Assessment Comments

Assessment is based on: (1) results of IDNR/UHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2006 through August 2008, (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 April 2004 through October 2006, (4) results of IDNR/UHL biological monitoring in 2005 and 2008, and (5) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2004 and 2006.

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 “not supported” due to high levels of indicator bacteria that exceed state water quality criteria.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported".   Fish consumption uses are assessed (monitored) as "partially supported based on issuance of a fish consumption advisory for this segment of the Upper Iowa River in 2008.   Sources of data for this assessment include (1) results of IDNR/UHL ambient monthly water quality monitoring conducted on the Upper Iowa River near Dorchester (station 10030001) during the period January 2006 through August 2008, (2) results of monitoring conducted by the Long-Term Resource Monitoring Program at LTRMP station UI02.9M from 2006 through 2008, (3) results of monitoring for indicator bacteria conducted at Upper Iowa River Watershed project Site 30 near New Albin (STORET No.  190050008) from April 2004 through October 2006, (4) results of IDNR/UHL biological monitoring in 2002, 2005 and 2008, and (5) results of U.S.   EPA/IDNR fish contaminant (RAFT) monitoring in 2004 and 2006.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not 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 and at eh Upper Iowa River Watershed Project site 30 near New Albin.   The geometric mean of E.   coli bacteria in the 21 samples analyzed at the IDNR/UHL ambient monitoring station near Dorchester was 144 orgs/100 ml; this geometric mean slightly exceeds the Iowa water quality standard of 126 orgs/100 ml.   These results are consistent with results of previous monitoring that show generally low levels of indicator bacteria in this river segment.   Six of the 21 samples (29%) 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 the geometric mean of E.   coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S.   EPA 1997b).  

Results from the UIRW monitoring station near New Albin also suggest slight impairment of the Class A1 uses.   The geometric mean level of indicator bacteria (E.   coli) in the 21 samples collected during the recreational seasons of 2004 through 2006 (153 orgs/100ml) at UIRW project Site 30 near New Albin also exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Seven of the 21 samples (33%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   Thus, monitoring results both the IDNR and UIRW stations show geometric means for E.  coli slightly above Iowa’s geometric mean criterion of 126 orgs/100 ml and thus suggest nonsupport of the Class A1 uses.     Note:  LTRMP monitoring does not include analysis for indicator bacteria.  

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported."  Similar to the previous (2008) assessment cycle, none of the approximately 32 samples from the IDNR/UHL station analyzed for conventional pollutants and ammonia, and neither of the two samples analyzed for pesticides and toxic metals 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.  

This evaluated biological assessment was based on data collected in 2005 and 2008 as part of the IDNR/UHL 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 2005 REMAP BMIBI scores were 87 (excellent) and 76 (excellent).   The 2008 BMIBI score was 82 (excellent).   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 1994-2004.   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 five 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 are assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dorchester in 2004 and 2006.   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 new advisory extends downriver the existing advisory issued in 2006 for the Upper Iowa River from the Lower Dam in eastern Winneshiek County upriver to County Road W20 approximately 5.5 miles upriver from Decorah.