ADBNet

Results of IDNR beach monitoring from 2012 through 2014 suggest that the Class A1 uses are "partially supported." Levels of indicator bacteria at Lake of Three Fires Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2012 (15 samples), 2013 (15 samples) and 2014 (18 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 Lake of Three Fires Beach, the geometric means from 2012, 2013 and 2014 were all below the Iowa water quality standard of 126 E.  coli orgs/100 ml.   The geometric mean was 26 E.  coli orgs/100 ml in 2012, 16 E.  coli orgs/100 ml in 2013 and 121 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 13% in 2012, 7% in 2013 and 44% in 2014.   The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2014.   According to IDNR's assessment methodology and U.S.  EPA guidelines, these results suggest "partially supported" of the Class A1 uses.

For the 2016 assessment/listing cycle, however, the Class A1 (primary contact recreation) uses of Lake Of Three Fires are assessed (monitored) as "not supported" due to poor water transparency and aesthetically objectionable conditions caused by algae blooms based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 70, 65, and 73 respectively for Lake Of Three Fires. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Lake Of Three Fires in between the Eutrophic and the Hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, very poor water transparency, and very high levels of phosphorus in the water column. The data show 2 violations of the Class A1 criterion for pH in 15 samples.

The level of inorganic suspended solids was relatively low at Lake Of Three Fires, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Lake Of Three Fires (2.5 mg/L) was ranked 39th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a large population of cyanobacteria exists at Lake Of Three Fires, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 94% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (44.8 mg/L) was ranked 117th 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 2010-2014. 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 (monitored) as "not supported" due to violations of the Class B(LW) criterion for DO. Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), 6 violations of the criterion for dissolved oxygen in 15 samples(40%), and 2 violations of the criterion for pH in 15 samples(13%). Based on IDNR's assessment methodology these violations are significantly greater than 10% of the samples and therefore suggest impairment (not supported/monitored) of the Class B(LW) uses of Lake Of Three Fires.

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 2010-2014 show that nitrate levels are extremely low at this lake (maximum value = 1.6 mg/l; median = 0.1 mg/l), these data are not sufficient for developing a valid assessment of support of the Class C uses.

Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Lake of Three Fires in 1998 and 2006.   Although the composite samples of fillets from channel catfish contained low levels of most contaminants in both the 1998 and 2006 samplings, the samples of largemouth bass had elevated levels of mercury.   Levels of mercury in the composite sample of largemouth bass fillets were 0.235 ppm in the 1998 sample and 0.37 ppm in the 2006 sample.   The level of mercury in the 2006 sample exceeds the IDNR/IDPH trigger level of 0.3 ppm for a one meal/week advisory.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   But, this elevated level does indicate a concern and the need to conduct additional monitoring to better define contaminant levels in fish from this lake.   Follow up monitoring was conducted in 2008.   The level of mercury in the composite sample of largemouth bass fillets was 0.207 ppm, which is below the one meal per week advisory trigger level (0.3 ppm).   Therefore the fish consumption uses at Lake of Three Fires will remain assessed as "fully supported."

Note:  A TMDL for impacts of siltation and nutrients at Lake of Three Fires was prepared by IDNR and approved by EPA in 2002; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle.   A TMDL for indicator bacteria at Lake of Three Fires was prepared by IDNR and approved by EPA in 2010.   Because not all Section 303(d) impairments identified for the 2016 assessment/listing cycle (dissolved oxygen) are addressed in the two TMDLs, this lake is placed into IR Category 5a (TMDL needed) for the 2016 assessment/listing cycle.