Assessment Comments
Assessment is based on: (1) results of the investigation of the April 2002 fish kill and (2) results of IDNR/UHL monitoring for indicator bacteria and dissolved oxygen from May 2004 to November 2006 at the County Road X16 crossing (station 15030011) as part of the Yellow River Watershed Project.
Basis for Assessment
[Note: Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class B(WW2) aquatic life uses remain assessed (monitored) as "partially supported" due to occurrence of a fish kill in April 2002 (impairment remains in IR Category 4d). This kill was caused by a spill. Sources of data for this assessment include (1) results of the investigation of the April 2002 fish kill and (2) results of IDNR/UHL monitoring for indicator bacteria and dissolved oxygen from May 2004 to November 2006 at the County Road X16 crossing (station 15030011) as part of the Yellow River Watershed Project.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A1 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 Section 305(b) assessments and Section 303(d) listings.
The geometric mean of E. coli in the 71 samples collected at the monitoring station near county road X16 during the recreational seasons of 2004 through 2006 was 345 orgs/100 ml. Thirty-eight of the 71 samples (54%) exceeded Iowa’s 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 the geometric mean 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).
The Class B(WW2) aquatic life uses remain assessed as impaired based on results of a fish kill investigation in 2002. The fish kill occurred on April 29, 2002, and resulted from the discharge of 1,500 gallons of 10-34-0 starter fertilizer from a local dealer of agricultural chemicals. Approximately 6 miles of this stream was affected; approximately 5,800 fish were killed. 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 ongoing impairment of the aquatic life uses. A fish kill also occurred on this stream in 1995; the kill was attributed to animal waste from a feedlot (see the assessment for the 1998 report for more information).
According to IDNR's assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant,” the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required). IDNR feels that (1) TMDLs should not be required for kills caused by a one-time illegal or unauthorized release of manure or other toxic substance where enforcement actions were taken and (2) enforcement action is more appropriate, efficient, and effective for addressing a spill-related impairment than is the TMDL process. IDNR sought and received restitution for the value of the fish killed in the April 2002 kill from the responsible party.
The results of IDNR/UHL water quality monitoring at station 15030011 from 2004 to 2006 showed only two violations of the Class B(WW2) criterion for dissolved oxygen (5.0 mg/l) in the 78 samples collected for a violation frequency of 3%. The minimum dissolved oxygen value was 4.3 mg/l. According to U.S. EPA guidelines for Section 305(b) reporting, if less than 10% of samples exceed state criteria for conventional parameters such as dissolved oxygen, the aquatic life uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, the results from YRWP site 15030011 do not indicate that significantly greater than 10% of the samples exceed the Class B(WW2) criterion for dissolved oxygen. Thus, these results suggest that the Class B(WW2) uses should be assessed (monitored) as “fully supported.” Despite the relatively good water quality indicated by chemical/physical monitoring, the Class B(WW2) uses remain assessed as impaired (IR Category 4d) due to the pollutant-caused fish kill in April 2002.
