Lindsey Creek IA 01-MAQ-54

Assessment Comments

Assessment is based on bacterial monitoring conducted on Lindsey Creek at one location in 2011 (STORET stations 15280022, at 165th Street).

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.   Thus, for the current (2014) assessment, 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 “partially supported” due to levels of indicator bacteria that exceed state water quality criteria.   This is a new impairment for this assessment segment.   The presumptive Class B(WW1) aquatic life uses are not assessed due to the lack of information upon which to base an assessment.   The source of data used for this assessment are the results of bacterial monitoring conducted from May to October 2011 on Lindsey Creek at 165th Avenue in Delaware County.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to violations of Iowa’s water quality criteria for indicator bacteria.   The geometric mean of E.  coli in the 13 samples collected at the monitoring station on Lindsey Creek from May to October 2011, was 656 orgs/100 ml.   Eleven of the 13 samples (85%) 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 impaired (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).  Thus, the Class A1 uses of this segment are assessed (“monitored”) as “partially supported” and this impairment is placed in Category 5p of IDNR’s 2014 Integrated Report (Iowa’s Section 303(d) list).  

The presumptive Class B(WW1) aquatic life uses are “not assessed” due to the lack of water quality information upon which to base an assessment.