Assessment Comments

Assessment is based on results of (1) IDNR/UHL biological (REMAP) sampling in 2002, (2) IDNR/UHL biological (Biocriteria) sampling in 2004, (3) IDNR/UHL ambient monthly water quality monitoring NE of Statford from 2002-04, 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 2002-04.   The Class B(WW) aquatic life uses were assessed (evaluated) as "partially supported” based on results of biological monitoring in 2002 and 2004.   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)) from 2002 through 2004, (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 and 1994.  

EXPLANATION:  The Class A (primary contact recreation) uses were assessed (monitored) as "fully supported" based on results of monitoring that show levels of indicator bacteria (E.  coli) slightly above Class A criteria.   Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A 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 the 2006 Section 305(b) assessments and Section 303(d) listings.  

The geometric mean level of indicator bacteria (E.  coli) in the 24 samples collected (72 orgs/100ml) during the recreational seasons of 2002, 2003, and 2004 is well below the Iowa Class A water quality criterion of 126 orgs/100ml.   Three of the 24 samples  exceeded Iowa’s single-sample maximum value of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting (pgs 3-33 to 3-35of U.S.  EPA 1997b), if levels of E.  coli exceed the single-sample maximum value in more than 10% of the samples, the primary contact recreation uses should be assessed as “partially supported.”  According to U.S.  EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, however, these results do not suggest that the violation frequency of Iowa’s single-sample maximum criterion is significantly greater than 10% and thus these results do not suggest impairment of the Class A uses of this river segment.   The relatively low geometric mean (72 orgs/100 ml) is atypical for free-flowing Iowa rivers and suggests that relatively low levels of indicator bacteria exist in this river segment.  

The Class B(WW) aquatic life uses were assessed (evaluated) as "partially supported” based on results of IDNR/UHL biological monitoring conducted in 2002 and 2004 as part of the DNR/UHL biocriteria and REMAP projects.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 FIBI score was 49 (fair) and the BMIBI score was 47 (fair).   The 2004 FIBI score was 73 (excellent) and the BMIBI score was 57 (good).   The FIBI average was 61 and the BMIBI average was 52.   The aquatic life use support was assessed (evaluated) as Partially Supporting (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.   This assessment is considered evaluated because the drainage area (844 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed the FIBI BIC and failed the meet the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.

Results of IDNR/UHL ambient chemical/physical monitoring suggest relatively good water quality in this river segment.   Only two violations of Class B(WW) criteria for conventional parameters occurred in the 36 samples analyzed during the 2002-2004 assessment period.   One sample had a pH level of 9.3 units; this level violated the Class B(WW) (and Class A) criterion of 9.0 units.   And one sample had a dissolved oxygen concentration of 2.9 mg/l; this level violated the Class B(WW) criterion of 5.0 mg/l.   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 and dissolved oxygen at this station (both 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 ammonia-nitrogen did not violate the applicable Class B(WW) criteria in the 36 samples analyzed during the biennial period; no violations of Class B(WW) chronic criteria occurred in the seven samples analyzed for pesticides or in the 10 samples analyzed for toxic metals.  

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 Watershed Monitoring & Assessment Section 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 average percent change of plus 3%.   This site, however, is one of the few in the 1998-99 ISU survey that did not show a drastic decline in mussel richness between the 1985 and 1998-99 survey periods.   Based on these results, the results from the survey of freshwater mussels was not used to assess this river segment 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 were assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring in this river segment in 2000.   The composite samples of fillets from channel catfish and smallmouth bass had low levels of contaminants.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.   This scenario, however, does not apply to the fish contaminant data generated from the 2000 RAFT sampling conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.

Note:  A review of the results of RAFT sampling in this segment of the Boon River showed that the level of mercury in the 1994 RAFT sample of smallmouth bass fillets (0.22) slightly exceeded the IDNR/IDPH trigger level for a one meal/week advisory of 0.2 ppm.   Subsequent fish contaminant monitoring in this segment of the Boone River in 2000, however, showed much lower levels of mercury (0.039 ppm).