Big Spirit Lake IA 06-LSR-1655

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 Big Spirit Lake as part of the DNR beach monitoring program.Crandall's Beach wasmonitored once per week during the primary contact recreation seasons(May through September) of 2014 (15 samples), 2015 (16 samples) and 2016 (15 samples), as part of the DNR beach monitoring program.Marble Beach wasmonitored once per week during the primary contact recreation seasons(May through September) of 2014 (15 samples), 2015 (17 samples) and 2016 (15 samples), as part of the DNR beach monitoring program.Orleans Beach Area Beach wasmonitored once per week during the primary contact recreation seasons(May through September) of 2014 (15 samples), 2015 (16 samples) and 2016 (15 samples), as part of the DNR beach monitoring program.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 Crandall's 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 17 E. coli orgs/100 ml in 2014, 11 E. coli orgs/100 ml in 2015 and 15 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 7% in 2014, 6% in 2015 and 13% 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 Marble 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 28 E. coli orgs/100 ml in 2014, 37 E. coli orgs/100 ml in 2015 and 22 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 20% in 2014, 12% in 2015 and 13% 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 Orleans Beach Area 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 107 E. coli orgs/100 ml in 2014, 41 E. coli orgs/100 ml in 2015 and 15 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 33% in 2014, 13% in 2015 and 0% 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.

For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Big Spirit Lake are assessed (monitored) as "fully supported" 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 57, 59, and 57 respectively for Big Spirit Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Big Spirit Lake in the Eutrophic category. These values suggest relatively low levels of chlorophyll a and suspended algae in the water, relatively good water transparency, and relatively low levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 15 samples.

The level of inorganic suspended solids was low at Big Spirit Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Big Spirit Lake (1.6 mg/L) was ranked 9th among the 138 lakes by the ISU lake survey.

Data from the 2012-2016 ISU lake survey suggest a large population of cyanobacteria exists at Big Spirit Lake, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 98% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (58.3 mg/L) was ranked 120th of the 138 lakes sampled. This median is in the worst 25% of the 138 lakes sampled. The presence of a large population of cyanobacteria at this lake suggests a potential violation of Iowa's narrative water quality standard protecting against the occurrence of nuisance aquatic life. This assessment is based strictly on the distribution of the lake-specific median cyanobacteria values from 2012-2016. Median levels greater than the 75th percentile of this distribution were arbitrarily considered to represent potential impairment. No other criteria exist, however, upon which to base a more accurate identification of impairments due to cyanobacteria. Assessments based on level of cyanobacteria will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence) to account for this lower level of confidence.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” based on results of a fish kill investigation in August 2009 and another in August of 2011. The first kill occurred on or before August 13, 2009. Approximately 600 walleye were killed along the southeast shoreline of Spirit Lake. Results of the investigation indicate that low levels of dissolved oxygen likely caused by algae and aquatic plant decomposition caused the kill. This is the same assessment as the 2010 and 2012 assesments. Approximately 2000 of yellow perch killed on or before August 16, 2011. Results of the investigation indicate that high water temperatures and old age caused the kill. According to the DNR assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2008-2011) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill was not identified during the DNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.

Information from the DNR Fisheries Bureau and results from the ISU lake surveys suggest that the Class B(LW) uses should be assessed as "fully supported." 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 Big Spirit Lake.

The Class C (drinking water) uses are not assessed due to the lack of recent information upon which to base an assessment. The only parameter collected as part of the ISU lake surveys relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU surveys from 2012-2016 show that nitrate levels are extremely low at this lake (maximum value = 1.1 mg/l; median = 0 mg/l), these data are not sufficient for developing a valid assessment of support of the Class C uses.

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S. EPA/DNR fish contaminant (RAFT) monitoring at Big Spirit Lake in 2009. The composite samples of fillets from common carp and yellow perch had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.0343 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.Levels of primary contaminants in the composite sample of yellow perch fillets were as follows: mercury: 0.043 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 2009 RAFT sampling conducted at this lake 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.