Patterson Creek IA 01-UIA-259
mouth (S29 T99N R6W Allamakee Co.) to east line of S3 T98N R6W Allamakee Co.
The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses are both assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed the respective state water quality criteria. The Class B(CW1) coldwater aquatic life uses are assessed as “fully supported” and the Class HH fish consumption uses remain “not assessed” due to the lack of information upon which to base an assessment. The source of data for this assessment is the results of monitoring for conducted at Site 21 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 19005004) from April 2012 through October 2014. This assessment is also based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in January 2019.
The Class A1 (primary contact recreation) uses and the Class A2 (secondary contact recreation) uses are both assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2012 through 2014 at UIRW Site 21 were as follows: the 2012 geometric mean was 860 orgs/100 ml, the 2013 geometric mean was 1,315 orgs/100 ml and the 2014 geometric mean was 289 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml; the 2012 and 2013 geometric means exceed the Class A2 geometric mean criterion of 630 orgs/100 ml. Fifteen of the 20 samples (75%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; three of the 20 samples (15%) exceeded the Class A2 single-sample maximum criterion of 2,880 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as impaired (see pgs 3-33 to 3-35 of U.S. EPA 1997b). The January 2019 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau also suggests “full support” of the Class B(CW1) aquatic life uses. According to this updated summary, Patterson Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the DNR Fisheries Bureau, this stream is placed in the category of Iowa trout Streams (a Category I stream) that exhibit fairly consistent natural reproduction and maintain a viable population of brown trout without any stocking.
The Class B(CW1) coldwater aquatic life uses are assessed as “fully supported”. Monitoring from 2012 to 2014 at Upper Iowa River Watershed Site 21 included analysis for pH, temperature, and ammonia. Of the 14 samples collected and analyzed for ammonia, 11 samples contained less than the limit of detection (0.05 mg/l); the detected samples contained 0.29, 0.09, and 0.06 mg/l of ammonia. These levels of ammonia are well below the respective Class B(CW1) aquatic life criteria for ammonia. In addition, there were no violations of Class B(CW1) criteria for pH or temperature in the 14 samples analyzed. These results do not suggest impairment of the Class B(CW1) aquatic life uses.