Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient monthly monitoring SW of Waterloo from 2000-02, (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 1998, and (3) IDNR/UHL ambient monitoring at three sites in 2001 as part of TMDL development.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses were assessed (monitored) as "not supported" due to high levels of indicator bacteria that violate state water quality standards.   The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 1998.   Sources of data for this assessment include (1) results monthly monitoring from January 2000 through December 2002 at the IDNR ambient station at Ridgeway Avenue SW of Waterloo (station 10070004), (2) results from monthly monitoring conducted at three additional locations in this stream segment from March to November 2001 as part of monitoring in support of TMDL development, and (3) U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 1998 near Hudson.  

EXPLANATION:  The Class A (primary contact recreation) uses were assessed as "not supported" due to levels of indicator bacteria (fecal coliforms) that violate Iowa’s Class A water quality criteria  The geometric mean of indicator bacteria (fecal coliforms) in the 21 samples not materially affected by surface runoff during the recreational seasons of 2000, 2001, and 2002 at the IDNR ambient monitoring station exceeded the Iowa water quality criterion to protect primary contact recreation uses.   For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff.   According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff."  The geometric mean of fecal coliform bacteria in the 21 non-runoff-affected samples was 240 orgs/100 ml, with eight samples (38%) exceeding the EPA-recommended single-sample maximum value of 400 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean is greater than 200 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   Results of monitoring at the three TMDL stations during the recreational season of 2001 are consistent with this assessment:  geometric means in six non-runoff affected samples at these stations ranged from 563 to 880 organisms/100 ml (N=6) with from 67 to 83% of the samples exceeding the single-sample maximum value of 400 organisms/100 ml.  

The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of monitoring from the IDNR ambient station SW of Waterloo from 2000 through 2002 and from the three stations monitored in 2001 in support of TMDL development for this stream reach.   Monitoring at these four stations show no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen.   In addition, no violations of state criteria for toxic metals and toxic organic compounds occurred in the nine samples analyzed during the assessment period for pesticides from the ambient monitoring station..  

Fish consumption uses remain assessed (monitored) as "fully supported" based on the results of EPA/DNR fish tissue (RAFT) sampling in 1998 near Hudson (see assessment for the 2000 report).