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 2006 through 2008, (2) results from IDNR/UHL TMDL monitoring from May-September 2005 at Humboldt (station 11460001), and (3) occurrence of a fish kill in this river segment in December 2001.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria (E. coli). The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" due to a fish kill in December 2001. Support of fish consumption uses remains "not assessed" 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 2006 through 2008, (2) results from IDNR/UHL TMDL monitoring from May-September 2005 at Humboldt (station 11460001), and (3) occurrence of a fish kill in this river segment in December 2001. Because the party responsible for the 2001 fish kill was identified, and restitution for the kill was sought, this impairment is not considered appropriate for Section 303(d) listing. The impairment due to high levels of indicator bacteria, however, meets requirements for addition of this river segment to Iowa's Section 303(d) list.
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 for the 2010 cycle.
EXPLANATION: The Class A1 uses are assessed (monitored) as "not supported" based on results of monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the 20 samples collected (138 orgs/100ml) during the recreational seasons of 2006 through 2008 slightly exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Five of the 20 samples (25%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Results of TMDL-related monitoring during the 2005 recreational season at Humboldt also suggested impairment of the Class A1 uses. The geometric mean level of indicator bacteria (E. coli) in the 5 samples collected (505 orgs/100ml) far exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Four of the five samples (80%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on the occurrence of a fish kill in this assessment segment in mid-December 2001. 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 is appropriate for Category 4d of Iowa's Integrated Report (impaired but TMDL not required). Also, according to IDNR’s assessment methodology, if no kill has occurred over the last five years (2004-2008), 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). Because no fish kills have been recorded for this segment over the 2002-2008 period, the assessment type is considered “evaluated"; this segment is appropriate for Iowa's list of waters in need of further investigation.
Results of IDNR/UHL ambient monitoring from 2006-2008 suggest relatively good water quality and “full support” of the Class B(WW1) uses. None of the 33 samples collected during the 2006-2008 assessment period at the IDNR/UHL ambient monitoring station (10550001) violated Class B(WW1) water quality criteria for dissolved oxygen, pH or ammonia-nitrogen. Neither of the two samples analyzed for toxic metals violated state water quality criteria. Results of chemical/physical monitoring at the IDNR/UHL TMDL station at Humboldt (11460001) also suggest 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 (see assessment developed for the 2000 report).
