This pump-controlled iron-enhanced sand filter (IESF) will protect, enhance, and restore water quality in an impaired water – Golden Lake. The project is estimated to remove up to 60 lbs-TP/yr from water entering Golden Lake. This project, paired with two previously installed upstream BMPs, will achieve up to 94% of the total external TP load reduction identified in the approved TMDL.
Golden Lake is within a developed area of Anoka County, just north of the Twin Cities metro area. It is surrounded by residential land use, and the focal point of a city park. The approved Golden Lake TMDL requires reductions in phosphorus from external and internal loading sources. This project will focus on reducing external phosphorus sources. The proposed IESF basin was identified in the Golden Lake Subwatershed Stormwater Retrofit Analysis to be one of the most cost effective remaining practices for reducing external phosphorus loads to Golden Lake.
The IESF basin will be installed on property owned by the City of Circle Pines near an existing stormwater treatment pond adjacent to Golden Lake. This pond receives stormwater runoff from a 6,426-acre drainage area via County Ditch 53-62. The pond currently provides treatment through retention and settling. However, the addition of an IESF will increase removal of phosphorus, particularly dissolved phosphorus, which the pond does not effectively treat.
The IESF basin will incorporate a pumping system to move water from the pond outlet to the IESF basin, which will be split between two zones. The IESF will be designed with sufficient binding sites to sequester up to 50 lbs-TP/yr for 25 years. Estimated reductions are 30-60 lbs-TP/yr; the range is based on known and predicted temporal variations in TP concentrations of incoming water.
WSB Engineering was contracted by the Anoka Conservation District to complete project design and construction management following an interview process with several firms. WSB also happens to be the long term engineering firm for the City of Circle Pines, giving them extensive knowledge of the project’s history, need and benefits.
Several landowner meetings were held to explain the project to interested citizenry. Primarily attended by those who live immediately adjacent to the project, several design modifications were made in response to homeowner concerns.
WSB completed project designs and put them out to bid. The project was awarded to the low bid, G.F. Jedlicki Inc. Following some negotiations and project modifications to get the project scope within budget, agreements were signed and project construction began.
The bulk of the project (74%) was installed in by mid-December 2018. The pipes, liners, drain tiles, berms and filter media are in place. ACD staff completed the media testing to ensure uniformity and concentration of the iron filings throughout the media. Average concentrations were approximately 8.5%, which of a bit higher than planned but within acceptable thresholds and will actually allow the project to remove more dissolved phosphorus than planned over the life of the project.
In the spring of 2019 the valves, control panel and pumps will be installed.
Throughout 2019 partners will work to fine tune operations to optimize performance and integrate their findings into a long-term operations and maintenance plan.
Operations and Maintenance Reference Manual:
Golden Lake IESF II Operations and Reference Manual
Clean Water Fund Work Plan
MOU between City of Circle Pines and ACD