Assessment Comments
Assessment is based on: (1) results of the IDNR-UHL beach monitoring program in the summers of 2004, 2005, and 2006 (2) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted in 2005 and 2006 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) IDNR/EPA fish tissue (RAFT) monitoring in 1998 and 2006.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed Iowa’s water quality standard. High levels of cyanobacteria are also a concern at this lake. The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to high levels of non-algal turbidity. 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 2004, 2005, and 2006 (2) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted in 2005 and 2006 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) IDNR/EPA fish tissue (RAFT) monitoring in 1998 and 2006.
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. Not all Section 303(d) impairments identified for the 2006 assessment/listing cycle and the current (2008) assessment/listing cycle (indicator bacteria), however, are addressed in the TMDL. Thus, this waterbody remains in Category 5a (impaired; TMDL required) for the 2008 assessment/listing cycle.
EXPLANATION: Results of IDNR-UHL beach monitoring from 2004 through 2006 suggest that the Class A1 uses are "not 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 2004 (14 samples), 2005 (12 samples), and 2006 (27 samples) as part of the IDNR-UHL 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) all thirty-day geometric means for 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 5-sample, 30-day 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).
At Lake of Three Fires beach, the geometric means of 13 thirty-day periods during the summer recreation seasons of 2004, 2005 and 2006 exceeded the Iowa water quality standard of 126 E. coli orgs/100 ml: 8 of 10 geometric means violated in 2004, 0 of 8 geometric means violated in 2005, and 5 of 23 geometric means violated in 2006. Also, the percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was significantly greater than 10% in the 2004 recreation season (29%). The percentages of samples exceeding Iowa’s single-sample maximum criterion in 2005 (17%) and 2006 (11%) were not significantly greater than 10% and therefore do not suggest impairment of the Class A1 uses. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest impairment (nonsupport) of the Class A1 (primary contact recreation) 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 suggest that the Class A1 (primary contact recreation) uses for Lake of Three Fires be assessed (monitored) as “partially supported” for the 2008 reporting cycle. Using the median values from these surveys from 2002 through 2006 (approximately 18 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 64, 63, and 68 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. While these values show improvement over the 2006 listing/assessment cycle (Secchi depth TSI 69, chlorophyll a TSI 64, total phosphorus TSI 73), the TSI scores from the 2008 listing/assessment cycle are not sufficiently less than 65 to propose delisting of this lake. The 2008 values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and high levels of phosphorus in the water column.
Based on data from the ISU and UHL surveys in 2002 through 2006, the median concentration of inorganic suspended solids was 6.0 mg/L, which was the 46th highest concentration of the 132 lakes monitored by these programs. These moderately high levels suggest potential problems related to in-lake turbidity.
Data from the 2002-2006 ISU and UHL surveys suggest a large population of cyanobacteria exists at Lake of Three Fires, which contributes to impairment at this lake. These data show that cyanobacteria comprised 98% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (80.7 mg/L) was also the 12th highest of the 132 lakes sampled. This median is in the worst 25% of the 132 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 2002-2006. 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.” 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 algal and non-algal turbidity remain concerns at this lake.
Results from the ISU and UHL lake surveys and physical/chemical monitoring associated with the IDNR-UHL beach monitoring program show good chemical water quality at Lake of Three Fires. The ISU and UHL lake surveys data from 2002-2006 show no violations of the Class B(LW) criteria for ammonia in 11 samples and only one violation of the Class B(LW) criterion for pH in 18 samples. The data show 2 violations of the criterion for dissolved oxygen in 18 samples (11%). 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. Results of physical/chemical monitoring as part of IDNR’s beach monitoring program also suggest good water quality at Lake of Three Fires. Data from the beach monitoring program from 2004 through 2006 show 4 violations of the Class B(LW) criterion for dissolved oxygen in 51 samples. These violations are less than 10% of the samples and therefore do not constitute an impairment of the Class B(LW) uses of Lake of Three Fires. The pH data from the beach monitoring program (2004-2006) show 8 violations of Iowa’s criterion for pH in 51 samples (13%). These violations are not significantly greater than 10% of the samples and therefore suggest full support of the Class B(LW) uses of Lake of Three Fires.
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 2002-06 show that nitrate levels are very low at this lake (maximum value = 3.0 mg/l; median = 0.1 mg/l in 17 samples) 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. Thus, follow-up monitoring will be conducted in 2008 to better determine whether a one-meal-per-week consumption advisory needs to be issued.
