Assessment Comments
Assessment is based on results of an IDNR investigation of a fish kill in May 2004.
Basis for Assessment
SUMMARY: The general uses of this stream are assessed (monitored) as “partially supported” due to a fish kill in May 2004. The kill was caused by a fertilizer spill. The party responsible for the kill was identified, and IDNR has sought restitution for the value of the fish killed and the costs incurred by IDNR during investigation of the kill. This impairment is appropriate for Category 4d of Iowa’s 2006 Integrated Report.
EXPLANATION: This kill occurred on or before May 2, 2004. The cause of the kill was identified as a fertilizer spill. An estimated 16,341 fish were killed with an estimated value of $1,942. All fish killed were non-game species including minnows (14,534), suckers (91), stonerollers (222), and darters (1,494). Approximately 1.25 miles of stream was affected. The kill occurred in Section 28 of T96N, R8W, Winneshiek County. According to the IDNR investigation of the kill, the spill sent approximately 1,250 gallons of fertilizer into Dry Branch Creek. According to the IDNR investigation, a farmer traveling downhill on a gravel road lost control of a trailer with a fertilizer nurse tank; the tank burst as a result of the accident. A mixture of approximately 1,000 gallons of 32 percent nitrogen fertilizer, and 250 gallons of thiosulfate, a chemical enhancement for fertilizer, spilled into the creek.
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 (2002-2005) 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.
