Assessment Comments
Assessment was previously based on results of an IDNR investigation of a fish kill in August 2000.
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 (2012) 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 upon which to base an assessment. Prior to the current (2012) Integrated Reporting cycle, this segment was assessed (evaluated) as "partially supported" based on a report of a fish kill in August 2000. The presumptive Class B(WW1) aquatic life uses are now considered “not assessed” due to the lack of additional kills being reported for this stream for over 10 years. Thus, this segment is being moved from IR Category 3b to IR Category 3a (not assessed) for the 2012 cycle.
EXPLANATION: 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 anhydrous 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. Because a consent order was issued to the party responsible for the kill and monetary restitution was sought for the value of the fish killed, the affected waterbody was placed in IR Category 4d (impaired but TMDL not required) for the 2004 IR cycle. According to IDNR's assessment/listing methodology, if no additional fish kills have occurred in a 4d water over at least a three-year period following the kill, the assessment 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, this segment was moved to IR Category 3b for the 2006 through 2010 IR cycles. The presumptive Class B(WW1) aquatic life uses are now considered “not assessed” due to the lack of additional kills being reported for this stream for over 10 years. Thus, this segment is being moved from IR Category 3b to IR Category 3a (not assessed) for the 2012 cycle
