Assessment Comments
Assessment based on (1) surveys by IDNR Fisheries Bureau, (2) results of the ISU lake survey from 2000-04, (3) results from the IDNR beach monitoring program from 2002 through 2004, (4) ISU reports on lake plankton communities from 2000-05, and (5) U.S. EPA / IDNR fish tissue monitoring in July 1998.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "not supported" due levels of indicator bacteria (E. coli) at this lake’s beach that exceed state criteria. This is a new impairment for this lake. An additional impairment of the Class A uses is due to poor water transparency caused by high levels of inorganic suspended solids. Also, very large populations of bluegreen algae present a potential impairment of these uses. The Class B(LW) aquatic life uses remain assessed (evaluated) as "partially supported" due to high levels of nutrients, siltation, and turbidity (algal and non-algal). A lake restoration project began at this lake in 2004, and water quality conditions will likely improve following completion of this project. The Class C (drinking water) uses remain "not assessed" due to the lack of data upon which to base an assessment. Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 1998. The sources of data for this assessment include (1) the results of the IDNR-UHL beach monitoring program in summers of 2002, 2003, and 2004, (2) results of the statewide survey of Iowa lakes conducted from 2000 through 2004 by Iowa State University (ISU), (3) information from the IDNR Fisheries Bureau, (4) information on plankton communities collected from 2000 through 2005 for the ISU lakes survey, and (5) results of U.S. EPA / IDNR fish tissue monitoring in 1998.
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 current (2006) assessment/listing cycle (indicator bacteria), however, are addressed in the TMDL. Thus, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle.
EXPLANATION: Results of IDNR beach monitoring at Lake of Three Fires from 2002 through 2004 suggest that the Class A uses are "not supported." Levels of indicator bacteria were monitored once per week during the primary contact recreation seasons (May through September) of 2002 (30 samples), 2003 (28 samples), and 2004 (14 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 A (primary contact recreation) uses: (1) all five-sample, 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 A uses should be assessed as “not supported”. Also, if 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 A uses should be assessed as “partially supported”. This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35of U.S. EPA 1997b).
At Lake of Three Fires beach, the geometric means of 9 thirty-day periods during the summer recreation seasons of 2002, 2003 and 2004 exceeded the Iowa water quality standard of 126 E. coli orgs/100 ml: 1 of 24 geometric means violated in 2003, 8 of 10 geometric means violated in 2004. None of the 26 geometric means for the 2002 recreational season exceeded this standard. Also, the percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was greater than 10% in the 2004 recreation season (29%). No more than 10% of the samples exceeded this standard during the recreational seasons of 2002 (10%) and 2003 (4%). According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest impairment (nonsupport) of the Class A (primary contact recreation) uses.
Results from the ISU statewide survey of Iowa lakes also suggest impairment of the Class A uses at this lake. The results from this survey show high levels of algal and non-algal turbidity suggesting that the Class A (primary contact recreation) uses of Lake of Three Fires should be assessed as “partially supported”. Using the median values from this survey from 2000 through 2004 (approximately 15 samples), Carlson's (1977) trophic state indices for total phosphorus, chlorophyll-a, and secchi depth are 73, 64, and 69, respectively. According to Carlson (1977), the index value for total phosphorus places this lake in the range of hyper-eutrophic lakes; the index values for chlorophyll-a and secchi depth place this lake in the middle and upper range, respectively, between eutrophic and hyper-eutrophic lakes. These index values suggest very high levels of phosphorus in the water column, moderately high levels of chlorophyll-a (suspended algae), and moderately poor to very poor water transparency.
According to Carlson (1991), the occurrence of a high TSI values for total phosphorus and secchi depth, with a relatively low value for chlorophyll-a, suggests that non-algal turbidity limits production of algae. The results of ISU monitoring at this lake are consistent with this pattern. The very high level of inorganic suspended solids at this lake suggests the potential for (1) limitation of algal production and (2) contributions to in-lake turbidity. The median level of inorganic suspended solids (ISS) in the 131 lakes sampled for the ISU lake survey from 2000 through 2004 was 5.2 mg/l. The median ISS value at Lake of Three Fires was 10.3 mg/l; this values is the 29th highest of the 131 lakes sampled. The ISS level at this lake suggests that non-algal turbidity both limits the production of algae and contributes to the turbidity-related impairment of the designated Class A uses.
Other non-phosphorus limitations (e.g., low TN:TP ratio and zooplankton grazers) may also limit algal production at Lake of Three Fires. Based on median values from ISU sampling from 2000 through 2004, the ratio of total nitrogen to total phosphorus for Lake of Three Fires is 10. This TN:TP ratio suggest that algal production at this may, at times, be limited by nitrogen availability.
In terms of all Iowa lakes sampled, data from the ISU survey show relatively small populations of zooplankton species at this lake that graze on algae. Although sampling from 2000 through 2005 showed that Cladoceran taxa (e.g., Daphnia) comprised about 45% of the dry mass of the zooplankton community of this lake, the average per summer sample mass of Cladoceran taxa over the 2000-2005 period (49 mg/l) was the 31st lowest of the 131 lakes sampled. These results suggest little if any non-phosphorus limitation due to zooplankton grazing at Lake of Three Fires.
Thus, these conditions indicate impairments to the Class A (primary contact) uses due to poor water transparency that violates Iowa’s narrative water quality criterion protecting against aesthetically objectionable conditions. The cause of the poor water transparency is primarily high levels of inorganic suspended solids, although levels of planktonic algae (as measured by chlorophyll-a) are approaching the impairment threshold.
The presence of nuisance (=noxious) algal species (i.e., bluegreen algae) may also present an impairment of the Class A uses at Lake of Three Fires. Data from the ISU survey from 2000 through 2004 suggest that bluegreen algae (Cyanophyta) comprise a significant portion of this lake’s summertime phytoplankton community. Summer sampling during this period showed the percent wet mass of the total phytoplankton community in bluegreens (cyanobacteria) was approximately 65%. Also, the median per summer sample mass of bluegreen algae at this lake (42 mg/l) was the 20th highest of the 131 lakes sampled. This median is in the worst 25% of the 131 Iowa lakes sampled. The presence of a large population of bluegreen algae at this lake suggests the potential violation of Iowa’s narrative water quality standard protecting against occurrence of nuisance aquatic life. This assessment, however, is based strictly on a distribution of the lake-specific median bluegreen algae values for the 2000-2004 monitoring period. Median levels greater than the 75th percentile of this distribution (~29 mg/l) were arbitrarily chosen by IDNR staff to represent the condition of “potential impairment: partially supported.” No criteria exist, however, upon which to base a more accurate identification of impairments due to bluegreen algae. Thus, while the ability to characterize the levels of bluegreen algae at this lake has improved over that of the previous (2004) assessment due to collection of additional data, the assessment category for assessments based on level of bluegreen algae nonetheless remains, of necessity, "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
The water quality conditions at this lake, along with information from the IDNR Fisheries Bureau, suggest that the Class B(LW) aquatic life uses should remain assessed (evaluated) as "partially supported" due to siltation, excessive nutrient loading to the water column, and moderately high levels of algal and non-algal turbidity. The ISU lake survey data show generally good chemical water quality at this lake. Results of this monitoring show that only 1 of the 13 samples collected exceeded the Class B(LW) criteria for dissolved oxygen and that 3 of the 13 samples collected exceeded Iowa’s Class A,B(LW) criteria for pH (maximum = 9.4; minimum = 7.7 pH units). Based on IDNR’s assessment methodology, these results do not suggest violation frequencies are significantly greater than 10% for either parameter and thus do not suggest impairment of either the Class A and Class B(LW) uses of Lake of Three Fires.
In April 2004, a lake dredging project began that will increase the average depth by approximately four feet and the maximum depth by eight feet. After dredging is complete, the lake will be drained to remove the common carp and gizzard shad that have degraded the quality of the fishery of this lake; the lake will be re-stocked with largemouth bass, channel catfish, and bluegill in fall, 2004. Prior to re-filling of the lake, the shoreline will be stabilized with rock and fish habitat will be placed in the lake bed. This project will likely lead to improvements in water quality at 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 lake survey relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU survey from 2000-04 show that nitrate levels are very low at this lake (maximum value = 2.1 mg/l; median = 0.4 mg/l in 13 samples), these data are not sufficient for developing a valid assessment of support of the Class C uses.
Fish consumption uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Lake of Three Fires in 1998 Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). The composite samples of fillets from channel catfish and largemouth bass had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 086 ppm; total PCBs: <0.08 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.235 ppm; total PCBs: <0.08 ppm; and technical chlordane: <0.03 ppm. 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. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. Although this scenario does not apply to the fish contaminant data generated from the 1998 RAFT sampling conducted at Lake of Three Fires, levels of contaminants are sufficiently high for concern and justify follow-up monitoring.
While results from the 1998 sampling show that levels of chlordane and PCBs are well below levels of concern, the level of mercury in the sample of largemouth bass fillets exceeds the 1 meal/week trigger level as defined in Iowa’s revised (2006) fish consumption advisory protocol. 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 river segment. Thus, follow-up monitoring will be conducted in 2006 to better determine (1) levels of mercury in the edible portions (fillets) of fish in this river segment and (2) whether a one-meal-per-week consumption advisory needs to be issued.
