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 current (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 (2008) 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 (evaluated) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class B(WW2) aquatic life uses are “not assessed” due to the lack of water quality data/information upon which to base an assessment. Fish consumption uses are “not assessed” due to the lack of fish contaminant monitoring in this stream segment. 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 were assessed (evaluated) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A1 criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.
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 these results indicate impairment of the primary contact recreation uses designated for this stream segment, the number of samples is relatively low and does not meet IDNR guidelines for developing a “monitored” (i.e., higher confidence) assessment. Thus, the assessment type is considered “evaluated” (lower confidence). While lower confidence assessments are not appropriate for addition to the state’s Section 303(d) list of impaired waters (IR Category 5), this assessment is appropriate for addition to the state list of waters in need of further investigation (IR Categories 2b or 3b).
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.]
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.
