Environmental Statement Volume 3 – Hydrogeological Risk Assessment

Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash

Rugeley Power Station

May 2007

Document control sheet Form IP180/B

Client: Rugeley Power Limited Project: Rugeley B Station Borrow Pit Landfill Job No: J24151C0 Title: Environmental Statement (Volume 3, Hydrogeological Risk Assessment)

Prepared by Reviewed by Approved by

ORIGINAL NAME NAME NAME S. Mannings & A. J. Oakeshott Parkes S. Mannings

DATE SIGNATURE SIGNATURE SIGNATURE April 2007

REVISION 1 NAME NAME NAME J. Oakeshott S. Mannings S. Mannings

DATE SIGNATURE SIGNATURE SIGNATURE

May 2007

REVISION NAME NAME NAME

DATE SIGNATURE SIGNATURE SIGNATURE

REVISION NAME NAME NAME

DATE SIGNATURE SIGNATURE SIGNATURE

This report, and information or advice which it contains, is provided by Jacobs Ltd solely for internal use and reliance by its Client in performance of Jacobs Ltd’s duties and liabilities under its contract with the Client. Any advice, opinions, or recommendations within this report should be read and relied upon only in the context of the report as a whole. The advice and opinions in this report are based upon the information made available to Jacobs Ltd at the date of this report and on current UK standards, codes, technology and construction practices as at the date of this report. Following final delivery of this report to the Client, Jacobs Ltd will have no further obligations or duty to advise the Client on any matters, including development affecting the information or advice provided in this report. This report has been prepared by Jacobs Ltd in their professional capacity as Consulting Engineers. The contents of the report do not, in any way, purport to include any manner of legal advice or opinion. This report is prepared in accordance with the terms and conditions of Jacobs Ltd‘s contract with the Client. Regard should be had to those terms and conditions when considering and/or placing any reliance on this report. Should the Client wish to release this report to a Third Party for that party's reliance, Jacobs Ltd may, at its discretion, agree to such release provided that: (a) Jacobs Ltd's written agreement is obtained prior to such release, and (b) By release of the report to the Third Party, that Third Party does not acquire any rights, contractual or otherwise, whatsoever against Jacobs Ltd, and Jacobs Ltd accordingly assume no duties, liabilities or obligations to that Third Party, and (c) Jacobs Ltd accepts no responsibility for any loss or damage incurred by the Client or for any conflict of Jacobs Ltd's interests arising out of the Client's release of this report to the Third Party.

Contents

1 Introduction 1-1

2 Installation Description 2-1

2.1 Site Location 2-1

2.2 Historical Development and Existing Arrangement 2-1

2.3 Proposed Containment Engineering 2-1

2.4 Use of Cooling Water as a Waste Transport Medium 2-1

2.5 Operation 2-2

2.6 Future Scenario 2-2

3 Overview of Conceptual Site Model 3-1

3.1 Introduction 3-1

3.2 Pollution Source Term 3-1

3.3 Pollution Pathway – Landfill Liner 3-2

3.4 Receptors 3-3

3.5 Numerical Modelling 3-4

3.6 Conclusion 3-5

4 Source Term Characterisation 4-1

4.1 Waste Types 4-1

4.2 Overview of Physio-Chemical Properties of PFA 4-1

4.3 Site-Specific PFA Analyses 4-5

4.4 Ash Supernatant Analyses 4-10

4.5 Model Source Term 4-12

5 Environmental Setting 5-1

5.1 Topography and Surrounding Land Uses 5-1

5.2 Historical Land Uses 5-1

5.3 Regional Geology 5-3

5.4 Ground Conditions in the Site Area 5-3

5.5 Hydrology 5-6

5.6 Hydrogeology 5-8

6 Assessment of Hydrochemical Conditions 6-1

6.1 Introduction 6-1

6.2 Monitoring 6-1

7 Hydrogeological Risk Assessment & Numerical Modelling 7-1

7.1 Introduction 7-1

7.2 Source-Pathway-Receptor Linkages 7-1

7.3 Source Characterisation 7-1

7.4 Groundwater and Surface Water Monitoring 7-2

7.5 Numerical Modelling 7-3

7.6 Modelling Scenarios and Assumptions 7-4

7.7 Model Results 7-6

7.8 Model Sensitivity 7-7

7.9 Model Summary 7-8

7.10 Hydrogeological Risk Assessment Summary 7-8

8 Requisite Surveillance 8-1

8.1 Introduction 8-1

8.2 Source Term and Leachate 8-1

8.3 Groundwater 8-2

8.4 Surface Water 8-3

8.5 Proposed Control & Trigger Levels 8-3

9 Conclusions 9-1

Appendix A - HRA Drawings Appendix B - Background Leachable Testing and Site Specific Certificates of Analysis Appendix C - Historical Plans Appendix D - Borehole Logs Appendix E - Pumping Tests Appendix F - Groundwater Level Data and Hydrographs Appendix G - Baseline Groundwater Quality Appendix H - Quantitative Risk Assessment Appendix I - Site Monitoring Plan

1 Introduction

Rugeley Power Limited (the applicant) has submitted a full Planning Application to Staffordshire County Council (the Waste Planning Authority or ‘WPA’) for the restoration through landfill of the B Station Borrow Pit (the Borrow Pit).

The Borrow Pit is located at the eastern end of the Rugeley Power Station site in Rugeley, Staffordshire, and would be infilled using Pulverised Fuel Ash (PFA) generated on-site as a by-product of coal combustion.

It is estimated that the voidspace of the Borrow Pit is around 718,000 m3 which would cater for the disposal of approximately 1 Million tonnes PFA (assuming a density of 1.4 tonnes/m3). The proposed landscaping would consume an additional 600,000 tonnes PFA (assuming a density of 1.6 tonnes/m3), increasing the landfill’s total capacity to around 1.6 Million tonnes PFA. The proposal should be able to cater for the disposal of all of Rugeley’s unsold PFA until at least 2016.

PFA is classified under the European Waste Catalogue (No. 10-01-02) as being “Solid, Non-Hazardous, Stable, Non-Biodegradable and Non-Reactive”.

The proposal falls under Item 11, Schedule 2 of the Town and Country Planning (Environmental Impact Assessment) (England and Wales) Regulations 1999 (the EIA Regulations) and as such the Planning Application must be accompanied by an Environmental Statement (ES) to assess its potential environmental effects.

The ES consists of three separate volumes, as follows:

• Volume 1 Non Technical Summary; • Volume 2 Environmental Statement (Main Report); and • Volume 3 Hydrogeological Risk Assessment.

The scope and content of the ES were agreed during pre-application meetings held with the WPA, which provided a ‘Scoping Opinion’ dated 5/12/2006 for the development under Regulation 10 of the EIA Regulations. This document is Volume 3, the Hydrogeological Risk Assessment, which provides an assessment of the likely risks posed by the landfill on groundwater and surface water quality.

The Borrow Pit was excavated within fluvio-glacial sands and gravels and is approximately 11m deep. The Borrow Pit is currently flooded but would be dewatered and provided with an engineered basal and side slope liner composed of bentonite enriched soil (BES) of minimum 0.5m thickness. Due to the low level of environmental risk posed by the installation, it would be operated as a passive landfill. This report demonstrates that the installation would comply fully with the Groundwater Regulations 1998 and the Landfill Regulations 2002.

The report has been prepared in general accordance with all relevant guidance provided by the Environment Agency for the landfill sector, including:

• Hydrogeological Risk Assessments for Landfills and the Derivation of Groundwater Control and Trigger Levels, March 2003 • Guidance on landfill completion, February 2003

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• Guidance on Monitoring of Landfill Leachate, Groundwater and Surface Water Issue 1 dated 28 Feb 2003 • Landfill Directive Regulatory Guidance Note 6.0 Interpretation of the Engineering Requirements of Schedule 2 of the Landfill Regulations 2002 Version 2 dated July 2004 • LFD Regulatory Guidance Note 11: The disposal in landfills for non- hazardous waste of; stable, non-reactive wastes, asbestos wastes; waste with high sulphate or gypsum contents

The structure of this report is as follows:

Section 2 provides a description of the installation;

Section 3 summarises the conceptual site model;

Section 4 characterises the source term represented by the repository;

Section 5 describes the site environmental setting and the hydrogeological and hydrological conditions relating to the site and local surrounding area;

Section 6 assesses the hydrochemical conditions relating both to groundwater and surface water resources located on site and in the local vicinity;

Section 7 comprises the hydrogeological risk assessment, with the methodology and results of contaminant fate and transport modelling that has been carried out for the installation;

Section 8 outlines the proposals for requisite monitoring of the installation in order to comply with the Groundwater Regulations and relevant guidance;

Section 9 sets out the overall conclusions of the report.

All drawings referred to in the report can be found in Appendix A.

Rugeley Power Limited 1-2 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

2 Installation Description

2.1 Site Location

The proposal site is located to the south-east of Rugeley Power Station (NGR 406930 316670) and covers approximately 87.3 hectares in total, of which approximately 6.3 hectares is occupied by the existing Borrow Pit. The installation will comprise a single discrete excavated cell. Drawing J24151C0/EIA/01 shows the site location and Drawing J24151C0/EIA/02-A the installation boundaries.

2.2 Historical Development and Existing Arrangement

The Borrow Pit, a flooded gravel pit, was excavated and worked in 1960s to provide aggregate for the construction of B station. It is up to 11m deep, and borehole logs show that it is underlain by a significant thickness of River Terrace Deposits (RTD). The water level is therefore regarded as a surface expression of shallow groundwater associated with the RTD minor aquifer.

2.3 Proposed Containment Engineering

The Borrow Pit will have both a basal and side slope engineered liner installed under a CQA system. The liner will comprise a minimum 0.5m thickness of bentonite enriched soil (BES). The BES lining will be formed from a mixture of locally won sand and fine gravel with bentonite, a very low permeability clay mineral.

It should be noted that the applicant wishes to consider off-setting some of the sands and gravels used in the BES mix with PFA, subject to discussions with the Environment Agency during the application for PPC permit for the installation.

A rigorous CQA (Construction Quality Assurance) testing programme will be put in place to monitor the mix design and the as-placed lining material to ensure that the required thickness and permeability is achieved.

The lining layer needs to have sufficient weight so as to resist the uplift pressure of inflowing groundwater during re-watering. A layer of compacted PFA approximately 0.5m thick will therefore be placed over the BES liner as it is laid. A detailed assessment of this risk and of the precautions that need to be taken against liner blow-out will be undertaken when the specification for the landfill is prepared.

The Borrow Pit will require dewatering by combination of direct and sump pumping to enable installation of the basal liner (as determined following pumping tests undertaken during June 2005).

2.4 Use of Cooling Water as a Waste Transport Medium

It is proposed that the installation will involve the use of water in order to transport PFA and FBA fines from the source to disposal site. The transport water will be drawn from the power station cooling water system as currently.

The slurry transport water would, therefore, not constitute waste and hence not prohibited waste in the context of the Landfill Regulations. The installation would be full of water while it would be operational and this should be considered in the

Rugeley Power Limited 2-1 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

interpretation of Schedule 1, Paragraph 2 of the Landfill Regulations. This Schedule deals with water and leachate management, which indicates that the Environment Agency should “take account of the characteristics of the landfill”.

2.5 Operation

It is anticipated that the installation will take some 10 years to fill, including the final phase when the surface levels will be raised to create the proposed final restoration profile and development landform.

When full the installation would be allowed a short period of time to enable the surface to dry, after which it would be initially ‘carpeted’ with a 1-2m thick layer of conditioned PFA that would be transported to the site from B Station. Dry- conditioned ash contains around 15% water which minimises dust blow and lubricates the ash to facilitate handling and compaction.

The filled Borrow Pit will be capped with a 2 metre thick layer of conditioned PFA in order to provide a structural platform for potential future development of the landfill site. The finished landform design modifies this capping layer by the addition of up to a further 4 metres depth of conditioned PFA in order to provide surface drainage and to integrate with the bund to the eastern / north-eastern boundary.

Further details on the proposed design of the finished landform are provided in Section 10.6.2, Volume 2 of the ES.

2.6 Future Scenario

The proposed landfill would be used for the permanent disposal of PFA with no reclaim being envisaged, apart from the periodic harvesting of cenospheres during the period when the site is being filled with PFA slurry.

Ultimately it is intended that the restored landfill site will be redeveloped for other beneficial uses including housing as part of Rugeley Power Stations eventual site closure plan. A large proportion of the site would be covered with low permeability cover: buildings, roads and areas of hard-standing. The remainder of the site would be developed as gardens and local amenity areas i.e. there would be a vegetative cover including a high proportion of bushes and trees. The exact arrangement would be subject to planning consent at the time. A detailed scheme of works and planning proposal would be developed as part of the site closure.

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3 Overview of Conceptual Site Model

3.1 Introduction

This section presents an overview of the key elements of the conceptual understanding of the hydrogeological conditions pertaining to the licensed site and overall mounded deposit. Detailed considerations of the data supporting the key elements of this conceptual model are presented in the following sections.

3.2 Pollution Source Term

The ‘pollution source term’ would be Pulverised Fuel Ash (PFA) produced as a result of combustion primarily of coal to produce electricity at Rugeley Power Station. Rugeley Power Station will recycle as much of this PFA as possible, sending it off-site for use primarily as a construction material. However, supply will always exceed demand, and the surplus material will need to be disposed of.

PFA is classified under the European Waste Catalogue (No. 10-01-02) as being “Solid, Non-Hazardous, Stable, Non-Biodegradable and Non-Reactive”.

The PFA would be sourced from Rugeley’s existing dust plant located within the main Power Station Site which lies outside of the application boundaries of the Borrow Pit development. PFA would be handled in two ways – either being mixed with between 1:5 and 1:10 ratio ash: water to form a slurry which can then be pumped over to the landfill by pipeline, or ‘conditioned’ by the addition of around 15% water which can then be loaded into lorries and transported to the landfill site using on-site haul routes. In both cases the water would be taken from Rugeley’s existing cooling water purge and would not increase water usage.

Both means of handling will be used to fill the proposed landfill, approximately 2/3rd of the below water table voidspace being filled using slurried PFA, conditioned PFA then being used to fill in the remaining voidspace and to landscape the site. The physical and chemical properties of PFA can be summarised as follows:-

• PFA consists of spherical particles with a diameter in the range <10 - 200µm which is consistent with a fine silt. Under loading these particles pack closely together to form very stable deposits which accounts for the widespread use of PFA as an engineering fill material;

• This property also means that compacted PFA deposits typically display low hydraulic conductivity values, which serves to limit the interaction between the ash deposit and groundwater. Freshly consolidated conditioned PFA would typically have a hydraulic conductivity of around 1x10-7m/s or lower;

• PFA is a “pozzolana” meaning that it self-hardens. This is particularly true of conditioned PFA. A hard ‘skin’ initially forms at the exposed face, within hours/days of the ash being compacted. If left undisturbed, a hard-pan layer then develops within the upper profile of the deposit, which will progressively thicken until the whole deposit is lithified. The hydraulic conductivity of cemented PFA is much lower than uncemented PFA (up to 2-3 orders of magnitude lower) which will substantially reduce the seepage of water through the deposit, so limiting leachate production still further;

Rugeley Power Limited 3-1 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

• Regards the chemical properties of PFA, the major elements Aluminium, Calcium, Iron, Magnesium, Potassium, Silicon and Sodium are the main “building blocks”, which together account for between 90 – 99% of the mass. Of these elements, Aluminium and Silicon are the most abundant and together account for over 80% of the mass. These constituents exist primarily as “Alumino-Silicates” (the main constituents of sand), however, they are “glassified” when the coal is burned in the power station;

• Typically PFA contains between 1 – 5% Calcium Oxide (Lime), which makes it moderately alkaline, pH values of slurried PFA typically ranging between 8 – 9, conditioned PFA typically being more alkaline (pH 8 – 11);

• PFA contains quite a wide range of trace elements, including Arsenic, Barium, Boron, Cadmium, Copper, Cobalt, Manganese, Mercury, Molybdenum, Nickel, Selenium, Vanadium and Zinc. The vast majority of these elements are extremely insoluble in PFA, both because they are mainly held within the glassified Alumino-silicate matrix, and because most form insoluble compounds in alkaline conditions. The majority are not, therefore, of any chemical or biological significance. However a few, notably Boron and Molybdenum, favour the high pH and are more soluble;

• There is a very large body of evidence demonstrating that only 2-3% of the PFA mass is soluble in water, 97-98% being permanently insoluble. This has been shown using a combination of laboratory tests (incorporating batch tests and column leaching experiments) and field trials;

• Of the above suite of constituent trace elements, the only “List I substances” (whose entry into groundwater is prohibited under the Groundwater Regulations) are Cadmium and Mercury. Total compositional levels of Cadmium are likely to be around <1-2mg/l, leachate levels being in the range <1-2µg/l. Total compositional levels are therefore likely to be very low and consistent with background levels that occur naturally in UK soils. Leachate levels would also be very low (typically being less than 1/50th of UK Drinking Water Standards) and at or below background concentrations recorded in the upgradient monitoring boreholes around the site. Mercury concentrations are likely to be below method detection limits, expressed both as total compositional and leachate concentrations;

• Since PFA contains little or no organic matter, it does not have the potential to produce any measurable quantities of landfill gas; and

• Unlike fly ash from some other combustion processes (notably Municipal waste incineration), PFA does not contain organic trace toxic contaminants such as Dioxins and Furans above background concentrations.

3.3 Pollution Pathway – Landfill Liner

An engineered liner would be constructed across the base and sides of the installation using Bentonite Enhanced Soil (BES) of 0.5m minimum thickness.

The BES lining would be formed from a mixture of locally won sand and fine gravel bound with bentonite, a clay mineral which would provide a very low permeability

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and attenuative barrier. The BES layer would be specified to ensure a maximum permeability of 5 x 10-10m/s with an average value of 1x10-10m/s or less (the site has been modelled with a maximum permeability of 1x10-9m/s).

In view of the very low pollution risk posed by the proposed landfill, no “active management” of the site is warranted in relation to leachate or landfill gas.

3.4 Receptors

3.4.1 Aquifers

The geological sequence within the study area comprises River Terrace Deposits (RTDs) overlying Sherwood Sandstone Group bedrock (SSG).

The Environment Agency classify the RTDs as a Minor Aquifer, the SSG as a Major Aquifer. However, a shallow sequence of mudstones (of the Mercia Mudstone Group (MMG)) appear to have been encountered in boreholes immediately adjacent to the north / north-west of the Borrow Pit. The MMG overlies the SSG and may indicate that the MMG extends further south than shown by the geological map, or may represent mudstones within the SSG (there is a gradual transition between the SSG and MMG). The MMG is classified as a non-aquifer.

3.4.2 Abstractions

The majority of the site falls within the northern extent of Groundwater Source Protection Zone (GPZ) 3 for the Public Water Supply (PWS) borehole located at Hanch Reservoir near Longdon Green some 4.5km to the south-east.

The Environment Agency typically divides source catchments into three zones:-

• Zone 1 (Inner protection zone) – Any pollution that can travel to the borehole within 50 days from any point within the zone is classified as being inside Zone 1. This applies at and below the water table. This zone also has a minimum 50 metre protection radius around the borehole. These criteria are designed to protect against the transmission of toxic chemicals and water- borne disease;

• Zone 2 (Outer protection zone) - The outer zone covers pollution that takes up to 400 days to travel to the borehole, or 25% of the total catchment area – whichever area is the biggest. This travel time is the minimum amount of time that the Environment Agency consider pollutants need to be diluted, reduced in strength or delayed by the time they reach the borehole; and

• Zone 3 (Total catchment) – The total catchment is the total area needed to support the licensed abstractions of water from the borehole.

The Environment Agency’s “Landfill Directive Regulatory Guidance Note 3, Groundwater Protection: Locational Aspects Of Landfills In Planning Consultation Responses & Permitting Decisions, Version 4, 2002” states that the Environment Agency will object to any proposed landfill site affecting a GPZ 1, and that in the case of landfill sites below the water table where groundwater provides an important contribution to river flow, or on or in a major aquifer, or within Source Protection Zones 2 or 3, a HRA will be required demonstrating that no long-term site management is required to reduce the groundwater risk to acceptable levels. Rugeley Power Limited 3-3 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

There are four registered groundwater abstraction licences within 2 km of the site and another 14 up to 5 km distant (including Longdon Green PWS some 4.5 km to the south-east). The details of these abstractions are given in the HRA. It is noted that of the four closest abstractions, one is Rugeley Power Station’s on-site abstraction (Licence No 03/28/05/0056) and another (Licence No 03/28/05/0036) used to be located on the adjacent mixed use site, but has been decommissioned.

3.4.3 Groundwater Flow

Due to the high permeability of the RTD in comparison with the SSG, the groundwater flow within the RTDs is predominantly lateral, towards the River Trent. This has been confirmed from groundwater monitoring at the site since April 2006. Full details of the baseline groundwater monitoring can be found in the HRA.

It is considered that during operation of Rugeley Power Station’s on-site groundwater abstraction borehole, which is screened within the Sherwood Sandstone, it is likely that some “leakage” from the overlying RTDs may occur within a radius of approximately 1 km around the abstraction. Any such downward flow of groundwater from the RTDs into the SSG will be captured by the on-site well, however, rather than be dissipated within the SSG aquifer.

In the future, when Rugeley’s on-site well has eventually been decommissioned, it is likely that groundwater levels within the SSG will recover to the point that there may be some upward flow from the SSG into the RTDs, given the site’s location close to the River Trent in the base of the valley. This will have the effect of further reducing the risk of the landfill on water quality within the SSG and on the GPZ 3 in particular.

3.5 Numerical Modelling

A numerical model has been constructed to quantify the likely impact of the proposed landfill on groundwater quality over the entire lifespan of the landfill. The model has been constructed using conservative parameters in order to provide an “upper range” or “precautionary” approach to the assessment, in particular:

• Conservative site specific source term; • Worst case maximum hydraulic conductivity of 1x10-9m/s for the BES liner; • Worst case minimum hydraulic conductivity of 4x10-4m/s for the RTD aquifer; and • No dispersion or retardation within RTD aquifer.

The model predicts no discernible release to groundwater of any of the List I substances modelled, including Cadmium.

The model also predicts that releases of all List II substances modelled, including Arsenic, Boron and Molybdenum, will be significantly below UK Drinking Water Standards and/or Environmental Quality Standards (EQS) at the downstream monitor well, and hence would not have the potential to cause pollution.

It should be noted that the actual impacts are likely to be less than those predicted by this model, which have been assessed on a precautionary basis.

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3.6 Conclusion

The HRA indicates that the proposed landfill will not present a significant risk to groundwater beneath and in the vicinity of the site, and hence no active management, either of leachate or landfill gas, is warranted.

Rugeley Power Limited 3-5 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

4 Source Term Characterisation

4.1 Waste Types

The installation will be used for the disposal of PFA and FBA fines. These wastes would be mainly slurried using transport water taken from the B station’s cooling water purge, although conditioned PFA would be used to landscape the site.

4.2 Overview of Physio-Chemical Properties of PFA

There have been a large number of industry and independent studies which show that PFA deposits are typically homogeneous and on compaction attain very low hydraulic conductivities in the range 1x10-7 to 10-8m/s.

The low hydraulic conductivity of PFA is due to a combination of the spheroidal shape of the component ash particles and their particle size distribution (1 to 100µm, with most being approximately 20µm in diameter), which together allow the particles to pack tightly together upon compaction. This is an important characteristic because it severely limits the potential for interaction between a consolidated PFA deposit and the water environment.

PFA is composed largely of alumino-silicates which, due to rapid cooling from a molten state, take a predominantly non-crystalline ‘glassy’ form. The actual composition is dependent upon the mineral matter present within the fuel fired in the furnace and the effectiveness of combustion that has taken place. Table 4-A summarises the typical major mineral constituents of PFA.

Mineral Constituent Minimum Maximum Typical

SiO2 45 51 48

Al2O3 24 32 27

Fe2O3 7 11 9 CaO 1.1 5.4 3.3 MgO 1.5 4.4 2.0

K2O 2.8 4.5 3.8

Na2O 0.9 1.7 1.2

TiO2 0.8 1.1 0.9

SO3 0.3 1.3 0.6 Cl 0.005 0.015 0.008

P2O5 0.09 0.65 0.2

Table 4-A Major chemical constituents of PFA (Woolley et al. 2000)

All data expressed as % dry mass

The prevalence of alumino-silicates and aluminium and iron oxides, and the calcium and magnesium oxides is important as they strongly influence the chemical behaviour and biological availability of trace elements that are present (see below).

It should be noted that PFA contains no significant carbonates and is therefore not a source of carbon dioxide gas.

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PFA typically contains a wide range of trace elements associated with fossil fuel. These include cadmium and mercury, both of which are List I substances, a variety of List II substances including arsenic, boron, lead, molybdenum, selenium, zinc and vanadium; as well as major cationic and anionic components notably sulphate. The proportion of some of these substances in PFA differs from that in the source fuel due to vapour losses of the more volatile species during the combustion process. For example, levels of mercury and selenium in PFA are generally very much lower than might be anticipated from the fossil fuel content.

Table 4-B indicates the range in total trace element concentrations recorded in PFA derived from various UK power stations.

2 2

2

2 1 1

1 Parameter Approx. Range High West Drax Burton Cottam on-Sour Ratcliffe- Didcot A Didcot Marnham Drakelow

List I Substances Cadmium <0.1 3 4 3 <1-2.3 <1-4 <0.5-1 <1-4 Mercury 0.75 <1 <1 <1 <1 - <1 <1 List II Substances Arsenic 111 71 128 108 10-132 48-144 30-84 <10-140 Boron 14 181 132 75 10-211 94-164 342-386 <100-400 Chromium 33 44 50 55 38-145 32-61 36-55 30-145 Cobalt - 20 22 16 - - - 16-22 Copper 33 56 73 66 - - 55-103 <50-100 Lead 84 70 72 43 22-147 19-92 18-97 <20-150 Molybdenum 16 16 15 13 <10-63 - 1-34 <10-60 Nickel 37 42 50 35 - - 45-70 30-70 Selenium 3.2 <1 <1 <1 1-20 3.8-6.7 <0.5-0.8 <1-20 Vanadium - 117 133 96 - - 121-147 100-150 Zinc 101 142 136 65 37-306 21-114 45-261 20-300 Table 4-B Total trace element concentrations recorded in UK PFA

All concentrations expressed as mg/kg

1 Based on work undertaken by Jacobs reproduced with the permission of the operators 2 SLR Consulting 2000 and National Power 2000

The total inventory of trace metal concentrations in PFA is typically within the range that occurs naturally in soils (e.g. Alloway 1995).

The trace element contaminants present in PFA exist in a wide range of different minerals and other chemical forms, however they can broadly be regarded as being associated with the following generic ‘pools’:

• Water soluble fraction – the fraction present in solution / pore space • Exchangeable – ions bound to reactive surfaces by electrostatic forces • Complexed and adsorbed – bound specifically (i.e. covalently) to mineral surfaces • Occluded and co-precipitated – fraction bound within secondary minerals or insoluble metal oxides

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• Residual – fraction bound in the silicate structures.

The lability of these pools decreases from water soluble through to residual, but there is a broad distinction between the lability of the water soluble / exchangeable / adsorbed pools and the more refractory occluded / co-precipitated / residual fractions.

For all trace elements the largest fraction is that associated with the alumino-silicate matrix (i.e. the residual fraction). Being contained within the glassy fabric of the PFA, this component can be regarded as being permanently unavailable for leaching and is not therefore of any environmental significance. Significant proportions of a trace element’s total inventory may be occluded and/or co- precipitated, associated principally with secondary minerals (e.g. calcium sulphate) and oxides of iron, manganese and aluminium that form surface coatings on the vitrified PFA beads during combustion. The high pH typical of PFA is conducive to the stability of these oxides which, are therefore unlikely to contribute significantly to contaminant leaching other than in highly weathered deposits, or under reducing conditions. In turn these oxides provide on their surface, weaker ionic and potentially stronger covalent (or specifically sorbed) exchange sites, which will weakly retain trace elements. Broadly speaking this represents the ‘exchangeable fraction’, which in the large part will account for the solubility of trace elements in PFA and hence their concentration found in the transport water or ‘porewater’ of ash deposits.

The partitioning between the above generic pools varies depending upon the physio-chemical properties of the contaminant. For example a relatively high proportion of total boron and molybdenum is typically water soluble/exchangeable which renders them potentially quite leachable, whereas most other contaminants including arsenic, cadmium, lead and zinc are reasonably or highly insoluble in PFA, existing mainly as specifically sorbed, co-precipitated or mineral-bound fractions. Upon wetting only a relatively small proportion of the total PFA content of any given contaminant – even boron and molybdenum – will be solubilised and available for leaching, the large part of the ‘total’ inventory being retained in the solid-phase.

Table 4-C overleaf summarises the typical range of leachable elements found in UK PFA as extracted using the standard leachate test with 1:10 PFA:water ratio.

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Parameter Concentration (mg/l) Parameter Concentration (mg/l) Aluminium <0.1 to 9.8 Manganese <0.1 Arsenic <0.1 Molybdenum <0.1 to 0.6 Boron <0.1 to 6 Sodium 12 to 33 Barium 0.2 to 0.4 Nickel <0.1

Calcium 15 to 216 Phosphorous <0.1 to 0.4

Cadmium <0.1 Lead <0.2 Chloride 1.6 to 17.5 Sulphate 24 to 510 Cobalt <0.1 Antimony <0.01 Chromium <0.1 Selenium <0.01 to 0.15 Copper <0.1 Silicon 0.5 to 1.5 Fluoride 0.2 to 2.3 Tin <0.1

Iron <0.1 Titanium <0.1

Mercury <0.01 Vanadium <0.1 to 0.5 Potassium 1 to 19 Zinc <0.1 Magnesium <0.1 to 3.9 pH 7 to 11.7 Table 4-C Typical range of leachable elements for UK PFA (UKQAA, 2000) These data demonstrate leaching behaviour across a wide range of UK power station ash. The leachate results are more consistent than ‘total compositional’ analyses probably because of the total contaminant concentration present, only a very small proportion of which is leachable, the remainder being held in the silicate matrix or retained by the mechanisms discussed above.

Studies carried out by Jacobs on Barlow Mound Ash Disposal Site at Drax Power Station (“Conceptual Model and Hydrogeological and Landfill Gas Risk Assessment, May 2004”) indicate that the leachability of some elements notably molybdenum and sodium decreases as the PFA matures, probably due to a combination of lithophilic and pozzolanic reactions which is consistent with literature reports.

A number of lysimeter studies have been carried out in which columns of ‘conditioned’ PFA have been leached with water (e.g. Mattigod et al 1990). These experiments should be viewed with caution because in order to generate sufficient leachate for chemical analysis, very high throughputs of water have been applied which does not occur in reality under field conditions.

However, the data are of interest because they have highlighted differences in the leaching characteristics of different groups of contaminants.

Those species with a proportionally higher water-soluble and exchangeable component (such as boron, molybdenum and potassium) tend to be present in higher concentrations in the initial leachate and thereafter decline rapidly before reaching a steady state. This is because a relatively high proportion of their total inventory is labile and is therefore readily leached in the ‘first-flush’.

Another group of contaminants can be defined which are released slowly in the initial leaching stages, but whose concentrations increase as leaching progresses. In this case the water soluble and exchangeable fraction initially comprises a very small proportion of the total ash concentration, which increases under the influence of leaching as consequential reductions in pH increase their solubilities. Trace elements such as cadmium, copper, chromium, lead and zinc fall into this category.

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In the context of the subject installation, it follows that by far the highest risk to groundwater will occur during the operational phase. This is because the transport water discharged into the lagoons is likely to contain the highest concentration of the more leachable contaminants such as boron and sulphate. Following completion and restoration, the source term would become weaker, as the mobile constituents will to a large extent already have leached from the deposit.

Apart from being pertinent to understanding the potential leaching behaviour of contaminants through PFA, these studies also serve to demonstrate that the “chemical fingerprint” of ash leachate can be used to discriminate PFA effects from natural baseline conditions, and have been successfully applied by Jacobs at various other landfill sites for this purpose e.g. Rampton R2 Lagoon at Cottam Power Station and the Girton Ash Disposal Site in Nottinghamshire.

Apart from trace elements, PFA does not contain any other contaminants of potential environmental significance. PFA contains only trace levels of Polycyclic Aromatic Compounds (PAHs) and no discernible dioxins/furans in comparison with background levels in UK soils (see Document 5/2 for further details).

The above points can be summarised as follows:

• The low permeability of PFA serves to limit its potential for interaction with the water environment.

• With few exceptions total trace element concentrations in PFA are within the range found to occur naturally in soils.

• A substantial proportion of the total trace element content of PFA is typically associated with the residual fraction which is permanently unavailable for leaching and therefore of no environmental significance.

• The high pH of PFA minimises the solubility of the majority of trace elements but increases the solubility of a few, notably boron and molybdenum.

• There is evidence to suggest that the leachability of some elements including boron and molybdenum declines as the PFA deposit matures.

• The presence together in groundwater of leachable constituents of PFA such as boron, potassium, sulphate and sodium can be used to help discriminate PFA leachate from other potential influences on groundwater quality.

Further information on leachable testing collated for JEP Member Companies is presented in Appendix B, together with the site specific analyses.

4.3 Site-Specific PFA Analyses

Under the current regulatory framework the station has not been required to monitor the chemical composition of ash deposited in the adjacent lagoons 3 and 4. The only monitoring that has been required under the existing IPC Authorisation is for the supernatant discharge into the River Trent from Lagoons No 4 LH and RH which requires daily pH, weekly suspended solids, cadmium and mercury measurements which are analysed as a monthly composite, and visible oil. In addition six monthly “spot” samples of supernatant are subject to full elemental analysis for the site’s

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pollution inventory. This is discussed further in Section 4.4 “Ash supernatant analyses”.

The source term characterisation for the purposes of this hydrogeological risk assessment has therefore been based on:

• A site investigation carried out by Jacobs in June-Sept 2004 in which a series of ash samples were recovered from the lagoons for analysis.

• Collation and review of “ad hoc” chemical compositional records held by the operator and others for ash derived from Rugeley Power Station.

The results are summarised and discussed below and the corresponding laboratory’s certificates of analysis are presented in Appendix B.

4.3.1 Ash Samples Recovered from Rugeley Ash Lagoons

(a) Total trace element concentrations

The total inventories of trace metals in ash samples recovered from the ash lagoons are summarised in Table 4-D with the component data itemised in Table 4-E. These data correspond with concentrations extracted using refluxing aqua-regia. These and all environmental analyses performed as part of Jacobs’ site investigation were carried out by TES Bretby in Burton on Trent using UKAS accredited methods with the exception of total boron for which no UKAS accredited method was available.

The ash contains only very low levels of the List I substances mercury and cadmium, mean concentrations of these elements being 0.34 mg/kg and 1 mg/kg, respectively. These results are consistent with the normal range reported for PFA from other UK stations and are well within the range reported to occur in soils.

Arsenic levels ranged from 2.9-169 mg/kg with a mean value of 100 mg/kg which is also within the <10-140 mg/kg range reported for other stations. Mean levels were a little higher in dry-conditioned ash than lagooned ash although the range and 95 percentile figures were comparable in both ash types. Arsenic levels were two to three times higher than the normal range in soils (reported to be between 0.1-40 mg/kg). However, O’Neill (1995) reports that levels as high as 900 mg/kg may occur naturally in argillaceous sedimentary rocks such as shales, mudstones and slates.

Boron levels in ash ranged from 0.6 – 37 mg/kg and showed a similar trend to arsenic in that mean levels were a little higher in the dry-conditioned ash (33 mg/kg) compared with lagooned ash (22 mg/l). These levels are at the lower end of the range reported for UK power stations where levels in excess of 100 mg/kg have generally been recorded. Higher levels have also historically been recorded for ash derived from Rugeley Power Station. It is noted that the methodology that was used by the testing laboratory (aqua regia extraction) was not UKAS accredited and recorded levels were comparable to those obtained in a parallel test for water soluble boron carried out by the same laboratory. It is therefore considered likely that the results underestimate total boron levels present in the ash samples and the assessment should therefore focus on leachable boron.

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Ash type Hg Cd As B Mn Mo Pb Se V Zn Lagooned ash Min <0.1 <0.1 2.9 0.6 117 0.5 5.9 0.5 8.2 19 Max 0.37 1.6 169 37 285 9.3 125 10.9 236 207 Mean 0.31 0.71 85 22 218 5.4 61 5 124 105 95 percentile 0.37 1.59 169 33 275 9.0 118 9.5 224 196 Dry-conditioned ash Min 0.28 0.1 15.8 25 136 4.6 22 3.1 70 33 Max 0.52 2.0 158 37 420 10.4 143 9.5 181 275 Mean 0.37 1.38 120 33 327 8.7 107 7.7 152 226 95 percentile 0.50 1.92 154 37 413 10.4 138 9.5 180 275 Aggregated statistics Min <0.1 <0.1 2.9 0.6 117 0.5 5.9 0.5 8.2 19 Max 0.52 2.0 169 37 420 10.4 143 10.9 236 275 Mean 0.34 1.0 100 27 265 6.8 81 6.2 136 157 95-percentile 0.46 1.78 168 37 403 10.3 131 10.0 213 275 Range in UK Power 1 <1-4 <1 <10-140 <100-400 - <10-60 <20-150 <1-20 100-150 20-300 Stations Normal Range 2 0.01-0.5 0.01-2 0.1-40 - 20-10,000 0.1-40 2-300 0.1-5 3-500 1-900 Reported in Soils Table 4-D Total chemical inventories of lagooned and dry-conditioned ash deposited within Rugeley Ash Lagoons All data expressed as mg/kg

Notes:

1 As per data referenced in Table 4-B of this report 2 Data from “Heavy Metals in Soils” Second Edition, Ed BJ Alloway Blackie Academic & Professional 1995

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Sample Hg Cd As B Mn Mo Pb Se V Zn No 4 LH Scrape A1 0.32 0.44 53 21 225 2.8 46 3.1 139 78 No 4 LH Scrape B1 0.31 0.49 49 18 213 2.9 56 4 143 93 BH105 (0.2m)2 0.28 0.1 15.8 25 136 4.6 22 3.1 70 33 BH105 (1.7-1.9m) 1 0.1 0.1 2.9 0.6 179 0.5 5.9 0.5 8.2 19 BH105 (2m) 1 0.34 0.1 12.9 26 117 3.8 21 2.9 77.6 32 BH105 (4-6m)1 0.36 0.36 87 26 225 7.1 54 4.8 93 67 BH111A (1m) 2 0.28 2 158 30 280 8.3 116 7.1 181 257 BH111A (2.5m) 1 0.33 1.57 169 37 285 8.5 125 10.9 236 175 BH111A (4m) 1 0.37 1.6 168 25 255 9.3 104 7 201 207 BH111A (5m) 1 0.35 1.05 141 21 248 7.9 78 7 93 167 BH111 (0.3-0.4m) 2 0.52 1.41 138 37 374 8.7 122 8.3 172 253 BH111 (1.5-1.8m) 2 0.43 1.66 143 34 360 9.8 143 9.5 152 275 BH111 (3-3.4m)2 0.36 1.49 140 35 393 10.4 121 9 177 263 BH111 (4.7-4.95m) 2 0.36 1.59 127 36 420 10.3 117 9.3 159 275

Table 4-E Total chemical inventories of individual lagooned and dry-conditioned ash samples recovered from Rugeley Ash Lagoons

All data expressed as mg/kg

1 Lagooned sample 2 Dry-conditioned sample

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Levels of the remaining List II substances including manganese, molybdenum, lead, selenium, vanadium and zinc were within the range reported for other UK power stations and also within (mostly well within) the normal range in soils.

The data indicate that there are no significant differences in the total trace element inventories of lagooned and dry-conditioned ash occurring within the lagoons, or between ash derived from the former “A” station (which was the origin of the lagooned ash in Lagoon No 3) and the existing B station (which is the origin of the ash sluiced into Lagoons No 4 LH and RH and the dry-conditioned material that was used to backfill and cap Lagoon No 3 and carpet the active lagoons).

(b) Polycyclic Aromatic Hydrocarbons

Total levels of polycyclic aromatic hydrocarbons (PAHs) were very low in all ash samples recovered from the lagoons. In the large part, levels were below method detection limits, with a maximum value of 4 mg/kg benzo(k)fluoranthene being recorded in some of the samples obtained from BH111.

(c) Leachable Trace and Major Element Concentrations

Leachate tests were carried out on all ash samples recovered from the lagoons using standard methods (10:1 water/solid ratio by volume extracted for 24 hr and filtered prior to analysis using ICPMS).

Trace elements

Table 4-F summarises the results for the trace elements and Table 4-G displays the component data broken down to each exploratory hole and sample depth.

Overall it can be seen that leachate concentrations of all trace elements were found to be well within the normal range reported for other UK power stations, which applied to both the lagooned and dry-conditioned ash samples.

Ash leachate contained only trace levels of the List I substances mercury and cadmium, concentrations being in the range <0.0001 mg/l – 0.0003 mg/l. These levels are significantly below UK Drinking Water Standards (UK DWS) which are set at 0.001 mg/l for mercury and 0.005 mg/l for cadmium.

Leachable arsenic concentrations were also found to be consistently low across the samples, with mean levels both from the lagooned and dry-conditioned material being approximately 0.02 mg/l which is only a factor of two above UK DWS and well within Environmental Quality Standards for freshwaters (EQS).

The extractable boron concentrations measured in ash recovered from the installation were also well within the range reported for UK power stations, the mean level being 0.92 mg/l compared with an industry norm of <0.1-6 mg/l. However, it is notable that extractable boron levels were much lower in lagooned ash (mean level 0.52 mg/l) than in dry-conditioned ash (1.32 mg/l). These results are consistent with the understanding of the leaching behaviour of boron as described in Section 4.2 above and indicate strongly that a large proportion of the leachable pool of boron is lost upon the “first flush” i.e. during sluicing. Section 4.4 below considers the properties of ash supernatant generated during sluicing, which as far as boron and other such highly labile substances are concerned, represents the main potential

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risk to controlled waters associated with the ash lagoons. The contaminant source term represented by the settled ash deposit is much weaker in comparison. It is pointed out that in a borehole (no 111), which is believed to have encountered backfilled dry-conditioned ash within Lagoon No 3, leachable boron levels were consistent with depth down the full profile of the deposit (see Table 4-D). Given the leaching behaviour of boron as described previously, these data provide a strong indication that there has been no significant leaching of the deposit since this lagoon was closed and levelled off with dry-conditioned ash in 1995.

Leachable concentrations of all other List II substances were found to be very low in both lagooned and dry-conditioned ash recovered from Lagoons 3 and 4 were at the lower end of the range reported for the industry as a whole. It is notable that this also applies to molybdenum which is a relatively mobile constituent of ash. The mean leachate concentration was 0.06 mg/l with a maximum recorded level of 0.2mg/l. Most likely this reflects its low inventory in Rugeley ash (see Table 4-D).

Major elements

Leachate concentrations of major elements and ions are summarised in Table 4-H with the component data set out in Table 4-I.

The leachate results for both lagooned and dry-conditioned ash were well within the normal range reported for UK power stations. Sulphate levels were at the very lowest end of the reported range.

In general the results show a trend of lower leachate concentrations occurring in the lagooned ash in comparison to dry-conditioned ash, which mirrors the results that were obtained and discussed above for boron. This trend was particularly pronounced for sodium, whose mean concentration was 45% lower in lagooned ash, and for sulphate, whose mean concentration was 48% lower.

The reason for these trends is that the leachable pool is quite readily soluble in water and is therefore substantially reduced during sluicing to the lagoons.

The sodium and sulphate data recorded for borehole 111 are consistent with those for boron and indicate that the dry-conditioned backfill in Lagoon No 3 has not been significantly leached in the ten years since this lagoon was closed.

4.4 Ash Supernatant Analyses

The main risk to groundwater is associated with seepage of transport water through the geological barrier underlying the installation during its active phase i.e. when ash is being sluiced to the lagoons.

This is because the transport water arriving at the lagoons is likely to contain the highest concentration of the more labile constituents such as boron and sulphate and upon completion of the “first flush” the leachable pool remaining within the deposit, and therefore available for potential future leaching, will be lower.

The station has been required to monitor the quantity and quality of supernatant discharged from the active lagoons to river under the station’s IPC Authorisation. For trace metals, compositional monitoring has only been required of cadmium and mercury, although a full suite of analyses has routinely been undertaken on at least an annual basis since 1994. These data therefore provide a robust account of the

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quality of supernatant leaving the installation over the course of the past decade, and will therefore be representative of a wide range of different fuel mixes burned in the boilers and also the full range of potential lagoon operating regimes. During Jacobs’ site investigation a sample of ash supernatant discharge was recovered from the outfall structure and scheduled for chemical testing in order to verify the above data and provide a fuller compositional analysis.

4.4.1 Trace Elements

Table 4-J summarises the monitoring results for the trace elements, with the component data itemised in Table 4-L.

The data show clearly that the supernatant rarely contains measurable mercury or cadmium and hence negligible List I trace element.

Mercury concentrations were consistently below 0.0001 mg/l which are therefore more than an order of magnitude below UK DWS and EQS. The station monitoring results show that cadmium levels have been consistently below the method detection limit that was used (0.01 mg/l) and during Jacobs’s monitoring, which was carried out in July 2004 using a lower method detection limit, it was recorded at a concentration of 0.0001 mg/l which is a factor of five below UK DWS and EQS.

List II substances have also consistently been measured at low levels.

The mean arsenic concentration recorded by the station during the period 1992- 2006 was <0.05 mg/l. During Jacobs study in 2004 using a lower method detection limit a concentration of 0.023 mg/l was recorded. These data accord very closely with leachate test results on ash recovered from the existing lagoons and are only a factor of two above UK DWS (0.01 mg/l) and comply with EQS for freshwaters (0.05 mg/l).

The mean lead concentration measured was 0.82 mg/l. During the Jacobs study using a more precise and lower method detection limit, a concentration of <0.001 mg/l was recorded. However the data are elevated above the leachate test results for the existing lagoons. It is noted that a significant proportion of the trace element concentration recorded in the ash supernatant is derived not from ash but from river water abstracted to feed the station cooling system within which contaminant levels are concentrated by up to a factor of two owing to evaporative losses through the cooling towers. Thus the elevated levels may be due to the contribution of river water feed.

The mean boron concentration measured by the station was 0.76 mg/l which is at the lower end of levels typically found in supernatant. One possible explanation for this is that the supernatant contains a mixture of PFA slurry and FBA transport water which is therefore likely to contain proportionally lower concentrations of the more labile constituents generally found in PFA.

The monitoring records show that all other List II substances in ash supernatant arising from Lagoon No 4LH and RH, including manganese, molybdenum, vanadium and zinc, occur at very low concentrations (typically <0.05 mg/l). Concentrations comply both with UKDWS and EQS, where they exist.

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4.4.2 Polycyclic Aromatic Hydrocarbons

No routine analyses for PAH analyses have been undertaken on the ash supernatant discharge from the lagoons.

PAHs were scheduled for analysis in Jacobs’ site investigation and found to be below method detection limits.

4.4.3 Major Elements

Table 4-K summarises the monitoring results for the major elements.

Concentrations of sodium, calcium and chloride have consistently been recorded in the range 100-300 mg/l with lower levels of potassium (10-30 mg/l) and rather higher levels of sulphate (100-850 mg/l and a mean value of 425 mg/l).

Levels of all these ions are slightly higher than expected based on the outcome of the leachate tests which is probably due to a significant contribution and subsequent concentration of river water that feeds the station cooling system as referred to above. Sulphate levels are further enhanced through the dosing of the cooling water with small quantities of sulphuric acid to reduce pH and hence scaling of the system. It is estimated that only approximately one quarter of the sulphate concentration measured in the lagoon outfall is derived from ash, the remainder being accounted for by concentrated river water, sulphur trioxide dosing of the flue gases to enhance dust removal in the precipitators and acid dosing of the cooling water.

4.5 Model Source Term

Leachable analyses from Lagoon 3 (representative of dry conditioned ash) and Lagoon 4 (representative of slurried ash) have been used to characterise the source term used in the model as shown in Table 4-N.

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Ash type Hg Cd As B Mn Mo Pb V Zn Lagooned ash Min <0.0001 <0.0001 0.003 0.23 <0.002 0.007 <0.001 0.019 0.007 Max 0.0002 0.0001 0.032 0.70 0.015 0.08 0.034 0.13 0.038 Mean <0.0001 <0.0001 0.021 0.52 <0.005 0.05 <0.007 0.07 0.02 95 percentile <0.0002 <0.0001 0.031 0.68 <0.013 0.07 <0.03 0.12 0.04 Dry-conditioned ash Min <0.0001 <0.0001 0.003 0.68 <0.002 0.037 <0.001 0.059 0.007 Max 0.0003 0.0002 0.046 1.71 0.012 0.2 <0.001 0.124 0.057 Mean <0.0001 <0.0001 0.020 1.32 <0.004 0.07 <0.001 0.087 0.02 95 percentile <0.0003 <0.0002 0.040 1.71 <0.01 0.16 <0.001 0.12 0.05 Aggregated statistics Min <0.0001 <0.0001 0.003 0.23 <0.002 0.007 <0.001 0.019 0.007 Max 0.0003 0.0002 0.046 1.71 0.015 0.2 0.034 0.13 0.057 Mean <0.0001 <0.0001 0.020 0.92 0.004 0.058 0.004 0.08 0.02 95 percentile <0.0002 <0.0001 0.038 1.70 0.013 0.13 <0.016 0.13 0.05 Range in UK Power 1 <0.01 <0.1 <0.1 <0.1-6 <0.1 <0.1-0.6 <0.2 <0.1-0.5 <0.1 Stations Table 4-F Leachability of trace elements in lagooned and dry-conditioned ash deposited within Rugeley Ash Lagoons

All data expressed as mg/l

1 As per data referenced in Table 4-B of this report

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Sample Hg Cd As B Mn Mo Pb Se V Zn No 4 LH Scrape A1 <0.0001 <0.0001 0.010 0.69 <0.002 0.041 <0.001 - 0.053 0.009 No 4 LH Scrape B1 <0.0001 <0.0001 0.009 0.23 <0.002 0.072 <0.001 - 0.046 0.007 BH105 (0.2m)2 0.0003 0.0002 0.003 0.68 0.002 0.2 0.001 - 0.07 0.057 BH105 (1.7-1.9m) 1 0.0001 0.0001 0.014 0.23 0.003 0.007 0.034 - 0.019 0.023 BH105 (2m) 1 0.0002 0.0001 0.003 0.55 0.002 0.08 0.001 - 0.06 0.035 BH105 (4-6m)1 0.0001 0.0001 0.023 0.55 0.015 0.04 0.001 - 0.13 0.038 BH111A (1m) 2 0.0001 0.0001 0.013 0.85 0.012 0.054 0.001 - 0.059 0.007 BH111A (2.5m) 1 0.0001 0.0001 0.032 0.7 0.005 0.058 0.001 - 0.097 0.014 BH111A (4m) 1 0.0001 0.0001 0.028 0.49 0.004 0.047 0.001 - 0.076 0.007 BH111A (5m) 1 0.0001 0.0001 0.026 0.61 0.002 0.047 0.001 - 0.065 0.011 BH111 (0.3-0.4m) 2 0.0001 0.0001 0.023 1.69 0.002 0.041 0.001 - 0.109 0.011 BH111 (1.5-1.8m) 2 0.0001 0.0001 0.046 1.71 0.002 0.037 0.001 - 0.124 0.015 BH111 (3-3.4m)2 0.0001 0.0001 0.021 1.39 0.002 0.039 0.001 - 0.082 0.02 BH111 (4.7-4.95m) 2 0.0001 0.0001 0.011 1.61 0.002 0.045 0.001 - 0.076 0.011

Table 4-G Leachability of trace elements in individual ash samples recovered from Rugeley Ash Lagoons

All data expressed as mg/l

1 Lagooned sample 2 Dry-conditioned sample

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Ash Type pH Cl Na K Ca SO4 Lagooned ash Min 8 1 3.3 1.47 13.3 11 Max 11.3 6 9.2 12.4 66 69 Mean 10.5 3.1 6.1 8.2 33 37 95 percentile 11.3 6 9.1 12.4 61 62 Dry-conditioned ash Min 10.2 1 1.2 2.4 31 39 Max 11.1 11 19.9 11.3 61 92 Mean 10.6 3.3 11.0 5.6 46 71 95 percentile 11.0 9 18.9 10.2 60 90 Statistical overview Min 8 1 1.2 1.47 13.3 11 Max 11.3 11 19.9 12.4 66 92 Mean 10.6 3.3 8.6 6.9 36 54 95 percentile 11.2 8.3 17.6 12.3 64 87 Range in UK Power 1 7-11.7 1.6-17.5 12-33 1-19 15-216 24-510 Stations Table 4-H Leachability of major elements in lagooned and dry-conditioned ash deposited at Rugeley Ash Lagoons

All data expressed as mg/l other than as indicated

1 As per data referenced in Table 4-B of this report

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Sample Na K Ca SO4 Cl pH No 4 LH Scrape A1 7.71 2.21 24 41 9 9.4 No 4 LH Scrape B1 7.39 3.23 16 28 8 9.8 BH105 (0.2m)2 15.8 6.8 61 75 11 11.1 BH105 (1.7-1.9m) 1 4.41 1.47 13.3 11 4 8 BH105 (2m) 1 9.2 6.7 66 69 6 11.3 BH105 (4-6m)1 8.6 4.8 45 27 6 11.2 BH111A (1m) 2 1.2 3.5 31 39 1 10.7 BH111A (2.5m) 1 3.3 12.4 26 38 1 10.9 BH111A (4m) 1 5.3 12.3 23 38 1 10.6 BH111A (5m) 1 5.8 11.4 26 41 1 10.9 BH111 (0.3-0.4m) 2 19.9 2.4 - 67 1 10.7 BH111 (1.5-1.8m) 2 12.4 3.7 - 92 2 10.2 BH111 (3-3.4m)2 8.3 6 - 83 2 10.4 BH111 (4.7-4.95m) 2 8.5 11.3 - 70 3 10.6

Table 4-I Leachability of major elements in individual ash samples recovered from Rugeley Ash Lagoons

All data expressed as mg/l

1 Lagooned sample 2 Dry-conditioned sample

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Hg Cd As B Mn Mo Pb V Zn Station monitoring Nov 1992 – April 2004 Min <0.0001 <0.01 <0.03 0.22 <0.002 <0.02 <0.001 <0.02 <0.002 Max 0.0006 0.01 0.13 1.59 0.09 0.16 1.5 0.32 0.09 Mean <0.0001 <0.01 <0.05 0.76 <0.02 <0.05 0.82 <0.05 <0.03 95 percentile <0.0002 <0.01 <0.10 1.2 <0.07 <0.14 1.5 0.19 0.07 Jacobs monitoring <0.0001 0.0001 0.023 0.65 <0.002 0.026 <0.001 0.027 <0.002 July 2004 Environmental Assessment Levels UKDWS 0.001 0.005 0.01 1 0.05 - 0.025 - 5 EQS 0.001 0.005 0.05 2 - - 0.004-0.25 0.02-0.06 0.008-0.5

Table 4-J Trace element concentrations in supernatant arising from Lagoons No 4LH and RH in the period 1992 – 2006 All data expressed as mg/l

pH Cl Na K Ca SO4 Station monitoring Nov 1992 – April 2004 Min - 105 83 10 118 106 Max - 291 231 31 285 852 Mean - 187 155 18 190 425 95 percentile - 260 226 24 274 714 Jacobs monitoring 7.8 - 128 15.2 148 450 July 2004 Environmental Assessment Levels UKDWS <6.6>10 250 200 - - 250 EQS <6>9 - - - - 400

Table 4-K Major element concentrations in supernatant arising from Lagoons No 4LH and RH in the period 1992 – 2006 All data expressed as mg/l other than as indicated

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Hg Cd As B Mn Mo Pb V Zn 09 November 1992 <0.05 <0.01 <0.04 0.7 0.02 <0.03 0.03 <0.01 10 February 1993 <0.05 0.01 <0.04 0.9 <0.05 0.06 <0.05 0.02 7 July 1993 <0.001 <0.01 <0.04 0.72 <0.02 0.03 <0.02 0.05 15 February 1994 <0.001 <0.01 <0.04 0.22 0.02 <0.03 <0.03 0.02 13 February 1995 <0.001 <0.01 <0.04 0.4 <0.02 <0.03 <0.03 <0.01 15 January 1996 <0.001 <0.01 <0.03 1.08 0.02 <0.03 <0.03 <0.01 03 February 1997 <0.0001 <0.01 0.05 0.7 0.14 <0.03 <0.03 <0.01 15 January 1998 <0.0001 <0.01 0.1 1.59 <0.01 0.16 0.03 0.09 <0.01 11 May 1999 <0.0001 <0.01 0.06 1.1 <0.01 0.06 <0.03 0.09 0.02 15 June 2000 <0.0001 <0.01 <0.03 0.3 <0.01 <0.02 <0.03 <0.02 0.01 5 July 2001 <0.0001 <0.01 0.07 1.22 <0.01 0.08 <0.03 0.15 <0.01 11 July 2002 <0.0001 <0.01 0.03 0.66 <0.01 <0.02 <0.03 0.07 0.02 6 August 2003 <0.0001 <0.01 0.05 1.02 <0.01 0.06 <0.03 0.32 0.09 16 October 2003 <0.0001 <0.01 0.13 1.05 0.03 0.06 <0.03 0.19 0.02 30 April 2004 <0.0001 <0.01 <0.03 0.6 0.06 0.03 <0.03 0.05 0.05 July 2004 <0.0001 0.0001 0.023 0.65 <0.002 0.026 <0.001 0.027 <0.002 26 October 2004 <0.0001 0.01 0.06 0.9 <0.01 0.03 0.04 0.11 0.03 26 April 2005 0.0006 <0.01 <0.03 0.41 0.01 <0.02 <0.03 <0.02 0.03 21 July 2005 0.0002 <0.01 <0.03 0.66 0.09 <0.02 <0.03 <0.02 0.06 4 October 2005 <0.0001 <0.01 <0.03 0.76 <0.01 <0.02 <0.03 <0.02 0.07 22 November 2005 <0.0001 <0.01 0.04 0.75 <0.01 0.02 <0.03 0.08 0.03 16 March 2006 <0.0001 <0.01 <0.03 0.28 <0.01 <0.02 <0.03 <0.02 0.02

Table 4-L Trace element concentrations in individual supernatant samples arising from Lagoons No 4LH and RH All data expressed as mg/l

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pH Cl Na K Ca SO4 09 November 1992 205 19.0 235 195 10 February 1993 156 13.0 164 120 7 July 1993 203 20.0 227 15 February 1994 163 16.0 176 106 13 February 1995 118 15.0 143 283 15 January 1996 231 20.0 190 398 22 July 1996 216 470 03 February 1997 291 227 24.0 253 528 15 January 1998 132 31.0 191 417 11 May 1999 236 168 20.0 285 716 15 June 2000 127 114 10.0 118 286 5 July 2001 247 193 23.6 275 852 11 July 2002 165 149 17.7 172 511 6 August 2003 168 139 20.0 234 680 16 October 2003 206 180 22.8 236 680 30 April 2004 160 136 16.6 189 449 July 2004 7.8 128 15.2 148 450 26 October 2004 105 82.9 14.7 144 331 26 April 2005 150 126 14.4 165 315 21 July 2005 172 129 15.3 151 440 4 October 2005 175 149 18.6 166 467 22 November 2005 184 141 17.4 179 397 16 March 2006 197 139 13.3 148 248

Table 4-M Major element concentrations in individual supernatant samples arising from Lagoons No 4LH and RH All data expressed as mg/l

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Sample As B Cd Pb Mo K SO4 V No 4 LH Scrape A1 0.010 0.69 <0.0001 <0.001 0.041 2.21 41 0.053 No 4 LH Scrape B1 0.009 0.23 <0.0001 <0.001 0.072 3.23 28 0.046 BH105 (0.2m)2 0.003 0.68 0.0002 0.001 0.2 6.8 75 0.07 BH105 (1.7-1.9m) 1 0.014 0.23 0.0001 0.034 0.007 1.47 11 0.019 BH105 (2m) 1 0.003 0.55 0.0001 0.001 0.08 6.7 69 0.06 BH105 (4-6m)1 0.023 0.55 0.0001 0.001 0.04 4.8 27 0.13 BH111A (1m) 2 0.013 0.85 0.0001 0.001 0.054 3.5 39 0.059 BH111A (2.5m) 1 0.032 0.7 0.0001 0.001 0.058 12.4 38 0.097 BH111A (4m) 1 0.028 0.49 0.0001 0.001 0.047 12.3 38 0.076 BH111A (5m) 1 0.026 0.61 0.0001 0.001 0.047 11.4 41 0.065 BH111 (0.3-0.4m) 2 0.023 1.69 0.0001 0.001 0.041 2.4 67 0.109 BH111 (1.5-1.8m) 2 0.046 1.71 0.0001 0.001 0.037 3.7 92 0.124 BH111 (3-3.4m)2 0.021 1.39 0.0001 0.001 0.039 6 83 0.082 BH111 (4.7-4.95m) 2 0.011 1.61 0.0001 0.001 0.045 11.3 70 0.076 Minimum 3 0.003 0.23 <0.0001 <0.001 0.007 1.47 11 0.019 0.00005 0.0005 Mean / Geometric mean4 0.015 0.86 0.0001 0.0013 0.047 6.30 51.4 0.076 Maximum 0.046 1.71 0.0002 0.034 0.200 12.40 92 0.130

Table 4-N Derivation of Model Source Term Leachability Concentrations (mg/l) 1) Lagooned sample; 2) Dry-conditioned sample; 3) Where minimum is below detection limit (DL), the minimum is represented as 0.5 DL; 4) Where concentrations below DL, mean (& geometric mean) calculated using DL concentration represented as 0.5DL. 5) Geometric mean calculated where order of magnitude difference between minimum and maximum values

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5 Environmental Setting

5.1 Topography and Surrounding Land Uses

The Borrow Pit currently covers an area of some 7.9ha and is roughly triangular in shape. The ground around the installation to the north and east comprises agricultural fields with levels falling gently towards the River Trent which is located some 300m to the north-east of the site.

To the south / south-west, there is a raised embankment, to a height of some 8m above water level. Immediately to the south-east, east and north-east, there is low undulating ground, including a metalled road which bounds the lake to the north- east / east, which is raised a few metres above the water level.

Further to the south-west, is an area formerly occupied by the A station site. This area has been largely cleared and is now mostly vacant although part of the site is being used as a go-cart / scrambling track. To the west, there is a track which separates the lake from the adjacent Lagoon 4RH, which is bunded and raised above the general land surface by some 5m.

5.2 Historical Land Uses

A Landmark Group historic map and previous industrial land use search (No. 6085091- 1 & 2) has been carried out for the area in the immediate vicinity of Rugeley Power Station. The corresponding maps and industrial use report are presented in Appendix C. These data were supplemented by environmental information supplied by the Environment Agency also included in Appendix C.

The following site history has been compiled from reference to historic maps, archive reports and anecdotal information. The site history information is presented in chronological order.

The following historic maps have been referenced:

Map Sheet Scale Published 046_9 Ordnance Survey County Series 1:2,500 1884, 1902, 1923 SK0616, 0617, 0716, 0717 Ordnance 1:2,500 1962,1974 Survey Plan SK0616, 0617, 0716, 0717 Ordnance 1:2,500 1974,1988 Survey Plan 045_NE, 045_SE, O46_NW, 046_SW 1:10,560 1887 Ordnance Survey County Series 045_NE, 045_SE, O46_NW, 046_SW 1:10,560 1902 Ordnance Survey County Series 045_NE, 045_SE, O46_NW, 046_SW 1:10,560 1924 Ordnance Survey County Series 045_NE, 045_SE, 046_SW Ordnance 1:10,560 1938 Survey County Series SK01NE Ordnance Survey Plan 1:10,560 1955, 1968, 1981, 2000

Table 5-A Ordnance survey maps consulted in the historical review The maps indicate that the site and its immediate surrounding area were undeveloped until between 1902 and 1924 when a large sewage works with

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extensive filter beds was built to the north-west of the site which extended to within 350 m of the western boundary of the area of the former Lagoon No 3.

Prior to this time there was an “old quarry” on land immediately to the east of the area of the Borrow Pit and a scattering of marl pits to the north of the River Trent. The map for 1887 indicates a well within the area now occupied by Lagoon No 3.

The map for 1955 indicates the sewage works and filter beds as still being operational and the installation area as being undeveloped.

By 1968 Rugeley A Power Station had been built on land to the immediate north- west and south-east of the current Lagoons 3 and 4 and Lea Hall Colliery had been developed immediately to the south of the power station. A mineral railway had been constructed serving the colliery. The Rugeley A station area immediately up gradient of the current Lagoon 3 was occupied by two large coal stores No 1 and No 2, each of which was equipped with a large “drag scraper”. A raised ash lagoon (Lagoon No 1) is shown immediately to the west with a Borrow Pit (the A Station Borrow pit, now an amenity lake) adjacent to it on the western side. A small residential dwelling (Holly Bank Cottages) is shown within the current Lagoons 3 and 4 area.

The map for 1981 shows Lagoons 3, 4 LH and RH which had already been modified into their current arrangement. Rugeley B Power Station had been constructed immediately to the north-west of the A station site on the land previously occupied by the sewage works and filter beds. The Borrow Pit is indicated adjacent to Lagoon No 4 RH. The Lea Hall Colliery site is still evident with the drag scrapers adjacent to the ash lagoons.

The final map that was viewed, for 2000, indicates that Lagoon No 3 had been completed with Lagoons No 4 LH and RH still in use. The former A station site had been cleared and Lea Hall Colliery is shown as being disused.

The Environment Agency has indicated that according to their records there are five landfill sites located within 500m radius of the site as follows:

Environment Licence No. or Most Recent Date of Issue – Waste Types Agency Landfill Alternative Licence Holder Date of Site Reference Reference Surrender No. & OS Grid Ref. 9999/9628 Not Licensed Not Given Unknown Unknown SK 060 175 (CC7R) 9999/1059 Not Licensed Not Given Unknown Sewage sludge & SK 061 173 (LD46) demolition wastes 9999/9648 8/E/77/0072 C.E.G.B. 21/07/1977 – PFA, neutralised SK 066 170 (C10) 04/01/1994 boiler cleaning effluent & excavated material 9999/6646 8/E/79/0167 C.E.G.B. 06/11/1979 – PFA SK 068 165 (C8) (Solihull) 02/06/1982 9999/1160 Not Licensed Unknown Unknown Believed to be SK 070 166 (LD47) construction materials Table 5-B Summary of Landfills Records within 500m radius

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Licence No. 8/E/77/0072 corresponds with the existing installation and was relinquished in favour of being regulated under the station’s IPC Authorisation. A map showing the relative positions of the landfills is included in Appendix C.

5.3 Regional Geology

Drawing J24151C0/EIA/04-A shows the site’s geological setting.

The published geology (1:50,000 scale, British Geological Survey (BGS) sheet 140 (solid and drift), Burton upon Trent, 1982) shows the Borrow Pit site to be underlain by natural superficial deposits comprising First River Terrace Deposits which overlie strata of the Triassic Sherwood Sandstone Group (SSG). Recent alluvium is shown immediately to the north of the site (and is presumed to overlie the river terrace deposits). The River Terrace Deposits (RTD) are described as comprising well- stratified sands and gravels with thin clay seams. The Jacobs’ intrusive investigations of July/August 2004 and May/July 2006 did not encounter any Alluvium indicating its absence within the study area.

The SSG are shown to be conformably overlain by strata of the Triassic Mercia Mudstone Group (MMG) as ground levels rise away from the floodplain c. 1km to the south-west and the north-east, to the north of the alluvium. The Triassic bedrock is sub-horizontal, dipping gently at dips approximately 3° to the north-west. The SSG are underlain at depth by strata of the Carboniferous Coal Measures. Figure 5-A shows the published geology overlain on a site base map.

The northern part of the Borrow Pit is shown to be underlain by strata of the Bromsgrove Sandstone Formation (BSF) which conformably overlie strata of Cannock Chase Sandstone Formation (CSF). The CSF strata sub-crop beneath RTD across the southern half of the site. The BSF and CSF respectively represent the upper and lower divisions of the SSG. The CSF strata are described as coarse grained sandstones with conglomerate lenses and layers. The basal BSF strata which succeed the CSF are described as fine to coarse grained sandstones with occasional mudstone layers and some conglomeratic horizons, while the upper part of the sequence comprises inter-bedded thin sandstones and mudstones.

The Coal Measures have been mined by the nearby Lea Hall Colliery, which supplied coal to Rugeley Power Station. The colliery was closed in 1991, and all ground movements associated with the mining are considered to be complete. The Coal Measures strata are not material to this report and are not considered further.

5.4 Ground Conditions in the Site Area

5.4.1 Introduction

Following on from the description of the regional geology, the following sections provide details from a hydrogeological perspective on the ground conditions in the immediate area of the proposed installation. The information is derived both from recent site investigations and review of previous study reports.

The ground conditions that have been encountered can be grouped as follows:

• PFA/FBA Made Ground • River Terrace Deposits • Sherwood Sandstone and Mercia Mudstone Rugeley Power Limited 5-3 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

The following sections of text should be read in conjunction with the Geological Plan Drawing J24151C0/EIA/04-A and Borehole Location Plan, Drawing J24151C0/EIA/05-C. All of the borehole logs that have been referenced are presented in Appendix D.

5.4.2 Made Ground

Clearly there is no made ground within the footprint of the proposed installation as it is excavated within the RTDs. However, the surrounding area including the adjacent lagoons and bunds comprises made ground, and is described below.

Up to 6.5m of PFA has been deposited within the adjacent lagoons. Arisings of PFA encountered during the intrusive investigations were homogenous and generally appeared to be visually dry although in one borehole the PFA was moist becoming wetter with depth. As discussed in Section 4 there have been a large number of industry and independent studies which show that PFA deposits are typically homogeneous and on compaction attain very low hydraulic conductivities in the range 10-7 to10-8m/s, severely limiting the potential for interaction between a consolidated PFA deposit and the water environment.

In addition, c.1m thick layer of clay was emplaced at the base of the adjacent lagoons and which grades laterally into a consolidated PFA liner which extends all the way up the sides of the bunds. The clay bottom liner has been proved beneath Lagoon No 3 and Lagoon No 4 RH; access restrictions prevented borehole investigation of Lagoon No 4 LH. The bunds appear to comprise reworked River Terrace Deposits and some made ground (see below) faced on the inside with PFA.

The bund forming the south-eastern boundary to Lagoon No 4 RH i.e. adjacent to the Borrow Pit consists of c. 10m of made ground as proven in Borehole 116. The made ground typically comprises a clayey or ashy topsoil overlying gravelly sandy clay and sandy gravel (possibly reworked river terrace deposits) and in places appears to contain a proportion of PFA and/or FBA. Some 3m of made ground was encountered in borehole 127 which is located between the Lagoon 4 RH bund and the edge of the Borrow Pit. Between 2- 3m of made ground was recorded adjacent to the east (borehole 103) and south (borehole 104) of the Borrow Pit.

5.4.3 River Terrace Deposits

Significant thicknesses of RTD were recorded beneath the made ground, with the top of the underlying SSG strata proven in a number of the boreholes. In the vicinity of the Borrow Pit, a maximum of 16m has been intercepted (borehole 104 adjacent to the south) with the basal elevation appearing to vary between c. 48 – 54m OD (boreholes 101, 104 & 105). It is described as fine to coarse sand and gravel with cobbles and is fairly homogenous across the site.

Field falling head permeability tests were attempted during the August 2004 investigation however unsurprisingly the high hydraulic conductivity caused the raised water level to dissipate immediately. However, a number of pumping tests were undertaken during June 2005 in order to assist with the design of the dewatering scheme required for the proposed construction. The pumping tests provided information on the hydraulic properties of the terrace gravels in the vicinity of the Borrow Pit, as well as the degree of hydraulic connection between the gravels, the River Trent and the Borrow Pit. The pumping test information and assessment is included in Appendix E. The results of the constant rate test and

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recovery analysis plots are shown in Table 5-C below; those plots which showed a reasonable or good fit to data have been used to determine a range of values for use in the model. From the asymmetry of the groundwater levels and drawdowns observed during the pumping tests it appears that the River Trent contributes water to the groundwater system under pumping conditions, indicating that there is hydraulic connection between the river and the gravels.

Borehole Hydraulic conductivity (m/s) Comments on analysis Constant Rate Test Analysis Results B 9E-04 Good fit to test data C 1E-03 Good fit to test data D 2E-03 Good fit to test data E 9E-04 Good fit to test data F 1E-03 Good fit to test data G 2E-03 Good fit to test data 103 2E-03 Poor fit to test data 106 2E-03 Poor fit to test data 106 (P) 2E-03 Poor fit to test data Recovery Monitoring Analysis Results B 7E-04 Reasonable fit to test data C 4E-04 Reasonable fit to test data D 1E-03 Reasonable fit to test data E 8E-04 Reasonable fit to test data F 8E-04 Poor fit to test data G 1E-03 Good fit to test data 103 3E-03 Poor fit to test data 106 2E-03 Reasonable fit to test data 106 (P) 8E-04 Poor fit to test data Summary of reasonable and good fit data Minimum 4E-04 Mean 1.0E-03 Maximum 2E-03 Table 5-C Pumping Test Hydraulic Conductivities The above estimated minimum, mean and maximum values have been used to represent the hydraulic conductivity of the RTD within the model.

5.4.4 Sherwood Sandstone

Strata of the Sherwood Sandstone Group were proved in the majority of boreholes including BH101, 104, 105 and 107 at between 48m and 57m AOD, becoming deeper towards the south-east in the vicinity of the Borrow Pit.

The BGS report ‘The physical properties of major aquifer in England & Wales’, 1997 indicates relatively similar bulk hydraulic conductivities for the Bromsgrove Sandstone and Kidderminster (of which the Cannock Chase Formation is the local equivalent) Formations. The report gives values between 0.014 – 486 m/d (1.6 x 10-7 – 5.6 x 10-3 m/s) with a geometric 1.58 m/d (1.8 x 10-5 m/s) for the Bromsgrove Sandstone Formation and 0.14 – 69.2 m/d (1.6 x 10-6 – 8.0 x 10-4 m/s) with a geometric mean of 4.93 m/d (5.7 x 10-5 m/s) for the Kidderminster Formation, i.e. at least one order of magnitude lower than the overlying RTD.

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5.4.5 Mercia Mudstone

Mudstones (of the MMG) appear to have been encountered in boreholes BH108 and BH107 to the north of Lagoons 3 and 4 above the Sherwood Sandstone at approximately 61.5m and 59m AOD and of 0.5 and 2m thickness. This may indicate that the MMG extends further south than shown by the geological map, or may represent mudstones within the BSF. There is a gradual transition between the BSF and MMG. Given that the intrusive investigation could not reasonably probe the entire areal extent of the site, the potential exists for other pockets of mudstone to occur beneath and in the immediate vicinity of the installation.

The effect of the presence of the MMG on groundwater quality in the Sherwood Sandstone and overlying terrace gravels is well-recognised. It is the high concentrations of a range of trace elements and the major anions, sulphate, in particular, which make the groundwater abstracted from RTD overlying MMG in the Trent Valley particularly popular for beer production.

The clay mineralogy of the MMG is dominated by illite and chlorite (Anderton et al 1979) although lesser amounts of other clays such as smectite and kaolinite will also be present. Molybdenum and arsenic are found in clay silicates and are therefore generally higher in soils associated with shales / mudstones such as found in the MMG. Illite is a common source of boron, and may contain vanadium. Chlorite commonly contains manganese and zinc. The sulphate contained within the MMG derives from evaporitic horizons which can be highly extensive laterally.

It is therefore considered that MMG is likely to have a major influence on groundwater quality in the vicinity of proposed installation (see Section 6).

5.5 Hydrology

5.5.1 Rainfall

Site annual rainfall total were obtained from the Rugeley Power Station weather station that has been keeping records of rainfall at the locality since 1989. These annual rainfall values were referenced against evapotranspiration values taken from the Centre of Ecology and Hydrology (Wallingford) website, compiled from Meteorological Office MORECS data. Figure 5-C presents the annual average monthly rainfall since 1989 to present. The monthly average ranges between 40 and 75 mm/yr which are relatively low for the UK with average total rainfall over that period recorded at 652mm/yr. Potential evapotranspiration ranges between 550 – 600 mm/yr assuming typical soil moisture and root constant conditions for grass according to the CEH Wallingford.

To evaluate the potential amount of recharge permeating the site the effective rainfall was calculated using the above data. The effective rainfall is described as total rainfall less potential evapotranspiration over a normalised period. Using the figures stated above the calculated effective rainfall for the site ranges between 50 - 100 mm/yr. By comparison data obtained from the Environment Agency website for the Midlands region for both total rainfall and effective rainfall in 2003 is recorded at 619mm/yr and 123mm/yr respectively, although values for 2004 are higher at 839 and 250mm respectively. This compares reasonably well with the values obtained from the site rainfall data and the Wallingford data.

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During the operation of the site, there would not be vegetative cover thus evapotranspiration would be reduced, however conversely evaporation from open water is higher thus it is likely that overall the effective rainfall figures would be unchanged. Furthermore, it is likely that a cemented PFA layer would form near surface due to pozzolanic reactions (see Appendix B) which would indicate that saturation of the upper layer of the deposit would be rapid due to limited downward percolation. Once such saturation occurs infiltration would cease and any additional water would runoff. This coupled with high tension forces within PFA means that it is unlikely that the effective rainfall values will be totally available for infiltration. Additionally, there is a high probability that any percolating water which does migrate below the low permeability surface layer into any dry-conditioned backfill would be absorbed by further pozzolanic reactions at depth.

In summary, it is likely that the above-calculated effective rainfall values would represent an over-estimation of even the most conservative recharge condition.

However, within the given site conceptual model the driving head for seepage within the installation will be dependent solely on the vertical driving head above the base of the geological barrier. During operation, the head within the installation is likely to be equivalent to the surrounding groundwater level. The realistic worst case is 1 - 2m above the groundwater levels in the underlying RTD depending upon seasonal fluctuations in the aquifer. The water levels within the Borrow Pit will be set by weir control on the outfall towers from the site. However the seepage rate would actually be lower still as this head difference would clearly not be a continuous all year round occurrence. A post closure worst case, albeit not realistic, would be complete saturation of the final raised landform some 6m above rest groundwater levels, this gives rise to a maximum seepage rate of 378mm/a (i.e. 1.2 x 10-8m/s) for the worst case BES hydraulic conductivity.

Therefore infiltration rates within the model have been conservatively input as a single value of 400mm to ensure that the infiltration combined with the adjusted liner permeability reflecting the exaggerated head enables the maximum leachate seepage through the BES liner..

5.5.2 Surface Water

Surface water resources in the vicinity of the site are shown in Drawing J24151C0/EIA/06 Location of Watercourses and Water Bodies.

Two natural surface watercourses are indicated within the vicinity of the site, the larger River Trent and its tributary Brereton Brook. The River Trent, classified as a main river, flows some 300m to the north east of the site, at its closest point. The Brereton Brook flows within an open ditch immediately alongside the western boundary of Lagoon 3 some 500m to the north-west. The only other surface water body of any note is the Trent & Mersey Canal located approximately 150m to the south of the site.

The River Trent flows north-west to south-east and is classified under the Environment Agency’s River Quality Objective scheme as being compliant with grade RE3 (‘fairly good’) quality designation along a 11km stretch. Environmental quality data was obtained for the River Trent at Little Haywood approximately 8km upstream and at Handsacre High 1.5km downstream show river quality upstream being comparable to downstream.

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The site is indicated as lying outside of the floodplain of the River Trent and there are no records of flooding caused by overflowing water courses.

The Trent and Mersey Canal River Quality Objective along the Staffordshire and Worchester to Coventry Canal (a 20km stretch) is given as compliant with grade RE4 (‘fair’ quality).

5.6 Hydrogeology

The following summarises the information available on the hydrogeology of the site using the most recent hydrogeological monitoring data, previous investigations and published reports.

5.6.1 Groundwater Vulnerability

The Environment Agency has published a series of maps which identify the vulnerability of groundwater to contamination within any specific area. Vulnerability is assessed on the basis of the distribution of aquifers, the physical and chemical properties of the overlying soils and the characteristics of the strata in the unsaturated zone. The groundwater vulnerability map of South Staffordshire and East Shropshire, Sheet 22 (Drawing J24151C0/EIA/05-A) shows the area of the site as ‘soils of high leaching potential’ (the natural superficial deposits) over a major aquifer (Sherwood Sandstone). The site is actually given a default worst case vulnerability classification as it falls within an urban area (Rugeley) and it is assumed that the ‘soils’ have ‘little ability to attenuate diffuse source pollutants and non-adsorbed diffuse source pollutants and liquid discharges have the potential to move rapidly to underlying strata or to shallow groundwater’.

The Sherwood Sandstone aquifer is highly productive, heavily exploited and able to support large abstractions for public supply and other industrial purposes. The majority of the site falls within the northern extent of Groundwater Source Protection Zone (GPZ) 3 for the public water supply (PWS) borehole (Drawing J24151C0/EIA/05-B) located at Hanch Reservoir near Longdon Green some 4.5km to the south-east. A Zone 3 classification represents the total groundwater catchment area required to support an abstraction from the groundwater source. It is an indication of the potential risk to groundwater supplies and generally the closer the activity to the groundwater source the greater the risk.

The northern boundary of the GPZ 3 has an unlikely configuration as it constitutes a straight line orientated precisely east-west; it does not bear any correlation with the superficial or solid geology, nor with any surface hydrological features. The eastern boundary of the GPZ 3 appears to follow the boundary between the Sherwood Sandstone and Mercia Mudstone; the latter is classified as a non-aquifer. Therefore, the extent of the MMG as indicated from the intrusive site investigation may infer that the GPZ 3 boundary should be further to the south. In addition, the extent of the total catchment is dynamic and changes periodically dependent on the prevailing hydrogeological conditions, hydrology and surrounding abstraction regime. Consequently, the boundary is by no means absolute and is only an indicator of areas where developments may pose a risk to groundwater abstractions.

The Rugeley power station site has an abstraction well (Licence No. 03/28/05/0056) which is used to provide process water and is approximately 208 m deep and screened exclusively within the Sherwood Sandstone at depth. Given its screened depth the zone of influence of the abstraction will mostly be within the deeper

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sandstone. However, it is likely that some leakage from the overlying gravels occurs from a radius of approximately 1 km around the abstraction. Therefore during operation, its hydraulic influence on the groundwater in the shallower portions of the aquifer will be to draw any downward flow of groundwater (and any potential contaminants entrained within it) into the well and away from the GPZ.

The river terrace deposits are designated a minor aquifer under the Environment Agency’s ‘Policy and Practice for the Protection of Groundwater’ and are regarded as locally important for local water supplies and contributing baseflow to rivers. From areas of RTD cover beyond the default ‘urban’ classification of Rugeley, the superficial deposits are classified as having a high leaching potential with ‘deep, permeable, coarse-textured soils which readily transmit a wide range of pollutants because of their rapid drainage and low attenuation potential’.

5.6.2 Groundwater Flow Regime

Shallow groundwater flow beneath the site is likely to be influenced by the presence of the River Trent. This is confirmed by groundwater levels recorded within the monitoring boreholes (see Drawing J24151C0/EIA/06-A and Drawing J24151C0/EIA/06-B) which show groundwater elevations falling from around 66m OD in the south-west of the site to around 64m OD in the north-west. The principal direction of groundwater flow, based on 14 no. monitoring boreholes with response zones mainly in the RTD (and occasionally in the sandstone) indicate a groundwater flow direction towards the north-east (62° from north, as input into the model), consistent with movement towards the River Trent as would be expected, with a hydraulic gradient of 0.002.

Detail of the monitoring borehole network is provided in Section 6. Hydrographs for the groundwater monitoring data are included in Appendix F.

Seasonal variations in groundwater levels in response to water levels in the River Trent within the terrace gravels immediately beneath the lagoons are likely to be relatively small due to the high porosity and large areal extent of these deposits. This is confirmed by the two contour plots (Drawing J24151C0/EIA/06-A and Drawing J24151C0/EIA/06-B) based on recent monitoring data between May – October 2006:

• Figure 5-I, representing the ‘upper range’ levels (recorded in October 2006 following a wet autumn), • Figure 5-J, representing ‘lower range’ levels (recorded in July following a prolonged dry period nationally).

It is possible that if extremely high levels occur in the River Trent localised changes in the groundwater flow direction in the immediate vicinity of the river (100-200m) may occur but these are unlikely to extend back to the site and therefore should not significantly affect levels in the vicinity of the Borrow Pit.

The conjectured contours show relatively consistent orientation and flow direction but levels changed slightly seasonally with contours up to c. 0.5m higher in October than the corresponding contours in July.

It is emphasised that the groundwater elevations are taken both from pre-existing and recently installed boreholes with varied response zones – although the installations all have relatively discrete interval response zones, with horizons

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monitored varying across River Terrace Deposits, Mercia Mudstone & Sherwood Sandstone bedrock.

Thus some of the absolute values should be treated with some circumspection. However the distribution of groundwater elevations across the site is broadly consistent and therefore robust and coherent contours can be derived.

5.6.3 Licensed Groundwater Abstractions

There are four extant groundwater abstraction licences within 2 km of the site and another 14 up to 5 km distant (including Longdon Green PWS some 4.5km to the south-east). The details of the four closest to the site are summarised below:

Licence No. Location Daily Abstraction Amount (m3/d) 03/28/05/0036 Rugeley Power Station 2400.0 03/28/05/0056 Rugeley Power Station 3816.0 03/28/05/0016 Cawarden Springs Farm 18.2 03/28/05/0003 Wade Lane Farm 10.2

Table 5-D Details of licensed groundwater abstractions within 2km of the site It is noted that Licence No 03/28/05/0036 is a former abstraction located on the adjacent commercial and residential development site which is destroyed.

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6 Assessment of Hydrochemical Conditions

6.1 Introduction

Rugeley Power Limited has not been required to monitor groundwater under its existing IPC Authorisation which covers use of the temporary ash storage lagoons. However routine sampling of water from the Borrow Pit has been undertaken on initially an annual basis since 1994 and on an at least biannual frequency since 2003.

The application submitted for Lagoons 3 and 4 discusses groundwater quality in the wider context of the site and these installations. However, groundwater is generally considered to flow towards the river to the north-east and as such these installations are not directly up gradient of the Borrow Pit site. Indeed, as the following discussion indicates, there is no evidence to suggest that these installations are having an impact on groundwater quality within the Borrow Pit.

As discussed previously, water within the Borrow Pit is considered to be predominantly supported by groundwater within the river terrace gravels and is thus representative of baseline groundwater quality. Furthermore, in response to the PPC permit application submitted for the existing lagoons, the Environment Agency considered that further groundwater monitoring was required in order to better characterise the conceptual site model and to provide a more statistically valid data set for groundwater up-gradient and down-gradient of the site, against which control and trigger levels could be established.

The extent, nature and programme of monitoring undertaken are described, while the monitoring results are reviewed and interpreted below. The laboratory certificates of analysis are presented in Appendix B. The proposed future monitoring for the site is discussed in Section 8 ‘Requisite Surveillance’, and also within the appended ‘Site Monitoring Plan’ (Appendix I).

6.2 Monitoring

Jacobs installed 10 no. groundwater monitoring boreholes (101 – 103, 106 – 112, of which 102, 106 and 108 were dual installations) in 2004 targeting shallow groundwater beneath and in the vicinity of the former Lagoons 3 and current Lagoon 4, and proposed Borrow Pit installation, followed by a further 4 no. boreholes (124 – 127) in 2006. Groundwater samples were collected from the original boreholes between July-Sept 2004 following well development and purging and were submitted to TES Bretby Laboratories for chemical analysis using UKAS accredited methods. Further groundwater samples were collected on a monthly basis from the existing and new boreholes between May and October 2006.

Monitoring relevant to the Borrow Pit has been undertaken at 6 no. boreholes (8 no. installations) as listed in Table 6-A below; the locations are shown in Drawing J24151C0/EIA/05-C Appendix A. The corresponding borehole logs are provided in Appendix D. The laboratory data have been collated and are presented within a number of spreadsheet tables and plots in Appendix G.

An existing groundwater monitoring borehole (MW107) which was installed in 2002 by Peter Brett Associates on the former “A” station site to the south-west has also

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been used to help characterise baseline groundwater quality up hydraulic gradient of the Borrow Pit. Previous monitoring records for this borehole have been obtained (both from Peter Brett Associates and Wardell Armstrong who have carried out subsequent monitoring work on the former A station site) and have been incorporated into the baseline evaluation. MW107 was re-sampled by Jacobs in September 2004 to verify the previous results and provide an updated monitoring record for this location.

Borehole Response Zone Targeted Strata Reference (m bgl) BH101 14.0 – 19.5 Sand and Gravel* /sandstone (SSG) BH102A-S 3.0 – 5.0 Silty, slightly gravelly Sand BH102A-D 12.5 – 14.2 Sandstone (SSG) BH103 5.5 – 9.0 Sand & Gravel* BH106-S 4.5 – 7.5 Sand & Gravel* BH106-D 16.0 – 18.5 Sandstone (SSG) BH125 3.5 – 5.5 Slightly clayey Sand & Gravel* BH127 3.0 – 5.0 Sand & Gravel* MW107 ? ?Sand & Gravel*

Table 6-A Groundwater Monitoring

* River Terrace Deposits sequence, SSG Sherwood Sandstone Group, MMG Mercia Mudstone Group

The response zones of the boreholes targeting the installation are predominantly located within the River Terrace Deposits as shown in Table 6-B. The boreholes on the site are located variously up-gradient, within and down-gradient as indicated below in Table 6-C. The existing and proposed use of the site is briefly outlined to provide context to the monitoring locations. The two active Lagoons No 4 LH and RH are filled and emptied in sequence over a two to three year cycle, which is envisaged to continue until the anticipated closure of the station after 2016 when they will be completely emptied of ash and the site restored.

Borehole Location BH101 West of Borrow Pit (& south of Lagoon 4RH); up-gradient BH102A South of Borrow Pit; up-gradient BH103 East of Borrow Pit; down-gradient BH106 North of Borrow Pit (and east of Lagoon 4RH); down-gradient BH125 West of Borrow Pit (& west of Lagoon 4RH); up-gradient North-west of Borrow Pit; up-gradient (but south-east & down-gradient of Lagoon BH127 4RH) MW107 West of Borrow Pit (and south-west of Lagoon 4RH); up-gradient Table 6-B Distribution of Monitoring Boreholes Locations BH101 & BH106 were dipped and sampled monthly over a 6 month period as agreed with the Environment Agency commencing in May 2006 as part of the Lagoons 3 & 4 monitoring network. Boreholes BH125 and 127 have been included within the monthly monitoring as they became ‘serviceable’ following drilling in May and July 2006. Boreholes 102 and 103 have been included from June /July 2006 onwards.

In addition, some 22 no. water samples were collected from the Borrow Pit lake between November 1992 and March 2006, with frequency varying between one sample (1992, 1993 – 2001) to four samples (2005) annually. Rugeley Power Limited 6-2 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

All monitoring was carried out to current industry standards including suitable sampling methodology and the taking of QA field blanks as appropriate. All samples were analysed for the following suite of determinands using UKAS accredited methods where available.

• Trace Metals: Antimony (Sb), Arsenic (As), Barium (Ba), Boron (B), Cadmium (Cd), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb), Magnesium (Mg), Manganese (Mn), Mercury (Hg), Molybdenum (Mo), Nickel (Ni), Selenium (Se), Vanadium (V), Zinc (Zn) • Other Parameters: pH, Calcium (Ca), Chloride (Cl), Potassium (K), Sodium (Na), Sulphate (SO4)

Analyses have been carried out by TES Bretby.

With a few exceptions, the method detection limits for the trace metals were equal to or below UKDWS or MRV where appropriate. For calcium, chloride, potassium, sodium and sulphate a method detection limit at or below 1 mg/l was used. Unfortunately the analytical method for mercury that is used by the laboratory is 0.1ug/l– but has been now lowered to equivalent to the MRV (0.01ug/l) from September 2006 (and for future analyses). The Environment Agency have been informed of the changes in detection limits.

The spreadsheet tables in Appendix G essentially comprise a table for each borehole with results of each monthly monitoring round and all presented in the same format. The results have been processed to provide the range (minimum and maximum), the average, standard deviation and 95-percentile values. Where results are below detection, half the detection limit value has been used to derive the various statistical parameters. The average has been calculated as either an arithmetic or geometric mean, the latter where the range is greater than one order of magnitude. As there are generally a maximum of 6 values for each determinand for each borehole, it is considered that more sophisticated statistical analysis cannot be supported. A summary table of means has also been included.

By review of the tabulated data and plots, it is possible to establish the presence or not of trends or groupings / differences within the data set. Generally the results are fairly consistent for each borehole, but there is some variation between boreholes. There is no apparent areal trend i.e. there is generally no significant difference between up-gradient and down-gradient boreholes, as would be expected as the installation has not yet been developed.

6.2.1 Borrow Pit

Tables 6-C and 6-D present the results of chemical composition monitoring of the Borrow Pit water samples.

The Borrow Pit is considered to be an expression of shallow groundwater and therefore water quality is likely to reflect that of local groundwater. Despite being located immediately adjacent to the existing lagoons it shows no evidence of being materially affected by the lagoons.

The Borrow Pit contained no measurable cadmium or mercury and a very low arsenic concentration (0.006 mg/l) consistent with levels recorded in groundwater up gradient of the installation. Concentrations of boron (0.73 mg/l), molybdenum

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(0.036mg/l) and zinc (<0.002 mg/l) were all within the broad range recorded in groundwater up hydraulic gradient of the installation.

Sodium, potassium and chloride concentrations were all at the lower end of the range recorded up hydraulic gradient of the site and were also much lower than those recorded in ash supernatant discharging from the lagoons. Given that these ions are highly mobile, their presence in the Borrow Pit only at very low concentrations provides a strong indication that the Borrow Pit is not being materially affected by ash supernatant. These data reinforce the assessment made above that the boron levels recorded in the Borrow Pit do not emanate from the lagoons.

Sulphate levels recorded in the Borrow Pit were similarly at the lower end of the range recorded in groundwater up hydraulic gradient of the installation and were significantly less than those measured in ash supernatant.

In summary there is no evidence to suggest that water quality within the Borrow Pit is being materially affected by ash supernatant despite the Borrow Pit being located immediately adjacent and down hydraulic gradient to the active lagoons.

6.2.2 Up Gradient Groundwater

The monitoring is summarised in Table 6-E.

Mercury and cadmium concentrations have been shown to be at or below method detection limits (and at least an order of magnitude below UK DWS) in all monitoring boreholes.

Arsenic concentrations in the range <0.0001-0.014mg/l were recorded up gradient. The highest concentration was recorded at MW107 which is situated close to a suspected former “Victorian waste dump” located on the “B” station site.

There appears to be a degree of variability in boron concentrations within shallow groundwater in the vicinity of the site, which is consistent with previous investigations carried out by Jacobs at various other sites within the Trent Valley. Boron concentrations in the up gradient baseline boreholes ranged from <0.05mg/l to 5.9mg/l with the highest concentrations being recorded in MW107.

Molybdenum levels were measured in the up gradient boreholes between <0.001 and 0.132mg/l, the latter the mean value recorded in borehole 127. Zinc levels recorded in groundwater up gradient ranged from <0.01mg/l to 0.04mg/

The source of these locally elevated boron (and other trace element) levels is uncertain, but most likely are due to a combination of natural conditions and anthropogenic activities. The MMG strata which occur in the area above the SSG are known to be a significant source of arsenic, boron, manganese, molybdenum and sulphate (see Section 5.5). It is considered unlikely that PFA could account for the upper range levels of boron and molybdenum recorded up gradient of the site.

Sodium, potassium and chloride are all good indicators of ash supernatant although they are seldom found at concentrations that are of any environmental risk. Sodium concentrations up gradient of the installation ranged from 28 mg/l to 113mg/l. It is noted that the mean sodium concentration in ash supernatant is 168mg/l which is

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significantly lower and complies with UK DWS. Potassium levels of between 3.1 and 28mg/l were recorded. Chloride concentrations ranged from 21mg/ to 142mg/l.

Sulphate concentrations were generally high up gradient with concentrations ranging between 48 to over 1100 mg/l. Sulphate levels recorded in borehole MW107 exceeded the UK DWS and EQS. It is noted that a mean sulphate level of 446mg/l has been recorded in ash supernatant discharging from the lagoons since 1994.

6.2.3 River Trent

The River Trent flows in a west to east direction approximately 300m to the north of the Borrow Pit at its closest point. Chemical composition monitoring has been undertaken upstream and downstream of the Borrow Pit as part of the previous application; the locations are detailed below and show on Figure 5-B.

• River Trent upstream (SW1); Upstream of Lagoons 3 & 4

• River Trent downstream (SW3); Located immediately downstream of the Borrow Pit and downstream of Lagoons 3 & 4 and of the consented discharge point from the lagoons to Brereton Brook/River Trent.

Table 6-F presents the results of chemical composition monitoring of the River Trent surface water resources in the vicinity of the installation.

There is no significant difference in water quality of the River Trent downstream of the installation compared with upstream. As discussed in Section 5, at the time of year that the monitoring was undertaken (July-September 2004) shallow groundwater beneath and in the vicinity of the installation was found to flow broadly in a north-easterly direction towards the River Trent.

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Hg Cd As B Mn Mo Pb V Zn 09 November 1992 <0.001 <0.01 <0.04 1.13 0.06 <0.03 <0.03 0.01 10 February 1993 <0.001 <0.01 <0.04 1.23 0.07 <0.03 0.03 <0.01 7 July 1993 <0.001 <0.01 <0.03 1.39 0.04 <0.03 <0.03 <0.01 15 February 1994 <0.0001 <0.01 <0.03 0.52 <0.02 0.07 <0.03 <0.01 13 February 1995 <0.0001 <0.01 <0.03 0.65 <0.01 0.03 <0.03 <0.03 <0.01 15 January 1996 <0.0001 <0.01 <0.03 0.13 0.01 <0.02 <0.03 <0.02 0.70 03 February 1997 <0.0001 <0.01 <0.03 0.92 <0.01 0.03 <0.03 <0.02 0.02 15 January 1998 <0.0001 <0.01 <0.03 0.82 <0.01 0.02 <0.03 <0.02 0.04 11 May 1999 <0.0001 <0.01 <0.03 0.82 0.01 0.04 <0.03 <0.02 0.02 15 June 2000 <0.0001 <0.01 <0.03 0.82 <0.01 0.05 <0.03 <0.02 0.01 5 July 2001 <0.0001 <0.01 <0.03 0.89 0.09 0.05 <0.03 <0.02 0.02 11 July 2002 <0.0001 <0.01 <0.03 0.77 0.01 0.05 <0.03 <0.02 0.07 6 August 2003 0.0002 0.01 <0.03 0.82 0.02 0.03 <0.03 <0.02 0.02 16 October 2003 0.0001 <0.01 <0.03 0.70 0.01 <0.02 <0.03 <0.02 0.07 30 April 2004 <0.0001 <0.01 <0.03 0.65 0.09 0.03 <0.03 <0.02 0.02 26 October 2004 <0.0001 <0.01 <0.03 0.81 <0.01 0.03 <0.03 <0.02 0.08 July 2004 <0.0001 <0.0001 0.006 0.73 0.036 <0.002 26 April 2005 <0.0001 <0.01 <0.03 0.83 0.02 0.03 <0.03 <0.02 0.02 21 July 2005 0.0006 <0.01 <0.03 0.94 <0.01 0.05 <0.03 <0.02 0.01 4 October 2005 <0.001 <0.01 <0.04 1.13 0.06 <0.03 <0.03 0.01 22 November 2005 <0.001 <0.01 <0.04 1.23 0.07 <0.03 0.03 <0.01 16 March 2006 <0.001 <0.01 <0.03 1.39 0.04 <0.03 <0.03 <0.01

Table 6-C Trace element concentrations in (ground)water samples from the Borrow Pit All data expressed as mg/l

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Cl Na K Ca SO4 09 November 1992 99 14 121 65 10 February 1993 108 16 139 263 7 July 1993 87 13 120 204 15 February 1994 57 8 95 166 13 February 1995 68 10 93 164 15 January 1996 76 47 3 76 83 22 July 1996 77 54 10 94 175 03 February 1997 65 43 8 81 132 15 January 1998 69 45 9 76 136 11 May 1999 79 59 10 83 174 15 June 2000 84 60 10 96 185 5 July 2001 78 59 10 103 181 11 July 2002 74 52 9 91 174 6 August 2003 76 162 13 87 162 16 October 2003 77 52 9 63 147 30 April 2004 76 56 9 91 170 July 2004 123 62 9.5 195 26 October 2004 80 55 9 88 167 26 April 2005 99 74 11 109 206 21 July 2005 99 14 121 65 4 October 2005 108 16 139 263 22 November 2005 87 13 120 204 16 March 2006 57 8 95 166

Table 6-D Major element concentrations in (ground)water samples from the Borrow Pit All data expressed as mg/l

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Baseline groundwater conditions Analyte MW1071, 2 MW1071, 3 BH1013 BH1014 BH1254 BH1274 List I Substances Cadmium <0.0001 <0.0001 0.0001 <0.0001 <0.0001 <0.0001 Mercury - - <0.0001 <0.0001 <0.0001 <0.0001 List II Substances Arsenic <0.001 0.014 <0.001 <0.001 0.0055 0.0013 Boron 3.4 5.9 0.09 <0.05 3.14 1.33 Lead <0.03 <0.001 0.001 <0.001 <0.001 <0.001 Manganese 24.32 14.1 0.065 0.0046 8.685 2.400 Molybdenum - 0.082 0.001 <0.001 0.0017 0.1324 Selenium - 0.002 0.002 <0.001 <0.001 0.0014 Vanadium - 0.003 0.001 0.001 0.0018 0.0019 Zinc <0.01 0.006 0.040 0.0038 0.0030 0.0029 Other Parameters Calcium 425 262 74 88 186 134 Chloride 25 21 29 30 142 104 Potassium - 28 4.5 3.1 7.4 8.9 Sodium 73 51 28 10.5 112.7 97.4 Sulphate 1108 602 48 33.7 413.2 185.0 pH 7.3 7.0 7.3 7.3 6.6 7.1

Table 6-E Up gradient groundwater quality

All data expressed as mg/l Notes:

- No data available

1 Groundwater monitoring wells installed by Peter Brett Associates 2 Groundwater monitored by Wardell Armstrong in January 2003 3 Jacobs re-sampling taken in September 2004 4 Jacobs sampling taken May – October 2006 (mean: geometric mean calculated where order of magnitude difference between minimum and maximum values)

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Water resource Cd Hg As B Mo Zn Na K Cl SO4 River Trent Upstream Lagoons (SW1) 0.0001 <0.0001 <0.003 0.27 0.002 0.014 84 10.6 91 188 Downstream Lagoons (SW3) <0.0001 <0.0001 0.003 0.3 0.003 0.019 87 11.2 96 163

Table 6-F Water quality in surface water resources in the vicinity of the installation All data expressed as mg/l

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7 Hydrogeological Risk Assessment & Numerical Modelling

7.1 Introduction

This section presents the overall hydrogeological risk assessment for the installation in addition to the quantitative modelling. The assessment is based on the conceptual understanding of the existing site, proposed facility and the results of groundwater monitoring carried out around the site and the numerical modelling. The proposed installation covers approximately 8 ha and will comprise a single discrete excavated cell some 11m deep with both a basal and side slope engineered BES liner installed under a CQA system. It is anticipated that the installation will be operational for c. 10 years.

7.2 Source-Pathway-Receptor Linkages

The following potential source-pathway-receptor linkages have been considered:

• Seepage of leachate / ash transport water from the proposed facility through the engineered liner into shallow groundwater beneath the site

• Pollution of the Sherwood Sandstone major aquifer by the downward movement of any contaminant plume within the terrace gravels

• Pollution of River Trent by leachate / transport water arising from the installation via lateral flow in the terrace gravels

The results of the numerical risk assessment demonstrate (see Section 7.7) that there is no impact on groundwater contained within the terrace gravels, it therefore follows that there can be no impact on the Sherwood Sandstone or River Trent.

7.3 Source Characterisation

The proposed facility will accept disposal of PFA and FBA fines. These wastes will be mainly slurried into the site using transport water from the station’s cooling water purge. An application of up to 6m of dry-conditioned PFA will be placed to stabilise and create the desired final landform.

It is intended that the installation will continue to use water as a medium to transport PFA and FBA fines to the disposal site. The water will therefore not constitute waste and hence not prohibited waste in the context of the Landfill Regulations.

Based upon experience with the UK electricity industry the physio-chemical properties of PFA/FBA fines can be summarised as follows:

• The low permeability of PFA serves to limit its potential for interaction with the water environment • With few exceptions total trace element concentrations in PFA are within the range found to occur naturally in soils • A substantial proportion of the total trace element content of PFA is typically associated with the residual fraction which is permanently unavailable for leaching and therefore of no environmental significance

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• The high pH of PFA minimises the solubility of the majority of trace elements but increases the solubility of a few, notably boron • There is evidence to suggest that the leachability of some elements including boron and molybdenum declines as the PFA deposit matures

Site-specific analyses of the chemical composition of PFA/FBA fines and ash supernatant can be summarised as follows:

• There are very low /negligible concentrations of cadmium and mercury, and although present at higher concentrations, levels of List II substances are generally within the range occurring in soils • There are no significant differences in the total trace element inventories of lagooned and dry-conditioned ash • Leachate test concentrations of trace elements are very low which in the most part comply with UK DWS and/or EQS (where standards exist) • A large proportion of the leachable pool is lost upon the “first flush” i.e. during sluicing. Ash supernatant is therefore likely to be the most significant contamination source term with respect to leachable elements such as boron. The source term represented by the settled ash deposit is much weaker in comparison • There is no evidence from the borehole investigation of Lagoon No 3 for any significant leaching of metals down the profile since its closure in 1994 • It is noted that a significant proportion of the trace and major element concentration recorded in the ash supernatant is derived not from ash but from river water abstracted to feed the station cooling system, within which contaminant levels are increased by evaporative losses through the cooling towers among other contributing factors in some cases

Rugeley will continue to blend and burn a wide range of fuels and fuel-types. Although there may be a degree of variability in the chemical composition of the individual ashes from these fuels, the varied nature of the power station’s fuel diet and the extensive mixing of ashes means that the long-term ash composition of the material deposited at the installation is fairly constant.

In summary PFA does not intrinsically constitute a significant pollution source term because its total contaminant inventory is limited and the leachability of those contaminants that are present is for the most part very low.

7.4 Groundwater and Surface Water Monitoring

Water monitoring has been undertaken around the site in order to determine the flow direction, hydraulic gradient of groundwater and to characterise groundwater and surface water quality in the vicinity of the proposed facility.

• The monitoring was carried out between July - September 2004 and May- October 2006 when groundwater flow was demonstrably towards north-east and the River Trent. It is probable that the hydraulic gradient will vary seasonally; there may be a reversal during the winter period when river levels are high, although unlikely.

• Monitoring of groundwater up gradient of the facility i.e. background quality shows that List I substances, mercury and cadmium are at or below method detection limits. There appears to be some degree of variability in many

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other determinands with boron, sulphate, chloride, potassium and arsenic concentrations recorded at well below to in excess of UK DWS. The source of these locally elevated trace elements is uncertain, but most likely is due to a combination of natural conditions and anthropogenic activities. The MMG strata which occur in the area above the SSG are known to be a significant source of arsenic, boron, manganese, molybdenum and sulphate.

• The Borrow Pit is considered to be an expression of shallow groundwater and therefore water quality is likely to reflect that of local groundwater. Despite being located immediately adjacent of the existing lagoons it shows no evidence of being materially affected by the lagoons. The water quality within the Borrow Pit is similar to that monitored in boreholes up gradient.

• There is no significant difference in water quality of the River Trent downstream of the installation compared with upstream. At the time of monitoring, shallow groundwater beneath and in the vicinity of the installation was found to flow broadly in a north-easterly direction towards the River Trent.

7.5 Numerical Modelling

7.5.1 Introduction

The source term used has been derived from a combination of the site specific data to represent the installation as discussed within Sections 3.2.1 and 4.5.

The chemical constituents considered for inclusion within the risk assessment were cadmium, arsenic, boron, lead, molybdenum, potassium, sulphate and vanadium. Following on from the qualitative assessments outlined in the preceding chapters and the conceptual model developed in Section 3, a probabilistic risk assessment was undertaken using the latest edition of ConSim. ConSim uses the Monte Carlo simulation technique to evaluate the uncertainty inherent in the input values by randomly selecting values from each input parameter range and repeating the calculations to give a probability distribution of outcomes.

LandSim and ConSim both use the same fundamental numerical modelling approach to calculating the potential migration of contaminants from sources to receptors. LandSim is a less flexible tool which is ideal for modelling multi-stream waste deposits incorporating engineered liners, with the ability to model unsaturated vertical pathways. As a result it requires considerably more information than ConSim which is less bespoke and as a result individual model runs take considerably longer (an order of magnitude longer in most cases).

Neither LandSim or ConSim are specifically designed to accommodate below water table repositories, and to that end, either model would need adaptation of various parameters to simulate this condition. In this case where the proposed facility will not conform to the standard landfill design, having instead a mono waste stream and no unsaturated zone or vertical pathway, it was considered that ConSim was a much more efficient tool without changing the conceptual approach.

Furthermore, this maintains consistency with the previous PPC application for the adjacent Lagoons 3 and 4. In essence, ConSim has been used as a screening tool; if the modelling had shown elevated discharges, then it may have been necessary to consider to use a more sophisticated numerical modelling package. However the Rugeley Power Limited 7-3 Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

ConSim model does not indicate any significant discharges, therefore it is not considered necessary to construct a specific model.

The following sections outline:

• Definition of the source term in the model; • Model scenario considered and definition of input values; • Model assumptions and limitations; • Model output; and • Model sensitivity.

7.6 Modelling Scenarios and Assumptions

7.6.1 Source Term

The source term has used been derived from a combination of the site specific data to represent the installation as discussed within sections 3.2.2 and 4.5, and as also identified for modelling for the adjacent Lagoons 3 and 4.

The chemical constituents considered for inclusion within the risk assessment were:

• List I substances: Cadmium was modelled as it was found at levels at or just above detection limits. Mercury was discounted as it was found at lower concentrations.

• No organic chemicals were considered as it is demonstrated that the PFA at Rugeley is devoid of any such contaminant (see Section 4).

• List II substances: Arsenic, Boron, Molybdenum, Vanadium and Lead.

• Other substances of potential concern: Sulphate and Potassium.

7.6.2 Modelling Scenario and Input Values

The Borrow Pit has been modelled as a single cell, with a conservative non- declining source term. The changes in infiltration due to possible changes in head over time have been accommodated with a single ‘excess‘ input value rather than modelled as separate runs. The existing Lagoons 3 and 4 have not been included in the model as additional multiple sources as the lagoons are neither up or down gradient of the Borrow Pit and therefore do not impact on the groundwater flux beneath or down gradient of the site. Furthermore, lagoon 4 which is adjacent to the Borrow Pit will be dug out and removed as scheduled after 2016.

Background groundwater quality concentrations were excluded from the fate and transport modelling in order to demonstrate the proposed installation’s true contaminant loading on the subsurface. This provides a more robust view of the “expected” impact on groundwater beneath the installation were the water quality within the underlying river terrace gravels pristine. As discussed in the previous section, a number of specific contaminants were measured at significantly greater concentrations immediately up gradient of the site.

The ‘unsaturated’ zone cannot be excluded from the model and as the base of the proposed facility is below the water table, this layer has been allocated 100%

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moisture content (to represent full saturation). This layer has been used to represent the liner. The engineered BES liner has been allocated a conservative range of permeabilities between 1x10-9 and 1x10-11m/s, with a most likely intermediate value of 1x10-10m/s. With the adoption of a CQA system, the higher end permeabilities would be avoided.

Retardation and vertical dispersion have been included with respect to the BES liner. Degradation has not been included in any pathways. Retardation and dispersion have not been included within the aquifer pathway.

ConSim (or LandSim) do not model lateral seepage through the liner on the sidewalls. Quantification of seepage through the BES along the sides of the lagoons was evaluated using a conservative Darcian saturated soil approach. Assuming a likely permeability of 10-10m/s for the BES liner and taking into account a realistic head of 0.5m over 1 metre incremental sections of extent of 10m, the results indicate flows of c. 0.0013 l/s. Assuming the same likely permeability for the basal BES estimates a downward flow of 0.0081 l/s i.e. the side slope leakage represents c. 15% of the total seepage (which also reflects the relative surface areas). However, the areas defined in the model for the source terms are at least 20% larger than the actual basal area because they are based upon the surface area. The model therefore overestimates the flow through the base by a very similar degree to which it underestimates the flow through the sides and the net effect is not significant.

The single infiltration rate of 400m/a has been allocated to be in excess of the calculated seepage rate of 378mm based on the worst case hydraulic conductivity (1.2e-0.8m/s, adjusted from 1e-9m/s by an extreme vertical hydraulic gradient of 12) and exaggerated maximum head of 6m.

No impacts on the groundwater regime within the Sherwood Sandstone were considered within the model as it was concluded that any downward flow of groundwater occurring from the gravels into the sandstone will be drawn into the on site abstraction well which is used to supply boiler water to the power station (see Section 5). However given the relatively high horizontal hydraulic conductivities within the underlying RTD, it is considered extremely unlikely that there is significant downward flux from the RTD to the SSG. The receptors considered included the base of the ‘unsaturated zone’, in this model equivalent to the base of the BES liner, for the List I determinand Cd, and the model default ‘Borrow Pit’ receptor, located on / immediately down-gradient of the most down-gradient point of the source (in this case on the north-eastern installation boundary), for the List II and other determinands.

The input values for other parameters were taken from site-specific results where available and supplemented with authoritative literature sources where appropriate.

The input values and justification are tabulated and included in Appendix H.

7.6.3 Model Assumptions and Limitations

The principal assumptions, which apply to most numerical groundwater modelling approaches, include:

• Homogeneous & isotropic hydrogeologic media; • Laminar flow, in one direction only with constant velocity;

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• No dispersion or diffusion other than that specifically included; and • Constant contaminant and geosphere properties.

Specific limitations of the model were addressed as follows:

• Lateral flow through the BES liner up the sides of the lagoons could not be realistically modelled. The model area of the basal liner was significantly larger than the actual situation and this therefore adequately takes into account the flow through the lagoon sides (see section 7.2.1).

• ConSim considers a vertical hydraulic head of unity in all situations but the soakaway option. Therefore in order to adequately represent the worse case vertical hydraulic head, when there is a potentially higher head within the Borrow Pit compared to the rest groundwater levels outside, the hydraulic conductivity of the basal liner was proportionally increased by a factor equivalent to the driving head. In addition, in order to incorporate into the model the ‘water / leachate’ driven through the liner by the increased hydraulic gradient, the infiltration rate was set above the capacity of the basal liner under these conditions.

7.7 Model Results

The selected results of the ConSim risk assessment are also enclosed in Appendix H. Also enclosed on a CD is an electronic copy of the ConSim model (EA copy only).

List II (and unlisted substances e.g. potassium) groundwater concentrations as calculated at the immediate down gradient boundary of the Borrow Pit were assessed against relevant UK DWS or EQS. The List I substance concentration (cadmium) as calculated at the base of the liner (as there is no unsaturated zone) was assessed against the minimum reporting value (MRV).

The predicted impacts for each chemical constituent modelled are presented in Table 7-A. The table indicates the following predicted impacts on groundwater:

• No discernible releases of List I substances;

• Concentrations of List II substances are significantly below the UK DWS (or other available criteria in absence of UK DWS); and

• Sulphate and potassium concentrations are significantly below the UK DWS.

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Predicted 95%ile Concentrations (mg/l) UK DWS Substance [Time to peak concentration (years)] MRV (mg/l) Base of Liner Borrow Pit Receptor List I substances Cadmium 0 (no breakthrough) 0.0001 0.005 List II substances Arsenic 0 (no breakthrough) 0.025 Boron 0.2 (25) 1 Lead 0 (no breakthrough) 0.01 Molybdenum 0.007 (1000) (0.07)1 Vanadium 0.011 (1000) (0.02 – 0.06)2- Other substances Potassium 1.2 (25) (12)3 Sulphate 11 (25) 250

Table 7-A Model results 1 World Health Organisation drinking water guideline 1984; No UK DWS 2 EQS; no UK DWS 3 UK DWS 1989, no UK DWS 2000

7.8 Model Sensitivity

In order to assess the sensitivity of the model predictions to variations in the source term, the model was run using probability distribution inputs for many of the parameters. The contaminants were input as triangular or log triangular distributions based upon the minimum, mean, maximum leachate analyses from combined dry conditioned and lagooned PFA samples collected from the Rugeley site. In addition other model parameters such as clay liner permeability and aquifer permeability were also assigned probability distributions. Justifications and selection of conservative input values are tabulated in Appendix H.

ConSim incorporates a sensitivity analysis module i.e. the model assesses whether a small change in an input parameter results in a relatively large change in model outcome. The analysis can only be applied to those parameters where there is a range of inputs; single values are not included. A positive correlation indicates that increasing the input value increases a specific output value while a negative correlation indicates an inverse relationship. The magnitude of the sensitivity is indicated by the value of the number (irrespective of whether it is positive or negative) from zero to one. A value of one indicates a perfect linear correlation (positive or negative) between the input value and the result. A value of zero indicates no relationship. .

Where the sensitivity identified by the model was greater than +/- 0.5, details were noted and the impact on the model assessed. The analysis indicated that the predicted following outcomes are most sensitive:

• A positive correlation was observed between receptor concentration and liner hydraulic conductivity for particularly boron, potassium, sulphate and molybdenum i.e. those determinands with no or relatively low retardation. As expected, an increase in essentially the driving head and increased permeability would lead to an increase in concentrations, and vice versa. The infiltration has been conservatively set assuming an extreme head of 6m

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and to be in excess of the liner permeability, while the barrier hydraulic conductivity is based on conservative values for an engineered BES liner.

• A similar if negative correlation was observed between travel times and liner hydraulic conductivity for again boron, potassium, sulphate and molybdenum i.e. those determinands with no or relatively low retardation. This is clearly associated with the correlation above, where increases in infiltration / driving head and permeability will lead to faster i.e. shorter migration times.

7.9 Model Summary

A robust hydrogeological risk assessment model has been constructed using conservative parameters. The model predicts no discernible releases of List I substances (i.e. cadmium) and contributions to groundwater significantly less than UK DWS for all other chemical constituents modelled.

7.10 Hydrogeological Risk Assessment Summary

The overwhelming majority of transport water which would enter the Borrow Pit would be discharged under consent to the river. The main potential source of groundwater pollution associated with the proposed facility would be the seepage of leachate / transport water through the engineered BES liner constructed along the base and side walls of the facility.

A total seepage rate of 9.4 x 10-6m3/s (0.009l/s) is predicted for the most likely situation that there is a head differential of 0.5m and liner permeability of 1x10-10m/s. The outward flow of leachate / transport water from proposed facility would therefore be very low even under a worst case. Since the permeability of the BES liner is likely to be at least an order of magnitude less than that used in these worst case estimates and the head difference likely to be negligible, the actual seepage rate through the sides and base of the proposed facility is also likely to be at least an order of magnitude less and essentially negligible.

Based upon a most likely permeability of 1x10-3m/s and the hydraulic gradient of 0.002m/m measured in the monitoring wells at site, and assuming a conservative thickness of 2m, the minimum total flow rate through the gravels beneath under the site is 0.012m3/s (1.2l/s).

Conservative estimates of flow in the gravels are therefore significantly greater than the worst case estimates of downward flow of transport water from the lagoons. This indicates that dilution factors under the installation will be in excess of 100.

The leachate / transport water contains no significant concentrations of List I substances and only very low concentrations of List II substances which are generally at or below UK DWS. The high potential dilution factor on entering shallow groundwater in combination with the low concentrations will therefore render insignificant all predicted emissions from the site.

Finally it is emphasised that the adjacent installations have been utilised for over thirty years with barriers of lower specification and despite extensive monitoring carried out around the site there is no evidence for the discernible release to groundwater of any List I substance or pollution by any List II substance.

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Based on the above, it is considered that the proposed design of the facility is “fit for purpose” and meets the requirements of the Landfill Directive, and that the installation will comply fully with the Groundwater Regulations.

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8 Requisite Surveillance

8.1 Introduction

This section considers the requisite surveillance for the installation in the context of the Groundwater Regulations 1998.

There are written procedures in place covering environmental monitoring related to Rugeley and all analyses are undertaken by independent laboratories using UKAS accredited methods where they are available.

The existing monitoring procedures have been reviewed and revised in the context of the Conceptual Site Model and Hydrogeological Risk Assessment with due regard to the requisite surveillance requirements of the Groundwater Regulations. The following section briefly describes the proposed monitoring regime under PPC. A more detailed Site Monitoring Plan is enclosed in Appendix I.

The proposed monitoring programme takes into account the predicted low impact of the installation. Where possible, it is proposed to co-ordinate the monitoring with that required for the adjacent former Lagoon 3 and current Lagoon 4 to avoid unnecessary duplication.

8.2 Source Term and Leachate

The PFA to be deposited within the engineered Borrow Pit is ultimately the source term for any potential contaminant emissions. However, because the PFA will be mainly slurried into the site, it is the ash transport water pumped to the lagoons which represents the principal risk to ground and surface water.

It is therefore proposed that monitoring of the source term, as represented by ash deposited within the installation, takes the form of both:

• Fresh pulverised fuel ash collected from the ash hopper • Transport water discharges from the active lagoons

8.2.1 Fresh Pulverised Fuel Ash

The majority of the PFA deposited will be in slurried form. While the total chemical composition of slurried PFA will be very similar to fresh ash, leachable concentrations of the more labile constituents such as boron, molybdenum and base cations will be lower because these species will be depleted on slurrying.

However, because of the practical difficulties in obtaining representative samples of slurried ash from the lagoons, it is proposed that fresh ash is instead recovered from the station ash hoppers and used as a proxy for ash deposited in the installation. This is proposed on the understanding that while the total chemical inventory of fresh ash will be comparable to that of slurried ash, the concentration of leachable constituents are likely to overestimate actual concentrations in slurried ash.

It is proposed that duplicate samples of fresh ash are collected from the ash hoppers on a six monthly basis and are extracted/analysed as follows:

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Total compositional analyses using refluxing aqua-regia

Full elemental suite including Al, Sb, As, B, Cd, Cr, F, Mn, Hg, Mo, Se, and V.

Leachable trace and major ion analyses*

Full elemental suite including, Al, Sb, As, B, Cd, Ca, Cr, F, Mg, Mn, Hg, Mo, K, Se, SO4, and V plus pH, Electrical conductivity, K, Mg, Ca, Na and SO4, *leaching test BS EN 12457 (BSI 2002) in accordance with latest Environment Agency guidance: 10:1 ratio (as simulating leaching from slurried ash), results reported as mg or ug/l.

The above analytical suite is considered to be appropriate because it includes all List I substances which could potentially occur in PFA or PFA leachate and the principal List II substances. Sulphate is included as it is a major constituent of ash leachate and could potentially occur at concentrations of significance to controlled waters. The base cations sodium and potassium are included as indicators of ash leachate, both being significant constituents of ash leachate but not usually present at concentrations that could give rise to any environmental cause for concern.

All samples would be analysed by an independent laboratory using UKAS accredited methods where available. For the leachable metals, the method detection limits would be at or above UK DWS/EQS whichever the lower (where they exist).

8.2.2 Supernatant Discharge (Transport Water)

It is proposed that metals analyses are carried out on “spot” samples collected on a quarterly basis and are analysed for a wide range of parameters targeting the more significant constituents of ash as follows:

• pH • List I substances - Cd, Hg • List II substances - As, B, Mo • Other substances - Na, K, SO4

As for the PFA analyses, all supernatant samples will be analysed by an independent laboratory using UKAS accredited methods and with method detection limits at or above UK DWS/EQS whichever the lower (where they exist).

8.3 Groundwater

The risk assessment has determined that there should be no discernible release of any List I or List II substance to groundwater in excess of UK DWS or EQS beneath the installation. Only limited monitoring of shallow groundwater is therefore proposed around the installation in order to demonstrate compliance with the Groundwater Regulations. However, as the conceptual model has been based on a relatively limited set of groundwater levels and compositional data, it is proposed that the control and trigger levels set out below should be re-considered on the basis of a more statistically valid data set following routine monitoring over an extended period.

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It is proposed that groundwater conditions be monitored at three boreholes as follows:

• Up gradient borehole: BH101 located south west of the site • Down gradient boreholes: BH103 and BH106 located north of the site

Figure 5-B Appendix A shows the location of the proposed monitoring boreholes. It is envisaged that for the first six months after issue of the PPC permit, groundwater levels in these three boreholes would be monitored on a monthly basis at which point monitoring would be continued on a quarterly intervals.

It is proposed that compositional monitoring be carried out for the following determinands:

• Electrical Conductivity, pH, Aluminium, Antimony, Arsenic, Boron, Cadmium, Calcium, Chloride, Chromium, Fluoride, Magnesium, Manganese, Mercury, Molybdenum, Potassium, Selenium, Sodium, Sulphate and Vanadium.

In the case of the trace metals, the method detection limits would be equal to or below UKDWS or MRV, whichever is lower. A method detection limit at or below 1 mg/l would be used for Potassium and Sulphate. The analytical suite includes all potential List I substances in PFA and a selection of the more leachable List II and other constituents which are collectively of most potential significance.

All analyses would be undertaken using UKAS accredited methods.

8.4 Surface Water

Based on this risk assessment it is not considered that there will be a discernable emission to groundwater of any List I or List II substance and therefore there is no pollution risk to River Trent downstream of the site. As such it is not considered that any further monitoring is warranted of the River Trent, either upstream or downstream of the consented discharge point.

8.5 Proposed Control & Trigger Levels

The following control and trigger levels are proposed for all monitoring boreholes which are consistent with those in use for the Temporary Ash Lagoons:-

BH101 BH103 BH106S Analyte Unit Control Trigger Control Trigger Control Trigger Arsenic µg/l 50 500 50 500 50 500 Boron mg/l 10 20 10 20 10 20 Cadmium µg/l 0.5 1 0.5 1 0.5 1 Mercury µg/l 0.2 0.4 0.2 0.4 0.2 0.4 Molybdenum µg/l 350 700 350 700 350 700 Table 8-A Proposed Control and Trigger Levels

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9 Conclusions

Based on this hydrogeological risk assessment it is considered that the proposed installation would comply fully with the Landfill Regulations 2002 because:

• It would have an engineered low permeability BES liner constructed under a CQA system along both the base and side walls

• The hydrogeological risk assessment has demonstrated that predicted seepage rates through the liner of leachate / transport water from site will be very low. On entering groundwater this seepage will be diluted most likely by two orders of magnitude

• Based on this assessment it is considered that the proposed liner would be fit for purpose and the requirements of Paragraph 3 Sub-paragraph 4 of Schedule 2 of the Landfill Regulations 2002 should be downgraded accordingly

• Given the predicted low risk of the installation it is not considered that any active controls such as leachate or landfill gas management are warranted

It has also been demonstrated that the installation would comply fully with the Groundwater Regulations 1998 because:

• In general PFA contains no List I substances apart from minute concentrations of cadmium and mercury, however leachable concentrations are below the limits of detection and well below UK DWS

• In general PFA contains relatively low concentrations of a range of List II substances but their solubilities are for the most part very low and hence only very low concentrations would be expected to occur in seepage from the site

• The chemical composition of the main source term at the site (the transport water sluiced to the existing lagoons) has been monitored over an extended period and shown to contain no measurable List I substance and only very low concentrations of List II substances which are at or below UK DWS

• Based on groundwater monitoring carried out around the site there is no evidence for the discernible release to groundwater of any List I or List II substance from the existing ash lagoon facilities (Lagoons 3 and 4), or of any other relevant parameter including sulphate

• This is consistent with the numerical modelling work which indicates that even under worst case conditions there would be no discernible release of any List I or List substance to groundwater beneath the site

Proposals have been made for future monitoring of groundwater resources around the installation, which include levels and compositional monitoring for selected parameters. Control and trigger levels have been proposed for these parameters.

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Appendix A - HRA Drawings

Drawing Register

J24151C0/EIA/01 Site Location Plan J24151C0/EIA/02-A Application Site Boundary and Land Ownership Plan J24151C0/EIA/04-A Geological Setting J24151C0/EIA/05-A Groundwater Vulnerability Map J24151C0/EIA/05-B Location of Groundwater Source Protection Zones J24151C0/EIA/05-C Borehole and Monitoring Point Location Plan J24151C0/EIA/05-D Proposed Groundwater Monitoring Locations J24151C0/EIA/06 Location of Watercourses and Water Bodies J24151C0/EIA/06-A Groundwater Contour Plan - Upper Range Levels J24151C0/EIA/06-B Groundwater Contour Plan - Lower Range Levels

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Appendix B - Background Leachable Testing and Site Specific Certificates of Analysis

Batch Leaching Results

In 2004, all of the batch leaching data for PFA available in the JEP Member Companies was collated. The statistical analysis of the data in order to suggest ‘typical’ values was complicated by the empirical nature of the data. In particular, statistical analysis issues arose from: the ‘scatter’ in the reported data; many of the reported concentrations being below method detection limits; and, various detection limits being reported for the same element.

All of these factors are exemplified by cadmium where of the 67 data values from the one-step batch leaching test at L/S = 10 l/kg, 62 of the data points were below the detection limits available from the laboratories used (<1000 µg/l [1 No. value]; <100 µg/l [18 No.]; <50 µg/l [10 No. ]; <10 µg/l [3 No.]; <5 µg/l [5 No.]; <4 µg/l [12 No.]; <1 µg/l [6 No.]; <0.4 µg/l [7 No.]). Only five of the values were above detection: 2 of 10 µg/l and one each of 8 µg/l, 6 µg/l, and 1 µg/l.

Taking these factors into account, a median value was been calculated from the data values for each determinand by converting any values reported as less than a detection limit into a value equal to half of the detection limit and then taking the median of the resulting dataset.

In addition a range of values was derived for each determinand which is bounded by either:

• the 10th and 90th percentile values, where all the data are above method detection limits. • zero and the 90th percentile of the observed values, where some of the data are below a method detection limit.

Where all the reported data are below method detection limits, the highest detection limit reported was quoted as the concentration “range”.

The data obtained using this approach for results from 10:1 single-step batch leaching experiments, 2:1 single-step batch leaching experiments and two-step batch leaching experiments at L/S ratios of 2 and 8 l kg-1 are presented in the following tables:

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Concentration / (mg l-1) Determinand n Median Range Aluminium Al 44 5.3 0 - 16.2 + Ammonium NH4 11 1 0 – 7.8 Antimony Sb 47 0.025 0 – 0.20 Arsenic As 67 0.05 0 - 0.20 Barium Ba 40 0.15 0 – 0.45 Boron B 67 3.2 0 - 6.8 Bromide Br- 10 0.39 0 – 0.83 Cadmium Cd 67 0.005 0 – 0.01 Calcium Ca 49 210 110 – 490 Chloride Cl- 52 3 0 – 15 Chromium Cr 67 0.05 0 – 0.21 Cobalt Co 46 0.023 0 - 0.038 Copper Cu 65 0.025 <0.1 Cyanide CN- 32 0.025 <0.1 Fluoride F- 61 1.5 0 – 3.1 Iron Fe 43 0.025 0 – 0.33 Lead Pb 64 0.025 0 – 0.06 Magnesium Mg 49 0.24 0 – 12 Manganese Mn 45 0.005 0 – 0.43 Mercury Hg 65 <0.0005* 0 - 0.0002 Molybdenum Mo 61 0.8 0 - 1.5 Nickel Ni 67 0.025 0 – 0.16 - Nitrate NO3 34 0.5 0 – 4.6 - Nitrite NO2 29 0.05 0 – 0.07 3- Phosphate PO4 15 0.05 0 – 2.7 Potassium K 49 22 5.6 – 42 Selenium Se 67 0.05 0 – 0.26 Silicon Si 43 1 0 – 2.77 Sodium Na 46 29 0 – 64 2- Sulphate SO4 49 500 230 – 800 Sulphide S2- 12 0.025 <0.1 Tin Sn 44 0.038 0 – 0.13 Titanium Ti 45 0.025 0 – 0.08 Vanadium V 62 0.14 0 – 0.79 Zinc Zn 66 0.025 0 – 0.32 pH 58 11 9.7 - 11.7 Elect. Condy µS/cm 63 1300 800 – 1900

Table 1.1A Summary of data obtained from the batch leaching of PFA at an L/S ratio of 10 l kg-1 (n is the number of values reported for each determinand; * for this entry the median is greater than the maximum of the range because almost all of the data are below various method detection limits).

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Concentration / (mg l-1) Determinand n Median Range Aluminium Al 6 3.8 0 – 22 + Ammonium NH4 - - - Antimony Sb 6 0.025 0 – 0.14 Arsenic As 5 0.04 0 – 0.15 Barium Ba 6 0.08 0 – 0.24 Boron B 6 17 11 – 33 Bromide Br- 6 0.95 0.42 – 3.8 Cadmium Cd 6 0.025 <0.05 Calcium Ca 6 910 830 – 2900 Chloride Cl- 6 20 0 – 51 Chromium Cr 6 0.26 0.2 - 0.61 Cobalt Co 6 0.025 <0.05 Copper Cu 6 0.025 <0.05 Cyanide CN- - - - Fluoride F- 6 4.4 1.1 – 5.1 Iron Fe 6 0.025 <0.05 Lead Pb 6 0.025 <0.05 Magnesium Mg 6 0.2 0 – 22 Manganese Mn 5 0.025 <0.05 Mercury Hg 6 0.00005 <0.05 Molybdenum Mo 3 5.4 4.0 – 6.0 Nickel Ni 6 0.025 <0.05 - Nitrate NO3 2 3.2 2.5 – 3.8 - Nitrite NO2 - - - 3- Phosphate PO4 6 0.005 0 – 0.6 Potassium K 6 150 73 – 200 Selenium Se 6 0.05 0 – 0.10 Silicon Si 6 1.8 0 - 2.6 Sodium Na 6 290 61 – 370 2- Sulphate SO4 6 1700 1600 – 2300 Sulphide S2- - - - Tin Sn 5 0.025 0 – 0.11 Titanium Ti 6 0.025 0 - 0.1 Vanadium V 6 0.71 0.18 – 1.0 Zinc Zn 6 0.025 <0.05 pH 6 10.7 9.9 - 11.0 Elect. Condy µS/cm 6 3300 2700 – 4100

Table 1.1B Summary of data obtained from the batch leaching of PFA at an L/S ratio of 2 l kg-1 (n is the number of values reported for each determinand).

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First step at L/S = 2 l kg-1 Second step at L/S = 8 l kg-1 Determinand n Concentration / (mg l-1) Median Range Median Range Aluminium Al 14 14 0 – 32 11 2.7 – 22 + Ammonium NH4 6 1.1 0.34 – 25 0.12 0 – 2.1 Antimony Sb 14 0.025 0 - 0.15 0.025 0 - 0.04 Arsenic As 14 0.01 0 - 0.07 0.04 0 - 0.10 Barium Ba 14 0.13 0 - 0.24 0.17 0 - 0.54 Boron B 14 15 2.4 – 24 2.2 0.55 – 4.9 Bromide Br- 6 0.85 0.37 – 1.90 0.06 0 – 0.35 Cadmium Cd 8 0.025* 0 – 0.013 0.025* 0 – 0.001 Calcium Ca 14 750 630 – 2700 200 110 – 310 Chloride Cl- 14 25 0 – 85 2.7 0 – 5.0 Chromium Cr 14 0.26 0.19 - 0.63 0.08 0 - 0.18 Cobalt Co 12 0.013 0 – 0.002 0.013 0 – 0.0005 Copper Cu 14 <0.008* 0 – 0.008 <0.017* 0 – 0.015 Cyanide CN- 6 0.01 <0.02 0.01 <0.02 Fluoride F- 14 3.3 0 – 7.8 0.7 0 – 2.0 Iron Fe 12 0.025 0 – 0.21 0.025 0 – 0.03 Lead Pb 14 0.001 0 – 0.002 0.005 0 – 0.005 Magnesium Mg 14 1.1 0 – 54 0.07 0 – 2.5 Manganese Mn 8 <0.025* 0 – 0.0009 <0.025* 0 – 0.0004 Mercury Hg 14 0.00015 0 – 0.0009 0.0001 0 – 0.0009 Molybdenum Mo 14 4.4 1.3 – 6.5 0.51 0.22 – 0.80 Nickel Ni 8 <0.025* 0 – 0.006 <0.025* 0 – 0.002 - Nitrate NO3 10 0.09 0– 2.1 0.005 0 – 1.6 - Nitrite NO2 6 0.005 <0.01 0.005 <0.01 3- Phosphate PO4 6 0.008 0 – 1.3 0.008 0 – 0.02 Potassium K 14 110 21 – 180 11 1.9 – 18 Selenium Se 14 0.05 0 - 0.41 0.05 0 - 0.18 Silicon Si 14 0.49 0.17 - 2.39 1.8 0.5 – 3.4 Sodium Na 14 220 38 – 390 13 3.8 – 21 14 1500 – 2- Sulphate SO4 2100 2600 360 150 – 520 Sulphide S2- 6 0.005 <0.01 0.005 <0.01 Tin Sn 12 0.021 0 – 0.07 0.015 <0.05 Titanium Ti 12 0.025 0 - 0.04 0.004 0 - 0.005 Vanadium V 14 0.16 0.10 – 0.93 0.2 0.1 – 0.7 Zinc Zn 14 0.03 0 – 0.09 0.025 0 – 0.1 pH 12 10.4 9.6 - 11.3 11.1 10.4 - 11.7 12 2900 – Elect. Condy µS/cm 3400 4300 950 690 – 1300

Table 1.1C Summary of data obtained from the successive batch leaching of PFA at L/S ratios of 2 and 8 l kg-1 (n is the number of values reported for each determinand; * for this entry the median is greater than the maximum of the range because almost all of the data are below various method detection limits).

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Column Leaching Experiments

A considerable amount of data on the leaching behaviour of PFA has been derived from column percolation tests by the JEP Member Companies. The test data are available from two sources:

• A series of column experiments undertaken at the CEGB (1971/2) and latterly Powergen (between 1997 and 2003), using an in-house methodology. • Tests undertaken by RWE Npower in accordance with the standardised column test prEN 14405 (CEN 2003).

There are limitations with the data obtained from column percolation experiments:

• Due to the time and expense involved with running these experiments for a relatively low permeability material such as PFA, a limited number of PFA samples have been tested and thus the results may not be fully representative of the range of leachate composition associated with PFA. • Despite careful packing of the columns, the hydraulic properties of samples may differ from real deposits of PFA in the field. • Other experimental conditions may also vary from field situations, e.g. degree of saturation of the sample, ambient temperature, pH of infiltrating water. • An important aspect to note is that, due to the relatively low permeability of PFA, column percolation experiments are time consuming and expensive to run.

CEGB and Powergen Experiments

The experiments involved placement of PFA samples from various UK power station sites into glass or perspex columns; pH-adjusted, demineralised water was then percolated through the samples, with eluates collected and analysed at regular intervals.

Since time intervals during the experiments were dependent on experimental factors such as percolation rate and sample dimensions, the concept of bed volume (BV) was introduced in the Powergen experiments to allow correlation of analytical results between experiments and with field situations. A unit of BV is essentially the volume of water contained within the test sample when fully saturated and was calculated after weighing the column with both fully saturated and dried ash prior to commencement of the experiment. Analytical results were recorded from samples collected at periodic intervals, related to the number of BV that had passed through the column.

The results of the CEGB/Powergen column experiments are summarised in Table 1.1D below. Note that median values have been calculated based on analytical results below detection limits assumed as being equal to a concentration of half the detection limit. For List II substances under the Groundwater Regulations 1998 this is considered appropriate; however for the List I substances mercury and cadmium, the resulting median calculation would be inappropriate since analytical detection limits have not been of the required precision to report the Environment Agency Minimum Reporting Values (MRV) for clean groundwater (Appendix 7, LFTGN01).

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Determinant S.V. Column Data Column Data Column Data Column Data 0 – 1 BV 1 – 5 BV 5 – 10 BV 10 + BV Media Max Media Max Media Max Media Max n n n n Aluminium 0.2 1.6 12 0.67 10 0.91 11 4.8 12 Ammonium 0.5 2.9 95 0.45 2.9 0.050 0.30 0.050 0.050 Antimony 0.005 0.001 0.12 0.0010 0.048 0.0033 0.011 0.0048 0.022 Arsenic 0.01 0.087 0.17 0.011 0.13 0.001 0.13 0.017 0.4 Barium 1.0 0.18 63 0.24 33 0.18 9.9 0.11 1.9 Beryllium3 0.015 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 Boron 1.0 0.76 120 0.50 25 0.63 8.5 1.0 3.3 Cadmium 0.005

Table 1.1D Summary of CEGB/Powergen Column Data

Notes: All values shown in mg/l and quoted to 2 significant figures; N/A, not available; S.V. Screening Value; UK drinking water standards (2001 or 1989) except: 1 World Health Organisation drinking water standard; 2 Inland waters EQS (IPPC Guidance Note H1), 3 Dutch national intervention value; BV, Bed volume;

The column data presented above is arbitrarily divided into 4 phases based on BV, to illustrate potential changes in leachate composition with time. In comparison to batch leach data, a similar list of determinants exceed screening values (SV) for median and/or maximum concentrations. Median concentrations are broadly comparable with those from the batch leach data; the main exception is boron, which shows a much higher median concentration in the batch leach dataset.

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Maximum concentrations detected in the column experiments may be significantly higher for some determinants in comparison to batch leaching tests, e.g. molybdenum and sulphate. These differences in maximum values may at least partly be explained by the brief time ‘interval’ that individual analyses represent; by way of contrast, the L/S 10:1 batch leach test data could be regarded as equivalent to an average over the first 10 to 15 BV (depending on the PFA sample density) of a column experiment. An important aspect of the column experiments is their measure of leaching trends over time. Results shown in the 10 + BV interval could be regarded as measurements beyond L/S 10:1 batch tests.

Only 4 determinants show median values still exceeding SV after 10 BV – aluminium, arsenic, selenium and pH. The alkaline nature of pH over the course of the column experiments is a particularly important point, since concerns have been raised that PFA deposits could generate, over prolonged timescales, acidic leachate with increased concentrations of dissolved inorganic substances.

The pH trend graph depicted below from the 2003 Powergen experiments provides a clear example of the stable, alkaline nature of leachate over time:

2003 Power Technology Ash Column Experiments pH Trends

13

12.5

12

11.5

11 pH A pH B 10.5 pH pH C pH D 10

9.5

9

8.5

8 0 5 10 15 20 25 30 35 Cumulative BV

A Powergen experiment undertaken in 2000 involved the same sample of ash, derived from Ratcliffe Power Station, being divided between 3 columns which were leached with pH-adjusted water of 4.2, 5.5 and 7.0 respectively. This experiment found that even after 40 BV at pH 4.2 and 75 BV at pH 5.5 had passed through the columns, the eluates remained alkaline with a pH of approximately 10, as shown in the summary graphs below:

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Note that in the 2000 experiments on Ratcliffe PFA, all analytical results were below detection limits for cadmium (0.1µg/l) and mercury (0.01µg/l).

RWE Npower Percolation Tests

A series of upflow percolation tests were undertaken during 2000 and 2002 on samples of PFA from 4 sources: Aberthaw, High Marnham, Didcot ‘A’ and Ratcliffe. Data below is presented for pH, List I substances (cadmium and mercury) and selected List II substances (selenium, arsenic and boron).

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pH Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power pH Station Didcot A 9.3 10.5 10.4 10.3 10.7 11.2 10.3 Ratcliffe 11.3 11.6 11.4 11.8 11.4 11.7 11.5 Aberthaw 9.2 9.2 9.4 9.1 9.2 9.7 9.7 High Marnham 10.6 10.6 10.8 10.5 10.2 10.4 10.1

List I Substances - Cadmium Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power Concentration (µg/l) Station Didcot A <5 <5 <5 1.6 <0.5 <0.5 <0.5 Ratcliffe 5.2 <50 4 0.9 <0.5 <0.5 <0.5 Aberthaw 0.3 0.3 0.1 0.1 <0.1 <0.1 <0.1 High Marnham 1.2 0.5 0.4 0.2 <0.1 <0.1 <0.1 Notes: Concentrations in italics exceed the MRV (LFTGN01) of 0.1µg/l Concentrations underlined exceed the UK DWS of 5.0µg/l

List I Substances - Mercury Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power Concentration (µg/l) Station Didcot A 0.25 0.082 0.033 0.014 <0.005 0.015 <0.005 Ratcliffe <0.005 0.17 <0.005 <0.005 <0.005 <0.005 <0.005 Aberthaw 1 0.9 1.1 0.8 0.5 0.2 <0.1 High Marnham 2.5 2.1 2.6 0.9 0.4 0.1 0.1 Notes: Concentrations in italics exceed the MRV (LFTGN01) of 0.01µg/l Concentrations underlined exceed the UK DWS of 1.0µg/l

The data for mercury and cadmium presented above shows that after an initial ‘flushing’ of these substances (L/S ratio <1), concentrations stabilise either below detection limits or at concentrations marginally above the MRV but below the UK DWS.

List II Substances - Selenium Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power Concentration (mg/l) Station Didcot A 1.1 0.6 0.33 0.19 0.057 0.028 0.046 Ratcliffe 0.22 0.09 0.041 0.01 0.003 0.006 0.03 Aberthaw 0.076 0.068 0.083 0.048 0.025 0.018 0.027 High Marnham 0.096 0.114 0.114 0.043 0.02 0.026 0.026 Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Notes: Concentrations in italics exceed the UK DWS of 0.01mg/l

List II Substances - Arsenic Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power Concentration (mg/l) Station Didcot A 0.072 0.07 0.0331 0.0288 0.0105 0.0054 0.0142 Ratcliffe 0.0179 0.0125 0.0029 0.0011 0.0012 0.0069 0.0216 Aberthaw 0.022 0.02 0.018 0.017 0.018 0.018 0.012 High Marnham 0.183 0.068 0.125 0.042 0.049 0.072 0.073 Notes: Concentrations in italics exceed the UK DWS of 0.01mg/l

List II Substances - Boron Fraction 1 2 3 4 5 6 7 L/S ratio 0.1 0.2 0.5 1 2 5 10 Power Concentration (mg/l) Station Didcot A 10.6 3.95 1.3 1.7 2 Ratcliffe 0.445 0.12 0.17 1.8 1.29 Aberthaw 4.4 4.3 4.8 4.8 3 0.98 0.46 High 2.5 2.7 2.5 2 0.69 1.08 1.07 Marnham Notes: Concentrations in italics exceed the UK DWS of 1.0mg/l

The data presented above for selenium, arsenic and boron clearly demonstrate that PFA has the potential to leach these List II substances at concentrations above DWS. However the data also demonstrates that leachable concentrations decrease with time and therefore could be regarded as declining source terms in a groundwater risk assessment.

Conclusions from Percolation Tests

• Column experiments performed over a number of years have provided valuable data on the potential long term leaching trends that may occur within UK PFA deposits. • Data obtained from in-house column experiments (CEGB/Powergen) and from prEN 14405 (CEN 2003) appear broadly consistent and also in accordance with results from standard batch leaching tests. • All the column experiments yielded alkaline eluates for their entire duration, which have extended as far as 75 bed volume (BV) equivalents and also been conducted with water of pH adjusted as low as 4.2. The alkaline nature of the leachate is again in agreement with historic results from batch leaching tests. • The data collectively indicates that PFA can be regarded as a declining source term in the context of groundwater risk assessments, with concentrations of determinants in leachate decreasing with time after some initial ‘flushing’ at L/S ratios equivalent to 1 or under. • Cadmium and mercury stabilise beyond L/S ratio of 1, at concentrations either below or slightly above analytical detection limits. These concentrations are at or marginally above minimum reporting values (MRV) for clean groundwater and therefore minimal attenuative capacity would be required by any geological barrier Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

to achieve compliance for these List I substances under the Groundwater Regulations (1998). • Several List II substances can be leached at concentrations above UK drinking water standards (DWS) after L/S ratios of 10 and beyond, although the declining nature of concentrations is still evident. Compliance with the regulations for these substances could be achieved with a combination of attenuation in the geological barrier and dilution in any receiving groundwater. • The median and maximum concentration data calculated for the Powergen column experiments could be used as a source term in quantitative groundwater risk assessments for List II substances. Care should be taken however in using statistical data for the List I substances mercury and cadmium, since analytical detection limits may not be of sufficient precision to allow assessment against MRV.

pH-dependent Leaching Experiments

A number of PFA samples have been subjected to the pH-dependent batch leaching test given in prEN 14429.

Comments on the practicalities of the upflow column percolation test method and the pH-dependent test method:

• Both tests take a long time to complete using PFA – the column test typically takes 15 working days and the pH-dependent test 10 working days. • The eluates from both tests require significant dilution before analysis using multi- element techniques. This increases the error in the reported concentrations and reduces the accuracy of the values reported for trace components.

The results of these tests are summarised in Tables 1.1E – 1.1J below.

Analysis of the data from the samples shows that the concentrations of List I and List II substances show varying patterns with the changing pH. In the case of cadmium, concentrations in the alkaline eluates were typically at or below the analytical detection limits, but concentrations rose in eluates on the acidic side of neutral. Mercury concentrations showed a less obvious pattern with pH, although many eluates contained concentrations below the analytical detection limit. Of the List II elements of particular interest for PFA, concentrations of boron typically decreased with increasing eluate pH, whist concentrations of molybdenum and selenium typically increased with increasing eluate pH.

Eluate pH after 48 hours Analyte 11.5 9.5 9.3 8.4 6.4 5.8 4.0 3.8 Concentration / (µg l-1) Sodium 26000 22000 22500 22500 25000 25000 28000 28000 Ammonium <5000 <10000 <12500 <12500 <12500 <12500 <20000 <20000 Potassium <5000 46000 40000 47500 52500 50000 56000 60000 Calcium 297000 574000745000 815000 980000 975000 10800001136000 Magnesium 35000 14000 100000 152500 202500 205000 224000 236000 Chloride <5000 <10000<12500 <12500 <12500 <12500 <20000<20000 Sulphate 657000 760000 890000 907500 920000 872500 864000 904000

Table 1.1E Major ion concentrations of pH-dependent test eluates from Didcot ‘A’ ash as determined by ion chromatography. Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Eluate pH after 48 hours Analyte 11.9 10.7 9.9 9.1 7.6 7.1 5.4 4.1 Concentration / (µg l-1) Sodium 29000 36000 26000 25000 27500 22500 20000 24000 Ammonium <5000 <10000 <10000 <12500 <12500 <12500 <20000 <20000 Potassium 18000 26000 24000 25000 27500 47500 14000 32000 Calcium 279000 564000 668000 815000 852500 937500 956000 1104000 Magnesium <5000 <10000 24000 127500 157500 172500 192000 232000 Chloride <5000 <10000<10000 <12500 <12500 <12500 <20000<20000 Sulphate 442000 608000 674000 697500 680000 680000 696000 696000

Table 1.1F Major ion concentrations of pH-dependent test eluates from Ratcliffe- on-Soar ash as determined by ion chromatography.

Eluate pH after 48 hours Analyte 11.5 9.5 9.3 8.4 6.4 5.8 4.0 3.8 Concentration / (µg l-1) Aluminium 13400 210 300 70 <50 560 51700 115000 Antimony 6.8 38 48 53 50 38 21 23 Arsenic 42.9 26.4 250 552 280 124 194 312 Barium 485 341 121 122 125 150 178 180 Boron 5700 11800 14600 15500 17000 17100 17300 18100 Cadmium <5 <5 <5 <5 28 61 77 83 Calcium 352000 637000836000 955000 1039000 1110000 11450001175000 Chromium 433 225 36.2 14.8 <6 <6 232 497 Cobalt <2 <2 <2 12 160 200 220 250 Copper <40 <40 <40 <40 <40 <40 431 542 Iron <100 <100 <100 <100 <100 <100 <100 <100 Lead <10 <10 <10 <10 <10 <10 <10 <10 Magnesium <600 15300 106000162000 194000 215000 242000288000 Manganese <10 <10 20 427 3890 4540 3390 3390 Mercury 0.083 <0.005<0.005 <0.005 <0.005 <0.005 <0.005<0.005 Molybdenum 1180 1170 1310 1160 780 240 <5 <5 Nickel <20 <20 <20 95 524 631 417 400 Potassium 45100 47500 45200 45300 52700 52100 56100 58700 Selenium 380 340 280 240 160 110 72 76 Silica 900 1300 7800 21000 120000150000 280000390000 Sodium 27300 25600 26300 27000 26100 28900 30200 28600 Tin 6 6 6 7 6 6 7 9 Titanium 5 9 110 12 17 16 20 23 Vanadium 160 320 950 1190 1030 670 470 620 Zinc <60 <60 <60 <60 648 2320 3340 3910

Table 1.1G Composition of pH-dependent test eluates from Didcot ‘A’ ash as determined by inductively-coupled plasma (ICP) spectroscopy, cold vapour with fluorescence detection (for mercury) or colorimetry (for boron).

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Eluate pH after 48 hours Analyte 11.9 10.7 9.9 9.1 7.6 7.1 5.4 4.1 Concentration / (µg l-1) Aluminium 672 780 930 140 <50 <50 2230 101000 Antimony <4 56 90 86 80 72 41 14 Arsenic 77 52 284 447 288 245 17.6 24.5 Barium 749 436 226 87 103 106 149 182 Boron 2800 7900 8900 9900 10300 10700 11200 11800 Cadmium <5 <5 <5 <5 <5 <5 37 44 Calcium 293000 636000772000 883000 932000 1022000 10400001266000 Chromium 198 81.5 23.7 7.7 <6 <6 <6 131 Cobalt <2 <2 <2 4 50 68 130 170 Copper <40 <40 <40 <40 <40 <40 242 937 Iron <100 <100 <100 <100 <100 <100 <100 180 Lead <10 <10 <10 <10 <10 <10 <10 29 Magnesium <600 <600 27300 131000166000 182000 189000232000 Manganese <10 <10 <10 125 3130 3770 4630 5360 Mercury <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 0.19 Molybdenum 1210 1300 125 940 880 850 33 <5 Nickel <20 <20 <20 44 280 343 440 345 Potassium 25100 26600 22700 25000 23900 25200 24500 28300 Selenium 210 370 300 200 100 100 42 30 Silica 9600 2300 4700 14800 41000 47000 100000 280000 Sodium 27000 30600 32100 30000 31800 30200 32600 35100 Tin 6 6 8 6 7 6 7 6 Titanium 4 7 10 11 8 12 17 19 Vanadium 150 540 780 880 460 500 140 22 Zinc <60 <60 <60 <60 <60 <60 2120 2890

Table 1.1H Composition of pH-dependent test eluates from Ratcliffe-on-Soar ash as determined by inductively-coupled plasma (ICP) spectroscopy, cold vapour with fluorescence detection (for mercury) or colorimetry (for boron).

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Eluate pH after 48 hours Analyte 3.7 6.5 7.3 7.8 8.5 9.9 10.9 12.0 Concentration / (mg l-1) Aluminium 10.8 0.16 0.09 0.09 0.44 3.96 6.54 11.1 Antimony 0.004 0.014 0.015 0.013 0.012 0.011 0.007 0.008 Arsenic 0.146 0.25 0.242 0.164 0.066 0.016 0.023 0.028 Barium 0.18 0.01 0.01 0.03 0.1 0.17 0.21 0.3 Boron 2.1 2 1.77 1.51 1.08 0.76 0.77 0.13 Cadmium 0.0023 0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 Calcium 454 363 283 226 172 129 95.8 25.3 Chromium 0.092 0.011 0.019 0.04 0.043 0.033 0.033 0.04 Cobalt 0.01 0.016 0.002 <0.001 <0.001 <0.001 <0.001 <0.001 Copper 0.009 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Iron 0.05 0.02 0.01 0.01 0.01 0.01 <0.01 0.01 Lead <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Magnesium 81.1 65.1 52.3 40 22.5 2.99 0.12 <0.03 Manganese 0.172 0.272 0.054 0.017 0.002 0.002 <0.001 <0.001 Mercury 0.0002 0.0003 0.0005 0.0005 0.0003 <0.0001 <0.0001<0.0001 Molybdenum 0.005 0.283 0.345 0.339 0.327 0.289 0.267 0.279 Nickel 0.032 0.048 0.012 0.003 <0.001 <0.001 <0.001 <0.001 Potassium 5.79 4.64 4.47 4.15 3.62 3.03 3.74 5.16 Selenium 0.046 0.091 0.106 0.11 0.133 0.088 0.108 0.116 Silica 36 18 8 6.4 1.2 0.3 2.1 4.5 Tin 17.4 16.2 16.6 16.7 16 22.6 110 708 Titanium <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Vanadium <0.02 <0.02 <0.02 0.02 <0.02 <0.02 <0.02 <0.02 Zinc 0.191 0.622 0.602 0.435 0.216 0.121 0.138 0.203

Table 1.1I Composition of pH-dependent test eluates from Aberthaw PFA as determined by inductively-coupled plasma (ICP) spectroscopy.

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Eluate pH after 48 hours Analyte 4.4 8.9 9.8 10.1 10.4 11.1 11.8 Concentration / (mg l-1) Aluminium 13.1 0.92 4.93 8.99 12.7 9.25 3.04 Antimony 0.021 0.06 0.044 0.037 0.031 0.008 0.006 Arsenic 0.002 0.114 0.1 0.098 0.097 0.01 0.14 Barium 0.07 0.02 0.08 0.12 0.12 0.12 0.13 Boron 5.40 4.60 4.30 4.00 4.00 2.90 0.44 Cadmium 0.0066 0.0012 0.0001 0.0001 0.0005 <0.0001 <0.0001 Calcium 714 564 467 407 408 290 64.5 Chromium 0.013 0.01 0.028 0.043 0.048 0.074 0.126 Cobalt 0.013 0.004 0.001 0.001 <0.001 <0.001 <0.001 Copper 0.182 0.027 0.001 0.008 0.007 0.008 0.007 Iron 0.3 0.13 0.01 <0.01 0.01 <0.01 <0.01 Lead 0.003 0.002 0.001 <0.001 <0.001 <0.001 <0.001 Magnesium 85.1 51.5 13 1.92 0.33 <0.03 <0.03 Manganese 0.317 0.055 0.001 0.002 0.003 0.003 0.003 Mercury 0.0009 0.0002 0.0002 0.0002 0.0002 <0.0001 <0.0001 Molybdenum 0.008 1.26 1.53 1.59 1.62 1.46 1.52 Nickel 0.060 0.019 0.005 0.004 0.004 0.003 0.002 Potassium 36.9 33.5 32.6 33.2 33.5 34.4 36.6 Selenium 0.001 0.028 0.062 0.073 0.083 0.076 0.057 Silica 36.1 2 0.1 <0.1 <0.1 0.3 3.6 Tin 68.2 49.4 49.4 49.3 49.3 109 473 Titanium <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Vanadium 0.05 0.03 0.02 0.02 0.02 0.02 0.02 Zinc 0.077 0.234 0.206 0.197 0.212 0.123 0.358

Table 1.1J Composition of pH-dependent test eluates from High Marnham PFA as determined by inductively-coupled plasma (ICP) spectroscopy.

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Appendix C - Historical Plans

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Appendix D - Borehole Logs

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Appendix E - Pumping Tests

B Station Borrow Pit – Aquifer Assessment

1.0 Aims

The primary aim of the pump test was to provide a direct measurement of the hydraulic properties of the terrace gravels in the vicinity of the Borrow Pit. Depending upon the hydraulic characteristics of the gravels a secondary aim of the test was to provide information regarding the degree of hydraulic connection between the gravels, the River Trent and the Borrow Pit.

2.0 Pump Test Programme & Contractor’s Factual Report

The hydrogeological testing programme undertaken at Rugeley Power Station as follows:

1. Step Drawdown Test, 10th June 05 2. Constant Rate Test, 11th to 13th June 05 3. Recovery Monitoring, 13th to 14th June 05

The analysis and interpretation of these test data are presented in the following sections. A complete record of the test data are presented within the Contractors factual report which is enclosed.

3.0 Step Test

The pumped well, borehole A, was pumped at five steps each of 100 minutes duration. The flow rates for each step were 3.8 l/s, 8.1 l/s, 12.4 l/s, 16 l/s and 22 l/s. The water level in borehole A was measured continuously throughout the test and for a period of 100 minutes after cessation of pumping.

The objective of the step drawdown test was to determine the broad hydraulic performance of the pumping well to determine the appropriate flow rate for the Constant Rate Test (CRT) and also to determine the Well Efficiency (%) at various pumping rates.

The Bierschenk & Wilson method was used to analyse the step test data, the results of which are presented in Table 1 below.

Table 1 Step Test Analysis Results

Flow Rate Water Level Well Efficiency Step (l/s) (mbd) (%) 1 3.8 3.13 72 2 8.7 3.98 53 3 12.4 4.99 44 4 16 6.37 38 5 22 9.2 31

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The results indicate the following;

1. The pumping rate of 22 l/s was the appropriate pumping rate for the CRT giving the maximum potential drawdown in the observation wells without excessive drawdown in the well itself.

2. The efficiency of the well, which is a function of friction losses as groundwater enters the well through the well screen, is generally poor and decreases with increasing flow rate. The effect of the low efficiency is that, at the rate used in the constant rate test, the observed drawdown in water level in the well is likely to be approximately three times greater than the groundwater level in the immediate vicinity of the borehole. The pumped well data have therefore not been used in the analysis of the test, which is not an issue given the number of observation wells used.

4.0 Constant Rate Test and Recovery

The pumped well, borehole A, was pumped at a rate of approx 22 l/s for a period of 48 hours, followed by a period of 24 hours of monitoring the recovery in groundwater levels following cessation of pumping. Groundwater level was monitored continuously within the pumped well, and the following observation boreholes; B, C, D, E, F, G, 103 and 106.

Both the data from the pumping phase and recovery phase can be analysed to give an estimate of hydraulic conductivity and storativity (% of water released from storage with reduction in head).

It should be noted that the numerical methods used to analyse pump test data actually provide an estimate of the transmissivity of an aquifer unit, which is the product of the aquifer thickness and the hydraulic conductivity. As a conservative assumption, the thickness of the gravels has been taken as 20m despite their base not being proved in the pumped well at 26m depth. This means that the estimates of hydraulic conductivity provided here are conservatively high since a greater thickness of aquifer would yield a lower hydraulic conductivity.

A summary of the test data is presented in Table 2.

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Table 2 Summary of Constant Rate Pump Test Data

Distance from Datum Rest Water Level, Pumped Water Location Easting Northing pumped well, m Elevation mbd Level, mbd BH103 407096.00 316748.17 222.77 66.01 1.87 1.97 BH106 407015.01 316919.99 153.39 66.62 2.04 2.23 BHA 407162.91 316960.65 0.00 66.62 2.68 10.26 BHB 407169.05 316967.92 9.52 66.15 2.29 3.145 BHC 407169.52 316952.81 10.25 66.32 2.435 3.28 BHD 407204.24 317019.83 72.18 64.68 1.17 1.465 BHE 407142.66 316981.65 29.17 66.16 2.25 2.92 BHF 407142.46 316939.31 29.56 66.06 2.06 2.65 BHG 407091.17 316888.64 101.65 65.60 1.43 1.71 R2 407156.85 317055.60 95.14 64.74 1.3 1.32 R1 407245.22 317015.71 99.03 64.05 0.86 0.85

The method used to analyse the data from the pumping phase was the Cooper-Jacob (1946) method, which is briefly outlined below.

The drawdown versus time data is plotted on a semi-logarithmic plot, and a best-fit straight line is drawn through the mid to late time data. The hydraulic conductivity and storativity of the strata are determined from the gradient and x-axis intercept of the best- fit line.

For the recovery phase of the test, the Theis Recovery (1935) method was adopted, which is briefly outlined below.

The residual drawdown is plotted against a time function on a semi-logarithmic plot, and a best-fit straight line is drawn through the data. The hydraulic conductivity of the strata is determined from the gradient of the best-fit line.

The results of these analyses are summarised in Tables 3 and Table 4, respectively.

Table 3 Constant Rate Test Analysis Results

Borehole Hydraulic Parameters Comments on analysis Hydraulic conductivity Storativity (m/s) B 9E-04 9E-03 Good fit to test data C 1E-03 4E-03 Good fit to test data D 2E-03 5E-03 Good fit to test data E 9E-04 6E-03 Good fit to test data F 1E-03 1E-02 Good fit to test data G 2E-03 7E-03 Good fit to test data 103 2E-03 9E-03 Poor fit to test data 106 2E-03 5E-03 Poor fit to test data 106 (P) 2E-03 5E-03 Poor fit to test data Mean 2E-03 7E-03

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Table 4 Recovery Monitoring Analysis Results

Borehole Hydraulic conductivity Comments on analysis (m/s) B 7E-04 Reasonable fit to test data C 4E-04 Reasonable fit to test data D 1E-03 Reasonable fit to test data E 8E-04 Reasonable fit to test data F 8E-04 Poor fit to test data G 1E-03 Good fit to test data 103 3E-03 Poor fit to test data 106 2E-03 Reasonable fit to test data 106 (P) 8E-04 Poor fit to test data Mean 1E-03

Drawdowns observed in Boreholes 103 and 106 are understandably small due to the large distance from the well and because of this the data are harder to analyse. Considerably more confidence can therefore be attached to the closer observation wells.

The geometric mean of the CRT analyses for the six closest observation wells (B, C, D, E, F and G) is 1.2E-3 m/s. The geometric mean for the six Recovery analyses with reasonable or good data fits is 9E-4 m/s, (including BH106 for which a reasonable fit to the data was obtained but excluding well F for which only a poor fit was obtained).

The values of storativity derived from the nine observation wells vary between 4E-3 and 1E-2 with an arithmetic mean of 7E-3. This implies that the aquifer is acting in a semi- confined manner and is not acting as a simple water table. This is likely to reflect the impact of the lower permeability soil layer present across the site.

5.0 Discussion of Pump Test Results

In order to gain a better understanding of the test results the pumped water level data were contoured using the Surfer software package. The pumped water levels are shown in Figure 1 (overleaf).

The cone of drawdown centred on the pumped well is asymmetric, with steeper groundwater gradients observed to the north east, towards the River Trent. A profile of the observed groundwater levels is presented in Figure 2.

The test data from the borehole closest to the River Trent, borehole D, are presented in Figure 3. From these data it can be seen that water levels reach a steady state condition after approximately 30 hours of pumping, whereas water levels in all the other boreholes are still dropping (for example borehole E in Figure 3). The steady state water level in borehole D corresponds to the water level recorded at the closest point in the River Trent during the test, a level of 63.2 mOD.

From the asymmetry of the groundwater levels and the observed drawdown in borehole D it is apparent that the River Trent is contributing water to the groundwater system under pumping conditions.

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Figure 1 Contour plot of Pumped Water Levels, mOD

317050

BHD

317000 BHE BHB BHA BHC 316950 BHF

BH106

316900 BHG

316850

316800 Pumped water levels at 0.5m intervals

0 50 BH103 316750 m 407050.00 407100.00 407150.00 407200.00

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Figure 2 Profile of pumped groundwater level

Pumped Groundwater Level

66

64

62

60

Elevation (mOD) 58

56 0 50 100 150 200 Distance (metres)

A B F G D

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Figure 3 Water Level Data, Observation Wells D and E

Rugeley Power Station: Observation Borehole E

0.00

0.10

0.20

0.30

0.40

0.50 Drawdown (m) 0.60

0.70

0.80 11 June 2005 12 June 2005 13 June 2005 14 June 2005 15 June 2005

Date

Rugeley Power Station: Observation Borehole D

0.00

0.05

0.10

0.15

0.20

Drawdown (m) Drawdown 0.25

0.30

0.35 11 June 2005 12 June 2005 13 June 2005 14 June 2005 15 June 2005

Date

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6.0 Sensitivity Analysis

In order to test the sensitivity of the hydraulic conductivity values derived from the analytical results, a preliminary numerical groundwater flow model was constructed. This groundwater flow model was constructed using the WinFlow software package.

Initially a steady state model was constructed using the following input parameters;

Aquifer top = 67mOD, Aquifer bottom = 47mOD, porosity = 0.1, Hydraulic conductivity, K = 1E-03 m/s, Storativity, S = 0.01, Hydraulic Gradient, i = 0.0027, Reference head = 63.95 mOD

The River Trent was modelled as a constant head boundary.

The results of the modelling are presented in Table 5.

Table 5 WinFlow Results, Non Pumping Condition

Observed Borehole Predicted (mOD) Residual (m) (mOD) G 64.17 64.189 -0.019 E 63.91 63.9228 -0.013 F 64 63.9821 0.018 C 63.89 63.8871 0.0029 B 63.87 63.8668 0.0032 D 63.51 63.69 -0.18 106 64.58 64.3569 0.22 103 64.14 64.3585 -0.22

The basic calibration undertaken focused on obtaining a good fit for observation wells closest to the pumped well (B, C, E, F and G). The model predicted that the River Trent was being fed by groundwater adjacent to the pumping well. The total flux of groundwater into the river was predicted to be 3.5 l/s.

The results of the modelling under non-pumping conditions are a reasonable fit with the predicted groundwater levels being close to the observed data. However, using this type of model it is possible to achieve reasonable calibration with a wide range of hydraulic conductivity values.

The pumping model was set up with the same aquifer parameters as the non-pumping model.

The initial results indicated that the predicted groundwater levels were all higher than those observed, with levels typically between 0.2m and 0.4m too high. The sensitivity of the model fit to the hydraulic conductivity was therefore assessed by varying the hydraulic conductivity over a range of values. The results of this analysis are presented in Table 6 which shows the residual groundwater difference between the observed and modelled heads at each observation well. Clearly the smaller the residual, the closer the fit of the model.

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Table 6 Sensitivity Analysis, Pumping Condition

Hydraulic Residual Groundwater Level Difference (m) Conductivity Sum Residual D B E C F G (m/s) for all six wells 2E-03 -0.42 -0.57 -0.51 -0.55 -0.38 -0.23 -2.66 1E-03 -0.37 -0.28 -0.34 -0.25 -0.2 -0.16 -1.6 8E-04 -0.34 -0.14 -0.26 -0.11 -0.11 -0.13 -1.09 6E-04 -0.31 0.11 -0.11 0.15 0.05 -0.07 -0.18 4E-04 -0.22 0.61 0.18 0.67 0.36 0.03 1.63 2E-04 0.02 2.25 1.09 2.36 1.36 0.38 7.46

It is apparent from Table 6 that the preliminary modelling is indicating a “best fit” hydraulic conductivity of 6E-04 m/s.

7.0 Conclusions

The pump test data have been analysed using three different methodologies:

1. Analysis of the Constant Rate Test data using the Cooper-Jacob (1946) method; 2. Analysis of the Recovery Monitoring data using the Theis Recovery (1935) method; and 3. Sensitivity analysis by construction of a preliminary numerical groundwater flow model using the WinFlow software package.

The results of these analyses have indicated a hydraulic conductivity for the gravels of between 6E-4 m/s and 1.2E-3m/s.

In addition the shape of the drawdown cone and responses to pumping in the borehole closest to the river have indicated that there is hydraulic connection between the river and the gravels. The river is therefore likely to act as a significant recharge boundary to the aquifer if water levels are lowered during dewatering.

Based on our earlier study (Engineering Feasibility Study, dated October 2004) it would therefore appear that it will be possible to dewater the Borrow Pit sufficiently to allow installation of a basal liner by direct pumping followed by sump pumping, without the need for hydraulic cutoffs. However, given the relatively high conductivities and the hydraulic connection that has been confirmed between the aquifer and the river, it is advised that the feasibility of this be confirmed through development of a more detailed numerical groundwater model for the site.

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Appendix F - Groundwater Level Data and Hydrographs

Rugeley Groundwater Levels (m OD)

BH101 BH102S BH102D BH103 BH106S BH106D May-06 65.13 63.23 65.35 Jun-06 65.00 64.75 64.75 65.33 65.33 Jul-06 64.96 64.64 64.64 64.06 65.36 65.33 Aug-06 65.02 64.77 64.77 63.47 64.97 65.41 Sep-06 65.06 64.79 64.79 64.10 65.26 65.25 Oct-06 65.14 64.88 64.88 64.26 65.41 65.41

BH107 BH108S Bh108D BH109 BH110 BH111A May-06 64.01 64.30 64.26 64.86 65.29 65.14 Jun-06 64.36 63.96 63.97 64.89 65.14 64.94 Jul-06 64.40 63.92 63.92 64.74 65.11 64.95 Aug-06 64.50 64.06 64.06 65.07 65.20 65.18 Sep-06 64.46 64.17 64.12 65.14 65.28 65.12 Oct-06 64.63 64.33 64.32 65.23 65.39 65.19

BH112 BH124 BH125 BH126 BH127 May-06 65.30 Jun-06 65.09 64.93 64.90 Jul-06 65.11 65.14 65.02 64.62 64.65 Aug-06 65.32 65.21 65.08 64.60 64.73 Sep-06 65.28 65.14 65.14 64.62 64.76 Oct-06 65.36 65.34 65.21 64.72 64.82

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Rugeley : Groundwater Hydrographs

66.0

BH101 65.5 BH102S BH102D BH103

65.0 BH106S BH106D BH107 BH108S

evation (m OD) 64.5 Bh108D BH109 BH110 BH111A 64.0 BH112 groundwater el groundwater BH124 BH125 BH126 63.5 BH127

63.0 May-06 Jun-06 Jul-06 Aug-06 Sep-06 Oct-06 date

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Appendix G - Baseline Groundwater Quality

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Appendix H - Quantitative Risk Assessment

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Rugeley Borrow Pit: Source concentrations (mg/l)

Lagoon 4 Date As As B Cd Cd Pb Pb Mo Mo K SO4 V V Position 7 4 9-Nov-92 <.04 0.04 0.7 <.01 0.001 <.03 0.03 0.02 0.02 19.0 195 0.03 0.03 ASH LAGOON WEIR 10-Feb-93 <.04 0.04 0.9 0.01 0.01 0.06 0.06 <.05 0.05 13.0 120 <.05 0.05 Location ref :- 7-Jul-93 <.04 0.04 0.72 <.01 0.001 0.03 0.03 <.02 0.02 20.0 <.02 0.02 SK 0711 1705 15-Feb-94 <.04 0.04 0.22 <.01 0.001 <.03 0.03 0.02 0.02 16.0 106 <.03 0.03 13-Feb-95 <.04 0.04 0.4 <.01 0.001 <.03 0.03 <.02 0.02 15.0 283 <.03 0.03 15-Jan-96 <.03 0.03 1.08 <.01 0.001 <.03 0.03 0.02 0.02 20.0 398 <.03 0.03 22-Jul-96 470 3-Feb-97 0.05 0.05 0.7 <.01 0.001 <.03 0.03 0.14 0.14 24.0 528 <.03 0.03 15-Jan-98 0.1 0.10 1.59 <.01 0.001 0.03 0.03 0.16 0.16 31.0 417 0.09 0.09 11-May-99 0.06 0.06 1.1 <.01 0.001 <.03 0.03 0.06 0.06 20.0 716 0.09 0.09 15-Jun-00 <.03 0.03 0.3 <.01 0.001 <.03 0.03 <.02 0.02 10.0 286 <.02 0.02 5-Jul-01 0.07 0.07 1.22 <.01 0.001 <.03 0.03 0.08 0.08 23.6 852 0.15 0.15 11-Jul-02 0.03 0.03 0.66 <.01 0.001 <.03 0.03 <.02 0.02 17.7 511 0.07 0.07 6-Aug-03 0.05 0.05 1.02 <.01 0.001 <.03 0.03 0.06 0.06 20.0 680 0.32 0.32 16-Oct-03 0.13 0.13 1.05 <.01 0.001 <.03 0.03 0.06 0.06 22.8 680 0.19 0.19 30-Apr-04 <.03 0.03 0.6 <.01 0.001 <.03 0.03 0.03 0.03 16.6 449 0.05 0.05 Jul-04 0.023 0.023 0.65 0.0001 0.0001 <0.001 0.001 0.026 0.03 15.2 450 0.027 0.03 26-Oct-04 0.06 0.06 0.9 0.01 0.01 0.04 0.04 0.03 0.03 14.7 331 0.11 0.11 26-Apr-05 <.03 0.03 0.41 <.01 0.001 <.03 0.03 <.02 0.02 14.4 315 <.02 0.02 21-Jul-05 <.03 0.03 0.66 <.01 0.001 <.03 0.03 <.02 0.02 15.3 440 <.02 0.02 4-Oct-05 <.03 0.03 0.76 <.01 0.001 <.03 0.03 <.02 0.02 18.6 467 <.02 0.02 22-Nov-05 0.04 0.04 0.75 <.01 0.001 <.03 0.03 0.02 0.02 17.4 397 0.08 0.08 16-Mar-06 <.03 0.03 0.28 <.01 0.001 <.03 0.03 <.02 0.02 13.3 248 <.02 0.02

Lagoon 3 No 4 LH Scrape A 0.01 0.01 0.69 <0.0001 0.0001 <0.001 0.001 0.041 0.041 2.21 41 0.053 0.053 Dry Conditioned No 4 LH Scrape B 0.009 0.009 0.23 <0.0001 0.0001 <0.001 0.001 0.072 0.072 3.23 28 0.046 0.046 samples BH 105 (0.2m) 0.003 0.003 0.68 0.0002 0.0002 0.001 0.001 0.200 0.200 6.8 75 0.070 0.070 BH 105 (1.7-1.9m) 0.014 0.014 0.23 0.0001 0.0001 0.034 0.034 0.007 0.007 1.47 11 0.019 0.019 BH 105 (2m) 0.003 0.003 0.55 0.0001 0.0001 0.001 0.001 0.080 0.080 6.7 69 0.060 0.060 BH 105 (4-6m) 0.023 0.023 0.55 0.0001 0.0001 0.001 0.001 0.040 0.040 4.8 27 0.130 0.130 BH 111A (1m) 0.013 0.013 0.85 0.0001 0.0001 0.001 0.001 0.054 0.054 3.5 39 0.059 0.059 BH 111A (2.5m) 0.032 0.032 0.7 0.0001 0.0001 0.001 0.001 0.058 0.058 12.4 38 0.097 0.097 BH 111A (4m) 0.028 0.028 0.49 0.0001 0.0001 0.001 0.001 0.047 0.047 12.3 38 0.076 0.076

BH 111A (5m) 0.026 0.026 0.61 0.0001 0.0001 0.001 0.001 0.047 0.047 11.4 41 0.065 0.065 Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

BH 111 (0.3-0.4m) 0.023 0.023 1.69 0.0001 0.0001 0.001 0.001 0.041 0.041 2.4 67 0.109 0.109 BH 111 (15-1.8m) 0.046 0.046 1.71 0.0001 0.0001 0.001 0.001 0.037 0.037 3.7 92 0.124 0.124 BH111 (3-3.4m) 0.021 0.021 1.39 0.0001 0.0001 0.001 0.001 0.039 0.039 6.0 83 0.082 0.082 BH 111 (4.7-4.95m) 0.011 0.011 1.61 0.0001 0.0001 0.001 0.001 0.045 0.045 11.3 70 0.076 0.076 min* 0.003 0.22 0.00001 0.0001 0.007 1.47 11 0.002 mean** 0.80 geomean** 0.0278 0.00044 0.0082 0.037 10.87 165 0.054 max 0.130 1.71 0.01 0.0600 0.200 31.00 852 0.320 log log log log log log log

* min taken as 0.1MRV (where MRV) otherwise 0.1 DL where min is

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Rugeley Borrow Pit: Source concentrations (mg/l)

Date As B Cd Pb Mo K SO4 V No 4 LH Scrape A 0.01 0.69 <0.0001 <0.001 0.041 2.21 41 0.053 No 4 LH Scrape B 0.009 0.23 <0.0001 <0.001 0.072 3.23 28 0.046 BH 105 (0.2m) 0.003 0.68 0.0002 0.001 0.200 6.8 75 0.070 BH 105 (1.7-1.9m) 0.014 0.23 0.0001 0.034 0.007 1.47 11 0.019 BH 105 (2m) 0.003 0.55 0.0001 0.001 0.080 6.7 69 0.060 Lagoon 3 BH 105 (4-6m) 0.023 0.55 0.0001 0.001 0.040 4.8 27 0.130 Dry BH 111A (1m) 0.013 0.85 0.0001 0.001 0.054 3.5 39 0.059 Conditioned samples BH 111A (2.5m) 0.032 0.7 0.0001 0.001 0.058 12.4 38 0.097 BH 111A (4m) 0.028 0.49 0.0001 0.001 0.047 12.3 38 0.076 BH 111A (5m) 0.026 0.61 0.0001 0.001 0.047 11.4 41 0.065 BH 111 (0.3-0.4m) 0.023 1.69 0.0001 0.001 0.041 2.4 67 0.109 BH 111 (15-1.8m) 0.046 1.71 0.0001 0.001 0.037 3.7 92 0.124 BH111 (3-3.4m) 0.021 1.39 0.0001 0.001 0.039 6.0 83 0.082 BH 111 (4.7-4.95m) 0.011 1.61 0.0001 0.001 0.045 11.3 70 0.076 min* 0.003 0.23 <0.0001 <0.001 0.007 1.47 11 0.019 0.00005 0.0005 mean** 0.015 0.86 0.0001 0.0013 0.047 6.30 51.4 0.076 max 0.046 1.71 0.0002 0.034 0.200 12.40 92 0.130 SD 0.012 0.52 0.00003 0.008842 0.044 3.98 24.2 0.031 95%ile 0.0369 1.697 0.000135 0.01255 0.122 12.335 86.15 0.1261 * min taken as 0.5 DL where min is

** mean calculated using detection limit value where values

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Rugeley Borrow Pit: Proposed Source concentrations (mg/l) Table 1.1 Summary of data obtained from the batch leaching of PFA at an L/S ratio of 10l/kg. Date As B Cd Pb Mo K SO4 V minimum 0 0 0 0 0 5.6 230 0 maximum 0.2 6.8 0.01 0.06 1.5 42.0 800 0.79 median 0.05 3.2 0.005 0.025 0.8 22.0 500 0.14

standard detection limit 0.03 0.1 0.02 0.02 0.001 input minimum 0.003 0.01 0.00001 0.0001 0.002 5.6 230 0.002 input 'most likely' 0.05 3.2 0.00500 0.025 0.8 22.0 500 0.14 input maximum 0.20 6.8 0.01000 0.060 1.5 42 800 0.79 log log log log log log

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Rugeley: Source concentrations (mg/l)

Lagoon 4 Date As B Cd Pb Mo K SO4 V Position 7 4 9-Nov-92 <.04 0.7 <.01 <.03 0.02 19.0 195 0.03 ASH LAGOON WEIR 10-Feb-93 <.04 0.9 0.01 0.06 <.05 13.0 120 <.05 Location ref :- 7-Jul-93 <.04 0.72 <.01 0.03 <.02 20.0 <.02 SK 0711 1705 15-Feb-94 <.04 0.22 <.01 <.03 0.02 16.0 106 <.03 13-Feb-95 <.04 0.4 <.01 <.03 <.02 15.0 283 <.03 15-Jan-96 <.03 1.08 <.01 <.03 0.02 20.0 398 <.03 22-Jul-96 470 3-Feb-97 0.05 0.7 <.01 <.03 0.14 24.0 528 <.03 15-Jan-98 0.1 1.59 <.01 0.03 0.16 31.0 417 0.09 11-May-99 0.06 1.1 <.01 <.03 0.06 20.0 716 0.09 15-Jun-00 <.03 0.3 <.01 <.03 <.02 10.0 286 <.02 5-Jul-01 0.07 1.22 <.01 <.03 0.08 23.6 852 0.15 11-Jul-02 0.03 0.66 <.01 <.03 <.02 17.7 511 0.07 6-Aug-03 0.05 1.02 <.01 <.03 0.06 20.0 680 0.32 16-Oct-03 0.13 1.05 <.01 <.03 0.06 22.8 680 0.19 30-Apr-04 <.03 0.6 <.01 <.03 0.03 16.6 449 0.05 Jul-04 0.0001 26-Oct-04 0.06 0.9 0.01 0.04 0.03 14.7 331 0.11 26-Apr-05 <.03 0.41 <.01 <.03 <.02 14.4 315 <.02 21-Jul-05 <.03 0.66 <.01 <.03 <.02 15.3 440 <.02 4-Oct-05 <.03 0.76 <.01 <.03 <.02 18.6 467 <.02 22-Nov-05 0.04 0.75 <.01 <.03 0.02 17.4 397 0.08

16-Mar-06 <.03 0.28 <.01 <.03 <.02 13.3 248 <.02 min* 0.003 0.22 0.00001 0.003 0.002 10.0 106 0.002 mean** 0.7629 18.2 423 geomean** 0.0432 0.00111 0.0314 0.033 0.04769 max 0.1300 1.5900 0.0100 0.0600 0.1600 31.0 852 0.3200 log log log log log previous model*** 0.05 0.82 0.0001 0.03 0.05 19.2 446 0.080

Lagoon 3 Ref. As B Cd Pb Mo K SO4 V Dry No 4 LH Scrape A 0.01 0.69 <0.0001 <0.001 0.041 2.21 41 0.053 Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Conditioned No 4 LH Scrape B 0.009 0.23 <0.0001 <0.001 0.072 3.23 28 0.046 samples BH 105 (0.2m) 0.003 0.68 0.0002 0.001 0.200 6.8 75 0.070 BH 105 (1.7-1.9m) 0.014 0.23 0.0001 0.034 0.007 1.47 11 0.019 BH 105 (2m) 0.003 0.55 0.0001 0.001 0.080 6.7 69 0.060 BH 105 (4-6m) 0.023 0.55 0.0001 0.001 0.040 4.8 27 0.130 BH 111A (1m) 0.013 0.85 0.0001 0.001 0.054 3.5 39 0.059 BH 111A (2.5m) 0.032 0.7 0.0001 0.001 0.058 12.4 38 0.097 BH 111A (4m) 0.028 0.49 0.0001 0.001 0.047 12.3 38 0.076

BH 111A (5m) 0.026 0.61 0.0001 0.001 0.047 11.4 41 0.065 BH 111 (0.3-0.4m) 0.023 1.69 0.0001 0.001 0.041 2.4 67 0.109 BH 111 (15-1.8m) 0.046 1.71 0.0001 0.001 0.037 3.7 92 0.124 BH111 (3-3.4m) 0.021 1.39 0.0001 0.001 0.039 6.0 83 0.082 BH 111 (4.7-4.95m) 0.011 1.61 0.0001 0.001 0.045 11.3 70 0.076 min* 0.003 0.23 0.00001 0.001 0.007 1.47 11 0.019 mean** 0.86 0.06 6.30 51.36 0.08 geomean** 0.015 0.000105 0.0013 max 0.046 1.71 0.0002 0.034 0.2 12.4 92 0.13 log log log log previous model*** 0.2 1.32 0.0002 0.001 0.07 5.6 71 0.087

* min taken as 0.1MRV (where MRV) otherwise 0.1 DL where min is

*** all single value pdfs

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Rugeley Input Values & Justification (1 of 2) Term Units Input Values Justification Borrow Pit Source predicted thickness based on Thickness m single (13) proposed design Contaminants As mg/l log triangular (0.003, 0.015, 0.046) B mg/l triangular (0.23, 0.86, 1.71) Cd mg/l log triangular (0.00005, 0.0001, 0.0002) Pb mg/l log triangular (0.0005, 0.0013, 0.034) Calculated from site (combined Lagoon 3 and 4) specific values, see Mo mg/l log triangular (0.007, 0.047, 0.2) Source term input spreadsheet K mg/l triangular (1.47, 6.3, 12.4) SO4 mg/l triangular (11, 51.4, 92) V mg/l triangular (0.019, 0.076, 0.130) Non declining Conservative assumption source term Time Offset? 0 yrs Barrier pathway In reality, indication that there is negligible infiltration. Conservatively assumed to be in exceedence of Infiltration mm/a single (400) 'barrier' hydraulic conductivity range such that seepage maximised to reflect (unrealistically) high head proposed engineered design Thickness m uniform (0.5) minimum 0.5m BES Water filled fraction single (1) Saturated porosity Actual range BES assumed 1e-11, 1e-10, 1e-9m/s,, this is a conservative range for BES as used in engineered liners. However Conductivity m/s log triangular (1e-11, 1e-10, 1e-9) values INPUT into model as 12e-10, 1.2e-9, 1.2e-8; these have been adjusted to take into account extreme driving head difference of 6m. Assumed conservatively low value Dry bulk density g/cm3 Uniform (1.91, 1.96) for basal BES liner vertical m uniform (0.05) Taken as 10% of thickness dispersivity partition As ml/g single (250) coefficients B ml/g single (0) i.e no retardation

Cd ml/g single (222) For As, Cd & Pb, taken as ConSim Pb ml/g single (435) default clay (glacial till) value. For Mo & V taken as default values in Mo ml/g single (110) absence of specific clay value. K ml/g single (0) i.e no retardation SO4 ml/g single (0) i.e no retardation V ml/g single (141)

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Rugeley Input Values & Justification (2 of 2) Aquifer Thickness m uniform (2, 4) hydraulic Derived from site specific m/m single (0.002) gradient information, borehole logs and groundwater groundwater contours degrees 61 flow direction Conductivity m/s triangular (4e-4, 1e-3, 2e-3) effective porosity fraction single (0.2) Conservative & representative dry bulk density g/cm3 2.65 values for sands & gravels lateral m single (1e-30) Default minimum value - equivalent dispersivity to no dispersion - conservative longitudinal m single (1e-30) assumption dispersivity partition As ml/g coefficients B ml/g Cd ml/g

Pb ml/g Retardation not included Conservative assumption Mo ml/g K ml/g SO4 ml/g V ml/g

Rugeley Borrow Pit Adjusted Kv and infiltration rates geological barrier' thickness (m) 0.5 0.5 0.5

Barrier Kv (m/s) 1.00E-09 1.00E-10 1.00E-11 Head difference (m) 6 6 6

Vertical hydraulic gradient iv 12 12 12 2 Seepage q (m/s per m ) through barrier (= Kviv) 1.2E-08 1.2-09 1.2E-10

Adjusted Kv (assuming iv = 1) (= q/iv) 1.2E-08 1.2E-09 1.2E-10 Equivalent infiltration (mm/a) (*1000*86400*365) 378 37.8 3.8

Rugeley Groundwater Flux width of Borrow Pit perpendicular to flow (m) 300 thickness of RTD beneath site (m) 2 hydraulic gradient (m/m) 0.002 hydraulic conductivity of RTD (m/s) 1.00E-03 groundwater flux: Q = KiA (m3/s) 0.0012 groundwater flux: Q = KiA (l/s) 1.2

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Rugeley Borrow Pit: Basal and Sidewall Liner Seepages

Approx. surface area As (m2) 98500

Approx. basal area Ab (m2) 81000 geological barrier' thickness (m) 0.5

Barrier Kv (m/s) 1.00E-10 Head difference (m) 0.5

Vertical hydraulic gradient iv 1 2 Seepage q (m/s per m ) through barrier (= Kviv) 1.00E-10

Adjusted Kv (assuming iv = 1) (= q/iv) 1.00E-10 Equivalent infiltration (mm/a) (*1000*86400*365) 3.2

Leakage Q (m3/s) through basal barrier (= KvivAb) 8.1E-06

Leakage Q (l/s) through basal barrier (= KvivAb) 8.1E-03

Leakage Q Leakage Q Seepage q (m3/s) (l/s) Assume 11m high, 0.5m thick Length at hydraulic (m/s per m2) through 1m through sidewall liner , assume Kv =Kh for segment, gradient through side segment 1m barrier emplaced BES S i barrier (= L h barrier (= segment Khih) KhihSL) (= KhihSL)

Total length of side slopes at surface, 1200 S11 (m) Total length of side slopes at base, 1000 S0 (m) Height of segment above base 11 1200 1 1.00E-10 1.20E-07 1.20E-4 10 1182 1 1.00E-10 1.18E-07 1.18E-04 9 1164 1 1.00E-10 1.16E-07 1.16E-04 8 1146 1 1.00E-10 1.15E-07 1.15E-04 7 1127 1 1.00E-10 1.13E-07 1.13E-04 6 1109 1 1.00E-10 1.11E-07 1.11E-04 5 1091 1 1.00E-10 1.09E-07 1.09E-04 4 1073 1 1.00E-10 1.07E-07 1.07E-04 3 1053 1 1.00E-10 1.05E-07 1.05E-04 2 1036 1 1.00E-10 1.04E-07 1.04E-04 1 1018 1 1.00E-10 1.02E-07 1.02E-04 0 1000 1 1.00E-10 1.00E-07 1.00E-04 Approximate area of side slopes (m2) 11001 m3/s l/s Leakage Q through side barrier 1.32E-06 1.32E-01 Leakage Q through base barrier 8.10E-06 8.10E-01 total leakage 9.42E-06 9.42E-01

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Appendix I - Site Monitoring Plan

SITE MONITORING PLAN

I.1 Groundwater

This section details the groundwater monitoring to be implemented at the site. Monitoring boreholes have been installed around and within the site at the locations shown in Drawing J24151C0/EIA/05-C, Appendix A.

I.1.1. Monitoring Boreholes

Groundwater monitoring boreholes have been previously installed at the site. A total of three boreholes detailed below are to be used to monitor groundwater quality. This will complement the monitoring carried out for the Temporary Ash Lagoons.

Borehole Location & Rationale Reference BH101 West of Borrow Pit (& south of Lagoon 4RH); up-gradient BH103 East of Borrow Pit; down-gradient BH106 North of Borrow Pit (and east of Lagoon 4RH); down-gradient Table SMP1 Groundwater Monitoring Boreholes

Drawing J24151C0/EIA/05-D shows the proposed new monitoring locations.

Borehole logs are included in Appendix D. It is not anticipated that additional boreholes are required. As a result of the ongoing and proposed PFA disposal at the site, it is feasible that some of the installations will become damaged. Should boreholes become damaged or lost, refurbishment works or replacement boreholes will be instructed, and their construction undertaken by a competent person, and their installation appropriately targeted. The detailed design of new monitoring wells will be agreed with the Environment Agency in advance of their installation.

The details of the installation and the geological sequence encountered are shown on the borehole logs. The drilling and installation were supervised by an appropriately qualified person. All boreholes have been surveyed to ordnance datum. Should any further refurbishment be required, the monitoring boreholes will be re-surveyed within approximately 1 month, and where necessary, any monitoring results obtained in the intervening period will be corrected to the revised levels.

I.1.2 Maintenance

Groundwater monitoring boreholes will be maintained in a condition that allows them to fulfil their intended purpose. Boreholes will be inspected for damage at every monitoring event. Any damage noted will be repaired where possible within approximately 1 month of detection. Where a borehole is damaged such that it requires replacement, a replacement borehole will be drilled within approximately three months, and monitoring recommenced as soon as the borehole is serviceable. Details of inspections of monitoring boreholes, remedial actions undertaken or replacement boreholes installed will be recorded in the site log, to include relevant

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

dates of inspections and remedial works and details of who carried out the inspection or works.

I.1.3 Monitoring Programme and Procedures

Groundwater levels will be measured at monthly intervals for the first 6 months after issue of the permit, and thereafter at quarterly intervals in the 3 no. specified boreholes (4 installations). Levels will be measured to an accuracy of 0.01m as m below ground level (m bgl), and will be calculated as groundwater elevation in metres above ordnance datum (m OD). This data will be reported along with the date of measurement.

Groundwater samples will be obtained from the 3 no. specified boreholes at quarterly intervals and analysed for determinands shown in Table SMP2:

• Electrical Conductivity, pH, Aluminium, Antimony, Arsenic, Boron, Cadmium, Calcium, Chloride, Chromium, Fluoride, Magnesium, Manganese, Mercury, Molybdenum, Potassium, Selenium, Sodium, Sulphate and Vanadium.

In the case of the trace metals i.e. List I or II substances, the method detection limits would be equal to or below UKDWS or MRV where appropriate. UKAS accredited methods, where available will be used.

Monitoring will be accordance with Environment Agency advice in LFTGN02 Guidance on Monitoring of Landfill Leachate, Groundwater and Surface Water, February 2003. Monitoring will be undertaken by personnel or external consultants appropriately trained in environmental monitoring procedures, and consistent with previous procedures at the site. Prior to purging and sampling, the water level will be measured using electronic dip meter. Plumb depth of boreholes will also be measured on each sampling occasion to ascertain degree if any of siltation.

As currently, boreholes will be purged using a portable submersible pump, with decontamination measures implemented between sampling. Boreholes will be purged of 3x cased well volume, and until pH and conductivity of discharge has attained a stable value as determined using hand held portable equipment, or flow through cell. In instances of low recharge, purging of 3x well volumes may be impractical, in which case a sample will be obtained once water levels have recovered sufficiently to provide adequate sample volume. Observation of the appearance (and odour if appropriate) of purge water will be recorded.

Samples will be collected in containers (using preservatives as required and) specified and provided by the laboratory. All containers will be filled to exclude all air and fitted with air tight PTFE cap.

All samples taken will be labelled with time and date of sampling, sample location and any other relevant information (or alternatively bar coded sample bottles may be used).

All samples will be delivered to the analytical laboratory within approximately 24 hours of sampling using refrigerated courier vehicles procured by the laboratory. Prior to removal from sites, samples will be stored at the appropriate temperature as specified by the laboratory. All samples will be analysed at an independent laboratory (currently TES Bretby) accredited to UKAS MCerts performance standard (EA Monitoring Certification Scheme) unless otherwise agreed with the Environment

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’

Agency. Accredited laboratories operate externally verified quality control procedures and checks on analytical work. These include spiked samples, blanks etc. Additional QC samples such as duplicates, field and trip blanks will be incorporated into the quarterly sampling as appropriate.

Records will be kept on site of determinands analysed and locations sampled, purging and sampling technique, date, sampler, results (including units, detection limits and analytical methods) and any repeat analysis or laboratory comment, or internal assessment, on the validity of the results.

A copy of the results of sampling and analysis of groundwater and levels measured for groundwater, calculated to metres above ordnance datum, will be forwarded to the EA within 1 month of being undertaken, along with details of any parameters which have been identified in excess of trigger levels (control and trigger levels, together with the action plan are detailed below in J.2). An interpretative annual review will be submitted to include all groundwater monitoring data.

I.2 Action Plan

Control and trigger levels have been developed for selected potentially polluting substances in groundwater in accordance with EA guidance “LFTGN01 Hydrogeological Risk Assessments for Landfills and the Derivation of Groundwater Control and Trigger Levels”, March 2003 and “LFTGN02 Guidance on Monitoring of Landfill Leachate, Groundwater and Surface Water”, February 2003.

The proposed trigger and control levels are listed in Table SMP3, which are consistent with those in use for the Temporary Ash Lagoons.

BH101 BH103 BH106S Analyte Unit Control Trigger Control Trigger Control Trigger Arsenic µg/l 50 500 50 500 50 500 Boron mg/l 10 20 10 20 10 20 Cadmium µg/l 0.5 1 0.5 1 0.5 1 Mercury µg/l 0.2 0.4 0.2 0.4 0.2 0.4 Molybdenum µg/l 350 700 350 700 350 700

Table SMP3 Proposed Control and Trigger Levels In the event that the control and trigger levels are breached, an action plan is proposed to ensure measures are taken to determine the cause of the breached concentration and the potential impact it may have upon the identified receptors.

The action plan is detailed below in Table SMP4 overleaf.

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Contingency Action following breach of control and / or trigger level Timescale

1. Monitoring contractor to advise site management. 1 week 2. Site management to advise EA. 2 weeks 3. Confirm breach by repeat measurements, if time allows (number and 3 months frequency of repeat samples to be discussed and agreed with the EA). 4. Review existing monitoring data and consider if the breach is likely to represent a change in baseline conditions, or if it likely to be caused by the 6 months installation. Submit evaluation report to EA for consideration. 5a. If it is agreed with the EA that the breach is likely to represent a change in baseline conditions, re-evaluate the assessment criteria and monitoring 9 months programmes and return to routine monitoring. Submit revised SMP to EA. 5b. If it is agreed with the EA that the breach is likely to be caused by the installation, review and update the Hydrogeological Risk Assessment and 9 months determine if the risks are acceptable. If so, re-evaluate the assessment criteria and monitoring programmes and return to routine monitoring. 5c. If it is agreed with the EA that the breach is caused by the installation, and the Hydrogeological Risk Assessment indicates the risks are 12 months unacceptable, develop proposed corrective or remedial measures and a strategy for monitoring their effectiveness in consultation with the EA. Table SMP4 Action Plan

Rugeley Power Limited Proposal to Restore Rugeley ‘B’ Station Borrow Pit through Landfill using Pulverised Fuel Ash Environmental Statement – Volume 3 ‘Hydrogeological Risk Assessment’