Assessment Comments
Assessment is based on monitoring conducted on Honey Creek just upstream from Mead Cemetery (STORET station 15280003) as part of the Lake Delhi watershed assessment from April to June, 2006.
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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2010) 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 that exceed state water quality criteria. This assessment represents a new addition to Iowa’s Section 303(d) list. 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 just upstream from Mead Cemetery (STORET station 15280003) as part of the Lake Delhi watershed assessment from April to June, 2006.
EXPLANATION: The 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 mean of E. coli in the 7 samples collected at the monitoring station on Honey Creek was 3,282 orgs/100 ml. All seven of the samples collected (100%) exceeded Iowa’s 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 the geometric mean of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Although IDNR’s listing methodology requires that a minimum of ten E. coli samples be collected over a three-year period to support a Section 303(d) listing, this segment is being added to Iowa’s 2010 Section 303(d) list based on overwhelming evidence of impairment. That is, even if three additional samples had been collected, and each of these three samples had less than 10 orgs/100 ml (the INDR detection level), the resulting geometric mean of E. coli (577 orgs/100 ml) would still have far exceeded Iowa’s Class A1 criterion of 126 orgs/100 ml. Thus, the Class A1 uses of this segment are assessed (“monitored”) as “not supported” and are being added to Category 5p of IDNR’s 2010 Integrated Report (Iowa’s Section 303(d) list).
The Class B(WW2) aquatic life uses were 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 station 15280003 on Honey Creek as part of the Lake Delhi watershed assessment project, 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.]
