Major sewerage work in Littleborough near Rochdale in North West England resulted in the closure of eight Combined Sewer Overflows and the construction of a new overflow incorporating downstream storage. The paper describes the method, named the CARP procedure, used in setting the frequency and volume of discharge from the new overflow and, therefore, the size of the tank. The effect of the resewerage work on the River Roch is being studied as a collaborative exercise involving the University of Manchester, Water Research Centre and North West Water. This is part of the River Basin Management Programme of the Water Industry of England and Wales (Clifforde et al, 1986). First results indicate that the tank will not operate as frequently as predicted by computer modelling. The discharge from the new Combined Sewer Overflow would not appear to significantly effect the river. This is to be confirmed by further fieldwork.
