Assessment Comments
Assessment is based on (1) observations and photo documentation by IDNR staff in 2005 and (2) results of weekly chemical monitoring conducted by IDNR staff from May 2005 through July 2006.
Basis for Assessment
SUMMARY: The general uses of this stream are assessed (monitored) as "not supported" due to impacts of poorly-treated wastewater discharged to the stream. This assessment is based on results of observations and water quality monitoring conducted by IDNR staff in 2005 and 2006. IDNR has documented accumulations of sewage sludge in the channel of this stream; these conditions are a violation of the narrative criteria in the Iowa Water Quality Standards that protect against accumulations of sewage sludge in Iowa streams. The sources of data for this assessment include (1) results of observations and photo documentation by IDNR staff in 2005 and (2) results of weekly chemical monitoring conducted by IDNR staff from May 2005 through July 2006 at three locations from North Liberty downstream to First Avenue in Coralville, IA. This stream was not assessed for purposes of Section 305(b) assessment or Section 303(d) listing prior to the 2006 assessment/listing cycle.
EXPLANATION: A survey conducted in October 2005 by IDNR staff documented accumulations of sewage sludge in Muddy Creek downstream from the North Liberty wastewater treatment facility. Accumulations of sludge were up to 12 inches deep and occurred up to one-half mile downstream from the wastewater treatment facility. In addition, results of water quality monitoring from May 2005 through July 2006 show acutely toxic levels of ammonia occurring on December 5, 2005. The accumulations of sewage sludge and poor water quality conditions observed and reported by IDNR staff potentially violate several of Iowa's narrative water quality standards (IAC 61.3(2)) designed to protect general uses of Iowa's surface waters (e.g., livestock and wildlife watering, aquatic life and non-contact recreation):
--such waters shall be free from substances from point source dischargers that will settle to form sludge deposits;
--such waters shall be free from floating debris, oil, grease, scum and other materials from wastewater discharges or agricultural practices in amounts sufficient to create a nuisance;
--such waters shall be free from materials from wastewater discharges or agricultural practices producing objectionable color, odor, or other aesthetically objectionable conditions;
--such waters shall be free from substance attributable to wastewater discharges or agricultural practices in concentrations or combinations which are acutely toxic to human, animal, or plant life.
Based on the information received by IDNR on this stream, the general uses are assessed (monitored) as "not supported" due to water quality impacts from poorly-treated domestic sewage being discharged to Muddy Creek. Waters assessed as “monitored/not supported” are considered appropriate for addition to Iowa’s Section 303(d) list of impaired waters.
