Dry Branch IA 01-TRK-2002

The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.  The geometric means of indicator bacteria (E. coli) in the eight monthly samples collected during the recreational season of 2012 (1,700 orgs/100 ml); the geometric mean of the nine samples collected during the recreational season of 2013 (3,702), and the geometric mean of the eight samples collected during the recreational season of 2014 (183 orgs/100 ml) all exceeded the Class A1 criterion of 126 orgs/100 ml.  Eighteen of the combined 25 samples (72%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). 

Results of water quality monitoring from April 2012 to November 2014 do not suggest impairment of the presumptive Class B(WW1) aquatic life uses.  No violations of Class B(WW1) water quality criteria for ammonia (15 samples), dissolved oxygen (24 samples), pH (23 samples), temperature (24 samples, or chloride (16 samples )occurred in the samples analyzed. 

A fish kill occurred in this stream on or before May 2, 2004.  The cause of the kill was identified as a fertilizer spill.  An estimated 16,341 fish were killed with an estimated value of $1,942.  All fish killed were non-game species including minnows (14,534), suckers (91), stonerollers (222), and darters (1,494).  Approximately 1.25 miles of stream was affected.  The kill occurred in Section 28 of T96N, R8W, Winneshiek County.  According to the IDNR investigation of the kill, the spill sent approximately 1,250 gallons of fertilizer into Dry Branch Creek.  According to the IDNR investigation, a farmer traveling downhill on a gravel road lost control of a trailer with a fertilizer nurse tank; the tank burst as a result of the accident.  A mixture of approximately 1,000 gallons of 32 percent nitrogen fertilizer, and 250 gallons of thiosulfate, a chemical enhancement for fertilizer, spilled into the creek. 

According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.  If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing.  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 will be placed in IR Category 4d (impaired but TMDL not required).  Thus, this assessment segment was placed in Category 4d of Iowa’s 2006 Integrated Report.  IDNR considers IR 4d fish kill waters with no subsequent kills in at least the five years subsequent to the kill as appropriate for movement to IR categories 2b or 3b (i.e., Iowa’s list of waters in need of further investigation).  Because this fish kill occurred more than five years ago and no subsequent kills have been reported, this assessment segment will was moved to Category 3b of Iowa’s 2012 Integrated Report.  Because no fish kills have occurred in this stream segment for over 10 years, this assessment was moved to IR Category 3a (not assessed) for the 2014 IR cycle.