Boyer River IA 06-BOY-1502

The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.  The geometric means of indicator bacteria (E. coli) in the 22 samples collected during the recreational seasons of 2012 through 2014 at the Boyer River at Logan by USGS were as follows: the 2012 geometric mean was 298 orgs/100 ml, the 2013 geometric mean was 162 orgs/100 ml, and the 2014 geometric mean was 2235 orgs/100 ml.  All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  Ten of the combined 22 samples (45%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "not supported"

Similarly, results of bacterial monitoring by IDNR also suggest that the Class A1 uses should be assessed as impaired.   The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2012 through 2014 at the Boyer River near Missouri Valley through the IDNR/SHL ambient stream monitoring program were as follows: the 2012 geometric mean was 125 orgs/100 ml, the 2013 geometric mean was 254 orgs/100 ml, and the 2014 geometric mean was 201 orgs/100 ml.  Two of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  Eleven of the combined 24 samples (46%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”  

Results of chemical/physical water quality monitoring at the Boyer River near Missouri Valley through the IDNR/SHL ambient stream monitoring program suggest “full support” of the Class B(WW1) aquatic life uses. Monitoring at the IDNR/SHL station NE of Missouri Valley showed no violations of Class B(WW1) water quality criteria for 36 Ammonia samples (maximum = 0.7 mg/L), 36 Dissolved Oxygen samples (minimum = 6.6 mg/L), 36 pH samples (range = 7.2 to 8.9), 36 Chloride samples (maximum = 56 mg/L), or 36 Sulfate samples (maximum = 68 mg/L) occurred during monitoring from January 2012 to December 2014. One of the 36 samples (3%) analyzed for Temperature (maximum = 32.3° c) violated the Class B(WW1) criteria during the 2012-2014 monitoring period. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as Ammonia, Dissolved Oxygen, pH, Chloride, or Sulfate suggests impairment of aquatic life uses.  Because the frequency of violations for this parameters is not greater than 10 percent, these results suggest "full support" of the Class B(LW) uses in this segment of the Boyer River.

Similarly, the results of chemical/physical water quality monitoring at the Boyer River at Logan by USGS also suggest “full support” of the aquatic life uses. Monitoring at the USGS station showed no violations of Class B(WW1) water quality criteria for 30 Ammonia samples (maximum = 0.7 mg/L), 29 Dissolved Oxygen samples (minimum = 6.6 mg/L), 30 pH samples (range = 7.6 to 8.6), 30 Temperature samples (maximum = 29.9° c), 30 Chloride samples (maximum = 75.5 mg/L), or 30 Sulfate samples (maximum = 73 mg/L) occurred during monitoring from February 2012 to September 2014. The 30 samples collected or for the pesticides chlorpyrifos or dieldrin showed no violations in the samples collected.  One of the 30 samples (3%) analyzed for DDE violated the Class B(WW1) criteria during the 2012-2014 monitoring period. According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, the results from both the IDNR and USGS monitoring stations suggest that the Class B(WW1) aquatic life uses should be assessed as "fully supporting".  

In contrast to the water quality aquatic life assessment, the aquatic life assessment based on biological sampling suggests the aquatic life uses are "partially supporting".   This evaluated biological assessment was based on data collected in 2012-2014 as part of the IDNR/SHL large river sampling project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa collected in the stream sampling reach.   The biological metrics were combined a benthic macroinvertebrate index (BMIBI).   The index rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2012-2014 BMIBI scores were 23, 29 (poor) and 49 (fair).  The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008.   The BMIBI BIC for this ecoregion is 54.   This assessment is considered evaluated because the drainage area (928 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 failed the BMIBI BIC (0/3), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn’t fall in the calibrated watershed size.   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).  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment.   Results of USGS monitoring near Logan, IA, from 2012-2014 show one violations of the human health/fish criteria for DDE and no violations of the human health/fish criteria for dieldrin in the 30 samples analyzed.