Project Construction

One of the greatest water quality challenges facing the lake is the physical impact of the accumulated sediment load. Bathymetry indicates peat and muck up to 10 feet deep in some areas of the lake, leaving an average water depth of only 3 feet. Drawdowns to consolidate the material are not substantially effective due to the stormwater runoff through the creek system, the irregular sediment loading throughout the lake and the poor quality of the material itself. The sediment load in the system is considered to be partly responsible for the loss of Lake Henrietta approximately one mile upstream of Lake Munson. The effects of just the past 45 years of sediment transport can be readily identified in the 30-acre delta which has blossomed in the headwaters to Lake Munson. The sediment delta was sampled to determine handling requirements during the lake restoration effort. Approximately 10 percent of the material is man made floatables, such as Styrofoam cups, lumber, packing crates, white goods, and tires. An additional 5 percent is vegetative debris such as trees and limbs. The sediments throughout the current project area were tested for Total Petroleum Hydrocarbons (TPH) and the USEPA priority pollutant metals. In addition, the two samples with the highest concentrations of "total" metals and TPH were tested for toxicity characterization leaching potential (TCLP) to determine if the constituents in the sediment were leachable, and possibly require special handling and disposal of the sediments. The sediment does contain petroleum byproducts and pesticides above the detectable limit; however, the TCLP tests verified that the materials do not merit a hazardous classification. The sediments are extremely high in nutrients, creating a tremendous oxygen load on the water system while supporting a stellar growth in exotic and nuisance species. The extensive growth of hydrilla and other exotic species has rendered the lake virtually inaccessible by motorized boats. Efforts to contain the exotics have included the introduction of grass carp with limited success. Removal of the underlying nutrient-laden sediment layer is considered to be crucial to the success of the aquatic weed control program. The construction at Lake Henrietta and Munson Slough is scheduled for two years, from November 1999 to November 2001. The in-lake restoration will be a separate project. The design is expected to focus on sediment removal for water quality improvement, in addition to considering wetland and upland habitat requirements and public recreation. The Florida Fish and Wildlife Conservation Commission (FFWCC) staff expressed a strong commitment to provide major funding to complete this portion of the project. Given competing priorities for County funding and staff time, it is expected that the FFWCC will be the primary agency to implement the in-lake restoration.