Capitol Area Stormwater Management

In its current condition, over 90 percent of the Capitol Area currently receives no stormwater treatment. This means that most of the rain that falls here runs into storm sewers, carrying pollutants such as fertilizer, sediment, oil, pesticides, and bacteria. The path of this polluted stormwater leads directly to the Mississippi River, which flows only a half mile away.

With the exception of key opportunity sites such as the 18-acre former Sears site, the Capitol Area is fully developed, with very limited treatment of stormwater runoff before it reaches the Mississippi River. This study lays the foundation for building future stormwater management practices in coordination with other area improvements, saving both time and money. The location of this study and subsequent projects will likely generate a lot of interest from stakeholders so regular communications will be important.

The neighborhoods in and around the Capitol include Areas of Concentrated Poverty (ACP50) where 50% or more of residents are people of color and 40% of residents live 185% below the federal poverty line. Careful, thoughtful, and inclusive planning will be important to avoid unintended impacts of urban redevelopment such as increased cost of living and displacement of residents.

The Capitol Area is poised to experience significant change over the next several years, with large redevelopment projects, the Capitol Mall redesign, and several roadway/transit improvements in the planning stages. This change presents a tremendous opportunity to manage stormwater runoff differently and to proactively plan for district stormwater systems that use green infrastructure practices.

The Capitol Area Stormwater Management Study (CASMS), linked below, examined opportunities for “district” stormwater management systems (systems serving more than one public or private parcel) that employ “green infrastructure” practices within the Capitol Area. District systems offer efficiencies and can provide additional functions and community benefits beyond stormwater runoff management. Green infrastructure practices capture stormwater runoff for reuse or allow it to soak into the ground instead of running into storm sewers.

The CASMS began with an initial screening of stormwater conditions to identify opportunities for more resilient stormwater management practices and to prioritize areas for focus. Early ideas generated from this process were then used to inform conversations with potential partnering agencies and community organizations. Using results from the screening analyses, feedback from the agency partners, and considering anticipated timelines for redevelopment and capital improvement projects within the Capitol Area, four focus areas were identified for further evaluation of district stormwater systems:

1. The former Sears redevelopment site
2. The University Avenue and Rice Street intersection
3. The Rice Street corridor
4. The Capitol Mall

The goal for each system was to maximize the stormwater and associated community benefits while acknowledging the unique constraints at each site.

To evaluate the costs and benefits of taking a district stormwater approach, a “triple bottom line” (TBL) analysis was used. The TBL approach goes beyond a typical cost-benefit evaluation to consider:

• Economic factors: The economic viability and profitability of a project.
• Social factors: The effect on human well-being and the welfare of the community or stakeholder groups. This includes considerations related to equity, social justice, health, and quality of life.

Environmental factors: The ecological consequences of the project, including water quality, energy consumption or savings, greenhouse gas emissions, and environmental sustainability.

Benefits of district systems in the Capitol Area include

• • Increased volumes of water captured and treated (1.4 to 11 times)
  • Enhanced user experience through the development of urban greening and the creation of three additional park spaces
  • Greater phosphorus removal from runoff (1.3 to 3 times)
  • Opportunities for stormwater reuse storage (up to 2.9 acre-feet)
  • Reduced urban heat island effect and improved air quality
  • Improved return on investment (1.2 to 6.2 times)

Next Steps

CRWD and CAAPB are continuing conversations with potential local, state, and private project partners to further define the opportunities and constraints for district systems within the Capitol Area.

As additional projects within the study area advance through the planning stages, the district stormwater concepts, goals, and guidelines developed through this planning effort will continue to inform the agency partners and encourage a more resilient and integrated approach to managing one of our state’s most precious resources.