Posted November 12, 2019
City may consider storm sewer filters to improve water quality in lake
Mill Lake could flood nearby homes in the event of a significant flood, a new city report says.
That will lead staff to consider dredging the lake – a move that could both reduce flooding risk during the winter and improve its “somewhat poor” water quality.
In the event of a major once-in-100-year storm, “the potential of flooding is widespread” across the Willband Creek watershed that drains most of central Abbotsford, according to a research report completed for the city as it embarks on work to create a new stormwater management plan for the area.
Dredging Mill Lake would help increase the water body’s storage. It would also provide cooler water and increase oxygen levels.
But, first, the city would likely need to sample the sediments at the bottom of the lake to find out how polluted they are and how easy it would be to dispose of any muck that is dug out.
Locals once swam in Mill Lake, but its water quality is considered compromised, in part because of insufficient water circulation and stratification. The city report also suggests exploring the possibility of installing mechanical aerators.
The city could also take a simpler step to improve the water quality, by catching oil and grit that currently runs from storm sewers into the lake.
Such oil/grit separators are commonly used but require frequent maintenance and cleaning to stop them from clogging. The report suggests more sophisticated treatment options exist, but would cost more.