If you would like to use a this letter we have produced which covers many of the core objections to the speculative Home Farm development plans, please copy and paste all the text below into the comments box on the Wiltshire Council page. You will need to complete the rest of the form with your details to register your objection.
Planning Application: PL/2026/02717
Site Address: Land at Home Farm, Boreham Road, Warminster
Objection by:
Address:
Date:
Dear Wiltshire Council,
I am writing as a local resident to object to the above planning application. This planning objection relates primarily to the proposed surface water drainage strategy and its deliverability. This is a concern as we are residents within the vicinity of the River Wylye where existing land is already within areas of high flood risk.
Whilst the drainage strategy relies on infiltration basins and swales, the effectiveness of these SuDS features is uncertain during the winter periods and high groundwater conditions. If this proposed drainage strategy is insufficient during these periods, exceedance flows could potentially be directed towards the River Wylye to the south, increasing flood risk to our property.
The submitted Flood Risk Assessment states that the drainage strategy relies on infiltration basins and swales to attenuate up to the 1 in 100 years plus 45% climate change event. This same report highlights the groundwater vulnerability within the south of the site with groundwater monitoring to be conducted during the winter period. Significant changes to the drainage strategy would be required if high seasonal groundwater levels are recorded on site.
The full drainage strategy relies on the confidence of unknown groundwater monitoring results.
Furthermore, the submitted information lacks sufficient engineering information. Additional drawings appear to be missing from the submitted documents including road, sewer and basin long sections that should demonstrate the development is technically deliverable.
On this basis, I do not consider the submitted information to be sufficient for a full planning application and therefore object to the proposed development (Land at Home Farm, Boreham Road, Warminster). Further details of the reason for the objection are seen below:
Groundwater and Infiltration Basin Viability
The main concern in the drainage strategy is the reliance on infiltration to ground while the site has been identified as sensitive to groundwater flooding despite monitoring not being completed. BRE365 compliant percolation testing has been conducted on site with results largely indicating low infiltration potential. Locally identified infiltration rate of 2.30×10-5 m/s was found in the deeper BHC sand in Zone 3 at SA4 where Basin A is proposed. The FRA states that the base of the infiltrating SuDS features should be a minimum of 1.0m above groundwater level. The basin has been proposed at a depth of 1.50m – 2.30m to access the permeable BHC sand. The greater depths increase the risk with seasonal groundwater levels where the unlined infiltration basin volume could be reduced, and the localised infiltration rate interrupted due to saturation. The consequence of the infiltration basins failing to provide adequate storage volumes could be increased flood risk to neighbouring properties, Boreham Road or the River Wylye.
Furthermore, Basin B has been proposed to drain the site access with the same infiltration rate as Basin A. The ground investigation conducted percolation test SA8 where Basin B is proposed which failed to calculate an infiltration rate. This will increase the risk of flooding that occurs on Boreham Road as exceedance flows from Basin B will flow to the south. The applicant should provide the groundwater monitoring results and refine the infiltration rates before the application is determined as significant changes to the drainage strategy may be required.
Lack of integrated engineering information
As this is a full planning application sufficient engineering information should be provided that demonstrates the deliverability of the development. It is understood that construction details will be provided in detailed design / condition stage, however the submitted information is lacking key information.
The submitted information does not provide an integrated engineering drawing package including the proposed drainage, road levels, finished floor levels, basin levels and existing ground levels. The application includes a Concept Levels Strategy and Drainage Strategy included within the FRA, however this split makes it difficult to confirm technical deliverability for the proposed site. Several of the submitted engineering drawings such as the Proposed Drainage Strategy and Concept Levels Strategy appear to be marked as draft or preliminary, which does not provide sufficient certainty for a full planning application of this scale and technical sensitivity.
Additional drawings appear to be missing from the submitted documents including road, sewer and basin long sections. This is significant information for planning as it highlights road design, manhole depths, pipe clashes, pipe gradients, basin sections and basin water levels. Road long sections are required to assess the proposed vertical alignment is deliverable for the proposed development. Vertical curve values and the tie-in to the existing Boreham Road access/highway levels cannot be reviewed.
As the drainage strategy relies on an infiltration basin in an area of identified existing surface water ponding a basin cross section should be required. Without a basin cross section, the freeboard and earthworks design to existing levels cannot be verified increasing the concern due to the groundwater uncertainty and exceedance flows.
The applicant should provide coordinated planning-stage engineering drawings including road, sewer and basin long sections to demonstrate the development is deliverable. Without this information the LLFA and highway authority cannot assess whether the development follows the relevant guidance.
Existing surface water catchments and southern ponding area
The submitted FRA does not clearly identify the existing surface water catchments that contribute to the surface water ponding located in the southwest of the site. The proposed basins appear to provide storage primarily for the proposed impermeable development in the north of the site. The existing low point which leads to ponding and flood risk on site could occur due to surface water from the west where limited formal drainage has been proposed. The applicant should provide an existing hydrology plan in the FRA that demonstrates existing overland flows and how the existing ponding area will be intercepted and managed through the drainage strategy. This will demonstrate that the development will not alter the existing overland flow routes or increase flood risk to neighbouring properties or Boreham Road.
Refuse and layout serviceability
The Transport Assessment highlights some bin collection points that exceed the resident carry distances. The applicant should provide an updated refuse strategy that demonstrates that all plots are compliant with carry and collection distances.
Conclusion
Overall, the submitted information does not demonstrate a technically deliverable development for a full planning application. The following information should be provided and reviewed before the application is determined:
- Groundwater monitoring results and groundwater addendum
- Basin cross-section drawings including ground levels, basin levels, side slopes, water levels, freeboard and peak groundwater levels.
- Confirmation that the base of the SuDS features is at least 1.0m above peak seasonal groundwater levels.
- Revise Basin B infiltration rate.
- Existing surface water catchment plans including overland flow routes for the southwestern area of the site due to existing surface water flooding occurring on site.
- Road and sewer long sections including gradients, manhole levels, vertical curve values and tie-in to existing ground levels.
- A combined drainage and levels strategy showing the road levels, finished floor levels, sewer levels, manhole depths and exceedance routing.
- A fallback drainage strategy if infiltration is not confirmed as viable following groundwater monitoring.
The submitted documents do not provide confidence that the site would be safe from flooding for the lifetime of the development and not increase flood risk to neighbouring areas such as Boreham Road and the River Wylye. The proposed development cannot be properly assessed by Wiltshire Council and local residents without the required information.