Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in August 2000.
Basis for Assessment
SUMMARY: The general uses are assessed (evaluated) as "partially supported" based on a report of a fish kill in August 2000. Due to the absence of kills subsequent to that kill, this assessment segment will be considered “evaluated” and thus moved from Category 4d (impaired but TMDL not required) to Category 3b (water in need of further investigation) of Iowa's 2006 Integrated Report.
EXPLANATION: The general aquatic life uses are assessed (monitored) as "partially supported" due to occurrence of a fish kill. A fish kill occurred on this stream segment on August 19, 2000. The kill was caused by discharge of approximately 1000 gallons of water used at an ag-chemical dealer to off-gas a 10,500 gallon anydrous ammonia tank that was presumed empty. The water travelled down a drainage ditch and into the unnamed tributary to the Wapsipinicon River. No estimate of the number of fish killed was developed. The responsible party was identified and restitution was sought.
According to DNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill during an assessment period indicates "partial support" of the aquatic life uses. 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 should be placed in IR Category 4d (impaired but TMDL not required). Thus, this assessment segment was placed into Category 4d of Iowa's 2004 Integrated Report. Also, according to IDNR's assessment/listing methodology, if no additional fish kills have occurred over at least a three-year period (i.e., no kills occurred in the period 2002-2004), 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).
