Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in June 2004.
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 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" (IR 3a) 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 remain assessed (evaluated) as “partially supported” (IR 3b) due to a fish kill in June 2004. The kill was caused by a spill of an industrial chemical (sulfuric acid). The party responsible for the kill was identified and IDNR has 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 3b of Iowa’s Integrated Report.
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 1,546 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 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. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required). IDNR feels that (1) TMDLs should not be required for kills caused by a one-time illegal or unauthorized release of manure or other toxic substance where enforcement actions were taken and (2) enforcement action is more appropriate, efficient, and effective for addressing a spill-related impairment than is the TMDL process. Thus, this assessment segment was moved to Category 4d of Iowa’s 2010 Integrated Report from Category 5b due to the information regarding restitution being sought. This impairment remained in IR Category 4d for the 2012 Integrated Reporting cycle. According to the IDNR assessment/listing methodology, if no additional fish kills have occurred over at least a five-year period, the assessment of impairment should be considered “evaluated” (i.e., of lower confidence), and the waterbody segment should be moved from IR Category 4d to IR Category 3b (list of waters in need of further investigation). Thus, because this kill occurred more than five years ago and because no subsequent kills have been reported, this impairment is moved to Category 3b of the Integrated Report and will be added to Iowa’s list of waters in need of further investigation.
