Washington Judicial Ditch 6 Headwaters Iron-Enhanced Sand Filter

Forest Lake is one of the top recreational lakes in the metro area and the largest lake in Washington County, with a diverse and healthy fishery and three public accesses. It is also an important economic asset to the Forest Lake community because of the impact of its tax base and recreational destination for visitors from outside the community. The water quality of Forest Lake also impacts downstream waters, particularly Comfort Lake, the Sunrise River, and ultimately Lake St. Croix. While not currently on the impaired waters list, the water quality of Forest Lake is very near the water quality standard for North Central Hardwood Forest lakes. Protection of Forest Lake water quality is a high priority for the Comfort Lake-Forest Lake Watershed District (CLFLWD), the City of Forest Lake, and the region. Monitoring of Forest Lake tributaries as part of the 2016 Forest Lake Clean Water Partnership (CWP) Diagnostic Study identified Washington Judicial Ditch 6 (WJD6) as the second largest contributor of flows and phosphorus loads to Forest Lake, second only to Shields Lake which is currently addressed by implementation of the FY17 Shields Lake Stormwater Harvest, Irrigation Reuse System and Alum Treatment project. This project proposes to treat 50% of the subwatershed runoff with an offline, multi-cell iron-enhanced sand filtration (IESF) treatment system. The headwaters of WJD6 is dominated by wetlands and contributes nearly half of the total phosphorus load in the WJD6 system, most of which is dissolved and difficult to remove with traditional best management practices (BMPs). This IESF will reduce watershed phosphorus loads to Forest Lake by 85 lb/yr.