Assessment Comments
Assessment is based on results of an IDNR investigation of a fish kill in June 2004.
Basis for Assessment
[Note: Prior to the current (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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2008) 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 are "not assessed" due to a lack of water quality information upon which to base an assessment. The presumptive Class B(WW-1) aquatic life uses of this stream are assessed (monitored) as “partially supported” due to a fish kill in June 2004. The kill was caused by a spill of an industrial chemical (sulfuric acid). Although the party responsible for the kill was identified, IDNR records do not indicate that IDNR sought restitution for the value of the fish killed or for the costs incurred by DNR during the investigation of the kill. Thus, this impairment is appropriate for Category 5b of Iowa’s 2006 Integrated Report (=Section 303(d) list).
EXPLANATION: This kill occurred on or before June 17, 2004. The cause of the kill was identified as a spill of an industrial chemical (sulfuric acid). An estimated 1,736 fish were killed, including a number of non-game and game fish species. The estimated value of the fish killed was $3,570. The kill occurred in sections 28, 33, and 32 of T72N, R13W, Wapello County; approximately 0.9 miles of this stream was affected. The kill began at the Highway 34 bridge east of Ottumwa and extended 1546 yards downstream to the confluence with the Des Moines River. According to the IDNR investigation, approximately 2,500 gallons of sulfuric acid spilled from an overturned transport truck at the Highway 34 bridge over Sugar Creek. The party responsible for the kill was 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 (2005-2007) 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. For previous assessment/listing cycles, IDNR had considered fish kill-impaired (IR 5b) waters with no subsequent kills in the three year subsequent to the kill as appropriate for de-listing and for movement to IR categories 2b or 3b (i.e., Iowa’s list of waters in need of further investigation). Due, however, to EPA uncertainty regarding the full recovery of the aquatic life following the kill, 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. Thus, this assessment segment will remain in Category 5b of Iowa’s 2008 Integrated Report.
