Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in February 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 (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 the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on a report of a fish kill in February 2000. Due to the absence of kills subsequent to that kill, this assessment segment was considered “evaluated” and thus was moved from Category 4d (impaired but TMDL not required) to Category 3b (water in need of further investigation) of Iowa's 2006 Integrated Report. Because no additional kills have been reported for this stream for over 10 years, this segment is being moved to IR Category 3a (not assessed) for the 2012 cycle.
EXPLANATION: The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" due to occurrence of a fish kill. A fish kill occurred on this stream segment on February 28, 2000. The kill affected approximately 1 mile of this unnamed tributary to Buffalo Creek in Crawford Co. The kill was caused by animal waste; the responsible party was identified. An estimated 12 fish were killed. The following is paraphrased from field notes taken by IDNR field staff that investigated the kill:
"This incident was reported to the IDNR field office on February 28, 2000 as a complaint of manure runoff from a hog confinement; the kill was investigated by IDNR staff on February 29th. According to the facility operator, manure was spilled while pumping from the pits into a 2000 gallon tank wagon. Reportedly, strong winds blew the piping out of the tank while the operator was inside the building. The owner of the facility stated that the amount lost was 200 gallons; IDNR field staff feel that more than 200 gallons was lost. The manure flowed approximately 500 feet to a drainage ditch that joins this tributary of Buffalo Creek. The ditch and the tributary traverse pastured land with evidence of recent livestock habitation. Water samples were collected at the point of contamination and approximately 50 feet up and downstream. At a bridge approximately one mile downstream, 10 dead minnows were observed. Water samples were collected at this site also. The area received approximately 1/2 inch of rain on February 29. FO staff returned to the site on 3-1-00 and observed 3 dead chubs and 2 dead minnows in the bridge area. No live fish were observed between the contamination site and the bridge area. Live fish were observed upstream from the contamination."
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. According to IDNR's 2008 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, this assessment segment was moved to Category 3b of Iowa’s 2008 Integrated Report. Because no additional kills have been reported for this stream for over 10 years, any fish kill-related impacts in this segment have likely dissipated; thus, this segment is being moved to IR Category 3a for the 2012 cycle.
