Project Appreciation and Objectives
Interceptor traps (also called Buchan traps or Winsor traps) were provided on almost all drain connections from the mid 19th century until the mid 20th century. The blockage rates on sewers with interceptors has been found to be up to 100 times the blockage rate on comparable modern sewers without interceptors. However the effect of the number of interceptors on drain and sewer systems and the blockage rate at interceptors is not known.
This project developed a model to estimate the numbers and different types of interceptors in public and private sewers and lateral and private drains and predict the blockage rate for each interceptor type. The project also examined the costs and implications (including legal requirements) of interceptor removal and installation.
Benefits to Clients
A robust estimate of the numbers of interceptors and the blockage rates will allow sewerage undertakers to:
- Understand the true costs of interceptors on their existing public sewers.
- Understand whether there is a robust business case for proactive removal of interceptors in accordance with the Sewerage Rehabilitation Manual (SRM) procedure and demonstrate this to the economic regulator.
- Improve their understanding of the costs of interceptors following transfer of private sewers and laterals in England and Wales.
- Comprehensively review pertinent literature and legislation, including relevant information held by participants.
- Investigate interceptor provision and blockage patterns in selected case studies.
- Examine the different methods of interceptor removal and identify associated problems.
- Establish the reasons behind the retention or installation of interceptors by local authorities.
- Spreadsheet based models to estimate the numbers of interceptors of different types in each contributor's area and to predict the numbers of blockages per year in each type of interceptor.
- A report giving guidance on the use of the models.
- A leaflet giving guidance to operations personnel on the likely locations and types of interceptor, guidance on removal and reasons for retention (if any).
Related WRc Work
- SRM Update, 2006-2008.
- Sewer Jetting to Reduce Flooding - Best Practice Manual, 2004-2005.
- Private Sewers Investigations for UKWIR, and various individual water companies 2001-2008.