Assessment Comments
Assessment is based on: (1) results from the IDNR/UHL ambient city monitoring station downstream from Ottumwa at Cliffland Road (STORET station 10900002) from 2008 through 2010, (2) reports of fish kills and supplemental information from the IDNR Fisheries Bureau, (3) results of IDNR/UHL biological (REMAP) monitoring in 2003, and (4) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2003 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). Similar to the adjacent downriver segment (IA 04-LDM-0010-4), the Class B(WW1) aquatic life uses are assessed (monitored) as "partially supported" based on the occurrence of repeated kills of shovelnose sturgeon in this river segment over the last 10 years. Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2003 and 2006. The sources of data for this assessment include (1) results from the IDNR/UHL ambient city monitoring station downstream from Ottumwa at Cliffland Road (STORET station 10900002) from 2008 through 2010, (2) reports of fish kills and supplemental information from the IDNR Fisheries Bureau, (3) results of IDNR/UHL biological (REMAP) monitoring in 2003, and (4) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2003 and 2006.
EXPLANATION: The Class A1 uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria (E. coli). The geometric means of indicator bacteria (E. coli) in the 22 samples collected during the recreational seasons of 2008 through 2010 at IDNR station 10900002 downriver from Ottumwa were as follows: the 2008 geometric mean was 184 orgs/100 ml, the 2009 geometric mean was 238 orgs/100 ml and the 2010 geometric mean was 93 orgs/100 ml. The 2008 and 2009 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2010 geometric mean meets the Class A1 criterion. Eight of the 22 samples (36%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”
The Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supported” due to fish kills on July 31, 2002 and on July 10, 2006 on the reach of river between Eldon (Wapello Co.) and Douds (Van Buren Co.). These recent kills are two in a series of kills that have occurred over the last ten years or so that appear to involve primarily shovelnose sturgeon (Scaphirhynchus platorynchus). Although the cause of the 2002 and 2006 kills and the previous kills remains unknown, the leading hypotheses are (1) that very high water temperatures, very low river flows, and elevated pH levels combine to make ambient levels of ammonia in the river toxic to the ammonia-intolerant shovelnose sturgeon and (2) that the kills are caused by a virus specific to shovelnose sturgeon. Note: According to the local IDNR Fisheries biologist, a severe fish kill was reported on the lower Des Moines River on July 7, 2012, from approximately Eldon (downriver from Ottumwa) to Farmington in Van Buren County. An estimated 57,000 fish were killed including at least 35,000 shovelnose sturgeon. No specific cause of the kill was identified, but low flow conditions, flow alterations, and very high water temperatures (95+F) are believed to have contributed to the kill.
According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates that the aquatic life uses of a waterbody are only "partially supported.” Thus, the Class B(WW1) aquatic life uses of this river reach were assessed as "partially supported.” Also, according to IDNR’s assessment methodology, if a cause of a fish kill was not identified during the IDNR investigation (cause = "unknown"), or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, typically lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (Category 5 of the Integrated Report). Waterbodies affected by such fish kills at usually placed in IR subcategories 2b or 3b and are added to the state’s list of “waters in need of further investigation”. Due however to (1) the repeated occurrence of these kills over the last 10 years, (2) the often large numbers of sturgeon killed (thousands), and (3) the likelihood that these kills are caused by a pollutant, this impairment was added to, and remains on, Iowa’s Section 303(d) list (Category 5 of the Integrated Report).
In contrast to the poor water quality suggested by the reoccurring fish kills, results of ambient chemical/physical water quality monitoring from the IDNR/UHL station downstream from Ottumwa at Cliffland Road from 2008 through 2010 show no violations of Class B(WW1) criteria and suggest generally good water quality. Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the approximately 30 samples analyzed or for toxic metals and pesticides in the three samples analyzed.
Results of biological monitoring conducted in 2003 also suggest “full support” of the aquatic life uses. This assessment is based on data collected in 2003 as part of the IDNR/UHL stream REMAP project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2003 FIBI score was 40 (fair) and the BMIBI score was 46 (fair). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41. This assessment is considered evaluated because the drainage area (13,443 mi2) above this sampling site was far greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.
Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) follow-up monitoring at the Cliffland Access downriver from Ottumwa in 2003 and 2006. The 2003 composite samples of fillets from channel catfish had low levels of the primary contaminants (mercury, PCBs, and chlordane). mercury: 0.157 ppm; total PCBs: 0.17 ppm; and technical chlordane: 0.081 ppm. The 2006 composite samples of fillets from channel catfish also had low levels of the primary contaminants: mercury: 0.115 ppm; total PCBs: 0.114 ppm; and technical chlordane: 0.048 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. Although results of previous fish contaminant monitoring showed that this river segment has a history of somewhat elevated levels of chlordane in fish, the levels of chlordane in the 2003 and 2006 RAFT follow-up samples are well below the IDPH/IDNR advisory trigger level of 0.6 ppm. Also, the levels of the other contaminants did not exceed the new (2006) advisory trigger levels for mercury and PCBs, thus suggesting no justification for issuance of a consumption advisory.
