Screens – do we still need them?
Jeremy Benn, Director, JBA Consulting and co-author of Culvert, Screen and Outfall Manual (C786) discusses the role of Screens.
Even though there may have been a screen for many years, it is good practice to periodically review if the screen is still required or remains fit for purpose.
The recently published CIRIA Culvert, Screen & Outfall Manual (C786) sets out how and when to assess the continued need for a screen (Chapter 4) and includes an Initial Need Assessment (INA) methodology (Appendices 2 and 3). The INA can be completed in a few hours and there are easy to use spreadsheets available to help with the process and which create an audit trail of the decision making process.
Where inlet debris screens may no longer be justified or where the performance of an existing screen needs to be enhanced, the Manual gives advice on the use of a primary or coarse screen. Primary screens are used to collect only the larger debris and also, if sited and designed appropriately, do not require intervention (cleaning) during high flows.
Coming soon: the next blog which will highlight the importance of avoiding or minimising manual clearance of screens.