Sewer systems are a vital part of a nation's infrastructure and play an essential part in maintaining public health. Yet they are largely out of sight and in the past this has often been a cause of neglect, leading to sewer flooding, polluting discharges, collapse and blockage. Where such performance failures did occur, solutions were often unplanned, piecemeal and uncoordinated.

Following the reorganisation of water and sewerage functions in the UK in the 1970s, a number of investigations were carried out into the state of the nation's water and sewerage assets - DoE/NWC 1977. (Department of the Environment/National Water Council, 1977. Sewers and Water Mains - A National Assessment. NWC/DoE Standing Technical Committee Report No. 4 NWC). MMC 1981, 1982, Monopolies and Mergers Commission, 1981. Severn Trent Water Authority, East Worcestershire Waterworks Company and The South Staffordshire Waterworks Company, A Report on Water Services supplied by the Authority and the Companies, HMSO. Monopolies and Mergers Commission, 1982, Anglian Water Authority, North West Water Authority, A Report on the Sewerage Functions of the Two Authorities, HMSO. House of Lords. Select Committee on Science and Technology, 1982, The Water Industry. Volumes I and II. HMSO, December 1982.

Two of the main conclusions of these investigations included the need to substantially improve information about all aspects of sewer systems, and to develop fully integrated strategies to improve the cost effectiveness of the rehabilitation work carried out on sewer systems.

At the same time advances in technology in a number of areas including sewer hydraulic modelling, sewer flow measurement and pipe internal CCTV inspection, allowed improved investigations and understanding of sewer systems. WRc was at that time developing new procedures for planning sewer rehabilitation work, capitalising on these developments. The House of Lords Select Committee (House of Lords Select Committee 1982) recommended that:

"the WRc's strategy for selective inspection and repair, with an increase in short term expenditure, should be adopted".

These procedures were later published as the first edition of the Sewerage Rehabilitation Manual in 1983. Drainage Area Plans were subsequently produced for most of the sewer systems in the UK and the current level of relevant information on sewerage infrastructure is greatly improved.

Since then there have been further changes in the structure of the water industry in the UK. Certain aspects of the Sewerage Rehabilitation Manual procedures were incorporated into the regulation of the water industry. There have also been further pressures to improve performance standards. These include customer and regulatory pressures to reduce sewer flooding due to hydraulic inadequacy or operational problems, requirements from national legislation and European Directives to improve environmental performance, and regulatory pressures to improve efficiency both in capital investment and operational expenditure.

As part of the drive to improve environmental performance, more detailed complementary procedures were developed for the planning of environmental upgrading works on sewer systems are contained in the Urban Pollution Management Manual, FWR 1994 and 1998. (UPM Manual A Planning Guide for the Management of Urban Wastewater Discharges During Wet Weather, FWR. 1994, 2nd Edition, October 1980).

Updated: 4/12/2012