Results of IDNR beach monitoring from 2012 through 2014 suggest that the Class A1 uses are "partially supported" Levels of indicator bacteria at Backbone Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2012 (19 samples), 2013 (18 samples) and 2014 (16 samples), as part of the IDNR beach monitoring program.   According to IDNR’s assessment methodology two conditions need to be met for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period are less than the state's geometric mean criterion of 126 E.  coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state's single-sample maximum value of 235 E.  coli orgs/100 ml. If a sampling season geometric mean exceeds the state criterion of 1000 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period and/or if significantly more than 10% of the samples in any one of the three recreation seasons 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).

At Backbone Beach, the geometric mean from 2012 was below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric means from 2013 and 2014, however, were greater than the Iowa water quality standard of 126 E. coli orgs/100ml and therefore suggests impairment of the Class A1 uses. The geometric mean was 78 E. coli orgs/100 ml in 2012, 257 E. coli orgs/100 ml in 2013 and 346 E. coli orgs/100 ml in 2014. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 37% in 2012, 50% in 2013 and 56% in 2014. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2012, 2013 and 2014. According to IDNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

The Class B(WW-1) aquatic life uses of this lake are "not assessed" due to a lack of information upon which to base an assessment.    

The fish consumption uses of this lake are “not assessed” due to the lack of fish contaminant information upon which to base an assessment.