Unnamed Tributary to Waterloo Creek IA 01-UIA-6570
from mouth (T100N R6W Sec24) to state line(T100N R5W Sec7 NW) Allamakee Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 7/19/2019 9:20:13 AM
- Updated
- 7/19/2019 9:23:25 AM
The presumptive Class A1 (primary contact recreation) uses remain assessed as “not supported” due to violations of Iowa water quality criteria for indicator bacteria. The presumptive Class B(WW1) aquatic life uses are assessed as "fully supported" based on results of water quality monitoring in 2011. The source of data for this assessment is the results of monitoring at two stations monitored as part of a DNR water quality project: (1) STORET station 13030008 (Site Waterloo 4) from April through November 2010 and (2) STORET station 13030004 (Site Arch1) from June to September 2011. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment categories are considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
The presumptive Class A1 uses are assessed (evaluated) as “not supported" due to levels of indicator bacteria (E. coli) that far exceed the Class A1 geometric mean criterion. The geometric mean of indicator bacteria (E. coli) in the 18 samples collected at Station 13030006 (Waterloo 4) during the recreation season of 2010 was 1,640 orgs/100 ml. Seventeen of the 18 samples (94%) exceeded the Class A1 single sample maximum criterion of 235 orgs/100 ml. Similarly, the geometric mean of indicator bacteria (E. coli) in the 11 samples collected at Station 13030004 (Arch1) during the recreation season of 2011 was 829 orgs/100 ml. Ten of the 11 samples (91%) exceeded the Class A1 single sample maximum criterion of 235 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 is greater than the respective criterion (126 orgs/100 ml for Class A1, the primary contact recreation uses should be assessed as impaired (see pgs 3-33 to 3-35 of U.S. EPA 1997b). In addition, the percentage of samples with levels of E. coli that exceeded Iowa single-sample maximum criteria indicates impairment of presumptive Class A1 uses at this monitoring site.
Although parameter coverage was limited, results of chemical/physical water quality monitoring at Station 13030004 from June to November 2011 suggest that the presumptive Class B(WW1) aquatic life uses could be assessed as "fully supporting". No violations of Class B(WW1) water quality criteria for dissolved oxygen or temperature occurred in the 11 samples analyzed.