Phase III Remediation & Validation Proposals at Duckett Street, Burnley

Client: Calico Homes Our ref: LG27759

Date: Dec 2015

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Table of Contents

1 OBJECTIVES 1

2 SITE LOCATION, TOPOGRAPHY AND DESCRIPTION 2

3 PREVIOUS SITE INVESTIGATION IDENTIFIED CONTAMINATION 3

4 REMEDIATION STRATEGY 4

5 VALIDATION SAMPLING STRATEGY 6

6 FURTHER CONSIDERATIONS 7

6.1 Health and Safety - Construction Workers .............................................................................. 7

6.2 Site Variations ............................................................................................................................ 7

7 PROPOSED VALIDATION PROCESS 9

7.1 Capping System - Sampling Strategy Imported Material ....................................................... 9

Further Verification ............................................................................................................................. 11

8 REPORTING 12

9 THIRD PARTY CONSULTATIONS 13

APPENDIX A – SITE INVESTIGATION PLAN 15

APPENDIX B – PROPOSED REMEDIATION / VALIDATION SAMPLING STRATEGY 16

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1 Objectives

1.1 Sutcliffe Investigations propose to conduct remediation validation works including soil

sampling and analysis on behalf of our client Calico Homes in order to enable

contaminated land remediation and validation as appropriate to their proposed

development at Land at Duckett Street, Burnley.

1.2 The present document outlines Sutcliffe Investigations proposals for Remediation

Strategies, and includes the following:

(i) Soil sampling and analysis to be conducted for purposes of site

characterisation and remediation planning

(ii) Anticipated remediation strategy

(iii) Soil sampling and analysis to be conducted for remediation validation

purposes

1.3 As discussed below, the sampling and analysis proposals set out in this document

are produced in light of the site investigation previously conducted by Sutcliffe

Investigations for this site. This report and the outlined strategy should be read in

conjunction with:

• Sutcliffe, LG27759 Phase II Geotechnical and Environmental Report at Duckett

Street, Burnley - September 2015

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2 Site Location, Topography and Description

2.1 The site is located on land at Duckett Street Burnley, Lancashire BB11 4AF. The site

location is shown on the drawings presented in Appendix A of this report. Site details

are summarised in the table below. The remediation plan is shown on Drawing No.:

27759-703.

Table 2.1: Summary of Site Description

Detail Remarks

Location 1 mile northwest west of Burnley Town Centre

NGR (X: 383104 Y: 432566)

Area 5100m²

Current Access Site is accessed via Accrington Road to the north and Pomfret

Street to the east of the site

Topography The site comprises a grassed area that was previously occupied by terraced housing.

Surrounding Land Uses

The surrounding area comprises of residential properties and local amenities.

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3 Previous site investigation identified contamination

3.1 The original site investigation was undertaken in June 2015 and comprised the

advancement of four window sample boreholes, six trial pits (3 Tonne JCB

excavator). Soil samples from the excavations were screened for a range of potential

contaminants as per the findings of the Phase I Desk Study.

3.2 During the original site investigations the soil contamination results were assessed

against Atkins Atrisk 1% SOM and LQM/CEIH Suitable for Use Levels (S4UL) values

for a residential with plant uptake end use. Elevated concentrations of Naphthalene

Benzo(a)anthracene, Benzo(b)fluoranthene, Benzo(a)pyrene and

Dibenzo(ah)anthracene have been noted within the made ground materials.

Additionally Asbestos as chrysotile loose fibres has been observed at sample

position WS3.

3.3 Ground gas monitoring was undertaken via three gas well installations within window

sample positions WS2, WS3 and WS4. During the monitoring period an elevated

concentration of ground gas were noted at WS2 (CO² at >5%); based on the

readings taken and using CIRIA C665, their concentrations resulted in an Amber 1

Classification. An Amber 1 Classification requires the development to include a

suitable gas membrane and ventilated subfloor void.

3.4 Statistical analysis has revealed site wide Benzo(a)anthracene,

Benzo(b)fluoranthene, Benzo(a)pyrene and Dibenzo(ah)anthracene contamination.

Asbestos as chrysotile loose fibres was identified at WS3 (0.50 - 0.80m bgl), with a

quantification value of 0.001% at WS3.

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4 Remediation Strategy

4.1 Areas of concern are noted across the site due to Ground Gases, PAH’s and

Asbestos contamination.

4.2 The applicable pathways by which these contaminants could impact human health

receptors include direct contact, ingestion, asphyxiation and inhalation pathways.

Given that the site is to be developed into residential housing, there is potential that

this area of contamination could impact human health receptors following

redevelopment by the above pathways.

4.3 In order to protect human health receptors from identified contaminants, a 600mm

site strip is proposed within all garden/landscaped areas of the site as per Sutcliffe

Drawing 27759 – 703 (Appendix A). Following the proposed strip, a 600mm capping

layer consisting of ‘clean’ imported tested material will be placed within all

garden/landscaped areas to act as a barrier to contamination below 600mm, with

hardcover protecting the remainder of the site.

4.4 The area of asbestos contamination observed around the area of WS3 will require

excavation to accommodate the foundation construction as it is directly within the

footprint of plots 14 and 15 (27759 – 702). The quantification value for the asbestos

at WS3 was noted to be 0.001% and it was not observed within any of the other

sampled location. The Environment Agency hazardous waste WM2 technical

guidance document lists waste that contains known carcinogenic substances at

concentrations of ≥0.1% as being hazardous (H7 Carcinogenic). Using the WM2

document as a guide, the asbestos content found within WS3 0.50-0.80m is not

considered to pose a significant risk to human health. However as an additional

precaution the excavation works in the area of WS3 (8m diameter suggested) will

need to be undertaken with relevant contractors Risk Assessments and Method

Statements for removal of asbestos impacted ground. If material is to be disposed of

offsite it will require removal with the quantification value communicated to the waste

disposal and haulage contractor.

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4.4 Upon completion of required excavations, removed material will then be replaced

with 600mm of clean imported tested material in these areas therefore breaking the

source-pathway-receptor linkages. Depth testing will be undertaken once clean

material is placed in position to ensure the capping layer has been incorporated as

specified. Photographic evidence of the made ground removal will be taken to show

that the contaminated material has been removed from the site and photos

evidencing the underlying geotextile membrane will also be provided.

4.5 Any future workers that will potentially come into contact with contaminants are to be

provided with a copy of this report and instructed on limiting exposure and mitigating

risk. This is particularly relevant with the possible exposure to service workers

working below the 600mm capping layer, any service entry points and service

trenches should be backfilled with clean material.

Source Pathway Receptor Linkage

PAH’s

• Inhalation

• Ingestion

• Direct contact

• Wind blown dust

• End uses

• Construction Maintenance Workers

• Wider environment (adjacent property and land users) via wind blown dust

A 600mm site strip is proposed within all garden/landscaped areas of the site. Following the proposed strip, a 600mm capping layer consisting of ‘clean’ imported tested material will be placed within all garden/landscaped areas to act as a barrier to contamination below 600mm, with hardcover protecting the remainder of the site. This will break existing source-pathway-receptor linkages.

Asbestos

• Inhalation

• Ingestion

• Direct contact

• Wind blown dust

• End uses

• Construction Maintenance Workers

• Wider environment (adjacent property and land users) via wind blown dust

The excavation works in the area of WS3 (8m diameter suggested) will need to be undertaken with relevant contractors Risk Assessments and Method Statements for removal of asbestos impacted ground. If material is to be disposed of offsite it will require removal with the quantification value communicated to the waste disposal and haulage contractor. The footprint of the proposed plots (14 and 15) shall then act as a barrier to any potential asbestos contamination below, breaking existing source-pathway receptor-linkages.

Gas • Inhalation • End users

• Buildings

Using CIRIA C665 gas protection measures are required to an Amber 1 specification.

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5 Validation Sampling Strategy

5.1 Validation will consist of two elements:

(i) Assessment that remediation has removed any contaminants from the soil

which are required by the remediation plan

and / or

(ii) Assessment to determine that remediation has broken contaminant migration

and exposure pathways as designed

5.2 With respect to (i) above, excavation photos of the site strip in garden and

landscaped areas shall be provided showing a minimum 600mm excavation.

5.3 With respect to (ii) above, a “before and after” assessment of the site will be

conducted to ensure that a capping layer has been created to the specified 600mm in

garden/landscaped areas, including 150mm of topsoil in the garden areas to act as a

growing medium. No material will be placed on site unless it has been validated by

Sutcliffe Investigations and the area to be covered has been confirmed. If any

contamination is encountered within the new imported material then this will not be

suitable for use on site.

5.4 Gas protection measures will consist of a Protech GM + or similar gas protection

barrier that will be validated by Sutcliffe/ local building control and integrity tested by

the manufacturer and installer.

Sutcliffe will make regular visits to inspect the gas protection barrier. It is the

contractor’s responsibility to ensure that Sutcliffe are informed when gas membrane

installation is progressing and allowed sufficient time to validate.

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6 Further Considerations

6.1 Health and Safety - Construction Workers

6.1.1 The levels of contamination observed in the soil analysis indicated that a low to high

transient health risk for construction workers and the general public will arise from

exposure to, or inhalation of airborne dust generated by construction activities, or

from direct contact with site soils. Special precautions will be required while

conducting work in this area. Contractors personnel engaged in groundwork’s should,

as a matter of course, be counselled in good practice with particular regard to the

avoidance of dust inhalation and skin contact with soils. Smoking or eating on the

immediate worksite should be avoided and the importance of washing after contact

with soils or plant operating on the site should be given due consideration.

Furthermore, for protection of workers and the general public, contractors would

need to adopt effective dust suppression measures including inter alias:

• Water spraying in dry weather conditions

• Sheeting of lorries transporting site soils

6.1.2 For more specific detail please consult the detailed method statements from the

contractor.

6.2 Site Variations

6.2.1 Sutcliffe Investigations will be employed in the capacity of a watching brief during the

development of the site. During the remediation works Sutcliffe Investigations will

make site visits to ensure works are being carried out in accordance with the

remediation strategy, if during those visits or during any other times any areas of

concern are noted i.e visual/olfactory evidence then Sutcliffe Investigations are to be

informed immediately and all works should stop on site.

6.2.2 If further areas of concern are noted a site visit will be arranged (with Burnley

Borough Council if required) and further testing will be required. All works are to stop

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on site until a full investigation has been completed and submitted to Bury Council for

their approval.

Capping Layer Material

6.2.3 The capping layer in the garden/landscaped areas is to be at a minimum of 600mm

or to natural material. Should any imported material exceed the SSAC value (set for

this site) it will not be suitable for use on site and new material will have to be

obtained. Importation records will be required as well as consignment slips

documenting the importation of any material as these will need to be included in the

final remediation validation report. All waste material movements on/off site should

be recorded by the relevant contractor in a site materials management plan.

Capping Layer Thickness

6.2.4 Recorded measurements of the capping layer thickness for the garden areas will be

notified to all parties as well as areas where the capping layer does not meet the

required standard. Areas not meeting the required depth standard will need to be

made up to requisite depth with further depth verification measurement undertaken

before the finial validation of the project.

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7 Proposed Validation Process

7.1 Capping System - Sampling Strategy Imported Material

7.1.1 Validation samples will be tested for the standard suite as used in the Phase II report

submitted for this site. This will include a suite of metals, speciated PAH, speciated

TPH, BTEX and Asbestos. Results will be assessed against Tier One Screening

values for a residential with plant uptake end scenario.

Verification testing

Remediation / Verification Area

Remediation / Verification

Number of samples Testing

Garden/Landscaped Areas

600mm Cover System

2 at source and 5 on site Metals, TPH, PAH,

Asbestos

7.2.2 Although final site levels are currently unknown a requirement exists for one sample

being taken per 50m3 of imported topsoil and a minimum of 3 samples. No material is

to be sourced from recycled material.

7.2.3 All samples will be analysed by a MCERTS/UKAS accredited soil laboratory. All

sampling procedures at Sutcliffe Investigations are as a matter of standard taken in

accordance with BS 10175: 2011 “Investigation of Potentially Contaminated sites –

Code of Practice” and BS 10381: 2002 (Part 1, 2 and 5) with sulphate testing in

accordance with BRE Special Digest “Concrete in Aggressive Ground, Part 1:

Assessing the Aggressive Chemical Environment, 2001” and trial pits and bore holes

completed in accordance with BS 5930: 2015 & A2 “2010” – “Code of Practice for

Site Investigations”.

7.2.4 The cover system adopted for this site is based upon:

‘Cover systems for land regeneration – thickness of cover systems for contaminated

land’ programme designed by RSK ENSR Limited, on behalf of the Association of

Geo-technical and Geoenvironmental Specialists, in partnership with BRE and

funded by the Department of Trade and Industry to reduce the risk of exposure to the

contaminant.

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The other design considerations, which need to be taken into account, are:

• Material used for cover system - A good quality cover should be used

incorporating a topsoil layer, ideally at least 150mm thick or 30% of the cover,

whichever is greater. Reference should be made to the Specification for

Topsoil, BS 3882:1994.

• Treatment of underlying ground - The ground should be suitably compacted

prior to the placement of the cover system (as set out in CIRIA SP 105). This

will inhibit root penetration, infiltration, burrowing animals and instability but

should not be allowed to induce water logging.

• Provision of capillary break layer – The provision of a capillary break layer

would control the upward movement of dissolved and/or mobile contaminants

during dry weather. It would also reduce the degree of inter-mixing of the soils

and so provide an additional factor of safety.

• Provision of physical barrier at base of cover system or visual marker – The

provision of a physical barrier or visual marker would discourage excavation

below cover system and again reduce the degree of intermixing of the soils.

This may be provided using a synthetic material (e.g. geogrid or geotextile) or

compacted granular free draining material. The geotextile or the compacted

layer would also reduce root penetration. Compacted granular free draining

material will be adopted as the physical barrier layer.

• The material adopted for the capillary break layer will be quarried material,

50mm single size stone.

• The sub-soil 1 material will have 3 no. samples on site.

Topsoil Number of samples Testing

On site 1 sample per 50m³

(With a minimum of 3 taken)

Metals, PAH, TPH Speciated, BTEX

and Asbestos (as a minimum)

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150mm Imported Topsoil

300mm clean inert

Subsoil (sand)

150mm free draining

Compacted c lean

Single size stone

A ll imported material is to be tested prior to importing

to site and once on site . Depth testing is to be undertaken once

materia l is p laced.

Typical Section Through Capping Layer

Geotextile M embrane

Further Verification

7.3.1 Photographic Evidence

7.3.1.1 Photographic evidence will be undertaken to show the 600mm of material has been

removed from garden areas or excavations have been undertaken to the natural

material on site, photographic evidence of the asbestos contaminated made ground

removal shall also be required. These photographs will be referenced and provided in

digital format for inclusion in the Completion/Validation report.

7.3.2 Surveys

7.3.2.1 Once the capping layers has been completed in the garden/landscaped areas the

contractor will undertake a level survey, to show that the required material has been

brought onto site, this will need to be referenced to the original and proposed ground

survey.

7.3.2.2 Once the imported material has been brought onto site and the validation testing has

been shown to be acceptable, 3 No. probe holes by hand auger will be carried out to

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confirm that 600mm of material is present in the landscaped areas. Photographic

evidence will be taken showing a staff or tape measurement.

8 Reporting

8.1 Sutcliffe Investigations will issue a full written Completion/Validation report upon

completion of the remediation strategy, with all aspects of the above work included to

Burnley Borough Council for final removal of planning conditions. The validation

report will be prepared in line with the guidance set out in CLR 11. This will contain

the following details:

• Details of clean fill materials imported, together with analysis results

• Any hot spots, unexpected discoveries and additional sampling results

• Remediation certificate

• Status at completion

• Final extent of works

• Quality management systems

• Verification of works undertaken

• Local Authority Remediation Approval

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9 Third Party Consultations

9.1 Local Authority approval of the remediation and validation strategy will need to be

gained prior to commencement of works on site.

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Prepared by: 14th December 2015 Date: S Robinson BEng (Hons) BA (Hons) Environmental Scientist Reviewed by: 14th December 2015 Date: W G Baldwin BEng (Hons) CEng MIStructE AIEMA Director

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Appendix A – Site Investigation Plan

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18-20 Harrington Street, Liverpool L2 9QA

t: 0151 227 3155 f: 0151 227 3156

e: sutcliffe@sutcliffe.co.uk w: www.sutcliffe.co.uk

Date Revision suffix

Scale at A3

Drawn by

Drawing title

Client

Project

Drawing number

DO NOT SCALE OFF THIS DRAWING

GENERAL NOTES

This drawing to read in conjunction with all relevant

structural and architectural drawings and specifications.

All dimensions to be checked on site by the contractor /

fabricator prior to commencement of works.

All dimensions are in millimetres unless stated otherwise.

All works to be carried out in strict accordance with the

engineer's specifications, relevant British Standards and

where applicable Local Authorities requirements.

For final setting out information relating to grid lines and wall

positions refer to the architect's drawings.

Description

PRELIMINARY DRAWING

Rev Date Checked By

RW15.12.15 PRELIMINARY ISSUEP1 SR

CALICO HOMES

DUCKETT STREET

BURNLEY

SITE INVESTIGATION

ON PROPOSED

SITE PLAN

1:500

R.WELSH

15.12.15

27759-702

P1

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Appendix B – Proposed Remediation / Validation Sampling Strategy

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18-20 Harrington Street, Liverpool L2 9QA

t: 0151 227 3155 f: 0151 227 3156

e: sutcliffe@sutcliffe.co.uk w: www.sutcliffe.co.uk

Date Revision suffix

Scale at A3

Drawn by

Drawing title

Client

Project

Drawing number

DO NOT SCALE OFF THIS DRAWING

GENERAL NOTES

This drawing to read in conjunction with all relevant

structural and architectural drawings and specifications.

All dimensions to be checked on site by the contractor /

fabricator prior to commencement of works.

All dimensions are in millimetres unless stated otherwise.

All works to be carried out in strict accordance with the

engineer's specifications, relevant British Standards and

where applicable Local Authorities requirements.

For final setting out information relating to grid lines and wall

positions refer to the architect's drawings.

Description

PRELIMINARY DRAWING

Rev Date Checked By

RW15.12.15 PRELIMINARY ISSUEP1 SR

CALICO HOMES

DUCKETT STREET

BURNLEY

REMEDIATION & VALIDATION

PLAN ON PROPOSED

SITE PLAN

1:500

R.WELSH

15.12.15

27759-703

P1