Assessment Comments
Assessment is based on results of monitoring at two sites conducted as part of a Clean Water Act Section 319 water quality project from May 2011 through May 2012 (STORET stations 15280018 and 15280020).
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general 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 and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are presumptively designated as Class A1 and Class B(WW1) waters. Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to violations of Iowa water quality criteria for indicator bacteria. This is a new impairment for this previously unassessed segment. The Class B(WW1) aquatic life uses remain “not assessed” due to the lack of water quality information upon which to base an assessment. The source of data for this assessment is the results of monitoring at two sites conducted as part of a Clean Water Act Section 319 water quality project from May 2011 through May 2012: ((1) STORET station 15280018: Honey Creek at 200th Ave (Site Honey Creek 5, [NULL 121]) and (2) STORET station 15280020: Honey Creek at Jet Rd (Site Honey Creek 7 [NULL 42])). Note: Monitoring in 2012 consisted of only one sample at each station. According to Iowa DNR's assessment and listing methodology, one sample of indicator bacteria in a recreation season is not sufficient for developing an assessment of support of recreation uses.
EXPLANATION: The presumptive Class A1 uses are assessed (monitored) as “not supported" (IR 5p) due to levels of indicator bacteria (E. coli) that exceed the Class A1 geometric mean criterion. The geometric means of indicator bacteria (E. coli) in the 13 samples collected at Honey Creek 5 during the recreational season of 2011 was 1,454 orgs/100 ml. All 13 samples exceeded the Class A1 single sample maximum criterion of 235 orgs/100 ml. The geometric mean of indicator bacteria (E. coli) in the 14 samples collected at Honey Creek 7 during the recreational season of 2011 was 1,912 orgs/100 ml. All 14 samples exceeded the Class A1 single sample maxiumu criterion of 235 orgs/100 ml.
Both of these recreation season geometric means far exceed Iowa’s Class A1 geometric mean criterion of 126 E. coli orgs/100 ml, thus indicating nonsupport of the Class A1 primary contact recreation uses. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean is greater than the respective criterion (126 orgs/100 ml for Class A1, the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). In addition, the percentage of samples with levels of E. coli that exceeded Iowa single-sample maximum criteria indicate impairment of Class A1 uses at this monitoring site.
