Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in August 2005 and on results of an IDNR fish kill follow-up investigation in October 2013.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current (2014) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of information for indicator bacteria upon which to base an assessment. The assessment of the presumptive Class B(WW1) aquatic life uses of this stream is changed from “partially supporting” (IR 5b) due to a 2005 fish kill to “not assessed “ (IR 3a) based on results of a fish kill follow-up investigation conducted by IDNR staff in July 2013. This change represents a de-listing of the biological (fish kill) impairment.
EXPLANATION: This kill occurred on or before August 12, 2005. The party responsible for the kill was not identified. The kill occurred in the SE ¼ of Section 35, T88N, R2W, Dubuque Co.; approximately 0.25 miles of stream was affected. Despite a thorough investigation of the kill by IDNR field staff, no cause or source of the kill was identified. Although no estimate was given for the number of fish killed, comments from the investigation note that “suckers, chubs and minnows” were killed. Investigators concluded that this localized kill may have been caused by combination of factors; for example, manure plus lignin sulfonate (recently sprayed on a nearby road for dust control) in combination with a rainfall event of approximately 1 inch on the night of August 11. This is the first kill reported for this segment of Johns Creek. A kill occurred in the lower reach of Johns Creek (IA 01-NMQ-0110-0) in July 1985.
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 (2007-2009) 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. Any existing fish kill (5b) impairment will remain in IR Category 5b until more recent monitoring has shown full recovery of the aquatic communities affected by the kill.
This stream segment’s fish community was sampled on October 9, 2013, 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 2014 assessment/listing methodology) were followed. Approximately 700 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 1,870 fish per mile compared to the Level IV ecoregion 47f average of approximately 1,590 fish per mile; 73% of the expected fish taxa for this ecoregion were sampled. For detailed results of this sampling, see https://programs.iowadnr.gov/bionet/Sites/960. 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 August 2005 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).
