Risk Assessment UKOP Replacement of Overhead 28.04.2020 Crossing at Fishers Green 817270-H-MIS-045 Revision 1
Revision: Date: Issued for: By: Checked by: Approved by: 0 22.04.2020 Review Ken Garstang 1 28.04.2020 Issued for planning Ken Garstang Gary Porter Gary Porter
Prepared by: Checked by: Approved by: Name: Ken Garstang Name: Gary Porter Name: Gary Porter Position: Senior Engineer Position: Project Manager Position: Project Manager Date: 28.04.2020 Date: 28.04.2020 Date: 28.04.2020 Signature: Signature Signature: UKOP Contents 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green
Page 3 1 Introduction 4
2 Scope 5
3 Preliminary Risk Assessment 6
3.1 Previous Land Uses 6 3.2 Potential Contaminants 7 3.3 Conceptual Model 8 3.4 Potentially Unacceptable Risks 8 3.5 Design Risk Register 8
4 Site Investigation Scheme and Verification Plan 9
Appendix 1 Preliminary Risk Assessment ...... 10 Appendix 2 Design Risk Register ...... 11 Appendix 3 Verification Plan...... 12 UKOP 1 Introduction 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green The 350mm NB Thames to Buncefield pipeline currently crosses the R Lea at Page 4 Fishers Green via an overhead crossing. The pipeline transports refined petroleum products.
Regulations 15 of the Pipeline Safety Regulation 1996 places a duty on the pipeline operator to ensure that:
“No person shall cause such damage to a pipeline as may give rise to a danger to persons.”
Thus, in addition to maintaining restricted public access to above ground crossings, the company must ensure as far as is practicable that the pipelines are protected from damage by third party interference thereby minimising or eliminating the risk they pose to the public.
The accessibility of the above ground crossing at Fishers Green elevates the risk of damage to the pipeline by third party interference, and injury to the general public, with a possible breach of containment leading to fire and/or environmental pollution. The risk of pollution is heightened since the crossing is above a waterway.
Over the last few years oil pipeline networks within the UK have been the victim of product theft by way of illegal pipeline tappings, with the UKOP pipeline at Fishers Green being the location of one such tapping.
Therefore, in order to increase the security of the pipeline system, BPA intend to replace the overhead crossing at Fishers Green with a buried section of pipeline.
Construction of the new section of pipeline will commence in 2020. The new section of pipeline is to be tied in to the existing pipeline during a pipeline shutdown period, the date of which has yet to be finalised.
Following re-commissioning of the pipeline, the existing overhead crossing and the redundant buried section of pipeline to the east of the crossing will be removed. The redundant section of pipeline to the west of the crossing will be capped and filled with grout.
Note: this document has been produced to address the planning conditions contained in Planning Decision Notice EPF/0857/17 (see Appendix 1), in particular condition 3, and is included in the documentation to be submitted in support of a new planning application. UKOP 2 Scope 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green Planning Decision Notice EPF/0857/17 Condition 3 states the following: Page 5 No development approved by this planning permission shall take place until a scheme that includes the following components to deal with the risks associated with contamination of the site shall each be submitted to and approved in writing by the Local Planning Authority:
1. A preliminary risk assessment which has identified All previous uses Potential contaminants associated with those uses A conceptual model of the site indicating sources, pathways and receptors and Potentially unacceptable risks arising from contamination at the site
2. A site investigation scheme based on (1) to provide information for a detailed assessment of the risks to all receptors that may be affected, including those off site.
3. The results of the site investigation and the detailed risk assessment in (2) and, based on these, an options appraisal and remediation strategy giving full details of the remediation measures required and how they will be undertaken.
4. A verification plan providing details of the data that will be collected in order to demonstrate that the works set out in the remediation and mitigation strategy in (1) are complete and identify any requirements for longer-term monitoring of pollutant linkages, maintenance and arrangement for contingency action.
This document addresses the above requirements. UKOP 3 Preliminary Risk Assessment 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green A Preliminary Risk Assessment is contained in the Geo-environmental Site Page 6 Assessment document ref 1921133 R01 (00) Section 3. It includes previous land uses, potential contaminants, a conceptual model and potentially unacceptable risks.
The Preliminary Risk Assessment is included for reference in Appendix 1.
3.1 PREVIOUS LAND USES
Previous land uses are detailed in the Geo-environmental Site Assessment Section 3.5. The following table summarising previous land uses.
Date Land use/features on site Land use/features in vicinity of site (of relevance to the assessment)
1884 – 1897 The River Lea runs directly Fishers Green Farm is located through the middle of the 50m to the east of the site and site. Cornmill and Horsemill comprises of a residential farm Stream flow around house and outbuildings Paynes Island. surrounded by fields. Hooksmarsh Bridge Woodland is present 50m to crosses the River Lea to the south west of the site the Boat House on the where Watch and Barrel west side of the site. Houses are located. These structures are associated with Fishers Green Farm is a Royal Gunpowder Factory situated on the east side of situated 700m to the south of the site as open land. the site. An embankment is present along the River Lea 120m south west of the site. The River Lea meanders 100m north of the site.
1897 – 1898 A boat house is identified Two buildings were identified on the south west corner of at 110m and 240m south west the site on the River Lea of the site on the floodplain between the River Lea and Cornmill Stream. The Dining Room building is also located 60m south west of the site along Cornmill Stream. The River Lea and Fishers Green are now covered by less forests.
1898 – No historical maps are available in these dates 1970s UKOP Date Land use/features on site Land use/features in vicinity 28.04.2020 of site (of relevance to the 817270-H-MIS-045 assessment) Revision 1
Replacement of Overhead 1972 – 1987 A pipeline has now been Two drains are located on the Crossing at Fishers Green identified across the River floodplain between Horsemill Lea, north of Hooksmarsh and Cornmill Streams, 200m Page 7 Bridge. and 20m south west of the site. The land on this flood plain A drain is situated to the 200m south of the site north of the Fishers Green (formerly occupied by Royal Lane. Gunpowder Factory facilities) Two ponds are located in has now been identified as a the field near Fisher Green Government Research Farm on the east side of Establishment. the site. A number of nitro-glycerine hills A path, separating (the remnants of gunpowder Horsemill Stream and making history) are present to Hooksmarsh, with the south east of the site, with embankments on either the closest structure 120m to side extends west of the the south east. site. A few large surface water Horsemill Stream has been features such as ponds and straightened and widened. lakes are located 120m and 10m north of the site. Hooksmarsh is located north west of the site. A nursery with a complex of greenhouses is located 240m to the north east.
1987 – 1992 A car park is situated in the The River Lea was subject to middle of the site to the straightening 100m north of west of Hooksmarsh the site. A lake was separated Bridge into two smaller lakes. The ponds to the east of Cornmill Stream are no longer present.
1992 – No change to the site and surrounding area present
3.2 POTENTIAL CONTAMINANTS
Potential contaminants are detailed in the Geo-environmental Site Assessment Section 3.8.1.
Briefly, the contaminants identified are:
Hydrocarbons from the pipeline. Gunpowder (historically from the Royal Gunpowder Mills). Contaminated ground (from the historic landfill site to the south of Fishers Green Lane. UKOP 3.3 CONCEPTUAL MODEL 28.04.2020 817270-H-MIS-045 A conceptual model is detailed in the Geo-environmental Site Assessment Section Revision 1 3.8
Replacement of Overhead 3.4 POTENTIALLY UNACCEPTABLE RISKS Crossing at Fishers Green Potential contaminants are detailed in the Geo-environmental Site Assessment Page 8 Section 3.8.4.
This identifies the above ground section of pipeline as providing the highest risk of potential contamination. Removing this section reduces the risk from high to low.
Reference is also made to potential contamination from the historic landfill site to the south of Fishers Green Lane where excavation works will take place. The construction contractor will be specifically required to address the potential for contaminated ground within his Environmental Management Plan, method statements and risk assessments.
The site was used for industrial (inert) fill between 1974 and 1976.
3.5 DESIGN RISK REGISTER
A Design Risk Register (document 817270-H-MIS-017) has been produced for the construction works which addresses, inter alia, environmental risks. The register is included for reference in Appendix 2. UKOP 4 Site Investigation Scheme and Verification Plan 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green Site investigations were undertaken in 2017 with the drilling of 3 boreholes. Page 9 Groundwater levels and quality were recorded and the investigation strategy and results are contained in the Geo-environmental Site Assessment Sections 5 and 6.
A Verification Plan (document ref 11921133 R02 (00)) has been produced for monitoring groundwater quality before, during and subsequent to the construction works, involving the drilling of 4 additional boreholes.
The Verification Plan is included for reference in Appendix 3. UKOP Appendix 1 Preliminary Risk Assessment 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green
Page 10
UKOP Appendix 2 Design Risk Register 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green
Page 11 Design Risk Register Replacement of Overhead Crossing at Fisher's Green 817270-H-MIS-017 Rev 0
Design & Construction Risk Register (information)
Likelihood Categories Severity Categories
Health, Safety & Environment Risks during Construction Score Descriptor Description Score and Operational Life
Minor injuries / inconveniences, operative can continue work 1 Improbable about 1 in 1000 1 Short term local damage
Minor injuries / First Aid Treatment, stops work 2 Remote about 1 in 100 2 Medium term local / short term regional damage
Reportable / Lost time injury or illness 3 Occasional about 1 in 10 3 Long term local / regional damage
Major injury or illness with long term effects 4 Probable more likely to happen than not 4 Long term widespread damage
Fatalities 5 Frequent expect it to happen 5 Widespread permanent damage
Risk Mitigation & Management
Risk Level Construction Risk Operational Risk
Check that no further risks can be eliminated by modifications of design. Seek alternative and assess cost to benefit of mitigation measures in Low Proceed with design. relation to severity of risk.
Consider alternative design or construction method. Disseminate risk assessment information to affected stakeholders and third Medium If alternatives are not available, specify precautions to be adopted. parties as appropriate. List Residual Hazards in risk register and H&S Plan. List Residual Hazards in risk register and H&S File.
Seek alternative solutions. Disseminate risk assessment information to senior management, affected If alternatives are not available, specify precautions to be adopted and High stake holders and third parties as appropriate. advise senior management and Planning Supervisor (where applicable). List Residual Hazards in risk register and H&S File. List Residual Hazards in risk register and H&S Plan.
Risk Profile Severity Score Likelihood Score 1 2 3 4 5
5 H 4 ig h M e 3 d iu m 2 L o w 1
28/04/2020 Design Risk Register Replacement of Overhead Crossing at Fisher's Green 817270-H-MIS-017 Rev 0
Pre RCM Post RCM ) E (
) t S n r r ( Const'n Op'n Const'n Op'n e H&S Plan = P e e
Activity / Risk y n n m t Hazard Consequence Comments/Constraints Risk Risk Risk Control Measures in Design (RCM) Risk Risk Control of Residual Hazards H&S File = F e n w w
Element No. f
o Design = D O O a
r L/M/H L/M/H L/M/H L/M/H i S v n E 3rd party 1 E/S Buried services (1) Damage to service during excavation Failure of service resulting in H 3rd party service searches undertaken. M Contractor to confirm service services injury and/or environmental Information included in tender documents. location/depth prior to commencing damage works by cat scan and trial holing, and comply with HSG47 (Avoiding danger from buried services)
2 E/S Buried services (2) Damage to service when crossing Failure of service resulting in H 3rd party service searches undertaken. M Contractor to provide protection to with heavy construction plant injury and/or environmental Information included in tender documents. buried services at crossing points damage (bog mats or similar) Contractor to agree method of protection with service owner/operator 3 S Overhead services Cable strike when manoeuvering Failure of service resulting in H 3rd party service searches undertaken. M Contractor to erect goalposts and plant and equipment injury Information included in tender documents. bunting in compliance with GS6 (Avoidance of danger from overhead electric power lines) 4 S CP interference with 3rd party Protection to pipeline and 3rd party L Impact on CP considered during design - None services services compromised Environment Note: this Environment section should be read in conjunction with the following documents: 1) Flood Risk Assessment 133822-R1 (0) 2) Geo-environmental Site Assessment 1921133 R01 (00) 3) Ecological Constraints Survey 2480202 Rev 01 4) Verification Plan 1921133 R02 (00) 5 E Environmental issues Breach of legislation, prosecution Working areas are immediately H Environmental/ecological/flood risk surveys M Contractor to produce adjacent to Lee Valley Ramsar completed and included in tender documents. Environmental Management Plan Site and SPA, Turnford and Cheshunt SSSI and Waltham Abbey SSSI 6 E Disposal of water following Pollution to watercourses M Contractor responsibilities defined in tender L Method Statements and Risk hydrotest documents Assessments 7 E Contaminated ground Delays to programme Potential for contaminated ground M Likelihood of contaminated ground considered L Contractor to include potential for as works cross a historic landfill as part of geoenvironmental assessment contaminated ground in site Environmental Management Plan 8 E Flooding Delays to programme, pollution M Flood Risk Assessment completed and EA L Contractor to comply with permit obtained recommendations in Flood Risk Assessment and requirements in EA permit 9 E Groundwater pollution Delays to programme, pollution, M Verification Plan produced for ongoing L reduction in quality of Controlled monitoring of groundwater quality. Waters Watching brief by environmental engineer during tie in works 10 E Protected species Delays to programme M Ecological assessment undertaken during design - Contractor to comply with phase ecological requirements 11 E Invasive species Delays to programme M Ecological assessment undertaken during design - Contractor to comply with phase. Invasive species survey to be completed ecological requirements prior to works commencing on site 12 E Nesting birds Delays to programme M Design to include for minimum removal of L Contractor to comply with hedgerows. Ecologist to carry out surveys where ecological requirements hedgerows etc are to be removed during nesting season 13 E Air pollution Impact on third parties M Requirements for Health and Safety Plan and L Contractor to correctly service and Environmental Management Plan included in maintain plant and equipment tender documents 14 E Noise pollution Impact on third parties M Requirements for Health and Safety Plan and L Contractor to correctly service and Environmental Management Plan included in maintain plant and equipment tender documents Acoustic barriers to be provided where appropriate 15 E Fuel spillages Ground contamination and/or water M Requirements for Health and Safety Plan and L Contractor to include mitigation pollution Environmental Management Plan included in measures within Health and Safety tender documents Plan (e.g. double skinned bowsers, drip trays, availability of spill kits)
Consents 16 - Consents Failure to obtain consents resulting in M Agent employed to ensure all consents are L Contractor to ensure adherence to delays to the construction programme obtained in a timely manner consents requirements 17 - Access Failure to gain access resulting in M Agent employed to ensure all accesses are L Liaison with landowners and delays to the construction programme obtained in a timely manner tenants throughout design and construction period
28/04/2020 2 of 6 Design Risk Register Replacement of Overhead Crossing at Fisher's Green 817270-H-MIS-017 Rev 0
Pre RCM Post RCM ) E (
) t S n r r ( Const'n Op'n Const'n Op'n e H&S Plan = P e e
Activity / Risk y n n m t Hazard Consequence Comments/Constraints Risk Risk Risk Control Measures in Design (RCM) Risk Risk Control of Residual Hazards H&S File = F e n w w
Element No. f
o Design = D O O a
r L/M/H L/M/H L/M/H L/M/H i S v n E Materials 18 S Manufacturing defects FailureDamage of to materials service during in service, excavation loss of M Linepipe and bends specified to project/ L Materials to be inspected when containment national/international specifications received on site 19 S Coating damage Corrosion, loss of containment M Linepipe and bends specified with external L Method statements to address coating to National Grid Spec T/SP/CW/6 handling of pipe during construction to prevent coating damage
20 S Corrosion Loss of containment M Linepipe and bends specified with external L Method statements to address coating to National Grid Spec T/SP/CW/6 handling of pipe during construction to prevent coating damage
21 S Hazardous materials Health risk H ITT references requirement for COSHH L Contractor to make available on site assessments to be held on site for all materials COSHH Assessments for all used in construction of the works permanent and temporary materials used during construction. Tool box talks to be held with workforce
Construction 22 S Construction accidents/incidents Personnel injury/fatality. M Design based on proven construction techniques L Method Statements and Risk Damage to plant and equipment Assessments. Contractor to demonstrate competence of workforce. Project Manager can ask for personnel to be re-alocated to other tasks if competence is questioned
23 S Construction damage Damage to plant and equipment M Design based on proven construction techniques L Method Statements and Risk and/or 3rd party property Assessments. Contractor to demonstrate competence of workforce. Project Manager can ask for personnel to be re-alocated to other tasks if competence is questioned
24 S Unforseen ground conditions Delays to programme M Geotechnical investigations undertaken and L None results included in tender documents 25 S Excavation/trench collapse Personnel injury/fatality M Proposed construction methodolgy (guided L Method Statements and Risk augerbore) requires deep drive and reception Assessments to include pits. Tender documents include requirements for assessment of excavation/trench working in, and adjacent to, deep excavtions stability. Contractor to provide (confined space working/training, working at appropriate support to heights, barrier/fencing requirements, temporary excavations/trenches (e.g. sheet works design etc) piling, trench boxes) Cotractor to provide temporary works design for piled pits etc 26 S Weather Delays to construction programme M ITT to include requirement for tender L Contractor to provide appropriate due to adverse weather conditions, programmes to include for impact of bad weather weather protection (e.g. welding failure to meet shutdown window tents) to enable works to continue during periods of bad weather
27 S Hydrotest failure Uncontrolled release of high pressure M Test pressure calculations carried out L Method Statements and Risk water during testing Assessments. Exclusion zones to be established prior to pressurisation. Warning signs to be placed at appropriate locations. Suitably rated equipment to be used
28 S Failure to construct river crossing Failure to install trenchless crossing. H Site investigations undertaken to determine M Contractor to review results of site Extended programme, failure to meet ground conditions and depth of existing piles investigations and advise on shutdown window along river bank. Information included in tender sufficiency of information documents Contractor to submit detail design and supporting calculations
28/04/2020 3 of 6 Design Risk Register Replacement of Overhead Crossing at Fisher's Green 817270-H-MIS-017 Rev 0
Pre RCM Post RCM ) E (
) t S n r r ( Const'n Op'n Const'n Op'n e H&S Plan = P e e
Activity / Risk y n n m t Hazard Consequence Comments/Constraints Risk Risk Risk Control Measures in Design (RCM) Risk Risk Control of Residual Hazards H&S File = F e n w w
Element No. f
o Design = D O O a
r L/M/H L/M/H L/M/H L/M/H i S v n E 29 S Confined space working PersonnelDamage to injury/fatality service during excavation H Proposed construction methodolgy (guided M Method Statements and Risk augerbore) requires deep drive and reception Assessments pits. Tender documents include requirements for All personnel entering confined working in, and adjacent to, deep excavtions spaces to have appropriate training (confined space working/training, working at heights, barrier/fencing requirements, temporary works design etc) 30 S Working at heights Personnel injury/fatality H Proposed construction methodolgy (guided M Method Statements and Risk augerbore) requires deep drive and reception Assessments pits. Tender documents include requirements for All personnel to have appropriate working in, and adjacent to, deep excavtions training (confined space working/training, working at heights, barrier/fencing requirements, temporary works design etc) 31 Working close to/above water Personnel injury/fatality H Requirements for ompetency/training of work M Method Statements and Risk force referenced in tender documents Assessments All personnel to have appropriate training 32 S RTAs Construction personnel and/or 3rd M Traffic management requirements in L Contractor to produce detailed party injury/fatality Construction Management Plan included with Traffic Management Plan planning application and ITT 33 S Overstressing of tie-ins Failure of pipeline in service M Design includes for pipeline flexibility at tie-in L Method Statements and Risk locations Assessments 34 S Mud on roads RTAs Traffic management requirements in L Contractor to produce detailed Construction Management Plan included with Traffic Management Plan planning application and ITT 35 S Radiation exposure Personnel injury/fatality M Phased array inspection techniques to be used - None eliminating the use of ionising radiation 36 S Lifting operations Personnel injury/fatality H Design based on proven construction techniques L Method Statements and Risk Assessments. Lifting plans to be prepared for all lifting operations 37 S Fire or medical emergency Personnel injury/fatality H L Contractor to produce detailed Emergency Plan 38 S Transportation of plant and RTAs M Traffic management requirements in L Contractor to produce detailed materials to site Construction Management Plan included with Traffic Management Plan planning application and ITT 39 S Presence of product in pipeline Fuel spillage, ground contamination M M Line clearance procedures L L Works to be undertaken under when cutting existing line at tie-in BPA permit system. locations Pipeline to have under pressure tapping at each tie-in location and line dipped for presence of fuel. Gulley sucker to be available on site to remove product if present 40 S Presence of nitrogen in pipeline Nitrogen collects in excavations M M Tender documents specify use of gas detectors L L Works to be undertaken under when cutting existing line at tie-in resulting in asphyxiation and air movers during tie in works BPA permit system. locations Contractor to provide gas detectors and air movers during tie in works
41 S Electricity Personnel injury/fatality H Tender documents specify that only 110 v L Method Statements and Risk equipment is to be used on site Assessments. Only 110 v equipment to be used on site 42 S Exhaust fumes Fumes collect in excavations M L Parking of vehicles to be monitored resulting in asphyxiation and controlled during works. Vehicles not to be parked close to excavations
43 S/E 3rd party interference/damage Loss of containment H Project objective is to remove overhead crossing L Contractor to provide security of canal to reduce the risk of 3rd party thoughout construction period interference 44 S Injury to 3rd parties Working areas immediately adjacent Risk to 3rd parties highlighted in tender Contractor to provide security to public paths and car parks documents . throught construction period, Works to be sequenced such that public working areas to be appropriately accesses remain open wherever possible fenced
28/04/2020 4 of 6 Design Risk Register Replacement of Overhead Crossing at Fisher's Green 817270-H-MIS-017 Rev 0
Pre RCM Post RCM ) E (
) t S n r r ( Const'n Op'n Const'n Op'n e H&S Plan = P e e
Activity / Risk y n n m t Hazard Consequence Comments/Constraints Risk Risk Risk Control Measures in Design (RCM) Risk Risk Control of Residual Hazards H&S File = F e n w w
Element No. f
o Design = D O O a
r L/M/H L/M/H L/M/H L/M/H i S v n E 45 S 3rd party interference LossDamage of Plant to service or Materials during excavation M Risk of 3rd Parties gaining unlawful access to the L Contractor to provide security work areas / site establishment throught construction period, working areas and site establishment to be appropriately fenced Programme 46 - Programme overrun Failure to meet shutdown window M Provisional construction programme developed L Contractor to produce detailed during design construction programme
28/04/2020 5 of 6 Construction Risk Register Guidance
Notes 1 The Risk Assessment process is based on a two-dimensional scoring system of LIKELIHOOD and SEVERITY, both on a scale of 1-5. The two tables are used to assess the scores. 2 The 'traffic light' matrix is then used to plot the position of each identified risk and the risk zone (red / amber / green) in which it falls. 3 Reference is then made to the Risk Mitigation and Management Table to determine the course of action to be taken for both CONSTRUCTION and OPERATION. 4 The lower portion of the Risk Register covers other areas of construction work which may or may not be covered by local legislation. 5 Every row of the Risk Register should be considered and project hazards should be entered in Column E. Columns C and D can be completed to give each hazard an identification code and to differentiate between SAFETY and ENVIRONMENTAL hazards.
7 Each row of the Risk Register is then addressed in turn, working from left to right. Enter at Columns J & K (at the pre- 'risk control measures in design' (RCM) stage) the risk ranking decision (L=low, M=medium, H=high) for CONSTRUCTION and OPERATION, where applicable. 8 Column L is used to record design decisions that mitigate or eliminate the risk, and Columns N and O record the resulting (reduced) risk ranking (L, M or H). 9 Columns P, Q and R set out what can be done to manage the residual risk during construction and operation, allocate a risk owner and state where the relevant risk information is stored. This document can also be used to hand over from a FEED (front- end engineering design) completion to a different designer for the detail design stage.
10 Consider additional risks not listed that are specific to the project, and add rows to the spreadsheet as required. 11 The Risk Register must have a designated Owner to be responsible for the overall risk management process. Project NAME and OWNER details can be entered in the RISK REGISTER SHEET page header and footer (File menu > Page Setup) 12 This Construction Risk Register should be regularly updated and stored in the Project Health & Safety Plan. 13 The Contractor or Performing Authority shall be made aware of the content of this Risk Register to support the preparation of Method Statements and detailed task risk assessments. UKOP Appendix 3 Verification Plan 28.04.2020 817270-H-MIS-045 Revision 1
Replacement of Overhead Crossing at Fishers Green
Page 12
British Pipeline Agency (BPA) Land off Fishers Green Lane, Cheshunt, EN9 2ED
Verification Plan
Project no. 1921133- R02 (00)
MARCH 2020
RSK GENERAL NOTES
Project No.: 1921133 R02 (00)
Title: Verification Plan: Land off Fishers Green Lane, Cheshunt, EN9 2ED
Client: British Pipeline Agency, 5-7 Alexandra Road, Hemel Hempstead, Hertfordshire, HP2 5BS
Date: March 2020
Office: RSK, 18 Frogmore Road, Hemel Hempstead, Hertfordshire, HP3 9RT, tel.: 01442 437500, contact: Alena Landers
Status: Final
Author Alena Landers Technical reviewer David Anchor
Signature Signature Date: March 2020 Date: March 2020
Project manager Alena Landers Quality reviewer Samantha Gower
Signature Signature Date: March 2020 Date: March 2020
RSK Environment Limited (RSK) has prepared this report for the sole use of the client, showing reasonable skill and care, for the intended purposes as stated in the agreement under which this work was completed. The report may not be relied upon by any other party without the express agreement of the client and RSK. No other warranty, expressed or implied, is made as to the professional advice included in this report. Where any data supplied by the client or from other sources have been used, it has been assumed that the information is correct. No responsibility can be accepted by RSK for inaccuracies in the data supplied by any other party. The conclusions and recommendations in this report are based on the assumption that all relevant information has been supplied by those bodies from whom it was requested. No part of this report may be copied or duplicated without the express permission of RSK and the party for whom it was prepared. Where field investigations have been carried out, these have been restricted to a level of detail required to achieve the stated objectives of the work. This work has been undertaken in accordance with the quality management system of RSK Environment Ltd.
CONTENTS
1 INTRODUCTION ...... 1 1.1 Background ...... 1 1.2 Objective ...... 1 1.3 Previous investigations ...... 2 1.4 Limitations ...... 3 2 THE SITE ...... 4 2.1 Site location and description ...... 4 3 PROPOSED VERIFICATION WORKS ...... 5 3.1 Groundwater and surface water monitoring ...... 5 3.1.1 Sampling locations ...... 5 3.1.2 Monitoring frequency ...... 6 3.1.3 Sampling methodology and In-situ testing ...... 7 3.1.4 Chemical testing ...... 7 3.1.5 Reporting of monitoring results ...... 7 3.2 Watching brief ...... 8 3.3 Borehole Decommissioning ...... 8 4 ARRANGEMENTS FOR CONTINGENCY ACTION ...... 10
TABLES Table 1: Site setting ...... 4 Table 2: Construction milestones and proposed monitoring ...... 6
FIGURES Figure 1 Site location plan Figure 2 Groundwater/surface water verification sampling locations
APPENDICES Appendix A Service constraints Appendix B Planning permission including the summary of conditions Appendix C Correspondence
British Pipeline Agency i Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED Project No. 1921133 R02 (00)
1 INTRODUCTION
RSK Environment Limited (RSK) was commissioned by the British Pipeline Agency (BPA) to monitor and verify the works associated with the removal of the existing pipeline bridge and its re-routing underneath the Lee Valley Flood relief channel and the River Lee, off Fishers Green Lane, Cheshunt.
This report is subject to the RSK service constraints given in Appendix A.
1.1 Background
The pipeline comprises of a single 350 mm diameter pipe transporting hydrocarbons between Epping Booster Station and Hemel Junction.
BPA proposed to change the existing section of above-ground pipeline to a below- ground section to eliminate the following identified hazards:
• Deliberate and malicious acts of sabotage; and
• Accidental damage by a third party.
There is no boat traffic on the stretch of the River Lee in the site area and therefore the risk from the pipeline damage caused by boat traffic is low.
A full planning permission was previously granted for the works by Epping Forest District Council (ref: PL/EPF/0857/17) with several conditions that needed to be satisfied. The planning permission granted in 2017 is now lapsed, and this report is prepared to support a new planning application.
This verification plan is likely required for monitoring of the proposed construction works. The plan needs to be agreed by the Local Planning Authority (LPA) and the Environment Agency (EA) before the construction works commence.
The Environment Agency was consulted in 2017 on the main elements of this report, including the location and construction details of monitoring boreholes. The relevant correspondence is included in the Appendix C.
1.2 Objective
The objective of this verification plan report is to address the requirement for the following information:
British Pipeline Agency 1 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
• Details of data that will be collected in order to demonstrate that the construction works do not cause a reduction in quality of Controlled Waters; • Identify any requirements for long-term monitoring of pollutant linkages; and
• Maintenance and arrangements for contingency action.
1.3 Previous investigations
RSK has previously undertaken a geo-environmental site assessment, which has been reported in RSK Geo-Environmental Site Assessment report (ref: 28841 R01), which was recently reappraised under ref 1921133 R01(00) in March 2020. The works included a site walkover conducted on 13th December 2016, a PRA study (all previous uses, potential contaminants associated with the identified uses, an initial conceptual model and potential unacceptable risks) and a subsequent intrusive investigation between 11th and 18th January 2017. Groundwater monitoring was completed on 1st February 2017 along with a geophysical survey to confirm the depth of the sheet pile walls along Horsemill and Cornmilll Streams.
During the site walkover the fuel pipeline was noted to be a potential source of contamination, however, the pipeline system is operated and maintained to a high standard and so it is considered unlikely for an incident or release of hydrocarbons to occur. No other potentially significant ground contamination issues were identified at the time of the site walkover.
The intrusive investigation conducted by RSK in January 2017 included drilling of 3 no. cable percussive boreholes (BH01, BH02 and BH03) advanced to 20 m bgl, which were installed as groundwater monitoring wells, and subsequent round of groundwater monitoring.
The exploratory holes revealed that the site is underlain by a variable thickness of made ground over Alluvium and River Terrace Deposits with the London Clay Formation over the Lambeth Group encountered at depth. In addition, Harwich Formation comprising a thin layer of sand was encountered at the base of the London Clay Formation.
The made ground encountered in the most eastern borehole (BH03) comprises the fill materials deposited on the site during the landfill operations between the 1950’s and 1970’s.
The exploratory boreholes further revealed that the maximum thickness of the River Terrace Deposits of 6.3 m was encountered in borehole BH02, situated next to Cornmill Stream. The thickness of the River Terrace Deposits in borehole BH03, situated approximately 20 m to the east of borehole BH02, was only 2.0 m. The reduced thickness of the gravel deposits in borehole BH03 is likely due to gravel extraction and subsequent infilling in this area of the site.
British Pipeline Agency 2 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
The Environment Agency (EA) classifies the underlying River Terrace Gravels as a Secondary A aquifer of high vulnerability. The site does not lie within a groundwater Source Protection Zone (SPZ) for groundwater abstraction.
The groundwater monitoring carried out in February 2017 indicated the shallow perched water table may be in hydraulic continuity with the groundwater in the River Terrace Deposits in the wider area. The testing for petroleum hydrocarbons indicates the absence of hydrocarbon contamination in the River Terrace Deposits and London Clay in the vicinity of the flood relief channels (BH01 and BH02). However, the sample obtained from the perched water in the fill at BH03 contained slightly elevated concentrations of petroleum hydrocarbons.
The most recent works included a new site reconnaissance visit and a check of the serviceability of the existing monitoring boreholes. The visit was conducted on 25th February 2020.
No changes were noticed between the observations made in 2016 and the observations during the recent site visit in 2020. The boreholes were confirmed to be serviceable for the future monitoring.
1.4 Limitations
The comments given in this report and the opinions expressed are based on the ground conditions encountered during the site work and on the results of tests made in the field and in the laboratory.
However, there may be conditions pertaining to the site that have not been disclosed by the investigation and therefore could not be taken into account. In particular, it should be noted that there may be areas of made ground not detected due to the limited nature of the investigation or the thickness and quality of made ground across the site may be variable. In addition, groundwater levels and ground gas concentrations and flows may vary from those reported due to seasonal, or other, effects.
It should be noted that no recent site investigation works were carried out on site. The findings presented in this document are based on the site works completed in 2017 and a site walkover completed in February 2020.
British Pipeline Agency 3 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
2 THE SITE
2.1 Site location and description
The site comprises of a section of above-ground pipeline located north of the confluence of the Horsemill and Cornmill Flood relief channels at Fishers Green Lane, Lee Valley Park, Cheshunt, EN9 2ED, approximately centred at National Grid reference 537907, 202656 as shown on Figure 1.
The pipe-bridge comprises a single 350 mm diameter pipe, which emerges from below- ground on the eastern side of the River Lea, forms a bridge over the river and then continues below-ground by Hooks Marsh Car Park.
The area surrounding the existing and proposed pipeline routes comprises the Fishers Green lane, which serves two residential properties (Fishers Green Cottage and Fishers Green Farm) and two small car parks. A system of lakes/marshes which are part of Lee Valley Park is located beyond the car park to the west of the river channel.
The area to the east of the channel currently comprises an open agricultural field. The area between the two channels is densely overgrown with trees and shrubs.
Table 1: Site setting
To the east of Two residential properties, grazing fields and a small car park. the channels: Lee Valley Farm comprising a large complex of green houses is situated 300 To the north: m to the north.
To the west of Hooks Marsh and Cheshunt Lakes are situated to the west of the site with a the channel: large industrial estate beyond, approximately 1 km to the west. Historical remnants of a cast iron Victorian aqueduct and nitro-glycerine hills To the south (remnants of a Royal Gunpowder Mill).
The site elevation remains constant throughout with some variation from 19.5 m Ordnance Datum (AOD) at Hooks Marsh Car park on the west side of the site to an elevation of 22 m Ordnance Datum (AOD) by Holyfield Fishery on the east side of the site. The elevation along the River Lea is approximately 21.4 m Ordnance Datum (AOD) with most of the land in the surrounding area remaining flat. No changes occurred on site in the recent years. The levels observed in 2017 remained unchanged.
British Pipeline Agency 4 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
3 PROPOSED VERIFICATION WORKS
This section details the proposed strategy to verify protection of Controlled Waters during decommissioning of the existing pipeline, construction and post-construction phases.
The measures to verify the protection of Controlled Waters will include groundwater/surface water monitoring and a watching brief by an environmental engineer during the key stages of the construction (cutting into the existing pipeline and connecting to the new pipeline section).
3.1 Groundwater and surface water monitoring
3.1.1 Sampling locations
Three groundwater monitoring boreholes (BH01, BH02 and BH03) were sampled in February 2017 to characterise baseline conditions. The boreholes were confirmed serviceable during the recent site walkover conducted 25th February 2020.
In addition to these three existing boreholes, a further four boreholes are proposed to be advanced at strategic locations on either side of the river within 10 m of the proposed pipeline route. The boreholes will be constructed to the full depth of the River Terrace Deposits (RTD), as specified in the previous correspondence with the Environment Agency presented in Appendix C.
The additional boreholes will be required in order to triangulate groundwater flow direction on the banks of the River Lee and provide further monitoring and sampling data throughout the course of the construction / demolition works.
Where possible the existing boreholes (BH01 – BH03) should be protected and monitored during the construction phase, however, if the route of the pipeline requires removal of the existing boreholes, these would need to be appropriately decommissioned. The redundant boreholes would be decommissioned in accordance with Environment Agency guidelines and best practice procedures as specified in Section 3.3.
In addition, three surface water samples should be collected from the sampling locations indicated in Figure 2 during each of the monitoring rounds.
British Pipeline Agency 5 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
3.1.2 Monitoring frequency
At this stage a detailed construction programme that is proposed to start in the second half of 2020 is not available.
The baseline / pre-construction monitoring will comprise data obtained in 2017 and monitoring data that will be obtained during the Enabling Works.
During the construction works it is proposed to monitor and sample the groundwater and surface water on a monthly basis from all existing (BH1 and BH2) and proposed (BH4 to BH7) boreholes. It should be noted that borehole BH3 is located in the area of the proposed open trench and therefore it is likely that this borehole would need to be decommissioned prior to start of the construction works.
On completion of the re-routing works the monitoring schedule will reduce to one monitoring and sampling round every three months. It is proposed that the last monitoring round is to be concluded 12 months from completion of the works. The construction milestones and proposed monitoring dates are summarised in Table 2 below.
Table 2: Construction milestones and proposed monitoring
Construction Proposed monitoring Monitoring Date milestones visits frequency Pre-construction One round off Enabling Works baseline sampling 1st monitoring and (installation of addition September 2020 sampling round - groundwater monitoring September 2020 boreholes and baseline sampling)
2nd monitoring and Monthly Site establishment* November 2020 sampling round – November 2020
3rd monitoring and Shaft construction and December 2020 sampling round – trenchless crossing December 2020
Installation of new th pipelines January 2021 4 monitoring and sampling visit – January Connection of the new 2021 (sealed) pipe
5th monitoring and Demobilisation off site February 2021 sampling visit – February 2021
British Pipeline Agency 6 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
Construction Proposed monitoring Monitoring Date milestones visits frequency
6th monitoring and Construction works March 2021 sampling visit – March completed 2021
7th monitoring and After 3 months sampling visit – June 2021
8th monitoring and After 6 months sampling visit – March 2021 – March September 2021 Post construction works 2022 9th monitoring and After 9 months sampling visit – December 2021
10th monitoring and After 12 months sampling visit – March 2022
Note: *the precise date of mobilisation to the site will be confirmed in Q2 2020
3.1.3 Sampling methodology and In-situ testing
Groundwater samples will be obtained utilising a low-flow sampling methodology from all available boreholes (BH1, BH2 and BH4 to BH7).
The surface water samples will be collected from the middle of the flowing stream of water. Three surface water sampling locations are included in Figure 2. The following parameters will be measured during the sampling: pH, conductivity, redox-potential, turbidity and dissolved oxygen.
3.1.4 Chemical testing
The samples will be tested for speciated petroleum hydrocarbons (TPHCWG) including benzene, toluene, ethyl benzene and xylene (BTEX), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) and alkalinity.
3.1.5 Reporting of monitoring results
The results of monitoring and sampling will be reported after each monitoring round in the form of a factual letter report. The individual factual reports will be incorporated into the final verification report.
British Pipeline Agency 7 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
3.2 Watching brief
A watching brief will be carried out by an environmental engineer during the key stages of the construction (cutting into the existing pipeline and connecting to the new section of the pipeline). The construction programme indicates that the new section of the 350 mm diameter pipeline will be connected in 2020.
The observations during the watching brief and photographic evidence will be included into the final verification report.
3.3 Borehole Decommissioning
On completion of the groundwater monitoring programme and in agreement with the Local Planning Authority and the Environment Agency (EA) the installed monitoring wells will be decommissioned in line with EA guidance. This states that redundant boreholes and wells must be decommissioned appropriately to make them safe and secure preventing preferential pathways being created into the underlying shallow aquifer.
The headworks should be removed, and the casing inspected to ensure it hasn’t corroded or broken. In instances where this is the case then provisions should be made to have the damaged casing removed.
The borehole should be backfilled with clean (washed) uncontaminated material to mimic, where possible, the geological strata against which they are placed. Alternatively, the entire borehole or well can be backfilled with low permeability materials that will prevent significant vertical or horizontal movement of groundwater through or along the borehole.
The boreholes on site (BH01 – BH07) will have discrete zones of slotted pipe targeting specific areas of geological strata for a water sample.
The cable percussive boreholes were drilled to a depth of 20 m bgl and then backfilled with arisings until a depth of 4 m bgl. Between depths of 4 and 2 m bgl slotted pipe with a gravel filter pack were installed to allow groundwater sampling, above which the boreholes were backfilled with plain pipe and bentonite. As such it would be recommended to backfill these boreholes with clean uncontaminated material such as crushed glass or pea gravel from 4 to 2 m bgl.
The Continuous Flight Auger (CFA) boreholes will be constructed with a screened zone in the River Terrace Deposits (RTD). Once redundant, these boreholes will be filled with a clean uncontaminated material such as crushed glass or pea gravel from 7 to 2 m bgl.
British Pipeline Agency 8 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
All backfilled boreholes should be completed with an impermeable plug and cap where the top two metres of the borehole should be filled with cement, concrete or bentonite grout. Records should be kept of the backfill materials used these submitted to the EA and LPA for their records on completion of the works.
British Pipeline Agency 9 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
4 ARRANGEMENTS FOR CONTINGENCY ACTION
The construction works, including excavation of the reception and thrust pits, de- watering of the pits, horizontal drilling and pipe connecting will be carried out by a subcontractor approved and selected by BPA. The subcontractor will provide detailed method statements and risk assessments associated with the works including details of environmental protection measures to be adopted. If any leaks or spills occur during the works, RSK and the EA will be notified. In such a situation RSK would offer technical support and advice on remediation of the site and prepare the remediation strategy. The strategy, including the proposed remedial methods and clean up targets will be submitted and agreed with the EA.
It should be noted that similar works, associated with re-routing of a pipeline, were previously carried out by BPA's approved subcontractors and that the works did not cause any negative effect. At this stage we anticipate that the works will be successfully completed without any leak or spills and therefore the requirement for the remedial strategy is unlikely. The absence of leaks or spills during the construction will be confirmed by RSK's engineer carrying out the watching brief on site and by the results of groundwater/surface water monitoring. The findings of the verification works will be compiled into a verification report, which will be submitted to the EA for approval.
British Pipeline Agency 10 Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
FIGURES
British Pipeline Agency Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00) 30 Site Location
Contains Ordnance Survey data © Crown copyright and database right 2013
Client BRITISH PIPELINE AGENCY (BPA)
Project Title LAND OFF FISHERS GREEN LANE
18 Frogmore Road Tel: +44 (0) 1442 437500 Hemel Hempstead Fax: +44 (0) 1442 437550 Drawing Title Hertfordshire Email: [email protected] HP3 9RT Web: www.rsk.co.uk United Kingdom SITE LOCATION PLAN
Rev Drawn Date Checked Date Approved Date Project Number Drawing File Drawing Number 01ASC 19.07.17 DE 19.07.17 SJ 19.07.17 Dimensions Scale Original Size 1921133 - R02 (00) 1921133 - SLP.dwg FIGURE 1 m 1:50,000 A4 LEGEND
Existing Pipeline Route
Proposed Pipeline Route
Existing Borehole Location
Proposed Borehole Location
Surface Water Sample Location
SW1
Rev. Date Amendment Drawn Chkd. Appd.
BH04 BH106
18 Frogmore Road Tel: +44 (0) 1442 437500 BH01 Hemel Hempstead Fax: +44 (0) 1442 437550 Hertfordshire Email: [email protected] BH105 HP3 9RT Web: www.rsk.co.uk United Kingdom
Client SW2 BH02 BRITISH PIPELINE AGENCY (BPA)
Project Title BH03
LAND OFF FISHER GREEN LANE BH107
SW3
Drawing Title
VERIFICATION BOREHOLE LOCATION PLAN
Drawn Date Checked Date Approved Date ASC 14.11.17 DE 14.11.17 SJ 14.11.17
Scale Orig Size Dimensions 1:1000 A3 m
Project No. Drawing File 1921133 - R02 (00) 1921133 (R02-00) Fig 3.dwg
Drawing No. Rev. FIGURE 3 P1
Scale 1 : 1000 0 10 20 30 40 50m
APPENDIX A SERVICE CONSTRAINTS
1. This report and the site investigation carried out in connection with the report (together the "Services") were compiled and carried out by RSK Environment Limited (RSK) for BPA (the "client") in accordance with the terms of a contract between RSK and the "client", dated March 2020.. The Services were performed by RSK with the skill and care ordinarily exercised by a reasonable environmental consultant at the time the Services were performed. Further, and in particular, the Services were performed by RSK taking into account the limits of the scope of works required by the client, the time scale involved and the resources, including financial and manpower resources, agreed between RSK and the client.
2. Other than that expressly contained in paragraph 1 above, RSK provides no other representation or warranty whether express or implied, in relation to the Services.
3. Unless otherwise agreed the Services were performed by RSK exclusively for the purposes of the client. RSK is not aware of any interest of or reliance by any party other than the client in or on the Services. Unless expressly provided in writing, RSK does not authorise, consent or condone any party other than the client relying upon the Services. Should this report or any part of this report or otherwise details of the Services or any part of the Services be made known to any such party, and such party relies thereon that party does so wholly at its own and sole risk and RSK disclaims any liability to such parties. Any such party would be well advised to seek independent advice from a competent environmental consultant and/or lawyer.
4. It is RSK's understanding that this report is to be used for the purpose described in the introduction to the report. That purpose was a significant factor in determining the scope and level of the Services. Should the purpose for which the report is used, or the proposed use of the site change, this report may no longer be valid and any further use of or reliance upon the report in those circumstances by the client without RSK 's review and advice shall be at the client's sole and own risk. Should RSK be requested to review the report after the date hereof, RSK shall be entitled to additional payment at the then existing rates or such other terms as agreed between RSK and the client.
5. The passage of time may result in changes in site conditions, regulatory or other legal provisions, technology or economic conditions which could render the report inaccurate or unreliable. The information and conclusions contained in this report should not be relied upon in the future without the written advice of RSK. In the absence of such written advice of RSK, reliance on the report in the future shall be at the client's own and sole risk. Should RSK be requested to review the report in the future, RSK shall be entitled to additional payment at the then existing rate or such other terms as may be agreed between RSK and the client.
6. The observations and conclusions described in this report are based solely upon the Services which were provided pursuant to the agreement between the client and RSK. RSK has not performed any observations, investigations, studies or testing not specifically set out or required by the contract between the client and RSK. RSK is not liable for the existence of any condition, the discovery of which would require performance of services not otherwise contained in the Services. For the avoidance of doubt, unless otherwise expressly referred to in the introduction to this report, RSK did not seek to evaluate the presence on or off the site of asbestos, electromagnetic fields, lead paint, heavy metals, radon gas or other radioactive or hazardous materials.
7. The Services are based upon RSK's observations of existing physical conditions at the Site gained from a walk-over survey of the site together with RSK's interpretation of information including documentation, obtained from third parties and from the client on the history and usage of the site. The Services are also based on information and/or analysis provided by independent testing and information services or laboratories upon which RSK was reasonably entitled to rely. The Services clearly are limited by the accuracy of the information, including documentation, reviewed by RSK and the observations possible at the time of the walk-over survey. Further RSK was not authorised and did not attempt to independently verify the accuracy or completeness of information, documentation or materials received from the client or third parties, including laboratories and information services, during the performance of the Services. RSK is not liable for any inaccurate information or conclusions, the discovery of which inaccuracies required the doing of any act including the gathering of any information which was not reasonably available to RSK and including the doing of any independent investigation of the information provided to RSK save as otherwise provided in the terms of the contract between the client and RSK.
8. The phase II or intrusive environmental site investigation aspects of the Services is a limited sampling of the site at pre-determined borehole and soil vapour locations based on the operational configuration of the site. The conclusions given in this report are based on information gathered at the specific test locations and can only be extrapolated to an undefined limited area around those locations. The extent of the limited area depends on the soil and groundwater conditions, together with the position of any current structures and underground facilities and natural and other activities on site. In addition chemical analysis was carried out for a limited number of parameters [as stipulated in the contract between the client and RSK] [based on an understanding of the available operational and historical information,] and it should not be inferred that other chemical species are not present.
9. Any site drawing(s) provided in this report is (are) not meant to be an accurate base plan, but is (are) used to present the general relative locations of features on, and surrounding, the site.
British Pipeline Agency Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
APPENDIX B PLANNING PERMISSION INCLUDING THE SUMMARY OF THE CONDITIONS
British Pipeline Agency Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
APPENDIX C CORRESPONDENCE
British Pipeline Agency Verification Plan for Land off Fishers Green Lane, Cheshunt, EN9 2ED 1921133- R02 (00)
Alena Landers Our ref: NE/2017/127861/02-L01 RSK Geoconsult Ltd Your ref: EPF/0857/17 18 Frogmore Road Industrial Estate Frogmore Road Date: 7 March 2018 Hemel Hempstead Hertfordshire HP3 9RT
Dear Alena
Fishers Green, Waltham Abbey
Verification plan proposal review
Thank you for sending us the Verification plan proposal to review for the above site as part of our cost recovery agreement. We have the following recommendations:
The Geoenvironmental Site Assessment, Project no. 28841 R01 (00) February 2017: Appendix H Exploratory hole records indicates that the base of the River Terrace Gravels to be around 7.50 metres below ground level and depth to ground water around 3.5 metres below ground level.
The Guidance on the design and installation of groundwater quality monitoring points (Science Report SC020093 Environment Agency January 2006: Section 2.3.3) states that the screen should be located such that at least part of the screen remains within the saturated zone during the period of monitoring, given the likely annual fluctuation in the water table.
As that the lowest base of the excavation works is 4.5 metres below ground level, we would recommend reviewing the proposed screen and casing depths of the proposed boreholes to the base of the river terrace deposits.
Should you have any queries regarding this response, please contact me.
Yours sincerely
Chris Padley Sustainable Places Planning Advisor
Direct dial 0208 4749329 E-mail [email protected]
End