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Wiltshire Council Planning Guidance

Wiltshire Council planning policy for sustainable drainage reports, flood risk assessments and contaminated land risk assessment are driven by environmental conditions and the local authority policy.
Guidance for architects, and developers on flood risk, drainage and phase 1 contaminated land reports is summarised below with links to the key summary documents.

Wiltshire Council Contaminated Land

Contaminated Land assessments may be required, even in localities which appear relatively unpolluted and undeveloped depending on the proposed land use. Even ‘green field’ sites may have a hidden history which is only revealed by some sort of investigation.

Wiltshire Council intends that such investigations should be proportionate, realistic and cost effective and so developers are advised to use the checklists provided in their appendices in determining what, if any, assessment is needed.

It is recommended that developers seek specific advice from the environmental protection team prior to any formal planning application if land contamination is likely to be an issue.

Typical site assessments would consist of one or more of the phases summarised below:

  1. Phase 1 Investigation (Desk Study, Walkover and Preliminary Risk Assessment)

The desk study element of a Phase 1 investigation typically comprises an assessment of the historic land use usually obtained from historic maps, known local issues such as landfill sites, pollution incidents, water abstractions, known contaminative uses etc. The geology and hydrology of the site is determined either from a commercial source or from the British Geological mapping series. The likely on and offsite receptors are identified and discussed in the context of the proposed development.

The above information is used to produce a qualitative or preliminary risk assessment within the body of the Phase 1 report.

At this point the Phase 1 Investigation report may demonstrate and conclude that:

1) The site appears likely to be free from contamination and that no investigation i.e. a Phase 2 Assessment is warranted or;

2) That there are one or more potential contaminant linkages that require further investigation.

  1. Phase 2 Investigation (Intrusive Investigation or Ground/Site Investigation)

Phase 2 Investigations require the physical investigation of the conditions present in or on the land, water and buildings present at a site.

  1. Remediation Scheme

The remediation scheme draws on the results of the site investigations and risk assessment to identify how land contamination risks can be managed.

  1. Site Validation

Once the remedial works are completed a site validation report will need to be produced and provided to the local planning authority to demonstrate that the works were completed as agreed.

It is preferable that all basic investigations into land contamination have been completed prior to the submission of a planning application or request preapplication advice. At the very least a desk study should be considered.

Site Walkover Reconnaissance

A site walkover should be undertaken at the Phase 1 stage to confirm the current visual and sometimes olfactory status of the site; observing the condition of vegetation, watercourses, buildings and the presence of storage tanks, pipe work etc. and other infrastructure associated with the former land use if still present and visible.

Guidance for Contaminated Land

Wiltshire Council

VIEW WILTSHIRE GUIDANCE FOR CONTAMINATED LAND

Wiltshire Council Flood Risk Assessment

Flooding is a serious issue in Wiltshire, with extensive flooding in the north of the county taking place in 2007 and 2008, and more recently across the whole county in 2014, when over 500 properties were affected.

The requirement to undertake a site-specific FRA to support applications for development proposed in flood risk areas or where proposed development may increase flood risk to third parties applies under the National Planning Policy Framework (NPPF) for Wiltshire.

The NPPF states that site-specific FRAs are required to accompany planning applications for sites:

  • within Flood Zones 2 or 3;
  • or where the site lies within Flood Zone 1 and is greater than 1 hectare in area,
  • or is in an area in Flood Zone 1 which has critical drainage problems (as notified to Wiltshire by the Environment Agency).

The NPPF states that site-specific FRAs should be carried out to the appropriate degree, at all levels of the planning process and to inform the application of the sequential approach. They should assess the risks of all forms of flooding to and from development, taking climate change into account.

It is the responsibility of applicants to consider the flood risk to a site, as early as possible. Applicants should refer to the SFRA at the start of the pre-application stage, or if this is not carried out, at the earliest stage in the preparation of development proposals and a planning application.

A site-specific FRA will need to demonstrate that flood risk to the development can be managed now and over the lifetime of the development for all sources of flooding. It should show that the development is safe. A site-specific FRA should demonstrate also that the development does not increase the risk of flooding to third parties from all sources and that the proposals are compliant with local planning policy. Where possible the development should aim to reduce flood risk overall, and the site-specific FRA should demonstrate this where it is the case.

Level 1 Strategic Flood Risk Assessment

Wiltshire Council

VIEW WILTSHIRE STRATEGIC FLOOD RISK ASSESSMENT

Wiltshire Council Sustainable Drainage SuDs

Wiltshire Council’s approach is to ensure that there is effective management of surface water, on all sites, but particularly on those where proposed redevelopment is likely to present significant opportunities for improvement and the achievement of sustainable development. This approach will reduce pressures on the existing drainage infrastructure and reduce the risk of surface water flooding and pollution.

Pre-application discussions are strongly encouraged to ensure that all drainage matters are given adequate consideration from an early stage.

The current position requires a developer to submit a ‘Flood Risk Assessment’ and ‘Drainage Strategy’ to the planning authority alongside a planning application. Wiltshire Council is the lead organisation for determining whether proposals comply with the planning policies. During the

determination period they will consult with other consultees such as your water and sewerage provider and the Environment Agency.

All applications for planning permission will need to be accompanied by a formal submission for Wiltshire Council approval in the form of a drainage application. This application is made up of a form to accompany the developers detailed drainage design. The application will incur a separate fee to that of the planning application fee.

Determination of the planning application should take place in parallel with the drainage application.

If a development is allowed under ‘permitted development’ rights but falls within the requirement for SuDS approval, a formal submission to Wiltshire Council will be required, but it is expected that the SuDS application will be simplified. Guidance on this will be confirmed. Once a drainage application has been registered, Wiltshire Council will consult on the application with the responsible organisations, and any other bodies who may be affected by or have an interest in the proposals.

Wiltshire Council will notify the planning team of its decision who will then issue the decision notice(s) to the applicant. Wiltshire Council’s decision notice may contain conditions relating to:

  • The construction of the drainage system. Details must be in accordance with the approved design and information must be submitted relating to construction including materials and specifications;
  • Receipt of a Non- performance bond to be received prior to commencement of construction to protect Wiltshire Council if the drainage were not to perform correctly;
  • Notifying Wiltshire Council of your intention to commence construction including provision of a programme of works to enable appropriate inspections to be arranged;
  • All fees to be paid in relation to work undertaken in connection with approval and construction.

Drainage Strategy

The drainage strategy can be viewed as a hierarchy, or sequential approach. This means that, in order to discharge directly to a receptor (i.e. surface water sewer); developers will be expected to have demonstrated that they have explored all of the sustainable measures first. In existing guidelines, this principle is known as a ‘SuDS management train’.

Developer’s guidance note on floods, drainage and SuDS

Wiltshire Council

VIEW WILTSHIRE DEVELOPER'S GUIDANCE NOTE ON SUDS

Wiltshire Council Groundwater Flood Risk

Groundwater flooding occurs as a result of water rising to the surface from the underlying rock strata, known as aquifers. Groundwater flooding within Wiltshire mainly occurs in the south of the county, due to the nature of the underlying chalk deposits, when the water tables are high, and additional rainfall causes the aquifers to fill and the water to rise out of the ground. This type of flooding can continue for weeks, even months, as until the groundwater levels start to drop the water remains on the surface.

The areas most susceptible to groundwater flooding in Wiltshire are in the south and south-east of the county, which are on the chalk aquifer, but there are areas in the north of the county that are also susceptible to groundwater, particularly those areas underlain by sand and gravel deposits.

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