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 of a fish kill investigation in May 2007.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to poor water transparency and algal blooms that violate the state’s narrative criteria protecting against aesthetically objectionable conditions. The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported" based on the results of a fish kill investigation in May 2007 and information from the IDNR Fisheries Bureau. Fish consumption uses are "not assessed" due to a lack of recent information upon which to base an assessment. 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 of a fish kill investigation in May 2007.
Note: A TMDL for siltation and nutrients at Badger Creek Lake was prepared by IDNR and approved by EPA in 2003. Because all Section 303(d) impairments identified for the 2012 assessment/listing cycle (algal growth [inlcuding nuisance growth of cyanobacteria]) are addressed by the TMDL, this waterbody remains in IR Category 4a (TMDL approved).
EXPLANATION: For the 2012 reporting cycle, the Class A1 (primary contact recreation) uses for Badger Creek Lake are assessed as “partially supported” based on results from the ISU statewide survey of lakes and the UHL ambient lake monitoring program. Using the median values from these surveys from 2006 through 2010 (approximately 17 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 67, 69, and 75 respectively for Badger Creek Lake. According to Carlson (1977) the Secchi depth and chlorophyll a values place Badger Creek Lake in between the eutrophic and hypereutrophic categories and the total phosphorus value places Badger Creek Lake in the hypereutrophic category. These values suggest high levels of chlorophyll a and suspended algae in the water, poor water transparency, and very high levels of phosphorus in the water column.
The levels of inorganic suspended solids at this lake were high and suggest that high levels of non-algal turbidity may contribute to the poor water clarity at this lake. The median level of inorganic suspended solids in Badger Creek Lake (6.0 mg/L) was the 44th highest median for all the 134 lakes sampled by ISU and UHL.
Data from the 2006-2010 ISU and UHL surveys suggest a large population of cyanobacteria exists at Badger Creek Lake, which contributes to the impairment at this lake. These data show that cyanobacteria comprised 78% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (34.2 mg/L) was the 41st highest of the 134 lakes sampled.
The Class B(LW) (aquatic life) uses for Badger Creek Lake are assessed (evaluated) as “partially supported” based on information from the IDNR Fisheries Bureau, and results of a fish kill investigation. Information from the IDNR Fisheries Bureau suggests that algal blooms and water clarity remain problems at this lake that affect the both the quality of the fish population and the likelihood of anglers using the lake. In addition, sediment resuspension, a lack of aquatic vegetation, and shoreline erosion are also problems at this lake.
A fish kill that occurred in this lake on or before May 17, 2007 also suggests "impairment" of the Class B(LW) uses. The kill was identified as a natural kill related to spawning stress. Monitoring of the lake showed that the pH was high (9.2) and there was a large amount of brown algae in the lake. The total number of fish killed was estimated to be 1000. This is the same assessment as that developed for the 2010 assessment/listing cycle. The continuance of the IR Category 2b listing is based on IDNR's 2012 assessment methodology that states the following: the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2009-2011) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation. Thus, this assessment segment will remain in Category 2b of Iowa’s 2012 Integrated Report.
The ISU and UHL lake surveys data from 2006-2010 show no violations of the Class B(LW) criterion for ammonia in 17 samples. The data show 3 violations of the Class B(LW) criterion for dissolved oxygen in 17 samples. Based on IDNR’s methodology these violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class B(LW) uses of Badger Creek Lake. The data also show 1 of 17 samples violated the Class A1,B(LW) criterion for pH (20%). These violations are not significantly greater than 10% of the samples and therefore does not suggest impairment of the Class A, and B(LW) uses of the lake. In the 2008 assessment/listing cycle, Badger Creek Lake was assessed as "partially supporting" due to significant violations of the pH criteria. According to 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. Because violations of the pH criteria were not significantly greater than 10% of the samples for both the 2010 and the current 2012 assessment/listing cycles, the pH impairment at Badger Creek Lake is suggested for delisting. The pH violations at Badger Creek Lake likely reflect the excessive primary productivity at the lake and do not reflect the input of pollutants into this lake.
Fish consumption uses were “not assessed” due to a lack of recent fish contaminant monitoring at this lake. The most recent fish tissue monitoring was conducted in 1999. While these results suggest that levels of contaminants were low at Badger Creek Lake, they are now too old (greater than 10 years) to be used for an assessment.
