Assessment Comments
This assessment is based on results of (1) IDNR/UHL monthly monitoring from 2000-04 at the Highway 30 bridge downstream from Cedar Rapids and (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 1996.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria that violate state water quality criteria. The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported” based on results of ambient chemical/physical water quality monitoring. Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of fish contaminant monitoring in 1996. The sources of data for this assessment include (1) the results of monthly monitoring from January 2002 through December 2004 at the IDNR ambient city monitoring station located at the Highway 30 bridge downstream from Cedar Rapids (station 10570001) and (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 1996. This assessment is the same as that developed for the adjacent downriver segment of the Cedar River (IA 02-CED-0020-3).
EXPLANATION: The Class A uses were assessed as "not supported" based on results of ambient monitoring for 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 39 samples collected (172 orgs/100ml) is slightly above the Iowa Class A water quality criterion of 126 orgs/100ml. However, 13 of the 39 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). In addition, if more than 10% of the samples exceed the single-sample maximum value of 235 orgs/100 ml, the primary contact recreation uses are "partially supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). 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 also suggesting impairment of the Class A uses. Thus, both the geometric mean of E. coli (172 orgs/100ml) and the percentage of samples that exceed the single-sample maximum value of 235 orgs/100 ml (33%) suggest impairment of the Class A (primary contact recreation) uses of this river segment.
The Class B(WW) aquatic life uses were assessed as "fully supported " based on results of monitoring from the IDNR ambient at Highway 30 from 2002 through 2004. Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen or ammonia-nitrogen in the approximately 36 samples collected or for toxic organic compounds (including pesticides) in the 32 samples analyzed during this assessment period. Of the 32 samples analyzed for toxic metals, however, one sample violated a Class B(WW) criterion: the sample collected on March 5, 2003 exceeded the Class B(WW) criterion for copper of 35 ug/l; the level of copper in the sample was 40 ug/l. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-18), however, one violation of a water quality criterion for a toxic pollutant in an abundant data set (at least 10 samples over at three-year period) does not indicate an impairment of aquatic life uses.
Levels of pH violated the Class B(WW) criteria of either 9.0 pH units and 6.5 pH units in three of the 36 samples collected (7%). According to U.S. EPA assessment guidelines, if less than 10% of samples exceed state criteria for pH, the primary contact (Class A) and aquatic life (Class B) uses should be assessed as "fully supported" (see pgs 3-17 of U.S. EPA 1997b). In addition, violations of the high pH criterion tend to be more related to natural conditions (high levels of primary productivity) than to pollution; thus, the occurrence of these high levels of pH in this river segment is not seen as a water quality impairment. The low pH violation on January 7, 2002, occurred on the same day as the maximum ammonia level (1.3 mg/l) for the 2002-2004 period; this pH violation is likely not related to high primary productivity.
Fish consumption uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Rapids in 1996. Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). 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 impairment of the fish consumption uses. This scenario does not apply to the fish contaminant data generated from the 1996 RAFT sampling in this assessment segment.
The composite samples of fillets from channel catfish and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.259 ppm; total PCBs: 0.143 ppm; and technical chlordane: 0.034 ppm. Levels of primary contaminants in the composite sample of freshwater drum fillets were as follows: mercury: 0.085 ppm; total PCBs: 0.164 ppm; and technical chlordane: 0.032 ppm. Although assessed as “fully supported” for this reporting cycle, the levels of at least one contaminant does, however, now exceed one or more advisory trigger levels: the level of mercury in the sample of channel catfish fillets (0.259 ppm) exceeds the one meal per week trigger level of 0.20 ppm. According to the IDNR/IDPH advisory protocol, this single result from the 1996 sampling on the Cedar River neither warrants issuance of an advisory nor indicates impairment of fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. But, this elevated level does indicate the need to conduct additional monitoring to better define contaminant levels in fish from this river segment. Thus, follow-up monitoring will be conducted in 2006 to better determine (1) levels of mercury in the edible portions (fillets) of fish in this river segment and (2) whether a one-meal-per-week consumption advisory needs to be issued.
