Elton Reservoir slip

Abstract

Elton Reservoir was built between 1804 and 1808 to supply water to the Manchester, Bolton and Bury Canal. The canal is no longer open for boat traffic, but the reservoir does provide a sweetening flow. The reservoir is retained by a 600 m long embankment dam with a maximum height of 8.8 m, has a capacity of 923 000 m3 and a surface area of 22 hectares. Top water level in the reservoir is 87.70 mAOD (above ordnance datum). The Canal & River Trust (the Trust) is the reservoir owner. The reservoir has experienced a number of embankment slips in the past with the most recent being in 2012. The water level was subsequently reduced until repair works could be undertaken. A length of unlined spillway channel along the toe of the embankment suffering from erosion was repaired at the same time. The opportunity was taken to complete other remedial works including making the operation of the scour valve within the confined space of the outlet tunnel less onerous. This paper outlines the investigation works undertaken and the various options considered with respect to repairing the slip and providing embankment stabilisation, which led to the preferred solution of counterfort drains.