Assessment Comments
Assessment remains based on results of monitoring for indicator bacteria conducted at Site 8 of the Upper Iowa River Watershed (UIRW) project from April 2008 through October 2010.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) 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 now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2012) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to levels of indicator bacteria that exceeded state water quality criteria. The Class B(WW2) aquatic life uses remain “not assessed” due to the lack of information upon which to base an assessment. The source of data for this assessment is the results of monitoring for indicator bacteria conducted at Site 8 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 191910002) from April 2008 through October 2010.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2008 through 2010 at UIRW Site 8 were as follows: the 2008 geometric mean was 629 orgs/100 ml, the 2009 geometric mean was 550 orgs/100 ml and the 2010 geometric mean was 706 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Nineteen of the 21 samples (90%) 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 are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, the Class A1 uses are assessed (monitored) as not supported.
The Class B(WW2) aquatic life uses remain “not assessed” due to the lack of information upon which to base an assessment.
