The Milwaukee Metropolitan Sewerage District (MMSD) provides wastewater treatment and flood management services for 1.1 million people over 411 sq miles in the greater Milwaukee area. The regional government agency encompasses or includes six watersheds.
In 2000, MMSD launched its storm water program—not for regulatory purposes, but rather as a voluntary research initiative. As part of the program, MMSD collects storm water during storm events when possible and samples surface water immediately after rain, snowmelt and baseflow events as a rule to assess environmental impacts. The resulting data supports the district’s 2020 Facilities Plan, intended to identify the facilities, programs, operational improvements and policies it will need by 2020 to comply with existing permits and additional regulatory requirements.
“The district is being proactive to solve the region’s problems rather than leaving local entities to do it themselves,” said MMSD Public Information Manager Bill Graffin.
Scope & Methods
At the outset of its monitoring program, MMSD researched storm water on 15 sites with various land uses—residential and recreational to highway and industrial. That number is up to 20 today, with staff conducting monitoring during the months of April to October. The smallest site drainage area measures 1.42 acres, and the largest covers 792 acres; these sites and all those in between feed a variety of receiving water bodies, including the Menomonee River and Lake Michigan.
The district’s sampling is modeled after NR216 protocols (e.g., a 72-hour antecedent dry period and four weeks between events). Taken from storm sewers to represent the first and second flush, samples are tested for up to 30 contaminants—up from 20 in 2000—including fecal coliform,
E. coli, ammonia, nitrogen, trace metals and total organic carbon. They are then sent to the nearby Great Lakes Water Institute (GLWI) for analysis and to help develop the DNA Bacteriodes, or human genetic marker, test method.
“Fecal pollution from different sources will carry different pathogens; however, fecal pollution from sanitary sewage generally constitutes a more serious public health risk because multiple human pathogens, including bacteria, viruses and protozoan can be present in high concentrations,” said Mary Singer, MMSD water resources program supervisor. “This human-specific Bacteroides genetic marker is a sensitive, specific indicator of sanitary sewage contamination and therefore can be used to evaluate whether sanitary waste is entering the storm water collection and conveyance system.”
In 2007, MMSD and GLWI isolated storm water outfalls at an area business where fecal coliform and Bacteriodes measurements indicated a possible cross-connection with sanitary sewers. The groups identified and eliminated the source of contamination via dye testing.
Most recently, MMSD’s Stormwater Program has focused on sites labeled “areas of concern,” so called due to persistently high bacteria levels or a majority of storm water samples testing positive for the genetic human marker. The district continually is increasing its sampling locations and frequency as well as partnerships and information sharing with watershed communities and nongovernmental organizations in an effort to eliminate these problem spots.
Continuing its work with GLWI, MMSD also will work in 2010 to develop faster, more cost-effective field methods to screen storm water outfalls and find potential sanitary sewer/storm water cross-connections. Staff members hope to achieve this goal by discovering correlations between field parameters and other test results.
“Finding and eliminating illicit discharges will improve water quality in ‘our’ watersheds while providing a model to enhance water quality elsewhere,” Singer said.