McLoud Run IA 02-CED-508

Assessment Comments

Assessment is based on fish kills caused by watermain breaks in summer 1997 and by urban runoff in 2001.

Basis for Assessment

SUMMARY:  The general (aquatic life) uses remained assessed as "partially supported."  EXPLANATION:  The previous assessment of support for the general beneficial uses of this stream ("partially supporting" the general aquatic life uses) was based on the occurrence of two spill-related fish kills during the 1996-1997 biennial assessment period (see assessment developed for the 1998 and 2000 reports).   The most recent fish kill, however, occurred on August 2, 2001 and was due to storm water runoff from urban watershed of this stream.   The rainfall event occurred during very warm summer weather, and the relatively warm runoff water raised the temperature of McCloud Run by 19 degrees F in an hour.   Temperature-sensitive species such as the (stocked) rainbow, brown, and brook trout were killed.   According to DNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period (1997-1999) indicates that the aquatic life uses of a waterbody are only "partially supported."  Thus, the general aquatic life uses of this stream remain assessed as "partially supported" due thermal impacts from urban runoff.   In addition to impacts of fish kills, fish tissue monitoring conducted in June 2001 following a mid-May fish kill showed that fillet samples of stocked trout (ages 1 and 2) contained levels of chlordane above the 0.300 ppm U.S.  FDA action level.   A second fish tissue sampling in July 2001 showed that levels were just below the FDA action level.   In response, the IDNR Fisheries Bureau has issued a no-kill restriction on trout taken from McCloud Run.   For purposes of Section 305(b) assessment, the general aquatic life uses of McCloud Run are considered "threatened" by the pesticide chlordane.