Assessment Comments

Assessment is based on: (1) results of IDNR/SHL monthly ambient water quality monitoring conducted on the Boone River northeast of Stratford (STORET station 10400001 (formerly Station 438056)) from 2010 through 2012, (2) results of IDNR/SHL biological sampling in 2004 and 2012, and (3) results of U.S. EPA / IDNR fish tissue (RAFT) monitoring in 2000 and 2007.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supporting" (IR 5a) based on results of ambient monitoring for indicator bacteria.   This represents a re-listing of the bacterial impairment that was de-listed for the previous (2012) IR cycle.   The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported” (IR 3b-u) based on results of biological sampling in 2004 and 2012.   Fish consumption uses remain assessed (monitored) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2000 and 2007.   The sources of data used for this assessment include (1) results of IDNR/SHL monthly ambient water quality monitoring conducted on the Boone River northeast of Stratford (STORET station 10400001 (formerly Station 438056)) from 2010 through 2012, (2) results of IDNR/SHL biological sampling in 2004 and 2012, and (3) results of U.S.  EPA / IDNR fish tissue (RAFT) monitoring in 2000 and 2007.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supporting" (IR 5a) based on results of monitoring for indicator bacteria (E.  coli) in the current assessment cycles.   This assessment represents a re-listing of the bacterial impairment that was de-listed for the previous (2012) IR cycle.   The geometric means of indicator bacteria (E.  coli) in the 25 samples collected during the recreational seasons of 2010 through 2012 at IDNR station 10400001 near Stratford were as follows:  the 2010 geometric mean was 83 orgs/100 ml, the 2011 geometric mean was 111 orgs/100 ml, and the 2012 geometric mean was 25 orgs/100 ml.   All three geometric means meet the Class A1 criterion of 126 orgs/100 ml and thus indicate “full support” of the Class A1 uses.   Seven of the 25 samples (28%), however, exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.   According to IDNR’s assessment methodology two conditions need to be met for results of monitoring for indicator bacteria to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period must be less than the state’s geometric mean criterion of 126 E.  coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state’s single-sample maximum value of 235 E.  coli orgs/100 ml.   If a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.”  Also, if significantly more than 10% of the samples exceed Iowa’s single-sample maximum value of 235 E.  coli orgs/100 ml, the Class A1 uses should be assessed as “partially supported.”  This assessment approach is based on U.S.  EPA guidelines (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).  

All geometric means for the recreation seasons of 2010-2012 at IDNR station 10400001 are below the geometric mean criterion.   The percentage of violations of Iowa’s single-sample maximum criterion for E.  coli (235 orgs/100 ml), however, is significantly greater than 10%.   Thus, the primary contact recreation uses are assessed as “partially supporting”.   Despite this impairment, the geometric mean levels at this monthly monitoring station have been below and met the Class A1 geometric mean criterion for previous IR cycles and the current (2014) IR cycle.   These results indicate consistently low levels of indicator bacteria in this segment of the Boone River.  

The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported” based on results of IDNR/sHL biological sampling conducted in 2004 and 2012 as part of the IDNR/SHL biocriteria and large river sampling 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 2004 FIBI score was 73 (excellent) and the BMIBI score was 57 (good).   The 2012 FIBI score was 62 (good) and the BMIBI scores were 55 (fair) and 56, 59 (both good).   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 1994-2008.   The riffle habitat FIBI BIC for this ecoregion are 53 and the BMIBI BIC for this ecoregion is 62.   The FIBI scores passed the FIBI BIC 2/2 times and the BMIBI scores passed the BIC 0/4 times in the last nine years.   This assessment is considered evaluated because the drainage area (887 and 903 mi2) above the sampling sites were 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 (2/2) and failed the meet the BMIBI BIC (0/4), 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.  

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous nine years (2004-2012); however, the multiple samples were not collected during a recent five-year period.   According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report).   IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).  

Monitoring at the IDNR/UHL station near Stratford showed no violations of Class B(WW2) water quality criteria during the 2010-2012 assessment period for dissolved oxygen, temperature, ammonia-nitrogen, chloride, or sulfate in the 36samples analyzed.   One of the 36 samples collected (3%) exceeded the Class B(WW1) criterion for pH.   According to U.S.  EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as pH, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   According to IDNR’s assessment/listing methodology, however, the results from IDNR station 10400001 do not indicate that greater than 10% of the samples exceed either the Class B(WW1) criteria for pH.   Thus, these results do not suggest impairment of the Class B(WW1) aquatic life uses.  

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 remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring in this river segment in 2000 and 2007.   The composite samples of fillets from channel catfish and smallmouth bass in 2000 had low levels of contaminants.   The composite samples of fillets from channel catfish and smallmouth bass in 2007 also had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.178 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.196 ppm.   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.   The fish contaminant data generated from the 2000 and 2007 RAFT sampling conducted in this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.