Wapsipinicon River IA 01-WPS-340

The Class A1 uses are assessed (monitored) as "partially supported" based on violations of state criteria for indicator bacteria (E. coli).  Results of IDNR bacteria monitoring conducted near Stone City as part of the city/county beach program during recreational seasons of 2012 and 2013 suggest slightly elevated levels of E. coli in this river segment.  The geometric means of indicator bacteria (E. coli) in the 16 samples collected during the recreational seasons of 2012 and 2013 were as follows:  the 2012 geometric mean was 127 orgs/100 ml, and the 2013 geometric mean was 99 orgs/100 ml.  The 2013 geometric mean was below (met) the Class A1 criterion of 126 orgs/100 ml; the 2012 geometric mean was just slightly above the Class A1 criterion.  Four of the 16 samples (25%) exceeded the Class A1 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 a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as Section 303(d)-impaired.  Despite this slight impairment, levels of bacteria during the recreational seasons of 2012 and 2013 were exceptionally low in this segment of the Wapsipinicon River. 

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supported” based on biological data collected in 2006 as part of the IDNR/SHL stream REMAP project and fish data collected in 2003 by IDNR Fisheries bureau.  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 65 (good) and the BMIBI score was 48 (fair).  The IDNR Fisheries Bureau 2003 FIBI score was 50 (fair).  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 1994-2008.  The non-riffle habitat FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52.  This assessment is considered evaluated because the drainage areas (1306 and 1263 mi2) above these sampling sites are 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 BIC and BMIBI BICs (using the UAV of 8 points), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment don't fall in the calibrated watershed size.

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Central City in 2006.  The composite sample of fillets from channel catfish had low levels of contaminants.  Levels of primary contaminants were as follows: mercury: 0.263 ppm; total PCBs: 0.09 ppm; and technical chlordane: < 0.03 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 levels of contaminants in the sample analyzed for the 2006 RAFT program do not exceed any of Iowa’s consumption advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.