Assessment Comments
Assessement is based on results of (1) IDNR/UHL city monthly monitoring downstream from Ottumwa from 2002-04, IDNR/UHL biological (REMAP) monitoring in 2003, and (3) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2001 and 2003.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses remain assessed (monitored) as "not supported" due to high levels of indicator bacteria (E. coli). Similar to the adjacent downriver segment (IA 04-LDM-0020-1), the Class B(WW) 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 are assessed (monitored) as "fully supported " based on results of fish contaminant monitoring in 2001 and 2003. 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, (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 2001 and 2003.
EXPLANATION: The Class A uses were assessed as "not supported" due to high levels of indicator bacteria (E. coli). 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 collected during the recreational seasons of 2002 through 2004 (148 orgs/100ml) slightly exceeded the Iowa Class A water quality criterion of 126 orgs/100ml. In addition, 8 of the 24 samples (33%) exceeded Iowa’s single-sample maximum value of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s 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). Also, these EPA guidelines state that if more than 10% of the samples exceed the state’s single-sample maximum criterion, the primary contact recreation uses should be assessed as “partially supported”. According to IDNR’s assessment/listing methodology, these results suggest that significantly greater than 10% of the samples exceed IDNR’s single-sample maximum value, thus suggesting that the Class A uses should be assessed as “partially supported/impaired”. Thus, both the geometric mean and the percentage of violations of Iowa’s single-sample maximum criterion (33%) suggest impairment of the Class A uses of this river segment.
The Class B(WW) aquatic life uses were assessed (monitored) as “partially supported” due to the repeated occurrence of kill of shovelnose sturgeon in this and the adjacent downriver segment of the Des Moines River (note: the most recent kill in this river segment—and a particularly large kill—occurred in July 2006). According to the IDNR Fisheries Bureau, these kills have occurred over the last ten years or so and appear to involve only shovelnose sturgeon (Schaphirynchus platorynchus). Although the cause of these kills remains unknown, the leading hypotheses are (1) that very high water temperatures and very low river flows 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.
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 (2002-2004) indicates that the aquatic life uses of a waterbody are only "partially supported." Thus, the Class B(WW) aquatic life uses of this river reach were assessed as "partially supported." Also, according to IDNR’s assessment methodology, if a cause of a fishkill 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 is being added to 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 station downstream from Ottumwa at Cliffland Road from 2002 through 2004 show few violations of Class B(WW) criteria and suggest generally good water quality. Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen or ammonia-nitrogen in the approximately 35 samples analyzed, for toxic metals in the 32 samples analyzed or for pesticides in the seven samples analyzed. One of the 36 samples, however, exceeded the Class B(WW) criterion for pH. The sample collected on June 1, 2004, contained a pH level of 10.4 pH units, thus greatly exceeding the water quality criterion of 9.0 pH units. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the percentage of violations for pH at this station (3%) does not suggest a water quality impairment (the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated). During the previous (2004) assessment period, one of the nine samples analyzed for pesticides and other toxic organic compounds contained a level of the pesticide 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. None of the 12 samples analyzed for this pesticide during the 2002-2004 assessment period violated the Class B(WW) criterion.
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 DNR/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 (air). 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 (13,720 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 were 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. The 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 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. 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 2003 RAFT follow-up sampling conducted in this assessment segment. Although results of previous fish contaminant monitoring show that this river segment has a history of somewhat elevated levels of chlordane in fish, the level of chlordane in the 2003 RAFT follow-up sample is well below the new advisory trigger level of 0.6 ppm. Also, the levels of the other contaminants do not exceed the new (2006) advisory trigger levels for mercury and PCBs, thus suggesting no justification for issuance of a consumption advisory.
