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Phase III Remediation & Validation Proposals at Duckett Street, Burnley
Client: Calico Homes Our ref: LG27759
Date: Dec 2015
LG 27759
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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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18-20 Harrington Street, Liverpool L2 9QA
t: 0151 227 3155 f: 0151 227 3156
e: [email protected] 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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18-20 Harrington Street, Liverpool L2 9QA
t: 0151 227 3155 f: 0151 227 3156
e: [email protected] 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