Assessment Comments
Assessment is based on (1) results of an IDNR investigation of a fish kill in April 2004 and (2) results of IDNR fish kill follow-up sampling in August 2011.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the Current (2012) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to a lack of water quality information upon which to base an assessment. The assessment of the presumptive Class B(WW2) aquatic life uses is changed from “partially supporting” (IR Category 5b) due to an April 2004 fish kill to “not assessed” (IR 3a). This change is based on results of fish kill follow-up monitoring conducted by IDNR staff in August 2011. This change represents a de-listing of the biological (fish kill) impairment.
EXPLANATION: This kill occurred on April 27, 2004. The cause of the kill was identified as animal waste from hog confinement operation. Only 1 fish was reported killed*; no value estimate was provided. No location information for the kill was provided. According to the IDNR investigation, the spill of animal (swine) waste sent approximately 1,500 gallons of manure into David’s Creek. The umbilical line (hose that runs from the confinement building to the tractor applying the manure) ruptured, thus spilling manure onto the land and through a tile line before entering the creek. Dams were constructed to stop the flow of manure into the stream. The party responsible for the kill was not identified.
According to IDNR’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.
This stream segment’s fish community was sampled on August 1, 2011 as part of the IDNR Watershed Improvement and Water Monitoring sections fishkill follow up monitoring program. Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s 2012 assessment/listing methodology) were followed. Approximately 1,200 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 1,166 fish per mile compared to the Level IV ecoregion 47e average of approximately 650 fish per mile; 71% of the expected fish taxa for this ecoregion were sampled. For detailed results of this sampling, see http://test.iowadnr.gov/bionet/Fish.aspx/Session/1277. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the 2004 fish kill event. Thus, this stream segment is being moved from impairment Category 5b of Iowa’s Integrated Report to Category 3a (designated use not assessed).
*Note: IDNR staff (JRO & TFW) surveyed Davids Creek in October 2001 as part of an IDNR stream use assessment. The fish community in the lower portion of this stream was found to be very productive and very diverse (15 species with eight species reported as "common"). Although field notes from that survey suggest that aquatic habitat in the upper reaches of this stream is limited, the report that only one fish was killed during the April 2004 kill should not be taken to imply that this stream is incapable of supporting an aquatic community.
