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Client: London Underground Ltd
Roughton was initially commissioned by London Underground Ltd (LUL) to undertake an investigation to identify the quality of discharge from the existing septic tank/filter bed arrangement serving the platform level foul drainage system at Hornchurch station. This investigation identified that the quality of effluent did not meet the criteria specified in the agreed discharge consent and as such, it was agreed that Roughton would undertake a feasibility/option study to identify alternative means of discharging foul flows from the station.
At the same time, the station entrance was experiencing flooding during periods of heavy rainfall, and the project commission was extended to investigate the reason(s) for these instances.
Following completion of the feasibility stage, it was agreed with the Client that a new pumping system would be installed to transport foul flows from platform level to the sewer in Station Lane together with a new surface water drainage system to the station entrance. Works comprised the following activities:
In order to meet the requirements of London Underground’s design standards as well as the obligations of PPS25, the new surface water drainage to the station entrance was designed as an infiltration system.
The system comprised a series of channels and gullies to collect flows which discharge, via a series of silt intercepting catchpits, to a new soakaway constructed adjacent to the station. The soakaway was located to partially within an existing low embankment to ensure access to nearby properties was maintained during construction. On completion, a series of gabion cages was introduced to support the excavated section of the embankment; these were partially filled with site reclaimed concrete to minimise transport of fill material to site.
