FY24 CWF Keller Lake Targeted Stormwater Treatment Project

The City of Apple Valley will continue efforts to improve water quality in Keller Lake by expanding Whitney Pond (KL-P2) to provide phosphorus load reductions contributing to the lake's nutrient impairment. Whitney Pond is a 2-acre stormwater basin located at Burnsville's Lac Lavon Park and Keller Park in Apple Valley. The pond is in Burnsville on land owned by the City of Burnsville. The pond treats stormwater from a significant portion of the Keller Lake watershed in Apple Valley that would otherwise drain to Keller Lake untreated. Keller Lake is a DNR classified natural environment lake that has been listed on the impaired waters list for nutrients since 2002. Keller Lake is tributary to Crystal Lake in Burnsville. Crystal Lake is a recreational lake that was delisted from the impaired waters list in 2018. This targeted project will help protect Crystal Lake and provide measurable improvements to Keller Lake nutrient loads.

Since the construction of Whitney Pond, the Crystal, Keller, and Lee Lakes Nutrient Impairment and Total Maximum Daily Load (TMDL) Report and Earley Lake Water Quality Assessment was completed in 2011 outlining a wasteload reduction of 130 lbs of Total Phosphorus (TP) per year for the City of Apple Valley. In 2017, the City of Apple Valley completed the Keller Lake Subwatershed Assessment (Barr, 2017) to evaluate options for additional stormwater quality treatment within the Keller Lake watershed.

Because Whitney Pond does not achieve all the nutrient load reduction required by the Keller Lake TMDL, one of the most efficient targeted locations identified in the subwatershed assessment for potential water quality improvements was an expansion of Whitney Pond. As the final pond before Keller Lake, the existing pond is overcapacity for its current loading from the large contributing watershed. The project will make use of green space in public ownership to expand the treatment volume provided by the existing BMP to achieve an additional 7 lbs of total phosphorus treatment annually. By implementing this project, along with other projects installed in the watershed, the City would meet 79% of the assigned wasteload allocation for external loading.

The proposed expansion would be located primarily in open space owned by the City of Apple Valley, but would also impact land located within the City of Burnsville. The City has been working with a consultant to complete a WBIF (Watershed Based Implementation Funds) grant-funded feasibility study on options for expanding the pond, which has included reviewing multiple concepts and public engagement. The pond's location near two parks with heavily used trail system make it a suitable and sensible location for public outreach. Educational signage around the proposed project would provide an opportunity for public education on water quality and the targeted approaches the City has taken to meet our water quality goals. Including a native buffer around the pond edge will enhance pollinator habitat in the neighborhood and surrounding parkland.

With support from Dakota County , the BDWMO, and the City of Burnsville, the City is eager to implement this targeted stormwater treatment project to achieve reduced TP loading to the lake by approximately 7 additional pounds of TP per year. The project is on targeted priority implementation lists for the City and the Black Dog WMO. The project compliments previously completed external load reduction projects installed by Apple Valley and Burnsville and also supports recently completed internal load reductions, including in-lake alum treatments completed in 2019 and 2021, and native aquatic plant transplant projects that occurred in 2020 and 2022.