Assessment Comments
Assessment is based on bacterial monitoring conducted on Honey Creek at three locations in 2011 and 2012 (STORET stations 15280003, 15280015, and 15280017).
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 assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria during the 2011 and 2012 recreation seasons that exceeded state water quality criteria. The Class B(WW2) aquatic life uses remain “not assessed” due to the lack of water quality data/information upon which to base an assessment. The source of data used for this assessment is monitoring conducted on Honey Creek in 2011 and 2012 at three stations: (1) just upstream from Mead Cemetery (aka, Honey Creek Outlet) (STORET station 15280003), (2) at Highway 13 (STORET station 15280015) and (3) at 165th Street (STORET station 15280017). Due to the relatively few samples collected at these stations in 2012, the data from 2011 will be used as the primary basis for this assessment.
EXPLANATION: The Class A1 (primary contact recreation) are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. Results of bacterial monitoring during the recreation season of 2011 show the following: The geometric means of indicator bacteria (E. coli) in the 12 samples collected during the recreational season of 2011 at station 15280003 was 687 orgs/100 ml. The geometric means of indicator bacteria (E. coli) in the 13 samples collected during the recreational season of 2011 at station 15280015 was 696 orgs/100 ml. The geometric means of indicator bacteria (E. coli) in the 13 samples collected during the recreational season of 2011 at station 15280017 was 1,634 orgs/100 ml. The only one of these three stations with sufficient data during the 2012 recreation season was 15280015 where the geometric means of E. coli in the 9 samples collected 597 orgs/100 ml. Based on all the bacterial samples analyzed during the 2011-2012 period, the percentages of samples that exceeded the Class A1 single sample maximum criterion of 235 orgs/100 ml were very high and all suggest impairment: 93 percent of the 14 samples at station 15280003, 95 percent of the 22 samples at station 15280015, and 100 percent of the 14 samples at station 15280017. 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, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.” The geometric mean levels of E. coli in this assessment segment suggest a moderate to severe bacterial impairment.
The Class B(WW2) aquatic life uses remain not assessed due to the lack of water quality data or other water quality information upon which to base an assessment. Although data for ammonia nitrogen were collected at STORET stations 15280003 and 15280015 on Honey Creek during 2011 and 2012, supporting data for pH and temperature were not collected. Thus, INDR was not able to compare the sample ammonia values to the temperature/pH-dependent Class B(WW2) water quality criteria for ammonia.
