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SECTION 5
SITE INVESTIGATION
SECTION 5
SITE INVESTIGATION
5
SITE INVESTIGATION
5.1
Rationale for Site Investigation and Specific Objectives
5.1.1
The site investigation has been undertaken in accordance with CLR11, Part 2A of the
EPA 1990 and associated statutory guidance, incorporating a desk study followed by
an intrusive investigation. Further targeted investigation and remedial options
appraisal would be dependent on the findings of this site investigation.
5.1.2
The site investigation has been designed to test the validity of the CSM and all the
potential pollutant linkages previously identified in Table 4.2. The key drivers for the
site being:
The risk to human health (dog walkers and other users);
The risk to controlled waters beneath the site; and
The risk to controlled surface waters surrounding the site.
5.1.3
The investigation will, therefore, focus on collecting data on the following:
Quality and nature of Made Ground and landfilled material;
Quality of natural ground within the site boundaries;
Presence of anthropogenic soil gas;
Perched water within / beneath the site;
Leachability of contaminants into the underlying hydrogeology; and
Quality of groundwater in the Minor Aquifer beneath the site.
5.1.4
Our soil sampling rationale for the site investigation has been developed with
reference to the EA guidance ‘Secondary Model Procedure for the Development of
Appropriate Soil Sampling Strategies for Land Contamination’ (Technical Report P5066/TR).
5.2
Methods of Site Investigation
5.2.1
The site investigation was undertaken between the 7 July and 25 July 2008, under the
full time supervision of a PB Engineer. The scope of the works are detailed within
Table 5.1, below;
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Table 5.1: Scope of Site Investigation
Works
Rationale
Excavation of 10 No. deep boreholes
to a maximum depth 20 mBGL across
the site.
Due to historic landfill activities known to operate on
the site, it is possible that elevated concentrations of
contaminants are present within the shallow capped
material, within the landfill material and in deep soils
beneath the land filled material.
Collection and analysis of three soil
samples from each borehole.
Leachability analysis carried out on
landfill material where visual and/or
olfactory evidence of contamination
was detected.
The excavation of deep boreholes to assess potential
risks to site users arising from potentially elevated
concentrations of contaminants in the soil and
determine any potential contamination migration
trend.
Four of the boreholes located out side of the landfill
site in order to determine the nature of the geology
and the depth to the solid geology beneath the site.
These boreholes also help to determine the depth of
groundwater.
Shallow surface sample within the Capping Material
(<1.0 mBGL) and additional samples taken at depths
where there is visual or olfactory evidence of
contamination to assess risks arising from all
potential exposure scenarios in this environment.
The analysis of leachate and eluate to assess if there
is a source in unsaturated ground that may pose a
risk to groundwater at the site.
Excavation of 4 No. window sample
boreholes to a maximum depth 5
mBGL under the entrance road to the
main part of the landfill site.
Collection and analysis of two soil
samples from each borehole.
The targeted collection of soil samples from under the
road to assess any risks posed by material
understood to have been disposed of at the site.
The analysis of leachate and eluate to assess if there
is a source in unsaturated ground that may pose a
risk to groundwater at the site.
Leachability analysis carried out on
landfill material where visual and/or
olfactory evidence of contamination
was detected.
Excavation of 30 No. trial pits to a
maximum depth 5 mBGL across the
site.
Collection and analysis of three soil
samples from each trial pit.
Leachability analysis carried out on
landfill material where visual and/or
olfactory evidence of contamination
was detected.
The excavation of a series of shallow trial pits enable
PB to determine the shallow ground conditions at the
site including the composition of the fill material, the
presence of perched groundwater and the extent of
the landfill.
The collection of shallow surface soil samples
additionally enable PB to assess any risks to future
site users arising from potentially elevated
concentrations of contaminants within the capping
material.
The analysis of leachate and eluate to assess if there
is a source in unsaturated ground that may pose a
risk to groundwater at the site..
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Table 5.1: Scope of Site Investigation
Works
Rationale
10 No. deep boreholes installed for
soil gas, soil vapour and groundwater
monitoring.
The installation and monitoring of the deep boreholes
enable PB to assess any risks to future site users
arising from potentially elevated ground gas and
vapour concentrations in natural ground at the site.
Six rounds of soil gas, soil vapour
and four rounds of groundwater
monitoring.
The influence on controlled waters (Minor Aquifer) of
contaminants originating from the site can also be
identified through groundwater monitoring.
5.2.2
All site works were undertaken in accordance with BS10175: 2001 (‘Investigation of
Potentially Contaminated Sites’).
5.2.3
All works were carried out by experienced personnel under the supervision of a PB
Engineer. A minimum of 2 persons were in attendance when an excavation was in
progress (e.g. PB Engineer and JCB/drill rig operator). If the PB Engineer was called
away from the excavation area, the excavation operative ceased work until the PB
Engineer returned. Before excavation commenced, the proximal area was cleared of
non-essential personnel.
5.2.4
Suitable personal protective equipment was worn at all times during the works.
Eating, drinking or smoking was not permitted on site except in designated messing
areas.
5.2.5
Prior to any excavation works, site services were be located using available service
plans (Appendix H), a Cable Avoidance Tool (CAT) and a signal generator (where
appropriate). As an additional precaution, excavations were hand dug to 1.2 mBGL
where possible.
5.2.6
All arisings were placed upon heavy-duty plastic sheeting to avoid surface
contamination. Excess soil arisings that required disposal were stored in accordance
with best practice. This involved locating an area where a lockable skip was
accessible by the site staff for the safe storage of the site soils. At the end of the
work, the skip was removed by a licensed contractor for off-site disposal, once the
required Waste Management 2 classification had been determined.
5.2.7
Waste water collected during the purging of groundwater from boreholes was stored
in bunded drums and removed by a licensed contractor for off site disposal. All such
works will comply with PB’s Environmental Monitoring System (ISO 14001
accredited).
Boreholes
5.2.8
Deep boreholes were excavated using a Hollow Stem Rotary Drilling Rig. This
technique has the advantage of recovering soil cores within a split spoon core, which
can easily be washed after each use. The excavation of window sample boreholes
was achieved through the use of a smaller drop weight window sampling rig, which
recovers cores using disposable semi-rigid polycarbonate plastic liners. These
sampling techniques allow for the accurate logging of subsurface ground conditions
and negate the risk of cross contaminating the ground surface. In addition, it also
provides sufficient material for sampling purposes, which meant that the PB Engineer
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was able to sample from discrete depths accurately. These types of drilling
techniques are extremely clean and resulted in minimal disruption to the site.
5.2.9
The rigs were securely positioned over borehole locations prior to commencement of
sampling. On uneven ground or slopes, the rig was prior to sampling.
5.2.10
When sampling was in progress, an area of approximately 2m around the sampling
rig was clearly marked preventing unauthorised access.
5.2.11
Where it was required that drilling equipment (including casing) be washed down after
every use. This w carried out into impermeable containers over hardstanding areas
(where possible). Spill kits including absorbent pads were held on site.
Trial Pits
5.2.12
Trial pits were excavated using a JCB type excavator. Under no circumstances did
anyone enter an excavation. All samples were collected from excavation arisings
only.
5.2.13
Trial pits were backfilled immediately upon completion, with the arisings placed back
in reverse order of excavation. No trial pits were left unsupervised or left open
overnight.
5.2.14
‘Deep Excavation’ warning signs were placed in the proximity of open excavations.
Barriers and warning tape were also placed around open excavations preventing
unauthorised access to the working area.
5.3
Laboratory Analysis
5.3.1
A total of 115 No. soil samples were collected during site works and submitted for
laboratory analysis from 10 No. deep boreholes (maximum depth 16.2 mBGL), 4 No.
window sample boreholes (maximum depth 5.0 mBGL) and 30 No. trial pits
(maximum depth 4.3 mBGL). The positions of all borehole and trial pit locations are
illustrated within Figure 2. The following determinands were scheduled for laboratory
analysis:
Table 5.2: Basic Suite of Determinands
Limit of
Detection
(mg/kg)
UKAS
Accreditation
Technique
5
Y (MCERTS)
ICPMS
Cadmium
0.5
Y (MCERTS)
ICPMS
Chromium
1
Y (ISO17025)
ICPMS
Lead
1
Y (MCERTS)
ICPMS
0.5
Y (MCERTS)
ICPMS
Nickel
1
Y (MCERTS)
ICPMS
Selenium
1
Y (ISO17025)
ICPMS
Determinand
Arsenic
Mercury
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Table 5.2: Basic Suite of Determinands
Limit of
Detection
(mg/kg)
UKAS
Accreditation
Technique
Copper
1
Y (MCERTS)
ICPMS
Zinc
1
Y (MCERTS)
ICPMS
0.5
Y (ISO17025)
0.1 units
Y (MCERTS)
Electrometric
5
-
Colourimetry
0.01%
Y
Ion Chromatography
Sulphide (S )
0.5
-
Colourimetry
Sulphur (S) (total)
1.0
Y (MCERTS)
Colourimetry
1
Y (MCERTS)
Colourimetry
0.3
Y
HPLC
MCERTS
Submitted
Colourimetry
5
0.5
Y (MCERTS)
GCFID
Determinand
Boron (B) (Water
Soluble)
pH Value
Chromium (VI)
Sulphate (SO4
)(total)
Cyanide (total, free)
Phenols
ICPMS
Thiocyanate
Speciated PAH
UKAS - United Kingdom Accreditation Service
ICPMS - Inductively Coupled Plasma Mass Spectrometry
HPLC - High Performance Liquid Chromatography
GCFID - Gas Chromatography Flame Ionization Detection
TPH - Total Petroleum Hydrocarbons
5.3.2
Additional determinands were analysed at locations where visual or olfactory
evidence of contamination was apparent, and at further locations to provide coverage
of the site. Up to 30 No. soil samples were additionally scheduled for the following
determinands:
Speciated Total Petroleum Hydrocarbons (TPH) using Criteria Working Group
Methodology (TPHCWG);
Asbestos (screen); and
Volatile Organic Contaminants (VOC).
5.3.3
To support the derivation of appropriate tier 1 screening values, a total of 44 No. soil
samples were analysed for Total Organic Carbon (TOC).
5.3.4
Groundwater samples were collected from the 9 No. deep boreholes installed during
this investigation and 4 boreholes previously installed over four monitoring rounds,
totalling 52 No. samples. Samples were stored in cool boxes (<4°C) and couriered to
the laboratory no more than 24 hours after sampling. All samples were preserved in
accordance with laboratory guidance.
5.3.5
Groundwater samples were collected and analysed for the following determinands:
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Table 5.3: Basic Suite of Determinands
Determinand
Limit of
Detection (ug/l)
UKAS
Accreditation
Technique
1
Y
ICPMS
Cadmium
0.5
Y
ICPMS
Chromium
1
Y
ICPMS
Lead
1
Y
ICPMS
0.5
Y
ICPMS
Nickel
1
Y
ICPMS
Selenium
1
Y
ICPMS
Copper
1
Y
ICPMS
Zinc
1
Y
ICPMS
Boron
20
Y
ICPMS
0.1 units
Y
Electrometric
Chromium (VI)
50
-
Colourimetry
SO4
50
Y
Ion Chromatography
SO
50
-
Colorimetric
Cyanide (total, free)
50
-
Colorimetric
Phenols
300
Y
HPLC
Thiocyanate
500
-
Colorimetric
Speciated PAH
0.05
Y
GCFID
Speciated TPH
0.1
Y
GCFID
VOC
0.1
Y
Chromatographic
COD
10000
Y
Colorimetric
BOD
3000
-
Electrometric
Hardness
5000
Y
Ion Chromatography
Chloride
100
Y
Ion Chromatography
Ammoniacal Nitrogen
10
-
Colorimetric
OC Pesticides
0.2
-
GC-MS
OP Pesticides
0.2
-
GC-MS
ON Pesticides
0.2
-
GC-MS
Arsenic
Mercury
pH Value
(total)
GC-MS - Gas Chromatography-Mass Spectrometry
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5.3.6
Where groundwater was not present and where there was visual and/or olfactory
evidence of contamination, leachability testing was undertaken to indicate the
potential (worst case) for soil contaminants to leach from soils. Leachability testing
was undertaken on 30 No. soil samples.
5.3.7
All soil and water samples were analysed by Chemtest, Newmarket, a UKAS and
MCerts accredited laboratory. Full schedules of sample analyses are provided in
Appendix F.
5.4
General Ground Conditions
5.4.1
Ground conditions have been logged in accordance with the requirements of
BS5930:1999. Detailed logs for the boreholes and trial pits are provided in Appendix
E, along with photographs of exploratory locations.
5.4.2
A summary of the ground conditions identified during the investigation is given below.
Made Ground
5.4.3
Made Ground was encountered within 1 borehole and 11 trial pit locations (BH110,
TP08, TP19, TP20, TP21, TP22, TP23, TP24, TP25, TP26, TP27 and TP28). The
average thickness of Made Ground within the trial pits is 1m and 3m within BH110.
Generally the Made Ground is sandy CLAY or clayey SAND with sandstone and
limestone gravel. It is understood that Made Ground was used as capping material
and to generate a mature sand dune appearance in keeping with the surrounding
area.
Fill Material
5.4.4
Fill material was encountered within all the exploratory locations with the exception of
BH101, BH102 and BH103 and TP05, TP06, TP07 and TP30. These locations were
specifically located out side the landfill to determine the ground conditions outside the
landfill area.
5.4.5
The average thickness of the landfill material identified within the boreholes was
4.6m. The majority of the trial pits did not identify the base of the landfill indicating a
greater depth of fill material than 3.5m. Trial Pits TP01 to TP04 and the window
sampling locations were located within the entrance road area. The average thickness
of fill in these locations was 2.65m. TP16 was located on the western side of the
landfill to identify the extent of the landfill in that area and identified a thickness of
1.2m of fill material.
5.4.6
Generally the fill material was a dark grey brown sandy gravely CLAY or clayey
gravely SAND with occasional cobbles with a high organic content, consisting of
broken down refuse or broken down garden waste. The gravel and cobbles consisted
of concrete, brick rubble and sandstone. Also present in abundance is glass, metal,
wood (including chipboard) and plastic (including bags and bottles).
5.4.7
The fill material found within the entrance road was a sandy GRAVEL or gravely
SAND containing glass, coke, clinker, brick, ceramics, crushed tarmac, sandstone
and limestone. At some of the locations bent metal (possibly old drums) was identified
with some wood and plastic.
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5.4.8
Additional visual and olfactory indicators that may be of some concern identified
during the investigation are described in Table 5.4:
Table 5.4: Visual and Olfactory Identification of Potential Contaminants
Exploratory
Location
Visual Evidence
Olfactory Evidence
-
Elevated levels of landfill gas
detected during drill area monitoring.
BH105
A few spots of a sheen on the
water
Strong odour of decomposing
material.
BH107
-
Odour of decomposing material
BH110
-
Elevated levels of landfill gas
detected during drill area monitoring.
WS1
Occasional Tarmac between 1.5
and 1.8m
-
WS2
Crushed Tarmac
-
TP01
Fragments of coke and clinker.
-
TP02
Fragments of rusted metal scraps
(including possible old drums) and
coke and clinker.
-
BH104
TP03
Fragments of rusted metal scraps
(including possible old drums)
-
TP15
-
Elevated levels of VOCs recorded on
the PID
TP18
-
Elevated levels of VOCs recorded on
the PID
TP19
-
Elevated levels of VOCs recorded on
the PID
TP21
-
Elevated levels of VOCs recorded on
the PID
TP29
Occasional ash and clinker
-
PID - Photo Ionisation Detector
Natural Ground
5.4.9
BH101, BH102 and BH103 and TP05, TP06, TP07 and TP30 were specifically
located within the natural ground to assess the nature of the natural ground and to
determine the extent of the landfill. All the boreholes encountered the natural ground
at approximately 4.6 mBGL as did TP16 at 1.2 mBGL. The natural ground was
encountered in the trial pits and window sample holes located in the entrance road at
a depth of approximately 2.6 mBGL.
5.4.10
Topsoil was identified in all the exploratory location consisting of organic rich sand in
the natural ground and increased clay within the landfill area. Below the Topsoil was
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generally coarse grained gravely SAND with occasional cobbles. Occasionally the
sand was inter-bedded with soft clayey sandy SILT.
5.4.11
Below the sand, between 2-3m below ordnance datum is soft grey clayey sandy SILT
approximately 5m thick. Below the silt at approximately 8m below ordnance datum is
dark grey well fractured fine grained SANDSTONE with some ironstone staining,
inter-bedded with very soft grey sandy very gravely CLAY. The sandstone is thought
to be the well weathered start of the Crackington Formation.
5.4.12
There was no visual or olfactory evidence of potential contamination within the natural
ground.
5.5
Buried Structures
5.5.1
The locations of buried structures encountered during excavations are provided in
Table 5.5.
Table 5.5: Locations of buried structures encountered during excavations
Exploratory Location
Depth (m BGL)
BH104A
Buried Structure
2.0
Unknown, believed to be concrete
2.0
Hard layer of crushed compacted
concrete, very difficult to drill through.
2.5
Hard layer of crushed compacted
concrete, very difficult to drill through.
3.6
Hard layer of crushed compacted
concrete, very difficult to drill through.
TP11
2.0
Large sub-angular boulder of concrete
TP16
1.0
Railway sleeper
BH107
BH109
BH110
5.6
Groundwater Observations
5.6.1
A total of 9 No. boreholes were excavated and installed during the site works to
monitor groundwater quality surrounding and beneath the site and leachate quality
within the landfill. Deep boreholes were installed into the sands below the landfill
material.
5.6.2
Depths to the groundwater surface within these monitoring wells are given within
Table 5.6a. Approximate details of the tide state during each monitoring visit are given
in Table 5.6b (Tide data from Proudman Oceanographic Laboratory (Natural
Environment research Council) – www.pol.ac.uk).
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Table 5.6a: Results of Groundwater Monitoring Visits
Groundwater Levels (AOD m)
Location
05/08/08
BH 101
13/08/08
22/08/08
29/08/08
05/09/08
12/09/08
Well not installed
BH 102
2.399
1.388
2.317
1.436
2.357
1.377
BH 103
2.397
0.695
1.006
1.783
-
1.782
BH 104
2.017
1.223
1.954
1.578
4.752
1.544
BH 105
2.593
0.953
1.599
1.161
1.303
1.401
BH 106
2.139
2.422
3.899
1.083
0.881
1.23
BH 107
2.575
1.985
2.288
1.581
0.928
2.017
BH 108
3.743
2.617
3.998
2.643
3.271
2.695
BH 109
5.181
5.273
3.011
5.261
5.401
5.38
BH 110
1.996
1.836
3.965
1.839
2.031
1.851
Height (m
AOD)
Tide State
Table 5.6b: Tide Data
Height (m
AOD)
Date
Tide State
05/08/08
High Tide
08.15
4.4
Low Tide
14.45
-3.55
13/08/08
Low Tide
09.00
-1.55
High Tide
15.50
2.65
22/08/08
High Tide
09.00
3.8
Low Tide
15.00
-3.2
29/08/08
Low Tide
10.30
-3.3
High Tide
17.00
4.2
05/09/08
High Tide
09.00
3.95
Low Tide
14.30
-2.5
12/09/08
Low Tide
09.30
-2.3
High Tide
16.00
3.2
Time
Time
5.6.3
Groundwater monitoring visits were undertaken by a PB Engineer on 5, 13, 22 and 29
August 2008 and 5 and 12 September. Water sampling was undertaken on the 22
August and 5 and 12 September. A total of 52 No. groundwater samples were taken
from the deep boreholes. All samples were submitted for laboratory analysis. The
results of water monitoring are given within Appendix E and the results of water
analysis are provided within Appendix F.
5.6.4
Tide data from the nearest tidal monitoring station in Ilfracombe and against weather
data from the nearest weather station in Chivenor (Nr. Barnstable) has also been
obtained.
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5.7
Surface Water Observations
5.7.1
Northam Burrows is located on a land spit and is surrounded by coastal waters on
three sides. Surface water was not sampled as part of this investigation.
5.8
Photo Ionisation Detector (PID)
5.8.1
A PID was used on site during the works to screen samples with visual and/or
olfactory evidence of contamination for the presence of volatile organic compounds.
Soil samples were bagged, allowed to equilibrate and screened for a minimum period
of 60 seconds.
5.8.2
All deep boreholes and window sample boreholes were installed for vapour
monitoring. Each borehole was screened with a PID over six monitoring rounds to
detect the presence of volatile organic compounds in the soil environment, and to
account for any interference this may cause with the ground gas monitoring
undertaken.
5.8.3
Screening results are provided within Appendix E.
5.9
Soil Gas Emissions (CH4, CO2 and O2)
5.9.1
9 boreholes were installed for gas monitoring. Each borehole was gas monitored with
an infra-red gas analyser (GA2000) over six monitoring rounds to assess any risks to
future site users from soil gas. Results of soil gas measurements methane, carbon
dioxide and oxygen are given in Appendix E.
5.10
Quality Assurance / Quality Control
5.10.1
The data collection, storage and preparation of this report has been undertaken in
accordance with PB’s Integrated Management System which operates within the
standards outlined in ISO 9001 (BSI Certificate No. Q06143) and ISO 14001 (BSI
Certificate No. A12283).
5.11
Ground Conditions and Hydrogeology
5.11.1
In the absence of ‘as-built’ construction drawings, the following section is based on
interpretation of the available site investigation data.
5.11.2
Based on the available information, the following seem likely:
5.11.3
Landfilled material extends into the underlying Natural Ground comprising silts and
sands, with no apparent liner system or cover;
5.11.4
The landfill appears higher in elevation than surrounding areas, so some radial
runoff may be expected as may some doming of leachate within the landfill;
5.11.5
The general groundwater gradient within the surrounding strata appears to be
influenced by both the proximity to the sea and estuary;
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5.11.6
The majority of waste material within the landfill is saturated, and the observed data
provide no evidence for the presence of an unsaturated zone within the Natural
Ground directly beneath the landfill;
5.11.7
Groundwater and leachate below and within the landfill are tidally influenced
and are in hydraulic continuity with sea and estuary; and
5.11.8
The underlying solid geology comprises the Crackington Formation, which is a Minor
Aquifer.
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