Agenda - 06-29-1992 - Laserfiche WebLink

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WATER coNATMNN GRO WATER Groundwater protection is a major concern in siting and designing a sanitary landfill in North Carolina. No field testing will be performed to determine- the actual hydrogeologic characteristics of the individual candidate sites. Investigations of the candidate sites subsequent to this phase of the project will be performed to obtain site specific information pertaining to actual subsurface soil types, depth to groundwater, and groundwater quality. Because of the lack of the site specific hydrogeologic information, surrogate parameters must be selected to measure the impact to groundwater with readily available information. The soil type influences the rate and extent of migration of a contaminant released from a landfill if a leak in the liner system occurs. For example, clayey soils, which are generally more impervious than other soil types, will tend to restrict the downward migration of contaminants from a site and potentially filter certain contaminants. Also, the deeper the underlying soil strata, the greater the protection. Exhibit R -2A presents impact ratings related to groundwater as a function of soil type and depth to groundwater. More impervious and deeper soil strata are assigned a low impact rating. Conversely, highly pervious and shallow soils are, assigned a greater impact rating. The soil types are grouped into sands, silts, and clays. This is done to indicate the general permeability characteristics of the soils. Rock characteristic categories are also included because, in some instances, groundwater is located beneath all soils within the bedrock. These rock categories indicate the water flow characteristics from relatively pervious rock strata to impervious strata. The depth to groundwater ranges give a variation of impact ratings based on the projected depths to groundwater beneath Pa E n