St. Louis MSD Green Infrastructure Pilot Program

Abstract

The Metropolitan St. Louis Sewer District (MSD) is a regional sewer district that provides wastewater and stormwater services to the City of St. Louis and most of St. Louis County, Missouri. The service area includes a combined sewer system (CSS) in the City and the older portions of the County. In 2011, MSD completed a Combined Sewer Overflow Long-Term Control Plan (CSO LTCP), which was formalized in a Consent Decree (CD) with the U.S. Environmental Protection Agency (EPA) in April, 2012. MSD’s combined sewer overflow (CSO) control plan includes a $100 million green infrastructure (GI) program in the portions of the City that flow directly to the Mississippi River outfalls. To build implementation experience, and to test and resolve the numerous anticipated regulatory, logistical and financial aspects of the projects, MSD is conducting a $3 million, five year pilot program, culminating in a final report in 2015. The pilot program includes construction of demonstration projects, a monitoring program, and education and outreach to solicit feedback from the community. This paper will document the process and lessons learned from siting, design, and construction of six “neighborhood-scale” bioretention projects constructed for the pilot program. Opportunities and challenges discussed include working with multiple stakeholders; forecasting future conditions; designing with urban retrofit realities of buried rubble, intact foundations, and potential environmental concerns; and addressing maintenance and warranty issues. Through this work, MSD has integrated green infrastructure into processes and procedures traditionally used for gray infrastructure systems, as well as developed details and specifications that can be used during the full-implementation of the GI program.