Assessment Comments

Assessment is based on results of (1) IDNR/UHL biological (REMAP) sampling in 2002, (2) IDNR/UHL biological (Biocriteria) sampling in 1998, (3) IDNR/UHL ambient monthly water quality monitoring NE of Statford from 2000-02, and (4) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2000. Data from the 1998-99 survey of freshwater mussels (Arbuckle et al. 2000) was considered but not used in the assessment.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses were assessed (monitored) as "fully supported" based on result of ambient monitoring for indicator bacteria from 2000-02.   The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported / threatened" based on results of biological monitoring in 1998 and 2002.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2000.   The sources of data used for this assessment include (1) results of IDNR/UHL monthly ambient water quality monitoring conducted on the Boone River northeast of Stratford (STORET station 10400001 (formerly Station 438056)), (2) results of IDNR/UHL biological (REMAP) monitoring conducted in 2002, (3) results of IDNR/UHL biological (Biocriteria) monitoring in 1998, and (4) results of U.S.  EPA / IDNR fish tissue (RAFT) monitoring in 2000.  

EXPLANATION:  The Class A (primary contact recreation) uses were assessed as "fully supported" based on results of monitoring that show low levels of indicator bacteria (fecal coliforms).   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."  Of the 21 samples from this station analyzed for indicator bacteria (fecal coliforms) during summers of 2000, 2001, and 2002, four samples were collected during conditions of high river flow.   These high flows resulted in monitoring at river discharges that exceeded the long-term monthly average flow plus one standard deviation of this average (flow statistics from Fischer et al.  1990).   For purposes of Section 305(b) assessments only, IDNR 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."  The geometric mean of fecal coliform bacteria in the 17 non-runoff-affected samples was 64orgs/100 ml; one of the 17 samples (6%) exceeded the EPA-recommended single-sample maximum value of 400 orgs/100 ml.   The geometric mean (64 orgs/100 ml) is well-below the state water quality criterion of 200 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean is less than 200 orgs/100ml, and less than 10% of samples exceed the single-sample maximum value of 400 orgs/ 100 ml, the primary contact recreation uses are "fully supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   Thus, the Class A (primary contact recreation) uses are assessed as "fully supported."  

The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported / threatened" based on results of IDNR/UHL biological monitoring conducted in 1998 and 2002 as part of the DNR/UHL REMAP project.   The 2002 Fish IBI score was 49 (fair) and the BM-IBI score was 47 (fair).   The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established for previous Section 305(b) reports.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.   This assessment differs from that developed for the 2002 report based on IDNR/UHL biological monitoring conducted in 1998 for the stream biocriteria project.   The 1998 Fish IBI score was 70 (good) and the BM-IBI score was 68 (good).   Thus, the aquatic life use support was assessed as fully supporting/threatened (=FS/T) for the 2000 report, based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established for previous Section 305(b) reports.  

Results of IDNR/UHL ambient chemical/physical monitoring suggest relatively good water quality in this river segment.   The only violation of Class B(WW) criteria for conventional parameters was in one of the 36 samples analyzed for pH during the 2000-2002 assessment period.   The sample collected on March 14, 2000, had a pH level of 9.3 units; this level violated the Class B(WW) (and Class A) criterion of 9.0 units.   According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-17), the percentage of violations for pH at this station (3%) does not suggest a water quality impairment (the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated).   Levels of dissolved oxygen and ammonia-nitrogen did not violate the respective Class B(WW) criteria in the 36 samples analyzed during the biennial period; no violations of Class B(WW) chronic criteria occurred in the nine samples analyzed for pesticides.  

This segment of the Boone River was sampled as part of the 1998-99 statewide study of freshwater mussels in Iowa streams and rivers (Arbuckle et al.  2000).   As part of this study, sampling results from 1998 and 1999 (Arbuckle et al.  2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987).   On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa streams and rivers from the mid-1980s to the late 1990s.   For stream segments having four or more species reported for the 1984-95 survey, results of this comparison were used by staff of the Iowa DNR Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported.   The results of this sampling on this segment of the Boone River, however, do not meet IDNR guidelines for developing an assessment of support for the aquatic life uses.   Species richness of freshwater mussels at the three sample sites in this segment was 2, 3, and 4 in the 1984-85 period and was 3, 1, and 5, in the 1998-99 period, respectively, for an average 1984-85 species richness of 3 and an averge percent change of plus 3%.   Based on these results, the aquatic life uses are considered “not assessed” due (1) to IDNR’s assessment methodology in which assessment decisions are developed only for those stream segments having an average of four or more species reported in the 1984-85 (Frest) survey and (2) the difficulty of interpreting status of mussel communities showing relatively low species richness during the both the historical (1984-85) and current (1998-99) surveys.  

Fish consumption uses remain assessed as "fully supported" based on results of U.S.  EPA / IDNR fish tissue (RAFT) monitoring in July 2000.   This monitoring showed that levels of all contaminants in the composite samples of fillets from channel catfish and smallmouth bass were well-below ½ of the respective FDA action levels and IDNR levels of concern.