Assessment Comments

Assessment is based on: (1) the results of monthly monitoring at the IDNR fixed ambient station near DeWitt (station 10820001) from 2006-09, (2) results of LTRMP ambient water quality monitoring near the mouth of the Wapsipinicon River (station WP02.6M) from 2004 to 2006; (3) results of USGS ambient monitoring near DeWitt from 2006 to 2008 (station 05422000), and (4) results of EPA/IDNR fish tissue (RAFT) trend monitoring north of McCausland in 2006 and 2008.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria (E.   coli).   The Class B(WW1) aquatic life are assessed (monitored) as "fully supported" based on results of ambient chemical/physical water quality monitoring from 2006-08.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring.   The sources of data for this assessments are (1) the results of monthly monitoring at the IDNR fixed ambient station near DeWitt (station 10820001) from 2006-08, (2) results of LTRMP ambient water quality monitoring near the mouth of the Wapsipinicon River (station WP02.6M) from 2006 to 2008; (3) results of USGS ambient monitoring near DeWitt from 2006 to 2008 (station 05422000), and (4) results of EPA/IDNR fish tissue (RAFT) trend monitoring north of McCausland in 2004, 2006, and 2008.   Note:  this assessment is also used for the next upriver segment, IA 01-WPS-0010-2.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria.   The geometric mean level of indicator bacteria (E.   coli) in the 21 samples collected at the IDNR ambient monitoring station during the recreational seasons of 2006 through 2008 (264 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   According to U.S.   EPA guidelines for Section 305(b) reporting and the IDNR assessment/listing methodology, if the geometric mean level of E.   coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35of U.S.   EPA 1997b).  

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" due to the lack of violations during the 2006-08 period of Iowa Class B(WW) water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in (1) the approximately 32 samples collected from at the IDNR fixed ambient station at DeWitt, (2) in the 41 samples collected at the LTRMP station near the mouth of the river, and (3) in the 34 from the USGS ambient monitoring station at DeWitt.   In addition, no violations of Class B(WW1) water quality criteria for toxic metals or pesticides occurred during this period in the two samples from the IDNR ambient station or in the one sample analyzed for toxic metals from the USGS ambient monitoring station at DeWitt.  

Fish consumption uses are assessed (monitored) as "fully supported" based on the 2006 and 2008 EPA/IDNR fish tissue (RAFT) sampling on the Wapsipinicon River north of McCausland.   This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring.   The results from the 2006 and 2008 samplings show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish samples of common carp.   In the 2006 sample, the levels of contaminants were as follows: mercury: 0.053 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.03 ppm.   In the 2008 samples, the levels were as follows:  mercury:  0.0959 ppm; total PCBs:  0.09 ppm; and technical chlordane:  0.042 ppm.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   The fish contaminant data generated from the 2006 and 2008 RAFT sampling conducted at this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.