September 7, 2000

 Dear Chris:

      After giving some thought to the comments made during the meeting held on Aug 21, 2000, I have included herein a simple outline for consideration.  If our group considers this outline to have sufficient merit, specific details could be developed.

 1.  Determine if saltwater is moving through the confining bed overlying the Upper Floridan aquifer.  USGS Savannah Area Model showed for 1985 conditions that approximately 50 cfs (approx 30 million gallons per day) of water recharging the Upper Floridan aquifer within the confluence of the Cone of Depression was contributed to vertical leakage from the surficial aquifer through the confining bed (USGS Open-file Report 920-629; page 33).

 Solution: The USACE is planning to drill a substantial number of boreholes along  the Savannah Channel. Cores taken from the confining material could be squeezed to extract pore water.  If salty water is moving vertically downward, we could expect to see a water quality profile in some of the boreholes.

 2.   If salty water is present in the confining material, determine the vertical rate of movement and time required to penetrate the confining bed.  Thickness of the confining bed will be an important factor.

 Solution: The USGS model or a more site specific model combined with updated hydraulic values for the area in question may offer the most reasonable method of calculating the vertical rate of salty water through the confining bed.

 3.   If the downward vertical rate of movement is within a “window of concern,” the impact of vertical leakage should be determined.

 Solution:   Dilution rates and flow should be calculated using the most appropriate model to determine if the impact on water quality will be significant.

                                                                      Sincerely,

                                                                      Camille Ransom, III