Boyer River IA 06-BOY-1502
from confluence with Willow Cr. (S28 T78N R44W Harrison Co.) to the Harrison-Crawford county line.
- Assessment Cycle
- 2018
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Stable
- Created
- 5/30/2019 1:36:27 PM
- Updated
- 7/30/2019 12:38:40 PM
Assessment Summary
The Class A1 (primary contact recreation) uses are assessed as "not supported" due to levels of indicator bacteria that violate state water quality criteria. Although results of chemical/physical water quality monitoring at this station continue to suggest good water quality conditions and full support of aquatic life uses, the Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" based on results of DNR/SHL biological sampling conducted in 2012-2014. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment. This assessment is based on results of (1) DNR/SHL monthly ambient monitoring conducted during the 2014-2016 assessment period at the County Road F-58 bridge NE of Missouri Valley (STORET station 10430001), (2) USGS chemical/physical water quality monitoring at Logan, IA, during the 2012-2014 period and (3) DNR/SHL biological sampling conducted in 2012-2014.
Assessment Explanation
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 DNR’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 DNR 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 2014 through 2016 at the Boyer River near Missouri Valley (STORET station 10430001) were as follows: the 2014 geometric mean was 487 orgs/100 ml, the 2015 geometric mean was 1138 orgs/100 ml, and the 2016 geometric mean was 539 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Eighteen of the combined 24 samples (75%) 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 DNR’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." Results of chemical/physical water quality monitoring at the Boyer River near Missouri Valley (STORET station 10430001) suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 36 Ammonia samples (maximum = 0.1 mg/L), 36 Dissolved Oxygen samples (minimum = 6.6 mg/L), 36 pH samples (range = 7.5 to 8.7), 36 Temperature samples (maximum = 27.9 °C), 36 Chloride samples (maximum = 56 mg/L), or 36 Sulfate samples (maximum = 67 mg/L) occurred during monitoring from January 2014 to December 2016. 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, these results thus suggest “full support” of the Class B(WW1) aquatic life uses. 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 DNR 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 DNR/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 DNR’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). DNR 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).
Assessment Key Dates
1/4/2012 | Fixed Monitoring Start Date |
12/2/2014 | Fixed Monitoring End Date |
8/6/2012 | Biological Monitoring |
9/4/2013 | Biological Monitoring |
9/24/2014 | Biological Monitoring |
1/7/2014 | Fixed Monitoring Start Date |
12/7/2016 | Fixed Monitoring End Date |
Methods
230 | Fixed station physical/chemical (conventional plus toxic pollutants) |
240 | Non-fixed station physical/chemical (conventional + toxicants) |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
420 | Indicator bacteria monitoring |