Assessment Comments

Assessment is based on results of: 1) IDNR ambient monthly monitoring near Hurstville (Maquoketa) (station 10490001; formerly station 290120) from January 2004 through December 2006 and 2) IDNR/UHL stream REMAP biological monitoring in 2006.

Basis for Assessment

[Note:  Prior to the current (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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), and due to the completion of a Use Attainability Analysis, 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 were 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 (monitored) as "fully supporting."  The fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river reach.   This assessment is based on results of IDNR ambient monthly monitoring near Hurstville (Maquoketa) (station 10490001; formerly station 290120) from January 2004 through December 2006 and IDNR/UHL stream REMAP biological monitoring in 2006.    

EXPLANATION:  The Class A1 (primary contact recreation) uses were assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.   The Class A1 use designation was added to this river segment by the state of Iowa in March 2006; this change in use classification was approved by U.S.  EPA in February 2008.  

The geometric mean of indicator bacteria (E.  coli) in the 24 samples collected during the recreational seasons of 2004 through 2006 at the IDNR ambient monitoring station near Hurstville exceeded the Iowa water quality criterion to protect primary contact recreation uses.   Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A1 criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, this exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.  

The geometric mean of E.  coli bacteria in the 24 samples from the IDNR ambient monitoring station near Hurstville was 828 orgs/100 ml, thus far exceeding Iowa’s geometric mean criterion of 126 orgs/100 ml; 15 samples (62%) 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 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 are assessed as “fully supporting” based on results of IDNR/UHL chemical/physical monitoring at the IDNR/UHL ambient monitoring station near Hurstville.   Results of this monthly ambient water quality monitoring show no violations of Class B(WW1) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the approximately 36 samples analyzed for conventional pollutants or in the approximately 10 samples analyzed for toxic metals and pesticides during the 2004-2006 period.   These results suggest "full support" of the Class B(WW1) aquatic life uses.  

The Class B(WW1) aquatic life uses are also assessed as “fully supporting” based on the  2006 biological monitoring but the confidence is lower in this assessment; thus, it is considered evaluated.   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 61 (good) and the 2006 BMIBI scores were 54 (fair) and 58 (good) (BMIBI average = 56).  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 36 and the BMIBI BIC for this ecoregion is 51.   This assessment is considered evaluated because the drainage area (563 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 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.

The fish consumption uses are "not assessed" due to lack of fish contaminant monitoring in this river reach.