Iowa River IA 02-IOW-628

[Note: A TMDL for indicator bacteria in this segment of Iowa River was prepared and approved by EPA in June 2007. The approval of this TMDL moves the bacterial impairment for this segment from Iowa's list of Section 303(d) waters (Category 5a of the Integrated Report) to IR Category 4a (impaired; TMDL not required).]

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at the ACOE long-term station near the University of Iowa water treatment plant were as follows: the 2014 geometric mean was 0 orgs/100 ml, the 2015 geometric mean was 91 orgs/100 ml, and the 2016 geometric mean was 93 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Five of the combined 24 samples (21%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Also, if significantly more than 10% of the samples exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A1 uses should be assessed as "partially supported." This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35 of U.S. EPA 1997b).All geometric means for the recreation seasons of 2014-2016 at the ACOE long-term station near the University of Iowa water treatment plant are below the geometric mean criterion. The percentage of violations of Iowa’s single-sample maximum criterion for E. coli (235 orgs/100 ml), however, is significantly greater than 10%. Thus, the primary contact recreation uses are assessed as "partially supported."

The Class B(WW1) aquatic life were assessed (evaluated) as "partially supported" for the 2010 Integrated Reporting cycle due to fish kill investigations on April 13, 2006 and March 17, 2007. Both kills involved only gizzard shad and were attributed to natural causes (temperature fluctuation). Waters affected by such kills are appropriate for Category 3b of Iowa's Integrated Report, and this potential impairment was added to Iowa's 2012 list of waters in need of further investigation.According to Iowa DNR’s assessment/listing methodology, any IR 2b or 3b fish kills that occurred more than 10 years ago will be moved to IR Category 3a (not assessed). Therefore the current 3b assessment for the 2006 and 2007 fishkills is move to 3a (not assessed) for the current (2018) IR cycle.

Despite the occurrence of these fish kills, the remainder of the various types of water quality monitoring conducted in this river segment suggest good chemical water quality and "full support" of the Class B(WW1) (aquatic life) uses.Monitoringat the ACOE long-term station near the University of Iowa water treatmentshowed no violations of Class B(WW1) water quality criteria for 65 Dissolved Oxygen samples (minimum = 7 mg/L), 66 pH samples (range = 7.5 to 8.8), 66 Temperature samples (maximum = 28.5°C), 9 Chloride samples (maximum = 40.9 mg/L), or 9 Sulfate samples (maximum = 53.6 mg/L) occurred during monitoring from January 2014 to December 2016. 1 of the 58 samples (2%) analyzed for Ammonia (maximum = 17 mg/L) violated the Class B(WW1) criteria during the 2014-2016 monitoring period.Monitoringat DNR ambient station 10520002 upstream from Iowa Cityshowedno violations of Class B(WW1) water quality criteria for 9 Ammonia samples (maximum = 1.7 mg/L), 9 pH samples (range = 7.1 to 8.3), 9 Temperature samples (maximum = 26.3°C), 9 Chloride samples (maximum = 33 mg/L), or 9 Sulfate samples (maximum = 56 mg/L) occurred during monitoring from January 2014 to September 2014.1 of the 9 samples (11%) analyzed for Dissolved Oxygen (minimum = 3.5 mg/L) violated the Class B(WW1) criteria during the 2014-2014 monitoring period.According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17) and Iowa DNR's assessment/listing methodology, a violation frequency of significantly greater than 10% for conventional parameters such as Ammonia suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

More recent monitoring, however, suggested improvement in the status of the mussel community in this segment of the Iowa River, thus suggesting that the impairment based on the 1998-99 survey should be removed. The rationale for this assessment is as follows.

As part of a study to reintroduce the endangered Higgins eye mussel into the Iowa, Cedar, and Wapsipinicon rivers in eastern Iowa, a four-day mussel search was conducted in August 2004. This survey was coordinated by staff of the DNR Fisheries Bureau from the Guttenberg and Solon fish management stations. The purpose of the survey was to search for transformed Higgins eye mussels growing in the substrate. In addition to staff from the Guttenberg and Solon stations, staff from DNR Fisheries offices in Bellevue, Rathbun, and Manchester also assisted in the effort. Also, volunteers, county conservation boards and three divers from the U.S. Fish and Wildlife Service assisted in the effort. The following is an excerpt from a summary of this study:

“In total, 54 river stretches were searched by diving, wading, sieving and basket trawling. Nearly 2,400 mussels were collected of 27 species from the three rivers. Particularly impressive was the apparent rebound of the mussel community in the Iowa River at Iowa City. In that reach, 24 species of mussels were collected including some of Iowa's rarer species, the yellow sandshell (Lampsilis teres) and the buckhorn (Tritogonia verrucosa). This may be the last substantial pistolgrip population left in the state of Iowa.”

Results of the August 2004 survey suggest improved richness of mussel species that likely exceeds that found during the 1984 survey. Thus, based on this information, the mussel-related impairment of the aquatic life uses of this segment of the Iowa River was removed from the 2006 reporting/listing cycle.

Somewhat contradictory to the WQ sampling and mussel results, the fish and benthic macroinvertebrate results generated as part of DNR/SHL sampling from this segment suggest (evaluated) "partial support" of aquatic life uses. However, because this segment is almost completely impounded by the lowhead dam at Burlington Street in Iowa City, and because the drainage areas above the sampling sites are much higher than the DNR wadeable IBI calibration, the 2016 aquatic life assessment for this segment will rely on the WQ and mussel data, and this biological data and following biological assessment will be considered strictly supplemental.

Based on results of the DNR/SHL 2005 REMAP and TMDL biological samplings and on 2012-2014 stream nutrient sampling, the Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supporting." 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 2005 FIBI scores (n=7) ranged from 6 to 22 (all poor). THe 2012 BMIBI score was 11 (poor), the 2013 BMIBI score was 20 (poor) and the 2014 BMIBI score was 38 (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 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 0/7 times in 2005 and passed the BMIBI BIC 0/3 times in the last five years. This assessment is considered evaluated because the drainage area (average = 3182 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site failed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessmentdon’t fall in the calibrated watershed size. Thus, this assessment is considered of lower confidence (evaluated) and is not appropriate for addition of a water to the state's Section 303(d) list. According to DNR’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). DNR 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).

Results of Class C(drinking water) monitoring at the ACOE long-term station near the University of Iowa water treatment plant suggest “full support” of the drinking water uses. Monitoring showedno violations of Class C (drinking water) criteria for 9 Chloride samples (maximum = 40.9 mg/L and average = 20.7 mg/L) occurred during monitoring from January 2014 to November 2016.3 of the 58 samples (5%) analyzed for nitrate+nitrite (maximum = 14.3 mg/L and average = 6.5 mg/L) violated the Class C (drinking water) criteria during the 2014-2016 monitoring period.Monitoringat DNR ambient station 10520002 upstream from Iowa Cityshowedno violations of Class C (drinking water) criteria for 9 Chloride samples (maximum = 33 mg/L and average = 21.3 mg/L), 14 Alachlor samples (maximum = 0.05 ug/L and average = 0.0312 ug/L), 7 Atrazine samples (maximum = 1.8 ug/L and average = 0.4643 ug/L), 7 Carbofuran samples (maximum = 0.05 ug/L and average = 0.05 ug/L), or 7 Cyanazine samples (maximum = 0.05 ug/L and average = 0.05 ug/L) occurred during monitoring from January 2014 to September 2014.1 of the 9 samples (11%) analyzed for nitrate+nitrite (maximum = 14 mg/L and average = 4.2 mg/L) violated the Class C (drinking water) criteria during the 2014-2014 monitoring period.Thus, results from both these routine ambient monitoring stations suggest “full support” of the Class C drinking water uses.

Fish consumption uses remain assessed (monitored) as "fully supporting." The results from the UI/ACOE fish contaminant monitoring in 2012 show that levels of organochlorine contaminant are very low. Samples were collected on the Iowa River downriver from Coralville Dam in Iowa City. The samples of common carp from this segment of the Iowa River had low levels of chlordane measured as the sum of cis-chlordane, trans-chlordane, cis-nonachlor, trans-nonachlor, and oxychlordane. The levels of mercury and PCBs in the UI/ACOE fish samples were also well below Iowa’s fish consumption advisory thresholds.

Results from the U.S. EPA/DNR RAFT program also suggest “full support” of the fish consumption uses in this river segment. The results from RAFT monitoring at Iowa City in 2006 show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite sample of common carp fillets: mercury: 0.195 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.021 ppm.

Similarly, results from the 2006 REMAP fish contaminant monitoring showed low levels of the primary contaminants in the composite sample of common carp fillets: mercury: 0.181 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Results of DNR follow-up fish tissue sampling in 2015 showed that levels of mercury in tissue plug samples from five White Bass were all below the level of detection (0.05 mg/kg or ppm) and levels of contaminants in thecomposite sample of common carp fillets were also low: mercury: 0.09 ppm; total PCBs: <0.06 ppm; and technical chlordane: <0.02 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. The levels of contaminants in fish from this segment of the Iowa River do not exceed any of Iowa’s advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.