Assessment Comments
Assessment is based on results of monthly monitoring from January 2006 through August 2008 at the IDNR ambient monthly monitoring station located at Hardin County Road D53 approximately 1.8 miles northeast of Gifford (STORET station 10420001).
Basis for Assessment
NOTE: The placement of recent water quality assessments for this segment and the downriver segment (IA 02-IOW-0070-2) have been confused. Segment IA 02-IOW-0070_2 extends from the Hardin/Marshall county line upriver to the South Fork Iowa River; segment IA 02-IOW-0070-3 (this segment) extends from the South Fork Iowa River upriver to Pine Creek near Eldora. Because IDNR/UHL ambient monitoring station 10420001 is upstream from the confluence with the South Fork Iowa River--and is thus in this segment (i.e., IA 02-IOW-0070-3)--any assessments based on monitoring data from this station should have been applied to this segment. Thus, any assessments based on data from this station and erroneously placed in the downriver segment (IA 02-IOW-0070-2) were restored to this segment (IA 02-IOW-0070-3) as part of the 2006 Section 305(b) assessment cycle. Also, recent assessments for the downriver segment (IA 02-IOW-0070-2) are now correctly considered "not assessed" due to the lack of monitoring information upon which to base an assessment.
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from 2006-2008. Fish consumption uses remain not assessed due to the lack of fish contaminant monitoring in this river reach. The source of data for this assessment is the results of monthly monitoring from January 2006 through August 2008 at the IDNR ambient monthly monitoring station located at Hardin County Road D53 approximately 1.8 miles northeast of Gifford (STORET station 10420001).
EXPLANATION: The Class A1 uses are assessed (monitored) as "not supported" due to levels of indicator bacteria (E. coli) that exceed state criteria. The geometric mean level of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2006-2008 (181 orgs/100ml) is slightly above the Iowa Class A1 water quality criterion of 126 orgs/100ml. Nine of the 21 samples (43%) contained a level of E. coli bacteria that 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).
The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of monitoring from the IDNR/UHL ambient station near Gifford from 2006 through 2008. Monitoring at this station showed no violations of Class B(WW1) water quality criteria in the 32 samples analyzed for dissolved oxygen or ammonia or in the two samples analyzed for toxic metals. One of the 32 samples (3%) had a pH value greater than the Class B(WW1) criterion of 9.0 units (9.4 pH units). Because this violation is more related to natural conditions (i.e., high levels of primary productivity) than to a pollutant, the occurrence of high levels of pH in this river segment is not seen as a water quality impairment. Also, according to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen and pH suggest "full support" of aquatic life uses. Thus, the percentage of violations of the pH criterion at this station (3%) does not suggest an impairment of aquatic life uses of the primary contact recreation uses in this stream segment.
Fish consumption uses were not assessed due to a lack of fish tissue monitoring in this river segment.
