Science Partnership PROPOSED RESIDENTIAL DEVELOPMENT EAST STREET, DOWLAIS

GEO-ENVIRONMENTAL DESK STUDY ASSESSMENT

ENCLOSURES

PLATES

FIGURE 1 Site Location Plan

FIGURE 2 Site Plan

FIGURE 3 Extract from BGS Sheet SO OO NE

FIGURE 4 Conceptual/Geological Cross Section

APPENDIX A Risk Assessment Criteria

APPENDIX B Extracts from Historical Maps

APPENDIX C Enviro-Insight Environmental Data Report

APPENDIX D Borehole Records Available from the British Geological Survey (BGS, 2016)

APPENDIX E Coal Authority Mining Report

APPENDIX F Preliminary UXO Risk Assessment (Zetica, 2017)

GENERAL NOTES

ESP.6626e.2285 4 June 2017 East Street, Dowlais Earth Science Partnership 1.0 INTRODUCTION AND OBJECTIVES

1.1 Background

Merthyr Tydfil Housing Association (hereafter known as the Client) are proposing to redevelop the subject site for residential purposes. The Earth Science Partnership Ltd (ESP), Consulting Engineers, Geologists and Environmental Scientists, were instructed by the Client, via Expedite Project Services, to undertake an integrated geotechnical and geo-environmental Desk Study assessment to identify and evaluate potential ground hazards which could impact on the proposed development. The site location is shown on Figure 1.

The proposed development will comprise the construction of residential properties with associated areas of landscaping and hardstanding. Based on the above, we understand that the proposed structures would be classified as Geotechnical Category 2 (BS5930:2015).

1.2 Objective and Scope of Works

The objective of the investigation was to obtain information on the geotechnical character and properties of the ground beneath the site, potential risks posed by contamination and ground gas, and to allow an assessment of these ground conditions with particular reference to the potential impact on the proposed development. We are not, at present, aware of any ground hazard related planning conditions relating to the development.

The scope of works for the investigation was mutually developed with the Client by ESP within an agreed budget, and comprised a desk study review of available historical Ordnance Survey maps, environmental data, geological maps, memoirs and data, and further desk study information and interpretive reporting.

The contract was awarded on the basis of a competitive tender quotation. The terms of reference for the assessment are as laid down in the Earth Science Partnership email proposal of 23 rd March 2017. The assessment was undertaken in May and June 2017.

1.3 Report Format

This report includes the desk study and field reconnaissance reports (Section 2) along with the Preliminary Risk Assessment stage (Section 3). However, it should be appreciated that this is a preliminary evaluation only, and will not generally meet the requirements of the Options Appraisal report of CLR11.

A preliminary risk register, identifying potential geotechnical hazards from the desk study review, is presented as Section 2.9.

The assessment of the potential for hazardous substances (contamination) or conditions to exist on, at or near the site at levels or in a situation likely to warrant mitigation or consideration appropriate to the proposed end use has been undertaken using the guidance published by CIRIA (2001). This is discussed in more detail in Section 3.2.1 and in Appendix A.

ESP.6626e.2285 5 June 2017 East Street, Dowlais Earth Science Partnership

1.4 Limitations of Report

This report represents the findings of the brief relating to the proposed end use and geotechnical category of structure(s) as detailed in Section 1.1. The brief did not require an assessment of the implications for any other end use or structures, nor is the report a comprehensive site characterisation and should not be construed as such. It should be appreciated that no intrusive investigation has been undertaken to date. Should an alternative end use or structure be considered, the findings of the assessment should be re-examined relating to the new proposals.

Where preventative, ameliorative or remediation works are required, professional judgement will be used to make recommendations that satisfy the site-specific requirements in accordance with good practice guidance.

Consultation with regulatory authorities will be required with respect to proposed works as there may be overriding regional or policy requirements which demand additional work to be undertaken. It should be noted that both regulations and their interpretation by statutory authorities are continually changing.

This report represents the findings and opinions of experienced geo-environmental and geotechnical specialists. Earth Science Partnership does not provide legal advice and the advice of lawyers may also be required.

1.5 Digital Copy of Report

This report is issued as a digital version only.

ESP.6626e.2285 6 June 2017 East Street, Dowlais Earth Science Partnership 2.0 DESK STUDY AND FIELD RECONNAISSANCE VISIT

The information presented in this section was obtained from desk-based research of sources detailed in the text, including historical maps (Appendix B), an environmental data report (Appendix C) and a mining report obtained from the Coal Authority (Appendix E). Further desk study reports/data/records are included as subsequent appendices where required and referenced in the text.

2.1 Site Location and Description

The site is located off East Street within the village of Dowlais, approximately 2 miles north east of the town centre of Merthyr Tydfil. The National Grid Reference of the centre of the site is (SO) 306717, 207811 and the postcode is believed to be CF48 3LB. A Site Location Plan is presented as Figure 1.

The site comprises a roughly inverted ‘L’ shaped parcel of land of around 60m in length (west to east) and 45m width (north to south) at its largest points occupying an area of around 0.2ha and is bounded by: · To the north: Immediately by a residential dwelling followed by Upper Union Street, Dowlais Library and associated parking areas; · To the east: Immediately by Commercial Road, gardens and properties associated with Dowlais; · To the south: Immediately by East Street and residential properties; · To the west: immediately by open ground, followed by Church Street and Dowlais Library.

A site walkover was undertaken on 15th May 2017 and identified the site to comprise a currently vacant plot, bounded by East Street, Commercial Street and Upper Union Street.

A number of large shrubs/semi mature trees are present on site, with the rest of the site laid to long overgrown grass. A substation has been identified at the south west boundary, with some fly tipped materials identified at the south boundary.

The site slopes southward from Upper Union Street toward East Street, with steep slopes noted at the west, south and south-east boundaries. We are not aware of a topographic survey for the site at this time, however recent Ordnance Survey maps (Appendix A) indicate a spot height of 303.5mAOD on Church Street, immediately to the south west of the site and 309.7mAOD to the east on Commercial Street.

ESP.6626e.2285 7 June 2017 East Street, Dowlais Earth Science Partnership 2.2 Site History

2.2.1 Published Historical Maps

The site history has been assessed from a review of available historical Ordnance Survey County Series and National Grid maps. Extracts from the historical maps are presented in Appendix B and the salient features since the First Edition of the County Series maps are summarised in Table 1 below.

Table 1: Review of Historical Maps Date On-Site In Vicinity of Site 1875 The site is indicated to be occupied by Residential dwellings surround the site to the west residential housing and two Public and south. A Market House is present to the east and Houses that occupy the boundaries of the Dowlais Church present to the north west. The site, with the central portion occupied by Dowlais iron company stables, with associated sidings gardens and out buildings. are indicated approximately 50m north east. Dowlais Station is located approximately 150m north west, along with a goods shed and associated sidings of the Brecon Merthyr railway line. Dowlais Ivor Iron Works are indicated approximately 310m north, along with its associated sidings and outbuildings. Dowlais Iron Works are indicated approximately 200m south. An air shaft is indicated 200m south. 1899 - No significant changes are indicated. A library is now indicated approximately 30m west of 1920 the site. A smithy is indicated approximately 70m south east of the site. The station and iron works (north and south of the site) have expanded. The air shaft to the south is no longer indicated 1956 No significant changes are indicated. Numerous ruins are indicated within the general vicinity. The stables and market house are no longer indicated as such. A ruin now exists within the stables footprint, with a factory and Police Station now being indicated in the area of the former Market House. A tank is located 25m to the north. Dowlais Iron works is no longer indicated to the south and has been replaced with factories. Areas of earthworks are now located in the areas of the former railway lines and sidings. 1961 - No significant changes are indicated. The station to the north is now indicated as disused 1966 with the associated railway lines being indicated as dismantled. Numerous new industrial buildings along with additional tanks are now indicated to the north in the location of the former iron works. 1974 – No significant changes are indicated. The factory located within the footprint of the former 1974 market is longer indicated. The stables to the west have been demolished. Residential dwellings approximately 60m to the south east have been demolished and Victoria Street is now present. A substation is indicated at the south west boundary.

ESP.6626e.2285 8 June 2017 East Street, Dowlais Earth Science Partnership

Table 1: Review of Historical Maps (Cont.) 1983 – The site is now indicated to be vacant Large scale demolition has occurred in the general 1993 area including the dwellings associated with Ivor Street to the north, Church Row to the east and Upper Union street south. New dwellings have been constructed along the north boundary with wider redevelopment occurring throughout the area. 1995 – No significant changes. No significant changes. Present (limited data)

2.2.3 Archaeological Setting

A full archaeological assessment was not included within the brief, but we have not been advised of, or identified, any obvious evidence of any significant archaeological features on the site as part of the walkover or historical map review.

2.3 Previous Investigations and Assessments

ESP undertook an investigation approximately 40m to the north within the grounds of the existing St Johns Church. A series of windowless sample drillholes, trial trenches and rotary boreholes were undertaken and encountered a covering of Made Ground throughout the site, increasing in thickness in a southerly direction to a maximum depth of 1.6m. The Made Ground consisted of an upper coarse grained soil with varying quantities of ash and slag followed by a layer of re-worked glacial soils. The Made Ground was underlain by thick fine grained glacial deposits, proven to approximately 27m.

Coal Authority information and available geological information obtained during the assessment indicated that there is no risk of shallow coal mining beneath the site. Extensive iron workings were identified to have occurred in the general area and the Coal Authority provided information to indicate there is a potential for shallow ironstone workings beneath the south east corner of the site. Subsequent rotary drilling was undertaken at four locations within the church and no anomalous ground conditions or voids were recorded during the drilling of the Glacial Till or bedrock.

2.4 Contact with Regulatory Bodies & Local Information Sources

The following departments of the Local Authority (Rhondda Cynon Taff Council) have been contacted as part of this assessment: · Environmental Services/Health/Pollution Control · Building Control · Trading Standards (Petroleum Officer)

At the time of issue of this report, we have not yet received a response from the consultees. Once received, any response will be forwarded under separate cover. It should be appreciated that their responses may contain salient information on the site which could not be taken into account during the preparation of this report.

ESP.6626e.2285 9 June 2017 East Street, Dowlais Earth Science Partnership

2.5 Hydrology

2.5.1 Surface Water Features

The nearest major surface water feature to the site is the River Taff which flows from north to south >1km to the west of the site.

2.5.2 Surface Water Abstractions

The environmental data report (Appendix C) indicates that there are no surface water abstractions within 250m of the site.

2.5.3 Flooding (Rivers and Seas)

From a review of topographical plans and flooding maps presented on the Natural Resources Wales website (May 2017), the site is not indicated to be at risk from flooding from rivers or seas.

2.5.4 Flooding (Groundwater)

The Groundsure Report (Appendix C) identifies the site as at risk of groundwater flooding from superficial deposits which may flood at the surface. A high confidence rating is provided in this assessment. No further assessment of groundwater flooding has been instructed as part of this scope of works, but may be required as part of detailed design as it may impact on the geotechnical aspects of the development.

2.6 Geology

2.6.1 Published Geology

The published geological map for the area of the site (1:10,560 scale, SO 00 NE) indicates the site to be underlain by Glacial Diamicton overlying bedrock of the Lower Coal Measures. The Glacial Till superficial strata would be expected to be fine-grained in nature with some gravel, and possibly cobbles and boulders. The Coal Measures bedrock comprises an interbedded succession of sandstones, siltstones and mudstones, with coal seams and associated seat earths.

Large areas of Made Ground are indicated approximately 500m north and approximately 350m south of the site associated with the former iron works and railway sidings (see Section 2.2). We cannot discount that Made Ground will be present on-site associated with likely earthworks undertaken as part of the demolition of historical properties and redevelopment of the site and adjacent areas.

The bedrock underlying the site is situated near the base of the Lower Coal Measures succession, with the conjectural top of the ‘Farewell Rock’, a thick succession of sandstones indicated approximately 200m to the north. The bedrock is indicated to dip approximately between 8º and 20º to the south east (downhill from the site). The Dowlais fault, trending northwest-southeast, is indicated approximately 550m south west.

ESP.6626e.2285 10 June 2017 East Street, Dowlais Earth Science Partnership

The geological map indicates the conjectural outcrop of the Gellideg coal seam to strike north east to south west some 400m to the south of the site. The Garw coal seam is indicated to be located below the Gellideg (but not identified on the geological map) would be approximately at the south boundary based on the regional dip. Based on the above and the known geological succession for the Lower Coal Measures we do not anticipate that there are any significant coal seams beneath the site, however, the Garw is likely to have been present just to the south and worked south east from the crop. Ironstone workings are indicated to the south of the site and available on line information indicates the ironstone workings are also present below the site (see Insert 1 and Section 2.9.3).

2.6.2 Available BGS Borehole Records/Previous Investigation

The nearest borehole to the site recorded on the BGS website is located at SO 0667 0790 approximately 40m north west of the site. The ground conditions consisted of Made Ground to a depth of 0.5m followed by soft (to 0.8m) becoming firm to very stiff, probable Glacial Diamicton to 15m. The Glacial Diamicton was described as a brown silty sandy to very sandy clay with gravel and occasional coal fragments. A copy of the available borehole record is presented in Appendix D.

2.7 Hydrogeology

2.7.1 Aquifer Classification

Reference to the aquifer maps published on the environmental data report/Environment Agency website (EA, 2016) indicates that the superficial deposits beneath the site (Glacial Diamicton) are classed as Unproductive Strata, whilst the bedrock (Lower Coal Measures) is classed as a Secondary A Aquifer. Groundwater movement within the diamicton will be controlled by intergranular flow, whilst in the Lower Coal Measures bedrock fracture flow is likely to be dominant.

Secondary A Aquifers generally correspond with the previously classified minor aquifers, and comprise permeable layers capable of supporting water at a local, rather than strategic, scale and in some cases form an important base flow to rivers. Secondary A Aquifers are sensitive to pollution. Unproductive Strata are bedrock or drift deposits of low permeability, which have negligible significance for water supply or river base flow. Unproductive Strata are the least sensitive in terms of pollution. The Groundsure Report indicates that there are no groundwater abstractions or Source Protection Zones within 1km of the site. It should be appreciated that in former mining areas, such as this, groundwater conditions may still be changing in response to the cessation or reduction in pumping from underground coal workings.

2.7.2 Anticipated Groundwater Bodies

Based on the available information, we consider that the shallowest main groundwater body is likely to be located within the Glacial Till deposits. However, localised perched water bodies within the overlying Made Ground cannot be discounted. The Groundsure Report (Appendix C) identifies the site as at risk of groundwater flooding from superficial deposits which may flood at the surface. A high confidence rating is provided in this assessment. Deeper groundwater bodies are likely to be present with the Coal Measures bedrock.

ESP.6626e.2285 11 June 2017 East Street, Dowlais Earth Science Partnership

2.7.3 Abstractions and Groundwater Vulnerability

The Groundsure Report and the groundwater resource maps on the EA website (EA, 2017) indicate that there are no groundwater abstractions or Source Protection Zones within 1km of the site. It should be appreciated that in former mining areas, such as this, groundwater conditions may still be changing in response to the cessation or reduction in pumping from underground coal workings.

2.7.4 Groundwater Movement

Groundwater movement within the Glacial Till deposits will be controlled by intergranular flow whilst, in the Coal Measures, fracture flow is likely to be dominant. It should be appreciated that in former mining areas, such as this, groundwater conditions may still be changing in response to the cessation or reduction in pumping from underground coal workings.

2.8 Environmental Setting

2.8.1 Summary of Environmental Data

The site exists in a historically industrial, and now an urban setting. Environmental data for the vicinity of the site has been obtained via a Groundsure Report, which is presented in Appendix B. The salient data is summarised in Table 2 below.

Table 2: Summary of Groundsure Data Item On the Site In the Immediate Vicinity Sensitive Land Uses None identified within the None identified. (SSSI, Nature Groundsure report. Reserves, SAC etc.) Environmental permits, None identified within the 2no. recorded within 250m of site, relating to: incidents and registers Groundsure report. · Significant impact on air quality, from atmospheric pollutants, described as Landfill odour, 152m north east in March 2002; · Minor impact on air quality, from atmospheric pollutants, described as Effects on humans, 82m east in March 2002. Potentially Infilled None identified within the 19no. identified within 250m including: Land Groundsure report. · A graveyard, reservoir, burial ground, unspecified heaps and unspecified ground workings and pits are indicated between 9m and 200m to the south east, associated with the former iron works. Landfill and other None identified within the None identified within 400m of the site. However, large waste Groundsure report. areas of Made Ground have been identified to the north and south of the site associated with former industrial uses and filling.

ESP.6626e.2285 12 June 2017 East Street, Dowlais Earth Science Partnership

Table 2 Cont: Summary of Groundsure Data Potentially None identified within the 111no. identified within 250m including; Contaminative uses Groundsure report, · Approximately 37m to 100m north, extensive however the site has railways sidings, good sheds and works associated previously been developed. with the former iron works and railway station and subsequent industrial developments; · Approximately 100m to 200m to the south, extensive railway lines, an unspecified mill, heaps and ground workings associated with the former iron works and then factories after the areas redevelopment. Historic Tanks None identified within the 19no. identified within 250m the closest of which was an Groundsure report. unspecified tank 150m north (1956) Discharge Consents None identified within the None identified. Groundsure report. Historical Energy None identified within the 1no. identified within 150m, as an electric substation 44m Features Groundsure report. south east.

2.9 Preliminary Geotechnical Risk Register

2.9.1 Summary of Potential Geotechnical and Geomorphological Hazards

The potential for various geotechnical and geomorphological hazards at the site is provided in the environmental data (Appendix C). The potential hazards, as reported in these reports are listed in Table 3 below, along with any salient further information on the potential hazard identified by ESP in the preparation of this report. Where a potential hazard has been identified, it is discussed further in subsequent sections.

Table 3: Natural Hazards Ground Stability Hazard Potential1 ESP Comment ESP do not concur with this assessment – see Section Coal Mining No hazard 2.9.2. ESP do not concur with this assessment – see Section Mining (non-coal) Very Low 2.9.3. ESP do not concur with this assessment– see Section Shrinking or Swelling Clay Very Low 2.9.4. ESP do not concur with this assessment – see Section Landslide Very Low 2.9.5. No further information identified to contradict Ground Dissolution Negligible environmental data report. ESP do not concur with this assessment– see Section Compressible Ground Negligible 2.9.6. No further information identified to contradict Collapsible Ground Very Low environmental data report. No further information identified to contradict Running Sand Very Low environmental data report.

ESP.6626e.2285 13 June 2017 East Street, Dowlais Earth Science Partnership

Table 3 Cont: Natural Hazards Radon - See Section 2.9.7. Volumetrically Unstable Not reported. See Section 2.9.8. Slag Sulphate/Pyritic Ground Not reported. See Section 2.9.9.

Unexploded Ordnance Not reported. See Section 2.9.10. Notes on Table 3: 1. Potential as reported in environmental data report (Appendix C). 2. Salient hazards discussed in following sections.

2.9.2 Past Coal Mining

As discussed in Section 2.4.1, the site is underlain by bedrock of the Lower Coal Measures, which contains several seams of coal (and bands of ironstone). As part of the desk study a mining report has been obtained from the Coal Authority and is presented in Appendix E. This indicates that based on the available Coal Authority records: · The property is not in the likely zone of influence from shallow coal workings; · The property is in the likely zone of influence from shallow ironstone workings, last worked in 1878; · No notice of the risk of the land being affected by subsidence has been given; · The property is not within the likely zone of influence of any present underground coal workings. With no recorded claims within 50m of the site boundary; · There are no known coal mine entries within, or within 20m of, the boundary of the site.

As discussed in Section 2.4.1, the bedrock underlying the site is situated near the base of the Lower Coal Measures succession. Considering the general dip direction of the strata to the south/southeast within the region (away from the site), and the absence of any significant coal seams beneath the site (due to its location just above the Farewell Rock and the Garw recorded to the south) we consider that there is a low risk from coal mining beneath the site. No further discussion is required in this regard.

2.9.3 Past Mining (Non Coal / Ironstone)

Extensive iron workings are known to have occurred in the general area and have been encountered at shallow depth beneath the Goat Mill Road industrial development approximately 200m to the south.

The Coal Authority online resources present further information on the ironstone workings indicated to be present at shallow depth beneath the site. A plan indicating the extent of known ironstone workings in the area is presented as Insert 1 with the recorded outcrop of the Garw seam and site location also presented.

ESP.6626e.2285 14 June 2017 East Street, Dowlais Earth Science Partnership

Probable Garw Outcrop

Extent of Iron Workings

Insert 1: Extent of Shallow Ironstone Workings

The plan indicates there is a potential for shallow ironstone workings beneath the site and likely relate to the Rosser Ironstone seams that occur in conjunction with the Garw Coal Seam. The iron workings in the area are generally recorded to have been worked from the crop, therefore considering the regional stratigraphy and the conjectural extent of the ironstone (Insert 1), any potential workings would have progressed away from the site to the south-east and are unlikely to have progressed under the site, unless the ironstone was present as an outcrop within the site boundary.

The Coal Authority report indicates the workings were last worked in 1878, however historical records indicate that properties were present on the site from at least 1875 (earliest available mapping) which further reduces the likelihood of on-site ironstone workings.

Whilst the available evidence of the risk posed by ironstone workings indicates probable absence, this will require confirmation and the risk at present considered Moderate.

2.9.4 Shrinkable and Swelling Soils

Fine grained glacial deposits are anticipated beneath the site, which can potentially have a high plasticity index and, hence, be classified as of high volume change potential with changes in moisture content (shrinkage and swelling). We consider that the potential for shrinkable and swelling clays at the site should be increased from that reported in the environmental data report (Table 3, very low) to Moderate.

ESP.6626e.2285 15 June 2017 East Street, Dowlais Earth Science Partnership

2.9.5 Landslips

Study of the available mapping data (South Wales Coalfield Landslip survey, 1980, page 6) and reference to the Groundsure report, indicates that landslips have not occurred within the immediate area.

However based on the locality of the site on a steep sided valley, potentially thick glacial deposits and steep slopes present on site, we cannot discount that there is a potential risk of landsliping in the area. We consider that the potential for landslides at the site should be increased from that reported in the environmental data report (Table 3, No hazard) to Low.

2.9.6 Compressibility

Fine grained glacial soils are anticipated at shallow depths underlying the site which can be susceptible to compression. We consider that the potential for compressibility at the site should be increased from that reported in the environmental data report (Table 3, Negligible) to Moderate.

2.9.7 Radon Hazard

Radon is a colourless, odourless, radioactive gas, which can pose a risk to human health. It originates in the bedrock beneath the site, where uranium and radium rich minerals are naturally present, and can move through fractures in the bedrock, and overlying superficial deposits, to collect in spaces within/beneath structures.

The environmental data report (Appendix C) indicates that the site lies in a radon affected area as defined by the Health Protection Agency, with <1% of properties above the action level and no radon protection measures required.

2.9.8 Volumetrically Unstable Slag

The potential for volumetrically unstable slag material to be present on the site is not considered in the environmental data report.

In our experience, on former industrial site such as this, there is the potential for slag materials to be present within Made Ground. There are a number of chemically different types of slag found on brownfield sites across the UK. Some forms of slags are volumetrically stable but, depending on their chemistry, some can be extremely unstable when hydrated, which can lead to significant heave at the surface and damage to buildings and hard surfaces. Given the currently available information, the presence on site of slag within the shallow Made Ground cannot be discounted, and the risk from unstable slag is considered Moderate.

ESP.6626e.2285 16 June 2017 East Street, Dowlais Earth Science Partnership

2.9.9 Pyritic Ground

The environmental data report does not consider the potential risk from sulphate rich or pyritic ground. The Glacial Deposits and anticipated Made Ground, coupled with the iron bearing rock underlying the site could potentially contain elevated levels of pyrite, which may oxidise to sulphates and lead to aggressive attack on buried concrete.

Given the above, at this stage (without laboratory analysis) we consider that the potential for sulphate/pyrite attack on buried concrete would be Moderate.

2.9.10 Buried Unexploded Ordnance (UXO)

The environmental data report does not consider the potential risk from unexploded ordnance at the site. A Preliminary UXO Desk Study assessment of risk has been completed by a specialist Ordnance consultant in accordance with CIRIA guidelines (Stone et al, 2009) and is presented in Appendix E (Zetica, 2016). This indicates that no readily available records of bombing or other military activity on the Site have been found. It is considered that the site is likely to have a low Unexploded Ordnance (UXO) hazard level. Whilst a detailed desk study, whilst always prudent, is likely to do no more than confirm a low UXO hazard level for the Site. Given the above, we consider that the potential for unexploded ordnance beneath the site would be Low.

ESP.6626e.2285 17 June 2017 East Street, Dowlais Earth Science Partnership 3.0 PRELIMINARY GEO-ENVIRONMENTAL RISK ASSESSMENT

3.1 Phase One Conceptual Site Model

3.1.1 Background

The Phase One Conceptual Site Model lists the potential sources of geo-environmental risk, the receptors at risk and the pathways between the two.

3.1.2 Potential Sources of Soil/Water Contamination

Potential Contamination Sources:

Although no contaminative former use has been identified for the site, it has been previously developed with residential properties and Public Houses and is in an area of historical urban and industrial development. Therefore, we anticipate that there could be a covering of Made Ground, which could contain contaminants.

Potential Contaminants Present:

The potential contaminants associated with the above potential sources have been identified from various guidelines published by DEFRA, the Environment Agency and others. The particular guidance referenced includes the Industry Profile for Railway Land (DoE, 1995). Based on this guidance and our experience, we consider that the following contaminants could be present on the site: • heavy metals and semi-metals (arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, vanadium, zinc); plus other metals. • cyanide, sulphate, sulphide; • polyaromatic hydrocarbon (PAH) compounds; • petroleum hydrocarbons, including methyl-tert-butyl-ether (MTBE); • phenols; • asbestos.

No evidence has been identified from the desk study to suggest that radioactive substances may be present on the site.

3.1.3 Potential Sources of Hazardous Ground Gas

Based on the available information, the following may prove potential sources of hazardous ground gas on or close to the site: • Made Ground, both within the site boundary and the local neighbouring area; • Potential shallow ironstone workings in neighbouring areas to the south; • Industrial heritage of local area, particularly pre mapping data.

Based on the guidelines presented by Wilson et al (2009), the above potential gas sources would generally be classified as of low/moderate gas generation potential.

ESP.6626e.2285 18 June 2017 East Street, Dowlais Earth Science Partnership

3.1.4 Potential Sources of Radon

The BRE Report BR211 (2007) classifies the risk from radon, based on the underlying geology. Radon is a colourless, odourless, radioactive gas, which can pose a risk to human health. It originates where uranium and radium are naturally present in the bedrock and can move through fractures in the bedrock and overlying superficial deposits to collect in spaces in structures. The site lies in an area identified by the BRE where there is a low risk from radon (<1% of properties affected).

3.1.5 Potential Receptors

As discussed in Section 1.1, the proposed site development will comprise residential properties with private gardens, landscaping and vehicle parking areas. Given the above, we consider that the most vulnerable receptors with regards to any contamination or hazardous ground gas present are likely to be as follows. · Future residents, the critical receptors being young children playing in private garden areas. · Construction and maintenance workers. · Buried concrete (foundations, drainage etc.). · The water quality in local surface waters, however the River Taff is not considered to be within influencing distance. · The groundwater within the Coal Measures strata beneath the site.

3.1.6 Potential Migration Pathways

Based on the Conceptual Site Model discussed in the previous sections, the following are considered the most likely migration pathways with regard to any contamination or hazardous ground gas present beneath the site.

Site Users: · Ingestion of soils and inhalation of dust in garden areas. · Ingestion of soils and inhalation of dust in landscaping areas. · Ingestion of edible plants and dust associated with such plants. · Dermal contact with contaminated soils. · Exposure to asbestos containing materials within the shallow soils. · Potential explosive risk from flammable ground gas/vapours from on-site sources. · Potential risk from toxic ground gas/vapours from on-site sources. · Potential exposure to flammable or toxic ground gas/vapours originating from off-site sources.

Construction and Maintenance Workers: · Exposure to asbestos containing materials within the existing buildings. · Exposure to asbestos containing materials within the shallow soils. · Ingestion of soils and inhalation of dust across site. · Dermal contact with contaminated soils. · Potential explosive risk from flammable or toxic ground gas/vapours from on-site sources. · Potential explosive risk from flammable or toxic ground gas/vapours from off-site sources.

ESP.6626e.2285 19 June 2017 East Street, Dowlais Earth Science Partnership

Groundwater/Surface Waters: · Leaching of mobile contaminants into the water-bearing strata within the bedrock. · Movement of mobile contaminants into minor surface waters. Impact on River Taff not anticipated.

Buildings: · Sulphate attack on buried concrete (foundations, drainage etc.). · Potential explosive risk from flammable ground gas/vapours from on-site sources. · Potential explosive risk from flammable ground gas/vapours from off-site sources.

3.2 Preliminary Risk Evaluation & Plausible Pollutant Linkages

The land use history of the site and surrounding area, as established from the desk study and walkover, has identified a number of potential contamination linkages due to ground conditions or former operations either on, adjacent to, or in the vicinity of the site. Note that these potential linkages will need to be later assessed and re-established using actual site data obtained from an exploratory investigation.

3.2.1 Introduction to Risk Evaluation Methodology

The methodology set out in CIRIA C552 Contaminated Land Risk Assessment – A Guide to Good Practice (Rudland et al, 2001), has been used to assess whether or not risks are acceptable, and to determine the need for collating further information or remedial action.

Whilst at a later stage, this methodology may be informed by quantitative data (such as laboratory test results) the assessment is a qualitative method of interpreting findings to date and evaluating risk. The methodology requires the classification of: · The magnitude of the potential consequence (severity) of risk occurring (Table A1 in Appendix A): · The magnitude of the probability (likelihood) of risk occurring (Table A2 in Appendix A).

The classifications defined above are then compared to indicate the risk presented by each pollutant linkage, allowing evaluation of a risk category (Tables A3 and A4 in Appendix A). These tables have been revised slightly from those presented in CIRIA C552, to allow for the circumstances where no plausible linkage has been identified and, therefore, no risk would exist.

The methodology described above has been used to establish Plausible Pollutant Linkages (PPL) based on the Conceptual Site Model generated for the site and proposed development, and to evaluate the risks posed by those linkages, using information known about the site, at this desk study stage. This is presented as Table ?? in Section 3.2.2 below.

ESP.6626e.2285 20 June 2017 East Street, Dowlais Earth Science Partnership 3.2.2 Tabulated Preliminary Risk Evaluation & Plausible Pollutant Linkages Table 4: Preliminary Risk Evaluation & Plausible Pollutant Linkages (PPL). Source Pathway Receptor Classification of Classification of Risk Category Further Investigation or Consequence Probability Remedial Action to be Taken Direct contact/ inhalation/ ingestion of Medium – potential for Site Users/Visitors Likely2 Moderate Risk contaminated soil or chronic levels. dust Potential contaminants in Made Direct contact/ Ground on site from previous inhalation/ ingestion of Construction/ Minor – standard PPE Moderate/Low Likely2 Sampling of near-surface soils to development including sources contaminated soil or Maintenance Workers likely to be sufficient Risk confirm levels of total such as previous development dust contamination present. and local historical Impact on development. Leaching of soil Groundwater Medium – site lies on a Likely2 Moderate Risk contaminants underlying Secondary Secondary A Aquifer Aquifer Leaching of soil Impact on surface Medium Low Likelihood2 Moderate Risk contaminants waters. Aggressive Mild – damage to Sampling of soils to confirm levels Soil sulphate Buried Concrete High likelihood3 Moderate Risk groundwater structures of sulphate and pH. Demolition/ Medium – potential for Asbestos Ingestion of fibres Low Likelihood4 Moderate Risk Sampling of shallow soils. Construction Workers chronic levels Asphyxiation/poisoning. Site Users/Visitors. Severe – acute risk. High Risk Hazardous ground gas risk from Injury due to explosion. on site Made Ground, local Damage through Building/Property Severe – acute risk. High Risk historical development and explosion. Likely5 Install and monitor gas wells. historic ironstone workings to Construction and Asphyxiation/poisoning. south. Maintenance Severe – acute risk. High Risk Injury due to explosion. Workers. Groundsure Report identifies low Site Users (Full time Medium – potential for Radon gas Migration into Buildings Unlikley6 Low Risk risk with no protection measures employees) chronic levels required. Notes: 1. Methodology and details of risk consequence, probability and category based on CIRIA C552 (2001) and presented in Section 3.2.1. 2. The presence of Made Ground or contamination has not yet been confirmed on site. 3. The underlying soils can potentially contain sulphates/pyrite (Section 2.8). 4. Potential for asbestos containing materials in existing buildings and underlying Made Ground. 5. Potential source of hazardous ground gas/vapours at the site (Section 3.1.3). 6. Radon risk identified in environmental data report (Section 3.1.4).

ESP.6626e.2285 21 June 2017 East Street, Dowlais Earth Science Partnership 4.0 PRELIMINARY GEOTECHNICAL RISK ASSESSMENT

4.1 Anticipated Geotechnical Hazards

4.1.1 Past Mining (Coal)

4.1.2 Past Mining (Non Coal / Ironstone)

The plan indicates there is a potential for shallow ironstone workings beneath the site and likely relate to the Rosser Ironstone seams that occur in conjunction with the Garw Coal Seam. The iron workings in the area are generally recorded to have been worked from the crop, therefore considering the regional stratigraphy and the conjectural extent of the ironstone, any potential workings would have progressed away from the site to the south-east and are unlikely to have progressed under the site, unless the ironstone was present as an outcrop within the site boundary.

Whilst the available evidence of the risk posed by ironstone workings indicates probable absence, this will require confirmation as part of intrusive investigation works.

4.1.3 Site Stability

The site is recorded to have been historically developed with housing, with slopes present on three boundaries. Due to the potential presence of Made Ground, historic basements and recorded coal/ironstone outcrops immediately to the south of the site, an assessment of stability will be required.

4.1.4 Shrinkable and Swelling Soils

Fine grained soils are anticipated to be present within the Made Ground and natural Glacial deposits and the potential shrinking and swelling of these soils poses a risk to future development. The plasticity of these soils will have to be considered as part of any intrusive works.

4.1.5 Compressible Ground

Based on the information available to date, there is a potential risk to the site, from compressible soils that are likely to be present between within the Made Ground and any near surface fine Glacial Deposits. The compressibility of these soils will need to be considered as part of any proposed future development.

ESP.6626e.2285 22 June 2017 East Street, Dowlais Earth Science Partnership

4.1.6 Pyritic Ground

The environmental data report does not consider the potential risk from sulphate rich or pyritic ground. Extensive Made Ground is anticipated to underlie the site and could potentially contain elevated levels of pyrite, which may oxidise to sulphates and lead to aggressive attack on buried concrete. Given the above, at this stage (without laboratory analysis) we consider that there is a potential risk posed to the site and any future development.

4.1.7 Volumetrically Unstable Slag

4.1.8 Invasive Species

An assessment of invasive species was not required as part of this assessment, however, species like Japanese Knotweed and Himalayan Knotweed are common on redevelopment sites and have potentially been identified in the south portion as part of the walkover. As part of the development works, the potential for the presence of invasive species should be considered.

4.1.9 Potential Foundation Options

Based on the available geological information, it is likely that traditional foundations will be unsuitable and alternative options will need to be considered such as lightly loaded rafts, however this will be addressed further upon confirmation of the ground model.

4.1.10 Groundwater Flooding

The Groundsure Report identifies the site as at risk of groundwater flooding from superficial deposits which may flood at the surface. A high confidence rating is provided in this assessment. This will require consideration as part of detailed design as shallow groundwater may impact on the proposed development and structure.

ESP.6626e.2285 23 June 2017 East Street, Dowlais Earth Science Partnership 5.0 RECOMMENDATIONS

5.1 Proposed Development

We understand that the site development is to comprise the construction of a residential dwellings with associated areas of landscaping and hardstanding. In order to progress the development it will be necessary to implement a ground investigation in order to satisfy the requirements of the modern development standards.

5.2 Exploratory Ground Investigation

The scope of works for the investigation will depend on the nature of the future development and an intrusive investigation would be required to confirm the Conceptual Ground Model considering the risks from any contaminants present, and geotechnical hazards. In particular, the investigation should be designed to provide information on the following: · The presence and make up of Made Ground across the site; · The levels of total soil contaminants in the shallow soils and/or Made Ground; · The levels of soil sulphate and whether pyrite is likely to be present; · The volume change potential and/or compressibility including potential for slag to be present; · The potential for ground gas; · Presence of invasive species; · Monitoring of groundwater levels, to determine the potential for shallow groundwater; · Preliminary assessment of the potential for on-site ironstone workings through trial pitting and/or rotary drilling.

Further guidance on these requirements and scope of intrusive investigations, can be provided by this office once development proposals have been finalised. It should be noted that dependant on the arising conditions identified as part of the exploratory (preliminary) investigation subsequent phases of work may be required.

ESP.6626e.2285 24 June 2017 East Street, Dowlais Earth Science Partnership 6.0 REFERENCES

BLACKMORE K, BRIERE DE L’ISLE B, GARROW D, JONSSON J, NORRIS M, TURRELL J, TREW J and WILCOX S. 2010. Guidance for the Selection of Water Supply Pipes to be Used in Brownfield Sites. UK Water Industry Research Ltd. Report ref. No 10/WM/03/21.

BRITISH GEOLOGICAL SURVEY (BGS). 2017. Website accessed January 2017.

BRITISH STANDARDS INSTITUTION (BSI). 2010. Code of Practice for Site Investigations. BS5930:1999+A2:2010. HMSO, London.

BRITISH STANDARDS INSTITUTION (BSI). 2013. Investigation of Potentially Contaminated Sites – Code of Practice. BS10175, HMSO, London.

COAL AUTHORITY. Website accessed May 2017.

CONSTRUCTION INDUSTRY RESEARCH & INFORMATION ASSOCIATION (CIRIA). 2001. Contaminated Land Risk Assessment – A Guide to Good Practice. CIRIA 552.

CONWAY B W, FORSTER A, NORTHMORE K J, and BARCLAY W J. 1980. South Wales Coalfield Landslip Survey. Institute of Geological Sciences, London.

DEPARTMENT FOR ENVIRONMENT, FOOD AND RURAL AFFAIRS (DEFRA) AND THE ENVIRONMENT AGENCY. 2004. The Model Procedures for the Management of Land Contamination. R&D Publication CLR11.

SCIVYER C. 2007. Radon: Guidance on Protective Measures for New Buildings. BRE 211.

WILSON S, CARD G and HAINES S. 2009. Ground Gas Handbook. Whittles Publishing.

ESP.6626e.2285 25 June 2017 East Street, Dowlais