asked the Secretary of State for the Environment what information he has regarding the number of sewer collapses in the area covered by each water authority since 1979.

The main sources of information on sewer collapses and other failures since 1979 are: a series of reports produced by the water research centre covering the period 1981–1985; and summary information in water authorities' corporation plans. 'The WRC survey indicated that the total number of failures requiring excavation in England and Wales is running at between 4,000 and 8,000 per year and that over half of these were collapses.Figures of significant sewer failures for 1985–86, as given in plans, are as follows:

	Numbers
Anglian	290
North West	1,140
Northumbrian	230
Severn Trent	420
South West	220
Southern	510
Thames	650
Wessex	280
Yorkshire	1,340

Figures for earlier years were provided in an answer to the hon. Member for Newcastle-upon-Tyne, North (Mr. Brown) on 15 January 1986, but because of varying and improving reporting methods, caution is at present needed in making any comparisons between authorities or over time.