Assessment Comments
Assessment is based on results of (1) monthly monitoring at the IDNR fixed ambient station near DeWitt from 2002-04, (2) LTRMP monitoring near the mouth of the Wapsipinicon River from 2002-04, (3) USGS monitoring near DeWitt from 2002-04, and (4) EPA/IDNR fish tissue (RAFT) monitoring north of Donahue in Scott County in 2004.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were assessed (monitored) as "not supported" due to high levels of indicator bacteria (E. coli). The Class B(WW) aquatic life were assessed (monitored) as "fully supported" based on results of ambient chemical/physical water quality monitoring from 2002-04. Fish consumption uses were assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2004. The sources of data for this assessments were (1) the results of monthly monitoring at the IDNR fixed ambient station near DeWitt (station 10820001) from 2000-04, (2) results of LTRMP ambient water quality monitoring near the mouth of the Wapsipinicon River (station WP02.6M) from 2002 to 2004; (3) results of USGS ambient monitoring near DeWitt from 2002 to 2004 (station 05422000), and (4) results of EPA/IDNR fish tissue (RAFT) trend monitoring north of McCausland in 2004. Note: this assessment is also used for the next upriver segment, IA 01-WPS-0010-2.
EXPLANATION: The Class A (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 2006 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 (164 orgs/100ml) from the IDNR ambient station is greater than 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 value 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). Thus, while the Class A uses of this segment were assessed as “partially supported” for the 2004 reporting cycle due to high levels of fecal coliforms, these uses are now assessed as “not supported” for the 2006 cycle due to high levels of E. coli.
The Class B(WW) aquatic life uses were assessed as "fully supported" due to (1) the lack of violations of Iowa Class B(WW) water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the approximately 36 samples collected from January 2002 through December 2004 at the IDNR fixed ambient station at DeWitt and in the 47 samples collected at the LTRMP station near the mouth of the river from 2002-2004, and (2) the lack of violations of Class B(WW) water quality criteria in the 10 samples from the IDNR ambient station analyzed for pesticides and toxic metals during the 2002-2004 assessment period. Also, no violations of Class B(WW) criteria occurred for dissolved oxygen, pH, ammonia, dieldrin, DDE, or chorpyrifos in the nine samples collected from June 2002 through September 2004 by USGS from their ambient monitoring at DeWitt.
Fish consumption uses are assessed as "fully supported" based on the 2004 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 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish sample of common carp: mercury: 0.141 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.083 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 RAFT sampling (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.
