Assessment Comments

Assessment is based on results of IDNR ambient monthly monitoring east of Grimes in 2000 and 2001.

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" based on results of ambient chemical/physical water quality monitoring from 2000-02 that show violations of Iowa’s general use criterion for total dissolved solids.   The source of data for this assessment is the results from the INDR/UHL ambient monthly monitoring station on Beaver Creek east of Grimes (STORET station 10770001 (formerly station 420307) from 2000-02.  

EXPLANATION:  Monitoring at the IDNR/UHL station east of Grimes showed no violations of Class B(LR) water quality criteria during the 2000-2002 assessment period for dissolved oxygen, pH, or ammonia-nitrogen in the 36 samples analyzed or for pesticides in the nine samples analyzed.   Four of the 36 samples analyzed, however, exceeded Iowa’s general use criterion of 750 mg/l.   These samples were collected on October 11, 2000 (960 mg/l), January 10, 2001 (880 mg/l), October 9, 2001 (780mg/l), and January 8, 2002 (860 mg/l).   The similarity in the months of these violations suggest some type of scheduled, reoccurring releases to this stream.