Cold Springs Lake IA 05-NSH-1420

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 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 “fully supported."  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 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 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 2014 reporting cycle, the Class A1 (primary contact recreation) uses for Cold Springs Lake are assessed as “fully supported.” Using the median values from the ISU lake survey and the UHL ambient lake monitoring program from 2008-2012(approximately 14 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 54, 59, 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 low levels of chlorophyll a and suspended algae in the water, relatively good water transparency, and relatively low levels of phosphorus in the water column.  
Note: Cold Springs Lake was assessed as “partially supporting” in the 2010 assessment/listing cycle due to violation for Secchi transparency.   Based on IDNR’s assessment methodology 2 consecutive assessment/listing cycles with index values at or below 63 are necessary to propose delisting based on non-algal turbidity violations.   Because the index values for secchi depth were below 63 for the 2012 assessment/listing cycle or the current (2014) assessment/listing cycle, the turbidty impairment for Cold Springs Lake is suggested for delisting.  

The levels of inorganic suspended solids at this lake were moderately high but do not suggest an impairment at this lake.   The median level of inorganic suspended solids in Cold Springs Lake (2.8 mg/L) was and ranked 52nd of the 134 lakes sampled by the ISU and UHL surveys.

Data from the 2008-2012 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 73% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (14.5 mg/L) and ranked 46th 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 2008-2012 show no violations of the Class B(LW) criterion for ammonia in 14 samples, or dissolved oxygen in 14 samples.   The data for pH show 1 violation of the Class B(LW) criterion for pH in 14 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 were assessed (monitored) as “fully supported, threatened” based on results of U.S.   EPA/IDNR fish contaminant (RAFT) monitoring at Cold Springs Lake in 2012.    The composite samples of fillets from largemouth bass and channel catfish had moderate levels of contaminants.    Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.457 ppm.  This composite value is above the 1 meal/week advisory threshold.  The levels of mercury generated from this monitoring data are sufficiently high for concern and to justify follow-up monitoring.  According to IDNR's assessment methodology, the single occurrance of a contaminant above the advisory trigger level neither warrants issuance of an advisory not indicated impairment of the fish consumption uses: two consecutive sampoings that show contaminant levels above the trigger level are needed to justify impairment.  Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0507 ppm; total PCBs: 0.09 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 the degree to which Iowa’s lakes and rivers support their fish consumption uses.     The fish contaminant data generated from the 2012 RAFT sampling conducted at this Cold Springs Lake show that the levels of contaminants do not yet warrant an advisory.  Follow up monitoring is needed to determine if an advisory should be issued.