Tower Bridge Mud Tanks

Tender description

Tower Bridge Mud Tanks – this project will deliver repairs and enhancement works to 6no. mud tanks that form part of the rainwater/surface drainage infrastructure at Tower Bridge, as well as associated repair/enhancement works to improve safety, access, lighting, etc. in the 6no. mud tanks bays, which are situated on the lower levels of the bridge. Tower Bridge is a bascule bridge and beneath the two towers are the pivot and drive shafts and hydraulic operating machinery. Beneath the main pivot shafts are 6no. mud tanks; 3no. on the north side and 3no. on the south. The tanks serve to collect rainwater, surface run-off, and debris from the bascule arms when raised, to prevent them entering the chambers below. Currently, they regularly block up and overflow, and must be manually monitored and emptied. A condition survey was undertaken in 2017 which identified that all the mud tanks are in poor condition with significant corrosion identified, and without exception all require repair to some extent. Each mud tank consists of a front and rear chamber. The rear chambers will be assessed and repaired in situ. The front chambers will be cut out and replaced with a new mild steel chamber with deeper profile, improving the water storing capacity and providing adequate spatial clearanceto moving parts of the bridge. Both chambers will be protected with new GRP lining. Discharge pipework will need alteration and reconnection to the revised tank chambers. Each mud tank will receive new GRP mesh deck hinged covers, to prevent larger debris/detritus entering the tanks/chambers and causing blockages, while still permitting water/runoff to reach the tanks. Beneath each mud tank lies a platform of original timber planks spanning the bascule chamber. This platform is currently inaccessible due to structural degradation (rot) caused by water overflow from the tanks above. A specialist contractor will assess the strength and condition of the timber planks. If they are deemed sufficient for maintenance loads, the planks will be restored and reused, while damaged/rotten planks and the timber kerb will be replaced. Each mud tank bay will also receive new handrails/guardrails to promote safer access, improved LED lighting (mixture of replacement and new/additional), new small power provision, and corrosion treatment/repainting.