Assessment is based on: (1) results of ambient water quality monitoring at Wapello conducted from February 2008 to December 2010 as part of the USGS NAWQA program, (2) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, 2008, and 2010, (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 are assessed as “not supporting” (IR Category 5a) due to levels of indicator bacteria that exceed state water quality criteria. This is a new impairment for this assessment segment. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient physical/chemical water quality monitoring from 2008-2010. Fish consumption (Human-Health/fish) uses are assessed (evaluated) as "partially supported" (IR Category 3b) due to violations of Iowa’s human-health/fish criterion for dieldrin. Results of fish contaminant monitoring in 2005, 2006, 2007, and 2008, 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 February 2008 to December 2010 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. Note: IDNR ambient monitoring was conducted in this segment from October to December 2010; this monitoring generated too few data (three samples) upon which to base assessments for the 2012 IR cycle.
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supporting” due to levels of indicator bacteria that exceed the Class A1 water quality criteria. The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2008 through 2010 at USGS station 05465500 at Wapello were as follows: the 2008 geometric mean was 200 orgs/100 ml, the 2009 geometric mean was 256 orgs/100 ml and the 2010 geometric mean was 136 orgs/100 ml. All three geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml. Eight of the 21 samples (38%) 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.” 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 the USGS/NAWQA monitoring from February 2008 through December 2010 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen (53 samples). for ammonia-nitrogen (44 samples), or for pH (85 samples). Results of this monitoring also showed no violations of the Class B(WW1) chronic water quality criteria for DDE (17 samples analyzed) or dieldrin (41 samples analyzed). No violations of Class B(WW1) chronic criteria occurred for the following parameters: arsenic (44 samples), chloride (48 samples), chlorpyrifos (44 samples), selenium (27 samples), or sulfate (27 samples).
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, 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 over a five-year period 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 a five-year period. 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).
The Human Health designated use (including the fish consumption use) is assessed (evaluated) as “partially supporting” (IR Category 3b-potentially impaired) due to levels of dieldrin in water. Although 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. 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 were too few (two) and the method detection level (0.009 ug/l) was 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 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 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 and 2008 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.
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 (not whole-fish) 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."
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 will be added to Iowa’s list of waters in need of further investigation.