Assessment Comments

Assessment is based on results of IDNR ambient monthly monitoring near Gifford, IA.

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.]

SUMMARY:  The Class A (primary contact recreation) uses were assessed as "not supported."  The Class B(WW) aquatic life uses were assessed as "fully supported."  Fish consumption uses were not assessed.   The sources of data for this assessment are (1) the results of monthly monitoring from October 1999 through September 2001 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 "not supported."  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."  Thirteen of the 15 samples collected from the Gifford station during the 2000 and 2001 recreational seasons were collected at flows not materially affected by surface runoff.   The geometric mean level of indicator bacteria (fecal coliforms) in these 13 non-runoff-affected samples (249 orgs/100ml) is above the Iowa Class A water quality criterion of 200 orgs/100ml.   In addition, three of the 13 samples (23%) 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 greater than 200 orgs/100ml, the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).   The Class B(WW) aquatic life uses were assessed as "fully supported" based on results of monitoring from the IDNR ambient station near Gifford in 2000 and 2001.   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 24 samples analyzed during this biennial period.   Fish consumption uses were not assessed due to a lack of fish tissue monitoring in this river segment.