Catfish Creek IA 01-TRK-125

The presumptive Class A1 (primary contact recreation) uses remain assessed 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-05 of the Catfish Creek Watershed Project (4,795 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml). Six of the 11 samples (55%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Similarly, at Station WQ-13, the geometric mean of E. coli in the 10 samples collected (1,188 orgs/100 ml) also far exceeded the Class A1 geometric mean criterion. Four of the 10 samples 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 "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

The Class B(WW2) aquatic life uses are assessed as “partially supported” due to a fish kill in late August 2014. This fish kill occurred on or before August 31, 2014, west of Key West in Section 2, T88N, R2E, Dubuque County. A definitive cause of the kill could not be determined, but investigators suspected a human-related cause of the kill. The following are notes from the fish kill investigation:

[Cause] Unknown. Based on the characteristics of the kill (length, time of year, fish species composition, disposition of near dead fish) best judgment suggests the kill was caused by ammonia toxicity. This fish kill originated in section 3, 9, or 10 of T88N, R2E (downstream of Oakland Farms Road), and dead fish were found downstream to the confluence of South Fork Catfish Creek and Catfish Creek in section 2 of T88N, R2E. The length of stream with dead fish was at least 2.2 miles and could have been as much as 3.8 miles based on fishery investigation.

An estimated 455 fish were killed. The kill affected approximately 2.2 miles of stream but, as noted in the investigation report, the kill may have extended up to 3.8 miles in length. The value of the fish killed was estimated at $2,705.01; no cost of the Iowa DNR investigation of the kill was provided. No responsible party for the kill was identified.

According to DNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.