BAIZE, DAVID G., baizedg@columb32.dhec.state.sc.us, DHEC, Bureau of Water, Columbia, SC, 29201

The 1996 Amendments to the Safe Drinking Water Act (SDWA) require states to develop and submit to EPA Source Water Assessment Programs (SWAP’s).   Source Water Protection Assessments will be completed for all Federally defined public water systems for both surface water and groundwater sources (73 surface water intakes and 2268 wells).
The first step is to delineate protection areas for groundwater wells and surface water intakes. Wellhead Protection Areas (WHPA’s) are based on identifying areas or zones of water contribution (ZOC) for a pumping well.  For the SWAP, a 10 year time-of-travel (TOT) is calculated using computer models to estimate the ZOC and serve as the source water protection area. For the Piedmont, a volumetric/recharge-area method based on pumping rate and recharge rate is used to define a contribution area for the well(s).
    The Source Water Protection Area (SWPA) for a surface water system includes the entire drainage basin upstream from the intake to the hydrologic boundary of the drainage basin.  The primary SWPA is defined as all subwatersheds adjoining the 24-hr travel distance upstream (main stream) from the intake.   The SWPA will be segmented into three susceptibility zones.  Susceptibility Zone 1 (SZ1) will be established 200 feet (61 m) from either the edge of the stream or from the edge of the geomorphic flood plain and from the edge of reservoirs. Susceptibility Zone 2 (SZ2) is established as a zone of concern, based on relative proximity to the surface water and associated travel time of potential contaminants, but as an area of relatively less concern than the very rapid overland flow and groundwater discharge typical of SZ1. Susceptibility Zone 3 (SZ3) is simply the remainder of the 14-digit HUC drainage basin.
    The second step is to inventory potential contamination sources within the protection areas.  Contaminants of concern that will be inventoried (at a minimum) include the contaminants regulated under the Safe Drinking Water Act (i.e., contaminants with an established maximum contaminant level) and the microorganism Cryptosporidium (and other pathogens).
The third step is to conduct an susceptibility analysis.  Susceptibility combines vulnerability (i.e., natural conditions) with the actual presence of potential contamination sources (PCS’s).  If a vulnerable system has no significant PCS’s within the source area, it would not be considered susceptible.  The three delineated Susceptibility Zones are used as a general framework to rank the susceptibility of an intake (SZ1, SZ2, or SZ3) or well (three larger geographic areas).  Each inventoried PCS in an SWPA is assigned a low, moderate, or high susceptibility ranking in a susceptibility matrix based on the relative location (i.e., zone) and type of contaminant.