Taylor Wimpey has at last submitted its latest application for an off-site drainage scheme which will require the ground at Thames Farm to be stabilised by grouting the sinkholes and underground voids.

This will pose a huge risk to the Grade 1 aquifer below the Thames Farm site which is also in a Zone 1 Source Protection area. The aquifer provides drinking water for Henley, Harpsden, and Shiplake.

This is just too big a risk to take and the community needs to ensure that the authorities do not allow this to happen.SODC will have to listen to the community if there are enough objections registered with them. The letters the residents sent last October stopped the proposed Lashbrook drainage scheme.

Arguably this is even more important. No one should be allowed to take risks with such a fundamental natural resource which is so material to how we live. Unpolluted drinking water is a right that we have to protect.

We must ensure that the authorities respect this position. There will be no reverse process if they get it wrong!

TFAG is fully aware of the “objection fatigue “ that can set in after such a protracted process but we need all residents to object by mail or email as soon as possible. It will make a difference and could be the last chance you will have to affect such an important decision. Below  is a summary of the current position as well as a suggested narrative on which to base your objections.

Objecting to the Latest Drainage Proposals

TFAG hopes that you are willing to continue to add your support to the concerns over the latest application. Taylor Wimpey has submitted their latest drainage proposals to South Oxfordshire District Council’s planning department for consideration.

Should they be approved this will remove the final hurdle and allow them to commence the development of the site.
TFAG and its advisors believe that there are significant issues and unanswered questions, particularly around the impact of their proposals on our drinking water supply that have not been addressed. It is therefore critical that we demonstrate the level of concern within our community to those who will make the planning decisions to ensure that they consider our views in making their assessment of Taylor Wimpey’s plans.

Why Should I Object?

All the drinking water for Shiplake, Harpsden, and Henley comes from the aquifer (an underground reservoir of water that is contained within the porous underground structure – like a sponge) which is located below the Thames Farm site. Given its location to this critical water source, Thames Farm and the surrounding area is designated by the Environment
Agency as a Source Protection Zone. As Thames Farm is so close to the point where our water is drawn from (the corner of Bolney Lane and Reading Road), it is within a Zone 1 Source Protection Zone. This is the highest level of protection that the Environment Agency places on such water supply locations and as such, the kinds of development and activity that are permitted in these zones are very limited. This water level in the aquifer varies throughout the year but is approximately 14-16 metres below the surface.

Due to the sinkholes and poor ground conditions found on-site, Taylor Wimpey plans to grout (fill the sinkholes and voids with cement) and compact the ground so they have a stable base to build upon. Many of the sinkholes have been identified to be up to 16m deep. They, therefore, coincide with the top water level of our drinking water supply.

By grouting these holes there is a risk that cement and other materials will enter our drinking water. Also, by filling these voids and compacting the ground around the voids, the way in which rainwater recharges the aquifer will be changed. Taylor Wimpey has failed to provide an assessment as to how their proposed plans will impact our water supply or how they intend to assess and manage the risks associated with their activities. The lack of these plans and an appropriate hydrological risk assessment means that it is not possible to determine whether our drinking water supply will remain protected during the lifetime of the proposed development.

What does permeability mean and why is it important?

Permeability refers to the potential for the ground to absorb and soak away water that falls upon it. Very sandy soil has a high permeability as water easily soaks into it and is absorbed. Clay soil has a very low permeability causing water to not easily soak into it but instead pool and run off it. Hard surfaces such as roads, roofs, and pathways are considered impermeable (i.e. they cannot absorb any water) and all water that falls upon them will runoff. During intense or prolonged periods of wet weather, such run-off leads to localised flooding at low points. Given that Thames Farm is on a small hill or rise, any such flood water will flow towards and across Reading Road and inundate the houses on the village side of the road. Because of this potential to cause flooding, the Developer is required to buffer and store run-off water and then discharge it at a flow rate that the local environment can cope with.
This is known as attenuation. The amount or volume of attenuation is calculated by understanding the size of the development, its permeability and how it behaved prior to the development occurring (known as greenfield run-off rate). We believe that in calculating the volumes of surface water that they need to attenuate from Thames Farm, Taylor
Wimpey has not taken account of the impact of the groundworks they propose. This will affect the permeability and run-off rate and they have therefore underestimated the attenuation volume they require. By doing this, there is a much higher risk of local flooding occurring during prolonged wet weather.

A Template For Objection

In order to assist you, we have developed a template response that you can draw up to submit an objection. Concerned residents are requested to use some or all of the points given below to submit their own objections. These objects can be submitted to:

planning@southoxon.gov.uk

All objections should use the planning reference: P20/S2808/DIS-HAR

Name: [Insert Name]

Address: [Insert address / e-mail]

Planning Reference: P20/S2808/DIS-HAR

Dear Sir/Madam

Land at Thames Farm Reading Road Shiplake.

I wish to object to the drainage strategy proposals submitted for this development on the following basis:

• The Developer has failed to demonstrate how they will protect the water supply for Shiplake, Harpsden, and Henley which lies directly beneath the site. My concerns mirror those of Thames Water who have stated that given the development is located in a Source Protection Zone 1 (SPZ1) of a strategic groundwater abstraction they require the Developer to confirm appropriate mitigation measures to ensure the water abstraction source is not detrimentally affected by the proposed development before, during and after its construction.

• The Developer has failed to provide an adequate hydrological risk assessment as required by the Environment Agency (The Environment Agency’s approach to groundwater protection February 2018 Version 1.2 - Policy N7) for development activities that present a hazard to groundwater resources, quality or abstractions within an SPZ1.

• The proposed approach does not consider the impact of the ground remediation works on the permeability of the site and the resulting volumes of surface water runoff that will need to be attenuated prior to discharge. This will likely lead to surface flooding during wet weather events when the attenuation capacity is overwhelmed due to a lack of capacity.

• The Developer's proposals contain plans for permeable paving and soakaways at various locations across the site. Given the level of grouting and ground compaction required to remediate the site prior to construction, no evidence has been provided to demonstrate how these drainage assets will be effective following the significant changes in soil permeability that will occur.

• The drainage proposals do not have any way to capture and remove contaminants in the surface water and protect the water quality of the receiving waters.

• The proposed off-site pumped solution for surface water is not aligned with the principles of sustainable drainage and is counter to Thames Water’s Net Zero commitments and SODC’s declared climate emergency. Henley Town Council has also declared a climate emergency which is also ignored.

• The proposals fail to provide any information regarding the ongoing operation and maintenance of the drainage scheme in particular they fail to acknowledge the permissions required from the riparian owners associated with the watercourse they plan to discharge into and how they plan to restore a currently silted and partially blocked watercourse and then maintain it in perpetuity. Without such agreements, flooding will occur in the future due to blockages and silt accumulation.

• The owners of the land across which the proposed drainage solution have yet to give their consent.

Yours faithfully
__________________________________________________________

Thank you for your continued support!

Peter@TFAG