Location: St. Paul, Minnesota
Client: Capitol Region Watershed District
Background
In 2016, the Capitol Region Watershed District (CRWD) hired HEI to complete an inventory of storm sewers in Como Park, document constructed best management practices (BMPs) in the Como Lake Watershed, and analyze existing pollutant loads delivered to Como Lake. Once these were completed, large-scale BMPs were identified that aligned with the Como Regional Park Stormwater Master Plan. Due to the timing with planned projects and the complexity of a large stakeholder group, the BMP feasibility assessment for these practices was expedited.
The Project
Ten BMP locations were evaluated for their potential to treat stormwater. Many of these locations were chosen due to their location relative to anticipated park improvement projects so that the BMPs can be used to treat the upcoming projects.
To begin, HEI analyzed existing data, completed a planning level Gopher One call to be sure no utilities would affect the function or construction of a BMP, and completed 13 soil borings for anticipated infiltration BMP locations. HEI then completed a survey to capture any missing storm sewer or utility data and held an on-site walk-through with the project partners.
From these tasks, HEI conceived of 21 potential BMPs for Como Park, most notably iron-enhanced sand filters (IESF), including IESF benches, due to their ability to remove dissolved phosphorous. Other concept designs included underground systems, pumped IESFs, infiltration, and a creative infiltrating stream design.
From the 21 options, the project partners chose nine concept BMPs, which HEI refined. The BMPs were prioritized for cost-effective water quality performance based on:
- volume reduction goals,
- a water quality assessment and modeling,
- an estimate of costs, and
- a cost-benefit analysis.
HEI provided recommended BMPs and treatment trains based on their cost-effectiveness and their ability to meet the goals outlined in the Stormwater Management Plan.
Client Benefits
- Several BMP concepts for project partner review and selection.
- Cost-effectiveness analysis for each potential BMP.
- IESF design recommendations to promote performance and longevity.
- Complex water conveyance system of diversions, treatment train BMPs, and pumps.
- Innovative and creative BMP designs, including adaptive, remote-control of BMPs’ functionality.