Cedar River IA 02-CED-472

Assessment Comments

Assessment is based on results of IDNR/UHL ambient monthly water quality monitoring near Janesville from 2002-04.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from 2002 through 2004.   Fish consumption uses remain not assessed due to the lack of fish contaminant monitoring in this river segment.   The source of data for this assessment is the results of monthly monitoring from January 2002 through December 2004 at the IDNR ambient monthly monitoring station located near Janesville in Bremer Co.  (STORET station 10090001).  

EXPLANATION:  The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of monitoring from the IDNR ambient station near Janesville from 2002 through 2004.   Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen or ammonia-nitrogen in the 36 samples collected or for pesticides or toxic metals in the 10 samples analyzed during this assessment period.   Levels of pH in this river segment, however, occasionally violate the Class B(WW) criterion of 9.0 pH units.   One of the 36 samples (3%) had pH values greater than the Class B(WW) criterion of 9.0 units (9.2 pH units).     Because these violations are more related to natural conditions (i.e., high levels of primary productivity) than to a pollutant, the occurrence of high levels of pH in this river segment is not seen as a water quality impairment.   Also, according to U.S.  EPA guidelines (U.S.  EPA 1997b, page 3-17), a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen and pH suggest "full support" of aquatic life uses.   Thus, the percentages of violations of the pH criterion at this station (3%) does not suggest an impairment of aquatic life uses in this stream segment.

Fish consumption uses were assessed not assessed due to the lack of recent fish tissue monitoring in this river segment.