Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 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. The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.” Fish consumption uses remain “not assessed.” Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 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 2012 reporting cycle, the Class A1 (primary contact recreation) uses for Cold Springs Lake are assessed as “partially supported” due to poor water transparency that violates Iowa's narrative criteria protecting against aesthetically objectionable conditions. Using the median values from the ISU lake survey and the UHL ambient lake monitoring program from 2006 through 2010 (approximately 16 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 54, 58, and 60 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 the eutrophic category. These values suggest relatively low levels of chlorophyll a and suspended algae in the water, very good water transparency, and relatively low levels of phosphorus in the water column. While these results suggest "full support" of the Class A1 (primary contact recreation) uses, Cold Springs Lake was assessed as "impaired" for the 2010 assessment/listing cycle. Based on IDNR's methodology, two consecutive assessment/listing cycles with chlorophyll a and Secchi depth TSI values below 63 are necessary to suggest de-listing of the impairment. Therefore, Cold Springs Lake remains assessed (monitored) as "partially supported."
The levels of inorganic suspended solids at this lake were relatively low and do not suggest that non-algal turbidity contributes to an impairment at this lake. The median level of inorganic suspended solids in Cold Springs Lake (2.5 mg/L) was the 48th lowest median of the 134 lakes sampled by the ISU and UHL surveys.
Data from the 2006-2010 ISU and UHL surveys suggest that a relatively 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 81% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (10.9 mg/L) was the 29th lowest of the 134 lakes sampled.
The Class B(LW) (aquatic life) uses for Cold Springs Lake are assessed (monitored) as “fully supported” based on information from the IDNR Fisheries Bureau and results of the ISU and UHL lake surveys. The ISU and UHL lake surveys data from 2006-2010 show no violations of the Class B(LW) criterion for ammonia in 16 samples, or dissolved oxygen in 16 samples. The data for pH show 1 violation of the Class B(LW) criterion for pH in 16 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.
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 continued improved water quality in this lake in the future. Information from the IDNR Fisheries Bureau suggests that these improvements have improved turbidity, but filamentous algae remains a concern at this lake.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.
