Timmons Group was contracted to provide hydrographic surveys, digital DTM, contour mapping and engineering evaluation to determine the stage-volume relationship of the entire Swift Creek Reservoir. The surveys were conducted in order for the County to be able to evaluate the stage-storage relationships of the reservoir at different depths, beginning with a normal pool elevation and working downstream. Horizontal and vertical control monuments were established by GPS, and the reservoir boundary was established by aerial Photogrammetry. Vertical Control was verified through field observations, which were measured against the existing gauging stations at the dam. These observations verified through field observations, which were measured agains the existing gauging stations at the dam. These observations verified that both vertical datum matched. Sounds of the reservoir were compiled using a portable echo sounding equipment used in connection with RTK GPS rover units. Data was collected along route lines, with an approximate measured density of 100-200'. Horizontal and vertical data was acquired, in order to depict the bottom elevations and contours. Nearly 50,000 observed corrdinate locations were gathered, and incorporated into the final mapping.