Storm Lake IA 04-RAC-1143

Results of DNR beach monitoring from 2014 through 2016 suggest that the Class A1 uses are "partially supported." Levels of indicator bacteria were measured at multiple beaches located at StormLake as part of the DNR beach monitoring program. Awaysis Beach wasmonitored once per week during the primary contact recreation seasons(May through September) of 2014 (15 samples), 2015 (16 samples) and 2016 (14 samples). Bel Air Beach wasmonitored once per week during the primary contact recreation seasons(May through September) of 2014 (11 samples), 2015 (12 samples) and 2016 (14 samples). Chautauqua Park Beach was monitored once per week during the primary contact recreation seasons(May through September) of 2014 (11 samples), 2015 (12 samples) and 2016 (14 samples). Old Water Plant Beach was monitored once per week during the primary contact recreation seasons(May through September) of 2014 (11 samples), 2015 (11 samples) and 2016 (14 samples). Casino Beach was monitored once per week during the primary contact recreation seasons(May through September) of 2014 (11 samples), 2015 (12 samples) and 2016 (14 samples). Edson Park Beach was monitored once per week during the primary contact recreation seasons(May through September) of 2014 (11 samples), 2015 (12 samples) and 2016 (14 samples). Frank Starr Beach was monitored once per week during the primary contact recreation seasons(May through September) of 2014 (10 samples), 2015 (12 samples) and 2016 (12 samples). According to DNR’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 Awaysis Beach, the geometric mean from 2014, 2015 and 2016 wereall 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 216 E. coli orgs/100 ml in 2014, 263 E. coli orgs/100 ml in 2015 and 238 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 47% in 2014, 50% in 2015 and 50% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2014, 2015 and 2016. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

At Bel Air Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 55 E. coli orgs/100 ml in 2014, 71 E. coli orgs/100 ml in 2015 and 34 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 27% in 2014, 17% in 2015 and 14% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2014. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

At Chautauqua Park Beach, the geometric means from 2014 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean from 2015, however, was 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 69 E. coli orgs/100 ml in 2014, 166 E. coli orgs/100 ml in 2015 and 66 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 36% in 2014, 42% in 2015 and 14% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2014 and 2015. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

At Old Water Plant Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 29 E. coli orgs/100 ml in 2014, 42 E. coli orgs/100 ml in 2015 and 39 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 18% in 2014, 9% in 2015 and 14% in 2016. None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses.

At Casino Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 18 E. coli orgs/100 ml in 2014, 36 E. coli orgs/100 ml in 2015 and 30 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 0% in 2014, 8% in 2015 and 7% in 2016. None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses.

At Edson Park Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 46 E. coli orgs/100 ml in 2014, 81 E. coli orgs/100 ml in 2015 and 58 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 18% in 2014, 25% in 2015 and 29% in 2016. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2016. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

At Frank Starr Beach, the geometric means from 2014, 2015 and 2016 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 44 E. coli orgs/100 ml in 2014, 58 E. coli orgs/100 ml in 2015 and 82 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 10% in 2014, 8% in 2015 and 25% in 2016. None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses.

For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Storm Lake are assessed (monitored) as "not supported" due to poor water transparency based on information from the ISU lake survey. Using the median values from these surveys from 2012-2016 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 73, 52, and 67 respectively for Storm Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Storm Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest low levels of chlorophyll a and suspended algae in the water, very poor water transparency, and high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 15 samples.

Note: A TMDL for turbidity at Storm Lake was prepared by DNR and approved by EPA in 2005; thus, this impairment is placed in IR Category 4a (impaired; TMDL approved) for the 2010 cycle. Because however, the bacteria impairment is not addressed by the TMDL, this impairment will be placed in Category 5a of the 2016 Integrated Report (i.e., Section 303(d) list).

The level of inorganic suspended solids was very high at Storm Lake, and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Storm Lake (16.8 mg/L) was ranked 130th among the 138 lakes by the ISU lake survey.

Data from the 2012-2016 ISU lake survey suggest a small population of cyanobacteria exists at Storm Lake. These data show that cyanobacteria comprised 51% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (2.8 mg/L) was ranked 23rd of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to excessive nutrient loading to the water column and re-suspension of sediment although information from the DNR Fisheries Bureau suggests that water quality is generally improving at this lake. The ISU lake survey results, however, show relatively good chemical water quality at Storm Lake.Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 15 samples(0%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and no violations of the criterion for pH in 15 samples(0%). Based on DNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Storm Lake.