In 2011, GRWW and the Grand Valley Metro Council received an EPA grant to conduct sediment testing in the area between the Sixth Street Dam and Ann Street. Limited sediment was found but it was tested and deemed acceptable. Of the 45 sample points, only one returned a slightly elevated level of arsenic, a commonly found element in Michigan waterways.
In 2020, the U.S. Army Corps of engineers conducted a similar sediment sampling upstream of the Sixth Street dam. All of the results were below the limits of Michigan’s Soil Direct Contact Criteria for both residential and non-residential areas, except for two locations that exceeded the limits for arsenic.
In 2020 the City and GRWW also conducted sediment sampling behind the dams in the lower reach. The State requires contaminant test when sieve grain analysis is less than 90% sand, on average. For the 11 samples taken, all locations were greater than 95% sand, except 1 sample. The City and GRWW decided to have the samples tested and no concentrations of any analytes were tested that exceeded any of the established screening guidelines per the State’s guidance on Sediment Testing for Dredging Projects or any known preceding screening guidelines.