Thames Water – Ripley Green

Updated July 2025

Following a Flood Forum meeting on 27 June 2025, information was given to Ripley Parish Council about Thames Water works that will affect The Green. Ripley Parish Council now have a reference for The Green and will be chasing this further.

We have asked for a construction traffic/access plan, where the sewer pipes will be routed, what the current capacity is and what additional capacity is required and when exactly works will take place.

Taylor Wimpey and Thames Water: Agreement on Ripley Wastewater Treatment Works

The following Q&A has been compiled using information from the sources listed below:

A: Ripley relies on a combined sewer system, which means rainwater and untreated sewage share the same pipes. During heavy rainfall, the system can become overloaded, leading to sewage overflows, including at the Ripley sewage works.

Thames Water has acknowledged that it currently lacks sufficient wastewater infrastructure to support major new developments at Gosden Hill, the Former Wisley Airfield, and Allium Park (the former Garlicks Arch site).

The Guildford Local Plan includes a requirement that infrastructure such as sewage capacity must be delivered in time to support these developments, not after they are occupied.

A: Records show serious flooding at Bridge End Farm in 1968, and more recent incidents at Elm Corner and Ockham Lane, logged by Surrey County Council.

Residents have also reported regular flooding, linked to Stratford Brook and sewer overflows (e.g. manhole covers lifting). Attendees at the CLG meeting were encouraged to press Thames Water and Surrey Highways on maintenance — a commitment Thames Water agreed to support (CLG Minutes p.3).

A: At present, the Wisley site has large areas of concrete (the old airstrip and hangar), which means rainwater runs off quickly with no controls, increasing flood risk.

As part of the development, Taylor Wimpey must install drainage systems to slow and manage surface water, bringing it down to greenfield (natural) run-off rates. This improvement — or “betterment” — will reduce flood risk compared to current conditions. (CLG Minutes p.4)

A: A new sewer is likely needed to connect drainage from Ockham Lane to the development. As building starts at Wisley Lane and progresses eastward, solutions for Ockham may be several years away. Residents are encouraged to stay in contact with Thames Water to ensure current issues aren’t overlooked (CLG Minutes p.4).

A: Ripley STW serves the village and surrounding areas. It is prone to storm overflows during heavy rainfall, discharging into the River Wey/Ockham Mill Stream, part of the wider Wey river system, flowing from Shalford to Weybridge. The system does not fully separate surface water from sewage, which increases overflow risks. See Storm Overflow Action Plan.

Yes. Thames Water plans to complete upgrades by summer 2030 as part of its AMP 12 programme.

Upgrades aim to reduce pollution, particularly by lowering phosphorus levels in treated wastewater to below 0.25mg/l, improving river health.

The Infrastructure Delivery Plan also calls for new foul water connections and increased capacity to support growth (CLG Minutes p.6).

Yes. Since 2019, developers are required to pay a sewer charge for each new home, even if upgrades to the sewer network aren’t immediately needed. This helps fund future improvements to ensure the system can cope with additional demand. (CLG Minutes p.4).

Concerns were raised about the impact of 4-5k additional people using the sewage system. Taylor Wimpey must pay a per-home charge to fund sewage upgrades. In West and East Horsley, which also use Ripley STW, Thames Water has confirmed upgrades could take up to five years (CLG Minutes p.11).

A: The Wisley sewage treatment facility is not large enough to handle the volume of waste expected from the new development. Although it is geographically closer, it lacks the capacity and infrastructure to serve a strategic site of this scale. The Ripley works, while further away, is the nearest facility with potential for upgrade to meet these demands.

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