Contaminated land planning guidance

This guide helps people (including developers, landowners, and consultants) applying to build on or near potentially contaminated land in the borough of Reigate & Banstead. The information is aimed to be used as a guide only as conditional wording may and does change depending on legislation revisions, the size and nature of sites and development plans.

Contaminated land

Below is an example of typical contaminated land planning conditions that we (Environmental Health) may choose to recommend to the Local Planning Authority for sites that are on or near contaminated land. The conditions are set to enable a phased approach to contaminated land investigations. Beneath each conditional requirement we have provided some further guidance on what we would typically expect information submitted for discharging a condition to comprise.

1. Environmental desktop study report

Prior to the start of the development a written comprehensive environmental desktop study report is required to identify and evaluate possible on and off site sources, pathways and receptors of contamination and enable the presentation of all plausible pollutant linkages in a preliminary conceptual site model. The study shall include relevant regulatory consultations such as with the Contaminated Land Officer and be submitted to the Local Planning Authority and is subject to the approval in writing of the Local Planning Authority and any additional requirements that it may specify. The report shall be prepared in accordance with the Environment Agency’s Model Procedures for the Management of Contaminated Land (CLR 11) and British Standard BS 10175.

The above requires the completion of a desktop study report. Unless stated it is usually expected that a full Phase 1 desktop study report is required to be completed in accordance with CLR11 and BS 10175. It should be noted that should the risk assessment identify a suitably low risk then there is the potential, with the exception of the unexpected ground contamination condition, that the remainder of the conditions are not required to be fulfilled. This discussion ultimately rests with the Local Planning Authority.

Key points to include in your report:

• site history
• site setting (location, surroundings, topography etc)
• site usage (including adjacent site)
• site geology, hydrogeology, geochemistry, hydrology
• site ecology and archaeology
• future plans for site
• regulatory consultations (e.g Environmental Health, Petroleum Officer, Environment Agency etc)
• site reconnaissance, detailed description of site, layout, visual and olfactory evidence of contamination
• conceptual site model
• review and comment on any previous environmental reports pertaining to the site
• preliminary risk assessment
• identification of potential contaminant sources, pathways and receptors (pollution linkages)
• conclusions and recommendations

2. Contaminated land site investigation proposal

In follow-up to the environmental desktop study report and prior to the start of development, a contaminated land site investigation proposal, detailing the extent and methodologies of sampling, analyses and proposed assessment criteria required to enable the characterisation of the plausible pollutant linkages identified in the preliminary conceptual model, shall be submitted to the Local Planning Authority. This is subject to the written approval in writing of the Local Planning Authority, and any additional requirements that it may specify, prior to any site investigation being commenced on site. Following approval, the Local Planning Authority shall be given a minimum of two weeks written notice of the commencement of site investigation works.

The above condition requires the completion of site investigation proposal to be submitted in writing to the Local Planning Authority. This proposal needs to be suitably detailed for the scale of works and extent of the site in question. The proposal will detail how you plan to investigate the site in question and include but not necessarily limited to:

• set aims and objectives of the site investigation
• number, type (e.g. window sampler/shell and Auger/Mechanical investigation) location and rationale for investigation locations
• soil and/or water sampling suites to be undertaken, number of samples proposed, sampling strategy etc
• any onsite screening/testing proposed e.g. use of PID for screening site soils
• ground gas monitoring proposed? If so how many visits are proposed and over what time period etc
• when will the works be undertaken, the condition requires giving the Local Authority a minimum of two weeks written notice of the commencement of site investigation works. This is so that we can undertake a site visit to see the works in progress if required.

3. Contaminated land site investigation and risk assessment

Prior to commencement of the development, a contaminated land site investigation and risk assessment, undertaken in accordance with the site investigation proposal as approved that determines the extent and nature of contamination on site and is reported in accordance with the standards of DEFRA’s and the Environment Agency’s Model Procedures for the Management of Contaminated Land (CLR 11) and British Standard BS 10175, shall be submitted to the Local Planning Authority and is subject to the approval in writing of the Local Planning Authority and any additional requirements that it may specify. If applicable, ground gas risk assessments should be completed inline with CIRIA C665 guidance.

Key points to include (having already provided a minimum of two weeks written notice of the commencement of site investigation works). The Site Investigation phase is the on-site validation of the Conceptual Site Model. Its purpose is to refine and update the Conceptual Site Model, confirm pollutant linkages and evaluate potentially unacceptable risks. It should include an intrusive investigation, chemical testing and a quantitative risk assessment.

Intrusive testing report should include:

• a plan of the site showing, exploration locations, locations of site structures
• justification of exploration locations
• justification of the sampling and analytical strategies chosen
• description of the methods used for collecting, preserving and transporting samples
• borehole/trial pit logs
• discussion of ground conditions
• conceptual site model
• risk assessment/site specific risk assessment
• details of any model input parameters and calculations
• details of constraints and limitations of the data and risk assessment
• identification of unacceptable pollution linkages
• signed laboratory certificates of analysis
• set the scene and summaries background to the site (identified from the desktop study)

4a. Detailed remediation method statement/strategy

Prior to the start of the development a detailed remediation method statement/strategy should be produced that details the extent and method(s) by which the site is to be remediated, to ensure that unacceptable risks are not posed to identified receptors at the site and details of the information to be included in a validation report, has been submitted to and approved in writing by the Local Planning Authority, and any additional requirements that it may specify, prior to the remediation being commenced on site. The Local Planning Authority shall then be given a minimum of two weeks written notice of the commencement of remediation works.

The above requires the completion of a suitably detailed remediation method statement or strategy should contamination be identified during the site investigation that requires subsequent remediation. It is very importance that information is provided on what will be included in a validation report also. We would expect this to be reasonably detailed in nature and include, but not limited to the following key points:

• description of ground conditions
• setting of remediation objectives
• type, form and scale of contamination to be remediated
• remediation methodology
• site plans and drawings (if applicable)
• phasing of works and timescales for completion
• consents and licences (if applicable)
• site management measures to protect neighbouring sites and wider environment during the works
• details of how the works will be validated to ensure remediation objectives have been met e.g. x amount of samples per plot or per m3, hand dug pits with photographs of tape measure to show final depth of clean fill, stating remedial targets/importation criteria etc.

4b. Remediation validation report

Prior to occupation, a remediation validation report for the site shall be submitted to the Local Planning Authority in writing. The report shall detail evidence of the remediation, the effectiveness of the remediation carried out and the results of post remediation works, in accordance with the approved remediation method statement and any addenda thereto, so as to enable future interested parties, including regulators, to have a single record of the remediation undertaken at the site. Should specific ground gas mitigation measures be required to be incorporated into a development the testing and verification of such systems should be in accordance with British Standard BS 8485:2015 and CIRIA C735 guidance document entitled ‘Good practice on the resting and verification of protection systems for buildings against hazardous ground gases’.

The above requires the completion and submission of a remediation validation report. This is a very important part of the investigation process as it provides key information and confidence to the Local Authority to demonstrate that the site is suitable for its new use in accordance with the requirements of the NPPF.

• details of who carried out the work
• details of the type, form and scale of contamination that was remediated
• details and justifications of any changes from the original remediation statement or strategy
• details of substantiating data such as signed laboratory results, ground gas monitoring results (if applicable) plans showing areas treated, waste management documentation, photographs showing works undertaken inc. evidence of clean soil depths (if required).

It is expected that the validation report would include key and relevant information carried through from the remediation method statement or strategy. For example if the remediation strategy states that validation samples will be undertaken at a rate of 100m3 of clean imported soil, the Council would expect this to be carried out or if the strategy states that a minimum clean cover system of 600mm will be provided in garden areas then we would expect on average for the applicant to demonstrate this has been achieved.

Should ground gas protection measures be required the Local Authority utilises both British Standard BS 8485:2015 and CIRIA C735 guidance document entitled ‘Good practice on the resting and verification of protection systems for buildings against hazardous ground gases’ for assessing protection systems are fit for purpose and been installed to an acceptable standard.

5. Unexpected ground contamination

Contamination not previously identified by the site investigation, but subsequently found to be present at the site shall be reported to the Local Planning Authority as soon as is practicable. If deemed necessary development shall cease on site until an addendum to the remediation method statement, detailing how the unsuspected contamination is to be dealt with, has been submitted in writing to the Local Planning Authority. The remediation method statement is subject to the written approval of the Local Planning Authority and any additional requirements that it may specify.

The above requires the applicant to report instances of when unexpected ground contamination was identified during development works in order for an assessment to appraise whether any revisions to the remediation method statement or strategy is required.

If no unexpected ground contamination was identified during the development works then the applicant shall provide a brief written statement to this effect to enable discharge of this condition.