Soldier River IA 06-SOL-1673

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 23 samples collected during the recreational seasons of 2014 through 2016 at the Soldier River near Pisgah (STORET station 10430002) were as follows: the 2014 geometric mean was 660 orgs/100 ml, the 2015 geometric mean was 1116 orgs/100 ml, and the 2016 geometric mean was 1127 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Nineteen of the combined 23 samples (83%) 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 Iowa 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 Soldier River near Pisgah (STORET station 10430002) 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 = 7 mg/L), 36 pH samples (range = 7.4 to 8.6), 36 Temperature samples (maximum = 26.7 °C), 36 Chloride samples (maximum = 22 mg/L), or 36 Sulfate samples (maximum = 49 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.

However, the results of DNR/SHL biological sampling in 2012, 2013, 2015 and 2016 suggest “partial support” of the aquatic life uses of this stream. This assessment was based on data collected in 2012, 2013, 2015 and 2016 as part of the DNR/SHL stream biocriteria project. A series of biological metrics which 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 that were 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 2012, 2013, 2015 and 2016 BMIBI scores were 33, 40, 52 (all fair) and 59 (good). Fish community samples were not collected as part of this sampling. The aquatic life use support was assessed (evaluated) as "partially supporting”, based on a comparison of the BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 54. This segment passed the BMIBI BIC 1/4 times in the last five years. This aquatic life assessment is considered "monitored" because there were two or more biological samples (four BMIBI samples) collected from the segment in multiple years in a recent five year period.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.