Assessment Comments
Assessment remains based on results of IOWATER monitoring from 2005-2008 and is based on results of Section 319 bacteria monitoring in 2011.
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 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. The presumptive Class B(WW1) aquatic life uses remain assessed (monitored) as "fully supported” based on results of chemical/physical monitoring from 2005 through 2008. This sources of data for this assessment are the results of IOWATER volunteer water quality monitoring conducted from 2005-2008 and the results of Section 319 monitoring conducted in 2011 on Price Creek at the following seven stations (moving from downstream to upstream): (1) Site 7 at T Avenue (STORET IDs 948067 (IOWATER) and 13480007 (319), (2) Site 6 at 110th St. and S Avenue (STORET IDs 948074 (IOWATER) and 13480006 (319), (3) Site 5 at R Avenue (STORET IDs 948058 (IOWATER) and 13480005 (319), (4) Site 4 at 110th St. (STORET IDs 948070 (IOWATER) and 13480004 (319), (5) Site 3 at PP Avenue (STORET IDs 948071 (IOWATER) and 13480003 (319), (6) Site 2 at P Avenue (STORET IDs 948059 (IOWATER) and 13480002 (319), and (7) Site 1 at NN Avenue (STORET IDs 948060 (IOWATER) and 13480001 (319).
EXPLANATION: The presumptive Class A1 uses remain assessed (monitored) as "not supported" based on results of Section 319 bacteria monitoring from June to November 2011. Eleven samples from each of the seven monitoring stations on Price Creek were analyzed for E. coli during the recreation season of 2011. The geometric mean levels of indicator bacteria (E. coli) at these seven stations and the number of samples exceeding the Class A1 single-sample maximum criterion of 235 orgs/100 ml were as follows (listed from downstream to upstream):
Site 7: GM= 459 orgs/100ml; 8 of 11 samples (73%) > single sample maximum criterion.
Site 6: GM= 747 orgs/100ml; 10 of 11 samples (91%) > single sample maximum criterion.
Site 5: GM= 796 orgs/100ml; 10 of 11 samples (91%) > single sample maximum criterion.
Site 4: GM= 649 orgs/100ml; 9 of 11 samples (82%) > single sample maximum criterion.
Site 3: GM= 859 orgs/100ml; 10 of 11 samples (91%) > single sample maximum criterion.
Site 2: GM= 459 orgs/100ml; 10 of 11 samples (91%) > single sample maximum criterion.
Site 1: GM= 459 orgs/100ml; 10 of 11 samples (91%) > single sample maximum criterion.
All seven stations exceed the Class A1 geometric mean criterion of 126 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 remain assessed (monitored) 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(WW1) criteria that was collected as part of Section 319 monitoring in 2011 was water temperature; none of the combined 69 samples collected at the seven stations violated the Class B(WW2) criterion for water temperature.) The 2005-08 results for dissolved oxygen, and pH showed no violations of Class B(WW1) criteria in the approximately 10 samples collected at each of the seven monitoring stations in this segment and showed 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.
