DIRFT III - Planning Inspectorate · 2016-04-20 · DIRFT III : Environmental Statement (2012) 2526579v5 Chapter I - Ground Conditions & Contamination P1 I1.0 Introduction Introduction

DIRFT III Environmental Statement (2012) Chapter I Ground Conditions & Contamination October 2012

AECOM 14 Queen Victoria Road, Coventry, CV1 3PJ Tel: 024 7625 3300 Web: www.aecom.com

DIRFT III : Environmental Statement (2012)

2526579v5 Chapter I - Ground Conditions & Contamination

Contents

I1.0 Introduction 1 Introduction .............................................................................................1 Scope of Assessment .............................................................................1

I2.0 Policy Context 2

I3.0 Assessment Methodology & Significance Criteria 4 Assessment Methodology .......................................................................4 Significance Criteria ................................................................................6 Consultation ............................................................................................7

I4.0 Baseline Conditions 9 Introduction .............................................................................................9 Site Development History........................................................................9 Geology...................................................................................................9 Hydrogeology........................................................................................10 Hydrology..............................................................................................11 Mineral Deposits ...................................................................................11 Contaminated Land...............................................................................11 Ground conditions encountered ............................................................12

I5.0 Potential Impacts 16 Introduction ...........................................................................................16 Impacts During Construction.................................................................16 Impacts During Operation .....................................................................18

I6.0 Mitigation Measures 19 Introduction ...........................................................................................19 Impacts During Construction.................................................................19 Impacts During Operation .....................................................................19

I7.0 Residual Effects 21 Residual Impacts During Construction ..................................................21 Residual Impacts During Operation ......................................................21

I8.0 Conclusions 22

I9.0 Abbreviations 24

I10.0 References 25

I1.0


2526579v5 Chapter I - Ground Conditions & Contamination P1

I1.0 Introduction

Introduction

I1.1 The following chapter presents a description of and an assessment of the impacts of the proposed development on the geology and hydrogeology, including potential mineral deposits, beneath and surrounding the site at Rugby Radio Station, Rugby. Constraints posed by the ground conditions on the proposed development also are considered.

Scope of Assessment

I1.2 This section of the report considers the existing ground conditions present, and the impact that the proposed development will have on the study area. Impacts relating to geology, hydrogeology, contaminated land and mineral extraction specifically are considered.

I1.3 The assessment is based largely on the following reports:

1 Rugby Radio Station, Geo-environmental and Ground Conditions Assessment, reference 60045712/G-01, dated October 2008, Faber Maunsell Limited.

2 Rugby Radio Station, Ground Engineering and Geo-environmental Assessment – Phase 2 Interpretive Report, reference 60051619/G-04, dated May 2010, AECOM Limited.

3 Nicholls Colton Factual Report - Rugby Radio Station Phase 2, reference G09069, dated March 2010.


P2 Chapter I - Ground Conditions & Contamination 2526579v5

I2.0 Policy Context

Policies

I2.1 The main policy document particularly relevant to this chapter of the Environmental Statement is the recently published National Planning Policy Framework (NPPF), published in March 2012. The NPPF replaced the following documents which were of direct relevance to these elements of the Environmental Statement:-

1 Planning Policy Statement 23: Planning and Pollution Control, 2004

2 Minerals Policy Statement 1: Planning and Minerals, 2006

I2.2 Planning Policy Statement 23 (PPS 23) addressed the prevention of water pollution and provided guidance on the location of and the appropriateness of certain ‘polluting’ developments so as to prevent pollution and ensure that the environment and human health were protected.

I2.3 Section 120 of the NPPF states that:-

To prevent unacceptable risks from pollution and land instability, planning policies and decisions should ensure that new development is appropriate for its location. The effects (including cumulative effects) of pollution on health, the natural environment or general amenity, and the potential sensitivity of the area or proposed development to adverse effects from pollution, should be taken into account. Where a site is affected by contamination or land stability issues, responsibility for securing a safe development rests with the developer and/or landowner.

I2.4 In addition, Section 121 requires that the ground conditions at development sites are suitable for the proposed use after the completion of any necessary remediation measures:-

Planning policies and decisions should also ensure that:

- the site is suitable for its new use taking account of ground conditions and land instability, including from natural hazards or former activities such as mining, pollution arising from previous uses and any proposals for mitigation including land remediation or impacts on the natural environment arising from that remediation;

- after remediation, as a minimum, land should not be capable of being determined as contaminated land under Part IIA of the Environmental Protection Act 1990; and

- adequate site investigation information, prepared by a competent person, is presented.

I2.5 It is essential that there is an adequate and steady supply of material, but that this provision is made in accordance with the principles of sustainable development. Minerals development is different from other



forms of development because minerals can only be worked where they naturally occur. The NPPF requires that local planning authorities should identify Mineral Safeguarding Areas and adopt appropriate policies to ensure that known areas of mineral resources are not needlessly sterilised by non-mineral developments. Section 13 of the document considers potential conflicts of development located on sites of potential exploitable minerals to ensure a steady and adequate supply of aggregates and industrial minerals.

Legislation

I2.6 The relevant legislation with regard to geology, hydrogeology and contaminated land are summarised below.

1 Environmental Protection Act, 1990 - Defines within England, Scotland and Wales the legal framework for duty of care for waste, contaminated land and statutory nuisance.

2 The Environment Act, 1995 - Establishes the Environment Agency and SEPA as the regulatory bodies for contaminated land, control of pollution, conservation or enhancement of the environment and fisheries.

3 Contaminated Land (England) Regulations, 2006 SI 1380 - Sets out provisions relating to the identification and remediation of contaminated land. Identifies sites requiring regulation as 'special sites' and adds land contaminated by radioactive substances to this classification.

4 Groundwater (England and Wales) Regulations, 2009 - Empowers the Environment Agency in England and Wales to prevent direct or indirect discharge of certain dangerous substances to groundwater and control pollution resulting from the discharge of those and other substances.

5 Environmental Damage (Prevention and Remediation) Regulations, 2009 SI 153 – Regulations to ensure that the environment is fully protected against the most serious environmental damage, to surface or ground water, contamination of land where there is a significant risk to human health or serious damage to EU protected natural habitats and species or damage to Sites of Special Scientific Interest (SSSIs).

6 Groundwater Directive (2006/118/EC) – Establishes a regime which sets water quality standards for groundwater and introduces measures to prevent or limit inputs of pollutants into groundwater.



I3.0 Assessment Methodology & Significance

Criteria

Assessment Methodology

I3.1 Available reports and published information have been reviewed with the aim of identifying the geological and hydrogeological conditions within and surrounding the proposed Daventry International Rail Freight Terminal, Phase 3 (DIRFT III). This data review established the geological strata beneath the site, including any potential mineral deposits, made an assessment of the engineering properties of the soils and rocks and identified areas of potentially contaminated land and of potential land instability. It also identified potential pollutant linkages, and facilitated a preliminary risk assessment for each of the identified pollutant linkages.

I3.2 The aforementioned Geo-environmental Assessment and Ground Engineering reports were carried out in accordance with the guidance provided in the following documents:

1 Contaminated Land Risk Assessment: A guide to good practice, CIRIA C552, 2001

2 Code of Practice for Site Investigations, BS 5930:1999

3 Investigations of Potentially Contaminated Sites – Code of Practice, BS 10175:2001

4 Model Procedures for the Management of Land Contamination, CLR 11, 2004.

Sources of Information

I3.3 Historical Ordnance Survey maps (1:10,560 and 1:10,000) for the period 1884 to 2005, together with a web-based document published by the former station manager Michael Hancock, entitled “The Official History of Rugby Radio Station” dated 2002, have been obtained and reviewed to establish the historical development of the site, which is summarised below. It should be noted that any development occurring between map editions will not necessarily have been recorded and some mapping of the site for certain periods was unavailable.

I3.4 The geology, hydrogeology and hydrology of the site and the surrounding land has been interpreted from the following sources of information:

1 British Geological Survey (BGS) 1:50,000, Sheet 184, Warwick;

2 BGS 1:50,000, Sheet 185, Northampton;

3 BGS and Ordnance Survey (OS), 1:10,560 Sheets SP 57 NE; SP 57 SE; SP 57 NW and SP 57 SW;



4 BGS Sheet Memoir 184, Geology of the Country around Warwick

5 BGS British Regional Geology, Central England;

6 The logs of six exploratory hole logs obtained from the BGS borehole archives;

7 Environment Agency, Policy and Practice for the Protection of Groundwater, Groundwater Vulnerability 1:100,000 Map Series, Sheet 30, Northern Cotswolds.

8 The results of ground investigations carried out on the site between 4 and 11 June and 2 and 3 November 2009.

Approach to Methodology

I3.5 A ground investigation of the DIRFT III development area was carried out in two parts between 4 and 11 June 2009, and 2 and 3 November 2009. The investigation was designed to confirm the ground conditions and the anticipated geological sequence and to provide information on the engineering properties of the soils across the site.

I3.6 The purpose of the ground investigation was:

1 To determine the geological strata underlying the site;

2 To identify the presence of any made ground;

3 To ascertain the physical and chemical properties of the different geological strata;

4 To determine the presence and level of groundwater;

5 To determine the presence, nature and extent of ground and/or groundwater contamination on the site;

6 To assess the risk posed to potential receptors from any contamination on the site;

7 To identify the potential environmental liabilities associated with any contamination on the site;

8 To identify any constraints posed to the detailed development proposals; and,

9 To recommend appropriate foundation solutions for the proposed development.

I3.7 The first phase of the investigation consisted of seven boreholes drilled using a percussive, cable-tool drilling technique and the excavation of seven trial pits on land owned by Rugby Radio Station Limited Partnership. The second phase of the investigation consisted of a further two boreholes and three trial pits in the south of the site.

I3.8 The boreholes were drilled to a depth of 10m and the trial pits were excavated to a depth of 3m. Samples of the materials proved in the boreholes and trial pits were submitted for both geotechnical and



geochemical analysis. The suites of chemical and geotechnical testing analysis are presented in Figures I3.1 and I3.2 below:

Figure I 3.1 Chemical Analytical Suite: Soil Sampling – 2009 Investigation

Arsenic, Boron, Cadmium, Chromium, Copper, Lead, Mercury, Nickel, Selenium, Zinc, Phenols, Polycyclic Aromatic Hydrocarbons (PAH), Total Petroleum Hydrocarbons (TPH), Polychlorinated Biphenyls (PCBs), Pesticides and Herbicides, Volatile Organic Compounds and pH

Figure I 3.2 Geotechnical Analytical Suite: Soil Sampling – 2009 Investigation

Moisture Content, Atterberg limits, Particle Size Distribution, Optimum Moisture Content, Quick Undrained Triaxial, One Dimensional Consolidation, California Bearing Ratio, Organic Matter, BRE SD1 Soluble Sulfate and pH

I3.9 The logs of the boreholes and trial pits and the laboratory testing results are provided in Nicholls Colton Factual Report (reference G09069). Following the completion of drilling, groundwater level and ground gas monitoring was conducted as part of a programme of environmental monitoring.

Significance Criteria

I3.10 The following series of ‘significance criteria’ have been developed to help ascertain the level of impact significance (i.e. major, moderate, minor, no perceived impact, indeterminate) and to provide a transparent and auditable decision making process to the reader. It is important to note that the significance criteria have not been designed to be a prescriptive tool and have been used primarily for guidance purposes only. They are loosely based on guidance provided in Contaminated Land Good Practice Guide, C552, Section 6.

Table I 3.1 Significance Criteria

Type of Impact Rationale for Assessment of Significance

Major Adverse

Chronic (and/or acute) risk to human health likely to result in ‘significant harm’. Significant pollution of controlled water. Catastrophic damage to buildings/property. Short term significant risk to ecosystem. Significant harm caused to RIGS Statutory designated sites.

Moderate Adverse

Pollution of controlled water. Significant change in an ecosystem. Damage to crops, buildings, structures and services. Sterilisation of significant mineral resource.



Type of Impact Rationale for Assessment of Significance

Minor Adverse

Non permanent effects on human health (easily prevented by PPE). Minor pollution of non-sensitive controlled water. Harm to crops, buildings, structures and services, although not necessarily significant, which may result in financial loss or expenditure to resolve. Minor harm caused to RIGS Statutory designated sites. Sterilisation of low quality mineral resource.

Negligible/Neutral No change to soil or water quality, or harm caused to any identified receptors

Minor Beneficial An improvement to the on-site soil and/or water quality

Major Beneficial An improvement to both the on-site and off-site soil and/or water quality

Indeterminate Impact

Insufficient baseline information or subjectivity

Consultation

I3.11 The section below outlines the consultation comments received from relevant organisations.

I3.12 A copy of the Faber Maunsell Geo-environmental and Ground Conditions Assessment (reference 60045712/G-01) was sent to the following stakeholders for comment and review:

1 Environment Agency – Groundwater Protection Unit based at Fradley Park, Lichfield

2 Environmental Health Officers – Daventry District Council (DDC)

Environment Agency

I3.13 A telephone conversation was held between representatives from the Groundwater Protection Team at the Environment Agency and AECOM prior to the commencement of the ground investigation at the site. The exploratory hole location plan and schedule (including justification for each exploratory hole) was discussed.

I3.14 The EA noted that the proposed works, the exploratory holes and the chemical testing suites, seem appropriate for a preliminary investigation at this early stage in the development process. It was accepted that it is will be necessary to carry out additional investigations in a phased approach as development plans progress.

Daventry District Council

I3.15 A meeting was held with Environmental Health Officers from Rugby Borough Council (RBC); David Burrows (Regulatory Services Manager) and Daventry District Council (DDC); Eamon McDowell (Senior Planning Officer), Richard Willis (Environment Improvement Officer) and Lynda



Johnson (Senior Environmental Health Officer) on the 16th February 2008. The purpose of the meeting was to discuss the proposed strategy for the investigation of potentially contaminated land at the Rugby Radio Station Site.

I3.16 It was explained that the intrusive investigation was designed to target potential sources of contamination and also to provide a general spread of information across the site. It would be carried out prior to and in support of the planning application for the development. This approach was considered appropriate.

I3.17 The proposed exploratory hole location plan was issued to Lynda Johnson prior to commencement of the investigation for comment and consultation. The screening values that were derived by AECOM for the purpose of assessing the risks from contaminated land also were issued for comment.



I4.0 Baseline Conditions

Introduction

I4.1 The following section presents the baseline geological, hydrogeological and hydrological conditions together with information on potential areas of contaminated ground and mineral deposits beneath and immediately surrounding the DIRFT III Site.

Site Development History

I4.2 The development site covers an area of approximately 345ha, located between the M1 Motorway and the A5, comprising pasture land and radio masts constructed intermittently across the site. The site also contains one distinct building complex referred to as ‘Station B’, located midway along the western boundary of the site and currently accessed from the A5.

I4.3 Prior to the construction of ‘Station B and associated masts’ in 1953, the site comprised undeveloped agricultural land.

I4.4 During the operational period of the radio station, ploughing and the grazing of cattle was prohibited. Consequently, the land around the masts remained undeveloped with only the grazing of sheep permitted.

I4.5 Although several masts associated with ‘Station B’ currently remain, these have been disconnected and the majority of the site has been made available for the grazing of cattle. A small area of land in the south of the site, beyond Shenley Farm, has been ploughed and currently is being used to grow wheat.

Geology

I4.6 The geological maps and memoirs, together with the BGS borehole logs indicate that the geology beneath the site consists of superficial drift deposits overlying the Charmouth Mudstone Formation; comprising the former Lower and Middle Lias Clays of the Jurassic.

I4.7 The drift deposits generally consist of the following units:

1 Alluvium – interbedded silt, clay, loam and sand and gravels between 1m and 4m thick.

2 River Terrace Deposits - Both First and Second River Terrace Deposits are indicated as being present on the site. The First Terrace deposits generally comprise clayey sands and gravels with pebbles and are likely to be between 1m and 5m thick. The Second Terrace deposits generally comprise interbedded clay, sand and gravel with lenses of silt and peat and are likely to be between 3m and 10m thick.



I4.8 The underlying clay of the Charmouth Mudstone Formation can be in excess of 200m thick and comprises grey shelly often calcareous mudstones with ironstone and cementstone nodules and a basal bed of limestone.

Hydrogeology

Groundwater Resources

I4.9 The Groundwater Vulnerability Map indicates that the Charmouth Mudstone Formation is classified as Unproductive Strata, defined by the Environment Agency (EA) as: ‘rock layers or drift deposits with low permeability that have negligible significance for water supply or river base flow.’

I4.10 The map also indicates that the superficial drift deposits are all classified by the Environment Agency (EA) as ‘Secondary A’ aquifers, defined as: ‘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.’

I4.11 The permeability of the ‘Secondary A’ aquifers varies across the site from soils with Low Leaching Potential to High Leaching Potential.

I4.12 The map indicates that the River Terrace Deposits have low a leaching potential and are defined as: ‘soils in which pollutants are unlikely to penetrate the soil layer due to horizontal water movements, or they have the ability to attenuate diffuse pollutants’. However, it is considered that the lithology of these units is more likely to provide a high leaching potential, defined as ‘soils which readily transmit liquid discharges because they are either shallow, or susceptible to rapid flow directly to rock, gravel or groundwater’. Likewise the alluvium is more likely to provide a low leaching potential.

Source Protection Zones

I4.13 The site is not within a Source Protection Zone (SPZ) and there are no SPZs located within 1km of the site.

Groundwater Abstractions

I4.14 There are no licensed groundwater abstractions on the site. However there are two recorded groundwater abstractions within 500m of the site for general farming and domestic use. These comprise two wells at Stone House Farm, located 390m and 420m north of the site.



Hydrology

I4.15 The site is mainly agricultural land and there are several drainage ditches located across the site, mainly on the boundaries between fields. However, there are several key hydrological features:

I4.16 The Clifton Brook Tributary flows westwards across the northern half of the site from the M1 to the A5. A smaller ditchcourse runs along the entire western site boundary, adjacent to the A5. The northern section of the ditch flows north, discharging into the Clifton Brook Tributary. The southern section flows south, discharging into the Clifton Brook which flows north-west.

Mineral Deposits

Minerals Local Plan and Safeguarding Areas

I4.17 In March 2011, the Northamptonshire Minerals and Waste Development Framework (MWDF) replaced the ‘Northamptonshire Minerals Local Plan’ adopted by Northamptonshire County Council (NCC) in May 2006.

I4.18 As a key part of this framework, NCC has published the ‘Locations for Minerals Development, Proposals Map’, which was adopted in March 2011. The map identifies the locations of allocated mineral extraction sites within the County. Based on this map, the site is not shown as a ‘proposed location for mineral development’ and no mineral safeguarding areas are defined within the site boundaries.

Contaminated Land

Potential Areas of Contamination

I4.19 A Geo-environmental and Ground Conditions Assessment of the site was prepared by AECOM (formerly Faber Maunsell) in October 2008 (reference 60045712/G-01). The desk study and walkover survey identified a number of current and historical land uses which have the potential to give rise to soil and/or groundwater contamination.

I4.20 As the majority of the site has an agricultural history, potential sources of contamination closely are associated with the activities of the ‘Station B’ building complex in the centre of the site. These include oil/fuel storage, chemical/gas storage and the storage of waste materials. In particular; a decommissioned, underground fuel tank, buried beneath the car park to the rear of the building, and numerous electrical sub-stations and relay transmitters present around the building which, depending on age and construction, may contain lubricating oils contaminated with PCBs.



Ground conditions encountered

I4.21 Generally, the ground investigation confirmed the anticipated geological sequence. The site is underlain by a variable thickness of superficial deposits which rest on the Charmouth Mudstone Formation (formerly the Lias Clay).

I4.22 Made ground was encountered in only two exploratory locations, in the car park area within the ‘Station B’ building complex. This material was between 0.25m and 0.45m thick, comprising concrete, bituminous tarmacadam and topsoil with occasional fragments of brick, ceramics and tiles.

I4.23 Superficial drift deposits consisting of a mixture of soft to firm, orange-brown and grey, sandy, gravelly clays and firm brown and grey clays with occasional orange-brown medium sands and fine to coarse gravels were encountered in all exploratory boreholes and trial pits. Generally, the gravels comprise quartz or flint and are typically sub-angular to sub-rounded. The soils are largely interpreted as alluvial deposits and vary in thickness between approximately 1.2m and 3.5m. The superficial deposits are much thinner than anticipated from a review of published geological maps.

I4.24 The Charmouth Mudstone Formation which underlies the superficial deposits generally comprises firm to stiff, locally very stiff, dark grey clay with occasional mudstone lithorelics. The top of the clay is marked by a 1m to 2m thick weathered zone consisting of softer, brown-grey clay with occasional selenite crystals. The base of the clay was not proven in any of the exploratory hole locations. The Charmouth Mudstone Formation was proved to a maximum thickness of 7.6m.

Mineral Resources

I4.25 Based on the conditions proved during the ground investigation, it is considered that no significant or extensive, economically viable, mineral deposits are present beneath the site.

Soil Chemical Results

I4.26 The results of geochemical testing of soil samples were compared to AECOM Generic Assessment Criteria (AGAC) as an initial screen. Details of the screening criteria are included in Appendix I1.

I4.27 The concentrations of potential Chemicals of Concern (COC) were below the AGAC screening values in the majority of analysed samples.

I4.28 Widespread elevated arsenic levels have been identified in the soils beneath the site. The arsenic is naturally-occurring and associated with the geological conditions (Charmouth Mudstone Formation clays) in the Rugby area.



I4.29 Phenol concentrations were below the laboratory detection limit in all samples. TPH and PAH concentrations were significantly below the guidance values.

I4.30 It is considered, based on the proposed end use, that the risk to human health from soil contamination is considered to be low and that no remedial measures are required to render the site suitable for the proposed development.

Groundwater Level

I4.31 No groundwater was encountered during drilling, except for borehole CP07 located in the south eastern part of the site, which struck groundwater at approximately 5.0m below ground level in the Charmouth Mudstone Formation. Within 20 minutes, the groundwater had risen to a level 1.26m above ground level. Groundwater seepages were noted in trial pits TP03 and TP07.

I4.32 It is considered that groundwater in the Charmouth Mudstone Formation locally is held under pressure within thin, discontinuous, siltstone bands surrounded by low permeability clays.

I4.33 Subsequent groundwater monitoring visits were conducted as part of an environmental monitoring programme following the completion of drilling. Generally, groundwater in the superficial deposits flows in a north westerly direction. It is considered likely that the groundwater in the superficial deposits is in hydraulic continuity with, and provides baseflow discharge to the surface water system on and in the vicinity of the site.

Groundwater Quality

I4.34 Samples of groundwater were recovered from 15 exploratory holes across the entire Radio Station site. It is considered that this groundwater is present in layers of permeable materials within the largely clay-dominated superficial deposits.

I4.35 The majority of potential contaminants, including TPH, phenols and volatile organic compounds (VOCs), are present in the groundwater at concentrations below the laboratory detection limits in all samples.

I4.36 Concentrations of arsenic above the screening value of 32mg/l were recorded in several monitoring points at various locations across the site. It is considered that naturally occurring arsenic levels, within the ground beneath the site, are the primary source of this contamination.

I4.37 Elevated cadmium, mercury and selenium concentrations were recorded in apparently unconnected locations across the site. The contamination at these locations cannot be readily explained.



I4.38 The site is not located within a Source Protection Zone, there are no potable abstractions in the immediate vicinity, and much of the site is underlain by unproductive strata, it is considered that the screening values used, whilst conservative, are appropriate for the minor groundwater resources within the superficial drift deposits which underlie the site.

I4.39 Based on a review of the results of the groundwater quality samples, it is considered that the groundwater beneath the site has not been significantly affected by activities undertaken on site. Consequently, it is also considered that the risk from any contamination present on the site to the quality of the Clifton Brook Tributary, in the northern half of the site, and any associated surface water drains is low.

Ground Gases

I4.40 Reference to the Annex A maps in the Building Research Establishment (BRE) publication 211, entitled “Radon: Guidance on Protective Measures for New Dwellings” dated 1999, indicates that the site is not in a radon affected area. Therefore Radon protective measures are considered unnecessary for future developments on this site.

I4.41 A total of six boreholes were monitored for the presence of ground gases (methane, carbon dioxide, oxygen, hydrogen sulphide and carbon monoxide) together with gas flow rates on 1 July and 2 September 2009.

I4.42 Methane was not recorded above the limit of detection of 0.1%v/v in any borehole. Carbon dioxide was detected above the limit of detection in five of the six monitored boreholes up to a maximum concentration of 1.3%v/v in borehole CP03 in both July and September. No detectable gas flow was recorded in any of the monitored boreholes during either visit.

I4.43 Methane and carbon dioxide occur naturally in the atmosphere; in addition, the decay of buried organic material has the potential to generate both methane and carbon dioxide. Methane is a colourless and odourless gas. It is a flammable gas and in the presence of at least 12.1%v/v oxygen can form an explosive atmosphere at concentrations above 5.0%v/v.

I4.44 The risks associated with methane and carbon dioxide are assessed using BS 8485:2007, which cites the guidelines published by CIRIA (Wilson et al 2007) and the NHBC (Boyle and Witherington 2007). These guidelines were written so as to be mutually consistent and are based on an interpretation of measured gas concentrations and gas flow rates, amongst other variables. They are compliant with the Environment Agency ‘Model Procedures for the Management of Land Contamination’, CLR11.



I4.45 In the above guidance, the development proposals for the site require consideration of ‘Situation A’, defined as any development other than low-rise (1 or 2 storey) housing with vented sub-floor void and gardens, e.g. factories, depots etc. This uses a modified version of the Wilson and Card (1999) methodology.

I4.46 The modified Wilson and Card assessment compares the maximum recorded gas concentrations and flow rates to determine gas screening values (GSV) which are compared with the limits in the published table (CIRIA Table 8.5). One of the assumptions in using the published table is that the worst-case ground gas regime has been identified on the site, for either methane (CH4) or carbon dioxide (CO2) at the worst-case temporal conditions that the site may be expected to encounter, such as immediately following rapid changes in atmospheric pressure.

I4.47 The idealised frequency of monitoring is suggested in CIRIA Tables 5.5a and 5.5b. These tables are adapted from Wilson and Haines (2005) Table 3, which gives examples of ground conditions with the various gas generation potentials, ranging from inert made ground/natural ground conditions (very low potential) to post 1960s domestic landfill (very high potential). It is considered, as the majority of the site is currently undeveloped agricultural land and due to the absence of any extensive made ground, that the current gas generation potential at the site is very low and that the sensitivity of the development is low.

I4.48 Consequently, an appropriate minimum monitoring regime of four readings over one month, normally would be recommended provided other monitoring requirements are also met, such as prevailing atmospheric pressure conditions (for example, BS 8485:2007 recommends monitoring shall include a period of falling atmospheric pressure).

I4.49 Two gas monitoring rounds have been completed to date. However, as no detectable gas flows have been recorded, calculated gas screening values for both methane and carbon dioxide are zero l/hour. Accordingly, with respect to methane and carbon dioxide, the site is classified as ‘Characteristic Situation 1’ using the Wilson and Card methodology. Sites characterised as ‘Characteristic Situation 1’ are defined as those where a negligible gas regime has been identified, of very low risk with natural soils containing low organic content and where gas protection measures are considered unnecessary.

I4.50 Firm conclusions on the risks associated with ground gases on the site are not possible at this stage due to the very limited monitoring carried out. The draft conclusions will be re-assessed following the results of future monitoring visits.



I5.0 Potential Impacts

Introduction

I5.1 For the purpose of the EIA, a suite of outline activities has been identified in order that a robust environmental appraisal can be undertaken. These are presented in the following table:

Table I 5.1 Summary: Potential Impacts

Activity Detail

Construction

1

Site access and site clearance: Activities are likely to included demolition of existing buildings and aerial structures, clearance of hardstanding areas, the redistribution of volumes of soils as part of cut and fill operations across the site to achieve proposed finished floor levels and the removal of selected trees, hedges and areas of scrub and vegetation

2

Ditch clearance and reservoir removal: it has been assumed that many of the ditches and watercourses across the site will be dredged and surface water drainage improved, and the reservoir in the centre of the site will be fully drained, dredged and reinstated.

3 Construction: this will involve the actual construction of the development and will include items presented in the Masterplan

Operation

4 Operational phase: post construction, once employees and visitors are working within the new rail terminal

Impacts During Construction

I5.2 A review of the baseline information has identified project activities in both the construction and operational phases of the development which have the potential to cause harm to identified receptors as follows:

1 Dredging of the ditch courses may disturb potential contamination within sediments

2 Earthworks and site regrading have the potential to move contaminated soils around the site

3 Receptors could come into contact with contaminated soils and/or water

Impact 1 – Impact on surface water quality and reservoir sediments

I5.3 Dredging of the ditches is likely to disturb any potential contaminants and cause a degradation of the water quality. This may result in a minor adverse impact for the short-term. However, dredging also may remove any potential source of contamination and this would have a minor beneficial impact.



I5.4 On-site excavations during preparatory earthworks will expose soils susceptible to erosion producing surface water runoff with a high content of suspended soils, which in turn may cause degradation in the quality of on-site and off-site surface waters. This may result in a moderate adverse impact for the short-term.

Impact 2 – Impact on waste generation

I5.5 The current development proposals indicate that the area will be utilised by DIRFT III (Daventry International Rail Freight Terminal, Zone 3) to include large industrial units, rail lines, roads and associated infrastructure.

I5.6 The proposals have the potential to generate large volumes of soils from cut and fill operations in order to accommodate development plateaus and achieve retaining structures and engineered slopes.

I5.7 The majority of soils that are excavated during the construction of footings, installation of services and the construction of pavements are likely to be classified as inert and due to the large size of the site, can be redistributed to different areas of the site. Accordingly, there would be no perceived impacts.

Impact 3a – Impact on human health: construction workers

I5.8 The ground investigation has identified discrete areas of contamination in shallow soils across the site and without pre-treatment or the use of appropriate personal protective equipment; this could result in a minor adverse impact on the health of construction workers.

Impact 4 – Impact on the groundwater regime

I5.9 A perched water table is present at shallow depths in the superficial deposits. The construction of foundations or the installation of services locally may affect the hydrogeological flow system within the site and this may result in a minor adverse impact.

Impact 5 – Impact on the groundwater quality

I5.10 Excavations during preparatory earthworks may encounter and expose shallow and perched groundwater resources to contamination from machinery and surface water runoff, which in the absence of mitigation measures could result in a moderate adverse impact.

Impact 6 – Impact on the ground gas regime

I5.11 A negligible gas regime has been identified beneath the site. Accordingly, it is considered there will be no impact to the development during construction.



Impacts During Operation

Impact 3b – Impact on human health: future end-users

I5.12 Site end users could come into contact with contaminated soils that remain untreated in the ground. Without avoidance or mitigation measures in place, this could result in a minor adverse impact on human health.

I5.13 As the area is likely to be covered with extensive areas of hardstanding under the current development proposals, it is considered that future site users will not be at risk from coming into direct contact with contaminated materials.

Impact 6 – Impact on the ground gas regime

I5.14 As stated above, negligible gas regime has been identified beneath the site. Accordingly, it is considered there will be no impact to the development post construction.



I6.0 Mitigation Measures

Introduction

I6.1 Mitigation measures should be implemented during and after construction to reduce and/or eliminate potential adverse impacts.

Impacts During Construction

Impact 2 – Impact Management - Waste generation

I6.2 The topography of the site should be considered when establishing the finished floor levels of the proposed buildings and infrastructure in order to minimise cut and fill across the site.

I6.3 Assuming that the cut and fill volumes balance, there would be no perceived impact.

Impact 3a – Impact Management - Human Health: Construction Workers

I6.4 The ground engineering and geo-environmental assessment should be reviewed to establish the risks posed to construction workers. More detailed ground investigations are required prior to phased construction to clarify the risks.

I6.5 Assuming that construction workers follow the recommendations of the geo-environmental risk assessment, wear appropriate personal protective equipment and follow good hygiene practice, there should be no perceived impact to health.

Impact 4– Impact Management – Groundwater Regime

I6.6 The groundwater flow and the depth of the water table should be considered in the design of the foundations for the proposed development. However, the finished plateau levels of the development are unlikely to significantly affect the hydrogeological regime and there should be no perceived impact.

Impacts During Operation

Impact 3b – Impact Management - Human Health: Future End Users

I6.7 Additional, phased, ground investigation works should be carried out to clarify the nature and extent of any ground contamination at the site. This should identify the need for soil and/or groundwater remediation if required.

I6.8 Although minor adverse impacts are possible, as contamination is highly localised, it is considered that with appropriate remediation measures



there will be no perceived impacts on the health of the future end users of DIRFT III.



I7.0 Residual Effects

Residual Impacts During Construction

I7.1 There will be no residual impacts as a result of the proposed DIRFT III development in respect of the ground, groundwater and surface water conditions assuming that mitigation measures identified in Section I6.0 are implemented.

Residual Impacts During Operation

Impact 5b – Impact on human health: future end-users

I7.2 The removal and/or treatment of contaminated soils and groundwater currently present on the site will result in a minor beneficial residual effect, and could in the long term result in a major beneficial residual effect as a result of improving the shallow soil quality.



I8.0 Conclusions

I8.1 Based on an assessment of background information on the site and the findings of the ground investigations, the following conclusions can be drawn:

1 The development area is underlain by a viable thickness of superficial deposits of sand, gravel and clay, which overlie clays of the Charmouth Mudstone Formation.

2 Generally, the superficial deposits are very thin or absent. No superficial deposits are present in the south eastern corner.

3 There is no evidence of significant, economically viable, mineral deposits beneath the site.

4 Groundwater is present in the superficial deposits. It is considered that the groundwater is in hydraulic continuity with the local surface watercourses which form the catchment of the Clifton Brook. The groundwater level in the superficial deposits typically is at a depth between 0.5m and 1.0m.

5 The area largely has been under agriculture. Areas of potentially contaminated ground are associated with the activities of the O2 Airwave building complex in the centre of the site and Shenley Farm adjacent to the eastern boundary.

6 There is no evidence of significant or extensive ground contamination on the development site. Elevated hydrocarbons are present in the area of the O2 Airwave building complex. Apart from isolated ‘hotspots’ of contamination, it is concluded that the ground conditions do no place any major constraints on the proposed development.

7 Treatment and/or excavation of localised areas of ground contamination may be required.

8 There is no evidence of widespread or significant groundwater contamination. It is concluded that previous activities on the site do not pose a risk to groundwater or surface water quality.

9 Elevated ground gases concentrations have not been detected on the site. Based on the results of limited monitoring, it is concluded that gas protection measures will not be needed for the proposed development. However, additional monitoring is required to confirm this conclusion.

I8.2 The following recommendations are made:

1 A ground investigation has been completed to a level sufficient to facilitate completion of the Environmental Impact Assessment and was designed to facilitate an assessment of the ground conditions



across the whole development site. Certain areas of potential contamination were targeted in the investigation.

2 Due to the large size of the development site, it was considered impractical at this stage to carry out a detailed ground investigation to facilitate an assessment of the ground conditions in each of the development areas. It is recommended that a staged ground investigation should be carried out, following confirmation of the DCO, in advance of the construction of each development area to confirm the ground conditions and facilitate foundation design and any remediation measures which may be required.

3 A limited amount of ground gas monitoring has been carried out. This has not identified the presence of elevated gas levels. However, currently the amount of data is insufficient to comply with current guidance. It is recommended that further ground gas monitoring is undertaken to prepare a database which complies with current guidance. As a minimum at least two further monthly monitoring visits should be carried out.



I9.0 Abbreviations

1 BGS British Geological Society

2 BRE Building Research Establishment

3 CIRIA Construction Industry Research and Information Association

4 DDC Daventry District Council

5 DIRFT Daventry International Rail Freight Terminal

6 EA Environment Agency

7 EIA Environmental Impact Assessment

8 EU European Union

9 GSV Gas Screening Value

10 GQRA Generic Qualitative Risk Assessment

11 MSA Mineral Safeguarding Area

12 NCC Northamptonshire County Council

13 NHBC National House Building Council

14 OS Ordnance Survey

15 PAH Polycyclic Aromatic Hydrocarbons

16 PCB Polychlorinated biphenyls

17 RBC Rugby Borough Council

18 SEPA Scottish Environment Protection Agency

19 SPZ Source Protection Zone

20 SSSI Site of Special Scientific Interest

21 TPH Total Petroleum Hydrocarbon

22 VOC Volatile Organic Compound

23 WCC Warwickshire County Council



I10.0 References

1 Building Research Establishment (BRE) publication 211, entitled “Radon: Guidance on Protective Measures for New Dwellings” 1999,

2 Code of Practice for Site Investigations, BS 5930:1999

3 Code of Practice for the Characterisation and Remediation from Ground Gas in Affected Developments BS8485:2007

4 Investigations of Potentially Contaminated Sites – Code of Practice, BS 10175:2001

5 CIRIA C552, Contaminated Land Risk assessment. A Guide to Good Practice 2001

6 CIRIA C665, Assessing the Risks Posed by Hazardous Ground Gases to Buildings 2007

7 Contaminated Land (England) Regulations, 2006 SI 1380

8 Environmental Damage (Prevention and Remediation) Regulations, 2009 SI 153

9 The Environment Act, 1995

10 Environmental Protection Act, 1990

11 Groundwater Directive (2006/118/EC)

12 Groundwater (England and Wales) Regulations, 2009

13 Minerals Policy Statement 1: Planning and Minerals, 2006

14 Model Procedures for the Management of Land Contamination, CLR 11, 2004

15 NHBC Guidance: Evaluation of Development Proposals on Sites Where Methane and Carbon Dioxide are Present. March 2008.

16 Planning Policy Statement 23: Planning and Pollution Control, 2004

17 Wilson S.A. and Haines S. 2005. Site investigation and monitoring for ground gas assessment - back to basics. Land Contamination and Reclamation, 13 (3), 211-22.

Documents

DIRFT III - Planning Inspectorate · 2016-04-20 · DIRFT III : Environmental Statement (2012) 2526579v5 Chapter I - Ground Conditions & Contamination P1 I1.0 Introduction Introduction