Sewer repairs were required for Thames Water, on a HS2 site, where the Colne Valley viaduct carries train tracks over a series of lakes and waterways at Hillingdon.
ChallengeJ Browne had to access a section of the leaking sewer in order to make repairs. Due to the proximity of several lakes, the excavation took them significantly below the water table, and despite the installation of a cofferdam, it required continuous dewatering at a rate of 20-30m3/h to keep the area dry. Water from the excavation was highly turbid as it was being pumped from the bottom of an active work area. This water needed to be treated to produce visually clear and safe water before being discharged, including reducing the pH if required.
J Browne called upon RVT Group to survey, recommend, and install a water treatment solution that would help them to meet their project timescales. It was also essential that the solution would deliver water quality that was in line with what the Environment Agency identified as the discharge parameters at this location.
SolutionAfter surveying the project, RVT installed a full chemical dosing system. This consisted of an agitated mix tank, dosing stand, and lamella settlement tank. The system provided flow-proportional chemical dosing and pH adjustment. The dosing skid automatically added flocculant and coagulant as required to make fine suspended solids easier to remove when discharging the water. A real-time monitor was also installed on site, which gave the team the ability to assess water quality levels in real-time.
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