Assessment Comments
Assessement is based on (1) results of IDNR city monthly monitoring downstream from Ottumwa during 2000-01 and (2) fish tissue (RAFT) monitoring in 1997, 1999, & 2001.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were assessed (evaluated) as "partially supported," and the Class B(WW) aquatic life uses were assessed (monitored) as "fully supported." Fish consumption remain assessed as "fully supported / threatened." The sources of data for this assessment include (1) results from the IDNR ambient city monitoring station downstream from Ottumwa at Cliffland Road (station 10900002) in 2000 and 2002 and (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2001. EXPLANATION: The Class A uses were assessed as "partially supported." 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." Seven of the 9 samples collected from the Cliffland Road station during the 2000 and 2001 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 (165 orgs/100ml) is below the Iowa Class A water quality criterion of 200 orgs/100ml. However, two of the 7 samples (29%) 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). Because less than 10 non-flow affected samples were available for this assessment, the assessment type is considered "evaluated"; thus, this assessment is not of sufficient quality to support a Section 303(d) listing. The Class B(WW) aquatic life uses were assessed as "fully supported" based on results of monitoring from the IDNR ambient station downstream from Ottumwa at Cliffland Road in 2000 and 2001. Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, ammonia-nitrogen, or toxic metals in the 14 samples analyzed, or for pesticides and other toxic organic compounds in the six samples analyzed, during this biennial period. The levels of pH, however, violated the Class B(WW) criterion of 9.0 pH units in one sample. The sample collected on November 2, 1999 had a pH level of 9.3 units which is greater than the Iowa water quality standard of 9.0 pH units. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b: page 3-17), however, a violation frequency for conventional parameters (including pH) of 10% or less does not suggest an impairment of aquatic life uses. Thus, the Class B(WW) uses are assessed as "fully supported." Fish consumption uses remain assessed as "fully supported /threatened." Results of EPA/DNR fish tissue (RAFT) monitoring in 2001 continue to show that levels of technical chlordane in composite samples of bottom feeding fish exceed 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 will be conducted as part of follow-up monitoring for the 2003 RAFT to better determine levels of chlordane and PCBs in the bottom-feeding fish of this river segment.
