Much of the City of St. Louis is located within the combined sewer overflow (CSO) area, meaning stormwater from the street is mixed with sanitary sewage.  During large rain events, the system becomes overwhelmed, resulting in raw sewage being discharged into the Mississippi River.  In 2011, Metropolitan Sewer District (MSD) entered a consent decree agreement with the Environmental Protection Agency and the Missouri Coalition for the Environment, requiring MSD to spend a minimum $4.7 billion over the next 23 years to address the issue of overflows and other sewer system improvements.

DTLS led the design of site renovations at the MSD headquarters aimed at showcasing the organization’s mission of reducing negative stormwater impacts, while supporting public education and enhancing accessibility.  The plan incorporated many green infrastructure best practices recommended in the guidelines adopted by MSD to reduce stormwater runoff.  The design strategies included lawn reduction, bioretention, permeable pavement, bioswales, a green roof, and water harvesting.  Meanwhile, new accessible parking spaces, connections to perimeter sidewalks, and a ramp were incorporated into the design of the main entry plaza, an area which was previously inaccessible to visitors with limited mobility.

The material palette was focused on regional sources and utilitarian elements which reflect MSD’s responsible stewardship of public funds. Limestone walls were sourced from southern Missouri and the plantings are entirely composed of local native species.  Thermally-modified wood from ash trees were selected for wood furnishings, cladding, and decking.  City standard concrete and galvanized steel elements reflect the utilitarian nature of the District.

The design process was guided by stakeholder review and feedback sessions which included polling and in-person design workshops.  The engagement process led MSD to prioritize the incorporation of demonstration and interpretive education as part of the site design.  Accordingly, DTLS designed nine educational signs illustrating the flow of water through the site, explaining each stormwater management method, describing measurable benefits of design solutions, and identifying native plant species.  These signs also provide visitors with tips and inspiration for implementing green infrastructure practices in their home landscapes, a fundamental objective of the consent decree.