Work began on Friday on a major £7.9M flood alleviation scheme in Lowestoft, Norfolk.
Set to assist 88 properties which are at risk of sewer flooding, the 55-week project will address the lack of combined sewer capacity that causes internal flooding during significant storm events. Previously during heavy rainfall in Lowestoft, the Norwich Road trunk sewer would surcharge, causing extensive external and internal flooding in nearby streets. Tidal ingress into the system was also affecting the efficiency of the Combined Sewer Overflow (CSO) outfalls. To resolve the surcharging and flooding conditions, the @one Alliance of Black & Veatch, Barhale and Anglian Water has designed and begun construction of a new sewer along the length of Denmark Road, adjacent to the railway line and inner harbour. And to minimise inconvenience to local people and traffic, construction in the roads is being avoided wherever possible; thus, four new tunnels (the longest being 900m of 1500mm diameter) are being created to transport flows to a new CSO, together with 10 intermediate caisson shafts (between 2m to 6m diameter). In addition to the tunnels, an open-cut pipework and a 10.5m diameter 15m deep pump shaft holds 3nr 500l/s pumps (duty/assist/standby), which will pump flows via a new screen and existing twin 750 gravity outfall into the Lowestoft inner harbour. To maintain sewer capacity during rising tides, new tide flex valves will be fitted to the outfall chambers. When flows are greater than the pumps' capacity, pumping station shaft and tunnels will surcharge, providing approximately 2200m3 of storage.