Assessment Comments
Assessment is based on: (1) results of the IDNR-UHL beach monitoring program in the summers of 2010-2012 (2) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted in 2008 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) IDNR/EPA fish tissue (RAFT) monitoring in 1998, 2006, and 2008.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to levels of indicator bacteria that exceed Iowa’s water quality standard. Aesthetically objectionable conditions caused by turbidity and algae also cause an impairment at this lake. The Class B(LW) (aquatic life) uses are assessed (monitored) as “partially supported" due to violations to the state's criterion for dissolved oxygen. The Class C (drinking water) uses remain not assessed due to a lack of data upon which to base an assessment. Fish consumption uses are assessed (monitored) as “fully supported.” Sources of data for this assessment include (1) results of the IDNR-UHL beach monitoring program in the summers of 2008, 2009, and 2010 (2) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted in 2006 and 2008 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) IDNR/EPA fish tissue (RAFT) monitoring in 1998, 2006, and 2008.
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 2014 assessment/listing cycle (dissolved oxygen) are addressed in the two TMDLs, this lake is placed into IR Category 5a (TMDL needed) for the 2014 assessment/listing cycle.
EXPLANATION: Results of IDNR beach monitoring from 2010-2012 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 2010 (15 samples), 2011 (15 samples), and 2012 (15 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 126 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, 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).
NOTE: Based on consultation with EPA Region 7 staff in 2011, IDNR’s methodology for assessing impairments based on the geometric mean water quality criterion was changed. Prior to the 2012 listing cycle, IDNR calculated geometric means for lakes based on a 30-day periods within the recreational season. Any violation of one of these 30-day periods within 3 years resulted in an impairment of the Class A1 uses of that lake. Because water quality standards do not identify a 30 day period but instead a recreational season, Region 7 concurred that the approach used for rivers and streams with less frequent bacteria data (seasonal geometric means) would be appropriate for identifying §303(d) impairments at lake beaches. Thus, for the 2014 listing cycle, IDNR identified primary contact recreation impairments for lakes when the geometric mean of all samples from the recreation season of a given year exceeded the geometric mean criterion. This does not impact the way IDNR assesses beaches for closure to protect the recreating public in the short term.
At Lake of Three Fires beach, the geometric means from 2010-2012 were all below the Iowa water quality standard of 126 E. coli orgs/100 ml. The geometric mean was 110 E. coli orgs/100 ml in 2010, 41 E. coli orgs/100 ml in 2011, and 26 E. coli orgs/100 ml in 2012. The percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was 40% in 2010, 20% in 2011 and 13% in 2012. The number of samples exceeding the single-sample maximum criterion was significantly greater than 10% in 2010 and therefore suggests impairment of the Class A1 uses. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest “partial support” of the Class A1 uses.
Lake of Three Fires was sampled as part of IDNR’s Safe Lakes Program, which aims to identify sources of bacteria to selected beaches where bacteria levels have consistently violated the state water quality criteria. The Safe Lakes Program found that wildlife (mainly geese) were the likely source of bacteria to Lake of Three Fires. Geese were noted regularly during sampling. Also, bacteria levels throughout the watershed were found to be consistently low, while bacteria levels in the sand were very high suggesting that inputs from the watershed were less significant than bacteria inputs at the beach.
Results from the ISU lake survey and the UHL ambient lake monitoring program from 2008-2012 suggest that the Class A1 (primary contact recreation) uses for Lake of Three Fires be assessed (monitored) as “partially supported” due to aesthetically objectionable conditions due to turbidity and algae. Using the median values from these surveys from 2008-2012 (approximately 14 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 69, 68, and 74 respectively for Lake of Three Fires. According to Carlson (1977) the Secchi depth and chlorophyll a values place Lake of Three Fires in between the eutrophic and the hypereutrophic categories while the total phosphorus value places Lake of Three Fires in the hypereutrophic category. The 2014 values suggest high levels of chlorophyll a and suspended algae in the water, poor water transparency, and high levels of phosphorus in the water column.
Based on data from the ISU and UHL surveys in 2008-2012, the median concentration of inorganic suspended solids was 2.5 mg/L, and ranked34th of the 134 lakes monitored by these programs.
Data from the 2008-2012 ISU and UHL surveys suggest a very large population of cyanobacteria exists at Lake of Three Fires. These data show that cyanobacteria comprised 94% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (51.7 mg/L) and ranked 121st of the 134 lakes sampled. This median is in the worst 25% of the 134 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 2008-2012. 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 “fully supported” based on information from the IDNR Fisheries Bureau and results of the ISU and UHL lake surveys. Information from the IDNR Fisheries Bureau suggests that water clarity and fish populations have improved at Lake of Three Fires following a dredging project and fishery renovation initiated in 2004. However, high levels of algae and limited rooted aquatic plant growth remain concerns at this lake.
Results of the ISU and UHL lake surveys data from 2008-2012 also suggest "partial support" of the Class B(LW) uses. These data show no violations of the Class B(LW) criteria for ammonia in 14 samples. There were 4 violations of the criterion for dissolved oxygen in 14 samples (29%). Based on IDNR's methodology, these violations constitute significantly greater than 10% of the samples, and therefore, suggest "patial support" of the Class B(LW) uses. Results also showed 2 violations of the Class A1,B(LW) criteria for pH in 14 samples. Based on IDNR’s assessment methodology, however, these violations are not significantly greater than 10% of the samples necessary to suggest impairment of the Class B(LW) uses.
The Class C (drinking water) uses remain "not assessed" due to lack of information upon which to base an assessment. The only parameter collected as part of the ISU and UHL lake surveys relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU and UHL surveys from 2008-2012 show that nitrate levels are very low at this lake (maximum value = 2.6 mg/l; median = 0.5 mg/l) compared to the MCL for nitrate (10 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."
