Assessment Comments

Assessment is based on results of (1) results monthly water quality monitoring from 2008 through 2010 at the IDNR ambient station (STORET station 10220001) located at the County Road C43 bridge south of Garber, (2) results of water quality monitoring conducted at Garber by USGS from 2008 to 2010, (3) results of LTRMP monitoring at station TK04.8M from 2002 through 2004, (4) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2007 and 2008 near Garber, and (5) biological monitoring conducted in 2002 by the IDNR Fisheries Bureau and in 2003 by IDNR/UHL for the Iowa REMAP project.

Basis for Assessment

Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008, this segment is also now designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and 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 levels of indicator bacteria that exceeded state water quality criteria.   The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" based on results of biological monitoring conducted by the IDNR Fisheries Bureau in 2002 and by IDNR/UHL in 2003.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2007 and 2008.   Sources of data for this assessment include (1) results monthly water quality monitoring from January 2008 through December 2010 at the IDNR ambient station (STORET station 10220001) located at the County Road C43 bridge south of Garber approximately 1 mile downstream from confluence with the Volga River, (2) results of water quality monitoring conducted at Garber by USGS from February 2008 to December 2010, (3) results of routine water quality monitoring conducted at station TK04.8M from 2002 through 2004 by IDNR staff of the Upper Mississippi River Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA, (4) results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 2007 and 2008 near Garber, and (5) biological monitoring conducted in 2002 by the IDNR Fisheries Bureau and in 2003 conducted by IDNR/UHL for the Iowa REMAP project.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.   The geometric mean of indicator bacteria (E.  coli) in the 21 monthly samples collected during the recreational seasons of 2008 through 2010 at the IDNR ambient monitoring station near Garber exceeded the Iowa water quality criterion to protect primary contact recreation uses.   Recreation season (March-November) geometric means based on the these 21 monthly samples were above Iowa’s Class A1 water quality criterion of 126 orgs/100 ml:  the 2008 geometric mean was 1,347 orgs/100 ml, the 2009 geometric mean was 209 orgs/100 ml and the 2010 geometric mean as 309 orgs/100 ml.   Eleven of the 21 samples (52%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   Results of USGS monitoring in 2009 and 2010 at the Garber monitoring station also showed that recreation season (March-November) geometric means based on the 14 samples collected over two years were above Iowa’s Class A1 water quality criterion of 126 orgs/100 ml:  the 2009 geometric mean was 380 orgs/100 ml and the 2010 geometric mean as 247 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).  

The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of ambient monthly monitoring from (1) the IDNR/UHL ambient station south of Garber from 2008 through 2010 (2) the USGS station near Garber from 2008 through 2010, and (3) from the LTRMP station near the mouth of the Turkey River in 2002-04.   In addition, the results of IDNR biological monitoring in 2002 and 2003 also suggest “full support” of the Class B(WW) uses.  

Monitoring at the IDNR, USGS, and LTRMP stations showed no violations of Class B(WW1) water quality criteria for conventional pollutants or ammonia in the approximately 30 samples analyzed at the IDNR station, the 30 samples analyzed at the USGS station, and in the 43 samples analyzed at the LTRMP station.   In addition, none of the 30 samples analyzed for banned pesticides (e.g., DDT, and dieldrin) by USGS violated the respective Class B(WW1) criteria.  

Results of biological monitoring conducted by the IDNR Fisheries Bureau in 2002 and by IDNR/UHL in 2003 suggest that the Class B(WW1) aquatic life uses should be assessed (evaluated) as “partially supported”.   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 2003 REMAP FIBI score was 75 (excellent) and the BMIBI score was 53 (fair).   The 2002 Fisheries FIBI was 39 (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 1994-2004.   The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.   This biological assessment is considered “evaluated” because the drainage area (1553 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 the one out of two samples failed to meet the FIBI BIC and the 2003 sample passed 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 potential impairment is not appropriate for Iowa’s Section 303(d) list of impaired waters (Integrated Report Category 5) but is appropriate for IR Category 3b of Iowa’s Integrated Report and Iowa’s list of waters in need of further investigation.  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Garber in 2007 and 2008.   The composite samples of fillets from channel catfish and smallmouth bass in 2007 had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: chlordane: <0.03 ppm; total PCBs: 0.09 ppm; mercury: 0.09 ppm.   The level of mercury in the composite sample of smallmouth bass fillets was 0.514 ppm.   The level of mercury in the sample of smallmouth bass is above the IDPH/IDNR advisory trigger level (0.30 ppm).   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.   According to IDNR's methodology two consecutive samples with levels above the advisory trigger level are necessary to issue a fish consumption advisory.   Follow-up sampling was conducted in 2008 to better determine the levels of mercury in smallmouth bass and determine whether an advisory is justified for this river segment.   The 2008 sampling showed the level of mercury in the composite sample of smallmouth bass fillets (0.269 ppm) was below the advisory trigger level.   Therefore an advisory at this river segment is not justified and the fish consumption uses remain assessed (monitored) as "fully supported."