Trumbull Lake IA 06-LSR-1636

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Trumbull Lake  are assessed (monitored) as "not supported" due to poor water transparency, aesthetically objectionable conditions caused by algae blooms based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 9 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 83, 73, and 81 respectively for Trumbull Lake . According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Trumbull Lake  in the Hypereutrophic category. These values suggest very high levels of chlorophyll a and suspended algae in the water, extremely poor water transparency, and extremely high levels of phosphorus in the water column. The data show one violation of the Class A1 criterion for pH in 9 samples.

Note: A TMDL for algae and turbidity at Trumbull Lake was prepared by IDNR and approved by EPA in 2006.   Because all Section 303(d) impairments identified for the 2014 assessment/listing cycle (algal growth and turbidity) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved) for the 2016 cycle.  

The level of inorganic suspended solids was extremely high at Trumbull Lake , and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Trumbull Lake  (23.5 mg/L) was ranked 134th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a large population of cyanobacteria exists at Trumbull Lake , which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 90% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (122.8 mg/L) was ranked 133rd of the 138 lakes sampled. This median is in the worst 25% of the 138 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 2010-2014. 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. 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(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to excessive nutrient loading to the water column, nuisance blooms of algae, and re-suspension of sediment.   This potential impairment is not appropriate for Iowa’s Section 303(d) list of impaired waters (Integrated Report Category 5) but is appropriate for IR Category 3b of Iowa’s Integrated Report and Iowa’s list of waters in need of further investigation. Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 9 samples(0%), no violations of the criterion for dissolved oxygen in 9 samples(0%), and one violation of the criterion for pH in 9 samples(11%).Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest impairment (fully supported/monitored) of the Class B(LW) uses of Trumbull Lake .

The level of support of the Class HH-fish consumption uses is changed from “fully supporting” to “not assessed” due to the age of the data upon which the previous assessment was based.  The previous assessment was based on results of U.S. EPA / IDNR fish tissue (RAFT) monitoring at Trumbull Lake in 2003.   The composite samples of fillets from common carp and yellow perch had low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp 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 yellow perch fillets were as follows: mercury: 0.021 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.   Overall the fish contaminant data generated from the 2003 RAFT sampling conducted at Trumbull Lake shows 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.

Note: The lake was drawn down in 2012 and rough fish were removed throughout the wetland complex and water control structures were installed to help regulate water levels in the wetland complex and at Trumbull Lake. The lake was refilled in 2014. Dramatic water quality improvements were noted.