Assessment Comments
Assessement is based on results of (1) IDNR/UHL city monthly monitoring downstream from Ottumwa from 2000-02 and (2) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 1999 and 2001.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were assessed (monitored) as "partially supported" due to high levels of indicator bacteria. The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported / threatened" based on results of IDNR/UHL ambient water quality monitoring that showed one violation of state criteria for the pesticide chlorpyrifos. Fish consumption remain assessed as "fully supported / threatened" based on results of fish contaminant monitoring in 1999 and 2001. The sources of data for this assessment include (1) results from the IDNR ambient city monitoring station downstream from Ottumwa at Cliffland Road (STORET station 10900002) from 2000 through 2002 and (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 1999 and 2001.
EXPLANATION: The Class A uses were assessed as "partially supported" due to high levels of indicator bacteria (fecal coliforms). 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." Fourteen of the 16 samples collected from the Cliffland Road station during the 2000, 2001, and 2002 recreational seasons were collected at flows not materially affected by surface runoff. The geometric mean level of indicator bacteria (fecal coliforms) in these 7 non-runoff-affected samples (154 orgs/100ml) is below the Iowa Class A water quality criterion of 200 orgs/100ml. However, three of the 14 samples (21%) exceeded the U.S. EPA-recommended single-sample maximum value of 400 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% or less of the samples exceed the single-sample maximum value of 400 orgs/100 ml, the primary contact recreation uses are "partially supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
The Class B(WW) aquatic life uses were assessed as "fully supported / threatened" based on results of monitoring from the IDNR ambient station downstream from Ottumwa at Cliffland Road from 2000 through 2002 that show a single violation of state criteria for the pesticide chlorpyrifos. Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, or toxic metals in the 28 samples analyzed. One of the nine samples analyzed for pesticides and other toxic organic compounds, however, contained a level of chlorpyrifos that exceeded state water quality criteria. The sample collected on December 3, 2001, contained 0.074 ug/l of chlorpyrifos; this level exceeds the state water quality criterion of 0.041 ug/l. Thus, based on IDNR assessment procedures, the Class B(WW) uses are assessed (monitored) as "fully supported / threatened."
Fish consumption uses remain assessed as "fully supported /threatened." Results of EPA/DNR fish tissue (RAFT) monitoring in 2001 continued to show that levels of technical chlordane in composite samples of bottom feeding fish exceeded one-half the FDA action level (0.30 ppm). The composite sample of channel catfish fillets analyzed for the 2001 RAFT contained 0.150 ppm of technical chlordane. Although approximately half the level seen in the partial sample of channel catfish fillets collected in 1999 (0.290; see assessment for the 2000 report above), this level is nonetheless equal to one-half the FDA action level of 0.300 ppm. In addition, this sample contained 1.03 ppm of total PCBs (=sum of Aroclors 1248, 1254, and 1260); this level of PCBs is slightly greater than one-half of the FDA action for PCBs of 2.0 ppm. Based on DNR's assessment methodology, these contaminant levels continue to suggest that fish consumption uses should be assessed as "fully supported/threatened." Additional fish tissue monitoring was conducted as part of follow-up monitoring for the 2003 RAFT program to better determine levels of chlordane and PCBs in the bottom-feeding fish of this river segment. The results from this monitoring are not yet available.
