Assessment Comments

Assessment is based on results of (1) IDNR/UHL monthly ambient monitoring conducted during the 2006-2008 assessment period at the County Road J-53 bridge near Shambaugh (STORET station 10730001 (formerly station 787044)), (2) IDNR/UHL stream REMAP biological sampling in 2006, and (3) fish tissue (RAFT) monitoring in 2007.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this river segment was designated for Class B(WW) aquatic life uses, including fish consumption uses and for Class C (drinking water) 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 is also now presumptively designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), for fish consumption uses (now termed Class HH (human health/fish consumption uses), and for Class C (drinking water) uses.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria (E.   coli).   The results of the water quality sampling indicate that the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported"; however, the 2006 biological sampling data indicate the Class B(WW1) aquatic life uses should be assessed (evaluated) as "partially supporting."  The Class C (drinking water) uses are also assessed (monitored) as "fully supported.”  Fish consumption uses are assessed (monitored) as “fully supported” based on fish contaminant monitoring in 2007.   This assessment is based on (1) results IDNR/UHL monthly ambient monitoring conducted during the 2006-2008 assessment period at the County Road J-53 bridge near Shambaugh (STORET station 10730001 (formerly station 787044)), (2) IDNR/UHL stream REMAP biological monitoring in 2006, and (3) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2007 south of Shambaugh.  

EXPLANATION:  The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of ambient monitoring for indicator bacteria (E.   coli).   The geometric mean level of indicator bacteria (E.   coli) in the 21 samples collected at the IDNR/UHL ambient monitoring station near Shambaugh during summer recreational seasons of 2006-2008 (829 orgs/100ml) far exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Seventeen of the 21 samples (81%) exceed Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level 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).   Note:  The February 2010 version of the Iowa surface water classification shows at least portions of this river segment designated for Class A2 (secondary contact recreation) uses.   This state-level designation, however, has not yet been approved by U.S.  EPA.   The geometric mean of the 32 E.  coli samples collected during calendar years 2006-2006 in this river segment (497 orgs/100 ml) would meet Iowa’s Class A2 geometric mean criterion of 630 orgs/100 ml, thus indicating “full support” of the Class A2 uses.  

Regarding support of the Class B(WW1) aquatic life uses, results of ambient monitoring at the IDNR/UHL station near Shambaugh showed no violations of Class B(WW1) water quality criteria during the 2006-2008 assessment period for dissolved oxygen (minimum value = 7.8 mg/l), pH (range:  7.2-8.9 units), or ammonia-nitrogen (maximum value = 1.2 mg/l) in the 32 samples collected.   Levels of pesticides in the 11 samples collected and levels of toxic metals in two analyzed were all below the respective Class B(WW1) criteria.   These results suggest "full support" of the Class B(WW1) aquatic life uses.  

However, the 2006 biological sampling suggest that the Class B(WW1) aquatic life uses should be assessed (evaluated) as “partially supported.”  This evaluated biological assessment was based on data collected in 2006 as part of the DNR/UHL stream REMAP project.   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 2006 FIBI score was 34 (fair) and the BMIBI score was 25 (poor).   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 36 and the BMIBI BIC for this ecoregion is 51.   This assessment is considered evaluated because the drainage area (779 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 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.  

The Class C (drinking water) uses are also assessed (monitored) as "fully supported."  Levels of atrazine exceeded the Class C criterion of 3 ppb (=EPA’s MCL) in one of the 11 samples (9%) analyzed (maximum value = 13 ppb).   The mean (1.3 ppb) and median (0.07 ppb) values of atrazine during the 2006-2008 period, however, are well-below the Class C criterion.   Also, the level of nitrate exceeded the Class C criterion of 10 mg/l (=EPA’s MCL) in one of 32 samples (3%) analyzed (maximum value = 11 ppm).   The mean (4.4 ppm) and median (4.2 ppm) values of nitrate during the 2006-2008 period, however, are well-below the Class C criterion, and the percentage of violations (3%) is below the IDNR impairment trigger level of a 10% violation frequency.   According to IDNR guidelines for Section 305(b) assessments, these results do not suggest an impairment of drinking water uses for this assessment segment.  

Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring at the Nodaway River south of Shambaugh in 2007.   The composite samples of fillets from channel catfish had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.087 ppm; total PCBs: <0.09 ppm; and technical chlordane: 0.068 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.   The fish contaminant data generated from the 2007 RAFT sampling conducted at this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.