Assessment Comments
Asssessment remains based on results of an IDNR investigation of a fish kill in November 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 (see http://www.iowadnr.gov/Portals/idnr/uploads/water/standards/files/swcdoc2.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 (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 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 (monitored) as “partially supported” due to a fish kill in November 2004. The kill was caused by a spill of ammonia fertilizer. 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. Due to the age of the kill (greater than five years), this assessment is moved from IR Category 4d to 3b for the 2012 Integrated Report.
EXPLANATION: This kill occurred on or before November 13, 2004 in Section 2 of T89N, R43W, Plymouth County. The cause of the kill was attributed to fertilizer. An ammonia nurse tank reportedly came unhooked when a truck crossed a bridge on 340th St. in Plymouth County around 10 PM Saturday, November 13, releasing approximately 25 pounds of ammonia into the creek. The IDNR investigation showed that ammonia levels in the creek were near 50 parts per million (ppm). Ammonia levels of about 8 to 10 ppm can cause a fish kill, depending on stream temperature and pH. The kill affected approximately 3 miles of this tributary. An estimated 7,323 fish were killed with an estimated value of $782. 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 if 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 2006 Integrated Report. 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.
