Ag BMP Soluble P Reduction

In recent years, nutrient enrichment has occurred in Lake St. Croix due to increasing amounts of phosphorus entering the lake from the watershed. According to the TMDL, approximately half of the phosphorus-loading to Lake St. Croix is in the soluble form, and agriculture has been identified as one of the largest contributors of that phosphorus. In addition to the TMDL, subwatershed analyses were completed to identify, assess, and prioritize phosphorus-reducing practices in rural areas draining to Lake St. Croix in Washington County. This project will reduce phosphorus discharges to the St. Croix by enhancing the soluble phosphorus removal capacity of targeted agricultural stormwater best management practices prioritized in the 2013 Top 50P! Rural Subwatershed Analysis and the 2014 St. Croix LCCMR Prioritization Rural Subwatershed Analysis. Using urban stormwater technologies such as infiltration, iron sand filters, and aluminum-based water treatment residuals, at least four targeted agricultural stormwater practices will reduce phosphorus discharges by least 50 lb/year. This project will enhance the function of traditional agricultural stormwater BMPs to further reduce phosphorus within the same footprint of an existing or newly constructed agricultural BMP.