Assessment Comments
Assessment is based on results of IOWATER monitoring from 2005-2008.
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 was compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria (E. coli) that exceed state water quality criteria. This is a new impairment for this stream segment. The Class B(WW2) aquatic life uses are assessed (monitored) as "fully supported” based on results of chemical/physical monitoring. This source of data for this assessment is the results of IOWATER volunteer water quality monitoring conducted from 2005 through 2008 on Price Creek at the following stations (moving from downstream to upstream): (1) Station PC-11 at Amana (STORET ID 948061), (2) Station PC-10 at Highway 151 (STORET ID 948075), (3) Station PC-9 above campground at C Street (STORET ID 948063), and (4) Station PC-8 at U Ave. and 118th St. (STORET ID 948065).
EXPLANATION: The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of IOWATER monitoring from 2005 through 2008. From nine to 10 samples from each of the four monitoring stations on Price Creek were analyzed for E. coli during the recreation seasons of 2005-08. 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: PC 11: 922 orgs/100 ml; PC 10: 1,151 orgs/100 ml, PC9: 1,228 orgs/100 ml; PC 8: 510 orgs/100 ml. 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 "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
The Class B(WW2) aquatic life uses are assessed (monitored) as “fully supporting” based on results of the water quality monitoring in this segment of Price Creek from 2005-2008. Results for dissolved oxygen, pH, and ammonia show 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 suggests “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 are 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.
