Assessment Comments
Assessment is based on: (1) the results of the IDNR-UHL beach monitoring program in summers of 2006, 2007, and 2008, (2) results of the statewide survey of Iowa lakes conducted from 2004 through 2007 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted from 2005 through 2008 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, (5) results of a fish kill investigation in April 2009, and (6) 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. The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to high levels of nutrients that contribute to nuisance algae blooms and results of a fish kill investigation in April 2009. 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 2006, 2007, and 2008, (2) results of the statewide survey of Iowa lakes conducted from 2004 through 2007 by Iowa State University (ISU), (3) results of the statewide ambient lake monitoring program conducted from 2005 through 2008 by University Hygienic Laboratory (UHL), (4) information from the IDNR Fisheries Bureau, (5) results of a fish kill investigation in April 2009, and (6) 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 2010 assessment/listing cycle.
EXPLANATION: Results of IDNR beach monitoring from 2006 through 2008 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 2006 (28 samples), 2007 (18 samples), and 2008 (24 samples) as part of the IDNR beach monitoring program. According to IDNR’s assessment methodology, all thirty-day geometric means for the three-year assessment period must be less than the state’s geometric mean criterion of 126 E. coli orgs/100 ml for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses. 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”. 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 8 thirty-day periods during the summer recreation seasons of 2006, 2007 and 2008 exceeded the Iowa water quality standard of 126 E. coli orgs/100 ml: 2 of 24 geometric means violated in 2006, 2 of 14 geometric means violated in 2007, and 4 of 20 geometric means violated in 2008. The percentage of samples exceeding Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) was 11% in 2006, 33% in 2007 and 25% in 2008. According to IDNR’s assessment methodology and U.S. EPA guidelines, the exceedences of the geometric mean criterion suggest impairment (nonsupport) of the Class A1 (primary contact recreation) uses.
For the 2010 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 to aesthetically objectionable conditions caused by nuisance algae blooms. Using the median values from these surveys from 2004 through 2008 (approximately 25 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 66, 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 5.6 mg/L, which was the 46th highest of the 132 monitored lakes.
Data from the 2004-2008 ISU and UHL surveys suggest a moderately large population of cyanobacteria exists at Lower Pine Lake, which contributes to the aesthetically objectionable conditions at this lake. These data show that cyanobacteria comprised 53% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (12.5 mg/L) was also the 56th lowest of the 132 lakes sampled.
The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to a fish kill that occurred in April of 2009. The fish kill was attributed to natural causes (fluctuating water temperatures). The 2009 kill affected approximately 2500 fish; mostly bluegill and crappie. No estimate of the value of these fish was made. According to IDNR’s assessment/listing methodology, 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 (2006-2009) 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.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.
Information from the IDNR Fisheries Bureau also suggests that the Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to nutrient loading that leads to nuisance algae blooms. Information from the IDNR Fisheries Bureau suggests that this lake has no submergent vegetation and a moderate common carp population that leads to occasional algae blooms. Overall, Results of the ISU and UHL lake surveys from 2004 through 2008 show good chemical water quality at Lower Pine Lake. These data show no violations of the Class B(WW-1) criterion for ammonia in 24 samples, and no violations of the Class B(WW-1) criterion for dissolved oxygen in 25 samples. The pH data show 1 violation of the Class A1,B(WW-1) criterion for pH in 25 samples (4%). Based on IDNR’s assessment methodology this violation is less than 10% of the samples and therefore does not suggest impairment of the Class B(WW-1) uses of Lower Pine Lake. However, Lower Pine Lake was impaired for high levels of pH for the 2008 assessment/listing cycle. Based on IDNR's assessment methodology, two assessment/listing cycles with less than 10% of samples below the water quality standard are needed to propose de-listing of the impairment. Therefore, pH will remain an impairment for the 2010 assessment/listing cycle.
Fish consumption uses were assessed (evaluated) 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. Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). 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.
