In 1996, Lake Trafford suffered an extensive fish kill due to low dissolved oxygen levels in the lake.  Studies were undertaken by the Florida Fish and Wildlife Commission to determine the cause of the low dissolved oxygen.  The study results indicated that the accumulation of a thick layer of decomposing organic matter on the bottom of the shallow lake containing a high level of total phosphorous was the cause of the low dissolved oxygen levels and the incident fish kills.

A program was recommended by the Florida Fish and Wildlife Commission and supported by the Big Cypress Basin of the South Florida Water Management District for the restoration of Lake Trafford by removing the contaminated sediment from the lake. ART Engineering was contracted to perform sediment mapping using Ground Penetrating Radar (GPR) at Lake Trafford. Objectives of the survey were to 1) map contaminated sediment, 2) to establish reference elevations for “Top of Muck” and “Top of Original Lake Bottom” and 3) calculate the volume of sediment to be removed by dredging.

Fieldwork

To validate and calibrate the radar results before surveying the entire lake, measurements were taken along two transect lines established in Lake Trafford. The radar data (measured time values) were calibrated to elevation of marl original lake bottom as determined from the cores.

RESULTS

A comparison of the "old image" of lake bottom contours based on available bore logs and "new image" of lake bottom contours based on AquaScan Survey is provided below. From data comparison it is apparent that the AquaScan Survey Data provides a much higher resolution image as compared to conventional boring data.

"Old Image" of Bottom Contours
"New Image" of Lake Bottom Contours

Archaeological Interests  

Based on the results of the high resolution image obtained from the AquaScan Survey,  a large sub-bottom anomaly (mound) appeared to be present in the subsurface. The radar reflections from the top of this layer suggest that the composition of this layer is clearly different from the natural occurring surrounding marl. Parabolic reflections in the radar profiles over the area of interest indicate the presence of objects in the subsurface of possible archaeological interest for further investigation.

BACK to TOP