The project involved remediating and regenerating a former coking works site contaminated with pollutants like PAHs, phenols, heavy metals, and asbestos. Over 20 years, remediation techniques included thermal desorption, soil screening, and bioremediation to treat over 600,000 cubic meters of contaminated material. Stringent verification procedures with over 20,000 samples ensured materials met standards for residential and recreational use. Groundwater and surface water treatment also exceeded targets. Comprehensive reporting demonstrated that final site conditions posed negligible long-term risks.

1. The Avenue Former Coking Works Remediation and
Regeneration Project (1999-2018)
Project Verification
Martin Westwood
Environmental Scientist BSc (Hons) CEnv
Stage 3 NEC Contract Supervisor/ designer
8 March 2018 IES Land Condition Symposium

2. Scope of Presentation
1. Project Overview
2. Remediation Techniques
3. Verification Procedures
4. Final Site Conditions
5. Verification Reporting

3. History and Works Stages
Year Activity
1890 Avenue Colliery and Lime & Iron Works operational on site
1930 Avenue Colliery and Lime & Iron Works become disused
1952 Construction of The Avenue Coking Works commenced
1956 Works is operational
1992 Works are closed
1999 EMDA take ownership of the site and become responsible for delivering its reclamation
1999 –2005 Stage 1: Plant area drain-down and demolition, site surveys, ground investigations, H&S
and environmental improvement works, desk studies, PRA, DQRA, remediation trials,
development of outline remediation strategy
2005-2006 Stage 2: Pre-qualification exercise and tender for detailed design of remediation strategy
/ Appointment of VSD for detailed design of remediation strategy
2006 –2009 Stage 2: Detailed design of earthworks and remediation strategy, value engineering,
economic appraisal. Early Contractor Involvement / OJEU Procurement / NEC:EEC
Option C Target Contract with Activity Schedule
2009 Stage3: Appointment of VSD for remediation of The Avenue site
2009 - 2016 Stage 3: Remediation and landscaping works
2017-2018 Defects Period and Verification Reporting Site Opens/Development commences
 1991 and 2007: 22 Phases of GI :
415 Boreholes/750 Trial Pits
 Environmental Monitoring
Programmes (Ground gas, Vapour, Air
Quality, Surface Water, Groundwater,
leachate)
 Source characterisation: Identified
Contaminants of Concern : PAHs
(Poly Aromatic Hydrocarbons),
Phenols, DROs (Diesel Range
Organics), PROs (Petrol Range
Organics), BTEX (Benzene, Toluene,
Ethylene, Xylene), Cyanide,
Thiocyanate, Ammonia, Heavy Metals
(Arsenic, Nickel, Cadmium,
Chromium), Asbestos
 Geological / Geotechnical /
Hydrogeological Characterisation

4. Project Overview
Remediation objectives
 Discharge legal obligations: avoid regulatory action under Part IIA of the EPA-Voluntary remediation
 Protect human health (future site users)
 Protect Controlled waters, specifically the River Rother
 28 hectare development platform (residential housing / garden) and public open space (65 hectares)
 Incorporate flood protection measures and SUDs
 Minimise material import / export and maximise material re-use on site (24 material types)
Remediation strategy
 Excavation and treatment of material that had the greatest potential to adversely impact receptors to
a design base of excavation (generally the top of the coal measure lithology)
 Shallow groundwater remediation: limited to shallow groundwater encountered in open excavations,
 Removal of all below ground structures and hazards
 No treatment of the deeper groundwater in the Coal Measures / Aquitard Reinstatement
 Reinstate material to achieve formation levels and adhere to geotechnical specification

5. Site Zones

6. Pre-Remediation Conceptual Site Model

7. Remediation Techniques
Technique Designs
Volume
Final /
Forecast
Treatment (m3)
Thermal desorption 270,300 257,266
Soil screening /sorting 237,600 203,485
Bioremediation 74,000 181,206
Total 581,900 641,497
Off-Site Disposal (Tonnes)
Asbestos 2352 913
Metal 3000 550
Other waste 4600 2470
Recovered Timber 1450 10,000
Tar 0 19,000
Total 11, 402 32,020
All Earthworks (m3)
Total Material volume (cut) 1,883,377 2,244,989
Total Material volume (Fill) 1,934,896 2,178,20
Total 3,818,273 4,423,189
Material Import to Create Landform 0 80,000
Groundwater and Surface Water Treated ?? 650,000+

8. Verification
Minimum Soil 1 per 250 m3 / m2
 Re-use SSAC (6000 samples)
 In situ / delineation testing (5,000 samples)
 Base of excavation testing (3,000 samples)
 Treatment Suitability and Operational Testing (>10,000 samples)
 Treatment Performance Verification (2,500 samples)
Groundwater and Surface Water
 Operational Surface and Groundwater Analytical Testing
 Compliance Surface and Foul Water Discharge Consents
 Treatment Suitability and Operational Testing
 Treatment Performance Verification
Other
 Geotechnical specifications
 Noise/Air /Waste notes/licenses /permits/MMP
Post Completion
 Preliminary Surface and Groundwater Monitoring Programme
 Ground Gas Monitoring Programme and GI
 Long term Surface and Groundwater Monitoring Programme
 Reed Bed Verification

9. Final Site Conditions (Base Chemical / Lithology)

10. Final Site Conditions (Fill Thickness / Unforeseen Excavations)

11. Material Excavated for
Treatment and to Create
Landform
1 High Geotechnical Quality (Reworked Natural Ground): Burnt Red shale.
2 High Geotechnical Quality (Reworked Natural Ground): Cohesive Colliery Spoil /Red Shale
3 Low Geotechnical Quality (Made Ground): Granular Iron Work Waste and Granular Colliery Spoil
4 High Geotechnical Quality (Reworked Natural Ground): Cohesive Colliery Spoil
5 Low Geotechnical Quality: Granular Made Ground
6 Granular Made Ground: Railway ballast / sub-base material
7 Waste Tip Material Upon
8 Lagoon Sediment / Tar /Free product
Material Excavated for
Disposal
9a Lagoon Tar
9b Waste tip material impacted natural ground
9c Inert Waste such as wood, plastic, metal, rags
9d Asbestos Containing Material (ACM)
Natural Ground / Reworked
Natural Ground Excavated
for Treatment / Landform
10 Alluvial Deposits / River Terrace deposits and River Sediments
11 Totally Weathered Mudstone Bedrock (Natural Ground): Mottled Brown Clay
12 Partially Weathered /Weakly Interbedded Undisturbed Mudstone (Natural Ground): Grey Mudstone
13 Weathered / Reworked sandstone (Natural Ground)
Material Output that has
been Subject to
Remediation/Treatment
14 TDU Output Material
15 WTPP Output Material Sorted Gravels, boulders, cobbles (30 mm - 75 mm)
16 Biologically Treated Material: Waste Tip Fines (0-30 mm fraction)
17 Biologically Treated Material: Made Ground
18 Biologically Treated Material: Natural Ground
Manufactured /Reclaimed
Materials Placed as Fill
Material
19 Crushed Demolition Materials (Manufactured Material from on-site material recovery).
20 Timber: (Manufactured Material from on-site material recovery)
21 Horticultural soils: (Manufactured Material from on-site material recovery)
22 Site won Low Quality topsoil/subsoil
Imported Material 23 Imported Material: Crushed Limestone Aggregate (6F5)
24 Imported Material: Horticultural Topsoil
Final Site Conditions (Material Types)

12. Final Site Conditions
(Material Types)

13. Final Site Conditions (Sub Surface / Surface Backfill Chemical)

14. Final Site Conditions (Ground / Surface Water)

15. Reporting

16. Post Completion DQRA Model
 Upward flow from coal measures (artesian /rising groundwater) excluded as aquitard reinstated
 Conceptual agreement that COCs above the Coal Measures will migrate to river / no GW water + COC loss to the aquifer
 Base of excavation derived to excavate and treat all contaminated material above coal measures
 River Rother = Receptor
 In-situ biodegradation not included
 Retardation allowed for (KOC)
 Plume concentration diluted by a factor of 175 (low flow river DF) + 1/10th EQS
 Limited suite of COCs given TDU/cost + COCs co-exist i.e. destroy one, destroy them all
Numerous iterations to reach final RTs
 COC physical/chemical properties: retained in all DQRA
 Source: Material volumes, placement zones, depth, composition - varies as scheme evolves
 Pathway: Hydrogeological Parameterisation - constant review as scheme evolves
 Receptor : River final location - varies as scheme evolves
 Forward mode to check predicted impacts at river (in final alignment)
 As-built data (soil chemistry and properties after treatment / placement)
 As built hydrogeology/ geology /geometry / parametrisation
 3 source areas
 Predicted “Raw Concentration” from 3 models combined and diluted by DF for river concentration
 Model run for 1000 years
 New as built parameters reviewed against design parameters (sensitivity analysis)

17. Measured Surface and Groundwater Verses
Predicted Surface Water Results
Parameter Units Maximum Measured
Groundwater
Concentration: Coal
Measures
Maximum Measured
Perched Groundwater
Concentration: Fill
Material
Maximum Measured
up gradient river
concentration
Maximum Measured
down gradient river
concentration
Predicted River Diluted
Concentration Based on Variable
Leachate SSAC
Sulphate mg/l 5,720 16,000 170 174 -
BAP µg/l - 0.27 0.2 0.13 -
Ammoniacal nitrogen mg/l - 5.23 0.93 0.90 0.0044
Naphthalene µg/l 20,000 237 0.12 0.13 0.1
COD mg/l - 1,950 30.7 35.2 -
pH (range) No unit 4.82 – 8.1 6.54 – 10.3 7.7 – 7.9 7.7 – 8.1 -
Iron (diss.filt) mg/l 1,170 20 0.24 0.22 -
Total PAH µg/l >13,000 480 2.58 2.24 -
Carbon, Organic mg/l - 91.7 7.47 7.47 -
Conductivity mS/cm 9.79 30.8 0.817 0.823 -
Benzene µg/l 69,500 40 <7 <7 1.5
Phenol µg/l <2 <2 <2 <2 2.1
DRO µg/l 113,000 1,420 <10 <10 0.6
GRO µg/l 940,000 79 <50 <50 -
Cyanide mg/l - 154 <0.05 <0.05 0.002
Thiocyanate mg/l 218 50.1 <0.05 <0.05 0.03

18. Thank You. Any Questions