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 classified only for general 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 and for Class B(WW1) 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(WW1) 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 previously un-assessed stream segment. The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported” based on results of chemical/physical monitoring from 2005 through 2008. This source of data for this assessment is the results of IOWATER volunteer water quality monitoring conducted on Price Creek at the following seven stations (moving from downstream to upstream): (1) Station PC-7 at New Jerusalem Church, T Ave. (STORET ID 948067), (2) Station PC-6 at 110th St. and S Ave. (STORET ID 948074), (3) Station PC-5 at R Ave. (STORET ID 948058), (4) Station PC-4 at 110th St., 0.5 mile west of R. Ave. (STORET ID 948070), (5) Station PC-3 at PP Ave. (STORET ID 948071), (6) Station PC-2 at P Ave. (STORET ID 948059), and (7) Station PC-1 at N Ave, 0.5 mile N of 110th St. (STORET ID 948060).
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 seven 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 seven stations exceed the Class A1 geometric mean criterion of 126 orgs/100 ml with geometric means ranging from a low of 260 orgs/100 ml at Station PC-1 to a maximum of 922 orgs/100 ml at Station PC-4. 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, and pH show no violations of Class B(WW1) criteria in the approximately 10 samples collected at each of the seven monitoring stations in this segment and show no violations of Class B(WW1) criteria for ammonia in the approximately three samples analyzed from each of the seven stations. The lack of violations suggests “full support” of the presumptive Class B(WW1) 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 low. The maximum level reported in the combined 25 samples analyzed from the seven stations was 0.8 mg/l in the sample collected from Station PC-7 on July 16, 2005. The next-highest ammonia level in the combined dataset was 0.25 mg/l; 15 of 25 samples reported as less than the detection level of 0.05 mg/l. The pH level for the July 16, 2005 sample from Station PC-7 was reported as 8 pH units, and the water temperature was 24.4C. At this temperature and pH, the sample ammonia level of 0.8 mg/l does not violate Iowa’s Class B(WW1) chronic criterion for ammonia (early life stages present). Arbitrarily assuming a pH level of 9 for this sample considerably lowers the chronic criterion (from 5.62 to 0.88 mg/l) but does not result in a violation of the chronic criterion.
