1)
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CONTAMINATION INFORMATIVE 1
The applicant is reminded that condition 22 (Contamination - Site investigation and
quantitative risk assessment) remains to be discharged until a sufficient site
investigation and quantitative risk assessment report is submitted in accordance with the
requirements of the condition that includes works set out in the letter from Fairhurst for
66-74 Notting Hill Gate - Scheme of Investigation (Ref: CB/HB/117485/NHG/SchemeofInvestigation/RevA),
dated 22 November 2018 andapproved by this authority.
The applicant needs to ensure the consultants are aware of
issues identified in the submissions for condition 21 and these issues are adequately
addressed towards ensuring condition 22 requirements are fully met.
The following needs to addressed as part of condition 22:
(a) A potential limitation to the investigation is apparent based on the proposal, and
following completion of the proposed investigation any shortcomings from the
investigation will have to be addressed to ensure a sufficient investigation has been
undertaken in order to adequately complete quantitative risk assessment. This
includes the limiting of the current ground gas monitoring to three round to the
south east of the site and the absence of any ground gas/vapour monitoring to the
north of the site due to site constraints.
(b) The indoor continuous monitoring appears to be limited to methane and TVOCs. It is
recommended indoor monitoring of gases include all likely gases that need to be
considered, including hydrogen sulphide (based on sewer pipe and manhole cover
indicated in the basement area). The use of thermal desorption tubes to speciate
VOCs is noted.
(c) Please ensure any the PID screening data is provided in the report to discharge
condition 22. Valid calibration certificates for the equipment used to complete the
ground gas and vapour monitoring, with relevant lamp details should be included in
the report to discharge condition 22.
(d) Any groundwater source vapour risk assessment using SOBRA (2017) would have to
clearly set out the site specific conditions and compare it to the modelled SOBRA
conditions to demonstrate it is appropriate and at the very least suitably
conservative criteria to use. The risk assessment as a whole still needs to consider
all sources vapour identified in the PRA.
(e) Prior to completing the site investigation, it is recommended the limit of detection
achievable, particularly with regard to VOCs is checked with the laboratory to ensure
it is as low as practicable and below the appropriate contamination criteria used for
soils and groundwater.
(f) Table 1: Generic Assessment Criteria for soil samples collected in area of soft
landscaping - it is noted not all the criteria in the table are suitable for soils used for
landscaping purposes. It is recommended in addition to the risk based criteria in the
table a total capped value for TPHs and PAHs is used to prevent gross
contamination remaining untreated for onsite and imported soils. A total TPH capped
value of 500 mg/kg and Total PAHs capped value of 20 mg/kg is recommended. A
note to the criteria table should make clear how these values are to be used
alongside the risk based values.
Please contact the Environmental Quality Unit ([email protected]) for further clarification
on requirements.
2)
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CONTAMINATION INFORMATIVE 2
The applicant is reminded that condition 23 (Contamination - Remediation Method
Statement) remains to be discharged until a sufficient site investigation and quantitative
risk assessment report is submitted in accordance with the requirements of the condition
22 and a remediation method statement based on the findings of the risk assessment and
the requirements of condition 24 (Verification Report) relevant to the final development is
submitted and approved by this authority. The applicant needs to ensure the consultants
are aware of issues identified in the submissions for condition 21
(letter from Fairhurst for 66-74 Notting Hill Gate - Scheme of Investigation
(Ref: CB/HB/117485/NHG/SchemeofInvestigation/RevA), dated 22 November 2018)
and these issues are adequately addressed towards ensuring condition 23 requirements
are fully met.
The following also needs to addressed as part of condition 23:
(a) Details of any proposed works relating to water supply pipes investigation, where
this has not been completed, and verification information be provided in due course
needs to be clearly set out in the remediation method statement and verification
plan.
(b) Details of any soils/materials to be imported to site as part of completing any
landscaping works including green roofs and details of how it will be verified needs
to be clearly set out in the remediation method statement and verification plan. Site
won soil or soil imported on to the site which is to be used for planting, landscaped
areas (including under paved areas) and green roofs, shall be sampled at an agreed
frequency (1 per 20m3 for onsite soils and 1 per 50m3 for imported soils as a
minimum) and analysed for contamination against appropriate contamination criteria
for landscaping soils. The criteria in the site investigation scheme is not suitable for
all contaminants will have to be updated as part of the remediation method
statement submission. A verification plan needs to make clear information including
sampling locations/depth, landscaping depth verification, the results of the
contamination analysis, soil provenance details and any other supporting
information shall be submitted as part of the verification report in due course.
(c) Addressing any potential residual risks based on the limitations of the investigation
will need to be clearly set out in the remediation method statement and verification
plan including sealing off of any potential preferential pathways.
Please contact the Environmental Quality Unit ([email protected]) for further clarification
on requirements.