Price Creek IA 02-IOW-699

[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 was compared to the applicable Class A1 and Class B(WW2) water quality criteria.] 

EXPLANATION:  The presumptive Class A1 uses remain assessed (monitored) as "not supported" based on results of Section 319 monitoring from May 2013 to September 2014.  Four samples were collected at each station during the 2013 recreation season, and 11 samples were collected at each station during the 2014 season except for Site 10 (13 samples).  The geometric mean level of indicator bacteria (E. coli) at all four stations far exceed the Class A1 geometric mean criterion of 126 orgs/100 ml (see table below).  According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion, the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b).  Thus, levels of indicator bacteria at all four monitoring stations suggest “non-support” of the presumptive Class A1 uses.  Note:  According to the data completeness guidelines in Iowa DNR’s assessment/listing methodology, at least seven independent samples per recreation season are needed to calculate a geometric mean appropriate for comparison to the Class A geometric mean criteria.  Too few samples (4) were collected at the four monitoring stations during the 2013 recreation season to allow calculation of a useful geometric mean.  During the 2014 recreation season, however, a sufficient number of samples was collected at each of the four monitoring sites.  

*Thirteen independent samples were generated at Site 10 from monitoring during the 2014 recreation season.

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supporting” based on results of the water quality monitoring in this segment of Price Creek from 2005-2008.  (The only supporting parameter with Class B(WW2) criteria that was collected as part of Section 319 monitoring in 2011; no parameters with Class B(WW1) criteria were collected during the 2012-2014 monitoring period).  During the 2005-2008 period, results for dissolved oxygen, pH, and ammonia showed no violations of Class B(WW2) criteria in the approximately 10 samples collected at each of the four monitoring stations in this segment (i.e.,  PC-11, PC-10, PC-9, and PC-8).  The lack of violations suggested “full support” Class B(WW2) aquatic life uses.  Note:  because the pH data were recorded to the nearest whole pH unit, these data were not useful for determining the strongly pH-dependent violations of aquatic life criteria for ammonia.  As monitored from 2005-2008, however, levels of ammonia in this segment of Price Creek were very low:  the maximum level reported in the 14 samples analyzed was 0.08 mg/l with 12 of 14 samples reported as less than the detection level of 0.05 mg/l.