The construction of Lee Tunnel will help tackle the discharge of up to 16 million tonnes of untreated sewage which is discharged into the River Thames via Abbey Mills Combined Sewer Overflow into the River Lee.
The works comprise a 7.2m internal diameter storage/transfer tunnel approximately 6.9km long from Abbey Mills Pumping Station to Beckton Sewage Treatment Works between 65m and 74m deep and initially included the construction of two 25m and one 20m internal diameter shafts and an off-line Tideway Pumping Station Shaft, which is 38m in diameter. Twin overflow culverts will be constructed out into the River at Beckton. The works also include all MEICA works required to intercept, control and pump out flow for treatment.
Subsequently an additional reception shaft and short connection tunnel to Lee Tunnel Shaft F was constructed at Abbey Mills. These works were undertaken on behalf of Tideway as the original proposal would have meant a prolonged shutdown of the Lee Tunnel which would be more expensive and contain more safety risks. Agreement for this was done in conjunction with Tideway and the industry regulator OFWAT.