Assessment Comments

Assessment is based on results of: 1) IDNR ambient monthly monitoring near Hurstville (Maquoketa) (station 10490001; formerly station 290120) from January 2008 through December 2010 and 2) 2006 IDNR/SHL stream biological monitoring data.

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, 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) are assessed (monitored) as "not supported" due to levels of indicator bacteria that exceed 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 2008 through December 2010 and on results of IDNR/SHL stream REMAP biological monitoring in 2006.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceed 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 Class A1 (primary contact recreation) uses are assessed as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria.   Results of IDNR monitoring from 2008 through 2010 showed that recreation season (March-November) geometric means based on the seven samples collected per year were well above Iowa’s Class A1 water quality criterion of 126 orgs/100 ml:  The annual recreation season geometric means for 2008, 2009 and 2010 are as follow:  2,391, 637, and 2,676 E.  coli orgs/100 ml.  respectively.   These geometric means far exceed the Class A1 criterion of 126 E.  coli orgs/100 ml.   Nineteen of the 21 samples (90%) exceeded Iowa’s single sample maximum criterion of 235 E.  coli 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 as “fully supporting” based on results of IDNR/SHL 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 29 samples analyzed for conventional pollutants during the 2008-2010 period.   These results suggest "full support" of the Class B(WW1) aquatic life uses.  

The Class B(WW1) aquatic life uses also remain assessed (evaluated) as “fully supporting” based on biological monitoring in 2006.   This biological assessment was based on data collected in 2006 as part of the IDNR/SHL 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).   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 segment passed the FIBI BIC 1/1 times and passed the BMIBI BIC 2/2 times in the last five years.   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.  

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.   This segment had multiple BMIBI samples collected in the previous five years; however, the samples were not collected in multiple years.   Despite this change in assessment methodology and type, this waterbody remains in IR Category 5a due to the primary contact impairment.  

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