Agenda item

24/03278/FUL Land (e) 431186 (n) 208772 Witney Road.

Meeting of Development Control Committee, Monday, 20th October, 2025 11.00 am (Item 14.)

Purpose:

To consider the application for development, details of which are set out in the attached schedule.

Recommendation:

That the application be determined in accordance with the recommendations of the Head of Planning.

Minutes:

James Nelson, Principal Planner, introduced the item.

In his presentation the Principal Planner made the following points:

The proposal was for construction and operation of a ground mounted solar farm, Battery Energy Storage System (BESS), associated infrastructure, ancillary works and landscaping.
The proposed site included six undeveloped agricultural fields on land south of the A40.
The site had a public right of way through it. It was near designated ancient woodland and listed buildings at Caswell House.
Site access and the BESS facility, including the impermeable attenuation tank, a key measure to contain run off water, were sited at the southern edge of the site.
Proposed landscape and visual mitigation included woodland planting to the southern edge of the site which would contain views of the development from the southwest.
Drainage layout drawings showed the sloping of the site down from the highest point in the north to the southwest corner.
An overview of the appearance and heights of infrastructure was provided and included racks, panels storage containers and the substation. The BESS, substation and panels would be three metres in height.
A control building would be in the southern corner of the site and be five metres in height.
Details of fencing, gates and CCTV were shown.
Photographs of the site from various viewpoints were presented.

The Chair then invited public speakers to address the Development Control Committee.

Richard and Amanda Matthews spoke in objection to the application which raised the following points:

Caswell House was a Grade 2 star listed manor.
The site of Caswell House included a moat. The moat was a heritage asset and was fed by a spring reservoir 500 metres away and was in direct proximity to the site of the proposed BESS. Underground aquifers fed the spring.
Sinking steel supports into the ground was potentially damaging to the aquifers and risked the water supply and subsequently the moat.
There was a colony of fresh-water mussels on the outlet of the moat that would be threatened by the potential water contamination.
The spring was the sole water supply for Caswell House and was incorrectly omitted from the Officer report.
The main risk was from flood and fire water which posed a threat to Caswell House as a business and had environmental and public health risks.
Policy OS2 was relevant to the application decision due to the importance of minimising impact on neighbouring properties.
Careful consideration was needed to the location of BESS units.
Various consultees had been compromised with their findings based on an inaccurate briefing that omitted key information.
Risks of water pollution could not be mitigated.

Josh Rigby, Michael Breslaw and Aiden Van de Weyer, agents for the application spoke in support of the application which raised the following points:

The site would help the move to clean low carbon power.
The inclusion of battery storage enhanced the application as it released power when demand was highest.
Since the initial application further work had been undertaken to work on the contamination risks.
The BESS was noted as the only credible source of potential contamination during a residual fire event. Mitigation had been put forward including, a lined drainage system, attenuation tank and a self-actuating valve. It was suggested that in the event of a fire the valve completely isolated and retained fire water within the site. The self-actuating valve was autonomous and would be activated in the build up to a fire.
There had been four incidents of fire at solar plants in the UK since 2020 and none of these had led to contamination of ground water due to mitigations inherent in such systems.
If the Development Control Committee agreed that no functional pathway for fire water existed, then it would have followed that there was a negligible risk of contamination to the spring.
The application was an outline application, and the applicant would accept conditions on mitigation aspects if necessary.

Following their presentation, Members then sought clarity from the applicants on the following points:

Would moving the location of the BESS impact the degree of risk of water contamination to the spring. The applicant asserted that the risk was considered negligible and the mitigation in the proposed location was sufficient. Moving the BESS would not alter this assessment. The Development Control Committee considered if a “negligible” risk was too high.
What factors had been considered in the application for the location of the BESS. The factors considered had included the landscape impact, the screening provided, the ecological impact and the highways access for both construction and services. It was noted that other locations would have different impacts on ecology and outlooks given the slope of the site. The applicant stated that the location of the spring had been a consideration but with mitigation the location in relation to the spring was considered acceptable.
The Development Control Committee established that changing the location of the BESS could not be achieved without a new planning application.
The Development Control Committee explored the mitigations that were proposed by the applicant with reference to the capacity of such systems to withstand simultaneous extreme weather events and fires.
The effectiveness of the suggested mitigation items, such as the self-actuating valve, in a variety of potential events such as hazardous overpressure scenarios, fires and one in a hundred-year storms were discussed. The applicant advised that over pressure scenarios were extremely unlikely on this site due to the size and gradient of the site, and the chances of this coinciding with an extreme weather event were small. Assessment had been made for a “reasonable worst-case scenario” which included a one in 30-year storm and a simultaneous fire. Other mitigations could be added to such a system by condition and could include an additional valve and pre-treatment of collected surface water.
The self-actuating isolation containment system capacity during an “event” was explored. It was clarified that the system did not require a clean water supply during the duration of an event and had capacity to circulate water for two days.
The self-actuating isolation valve was confirmed to be new technology, which would need replacement and maintenance throughout the lifetime of the project.
The Development Control Committee discussed the potential impact of the solar panel foundation posts on the aquifer that supplied Caswell House. The applicant suggested that the rods were sunk to a depth of between one to two metres, with the aquifer being below this depth. The rods would not create a channel flow beneath the surface into ground water. The rods would be removed after the life of the project.
The Fire Brigade Authority had been consulted and had no objections subject to a Storage Management and Emergency Response Plan. A Battery Storage Safety Management Plan was also in the application. In the discussion a Member referenced a section of a report from the Fire Industry Association, in particular with regard to potential BESS fires and their treatment. The applicant acknowledged the fire risks but noted that well established international standards had been followed.
It was suggested that the spacing of the BESS units ensured that the risk of fire spreading between them was minimal as there was no thermal runaway.
There was discussion around the applicant’s openness to increasing the mitigation provision and moving the BESS unit. The applicant restated that moving the BESS would not change the negligible risk assessment and would require a new application as such changes would be materially different and would include other potentially harmful impacts.
In the event of contamination of the spring, a query was raised if it as possible for Officers to condition a commitment from the applicant to supply water to neighbouring businesses until it was proved contamination was no longer present. The applicant noted that the polluter would be liable for damage in the event of a fire and this was therefore controlled by law. In the discussion it was suggested that the consideration was reputational not financial for the surrounding businesses.

The Principal Planner then concluded his presentation making the following points:

Costs had not been a material consideration on the application however cost implications could be considered by the Development Control Committee.
Condition eight now included a section that stated the details agreed were retained in perpetuity.
The Principal Planner noted that the main reason for refusal at the Sub-Committee had been the risk of contamination to the aquifer. However other relevant considerations were:
- Policy EH6 supported renewable energy applications in principle but should minimise adverse impact on the surroundings that included high value landscape and the historic environment.
- The application had a capacity for generation and storage of 30 MgW with the potential to supply twelve thousand homes and saving half a million tonnes of CO2 over its forty-year life span. These benefits accorded with the NPPF renewable energy provisions.
- The landscape visual impacts were reviewed. The impact had been mitigated by the extension of the woodland belt on the southern boundary to the western boundary. There would be some harm, but the impact was contained to a localised level.
- There was a low level of less than substantial harm to the setting of heritage assets and this harm was outweighed by the considerable benefits of the application.
- There was no adverse impact from the loss of the agricultural land which had been confirmed by the Biodiversity Officer.
With regard to the drainage and contamination risk, the Principal Planner noted that the risk and mitigation details proposed were considered acceptable concerning storage of potential hazardous fire water. Details of the briefing note submitted by the applicant were given which concluded that the mitigations would result in the complete containment of contaminants on site and therefore had assessed the risk to the spring as negligible. The Principal Planner expanded on the mitigations that had been added by the applicant since the decision at the Sub-Committee.
Subject to the mitigations proposed being undertaken, which would be secured in condition eight, and the securing of a S106 agreement, Officers recommended that the application be approved.

The Chair then invited the Development Control Committee to debate the application. In the discussion that followed the following points were raised:

There were potential risks from gases produced by a fire at the BESS units. The Principal Planner advised that this was not an issue raised by any consultee or third party and the primary consideration was contamination of water supply. The NPPF gave considerable weight to the storage of intermittent power supply such as the use of a BESS facility.
A Member noted that the expert advice on potential water contamination from both parties differed and this was an uncomfortable position for the Development Control Committee. Consideration should be given to incoming new technologies and Government standards before approval.
Further confirmation was sought as to the degree of discussion that had taken place on the potential to move the BESS. The Principal Planner reminded Members that the application needed to be considered as brought to the Development Control Committee. There would be impacts of moving the BESS and as such any movement would require re-consultation. It was not possible to condition the movement of the BESS. It was reiterated that movement of the BESS would require a new application.
The flow of surface water was considered and noted to be down to the south-east corner of the site. However, the design of the mitigation included containment of water in the attenuation tank regardless of the direction of flow.
The approach to a BESS fire by the Fire Service was outlined. A Member noted current procedure was not to attempt to put out such a fire but to mitigate damage to the surrounding area. It was also noted that the capacity of the attenuation tank was sufficient.
The Development Control Committee suggested that increased mitigations to increase containment could be dealt in the discharge of point J of condition eight.

Councillor David Melvin left the meeting at 12:19

Councillor Julian Cooper proposed to approve the application in accordance with the recommendations in the Officer Report.

This was seconded by Councillor Ashton with a proposed amendment to condition 10 to amend the wording “prior to first occupation” with the wording “prior to commencement of operations”.

A further amendment was proposed that a further assessment of the quality of water and the aquifer should be undertaken by the applicant post-construction and thereafter.

A further amendment was proposed that an additional condition be added to the effect that the applicant would supply a water standpipe to Caswell House for use in the event of water contamination.

A further amendment was proposed that the applicant would be required to include additional mitigation of an additional valve.

The Principal Planner reminded the Development Control Committee that he had included additional wording to the final line of condition eight to include the words “and retained in perpetuity”.

Councillors Cooper and Ashton accepted the amendments to their proposition, and this then went to the vote.

Voting Record – For 10, Against 6, Abstained 1.

The Development Control Committee Resolved to:

1. Determine the application in accordance with the recommendations of the Head of Planning with the following additions to conditions 8 and 10:

a. Condition 10 to be amended to replace the wording “prior to first occupation” with the wording “prior to commencement of operations.”

b. Condition 8 to include a requirement that the applicant would provide a water standpipe to Caswell House for use in the event of water contamination.

c. Condition 8 to include the requirement for the applicant to include additional mitigation of an additional valve for redundancy.

d. Condition 8 to require the applicant to undertake a further assessment of the quality of water and the aquifer post-construction.

e. Condition 8 to include additional wording to the final line to include “and retained in perpetuity”.

Councillors Nick Leverton and Michele Mead left the meeting at 12:40.

Supporting documents:

Agenda item

24/03278/FUL Land (e) 431186 (n) 208772 Witney Road.

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