Stormwater BMPs are activities, practices, and structures designed to reduce stormwater pollution and stormwater runoff volume and increase groundwater recharge. CRWD, in partnership with local units of government and other entities, has been designing and implementing stormwater BMPs throughout the watershed to minimize the impacts of stormwater and improve the water quality of CRWD water resources.
CRWD operates and maintains some of these BMPs and assesses their effectiveness in reducing stormwater runoff and removal of pollutants such as phosphorous. Those BMPs include the Villa Park Wetland System in Roseville and the eighteen BMPs constructed for the Arlington Pascal Stormwater Improvement Project in St. Paul and four BMPs in the Green Line Light Rail project area in St. Paul.
To view a map of the BMPs, click here.
To view a map of the Arlington Pascal Stormwater Improvement Project BMPs, click here.
To view a map of the BMPs constructed in the CCLRT project area, click here.
To view a map of the Villa Park Wetland System, click here.
BMP Maintenance and Monitoring
CRWD regularly inspects and maintains all of the BMPs. This helps to maintain and ensure that they are operating efficiently.
CRWD also monitors the inlet and outlet of the Villa Park Wetland System and four of the Arlington Pascal Stormwater Improvement Projects BMPs (two infiltration trenches, the underground stormwater facility and the stormwater pond). In addition, the peak water level reached in each rain garden during storm events, are also measured. The collection of this data enables CRWD to determine the amount of stormwater runoff and pollutants entering and exiting each BMP; thus yielding the amount of runoff and pollutants removed by each BMP during the monitoring season.
BMP Performance Assessment
The monitoring data collected on the four monitored Arlington Pascal Stormwater Improvement Project BMPs were used to calibrate a water quality model. This model simulated the amount of stormwater runoff and pollutants which flowed to and from all eighteen Arlington Pascal Stormwater Improvement Project BMPs in a calendar year. Modeling efforts are necessary because Minnesota winters prohibit monitoring data from being collected year round. This data, in addition to actual construction, design, and operation and maintenance costs for each individual BMP, were used to determine the cost-benefit (the cost per pound of pollutants removed and the cost per unit of volume reduction) of each BMP.
For detailed results of the BMP performance and cost-benefit analysis, visit our Reports Page.
Additional Monitoring and Analysis
Some of the Arlington Pascal Stormwater Improvement Project BMPs incorporate pretreatment units into their design to help maintain the effectiveness of the BMPs at infiltrating stormwater runoff and removing pollutants. Those units include 30 sumped catch basins and 15 sumped manholes which pretreat stormwater runoff flowing to the eight infiltration trenches as well as a hydrodynamic swirl separator which pretreats runoff flowing to the underground stormwater storage and infiltration facility. All of the pretreatment units help to capture gross solids (trash, organic matter, and sand/gravel) that would otherwise accumulate within the BMP.
CRWD undertook additional monitoring efforts to determine the amount of gross solids captured by each pretreatment unit as well as the amount of gross solids which accumulated within the BMPs. Additionally, the amount of phosphorous contained in the gross solids was also determined. The results of this study were incorporated in to the BMP performance analysis described above. Detailed results of the gross solids accumulation study can be found in the Arlington Pascal Gross Solids Accumulation Study on our Reports Page.