Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results from the IDNR-county voluntary beach monitoring program in 2004 and 2005.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to aesthetically objectionable conditions caused by poor water transparency. Violations of the pH criterion also contribute to impairment of the Class A1 uses at this lake. The Class B(LW) (aquatic life) uses are assessed (monitored) as “partially supported” due to violations of the Class B(LW) criterion for pH. Fish consumption uses remain “not assessed.” Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results from the IDNR-county voluntary beach monitoring program in 2004 and 2005.
EXPLANATION: Results of IDNR county beach monitoring from 2004 and 2005 suggest that the Class A1 uses are assessed (evaluated) as "fully supported." Levels of indicator bacteria at Cold Springs Lake beach were monitored sporadically during the primary contact recreation seasons (May through August) of 2004 (10 samples) and 2005 (2 samples) as part of the IDNR county beach monitoring program. Because limited data were collected in only two years of sampling, the assessment is considered “evaluated” (lower confidence) as opposed to “monitored” (higher confidence). 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 Cold Springs Lake beach, the geometric means of all 6 thirty-day period during the summer recreation season of 2004 were below the Iowa water quality standard of 126 E. coli orgs/100 ml. The percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was less than 10% in 2004 (0%). One of the two samples in 2005 exceeded the single-sample maxiumum criterion, however, based on IDNR’s assessment methodology this violation is not significantly greater than 10% of the samples. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest “full support” (evaluated) of the Class A1 (primary contact recreation) uses.
For the 2008 reporting cycle, the Class A1 (primary contact recreation) uses for Cold Springs Lake are assessed as “partially supported” due to poor water transparency and violations of the state’s pH criterion. Using the median values from the ISU lake survey and the UHL ambient lake monitoring program from 2002 through 2006 (approximately 20 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 68, 62, and 63 respectively for Cold Springs Lake. According to Carlson (1977) the index values for Secchi depth, chlorophyll a, and total phosphorus all place Cold Springs Lake in between the eutrophic and hypereutrophic categories. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, poor water transparency, and moderately high levels of phosphorus in the water column.
The levels of inorganic suspended solids at this lake were moderately high and suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Cold Springs Lake (4.8 mg/L) was the 57th highest median of the 132 lakes sampled by the ISU and UHL surveys.
Data from the 2002-2006 ISU and UHL surveys suggest that a small population of cyanobacteria exists at Cold Springs Lake that does not indicate an impairment to the Class A1 uses of the lake. These data show that cyanobacteria comprised 62% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (5.5 mg/L) was also the 21st lowest of the 132 lakes sampled.
The Class B(LW) (aquatic life) uses for Cold Springs Lake are assessed (monitored) as “partially supported” due to violations of Iowa’s Class A1,B(LW) criterion for pH. The ISU and UHL lake surveys data from 2002-2006 show no violations of the Class B(LW) criterion for ammonia in 13 samples, or dissolved oxygen in 20 samples. The data for pH, however, show 3 violations of the Class B(LW) criterion for pH in 20 samples. Based on IDNR’s assessment methodology, these violations are not significantly greater than 10% and therefore do not constitute an impairment of the Class A1 or Class B(LW) uses of Cold Springs Lake. However, data from the 2006 assessment cycle showed significant violations of the pH criterion; therefore Cold Springs Lake will remain assessed as “partially supported” due to these continued violations. Based on IDNR’s assessment methodology 2 consecutive assessment/listing cycles without significantly greater than 10% of the samples violating the criterion are necessary to propose delisting based on pH violations. These violations likely reflect the high levels of primary productivity at Cold Springs Lake and do not reflect the input of pollutants into this lake.
Note: In 2006 Cold Springs Lake was drawn down and the fishery was renovated to eliminate problematic crappie and grass carp populations. At this time, aquatic vegetation was also planted in the lake bed. These activities will likely lead to improved water quality in this lake in the future.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.
