Assessment Comments
Assessment is based on: (1) the results of the IDNR-UHL beach monitoring program in summers of 2004, 2005, and 2006, (2) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) results of U.S. EPA/IDNR fish tissue monitoring in 2003.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to high levels of indicator bacteria that exceed Iowa’s water quality standards, and aesthetically objectionable conditions caused by algae blooms. Violations of the Class A1 criterion for pH also contribute to the impairment. The Class B(WW-1) (aquatic life) uses are assessed (monitored) as “partially supported” due to violations of the Class B(WW-1) criterion for pH and high levels of nutrients that contribute to nuisance algae blooms. Fish consumption uses remain assessed (monitored) as “fully supported.” Sources of data for this assessment include (1) the results of the IDNR-UHL beach monitoring program in summers of 2004, 2005, and 2006, (2) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, and (5) results of U.S. EPA/IDNR fish tissue monitoring in 2003.
Note: A TMDL for organic enrichment at Lower Pine Lake 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. Because the Section 303(d) impairment due to indicator bacteria (aka, "pathogens") was not addressed in the TMDL, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle and remains in Category 5a for the 2008 assessment/listing cycle.
EXPLANATION: Results of IDNR beach monitoring from 2004 through 2006 suggest that the Class A1 uses are "not supported." Levels of indicator bacteria at Pine Lake beach were monitored once per week during the primary contact recreation seasons (May through September) of 2004 (22 samples), 2005 (23 samples), and 2006 (28 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 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 Pine Lake beach, the geometric means of 10 thirty-day periods during the summer recreation seasons of 2004, 2005 and 2006 exceeded the Iowa water quality standard of 126 E. coli orgs/100 ml: 2 of 18 geometric means violated in 2004, 6 of 19 geometric means violated in 2005, and 2 of 24 geometric means violated in 2006. Also, the percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was greater than 10% in the following recreation seasons: 2004: 14%, 2005: 35%, 2006: 11%. The results from 2005 do suggest that significantly more than 10% of samples exceed the single-sample maximum criterion. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest impairment (nonsupport) of the Class A1 (primary contact recreation) uses.
For the 2008 assessment/listing cycle, results from the ISU and UHL lake surveys indicate that the Class A1 (primary contact recreation) uses of Lower Pine Lake are assessed “not supported” due aesthetically objectionable conditions caused by nuisance algae blooms, and violations of the Class A1 criterion for pH. Using the median values from these surveys from 2002 through 2006 (approximately 23 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 65, 73, and 71 respectively for Lower Pine Lake. According to Carlson (1977) the Secchi depth score places Lower Pine Lake in between the eutrophic and hypereutrophic categories, while the chlorophyll a and total phosphorus scores place Lower Pine Lake in the hypereutrophic category. These values suggest very high levels of chlorophyll a and suspended algae in the water, poor water transparency, and very high levels of phosphorus in the water column.
Based on data from the ISU and UHL lake surveys, the level of inorganic suspended solids was only moderately high at this lake and does not suggest an impairment based on non-algal turbidity. The median inorganic suspended solids concentration at Lower Pine Lake was 6.3 mg/L, which was the 42nd highest of the 132 monitored lakes.
Data from the 2002-2006 ISU and UHL surveys suggest a large population of cyanobacteria exists at Lower Pine Lake, which contributes to impairment at this lake. These data show that cyanobacteria comprised 94% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (39.7 mg/L) was also the 31st highest of the 132 lakes sampled. This median is in the worst 25% of the 132 lakes sampled. The presence of a large population of cyanobacteria at this lake suggests a potential violation of Iowa’s narrative water quality standard protecting against the occurrence of nuisance aquatic life. This assessment is based strictly on the distribution of the lake-specific median cyanobacteria values from 2002-2006. Median levels greater than the 75th percentile of this distribution were arbitrarily considered to represent potential impairment. No other criteria exist, however, upon which to base a more accurate identification of impairments due to cyanobacteria. The assessment category for assessments based on level of cyanobacteria will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence) to account for this lower level of confidence.
The Class B(WW-1) (aquatic life) uses are assessed (monitored) as “partially supported” due violations of the Class B(WW-1) criterion for pH and nutrient loading that leads to nuisance algae blooms. Overall, Results of the ISU and UHL lake surveys from 2002 through 2006 show good chemical water quality at Lower Pine Lake. These data show no violations of the Class B(WW-1) criterion for ammonia in 16 samples, and no violations of the Class B(WW-1) criterion for dissolved oxygen in 23 samples. The pH data show 2 violations of the Class A1,B(WW-1) criterion for pH in 23 samples (10%). Based on IDNR’s assessment methodology these violations are less than 10% of the samples and therefore do not suggest impairment of the Class B(WW-1) uses of Lower Pine Lake. Results of physical/chemical monitoring associated with the IDNR-UHL beach monitoring program show similar results for dissolved oxygen (no violations in 69 samples), but show 17 violations of the Class B(WW-1) criterion for pH in 69 samples (25%). Based on IDNR’s assessment methodology these violations are significantly greater than 10% of the samples and therefore suggest impairment (partial support/monitored) of the Class B(WW-1) uses at Lower Pine Lake. The violations of the pH criterion likely reflect primary productivity at Lower Pine Lake and do not reflect the input of pollutants into this lake.
Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring at Lower Pine Lake in 2003. 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: <0.0181 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.048 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 2003 RAFT sampling conducted at Lower Pine Lake show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
