Assessment Comments
Assessment is based on (1) repeated occurrence of fish kills (May 1997, September 1998, January 2002, and August 2002) and (2) results of IDNR/UHL biological (biocriteria) monitoring in 1999: Fish IBI= 32(fair), BM-IBI= 61(good).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed as “not supported” due to reoccurring fish kills in this river segment, with kills occurring the following dates: May 1997, September 1998, January 8, 2002, and August 8, 2002. Results of IDNR/UHL biological monitoring in 1999 also suggest impairment of these uses.
EXPLANATION: Historical fish kills occurred on this segment of the Floyd River on May 17, 1997 and on September 24, 1998. More recent kills occurred on January 8, 2002 at Sheldon and on August 8, 2002 at Hospers.
The May 1997 kill occurred near Sheldon and was caused by an unintentional discharge of animal waste to the river. The discharge occurred during the lowering of a feedlot lagoon by using irrigation hose and pipe to pump liquid manure from the lagoon to the application site approx. 1 mile away. A break in the line occurred where the line crossed the Floyd River. The pumping ceased shortly (2-3 minutes) after the break, with an estimated 900 gallons per minute being pumped. The total number of fish killed was estimated at 5. Restitution for this kill was requested and received by DNR.
The September 1998 kill occurred on at, and 15 miles downstream from, Sheldon in Sioux County. Contents of a catchment basin surrounding a tank with 28% nitrogen were pumped into a storm sewer following a rainfall event. Toxic materials were discharged from the storm sewer to a drainage way one-quarter mile from the Floyd River. An estimated 408,000 fish were killed over the 15 mile reach affected by the kill. Restitution for this kill was requested and received by DNR.
The kill in January 2002 resulted from discharge of liquid nitrogen from a farmers coop facility in Sheldon. Ice conditions prevented the use of usual methods to estimate fish loss. The numbers of fish killed from Sheldon to Alton were estimated based on a previous fish kill evaluation on this same river reach in 1998. Ammonia readings of greater than 250 ppm were reported.
The kill in August 2002 occurred near Hospers. The kill started near the bridge at 350th Street; approximately 2 miles of river was affected. An estimated 5,800 fish were killed. No cause of this kill was identified, although feedlot runoff delivered to the river by recent rains was suspected as the cause.
According to DNR's assessment methodology for Section 305(b) reporting, occurrence of two or more pollutant-caused kills within the most recent three-year period (2000-2002) indicates that the aquatic life uses are "not supported." In addition, pollutant-caused fish kills for which a responsible party was not identified suggest the potential for additional kills to occur and suggest that addition to Iowa’s Section 303(d) list is appropriate. The relatively large number and variety of kills in this river segment, centering around the towns of Sheldon and Hospers, suggests an ongoing, although potentially unrelated, impacts to the aquatic life of this river reach.
In addition to results of fish kill investigations that suggest impairment, results of IDNR/UHL biological monitoring in 1999, conducted as part of the IDNR’s stream biocriteria project, also suggest impairment of the Class B(LR) aquatic life uses. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 Fish IBI score was 32 (fair) and the BM-IBI score was 61 (good). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
