East Fork Des Moines River IA 04-EDM-970

Note:  A TMDL for indicator bacteria (E. coli) was prepared by IDNR and approved by EPA in January 2009.  Thus, the 2006 bacteria impairment was moved from IR Category 5a to Category 4a (impaired; TMDL approved) for the 2008 cycle.  This impairment remains in Category 4a of Iowa’s Integrated Report. 

EXPLANATION:  The Class A1 uses are assessed (monitored) as "partially supported" based on results of monitoring for indicator bacteria (E. coli).  The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2008 through 2010 at IDNR station 10550001 near St.  Joseph were as follows:  the 2012 geometric mean was 64 orgs/100 ml, the 2013 geometric mean was 394 orgs/100 ml, and the 2014 geometric mean was 231 orgs/100 ml.  The 2013 and 2014 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2012 geometric mean is well-below the Class A1 criterion.  Ten of the 24 samples (42%) exceeded the Class A1 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 a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired” (partially supported).

Results of IDNR/UHL ambient monitoring from 2012-2014 suggest relatively good water quality and “full support” of the Class B(WW1) uses.  None of the 36 samples collected during the 2012-2014 assessment period at the IDNR/UHL ambient monitoring station (10550001) violated Class B(WW1) water quality criteria for pH, ammonia-nitrogen, temperature, chloride, or sulfate.  One of the 36 samples (3%) had a level of dissolved oxygen (4.4 mg/l) that violated the Class B(WW1) criterion of 5.0 mg/l.  According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b:  page 3-17), a violation frequency for conventional parameters such as dissolved oxygen of less than 10% does not suggest an impairment of aquatic life uses.  Thus, the results of chemical/physical water quality monitoring from 2012-2014 suggest “full support” of the Class B(WW1) aquatic life uses.  

The previous (2014) assessment of the Class B(WW1) aquatic life uses was “partially supporting” based on a December 2001 fish kill on Lotts Creek.  The kill began in Lotts Creek northeast of Whittemore in southwestern Kossuth County; the kill resulted from nitrogen fertilizer discharged from a damaged pipeline.  The kill included a 31-mile reach of Lotts Creek and an 18.5-mile reach of the East Fork Des Moines River from its confluence with Lotts Creek downstream to Dakota City in Humboldt Co.  According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates that the aquatic life uses of a waterbody are only "partially supported.”  Thus, the Class B(WW1) aquatic life uses of this river reach were assessed as "partially supported.”  Because IDNR sought restitution for the value of the fish killed, this impairment was placed in Category 4d of Iowa's 2006 Integrated Report (impaired but TMDL not required).  Also, according to IDNR’s assessment methodology, if no kill has occurred over the last five years since the kill occurred, the assessment should be considered “evaluated” (i.e., lower confidence), and the waterbody would be appropriate for IR Categories 2b or 3b (list of waters in need of further investigation).  Thus, this impairment was moved to Category 3b of Iowa’s 2008 Integrated Report and remained in IR 3b for the 2010 and 2012 cycles.  As data age beyond ten years, their ability to represent current water quality conditions is increasingly suspect.  Further, according to Iowa DNR’s assessment methodology for Integrated Reporting, if no additional kills have been reported for a non-303(d)-impaired stream for over 10 years, any fish kill-related impacts in this segment have likely dissipated, and the aquatic life uses will be considered “not assessed” (IR 3a). Thus, this segment is being moved to IR Category 3a for the 2016 cycle.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.