Working to slow down the phosphorus train

Photo submitted

Photo submitted

Angie Hong
Guest Writer

We’re standing in a field near the Forest Lake water tower and the sounds of insects are almost deafening. Grasshoppers are launching themselves around crazily and the sun is beating down on our backs. The Washington Water Consortium, a group comprised of representatives from local units of government, state and regional agencies, and private contractors that frequently work with communities on their water projects, is on its annual tour and this nondescript field is one of our last stops.

More important than what we can see in this field, is what we cannot. Beyond the trees on the north edge of the field is a series of wetlands that connect to the Sunrise River, which flows to Comfort Lake before continuing north and eventually reaching the St. Croix River at Wild River State Park. Just south of the field is Broadway Ave., a major road and commercial corridor for Forest Lake.

Three years ago, Washington County applied for a permit from the Comfort Lake – Forest Lake Watershed District to reconstruct Broadway Avenue through the City of Forest Lake. In order to protect lakes and rivers within its boundaries, the Watershed District has rules governing new development and redevelopment and to comply with these rules, the county’s roadway project included a sediment pond and filtration basin designed to treat stormwater runoff from 52 acres of land along Broadway Avenue. Now, when it rains, water that runs off of the road and nearby properties flows into storm sewers that connect to a pond at the northwest corner of First Avenue and Eighth Street. As water collects in the pond, sand, silt and other debris settles to the bottom. When the water reaches a certain height, it then flows out into the field north of the pond, which is actually a filtration basin. In the basin, the water soaks into the ground and additional pollutants, such as oil, metals and phosphorus are filtered out by the soil so that the water is cleaner by the time it filters down to drain tile that connects to the nearby wetlands.

Though the sediment pond and filtration basin created by the County were enough to meet the rules, the Watershed District worked with county engineers and local firm, Emmons & Olivier Resources, Inc., to further enhance the project so that it could remove even more phosphorus from the water running into the wetlands. Phosphorus is a natural element found in sand, silt and yard waste and it is carried into lakes and streams when rainwater runs off of rooftops, parking lots and streets and into storm sewers that connect to nearby water bodies. In lakes and slow-moving rivers, phosphorus feeds algae, resulting in green water that is often murky instead of clear. There are several stretches of the Sunrise River that are listed as “impaired” due to poor health, often as a result of too much silt in the water, and the Sunrise River is also one of the biggest sources of phosphorus to the St. Croix River, which sometimes suffers from toxic algae blooms late in the summer.

For the Broadway Avenue project, the Comfort Lake – Forest Lake Watershed District funded the additional cost for the County to incorporate iron-enhanced sand into the filtration basin so that it filters out even more phosphorus than it would normally. Altogether, the pond and filtration basin will remove 37.9 pounds of phosphorus from the runoff water entering the Sunrise River wetlands, which is the equivalent of nearly 20,000 pounds of algae. If you consider the Sunrise River as a train that gathers more and more pollution as it travels, this project will take one car off the back of the train, meaning less phosphorus in Comfort Lake, less phosphorus and sediment clouding the water in the Sunrise River, and less phosphorus contributing to algae blooms in the St. Croix River as well. That nondescript field in Forest Lake? It’s the first stop on the clean water train.

Angie Hong is an educator for East Metro Water. Contact her at 651-275-1136 x35 or angie.hong@mnwcd.org.

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