draft - north warwickshire

MAIN OFFICE & LABORATORIES Slapton Hill Barn, Blakesley Road, Slapton, Towcester, Northamptonshire. NN12 8QD

Telephone: (01327) 860060 Fax: (01327) 860430 Email: [email protected]

DRAFT

FLEXIDART

QUANTITATIVE GROUNDWATER RISK

ASSESSMENT AND REMEDIAL

OPTIONS APPRAISAL

Proposed Industrial Site Marsh Lane Water Orton

WARWICKSHIRE B46 1NS

REPORT NO: 12.11.013B

AUGUST 2016

Report No: 12-11-013b Date: August 2016

LISTERS Geotechnical Consultants Ltd www.listersgeotechnics.co.uk Tel: 01327 860060

DOCUMENT RECORD

Report Title Quantitative Groundwater Risk Assessment

Project Title Proposed Industrial Development

Project Address Marsh Lane, Water Orton, B46 1NS

Project Number 12.11.013b

Client Flexidart

Prepared By Signed................................................. Ian Evetts Director MSc, HNC, FGS, CGeol Checked By Signed................................................. Dr Mark Cowley Managing Director BSc, MSc, PhD, MCSM, FGS, CGeol, CSci For and on behalf of Listers Geotechnical Consultants

Issue No Date Status

1 9th February 2016 Draft

2 24th February 2016 Final Draft

3 12th August 2016 Final with Revised Development Proposals

© This Report is the copyright of Listers Geotechnical Consultants Ltd. Any unauthorised reproduction or

usage by any person other than the addressee is strictly prohibited.

Charlotte

Ian

Charlotte

Mark

Report No: 12-11-013b Date: August 2016


CONTENTS

QUANTITATIVE GROUNDWATER RISK ASSESSMENT REPORT .............................................................. 1 INTRODUCTION ................................................................................................................................................. 1 SCOPE OF THE INVESTIGATION .......................................................................................................................... 1 PROPOSALS ..................................................................................................................................................... 1 SITE INFORMATION AND WALKOVER SURVEY ..................................................................................................... 2 GEOLOGY ........................................................................................................................................................ 3

Published Geology ..................................................................................................................................... 3 Previous Work – January 2013 ................................................................................................................. 3

PREVIOUS WORK – JUNE 2015 ..................................................................................................................... 4 SUMMARY ........................................................................................................................................................ 4 PREVIOUS HUMAN HEALTH RISK ASSESSMENT ........................................................................................ 4

General ...................................................................................................................................................... 5 Japanese Knotweed .................................................................................................................................. 5

PREVIOUS GROUNDWATER RISK ASSESSMENT ................................................................................................... 5 General And Remedial Work Required. .................................................................................................... 5 Area A ........................................................................................................................................................ 6 Area B ........................................................................................................................................................ 6 Area C ........................................................................................................................................................ 7

QUANTITATIVE RISK ASSESSMENT AND PRODUCTION OF GROUNDWATER REMEDIAL TARGETS AND REMEDIAL OPTION APPRASIAL .......................................................................................................... 8

GENERAL ......................................................................................................................................................... 8 LEVEL 2 - GROUNDWATER ................................................................................................................................ 8 LEVEL 3 - GROUNDWATER ................................................................................................................................ 9

REMEDIATION OPTIONS APPRAISAL ........................................................................................................ 10 CONCLUSION .................................................................................................................................................. 12

REFERENCES ................................................................................................................................................ 13 APPENDICES

APPENDIX A - PLANS AND PHOTOGRAPHS

Site Location Plan

Exploratory Hole Location Plan – Showing Development Proposals

Potential Areas of Remediation Plan

Site Photographs

Groundwater Contour Plans and Hydraulic Gradients APPENDIX B – CONTAMINATION RISK ASSESSMENT WORKSHEETS

R&D P20 RTM Printouts

1 Report No: 12-11-013b Date: August 2016


QUANTITATIVE GROUNDWATER RISK ASSESSMENT REPORT

INTRODUCTION

A quantitative groundwater risk assessment has been undertaken in order to provide groundwater

remediation targets for a site at Marsh Lane, Water Orton, Warwickshire, B46 1NS. A Site Location Plan is

provided in Appendix A. The Ordnance Survey National Grid reference for the site is approximately 418250,

291550.

This report describes the previous site work and the risk assessment processes and results and gives

recommendation for possibly remedial strategies.

Instructions to undertake the original geoenvironmental consultancy were received from Flexidart. This work

started with conversations with Nicola Rushden of North Warwickshire Borough Council and a site meeting

on the 11th November 2015. Following this site meeting information was forwarded to the Environment

Agency for comment and a reply was received on the 5th January asking for a method statement with

remediation targets.

Following submission of the initial report, the development proposals have altered and this revised report has

been undertaken following instructions received from Mr. C. Fellows, architects acting on behalf of the client,

Flexidart Limited, in his email dated 20th July 2016.

This report supplements previous reports by Listers Geotechnical Consultants at the site dated January 2013

(12.11.013) and August 2016 (12.11.013a). This current report should be read in conjunction with the

previous reports for full details of the investigations undertaken at the site.

This report has been prepared for the sole use of the client and their professional advisors. This report shall

not be relied upon by third parties without the express written authority of Listers Geotechnical Consultants.

If an unauthorised third party comes into possession of this report they must not rely on it and the authors

owe them no duty of care and skill.

SCOPE OF THE INVESTIGATION

The scope of this report is to undertake a groundwater risk assessment to provide groundwater remedial

targets and to suggest a remedial strategy that can be followed by a specialist remedial contractor. The

method statement and validation reporting would then be undertaken by these contractors.

PROPOSALS

It is proposed to redevelop the site to accommodate two new industrial units, both approximately 750m2 floor

area, with an additional 580m2 of office space. The original proposals included construction into an existing

fishing lake however this is now to be retained with the new buildings and car parking areas proposed on

land, south of the lake.



SITE INFORMATION AND WALKOVER SURVEY

The original walkover survey of the site and its immediate surrounds was undertaken on the 5th December

2012 and a supplementary walkover was undertaken on the 23rd

April 2015. A selection of site photographs

is provided in Appendix A.

The site is rectangular in shape with maximum dimensions of 70m by 90m. The area of the site was

generally flat lying with only a small drop in topographic level from south to north. The site is bound to the

south by Marsh Lane (see Photo 1 – Appendix A); to the east by an operational scrapyard (Photo 2), to the

southeast by existing factory units and a yard (Photo 3). A fly-over of the M42 is location approximately

300m to the east; to the west and north is a lake (Photo 4), and 100m to the north is the River Tame. There

are six residential properties to the immediate south of the site area (Photo 5), but no others for 250m.

The site was occupied by an MOT vehicle garage and residential property at the time of the original

walkover, with the MOT garage having been closed down by the time of the second walkover. The

residential property, ‘Mallard Lodge’ (Photo 6), was located to the southeast of the area, with a large grassed

garden area to its southeast and a large (at the time flooded) hardcore area to its west. To the rear of

Mallard Lodge was a small domestic modular garage, made from wooden panels with a corrugated roof.

The majority of the site was occupied by an MOT vehicle garage in the centre and ancillary storage areas to

the south, north and northeast of the site, at the time of the original walkover. The central garage (Photo 7)

was located in a Dutch Barn, which appeared to be constructed of asbestos cement tiling in apparent

reasonable condition. There were a number of hydraulic ramps, waste oil containers and a spray booth

located inside the garage. To the south of the building, near to the frontage of the site, were the remnants of

an old petrol station (Photo 8). A large number of metal crates were stored to the front of the old petrol filling

station and there were approximately ten old and new cars and vans parked in this area (Photo 9). There

were no areas of above ground oil storage in this part of the site that were seen during the walkover survey,

but an old plinth was seen to the south of the barn with oil staining beneath.

To the north and northeast of the garage building were two distinct storage areas with a large number of cars

and vans parked and a large number of metal containers (Photo 10). The area to the north had a hardcore

surface, while the area to the northeast was mostly grassed (Photo 11).

During the second walkover survey an underground water storage tank was encountered to the rear of the

Dutch Barn, in the centre of the site, it was believed to be a drain interceptor. It smelt strongly of

hydrocarbons and solvents. This is included as Photograph 12. In addition to this an area of suspected

newly sprouting Japanese Knotweed was encountered toward the front of the site, adjacent to Marsh Lane;

and heavy oil staining was encountered to the front of the Dutch Barn/ old MOT garage. These areas are

marked on the Exploratory Hole Location Plan in the Appendices.

Therefore, the specific point sources of contamination seen during the walkover survey were the garage

building and the old petrol station, although there was considered to be a moderate risk across the majority

of the garage storage area, from potential fuel leakage from old cars and vans. In addition, the drain

interceptor to the rear of the garage and the area of oil staining to the front.



GEOLOGY

Published Geology

Reference to geological information on the area indicates that 1st Terrace River Deposits overlie strata

representing the Mercia Mudstone Group of Triassic age at the site. The River Terrace Deposits are

described as consisting of silty clays, with bands of clayey sands and sandy gravels. The Mercia Mudstone

Group strata are described as comprising ‘Red mudstone with green grey dolomitic siltstone and sandstone

beds (skerries) and nodules of gypsum, at depths greater than 30m bgl.’

Previous Work – January 2013

A previous ground investigation was carried out on the adjoining scrapyard for the client, this included three

continuous tube samples (BH’s A, B and C) and one cable percussion borehole (BH 101) being undertaken

on the site area itself; and one cable percussion borehole very close to the site boundary within the

scrapyard (BH 104).

These boreholes are included in the previous investigation and should be viewed while reading this report.

They indicate that the site was underlain by Made Ground, Terrace Deposits with Mercia Mudstone strata at

depth.

Made Ground was encountered at every location from ground level down to depth ranging from 1.30m bgl to

4.40m bgl. It generally consisted of concrete and/or dense hardcore at ground level grading into a very

loose to medium dense dark grey clayey ashy sand/ soft very sandy clay with occasional fine gravel sized

fragments of pottery, clinker, quartz and brick.

Terrace Deposits were encountered in all the boreholes (with the exception of WS C) from beneath the Made

Ground to depths ranging from 2.90m bgl to 8.00m bgl. It consisted of dense red-brown clayey sandy gravel

of flint and quartz. SPT ‘N’ values ranged from 24 to >50 and it is considered that these strata would be in

compressibility grade II to III, with regard to Burland and Burbidge (1985).

Mercia Mudstone Group strata was encountered in the cable percussion boreholes from beneath the Terrace

Deposits and down to the full depth of the investigation in each case. It consisted of very stiff red-brown clay

and very weak red-brown mudstone. SPT ‘N’ values were all >50 and it is considered that these strata

would have a coefficient of compressibility (mv) 0.1m2/MN or lower

Long term monitoring carried out as part of the project has revealed standing groundwater levels within the

natural deposits of between 0.98m and 1.95m below the existing ground level. This indicated that the water

level across the site is fairly level, with no discernible flow direction or hydraulic gradient, although it is

assumed that direction would be towards the River Tame to the north.



PREVIOUS WORK – JUNE 2015

SUMMARY

The boreholes put down across the site area, as part of the initial site investigation in June 2015, indicated

that Made Ground was encountered at each location from ground level to depths ranging from 0.25m bgl

towards the southern front of the site to 3.70m bgl towards the central eastern boundary of the site. It

consisted of a variety of material including dense brick gravel, concrete, hardcore, loose black ashy sand

across the centre of the site and soft to firm brown sandy clay across the eastern central area with various

man made gravel to cobble sized fragments within it. Hydrocarbon odours were encountered within the

Made Ground deposits at several locations across the site, primarily centred around three locations; the old

MOT garage and filling station, the drain interceptor and the central eastern boundary of the site (at

approximately 2.50m bgl).

Terrace Deposits was encountered at all locations where the Made Ground was penetrated from depths

ranging from 0.25m bgl to 3.70m bgl and down to depths ranging from 3.30m bgl to 4.90m bgl. It consisted

of a thin layer of firm to stiff grey green sandy clay (particularly towards the southern front of the site)

overlying a medium dense to dense red-brown and brown sandy fine to coarse rounded quartz and flint

gravel with many cobbles.

Mercia Mudstone Group strata were encountered at six of the locations from beneath the Terrace Deposits,

from depths of between 3.30m bgl to 4.90m bgl, and to the full depth of the investigation in each (a maximum

of 6.80m bgl in all cases and terminated on rock quality strata). It consisted of a layer of stiff becoming very

stiff red-brown very silty clay with mudstone lithorelics grading into weak red-brown silty mudstone between

4.50m bgl to 6.80m bgl. Within the cable percussion boreholes the mudstone was chiselled for one hour in

all cases and limited progress was made so the borehole was terminated.

Groundwater was encountered as seepages in seven of the exploratory holes undertaken as part of the

investigation, as both perched levels within the shallow Made Ground and standing levels within the Terrace

Deposits. Standpipes installed in some of the exploratory holes recorded standing groundwater levels

ranging from 74.55 to 74.80m AOD (or between 0.44 and 0.68m bgl). This indicated that the water level

across the site is fairly level, with a very slight hydraulic gradient towards the northwest of 0.005. Chemical

testing of groundwater from BH 4 indicated an elevated hydrocarbon concentration.

PREVIOUS HUMAN HEALTH RISK ASSESSMENT

The following qualitative risk assessment was carried out using the source-pathway-receptor principle. As

such, potential sources of contamination were assessed using the CLEA Guidelines. The fact that a

pathway must exist between a potential source and potential receptor for there to be a risk, was taken into

account. The potential human receptors evaluated for their individual risk were:

End users of the site (workers).

Surrounding residents.

Construction workers.



General

Although the previous investigation recorded areas of olfactory and visual evidence of soil contamination the

results of the soil samples tested indicated that contaminants within the soil do not pose a significant risk to

the potential end usage of the site from a human health perspective. In addition, all the areas where

contamination evidence was seen will be located below car parking areas, so reducing any risks even

further. As such, it is recommended that further investigation or remedial measures are not required from a

human health point of view. This was not the case with regard to controlled waters.

Japanese Knotweed

Japanese Knotweed is suspected to be present on the site towards the southern front of the site, as

indicated as Area C on the ‘Potential Area of Remediation’ plan attached in the Appendices. Its presence

should be confirmed by a qualified ecologist. This plant is an invasive species, must not be allowed to spread

and must be treated with care if removed. Reference should be made to the Japanese Knotweed section on

the Environment Agency’s website and the ‘Knotweed Code of Practice’ document which is available to

download. Discussion should be held with specialist remediation contactors to establish the best methods

available for control of the plant.

PREVIOUS GROUNDWATER RISK ASSESSMENT

The following risk assessment was, again, carried out using the source-pathway-receptor principle. The

procedures set out in the Environment Agency’s Remedial Targets Methodology Hydrogeological risk

assessment for contaminated land (2006), have been followed. Results were compared to the UK Drinking

Water Standards and to recently published Environmental Quality Standards. The potential environmental

receptors considered during this risk assessment were:

Controlled Waters, Receiving Stream – the River Tame, 50m to the north of the site.

Controlled Waters, Receiving Stream – the Fishing Lake, 30m to the northwest of the site.

Controlled Waters – the Secondary B aquifer beneath the site.

General And Remedial Work Required.

Elevated hydrocarbons were encountered within the groundwater taken from BH 4; located in the area of the

old filling station; and elevated values of metals and solvents were encountered in the water taken from

within the drain interceptor. Given the permeable and granular nature of the underlying Terrace Deposits, it

is considered that the liquid pollutants found in BH 4 have the potential to travel to the River Tame. The

liquids within the interceptor were sealed within that structure and appeared not to be able to escape, as a

trial pits undertaken on the outside of the structure (TP5) did not recorded any elevated solvents.

As such, it is considered that further works/ remediation will be required in several areas of the existing site

prior to/ during the redevelopment process to reduce the risk of hydrocarbons/ solvents entering the adjacent

River or pond.



The Environment Agency is the regulatory body charged with protection of controlled waters and is likely to

be a consultee in the planning process. As such, we recommend that dialogue is started with them through

the planning department to agree a Remedial Method Statement.

Reference to the ‘Potential Area of Remediation’ plan attached in the Appendices indicates Areas A and B,

where it is considered that further works will be required.

Area A

Area A is located around the old filling station and MOT garage and groundwater taken from BH 4 revealed a

total petroleum hydrocarbon concentration of 42,000µg/l. Soil samples taken in the area indicated that

hydrocarbon contamination was limited to the top metre and it is likely that it was caused by an above

ground tank located at the rear of the old filling station, where oil staining was visible on the ground. The

values of total TPH recorded in this area ranged from 660mg/kg in TP A2 at 0.30m bgl reducing to 20mg/kg

at 0.70m; and 470mg/kg in CT F at 0.50m bgl reducing to 49mg/kg at 1.00m bgl. It is considered likely that

any remedial process will need to address the existing TPH contamination at shallow depth within the soil

and the existing TPH contamination within the groundwater in this area. There are many different remedial

techniques that can be applied for sites with similar contamination, for example the excavation and removal

of the soil to a treatment hub in conjunction with a pump and treat of the groundwater may prove viable or

the ex-situ bioremediation of the site in conjunction with in-situ chemical oxidation of the groundwater.

Discussion should be held with specialist remediation contactors to establish the best methods available,

and one which also deals with the other areas of concern on site.

Area B

Area B is located around the old drain interceptor located to the rear of the old MOT garage. A water sample

taken from inside the interceptor revealed elevated metal and solvent values in the water, these included

Arsenic at 630µg/l (UKDWS 10µg/l; EQS 50µg/l); Copper at 5600µg/l (UKDWS 2000µg/l; EQS 1-28µg/l);

Lead at 2000µg/l (10µg/l; EQS 7.2µg/l); Naphthalene at 2000µg/l (no EQS); Xylenes at 3400µg/l (WHO DWS

500µg/l) and trimethylbenzenes at 2800µg/l (no EQS). However, soil samples taken from TP A5, outside the

interceptor, did not reveal levels above the relevant environmental quality standards.

As such, it is considered that the water within the drain interceptor will require pumping out and disposing

and the structure will require cleaning and demolishing, along with drains leading towards it. In addition, it is

likely that some soil surrounding the drains and the interceptor will require removal or treatment, but that is

likely to be determined on site. Reference to groundwater samples taken from BH 3, just down hydraulic

gradient from the area of the interceptor did not reveal any elevated solvents levels, and therefore it is

considered unlikely that the groundwater in this area is adversely affected.



Area C

Area C is located to the southern front of the site and is an area of concern because of the possible

existence of Japanese Knotweed. This plant is an invasive species, must not be allowed to spread and must

be treated with care if removed. Reference should be made to the Japanese Knotweed section on the

Environment Agency’s website and the ‘Knotweed Code of Practice’ document which is available to

download. Discussion should be held with specialist remediation contactors to establish the best methods

available for control of the plant.



QUANTITATIVE RISK ASSESSMENT AND PRODUCTION OF GROUNDWATER REMEDIAL

TARGETS AND REMEDIAL OPTION APPRASIAL

Following the site investigation and site characterisation undertaken in report 12.11.013a, remedial targets

and a remedial options appraisal were requested by the Environment Agency in their email dated January

2016. For producing the groundwater remedial targets the procedures set out in the Environment Agency’s

Remedial Targets Methodology Hydrogeological risk assessment for contaminated land (2006), have been

followed. Results have been compared to the UK Drinking Water Standards and EQS’s. The potential

environmental receptors considered during this risk assessment were, as before:

Controlled Waters, Receiving Stream – the River Tame, 50m to the north of the site.

Controlled Waters, Receiving Stream – the Fishing Lake, 30m to the northwest of the site.

Controlled Waters – the Secondary B aquifer beneath the site.

GENERAL

As explained above groundwater contaminated with TPH was encountered in BH4 with a total concentration

of 42,000µg/l. Reference to the desk indicated that discussions with the local Petroleum Officer (Robert

Bryson) stated that two 500G and one 1000G underground storage tanks were removed from the former

forecourt area of the petrol filling station by Edwards Ltd in January 1994.

Soil samples taken in the area indicated that hydrocarbon contamination was limited to the top metre and it

is likely that it was caused by an old above ground tank that was located at the rear of the old filling station,

where oil staining was visible on the ground, and a plinth was visible.

These two potential sources were located in Area A, as shown on the appended plan, and were thought to

require remediation to prevent ongoing pollution of the above recognised receptors. In order to establish a

level to which the groundwater needs remediating quantitative risk assessment was undertaken in

accordance with the Environment Agency’s Remedial Targets Methodology Hydrogeological risk assessment

for contaminated land (2006)

LEVEL 2 - GROUNDWATER

Within the methodology set out above, assessment for groundwater starts at Level 2 as the contaminants

are already dissolved within the groundwater. Level 2 for groundwater is a direct comparison between

remedial target and recorded contaminant concentration.

The concentrations of TPH in the groundwater, in the area in the south of the site, fail the Level 2 target of

10µg/l (which is taken from the old UKDWS 1989 for mineral oils) and therefore, further assessment has

been undertaken.



LEVEL 3 - GROUNDWATER

Level 3 takes account of the potential attenuation of contaminants by the soils as they move through the

groundwater. The Level 3 model has been used to predict likely TPH concentrations down-gradient of the

source as a result of the following:

Degradation including biological breakdown.

Sorption onto the aquifer soil matrix.

Volatilisation of semi-volatile and volatile compounds.

Dispersion.

The Level 3 remedial target is established by deriving these attenuation factors. The worksheets are

provided in the Appendices.

To model a likely plume, the hydrocarbon fractions have been considered separately. Research indicates

that LNAPL plumes tend to remain localised and extend to relatively short distances from their sources. This

will of course be dependent upon the groundwater flow and geochemistry of the aquifer.

Conservative values have been used where site specific data is not available and ranges of values have

been entered to test the sensitivity of the effects on the target. These are shown below along with their

sources:-

Property Unit Source of Information Value

Half Life of degradation in

groundwater

Days Stated equivalence from Howard et al. “Environmental

Degradation Rates”1991

Various

Width of plume m Site measurement 25

Plume thickness m Site measurement 4

Saturated aquifer thickness m Site measurement 5

Density of aquifer material g/cm3 Site measurement from SPT data 1.9

Effective porosity of aquifer % Site measurement from PSD between 20% and 30%,

therefore take conservative option

20%

Hydraulic gradient % Site measurement 0.005

Hydraulic conductivity m/d Site measurement 0.864

Distance to compliance

point

m Site measurement 30

Fraction of organic carbon % Assumed 1%

Organic carbon partition

coefficient

l/kg EA “Petroleum hydrocarbons in groundwater” 2006

Various



Using the values stated above, the UKDWS for mineral oils of 10µg/l and the RTM spreadsheet published by

the EA the following remedial targets have been derived for the various hydrocarbon fractions:-

TPH Fraction RTM Remedial Target value (µg/l) Value from BH 4 (µg/l)

C8 – C10 88 280

C10 – C12 182 2700

C12 – C16 332 17000

C16 – C21 26 19000

C21 – C35 12.5 3800

Discussion As can be seen the TPH fraction C8 – C35 all exceeded the stated RTM remedial targets and as such

groundwater in the area of BH 4 will require remediation. It has also been recommended that the near

surface hydrocarbon soaked Made Ground in Area A, as set out in the plan, be removed/remediated to

below detection level to avoid ongoing contamination of the underlying groundwater in this location.

REMEDIATION OPTIONS APPRAISAL

Although the contamination has been occurring over a long time period, prior to redevelopment, it is

recommended that every effort is made to ensure that the contamination does not migrate further off-site and

does not cause any negative environmental or social issues, particularly during construction, when the soil is

exposed or bored through.

There are a range of options that may be suitable to remediate the site. The final options will depend upon

the requirements of the developer with relation to cost and timeframe.

As well as cost and time constraints, the remedial works will also need to take into account waste production,

access and effects of surrounding neighbours.



Each option that could potentially be used at the site for the organic hydrocarbon contamination has been

listed below together with the advantages and disadvantages of each.

Remediation Method

Advantages Disadvantages

Dig and Dump Removes shallow diesel contaminated soils entirely. Rapid solution.

Heavy vehicle traffic will be a problem. Will be expensive. Potential for vapours to cause a nuisance.

Monitored Natural Attenuation (MNA)

Creation of permanent monitoring wells and a long term sampling and testing programme to monitor the natural attenuation of contaminants with time. Low cost option. No waste soils.

Excessive time frame, will take years to complete monitoring. Would require off-site boreholes down length of plume. On-site risks from contaminated soils remain.

Physical Barrier Create a physical barrier at the upstream end of the site to prevent further migration off-site.

Imported material required to form the barrier. Vehicle movement to bring material to site. May require future maintenance. Does not eliminate the problems from the contaminated soils and groundwater left in-situ.

Permeable Chemical Reactive Barrier

Allowing the contaminants to move off-site within groundwater, but through a barrier containing chemicals that will attenuate the contamination as it passes through. Low vehicle traffic. No waste soils.

Likely to be expensive. Long time frame required. Does not eliminate the problems of vapours from the contamination left on site. May require future maintenance.

Ex-situ Bioremediation

Treatment of soils on site without need for vehicle movements. Lower costs. Soil could be reused.

Need space on site to store soils whilst being treated. Problems with odours and vapours to neighbouring properties. Long time scale required.

In-situ Bioremediation (eg PlumeStop by Regenesis)

Injection of solution and additives directly into aquifer. Would work best in the Hackney Gravel. No excavation required. Will reduce vapours entering the air during construction. Will prevent vapours entering the new building negating the requirement for a membrane. No vehicles movements, little disruption. Sustainable process. May be able to be undertaken alongside construction and beneath the future building.

Unsuitable for clay soils. May delay start on site.

Soil Vapour Extraction and Air Sparging

Extracts volatiles from high permeability soils. Rapid method. No vehicle movement. Cost effective.

May take more than one round of treatment. Limited to volatile contaminants. Unsuitable for low permeability soils.

Chemical Oxidation

Fast clean up rates for volatile contaminants. No vehicle movement.

Unsuitable for low permeability soils. Requires the use of noxious chemicals (e.g H2O2)

Ex-situ Thermal Desorption

Burns off organic contaminants quickly. Cost effective compared with landfilling. Low vehicle movement. Soil may be re-used.

May be expensive. Unsuitable for topsoils or organic rich soils Soil requires excavating and thus vapours may be a problem. Soil structure will be damaged, thus not suitable for engineering re-use. Method may attract complaints from neighbours. Various licenses and permits required.

In-site Thermal Treatment (eg ERM UK)

Burns or steams off organic contaminants quickly. Cost effective compared with landfilling. Low vehicle movement. No soil excavation.

May be expensive. Unsuitable for topsoils or organic rich soils. Soil structure may be damaged. Various licenses and permits required.

In-situ Physical or Chemical Stabilisation (eg Celtic Technologies & Biogenie)

Will stop further migration off-site. Will prevent vapours entering the air during construction. Will prevent vapours entering the new building negating the requirement for a membrane. Short time frame required. Low vehicle movements.

May be expensive. Does not remove or destroy contaminants. Potential for volume increase of soils. May require long term monitoring.



CONCLUSION

Given the above remedial options appraisal and likely development timeframe (remediation results required

quickly) it is considered likely that in-situ chemical oxidation is likely to be an appropriate method of

remediating the groundwater at the location of BH 4. The area of near surface hydrocarbon impacted Made

Ground could be treated either by removal to a licensed treatment centre and replacement with inert material

or ex-situ bioremediation. Removal would be quicker but more expensive and ex-situ bioremediation taking

longer but costing less.

It is recommended that the remediation contractors are requested to assess the site based upon their

specialist knowledge of treating diesel and petrol type contamination in soils and groundwater with time

frames, costs and logistics in mind. A combination of methods will likely be the best solution at this site.

Once the chosen methods have been agreed a Remedial Method Statement will be produced by the

contractor and agreed by the Environment Agency/ Local Authority. Following remediation a Validation

Report will need to be produced.



REFERENCES

1. Site Investigations, Code of Practice, BS5930:2015.

2. Investigation of Potentially Contaminated Sites – Code of Practice, BS10175, 2011.

3. National House Building Council (NHBC) Standards, Chapter 4.1 Land Quality – Managing Ground

Conditions. 2011.

4. Environment Agency, The Model Procedures for the Management of Land Contamination, CLR 11,

2004.

5. Environment Agency, Human Health Toxicological Assessment of Contaminants in Soil, January

2009.

6. Amherst Scientific Publishers; The Total Petroleum Hydrocarbon Criteria Working Group (TPHCWG)

- Volumes 1 -5, March 1998.

7. The LQM/CIEH S4ULs for Human Health Risk Assessment (S4UL3032), ISBN978-0-9931084-0-2,

January 2015

8. Health and Safety Executive (HSE), Protection of Workers and the General Public during

Development of Contaminated Land, HS(G) 66. HMSO London 1991.

9. Environment Agency, Remedial Target Methodology, Hydrogeological Risk Assessment for

Contaminated Land, 2006.

10. Soils for Civil Engineering Purposes, BS1377, 1990.

11. Environment Agency, Technical Guidance WM3, 1st edition, ‘Guidance on the classification and

assessment of waste, May 2015.

Listers Geotechnical Consultants Ltd www.listersgeotechnics.co.uk Tel: 01327 860060

APPENDIX APLANS AND PHOTOGRAPHS

Approximate Site Location

1 : 200,000

1 : 50,000

Key:

Site Location Plan

Site: Marsh Lane, Water Orton, B46 1NS

NTS Job No: 12.11.013b Drawn By: HC

Title:

Scale:


BH5

BH2

BH1

BH4

BH3

TP A4

TP A5

TP A1

TP A2

TP A3

CT E

CT E

CT B

CT A

CT E

CT C

TP A6

CT G

Machine Excavated Trial Pit

Cable Percussive Borehole

Continuous Tube Sampler Borehole

Key:

Approximate Extent of Historical Pond

Exploratory Hole Location Plan - Proposed Development


NTS Job No: 12.11.013b Drawn By: BL

Title:

Scale:


BH5

BH2

BH1

BH3

TP A4

TP A1

TP A3

CT E

CT A

CT D

CT C

TP A6

CT G




Key:

Approximate Extent of Historical Pond

Area B - Drain filled with solvents. Need removal and demolition.

Area C - Japanese Knotweed

Area A - Made Ground to approx 1m bgl contaminated with hydrocarbons and groundwater impacted also.

TP A5

BH4

CT E

TP A2

CT B

Potential Areas of Remediation Plan



Title:

Scale:


Listers Geotechnical Consultants

Date:- January 2013 Site Photographs Job No. :- 12-11-013b

Job Ref.:- Marsh Lane, Water Orton B46 1NS.

Photograph 1

Photograph 2




Photograph 3

Photograph 4




Photograph 5

Photograph 6




Photograph 7

Photograph 8




Photograph 9

Photograph 10




Photograph 11

BH5

BH2

BH1

BH4

BH3

TP A4

TP A5

TP A1

TP A2

TP A3

CT E

CT B

CT E

CT C

TP A6

CT G




Key:

CT A

74.79m AOD

74.67m AOD

74.69m AOD

74.72m AOD

CT F

Hydraulic Gradient Plan



Title:

Scale:



APPENDIX B

CONTAMINATION RISK ASSESSMENT WORKSHEETS

R&D Publication 20 Remedial Targets Worksheet, Release 3.1 0 User specified value for partition coefficient

1 Calculate for non-polar organic chemicals

Level 3 - Groundwater See Note 0 Calculate for ionic organic chemicals (acids)

Input Parameters (using pull down menu) Variable Value Unit Source Select Method for deriving Partition Co-efficient (using pull down menu)

Calculated concentrations for

Contaminant from Level 1 distance-concentration graph

Target Concentration CT 1.00E-02 mg/l from Level 1 Entry if specify partition coefficient (option)

Soil water partition coefficient Kd 0.00E+00 l/kg Ogata Banks

Entry for non-polar organic chemicals (option) From calculation sheet

Select analytical solution (click on brown cell below, then on pull-down menu) Fraction of organic carbon in aquifer foc 1.00E-02 fraction Distance Concentration

Equations in HRA publication Organic carbon partition coefficient Koc1.59E+03

l/kg mg/l

0 Entry for ionic organic chemicals (option) 0 2.8E-01

Simulate vertical dispersion in 1 directionApproach for simulating vertical dispersion: Sorption coefficient for related species Koc,n 0.00E+00 l/kg 1.5 2.51E-01

Simulate vertical dispersion in 2 directions 2 Sorption coefficient for ionised species Koc,i 0.00E+00 l/kg 3.0 2.25E-01

Select nature of decay rate (click on brown cell below, then on pull-down menu) pH value pH 0.00E+00 4.5 2.02E-01

Apply degradation rate to dissolved pollutants onlyApproach for simulating degradation of pollutants: acid dissociation constant pKa 0.00E+00 6.0 1.81E-01

Apply degradation rate to pollutants in all phases (e.g. field derived value, laboratory study for aquifer + water mix, radioactive decay)Source of parameter value Fraction of organic carbon in aquifer foc 0.00E+00 fraction 7.5 1.63E-01

Initial contaminant concentration in groundwater at plume core C0 2.80E-01 mg/l Site testing 9.0 1.46E-01

Half life for degradation of contaminant in water t1/2 3.65E+02 days highest for xylene (howard et al.) Soil water partition coefficient Kd 1.59E+01 l/kg 10.5 1.31E-01

Calculated decay rate l 1.90E-03 days-1

12.0 1.18E-01

Width of plume in aquifer at source (perpendicular to flow) Sz 2.50E+01 m Site measurement 13.5 1.06E-01

Plume thickness at source Sy 4.00E+00 m Site measurement Dispersivity based on Xu & Eckstein (1995)0 15.0 9.47E-02

Saturated aquifer thickness da 5.00E+00 m Site measurement Define dispersivity (click brown cell and use pull down list) Dispersivities 10%, 1%, 0.1% of pathway length1 16.5 8.50E-02

Bulk density of aquifer materials r 1.90E+00 g/cm3

Site measurement User defined values for dispersivity2 18.0 7.62E-02

Effective porosity of aquifer n 2.00E-01 fraction Site measurement (PSD) 19.5 6.84E-02

Hydraulic gradient i 5.00E-03 fraction Site measurement Enter value Calc value Xu & Eckstein m 21.0 6.13E-02

Hydraulic conductivity of aquifer K 8.64E-01 m/d Site measurement Longitudinal dispersivity ax 0.00E+00 3.00E+00 2.13E+00 m Note 22.5 5.50E-02

Distance to compliance point x 3.00E+01 m Site measurement Transverse dispersivity az 0.00E+00 3.00E-01 2.13E-01 m 24.0 4.93E-02

Distance (lateral) to compliance point perpendicular to flow direction z 0.00E+00 m Vertical dispersivity ay 0.00E+00 3.00E-02 2.13E-02 25.5 4.42E-02

Distance (depth) to compliance point perpendicular to flow direction y 0.00E+00 m Note values of dispersivity must be > 0 27.0 3.97E-02

0 Time since pollutant entered groundwater t 1.00E+100 days time variant options only For calculated value, assumes ax = 0.1 *x, az = 0.01 * x, ay = 0.001 * x 28.5 3.55E-02

Parameters values determined from options Xu & Eckstein (1995) report ax = 0.83(log10x)2.414

; az = ax/10, ay = ax/100 are assumed 30.0 3.18E-02

Partition coefficient Kd 1.59E+01 l/kg see options

Longitudinal dispersivity ax 3.00E+00 m see options The measured groundwater concentration should be compared

Transverse dispersivity az 3.00E-01 m see options with the Level 3 remedial target to determine the need for further action.

Vertical dispersivity ay 3.00E-02 m see options Ogata Banks 1 Note if contaminant is not subject to first order degradation, then set half life as 9.0E+99.

0 Domenico - Steady stateDomenico - Steady state 0

Calculated Parameters Variable 1 Ogata BanksDomenico - Time Variant 0

Groundwater flow velocity v 2.16E-02 m/d

Retardation factor Rf 1.52E+02 fraction

Decay rate used l 1.25E-05 d-1

Rate of contaminant flow due to retardation u 1.42E-04 m/d

Contaminant concentration at distance x, assuming one-way vertical dispersion CED 3.18E-02 mg/l

Attenuation factor (one way vertical dispersion, CO/CED) AF 8.79E+00 Site being assessed: Marsh Lane, Water Orton

Completed by: Murray Bateman

8.79E-02 Date: ########

Remedial Targets #REF! Version: 1

Remedial Target 8.79E-02 mg/l For comparison with measured groundwater concentration.

Ogata Banks

Distance to compliance point 30 m

Concentration of contaminant at compliance point CED/C0 3.18E-02 mg/l Ogata Banks

after 1.0E+100 days

Care should be used when calculating remedial targets using the time variant options as this may result in an overestimate of the remedial target.

The recommended value for time when calculating the remedial target is 9.9E+99.

This worksheet should be used if pollutant transport and degradation is best described by a

first order reaction. If degradation is best desribed by an electron limited degradation such

as oxidation by O2, NO3, SO4 etc than an alternative solution should be used

By setting a long travel time it will give the steady state solution, which should be used to

calculate remedial targets.

Calculate for non-polar organic chemicals

Note graph assumes plume disperses vertically in one direction only. An alternative

solution assuming the centre of the plume is located at the mid-depth of the aquifer is

presented in the calculation sheets.

This sheet calculates the Level 3 remedial target for groundwater, based on the distance to

the receptor or compliance located down hydraulic gradient of the source Three solution

methods are included, the preferred option is Ogata Banks.

Simulate vertical dispersion in 1 direction

C8 - C10

Ogata Banks

Dispersivities 10%, 1%, 0.1% of pathway length

Apply degradation rate to dissolved pollutants only

0.0E+00

5.0E-02

1.0E-01

1.5E-01

2.0E-01

2.5E-01

3.0E-01

0 5 10 15 20 25 30 35

Ca

lcu

late

d c

on

ce

ntr

ati

on

(m

g/l)

Distance (m)

Remedial targets worksheet v3.1 24/02/2016, 10:03

RTM c8 to c10.xlsxLevel3 Groundwater












l/kg mg/l

0 Entry for ionic organic chemicals (option) 0 1.7E+01

Simulate vertical dispersion in 1 directionApproach for simulating vertical dispersion: Sorption coefficient for related species Koc,n 0.00E+00 l/kg 1.5 1.43E+01

Simulate vertical dispersion in 2 directions 2 Sorption coefficient for ionised species Koc,i 0.00E+00 l/kg 3.0 1.20E+01

Select nature of decay rate (click on brown cell below, then on pull-down menu) pH value pH 0.00E+00 4.5 1.01E+01

Apply degradation rate to dissolved pollutants onlyApproach for simulating degradation of pollutants: acid dissociation constant pKa 0.00E+00 6.0 8.45E+00

Apply degradation rate to pollutants in all phases (e.g. field derived value, laboratory study for aquifer + water mix, radioactive decay)Source of parameter value Fraction of organic carbon in aquifer foc 0.00E+00 fraction 7.5 7.09E+00

Initial contaminant concentration in groundwater at plume core C0 1.70E+01 mg/l Site testing 9.0 5.95E+00

Half life for degradation of contaminant in water t1/2 2.04E+02 days highest for Acenaphthylene (howard et al.) Soil water partition coefficient Kd 5.01E+01 l/kg 10.5 5.00E+00


12.0 4.20E+00

Width of plume in aquifer at source (perpendicular to flow) Sz 2.50E+01 m Site measurement 13.5 3.52E+00

Plume thickness at source Sy 4.00E+00 m Site measurement Dispersivity based on Xu & Eckstein (1995)0 15.0 2.96E+00

Saturated aquifer thickness da 5.00E+00 m Site measurement Define dispersivity (click brown cell and use pull down list) Dispersivities 10%, 1%, 0.1% of pathway length1 16.5 2.48E+00


Site measurement User defined values for dispersivity2 18.0 2.09E+00

Effective porosity of aquifer n 2.00E-01 fraction Site measurement (PSD) 19.5 1.75E+00

Hydraulic gradient i 5.00E-03 fraction Site measurement Enter value Calc value Xu & Eckstein m 21.0 1.47E+00

Hydraulic conductivity of aquifer K 8.64E-01 m/d Site measurement Longitudinal dispersivity ax 0.00E+00 3.00E+00 2.13E+00 m Note 22.5 1.23E+00

Distance to compliance point x 3.00E+01 m Site measurement Transverse dispersivity az 0.00E+00 3.00E-01 2.13E-01 m 24.0 1.03E+00

Distance (lateral) to compliance point perpendicular to flow direction z 0.00E+00 m Vertical dispersivity ay 0.00E+00 3.00E-02 2.13E-02 25.5 8.68E-01

Distance (depth) to compliance point perpendicular to flow direction y 0.00E+00 m Note values of dispersivity must be > 0 27.0 7.28E-01

0 Time since pollutant entered groundwater t 1.00E+100 days time variant options only For calculated value, assumes ax = 0.1 *x, az = 0.01 * x, ay = 0.001 * x 28.5 6.11E-01


; az = ax/10, ay = ax/100 are assumed 30.0 5.12E-01











Contaminant concentration at distance x, assuming one-way vertical dispersion CED 5.12E-01 mg/l



3.32E-01 Date: ########



Ogata Banks


Concentration of contaminant at compliance point CED/C0 5.12E-01 mg/l Ogata Banks

after 1.0E+100 days
















C12 - C16

Ogata Banks



0.0E+00

2.0E+00

4.0E+00

6.0E+00

8.0E+00

1.0E+01

1.2E+01

1.4E+01

1.6E+01

1.8E+01

0 5 10 15 20 25 30 35

Ca

lcu

late

d c

on

ce

ntr

ati

on

(m

g/l)

Distance (m)



Date of Workbook Issue: October 2006

Details to be completed for each assessment

Site Name:

Site Address:

Completed by:

Date: 03-Feb-16 Version: 1

Contaminant C16 - C21

Target Concentration (CT) 0.01 mg/l Origin of CT:

Data carried forward from an earlier worksheet are identified by a light green background

Marsh Lane, Water Orton

B46 1NS

IMPORTANT: To enable MS Excel worksheet, click Tools, Add -Ins, Analysis Tool Pak and Analysis Tool Pak-VBA (to calculate error functions).

The spreadsheet also includes a porosity calculation worksheet, a soil impact calculation worksheet and a worksheet that performs some simple hydrogeological

calculations.

Hydrogeological risk assessment for land contamination

UKDWS

Murray Bateman

This worksheet has been produced in combination with the document 'Remedial Targets Methodology: Hydrogeological risk assessment for land contamination (

Environment Agency 2006).

Users of this worksheet should always refer to the User Manual to the Remedial Targets Methodology and to relevant guidance on UK legislation and

policy, in order to understand how this procedure should be applied in an appropriate context.

© Environment Agency, 2006. (Produced by the Environment Agency's Science Group)

The calculation of equations in this worksheet has been independently checked by Entec (UK) Ltd on behalf of the Environment Agency.

All rights reserved. You will not modify, reverse compile or otherwise dis-assemble the worksheet.

It is recommended that a copy of the original worksheet is saved (all data fields in the original copy are blank).

Remedial Targets Worksheet , Release 3.1

This worksheet can be used to determine remedial targets for soils (Worksheets Level 1 Soil, Level 2 and Level 3 Soil) or to determine remedial targets for groundwater (Level 3

Groundwater). For Level 3, parameter values must be entered separately dependent on whether the assessment is for soil or groundwater. For soil, remedial targets are

calculated as either mg/kg (for comparision with soil measurements) or mg/l (for comparison with leaching tests or pore water concentrations).

Site details entered on this page are automatically copied to Level 1, 2 and 3 Worksheets.

Worksheet options are identified by brown background and employ a pull-down menus. Data entry are identified as blue background.

Data origin / justification should be noted in cells coloured yellow and fully documented in subsequent reports.

Liability: The Environment Agency does not promise that the worksheet will provide any particular facilities or functions. You must ensure that the worksheet meets your needs and you remain solely

responsible for the competent use of the worksheet. You are entirely responsible for the consequences of any use of the worksheet and the Agency provides no warranty about the fitness for purpose or

performance of any part of the worksheet. We do not promise that the media will always be free from defects, computer viruses, software locks or other similar code or that the operation of the worksheet will

be uninterrupted or error free. You should carry out all necessary virus checks prior to installing on your computing system.

Environment Agency Publication 20, Remedial Targets worksheet v3.124/02/2016, 10:04

RTM c16 to c21.xlsxIntroduction












l/kg mg/l

0 Entry for ionic organic chemicals (option) 0 3.8E+00

Simulate vertical dispersion in 1 directionApproach for simulating vertical dispersion: Sorption coefficient for related species Koc,n 0.00E+00 l/kg 1.5 3.76E+00

Simulate vertical dispersion in 2 directions 2 Sorption coefficient for ionised species Koc,i 0.00E+00 l/kg 3.0 3.72E+00

Select nature of decay rate (click on brown cell below, then on pull-down menu) pH value pH 0.00E+00 4.5 3.68E+00

Apply degradation rate to dissolved pollutants onlyApproach for simulating degradation of pollutants: acid dissociation constant pKa 0.00E+00 6.0 3.64E+00

Apply degradation rate to pollutants in all phases (e.g. field derived value, laboratory study for aquifer + water mix, radioactive decay)Source of parameter value Fraction of organic carbon in aquifer foc 0.00E+00 fraction 7.5 3.60E+00

Initial contaminant concentration in groundwater at plume core C0 3.80E+00 mg/l Site testing 9.0 3.56E+00

Half life for degradation of contaminant in water t1/2 4.30E+03 days highest for Flourene (howard et al.) Soil water partition coefficient Kd 1.26E+02 l/kg 10.5 3.52E+00


12.0 3.48E+00

Width of plume in aquifer at source (perpendicular to flow) Sz 2.50E+01 m Site measurement 13.5 3.44E+00

Plume thickness at source Sy 4.00E+00 m Site measurement Dispersivity based on Xu & Eckstein (1995)0 15.0 3.41E+00

Saturated aquifer thickness da 5.00E+00 m Site measurement Define dispersivity (click brown cell and use pull down list) Dispersivities 10%, 1%, 0.1% of pathway length1 16.5 3.37E+00


Site measurement User defined values for dispersivity2 18.0 3.33E+00

Effective porosity of aquifer n 2.00E-01 fraction Site measurement (PSD) 19.5 3.29E+00

Hydraulic gradient i 5.00E-03 fraction Site measurement Enter value Calc value Xu & Eckstein m 21.0 3.26E+00

Hydraulic conductivity of aquifer K 8.64E-01 m/d Site measurement Longitudinal dispersivity ax 0.00E+00 3.00E+00 2.13E+00 m Note 22.5 3.22E+00

Distance to compliance point x 3.00E+01 m Site measurement Transverse dispersivity az 0.00E+00 3.00E-01 2.13E-01 m 24.0 3.18E+00

Distance (lateral) to compliance point perpendicular to flow direction z 0.00E+00 m Vertical dispersivity ay 0.00E+00 3.00E-02 2.13E-02 25.5 3.15E+00

Distance (depth) to compliance point perpendicular to flow direction y 0.00E+00 m Note values of dispersivity must be > 0 27.0 3.11E+00

0 Time since pollutant entered groundwater t 1.00E+100 days time variant options only For calculated value, assumes ax = 0.1 *x, az = 0.01 * x, ay = 0.001 * x 28.5 3.07E+00


; az = ax/10, ay = ax/100 are assumed 30.0 3.03E+00











Contaminant concentration at distance x, assuming one-way vertical dispersion CED 3.03E+00 mg/l



1.25E-02 Date: ########



Ogata Banks


Concentration of contaminant at compliance point CED/C0 3.03E+00 mg/l Ogata Banks

after 1.0E+100 days
















C21 - C35

Ogata Banks



0.0E+00

5.0E-01

1.0E+00

1.5E+00

2.0E+00

2.5E+00

3.0E+00

3.5E+00

4.0E+00

0 5 10 15 20 25 30 35

Ca

lcu

late

d c

on

ce

ntr

ati

on

(m

g/l)

Distance (m)



draft - north warwickshire

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