North Fork Catfish Creek IA 01-TRK-6486
from Hwy 20 bridge in Dubuque (S27 T89NR2E Dubuque Co.) to headwaters in NW1/4 S20 T89N R2E Dubuque 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 11:59:52 AM
- Updated
- 7/19/2019 12:01:06 PM
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 remain “not assessed” due to the lack of water quality information upon which to base an assessment. The source of data for this assessment is the results of monitoring in 2010 at Stations WQ-09 and WQ-11 of the Catfish Creek Watershed Project. This is the same assessment as developed for previous IR cycles. 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 (primary contact recreation) uses remain assessed (evaluated) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric mean of indicator bacteria (E. coli) in the 11 samples collected approximately every two weeks during the recreational season of 2010 at Site WQ-09 of the Catfish Creek Watershed Project (1,423 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml). All 11 samples (100%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. At Station WQ-11, the geometric mean in the 11 samples collected approximately every two weeks during the recreational season of 2010 at Site WQ-09 of the Catfish Creek Watershed Project (1,519 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml). Ten of the 11 samples (92%) exceeded Iowa’s 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 the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).