remediation strategy and verification plan
TRANSCRIPT
Remediation Strategy and Verification Plan
Site: 45 Broadwater Road, Welwyn Garden City
Client: C Field Construction Ltd.
Report Date: 1st July 2021
Project Reference: JN1576
TABLE OF CONTENTS
A INTRODUCTION.....................................................................................................................................................................1
1 AUTHORITY ........................................................................................................................................ 1
2 LOCATION .......................................................................................................................................... 1
THE SITE LOCATION IS INDICATED ON FIGURE 1 WITHIN APPENDIX A. ................................................................................................................ 1
3 PROPOSED CONSTRUCTION .............................................................................................................. 1
4 SCOPE................................................................................................................................................ 1
B BACKGROUND INFORMATION ..........................................................................................................................................2
5 SITE INVESTIGATION WORKS ............................................................................................................ 2
6 SITE HISTORY .................................................................................................................................... 2
7 RELEVANT POLLUTANT LINKAGES ..................................................................................................... 3
C REMEDIAL OBJECTIVES AND OPTIONS............................................................................................................................3
8 REMEDIAL OBJECTIVES ..................................................................................................................... 3
9 OPTIONS APPRAISAL ......................................................................................................................... 3
D REMEDIATION STRATEGY ...................................................................................................................................................5
10 REMEDIATION METHODS .................................................................................................................. 5
11 ASSESSMENT CRITERIA ..................................................................................................................... 5
E VERIFICATION PLAN ............................................................................................................................................................6
12 DATA COLLECTION ............................................................................................................................ 6
13 REPORTING ........................................................................................................................................ 6
14 DISCOVERY STRATEGY ...................................................................................................................... 7
15 GENERAL GUIDANCE ........................................................................................................................ 7
APPENDIX A Site Plans
APPENDIX B Verification Criteria
JN1576 Phase III Contamination Site Investigation Report 1 1 July 2021
A INTRODUCTION
1 Authority
Our authority for carrying out this work was given by Brian Greene of C Field Construction, dated 28th May 2021.
2 Location
The site is located at 45 Broadwater road, in Welwyn City Garden, Hertfordshire AL7 3AX.
The approximate National Grid Reference of the site is TL 24180 12450.
The site location is indicated on Figure 1 within Appendix A.
3 Proposed Construction
It is proposed to construct a four-storey care home, with associated hard and soft landscaping.
For the purposes of the contamination risk assessment, and taking a conservative approach, the proposed development land use is classified as Residential with home-grown produce, (CLEA model1/C4SL report2). The gas sensitivity of the site is therefore rated as High (CIRIA C6653).
4 Scope
This report presents our Remediation Options Appraisal, Remediation Strategy, and Verification Plan for the proposed remedial works at the site.
As with any site there may be differences in soil conditions between exploratory hole positions.
The findings and opinions conveyed via this report are based on information obtained from a variety of sources as detailed within this report, and which Southern Testing Laboratories Limited believes are reliable. Nevertheless, Southern Testing Laboratories Limited cannot and does not guarantee the authenticity or reliability of the information it has obtained from others.
This report has been prepared for the sole internal use and reliance of C Field Construction Ltd. and their appointed Engineers. This report shall not be relied upon or transferred to any other parties without the express written authorization of Southern Testing Laboratories Limited. If an unauthorised third party comes into possession of this report they rely on it at their peril and the authors owe them no duty of care and skill.
The recommendations contained in this report may not be appropriate to alternative development schemes.
1 Environment Agency Publication SC050021/SR3 ‘Updated technical background to the CLEA Model’ (2009). 2 SP1010 Development of Category 4 Screening Levels DEFRA (2014) 3 CIRIA C665 (2006) Assessing risks posed by hazardous ground gases to buildings.
JN1576 Phase III Contamination Site Investigation Report 2 1 July 2021
The contamination screening values used are valid at the time of writing but may be subject to change and any such changes will have implications for the assessments based upon them. Their validity should be confirmed at the time of site development.
B BACKGROUND INFORMATION
5 Site Investigation Works
The site has been the subject of a series of site investigation reports, as listed below:
Ref Date Author Title/Ref No. Subject
1 2019 Integral Geotechnique
(Wales) Limited (IGWL)
Not known Phase I and II Site Investigation Report
2 October 2020 A F Howland Associates
Ground Investigation Report for a proposed
residential care home/JAH/20.212/GIR
Phase III ground investigation report
3 July 2021 ST Consult Phase III Contamination
Investigation Site Report
Phase III contamination Investigation
These reports provide good coverage and characterisation of the site and information derived from these reports is discussed below. The reader is referred to the original reports for supporting detail if needed. These reports are referred to below by the number given in the left hand column of the above table.
6 Site History
The desk study was very briefly summarised in [2]. The site has reportedly been occupied by
buildings, used for light industrial activity, since the 1930’s, with some reconfiguration of these
between 1960 and 1990.
JN1576 Phase III Contamination Site Investigation Report 3 1 July 2021
7 Relevant Pollutant Linkages
The various site investigations and risk assessments carried out [1, 2 and 3] identified the following Relevant Pollutant Linkages for the site:
Contaminant/Source Pathways Receptors
Asbestos within the made ground (generally low-level)
Soil/dust dermal exposure
Soil/dust ingestion/inhalation
Site/Construction workers
Future residents
PAH’s in Made Ground Ingestion/inhalation/dermal contact
Direct Contact
Future residents and construction Workers
Structures/services
Zinc/Copper in Made Ground Vegetation growing in contaminated soil
Flora
Petroleum Hydrocarbons Soil/dust ingestion/inhalation
Soil/dust ingestion/inhalation
Direct contact
Migration through soil
Site/Construction workers
Future residents
Structures/services
Perched groundwater
C REMEDIAL OBJECTIVES AND OPTIONS
8 Remedial Objectives
It is proposed to construct a four-storey care home, with associated hard and soft landscaping.
On the basis of the investigation carried out date and site proposals, the remediation objectives are as follows:
1. Reduce any risk, to the site workers and future residents, from the asbestos, lead, zinc, lead, PAHs and TPH identified in the made ground material.
2. To reduce the risk to the perched groundwater from the hotspot of diesel identified.
3. To reduce the risk to water main pipes from the generally minor levels of TPH/PAH recorded in the soils on site.
9 Options Appraisal
9.1 Asbestos Containing Materials (ACMs), Lead, Zinc, Copper, TPH and PAHs
The risks to human health receptors from generally low-levels of asbestos, lead, zinc, copper PAHs and TPH in the Made Ground could be dealt with by several methods. In respect of construction and maintenance workers, the use of PPE and safe working practices (minimising disturbance of the soil, creation of dust and the extent and duration of contact with soils) can reduce risk by helping to break the exposure pathways.
However, while use of these measures should be considered as part of good practice in construction
JN1576 Phase III Contamination Site Investigation Report 4 1 July 2021
and maintenance, they typically are looked upon as a measure of last resort and need to be used in combination with other measures. Neither are such measures appropriate for future site users (store workers and customers). Breaking the exposure pathway prior to construction by emplacement of imported clean material and/or impermeable cover over the made ground could reduce risks to human health receptors including future site users. Buildings, access roads and car parking spaces constitute impermeable cover and therefore imported soils would only be needed for areas of the site proposed as soft landscaping.
Removing the source by careful selective excavation of affected soils and subsequent off-site disposal to an appropriately licensed facility is also capable of reducing/eliminating the risk to human health receptors. As with emplacement of a barrier of clean material, this would only be required for soft landscaping areas, as buildings, access roads and car parking spaces will break the pathway.
Off-site disposal of contaminated soils and importation of clean materials place additional demands on aggregate resources and waste disposal capacity, and both require significant road haulage. Use of these remediation methods therefore requires that the quantities involved be minimised to ensure the approach remains sustainable in respect of resources, energy and traffic impacts.
A discovery strategy will also need to be in place to deal with any more significant concentrations of asbestos (or any other contamination) that come to light during the site development work (see section 15 below).
9.2 Petroleum Hydrocarbons and PAHs
Although there was no visual and olfactory evidence of any significant organic contamination in the trial holes in the most recent investigation, some basic screening was carried out. In addition, a hotspot of significant diesel contamination was identified by others at depth in WS 105.
Organic contaminants present in the soils, particularly the PAH’s and petroleum hydrocarbons found in some of the Made Ground on site, could affect plastic underground service pipes (such as the types used by water and gas supply companies). Guidance should be sought from the relevant companies regarding any proposed plant in the affected area. Many water supply companies now require higher specification pipe on contaminated sites, even following remediation. At this stage, allow for Protecta Line pipes or similar.
For the diesel contamination at depth, the risk to the perched groundwater, along with any minimal risk to the end users, is best mitigated by excavation and removal. The identified impact appears to be of such small volume to make any more sustainable remediation, such as bio-remediation or other treatments, impractical; furthermore, the diesel impact is not volatile and, therefore, not suitable for any sustainable techniques.
9.3 Zinc and Copper
An isolated high concentration of zinc and copper was reported in the Made Ground analysed from TP4. Although at the concentrations and pH measured the impact is not considered a significant risk, these are phytotoxic metals and some clean cover will be required to provide a growing medium for new planting.
JN1576 Phase III Contamination Site Investigation Report 5 1 July 2021
D REMEDIATION STRATEGY
10 Remediation Methods
The Remediation Strategy will comprise the following:
Location Details
Diesel impact at depth 2.7m in WS 105
Removal of any petroleum hydrocarbon impacted soils and perched groundwater. The exposed soil will require inspection and validation testing to confirm that it is suitable to remain on site.
Soft landscaped areas
Provision of 300mm of certified clean topsoil in any new soft landscaping areas. This should be increased to 600mm of certified clean subsoil and topsoil and subsoil for any garden/vegetable growing areas.
New Water Supply pipes Allow for Protecta-Line pipes
11 Assessment Criteria
Post-removal of diesel, the exposed soils in the validation trench will comply with the following re-use criteria:
Soils
Hydrocarbon Substance or Fraction Measured Concentrations in mg/kg*
BTE
X
Benzene 0.087
Toluene 130
Ethylbenzene 47
Xylenes 56
Aliphatics
EC5-EC6 42
>EC6-EC8 100
>EC8-EC10 27
>EC10-EC12 130
>EC12-EC16 1100
>EC16-EC35 1100
Aro
matics
EC5-EC7 (Benzene) 70
>EC7-EC8 (Toluene) 130
>EC8-EC10 34
>EC10-EC12 74
>EC12-EC16 140
>EC16-EC21 260
>EC21-EC35 1100
*LQM/CIEH Suitable 4 Use Levels (S4ULs) for a residential with homegrown produce consumption land use, and a 1% Soil Organic Matter content.
JN1576 Phase III Contamination Site Investigation Report 6 1 July 2021
Imported topsoil shall be free from deleterious materials, weeds and contamination. The material to be used will comply with the appropriate BS Specifications for Topsoil (BS 3882:2007) and the analysis shall also comply with the values given for (residential with plant uptake) in the table in Appendix B.
In addition to the certification from the supplier, imported soils may also need to be independently sampled and tested, depending on the source and views of the local authority.
These values are valid at the time of writing but may be subject to change and any such changes will have implications for the assessments based on them. Their validity should be confirmed at the time of site development.
Perched Groundwater
Depending on the views of the regulators, it may be necessary to sample and test the perched water again, in the vicinity of WS 105. This will likely necessitate the installation of a new groundwater monitoring well.
E VERIFICATION PLAN
12 Data Collection
Location Data Responsible party
Diesel Hotspot (WS 105)
Excavation and removal of any petroleum hydrocarbon impacted soils.
Main contractor
Provision of consignment notes for the petroleum hydrocarbon contaminated soils removed from site.
Main Contractor
Sampling & confirmatory laboratory analysis of the exposed soils
ST Consulting
Soft Landscaped areas
Post placement check of thickness
Post placement soil samples (if required)
Consignment Notes (both exported topsoil and certified clean imported topsoil)
ST Consult
ST Consult
Main contractor
Buried services Allowances for fully barrier-protected piping
Main contractor
13 Reporting
At the end of the remediation, a verification report will be produced by ST Consult.
JN1576 Phase III Contamination Site Investigation Report 7 1 July 2021
14 Discovery Strategy
As with any site, areas of contamination not identified during site investigation works may come to light in the course of redevelopment. Accordingly, a discovery strategy will be adopted to ensure that any hitherto unknown contamination is identified and dealt with in an appropriate manner, as follows:
• A close watch will be maintained during all demolition and excavation works.
• In the event that unexpected or malodorous soils or liquids are encountered, excavation work shall cease in the affected area.
• The affected area shall be made safe and fenced off to prevent unauthorised access.
• The Site Manager shall notify ST Consult of the discovery, who will attend site to inspect the suspect materials, provide advice and take samples as necessary. Within ST Consult, Joe Kelly shall be the first point of contact.
• The Site Manager shall notify Welwyn Hatfield Borough Council of the discovery. Within the council, the Contaminated Land Officer shall be the first point of contact.
Any suspect excavated soil will be stockpiled separately on polythene sheeting, covered, and tested before being removed.
15 General Guidance
In general terms, the workforce and general public should be protected from contact with contaminated material. There is a range of relevant documents published by the Health and Safety Executive, and organisations such as CIRIA, and the BRE.
Some soils will require removal from site and disposal to suitably licensed landfills. Different guidelines and charges will apply to different waste classifications. As waste producers, the Developer holds responsibilities under the various governing regulations, including:-
• Ensuring that waste is characterised in accordance with current Technical Guidance.
• Ensuring that waste is disposed of at a facility appropriately licensed to receive the waste as classified.
• Keeping accurate records of all waste classification, transfer and a disposal log including information such as:
o Date, Waste Classification, Carrier’s Registration Number, Transfer Note Number, Ultimate Destination.
• Submitting full copies of those records for inclusion in validation/closure reports.
Maintaining those records for potential future regulatory inspection.
APPENDIX A
Site Plans
85.64
85.67
85.6
5
85.60
85.53
85.53
85.5985.59
85. 5
4
85.6
3
85.90
86.05
85.75
85.7
8
85.6
1
85.5
5
85.4
6
85.3
8
85.4785.60
85.4
6
85.44
85.4985.52
85.53
85.65
85.8
285.7
5
85.6
9
85.7
4
85.8
7
85.9
4
85.75
MH S/W CL 85.9585.95
85.71
85.54
85.67
85.84
85.95
86.09
86.3
2
86.5
1
86.5
5
86.6
5
86.4
78
6.3
0
86.2
8
86.1
8
85.9
28
5.7
5
85.7
2
85.8
3
86.0
2
86.2
8
86.2
3
86.1
3
87. 3
387.4
7
87.1
8
87.1
5
86.8
8
85.42
85.60
85.61
85.66
85.65
85.45
85.22
85.70
85.47
85.39
85.36
85.34
85.0
0
85.3
3
85.93
86.12
86.11
86.05
86.06
85.7
7
85.90
85.
87
85.96
85.9
5
85.84
85.6
5
85.7
0
85.6
5
85.62
85.8
5
86.8
5
86.9
0
86.7
5
86.6
8
85.7
5
85.8
6
MH UTLCL 85.78
85.82
85.
72
85.7
2
85.70
85.6
9
86.72
86.5
9
86.5
3
85.85
85.94
85.93
85.88
86.09
85.92
85.63
85.64
85.64
85.65
85.94
85.53
85.65
85.70
85.73
85.67
85.57
85.55
85.42
85.55
85.59
85.64
85.60
85.60
EL 92.36
PW
L 9
5.0
7
85.0
1
85.73
85.9
7
h 6m
Oak
h 6mOak
h 6mOak
h 12mApprox Position
h 12m
Approx Positionh 12m
Approx Position
h 12m
Approx Position
h 12m
Approx Position
h 12mApprox Position
h 10m
Sycamore
h 4mMultibole
h 12mSycamore
h 12m
Sycamore
h 12m
Sycamore
h 10m
h 10mSycamore
h 10mSycamore h 10m
Sycamore
h 8m
Sycamore
h 14mSycamore h 10m
Sycamore
h 12m
h 12m
h 8m
h 8m
h 16m
h 10m
h 2m
h 12m
h 12m
h 12m
h 10m
h 10m
h 10m
h 10mSycamore
h 12mSycamore
h 12m
h 8mMultibole
h 8m
Multibole
BT
BT
BT
BT
BT
CA
TV
BT
bu
s s
top
86.7
2
86.7
2
86.7
8
bu
s s
top
b r i c k b u i l d i n g
b r i c k b
b r
i c
k b
u i l d
i n
g
b r
i
RFL 93.94
PW
L 9
5.0
7
PW
L 9
5.0
9
b r i c k b u i l d i n g
PWL 95.35
b r i c k b u i l d i n g
g r a s s
g r a s s
u n s u r f a c e d / t a r m a c
t a r m a c
b r i c k p a v i o r s
b r
i c k
p
a v
i o
r s
b r
i c k
p
a v
i o
r s
U/S
brick paviors
S/B
gas
box
g r
a s
s
brick paviors
b u s h
r e f u s e h e a p
w o o d e n p a n e l f e n c e h t 2 . 0 0 m
close boarded fence ht 2.00m
c l o s e b o a r d e d f e n c e h t 1 . 8 0 m
c l o s e b o a r d e d f e n c e h t 1 . 8 0 m
wire m
esh fence h
t 2.0
0m
wire m
esh fence h
t 2.0
0m
wir
e m
esh fence h
t 2.0
0m
site
hoard
ing h
t 2.5
0m
site
hoard
ing
ht 2.5
0m
site
hoard
ing
ht 2.5
0m
B R
O A
D W
A T
E R
R
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D
t a r
m a
c
t a r
m a
c
gra
ss
gra
ss
gra
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t a r
m a
c
t a r
m a
c
shru
b b
ed
S/B
CP
S
S/B
CP
S
IRF
ht 1.0
0m
IRF
ht 1.0
0m
brick paviors
dense foliage
brick
build
ing
u n
s u
r f a c
e d
u n
s u
r f a c
e d
u n s u r f a c e d
100
100
100100
IL 84.50
CB
F h
t 2.0
0m
S/B
in-filledchamber
CLF ht 1.80m
concrete slab
85.3
9
approximate fence line
concre
te p
avi
ng s
labs
electricity sub-station
g r a
s s
ele
ctr
icity
sub-s
tatio
n
soil
s o i
l
LP
brick w
all
ht 1.8
0m
h 10m
S T
R E
E T
S
C E
N E
E
L E
V A
T I O
N
P
P
PP
PP
P
P
P
P
ST
ST
ST
LP
LP
LP
LP
SP
GY
GY
GY
RS
2
3
4
30
212400N
212450N
RL 9
5.8
0
RL 9
5.7
7
85.1
3
85.3
0
85.4
2
85.6
3
85.8
7
86.0
7
86.2
0
86.3
7
86.5
5
86.7
7
87.0
087.1
287.0
5
86.8
9
86.4
8
86.3
1
86.1
6
85.9
2
85.7
8
85.5
0
85.4
4
85.2
7
MH
CL 8
6.0
7
86.9
2
86.6886.85
87.1
08
7.1
7
87.2
08
7.1
687.1
6
86.8
9
86.78
86.66
86.7
8
86.6
5
86.4
9
86.4
1
86.2
2
85.9
1
85.7
2
85.5
7
85.5
8
85.4
2
85.5
4
85.3
585.3
685.1
6
85.8
7
85.6
2
85.4
8
85.3
4
86.6
7
86.4
9
86.7
6
86.9
0
RF
L 8
9.9
9
RF
L 9
5.3
5
RL 94.88
EL 92.49
RL 9
5.3
3
RL 9
8.9
5
RF
L 9
4.3
0
PW
L 9
5.0
9
RFL 93.77
85.3
8
85.
44
85.5
0
85.9
2
86.4
8
86.5
0
86.86
87.05
87.04
87.08
87.17
87.15
87.0
9
87.1
0
86.0
8
MH UTLCL 85.85
86.33
87.12
86.74
86.69
86.78
86.85
86.63
86.48
86.42
86.41
86.28
86.3
5
86.1
5
85.9
5
85.6
0
85.5
9
85.3
285.4
9
85.6
8
86.0
8
86.2
6
86.4
7
86.40
86.53
86.49
86.58
85.9
4
85.7
7
85.8
4
85.65
85.66
85.68 85.65
85.6
4
85.61
1
25
DROP-OFF
5
10
20
MAINENTRANCE
Bro
ad
wa
ter
Ro
ad
28.5m
27m
21m
30m
24m
26.5
m
26m
RESIDENTIAL
DEVELOPMENT
3 storey residential unit
with limited windows in
end elevation
3 storey residential units with
habitable rooms facing site
Tree/soft planting buffer
zone outside site
Tree/soft planting buffer
zone outside site
AMENITY
GARDEN
85.87
15
ele
ctr
icity
sub-s
tatio
n
SERVICE
ENTRANCE
Change in surface
treatment to dedicated
pedestrian traffic route.
Footpath over RPA to be a
no-dig construction method
Cellweb or similar.
16
26
27
28
33
CS
Lighting
h 6m
Oak
h 6mOak
h 6mOak
h 12mApprox Position
h 12m
Approx Positionh 12m
Approx Position
h 12m
Approx Position
h 12m
Approx Position
h 12mApprox Position
h 10m
Sycamore
h 4mMultibole
h 12mSycamore
h 12m
Sycamore
h 12m
Sycamore
h 10m
h 10mSycamore
h 10m
Sycamore h 10mSycamore
h 8m
Sycamore
h 14mSycamore h 10m
Sycamore
h 12m
h 12m
h 8m
h 16m
h 10m
h 12m
h 12m
h 12m
h 10m
h 10m
h 10m
h 10mSycamore
h 12mSycamore
h 12m
h 8mMultibole
h 8m
Multibole
PROPOSED
CARE HOME
4 Storeys
REFUSE
STORE
No habitable/resident windows
at upper levels in end elevation
Windows to be provided at
corridor ends
N
Marbrook
NOTES
1. Scheme design is subject to relevant
Statutory Approvals.
2. Drawing based on topographical survey
ref: TS18-448X1.
3. Tree information based on Arboricultural
Survey ref. BS5837.
4. Refer to Deacon Design information for
landscaping and materials.
5. Refer to Canham Consulting information
for levels.
KEY
PARKING
33 car parking spaces
incl. 3No. disabled
GIA m²
Ground Floor 1490
First Floor 1477
Second
1313
Beds/
Suites
27
31
32
Units
2
2
2
Third Floor
1455
90 Beds/
13 Suites
1
TOTAL BEDS/SUITES & GIA
5735
SCHEDULE OF ACCOMMODATION:
CARE HOME
13
Site Boundary
Previous Consent Footprint
Existing Buildings
Proposed Building
Vehicular Access & Parking
Paths
Patio Areas
Existing Tree - Retained
Existing Tree - Removed
Tree Root Protection Area
New Tree
Cycle Shelter - 8 Spaces
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DRAWING NO. revision
CLIENT
PROJECT
DRAWING TITLE
T: 0151 207 4371 ● F: 0151 207 7087
Construction
For Approval
Tender
Preliminary
REVISION DETAILS date / by
NOTES
MATERIALS PROHIBITED
C
SCALE drawn by date
This drawing is copyright of Condy and Lofthouse Ltd. and may not be reproduced in
any way without their specific permission.
a) high alumina cement in the structural elements;
b) wood wool slabs in permanent formwork to concrete;
c) calcium chloride admixtures for use in reinforced concrete;
d) asbestos or asbestos-containing products, as defined in the 'Control of Asbestos at
Work Regulations, as amended 2012' or any other statutory modification or re-
enactment thereof;
e) any naturally occurring or man made mineral fibres (for example, rock-wool or slag
wool) with a thickness of 3 microns or less and a length of 200 microns or less, unless
they are appropriately sealed to prevent migration of fibres;
f) aggregates for use in reinforced concrete which do not comply with:
'BS EN 12620:2002: properties of aggregates used in concrete.
'BS EN 13139:2002: Properties of aggregates used in mortar.
'BS EN 13055 (Parts 1 & 2): properties of lightweight aggregates.
'Guidance on avoiding alkali-silica reaction and limitations on alkali content in
BRE Digest 330 (2004)' & 'Concrete Society Technical Report 30 (1999)';
g) lead, lead paint or any other materials containing lead which may be ingested,
inhaled or absorbed, except where copper alloy fittings also containing lead are
specifically required in drinking water pipework by any relevant statutory requirement
or where lead flashings or other lead roof coverings are specifically provided for in the
Contract;
h) urea formaldehyde foam or materials which may release formaldehyde in quantities
which may be hazardous with reference to the limits set by the Health and Safety
Executive;
i) calcium silicate bricks or tiles;
j) vermiculite unless it is established as being fibre-free; calcium silicate bricks or tiles;
k) any products containing cadmium referred to in Statutory Instrument 'SI 2006/3311
Controls on dangerous substances and preparations Regulations 2006'. Reference
should also be made to 'HSE IDGE391 Cadmium and you';
l) any new timber treated with pentachlorophenol;
m) non galvanised mild steel structural fixings for building elements particularly susceptible
to erosion;
n) concrete used in circumstances where it is susceptible to alkali/silica reaction;
o) materials containing chlorofluorocarbons (CFC's);
p) solvent based paints except where water based paints are unsuitable for unavailable;
q) any new materials not in accordance with statutory requirements, British Standards,
Codes of Practice and good building practice current at the date of incorporation of
the relevant materials into the Works or the specifications thereof;
Materials prohibited from use, except where used in accordance with 'Good Practice in
the Selection of Construction Materials (March 2011)' or unless required by the Contract:
1:200@A1 CS 03.08.2018
17-132-110
Proposed Site Plan
Broadwater Road
Welwyn Garden City
AL7 3AX
CS
SITE PLAN - AS PROPOSED
0 10
Scale Bar
5 20 Metres15 0 10
Scale Bar
5 20 Metres15 J
Sub-station indicated.A 17.12.2018
'Do Not Scale' notation omitted.B
17.01.2019
'Car parking spaces out of use
during refuse collection' notation
omitted based on Mayer Brown
drawing no. BPWELWYNGC.1/TK10.
C
30.04.2019
GIA increased by 5m² due to Third
Floor balcony redesign as agreed
with Planning on 16.05.2019.
D
17.06.2019
D
17.06.2019
E Frontage trees revised. 04.08.2019
F Existing Oak tree retained and
access footpath and parking
amended to suit. 16-07-2020
G Drop off zone and parking
amended to suit client
comments [meeting with PS
11-08-2020] 13-08-2020
H Main entrance moved and
parking amended to suit [PS
email 30-11-2020]
DD layout shown to amenity
garden 01-12-2020
TENDER ISSUE
I - Levels removed and note
added to refer to Canham info
- Shrubs removed from key and
noted added to refer to Deacon
Design info 15-01-2021
J Hard standing areas amended
to reflect Deacon Design info
08-02-2021
NB: Positions of Boreholes and/or Trial Pits are only indicative
Site: Broadwater Road, Welwyn STL: JN1576 Fig No: 1
Date: 3rd June 2021 Fieldwork Locations
TP2TP2TP2TP2
SSSStockpile tockpile tockpile tockpile samplessamplessamplessamples
SESSESSESSES
Southern Testing: Keeble House, Stuart Way, East Grinstead, West Sussex RH19 4QA ST Consult: Twigden Barns, Brixworth Road, Creaton, Northampton NN6 8NN
TP1TP1TP1TP10000
TP9TP9TP9TP9
TP6TP6TP6TP6
TP7TP7TP7TP7
TP5TP5TP5TP5
TP4TP4TP4TP4
TP1TP1TP1TP1
TP8TP8TP8TP8
SENSENSENSEN
TP3TP3TP3TP3
APPENDIX B
Verification Criteria
Contaminant Screening Values for Imported Soils
Contaminant Units
Proposed Land Use
Residential with homegrown produce
consumption
Residential without
homegrown produce
consumption
Open Space* (Residential)
Open Space* (Park)
Allotments Commercial / Industrial
Arsenic (As) [2] mg/kg 37 40 79 170 43 640
Cadmium (Cd) [2] mg/kg 11 85 120 555 1.9 190
Trivalent Chromium (CrIII) [2] mg/kg 910 910 1,500 33,000 18,000 8600
Hexavalent Chromium (CrVI) [2] mg/kg 6 6 7.7 220 1.8 33
Lead (Pb) [3] mg/kg 200 310 630 1300 80 2330
Mercury (Hg) [1,2,7] mg/kg 7.6-11 9.2-15 40 68-71 6.0 29-320
Selenium (Se) [2] mg/kg 250 430 1,100 1,800 88 12,000
Nickel (Ni) [1,4] mg/kg
pH<6.0 60
pH 6.0-7.0 75
pH>7.0 110
Copper (Cu) [1,4] mg/kg
pH<6.0 100
pH 6.0-7.0 135
pH>7.0 200
Zinc (Zn) [1,4] mg/kg
pH<6.0 200
pH 6.0-7.0 200
pH>7.0 300
Phenol [1,2] mg/kg 120-380 440-1200 440-1300 440-1300 23-83 440-1300
Benzo[a]pyrene [1,5] mg/kg 1.7-2.4 2.6 4.9 10 0.67-2.7 36
Naphthalene [1,2] mg/kg 2.3-13 2.3-13 77-430+ 77-430+ 4.1-24 77-430+
Total Cyanide (CN) [6] mg/kg / / / /
Free Cyanide [6] mg/kg / / / /
Complex Cyanides [6] mg/kg / / / /
Thiocyanate [6] mg/kg / / / /
Asbestos - None detected None detected None
detected None
detected None
detected None detected
Notes:
* Open Space levels calculated on the basis of the exposure modelling developed in the C4SL research.
+ Screening values constrained to saturation limit. Higher values may be acceptable on a site specific basis.
[1] Where ranges of values are given for organic contaminants, the screening value is dependent on the Soil Organic Matter. Where ranges are given for inorganic contaminants, the screening value is dependent on the pH.
[2] LQM/CIEH S4UL (2014). Copyright Land Quality Management Ltd reproduced with permission; Publication Number S4UL 3116. All rights reserved.
[3] C4SL (DEFRA 2014).
[4] Copper Zinc and Nickel may have phototoxic effects at the GAC or SGV concentrations and alternative criteria are given for importation of Topsoil or other soils for cultivation, based on BS3882:2015 (Topsoil) and BS8601:2013 (Subsoil).
[5] Based on the Surrogate Marker approach and modelled using the modified exposure parameters of C4SL but retaining ‘minimal risk’ HCV.
[6] Usually Non-Detect concentrations. Screening criteria to be derived on a site specific basis if test results indicate.
[7] SGV/GAC for Methyl Mercury, higher concentrations may be tolerable if inorganic mercury is the only species present. Lower concentrations apply for elemental mercury.
These screening values are valid at the time of writing but may be subject to change. Their validity should be confirmed at the time of site development.