Investigating surface water outfalls at Malt Mill Lake

Environment Agency Malt Mill Lake Walkover 10/09/25

This month, Friends of the Dart joined the Environment Agency for a joint walkover of Malt Mill Lake — a tributary that runs parallel to Plymouth Road, flows along Coronation Road, and joins the main Dart at Vire Island. The stream is fed by two combined sewer overflows (CSOs) and has been monitored by the Environment Agency throughout the bathing season, consistently showing elevated E. coli and intestinal enterococci levels.

The walkover was designed to investigate surface water outfalls and check for possible pipe misconnections — where wastewater pipes are mistakenly connected to surface water pipes. Using an ammonium probe, we tested four outfalls; encouragingly, all showed ammonium levels within the safe range.

Access challenges meant we were unable to reach the upper stretch of the stream on this occasion. However, we will be reviewing options for site access and plan to revisit for another walkover in the coming weeks.

We are thrilled to be collaborating with the Environment Agency on this work. By combining our local knowledge and monitoring with their technical expertise, we are building a clearer understanding of the issues facing Malt Mill Lake and how best to address them.