Assessment Comments

Assessment is based on results of IDNR/UHL ambient water quality monitoring NE of Gifford, IA, from 2000-02.

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment IA 02-IOW-0070-2, which extended 43 miles from Hardin/Marshall line to the east corporate limit of Iowa Falls, was split into three subsegments:  (1) Hardin/Marshall county line to South Fork Iowa River (IA 02-IOW-0070-2), (2) South Fork Iowa River to Pine Creek near Eldora (IA 02-IOW-0070-3), (3) Pine Creek to bridge in S12, T88N, R20W, Hardin Co.  (IA 02-IOW-0070-4), and (4) Hardin Co.  bridge to east corporate limit of Iowa Falls (IA 02-IOW-0070-5).   As part of this splitting, the identification number for segment IA 02-IOW-0070-3 (east corporate limit of Iowa Falls to unnamed tributary 3 miles SE of Popejoy) was changed to IA 02-IOW-0070-6.   See assessment information for the original 43-mile segment under the documentation for segment IA 02-IOW-0070-2 for earlier Section 305(b) assessments for this river reach.]

NOTE:  The placement of recent water quality assessments for this segment and the downriver segment (IA 02-IOW-0070-2) have been confused.   Because IDNR/UHL ambient monitoring station 10420001 is upstream from the confluence with the South Fork Iowa River--and is thus in segment (IA 02-IOW-0070-3)--any assessments based on monitoring data from this station should have been applied to IA 02-IOW-0070-3.    Thus, any assessments  based on data from this station and erroneously placed in the downriver segment (IA 02-IOW-0070-2) have been restored to IA 02-IOW-0070-3.   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.   I apologize for this confusion.  

2004 ASSESSMENT:  SUMMARY:  The Class A (primary contact recreation) uses were assessed (monitored) as "partially supported" due to high levels of indicator bacteria.   The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring.   Fish consumption uses were not assessed due to the lack of fish contaminant monitoring in this river reach.   The sources of data for this assessment are (1) the results of monthly monitoring from January 2000 through December 2002 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 A uses were assessed as "partially supported" due to elevated levels of indicator bacteria.   For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff.   According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff."  Nineteen of the 21 samples collected from the Gifford station during the 2000, 2001, and 2002 recreational seasons were collected at flows not materially affected by surface runoff.   The geometric mean level of indicator bacteria (fecal coliforms) in these 19 non-runoff-affected samples (193 orgs/100ml) is just below the Iowa Class A water quality criterion of 200 orgs/100ml.   In addition, four of the 19 samples (21%) contained a level of fecal coliform bacteria that exceeded the U.S.  EPA-recommended single-sample maximum value of 400 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean is less than 200 orgs/100ml, but more than 10% or less of the samples exceed the single-sample maximum value of 400 orgs/100 ml, the primary contact recreation uses are only "partially supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   Thus, support of the Class A (primary contact recreation uses are assessed (monitored) as “partially supported.”

The Class B(WW) aquatic life uses were assessed as "fully supported" based on results of monitoring from the IDNR/UHL ambient station near Gifford from 2000 through 2002.   Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, toxic metals, and toxic organic compounds in the 36 samples analyzed during this assessment period.  

Fish consumption uses were not assessed due to a lack of fish tissue monitoring in this river segment.