Assessment is based on: (1) results of ambient water quality monitoring at Wapello conducted from January 2010 to December 2012 as part of the USGS NAWQA program, (2) results of IDNR ambient monitoring at Wapello from October 2010 to June 2012, (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, 2008, and 2010 and (4) 2002, 2008 and 2012 IDNR/SHL biological sampling data.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed as “not supporting” (IR 5a) due to levels of indicator bacteria that slightly exceed state water quality criteria. The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" (IR 3b-u) based on results of biological monitoring. Ambient physical/chemical water quality monitoring from 2010-2012 suggests "full support" of the Class B(WW1) aquatic life uses. Fish consumption (Human-Health/fish) uses are assessed (evaluated) as "partially supported" (IR 3b) due to violations of Iowa’s human-health/fish criterion for dieldrin. Results of fish contaminant monitoring in 2005, 2006, 2007, 2008, and 2010, however, suggest low levels of common fish contaminants (mercury, PCBs, and chlordane). Sources of data for this assessment include (1) results of ambient water quality monitoring at Wapello (USGS station 05465500) conducted from January 2010 to December 2012 as part of the USGS NAWQA program, (2) results of IDNR ambient monitoring at Wapello from October 2010 to June 2012, (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, and 2008, (4) results of REMAP fish contaminant monitoring in 2006 and (5) 2002, 2008 and 2012 IDNR/SHL biological sampling data.
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supporting” due to levels of indicator bacteria that slightly exceed the Class A1 water quality criteria. The geometric means of indicator bacteria (E. coli) in the 27 samples collected during the recreational seasons of 2010 through 2012 at USGS station 05465500 at Wapello were as follows: the 2010 geometric mean was 136 orgs/100 ml, the 2011 geometric mean was 31 orgs/100 ml, and the 2012 geometric mean was 48 orgs/100 ml. Only the 2010 geometric mean—and then only very slightly—exceeded the Class A1 criterion of 126 orgs/100 ml. Six of the 27 samples (22%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. Bacteria monitoring at the IDNR ambient station at Wapello produced sufficient to calculate only one recreation season geometric mean: only two recreation season were collected in 2010, and only three samples were collected in the recreation season of 2012: these sample sizes do not meet the IDNR data quantity guidelines and are thus too small to calculate a meaningful geometric mean for comparison to the Class A1 criterion. The geometric mean of the eight monthly samples collected during the recreation season of 2011 was 52 orgs/100 ml which is far below the Class A1 criterion of 126 orgs/100 ml. Only one of the eight recreation season samples in 2011 (12%) exceeded the Class A1 single-sample maximum criterion. 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 (for 2010), these uses are assessed as “impaired.” Regardless of this impairment, levels of indicator bacteria in this segment of the Iowa River have historically been and continue to be low relative to levels in other stream/river segments in Iowa.
Regarding support of the Class B(WW1) uses, results of USGS/NAWQA monitoring and IDNR ambient monitoring from 2010 through 2012 suggest “full support” of these uses. Result of this monitoring showed no violations of Class B(WW1) water quality criteria for the following parameters: dissolved oxygen in the 60 USGS samples or the 21 IDNR samples; ammonia-nitrogen in the 52 USGS samples or the 21 IDNR samples; chloride in the 51 USGS samples or the 21 IDNR samples, or sulfate in the 51 USGS samples or the 21 IDNR samples. Violations of Class B(WW1) criteria for conventional parameters occurred in the following: one of 21 IDNR samples (5%) exceeded the temperature criterion of 32C; , two of 21 IDNR samples (10%) violated the criteria for pH; and four of 60 USGS samples (7%) violated the criteria for pH. These monitoring results do not suggest impairment of the Class B(WW1) aquatic life uses. According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as pH, dissolved oxygen, or temperature, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, however, the results from the USGS and IDNR monitoring stations in this river segment, however, do not indicate that significantly greater than 10% of the samples exceed the Class B(WW1) criteria for dissolved oxygen, pH, or temperature. Thus, the results of chemical/physical water quality monitoring from 2010 to 2012 in this segment suggest that the Class B(WW1) aquatic life uses should be assessed (monitored) as “fully supported.”
Results of this monitoring for toxics also suggest “full support” of the Class B(WW1) aquatic life uses. No violations of Class B(WW1) criteria occurred for the following parameters monitored by USGS: arsenic (52 samples), chlorpyrifos (50 samples), DDE (3 samples), dieldrin (50 samples) or selenium (42 samples). Similar to the results of monitoring for conventional parameters, results of monitoring for toxics suggest “full support” as none of the parameter exceed their respective criteria in more than one sample over the three year period (2010-2012).
However, the biological monitoring conducted in this segment suggests (evaluated) partial support of the aquatic life uses. This evaluated biological assessment was based on data collected in 2002, 2008 and 2012 as part of the IDNR/SHL 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 2008 BMIBI scores were 40 and 45 (both fair). The 2012 BMIBI score was 14 (poor). 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 1994-2008. 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 times in 2002 and passed the BMIBI BIC 0/3 times in the last five years. This assessment is considered evaluated because the drainage area (12490 and 12499 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.
The Human Health designated use (including the fish consumption use) remains assessed (evaluated) as “partially supporting” (IR Category 3b-potentially impaired) due to levels of dieldrin in water. For the previous (2012) IR cycle, none of the 44 samples collected from 2008-2010 at USGS station 05465500 contained detectable levels of dieldrin (detection level of 0.009 ug/l), two samples contained “estimated” levels of dieldrin (both samples were estimated to have 0.002 ug/l of dieldrin; these samples were collected on June 2, 2008 and June 25, 2009. These estimated values exceed the Iowa human health-fish (HH-fish) criterion of 0.00054 ppb. In addition, one of 50 samples analyzed by USGS for dieldrin from 2010-2012 exceeded this Class HH/fish criterion: the sample collected on June 6, 2011 contained 0.005 ug/l of dieldrin. According to IDNR’s assessment/listing methodology, if the average level of a toxic metal or pesticide is greater than its respective human health criterion, impairment ("nonsupport") of the Human Health use is indicated. However, the samples with detectable levels of dieldrin at this monitoring station are too few (three over five years of monitoring) and the method detection level (either 0.008 or 0.009 ug/l) is far too high (~16 times the HH criterion for dieldrin) to allow calculation of a meaningful summary statistic (i.e., mean) for dieldrin at this monitoring station.
Results of fish contaminant sampling in this river segment conducted in 2007 as part of the U.S. EPA/IDNR RAFT program showed 6 ppb of dieldrin in the composite sample of common carp fillets and 35 ppb in the composite sample of whole-fish common carp analyzed for the 2008 RAFT. Although Iowa does not have a consumption advisory trigger level for dieldrin, the levels seen in the 2007 fillet samples and the 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. Due to the low levels of dieldrin in fish tissue samples from this river segment, and due to the low frequency with which violations of the human health (fish + water) dieldrin criterion occurred (5%), this assessment is considered appropriate for Iowa’s IR Category 3b (potential impairment). IR Category 3b waters will be added to Iowa’s list of waters in need of further investigation.
Fish contaminant monitoring for toxic parameters other than dieldrin (e.g., mercury, PCBs, and chlordane) suggest “full support” of fish consumption uses. Fish consumption was conducted near Wapello in (1) 2005, 2006, 2007, 2008, and 2010 as part of the EPA/IDNR fish tissue (RAFT) program and (2) 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. Contaminant levels in the 2010 composite whole-fish sample of common carp had similar levels: mercury: 0.061 ppm; total PCBs: 0.111 ppm; and technical chlordane: 0.091 ppm. These results do not suggest the need for issuance of a consumption advisory.
Due, however, to the low frequency with which violations of the human health (fish + water) dieldrin criterion occurs, the assessment of the HH-fish consumption uses in this river segment is considered appropriate for Iowa’s IR Category 3b (potential impairment). IR Category 3b waters are added to Iowa’s list of waters in need of further investigation.