Assessment Comments

Assessment is based on: (1) results of IDNR/SHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) from 2010-2012, (2) results of monitoring conducted by the Long-Term Resource Monitoring Program at LTRMP station UI02.9M from 2006-08, (3) results of monitoring for indicator bacteria conducted at Upper Iowa River Watershed project Site 30 near New Albin from 2010-2012, (4) results of IDNR/SHL biological monitoring in 2005, 2008 and 2012, and (5) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2004, 2006, and 2010.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was designated for Class A1 (primary contact recreation) uses and B(WW) aquatic life uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.   EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment remains designated for both primary contact recreation uses (still termed Class A1) and for aquatic life uses (now termed Class B(WW1).   In addition, this assessment segment also remains designated for fish consumption uses (now termed Class HH (human health/fish consumption) uses).]

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to high levels of indicator bacteria that exceed state water quality criteria (IR 5a).   The Class B(WW1) aquatic life uses remain assessed (monitored) as "fully supported" (IR 2a).   Fish consumption uses remain assessed (monitored) as “partially supported” based on high levels of mercury in fish samples and based on the resultant issuance and continuance of a fish consumption advisory for this segment of the Upper Iowa River (IR 5a).   Sources of data for this assessment include (1) results of IDNR/SHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2010 through December 2012, (2) results of monitoring conducted by the Long-Term Resource Monitoring Program at LTRMP station UI02.9M from April 2007 through November 2008, (3) results of monitoring for indicator bacteria conducted at Upper Iowa River Watershed project Site 30 near New Albin (STORET No.   NEIARCD 190050008) from April 2010 through October 2012, (4) results of IDNR/SHL biological monitoring in 2005, 2008 and 2012, and (5) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2004, 2006 and 2010.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to levels of indicator bacteria (E coli) that exceed state water quality criteria.   Twenty-one samples were analyzed both at the IDNR/UHL ambient water quality monitoring station near Dorchester (STORET station 10030001) and at the Upper Iowa River Watershed Project site 30 near New Albin (STORET station 190050008).   Recreation season (March-November) geometric means based on the 24 samples from the IDNR ambient monitoring station near Dorchester very slightly exceeded Iowa’s Class A1 water quality criterion of 126 orgs/100 ml.   While the 2010 geometric mean was 263 orgs/100 ml and thus exceeded the Class A1 criterion, the 2011 geometric mean (57 orgs/100 ml) and the 2012 geometric mean (42 orgs/100 ml) were well below the Class A1 criterion.   Only three of the 24 samples (12%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   Thus, the bacteria data for this station from 2010-12 indicate that only the geometric mean from 2010 suggests impairment of the Class A1 uses.

Similarly, the geometric means of indicator bacteria (E.  coli) in the 20 samples collected during the recreational seasons of 2010 through 2012 at Upper Iowa River Watershed project Site 30 near New Albin also slightly exceeded the Iowa water quality criterion to protect primary contact recreation uses.   The 2010 recreation season geometric mean of seven samples was 259 orgs/100 ml, the 2011 geometric mean of six samples was 75 orgs/100 ml, and the 2012 geometric mean of seven samples was 91 orgs/100 ml.   Levels of E.  coli in five of the combined 20 samples (25%) exceeded Iowa’s 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 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).   Thus, the violations of the Class A1 geometric mean criterion in the recreation season of 2010 at both stations suggests that the Class A1 uses should be assessed as “impaired”.   Regardless, the 2010-2012 data suggest very low levels of indicator bacteria in this river segment.

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported."  Similar to the previous (2010 and 2012) assessment cycles, none of the 36 samples from the IDNR/UHL station analyzed from January 2010 through December 2012 for conventional pollutants and ammonia exceeded a state Class B(WW) criterion.   None of the 30 samples analyzed from LTRMP station UI02.9M from 2006-2008 violated Class B(WW1) criteria for ammonia, dissolved oxygen, or pH.   Monitoring from 2010 to 2012 at Upper Iowa River Watershed Site 30 included analysis for ammonia.   None of the 20 samples collected violated the ph/temperature-dependent aquatic life criteria for ammonia with ammonia levels 18 of the 20 samples being reported as less than the analytical level of detection (0.05 mg/l).   The samples with the two detected levels of ammonia (0.06 mg/l on July 6, 2010 and 0.09 mg/l on July 2, 2012) do not have the accompanying data for pH and water temperature needed to calculate the respective Class B(WW1) criterion; however, these detected levels are well below criteria based on typical water quality conditions.  These results suggest “full support” of the Class B(WW1) aquatic life uses.

Similarly, the Class B(WW1) aquatic life uses are assessed (evaluated) as “fully supporting" based on data collected in 2005, 2008 and 2012 as part of the IDNR/SHL stream biocriteria and REMAP projects.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria 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 REMAP FIBI scores were 57 (good) and 82 (excellent).   The 2008 BMIBI score was 82 (excellent).   The 2012 BMIBI scores were 70 and 72 (both good).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), 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 52 and the BMIBI BIC for this ecoregion is 61.   This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 3/3 times in the last eight years.   This assessment is considered evaluated because the drainage areas (768 and 897 mi2) above the sampling sites was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed both the FIBI and BMIBI BICs, 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.  

Fish consumption uses remain assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dorchester in 2004, 2006, and 2010.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   The composite samples of fillets from the 2004 samples of common carp and smallmouth bass had generally low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.228 ppm; total PCBs:  0.13 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.486 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   The levels of mercury in 2004 samples of both common carp and smallmouth bass exceed the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory:  the level of mercury in the sample of common carp fillets was 0.228 ppm and in the sample of smallmouth bass fillets was 0.486 ppm.  

The composite samples of fillets from the 2006 RAFT samples of golden redhorse (Moxostoma erythrurum) and smallmouth bass had similarly high levels of mercury.   The level of mercury in the composite sample of golden redhorse fillets was 0.362 ppm, and the level of mercury in the composite sample of smallmouth bass fillets was 0.37 ppm.   According to the IDNR/IDPH advisory protocol, if two consecutive samplings show that contaminant levels are above an advisory trigger level in fillet samples, a consumption advisory will be issued.   Because levels of mercury in both the 2004 and 2006 samples of smallmouth bass exceed the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory, a consumption advisory was issued for this segment by IDNR in March 2008.   Because level of mercury in the sample of the bottom-feeding golden redhorse was also greater than the advisory level, all species were included in the one-meal/week advisory.   The existence of a one-meal/week consumption advisory for this assessment segment suggests that the fish consumption uses are “partially supported.”  This advisory extends from the Lower Dam in eastern Winneshiek County upriver to County Road W20 approximately 5.5 miles upriver from Decorah.   Follow-up sampling was conducted at the Upper Iowa River near Dorchester in 2010.   The level of mercury in samples of golden redhorse fillets (0.318 ppm) and smallmouth bass fillets (0.392 ppm) were both above the advisory trigger level therefore suggesting that the fish consumption advisory should remain at this river segment.