Assessment Comments
Assessment is based on results of (1) IDNR/UHL monthly ambient monitoring 1 mile N of St. Joseph, Kossuth Co. from 2002-04 and (2) an IDNR investigation of a fish kill in December 2001.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "partially supported" due to high levels of indicator bacteria (E. coli). The Class B(WW) aquatic life uses are 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 2002 through 2004 and (2) 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, meet requirements for addition of this river segment to Iowa's Section 303(d) list.
EXPLANATION: The Class A uses were assessed (monitored) as "partially supported" based on results of monitoring for indicator bacteria (E. coli). Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of the 2006 Section 305(b) assessments and Section 303(d) listings.
The geometric mean level of indicator bacteria (E. coli) in the 24 samples collected (122 orgs/100ml) during the recreational seasons of 2002, 2003, and 2004 is slightly less than the Iowa Class A water quality criterion of 126 orgs/100ml. Nine of the 24 samples (38%), however, exceeded Iowa’s single-sample maximum value of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting (pgs 3-33 to 3-35 of U.S. EPA 1997b), if levels of E. coli exceed the single-sample maximum value in more than 10% of the samples, the primary contact recreation uses should be assessed as “partially supported.” According to IDNR’s assessment/listing methodology, these results suggest that significantly greater than 10% of the samples exceed IDNR’s single-sample maximum value, thus suggesting that the Class A uses should be assessed as “partially supported/impaired”.
The Class B(WW) uses are 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(WW) aquatic life uses of this river reach were assessed as "partially supported." Also, according to IDNR’s assessment methodology, if no kill has occurred over the last three years (2002, 2003, and 2004 for the current assessment), the assessment should be considered “evaluated” (i.e., lower confidence), and the waterbody should be placed into 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 2002-2004 period, the assessment type is changed from “partially supported/monitored” (i.e., higher confidence) to “partially supported/evaluated” (i.e., lower confidence).
In contrast, results of IDNR/UHL ambient monitoring suggest relatively good water quality and “full support” of the Class B(WW) uses. None of the approximately 35 samples collected during the 2002-2004 assessment period violated Class B(WW) water quality criteria for pH or ammonia-nitrogen. None of the approximately 7 samples analyzed for pesticides or the 10 samples analyzed for toxic metals violated state water quality criteria. One of the 34 samples analyzed for dissolved oxygen, however, violated the Class B(WW) criterion of 5.0 mg/l (this sample contained a dissolved concentration of 3.7 mg/l). According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), however, a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen nonetheless suggest "full support" of aquatic life uses. Thus, the percentages of violations of the dissolved oxygen criterion at this station (3%) does not suggest an impairment of aquatic life uses in this stream segment.
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 above).
