Assessment Comments
Assessment is based on results of monitoring for indicator bacteria conducted at Site 22 of the Upper Iowa River Watershed (UIRW) project from April 2008 through October 2010 and on on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life 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 presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. This is a new impairment for this stream segment. The presumptive Class A2 (secondary contact recreation) uses, however, are assessed (monitored) as “fully supported.” The Class B(CW1) coldwater aquatic life uses remain assessed as "fully supported." The fish consumption uses remain “not assessed” due to the lack of information upon which to base an assessment. The sources of data for this assessment are (1) the results of monitoring for indicator bacteria conducted at Site 22 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 190050001) from April 2008 through October 2010 and (2) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011.
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as not supported based on levels of indicator bacteria that exceeded state water quality criteria while the Class A2 (secondary contact recreation) uses are assessed as "fully supported". The geometric means of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2008 through 2010 at UIRW Site 22 were as follows: the 2008 geometric mean was 240 orgs/100 ml, the 2009 geometric mean was 141 orgs/100 ml and the 2010 geometric mean was 119 orgs/100 ml. Two of the three geometric means (2008 and 2009) slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2009 geometric mean is below the Class A1 criterion of 126 orgs/100 ml. All three geometric means are well below the Class A2 geometric mean criterion of 630 orgs/100 ml. Seven of the 20 samples (35%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; only one of the 20 samples (5%) exceeded the Class A2 single-sample maximum criterion of 2,880 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 are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
Based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011, the Class B(CW1) uses are assessed as "fully supported". According to the updated summary, Paint Creek (aka Pine Cr.) is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population for the resident trout species at this time.
Fish consumption uses remain “not assessed” due to the lack of information upon which to base an assessment.
