Ottawa County study finds human sewage contamination at ‘No Risk’ level in Grand River
The lower Grand River has an image problem when it comes to water quality, but recent monitoring of fecal indicator bacteria suggests that some of the Grand’s historic problems have been remedied.
The Grand River is Michigan’s longest river and, like most large rivers, it has suffered from its share of human use and abuse over the past 150 years. One of the Grand’s historic problems was combined sewer overflows (CSOs) that resulted in raw human sewage flowing into the river during times of heavy rain.
This was a problem not only for the river, but also for beachgoers in Lake Michigan at the mouth of the Grand River in Grand Haven. Beach advisories are recommendations to avoid contact with lake water due to elevated levels of E. coli. Things get a bit tricky here because E. coli is found in the intestines of many animals; including livestock and gulls, and E. coli can persist in the environment for an extended period given the right conditions. That means that beach advisories can result from factors other than human sewage contamination.
During the 2012 beach season, no advisories were issued for Grand Haven beaches. In accordance with the Beach Act, routine monitoring of beaches occurs; however, monitoring of river water is not required. Determination of the source of fecal contamination also is not required, in part, due to the difficulty of doing so. A special study funded by Ottawa County and the Michigan Department of Environmental Quality enabled researchers to do both last summer, and the results were presented on November 1 at the Ottawa County Water Quality Forum in cooperation with Michigan State University Extension.
Senior Environmental Health Specialist Dr. Vijay Kannappan presented results of sampling at five sites along the Grand River in Ottawa County, in addition to beaches north and south of the river mouth. Dr. Kannappan looked at two different fecal indicator bacteria: E. coli and Bacteroides. The E.coli sampling found that levels were below the daily Michigan beach water quality standard at all sites throughout the summer.
The Bacteroides analysis went a step further and determined the sources of fecal contamination in the Grand River. Human Bacteroides levels were extremely low and categorized as “no risk.” The same was true for bovine Bacteroides, indicating “no risk” from cow feces in the Grand. Swine Bacteroides was more prevalent, and scored in the “moderate to low” risk category. The bottom line is that, at least during the 2012 season, human sewage was not a problem in the Grand River. Future work could include development of better methods to track gull and geese feces and investigation of sources of swine feces to the river.
This was a dry summer and lack of rain tends to concentrate bacteria from constant sources such as illicit connections and leaky septic fields. However, combined sewer overflows only happen during heavy rains, and other inputs from agricultural sources are generally lower under dry conditions. Did this year’s drought mask the usual problems from upstream CSOs?