Event Duration Monitors (EDMs) record the duration and frequency of untreated, raw sewage releases into the river. Raw sewage dumps are only supposed to happen during extreme rain storms when the sewage treatment works can't cope with the capacity due to the additional rain. However, last year (2022) the EDM monitors recorded 345 sewage spills in just that year, totaling 4473.79 hours worth of raw sewage pouring into rivers across the Evenlode Catchment. As if that wasn't bad enough, it turns out that not all of the sewage treatment works have EDMs fitted and so this is an underestimation...
In 2021, Environment Agency data shows that Thames Water listed a total of 465 sewage treatment works across the whole Thames Catchment that were required to be fitted with Event Duration Monitors. They declared that all of those 465 assets had EDMs installed - 100% fitted.
Fast forward a year to 2022, and Thames Water declared there were 777 sewage treatment works that required EDM equipment in the area and of these, only 480 had EDMs fitted, resulting in a fitting level of 61.8%. This has put TW straight to the bottom of the rankings across 10 other water companies.
In terms of the Evenlode Catchment, we know 6 out of the total 19 sewage treatment works are not fitted with EDM monitors.
These storm overflows with no EDM equipment may well be contributing to the total spill events and hours across the Thames catchment area. There still remains the larger unknown as to the volume of untreated sewage entering our rivers during these pollution events. We need greater transparency by water companies in their reporting. An explainer from Thames Water as to why they have missing EDMs can be found here.
Find out more about our work and the Evenlode Catchment Partnership here
Want to know more about the pollution in our rivers? Take a look at WASP's (Windrush Against Sewage) website.
