Assessment is based on: (1) results of ambient water quality monitoring at Wapello conducted from January 2006 to December 2008 as part of the USGS NAWQA program, (2) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, and 2008, (3) results of REMAP fish contaminant monitoring in 2006 and (4) 2002, 2003 and 2008 IDNR/UHL biological monitoring data.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain not assessed due to the lack of information on levels of indicator bacteria upon which to base an assessment. The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" based on results of 2002, 2003 and 2008 IDNR/UHL biological monitoring. However, the ambient physical/chemical water quality monitoring results from 2006-2008 suggest "monitored" full support of aquatic life uses. Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2005, 2006, 2007, and 2008. Sources of data for this assessment include (1) results of ambient water quality monitoring at Wapello (station 05465500) conducted from January 2006 to December 2008 as part of the USGS NAWQA program, (2) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, and 2008, (3) results of REMAP fish contaminant monitoring in 2006, and (4) 2002, 2003 and 2008 IDNR/UHL biological monitoring data.
EXPLANATION: The Class A1 (primary contact recreation) uses remain “not assessed” due to lack of data on indicator bacteria upon which to base an assessments. The monitoring conducted on the Iowa River at Wapello from 2006 through 2008 by USGS (station 05465500) did not include analysis for indicator bacteria. Thus, due to this lack of information, an assessment of support of the Class A1 uses could not be developed.
Regarding support of the Class B(WW1) uses, results of the USGS/NAWQA monitoring from January 2006 through December 2008 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen (40 samples) or ammonia-nitrogen (41 samples). One of 45 samples (2%) did violate the Class B(WW1)/A1 criterion for pH: the sample pH value (9.1 units) exceeded the Class B(WW1)/A1 criterion of 9.0 units. According to U.S. EPA assessment guidelines, however, if less than 10% of samples exceed state criteria for conventional parameters such as 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). Violations of pH in ambient waters tend to reflect high levels of primary productivity and do not typically reflect the addition of pollutants to surface waters.
Results of this monitoring also showed no violations of the Class B(WW1) chronic water quality criteria for DDE (26 samples analyzed) or dieldrin (41 samples analyzed). Note: the assessment of aquatic life uses developed for the 2000 report ("partially supported”) was based on two violations of the Class B(WW) chronic water quality criterion for dieldrin in the 52 samples collected between March 1996 and August 1998. Because no dieldrin was detected in the 34 samples collected between October 1998 and September 2001, this assessment was changed to "fully supported" for the 2002 report. USGS monitoring conducted from September 2001 through December 2008 has shown no levels of dieldrin above the Class B(WW1) chronic criterion (0.0556 ppb). Only one sample was analyzed for toxic metals during the 2006-2008 period; no violations of Class B(WW1) chronic criteria for metals occurred in this sample.
However, the biological monitoring conducted in this segment suggest (evaluated) partial support of the aquatic life uses. This evaluated biological assessment was based on data collected in 2002, 2003 and 2008 as part of the IDNR/UHL stream REMAP and large river benthic macroinvertebrate sampling projects. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological 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 2002 FIBI score was 40 (fair). The 2003 and 2008 BMIBI scores were 35, 40 and 45 (all fair). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 1/1 time in 2002 and passed the BMIBI BIC 0/3 times in the last six years. This assessment is considered evaluated because the drainage area (12490 and 12493 mi2) above the sampling sites is greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC and failed to meet the BMIBI BIC, 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.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”. This segment had multiple BMIBI samples collected in the previous 10 years (1999-2008); however, the samples were not collected during 2004-2008. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).
One of 41 samples from USGS station 05465500 analyzed for dieldrin during the 2006-2008 period exceeded the Iowa human health-fish (HH-fish) criterion of 0.00054 ppb. For purposes of Section 305(b) assessment, Iowa DNR views the Human Health criterion for dieldrin as analogous to a chronic criterion for a toxic parameter. Thus, impairment of the HH use by dieldrin would be suggested if significantly more than 10% of the samples violated this criterion. Because only 2% of the samples (1 of 41) violated this criterion, this violation does not indicate impairment of the HH-fish use. Results of recent fish contaminant sampling in this river segment conducted as part of the U.S. EPA/IDNR RAFT program showed 6 ppb of dieldrin in the composite sample of common carp fillets analyzed for the 2007 RAFT and 35 ppb in the composite sample of whole-fish common carp analyzed for the 2008 RAFT. Although Iowa does not have an advisory trigger level for dieldrin, the levels seen in the 2007 and 2008 whole-fish composite samples from Wapello are well below the Iowa’s previous advisory trigger of 300 ppb of dieldrin (i.e., the U.S. FDA action level for dieldrin). Levels of dieldrin in Iowa fish have declined significantly since the early and mid-1980s when levels of 300 ppb to 500 ppb were not uncommon.
Fish consumption uses are assessed (monitored) as "fully supported" based on fish contaminant monitoring near Wapello conducted (1) in 2005, 2006, 2007 and 2008 as part of the EPA/IDNR fish tissue (RAFT) program and (2) in 2006 as part of the IDNR REMAP project (Site 45). This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring. Due to a change in the design of the RAFT program, this site was sampled in the consecutive years of 2005 and 2006. The 2005 composite whole-fish samples of common carp had low levels of the primary contaminants: mercury: 0.111 ppm; total PCBs: 0.193 ppm; and technical chlordane: 0.051 ppm. The 2006 composite whole-fish samples of common carp had similar levels of these contaminants: mercury: 0.196 ppm; total PCBs: 0.223 ppm; and technical chlordane: 0.043 ppm. The 2008 composite whole-fish samples of common carp also had similar levels of these contaminants: mercury: 0.135 ppm; total PCBs: 0.217 ppm; and technical chlordane: 0.067 ppm.
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. Although assessed as “fully supported” for this reporting cycle, the level of at least one contaminant does, however, exceed one or more advisory trigger levels: the level of PCBs in the 2006 and 2008 samples of whole-fish common carp (0.223 ppm and 0.217, respectively) slightly exceed the one meal per week trigger level of 0.20 ppm. According to the IDNR/IDPH advisory protocol, these results neither warrant issuance of an advisory nor indicate 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. Fish contaminant monitoring conducted as part of the IDNR REMAP project in October 2006, however, suggests that levels of PCBs in the edible portion of common carp are well-below the advisory trigger level for PCBs. Results of this monitoring showed low levels of the primary contaminants in the samples of common carp fillets: mercury: 0.183 ppm; total PCBs: 0.1 ppm; and technical chlordane: <0.03 ppm. These results suggest that PCB levels in the edible portion of bottom feeding fish are below advisory trigger levels for PCBs as well as those for mercury and chlordane. In addition, RAFT monitoring conducted in 2007 showed low levels of the primary contaminants in the samples of common carp fillets: mercury: 0.12 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. In addition the level of mercury in the fillet sample of freshwater drum (0.098 ppm) was below the advisory trigger level. These results suggest that the fish consumption uses be assessed as "fully supported."