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RSPB Ham Wall

Ham Wall is a Nature Reserve on the Somerset Levels managed by the RSPB. Once part of a shallow sea, the reserve is made up of wetlands, reedbeds and peat bog teeming with wildlife and migratory birds. And thousands of visitors for which toilet facilities were desperately required.

Ham Wall attracts up to 1,000 people per day during its busiest season. With heavy concentrations of ammonia, highly intermittent flows and the need for a silent treatment works, Ham Wall’s location on a peat bog and wetland introduced unique challenges to the specification of sewage works.

WCI’s solution was to specify a non-electrical treatment system which was resilient to intermittent loadings and which could be sized for the high concentrations of ammonia the system was forecast to receive. To address the highly unstable peat soil structure and the high water table, only the primary tank was installed below ground. This allowed for gravity foul drains to be used to carry the solid waste to the system. Septic effluent was then pumped to the treatment units which were installed on a concrete raft above ground to minimise the amount of groundworks required. The entire scheme was sympathetically fenced and reinstated with the seed bank which had been carefully stripped on commencement of the works.


A 10,000 litre super-reinforced HDPE primary tank was installed below-ground together with a separate pumping station. The pumping station elevates septic effluent to three non-electrical passively-vented filter units installed on a steel-reinforced concrete raft. Final discharge is via a Somerset Drainage Board-approved headwall to an adjacent drain.