Assessment Comments
Assessment is based on: (1) results from the IDNR ambient monthly monitoring station near St. Joseph in Kossuth County (STORET station 10550001) from 2010 through 2012,(2) results from IDNR/UHL TMDL monitoring from May-September 2005 at Humboldt (station 11460001), and (3) results of a December 2001 fish kill investigation.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" (IR 4a) due to high levels of indicator bacteria (E. coli). The Class B(WW1) aquatic life remain assessed (evaluated) as “partially supporting” (IR 3b) due to a December 2001 fish kill. Fish consumption uses remain "not assessed" (IR 3a) due to the lack of fish contaminant monitoring in this river reach. The sources of data for this assessment include (1) results from the IDNR ambient monthly monitoring station near St. Joseph in Kossuth County (STORET station 10550001) from 2010 through 2012, (2) results from IDNR/UHL TMDL monitoring from May-September 2005 at Humboldt (station 11460001), and (3) results of a 2001 fish kill investigation.
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 "not 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 2010 geometric mean was 219 orgs/100 ml, the 2011 geometric mean was 155 orgs/100 ml, and the 2012 geometric mean was 64 orgs/100 ml. The 2010 and 2012 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2012 geometric mean is well-below the Class A1 criterion. Nine of the 24 samples (38%) 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 are "not supported" (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.”
The assessment of the Class B(WW1) aquatic life uses as “partially supporting” is based on the 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. Despite the age of these data, the aquatic life uses of this assessment segment will remain “partially supporting/evaluated” due to the 2001 fish kill, and thus this assessment will remain on Iowa’s list of waters in need of further investigation (IR Category 3b). Additional monitoring is needed in this assessment segment to update status of its aquatic communities.
Results of IDNR/UHL ambient monitoring from 2010-2012 suggest relatively good water quality and “full support” of the Class B(WW1) uses. None of the 36 samples collected during the 2010-2012 assessment period at the IDNR/UHL ambient monitoring station (10550001) violated Class B(WW1) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, temperature, chloride, or sulfate. Results of chemical/physical monitoring at the IDNR/UHL TMDL station at Humboldt (11460001) also suggested full support of the Class B(WW1) uses: none of the five samples collected from May-September 2005 violated the respective Class B(WW1) criteria for dissolved oxygen, pH, or ammonia.
Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.
