IMPORTANCE OF GEOLOGICAL ASSESSMENT FOR SITING AND/OR CONSTRUCTION OF RESERVOIRS IN THE GULF COASTAL PLAIN SEDIMENTS: THREE EXAMPLES FROM MISSISSIPPI

Many different conditions may exist that need to be taken into consideration in the siting and/or construction of reservoirs in the sediments of the Gulf Coastal Plain. There are many site conditions that may need to be established in addition to the common considerations of valley/floodplain configuration, hydrology, water quality, and source materials for dam construction. A review of three proposed reservoir sites in Mississippi demonstrates different conditions of concern at each that are important in consideration of siting and/or construction of a reservoir in addition to those common ones. Those additional conditions of concern encountered in the geologic assessments for the three reservoirs include high permeability sands in proposed reservoirs' dam abutments and basins, possible faulting below a proposed dam site, geologic materials of concern below proposed dam sites, and karst conditions within a proposed reservoir's basin. The conditions of concern for some of the proposed sites may be relatively easily remediated, but others may be significant enough to suggest the site is not feasible for a reservoir. In all cases, should the geologic assessment not have been conducted, those conditions would not have been determined, potentially resulting in failure of the reservoirs. The failures could result from a variety of reasons, including leakage and/or failure of the dam.