"The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at DNR station 10400001 on the Boone River near Stratford were as follows: the 2014 geometric mean was 81 orgs/100 ml, the 2015 geometric mean was 72 orgs/100 ml, and the 2016 geometric mean was 95 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Eight of the combined 24 samples (33%) 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). 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 2014-2016 at DNR station 10400001 on the Boone River near Stratford 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 supported."

The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported” based on results of DNR/SHL biological sampling conducted in 2012-2014 as part of the DNR/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 2012 FIBI score was 62 (good) and the BMIBI scores were 55 (fair) and 56, 59 (both good). The 2013 BMIBI score was 56 (good). The 2014 BMIBI scores were 46 and 50 (both fair). 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 1/1 times and the BMIBI scores passed the BIC 0/6 times in the last five years. This assessment is considered evaluated because the drainage area (887 and 903 mi2) above the sampling sites 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 the sites used for the assessmentdon’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).

Results of chemical/physical water quality monitoring at DNR station 10400001 on the Boone River near Stratford suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 1.3 mg/L), 36 Dissolved Oxygen samples (minimum = 7.1 mg/L), 36 Temperature samples (maximum = 27.8° c), 36 Chloride samples (maximum = 78 mg/L), or 36 Sulfate samples (maximum = 190 mg/L) occurred during monitoring from January 2014 to December 2016. One of the 35 samples (3%) analyzed for pH (range = 7.5 to 9.2) violated the Class B(WW1) criteria during the 2014-2016 monitoring period. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17) and Iowa DNR's assessment/listing methodology, a violation frequency of significantly greater than 10% for conventional parameters such as pH suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/DNR fish contaminant monitoring in this river segment in 2007. 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 2007 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.