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/SHL ambient monthly monitoring station on Beaver Creek east of Grimes (STORET station 10770001) were as follows: the 2014 geometric mean was 745 orgs/100 ml, the 2015 geometric mean was 555 orgs/100 ml, and the 2016 geometric mean was 678 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 "partially supported."

Results of chemical/physical water quality monitoring at Beaver Creek east of Grimes (STORET station 10770001) suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 35 Ammonia samples (maximum = 0.8 mg/L), 36 Dissolved Oxygen samples (minimum = 6.9 mg/L), 35 pH samples (range = 7.4 to 8.4), 36 Temperature samples (maximum = 27.4° c), 36 Chloride samples (maximum = 160 mg/L), or 36 Sulfate samples (maximum = 120 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(WW2) aquatic life uses.

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 monitored biological assessment was based on data collected in 2012, 2013, 2015 and 2016 as part of the DNR/SHL large river/stream nutrient 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 BMIBI score was 21 (poor) and the 2013 BMIBI score was 56 (good) and the 2015 and 2016 BMIBI scores were 67, 67 (good). The aquatic life use support was assessed (monitored) 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 62. This segment passed the BMIBI BIC 2/4 times in the last five years.

This aquatic life assessment is now considered "monitored" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years during a recent five year period to be considered “monitored”. This segment had four BMIBI samples collected in the last five years.