Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in February 2000.
Basis for Assessment
SUMMARY: The general uses are 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 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 (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 tribuary 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 approximatey 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. 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).
