Assessment Comments

Assessment is based on: (1) the results of monthly monitoring at the IDNR fixed ambient station near DeWitt (station 10820001) from 2004-06, (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 2004 to 2006 (station 05422000), and (4) results of EPA/IDNR fish tissue (RAFT) trend monitoring north of McCausland in 2004 and 2006.

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 2004-06.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2004 and 2006.   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 2004-06, (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 2004 to 2006 (station 05422000), and (4) results of EPA/IDNR fish tissue (RAFT) trend monitoring north of McCausland in 2004 and 2006.   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.   Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, E.  coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of the 2006 Section 305(b) assessments and Section 303(d) listings.  

The geometric mean level of indicator bacteria (E.  coli) in the 24 samples collected at the IDNR ambient monitoring station during the recreational seasons of 2004 through 2006 (137 orgs/100ml) slightly exceeds the Iowa Class A water quality criterion of 126 orgs/100ml.   In addition, nine of the 24 samples (38%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   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 2004-06 period of Iowa Class B(WW) water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in (1) the approximately 36 samples collected from at the IDNR fixed ambient station at DeWitt, (2) in the 45 samples collected at the LTRMP station near the mouth of the river, and (3) in the 35 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 10 samples from the IDNR ambient station or in the ten samples analyzed for toxic metals from the USGS ambient monitoring station at DeWitt.

Fish consumption uses are assessed as "fully supported" based on the 2004 and 2006 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 2004 and 2006 samplings show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish samples of common carp.   In the 2004 sample, the levels of contaminants were as follows:  mercury:  0.141 ppm; total PCBs:  0.09 ppm; and technical chlordane:  0.083 ppm.   In the 2006 samples, the levels were as follows:  mercury:  0.053 ppm; total PCBs:  0.09 ppm; and technical chlordane:  0.03 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.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.   This scenario, however, does not apply to the fish contaminant data generated from the 2004 or 2006 RAFT samplings (or from previous RAFT trend monitoring) conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.