A digital model of the sedimentary Northern Atlantic Coastal Plain aquifer system is composed of 20 rasters and hydrogeologic unit extent polygons. Rasters describe the top elevations of regional aquifers and confining units at a resolution of 2640 feet (1/2 mile). The rasters are clipped to the extent polygons, which represent the spatial extents of the hydrogeologic units onshore and several miles offshore. This three-dimensional hydrogeologic model was constructed as part of a U.S. Geological Survey Groundwater Resources Program study of groundwater availability in the Northern Atlantic Coastal Plain (NACP) aquifer system, including parts of New York, New Jersey, Delaware, Maryland, Virginia, and North Carolina. Digital elevations of major regional aquifers and confining units were compiled from published digital elevation models (DEM) of various parts of the NACP aquifer system to provide a consistent regional model of hydrogeologic unit geometries. The many studies incorporated within these data include the interpretation and analysis of thousands of well logs and other related information spanning at least a century of study. These regional units are derived from published unit-elevation contours interpreted by geologists at the state and local level, and incorporate little additional interpretation of unit elevations beyond the correlation of individual units across geographic boundaries and some extrapolation of units to the edges of the modeled area. This regionally consistent hydrogeologic framework was used as the foundation of a MODFLOW groundwater flow model of the NACP, which informed modifications to the regional hydrogeologic units that have now been incorporated into the framework data.

This point shapefile consists of digital points that represent water level altitudes in the Lloyd and North Shore aquifers of Long Island, New York. The U.S. Geological Survey measured 55 observation wells and 5 supply wells screened in the Lloyd aquifer and the contiguous and hydraulically connected North Shore aquifer. This point shapefile is a digital representation of the water levels presented in sheet 3 of Scientific Investigations Map 3398.

This polyline shapefile consists of digital contours that represent the potentiometric-surface altitude of water in the Lloyd and contiguous North Shore aquifer beneath Nassau and Suffolk Counties, Long Island, New York. The U.S. Geological Survey constructed a potentiometric-surface altitude map using ground-water levels measured in the Lloyd and North Shore aquifers during the spring of 2016. Contours were constructed at a scale of 1:125,000 from water-level data collected at 60 groundwater monitoring wells. The potentiometric-surface altitude contours were digitized and compared to 1997, 2006, 2010 and 2013 potentiometric-surface altitude maps. The contours range from -5 to 60 feet at 5 foot intervals above and below the National Geodetic Vertical Datum of 1929. This polyline shapefile is a digital representation of the potentiometric-surface contours presented in sheet 3 of Scientific Investigations Map 3398.

This polyline shapefile consists of digital contours that represent the potentiometric-surface altitude of water in the Lloyd and contiguous North Shore aquifer beneath Long Island, New York. The U.S. Geological Survey constructed a potentiometric-surface altitude map using ground-water levels measured in the Lloyd and North Shore aquifers during the spring of 2013. Contours were constructed at a scale of 1:125,000 from water-level data collected at 66 groundwater monitoring wells. The potentiometric-surface altitude contours were digitized and compared to 1997, 2006, and 2010 potentiometric-surface altitude maps. The contours range from -10 to 60 feet at 5 foot intervals above and below the National Geodetic Vertical Datum of 1929. This polyline shapefile is a digital representation of the potentiometric-surface contours presented in sheet 3 of Scientific Investigations Map 3326.

A digital map of the thickness of the surficial unconfined aquifer, including from the land surface and unsaturated zone to the bottom of sediments of geologic units identified as part of the surficial aquifer, was produced to improve understanding of the hydrologic system in the Maryland and Delaware portions of the Delmarva Peninsula. The map is intended to be used in conjunction with other environmental coverages (such land use, wetlands, and soil characteristics) to provide a subsurface hydrogeologic component to studies of nitrate transport that have historically relied on maps of surficial features. It could also be used to study the transport of other water soluble chemicals. The map was made using the best currently available data, which was of varying scales. It was created by overlaying a high resolution land surface and bathymetry digital elevation model (DEM) on a digital representation of the base of the surficial aquifer, part of hydrogeologic framework, as defined by Andreasen and others (2013). Thickness was calculated as the difference between the top of land surface and the bottom of the surficial aquifer sediments, which include sediments from geologic formations of late-Miocene through Quaternary age. Geologic formations with predominantly sandy surficial sediments that comprise the surficial aquifer on the Delmarva Peninsula include the Parsonsburg Sand, Sinepuxent Formation (Fm.), and parts of the Omar Fm. north of Indian River Bay in Delaware, the Columbia Fm., Beaverdam Fm., and Pennsauken Fm. (Ator and others 2005; Owens and Denney, 1986; Mixon, 1985; Bachman and Wilson, 1984). Formations with mixed texture and sandy stratigraphy including the Scotts Corner Fm. and Lynch Heights Fm. in Delaware are also considered part of the surficial aquifer (Ramsey, 1997). Subcropping aquifers and confining beds underlie the surficial aquifer throughout the Peninsula and may increase or limit its thickness, respectively (Andreasen and others, 2013). Stream incision through the surficial aquifer into older fine-textured sediments is more common in the northern part of the Peninsula where confined aquifers and their confining beds subcrop beneath the surficial aquifer. The potential for nitrate transport is greatest where relatively coarse sediments of the unconfined surficial aquifer (such as sand and gravel), are present beneath uplands and streams. Where these sediments are truncated and the streambed is incised into underlying fine-textured sediments, the potential for nitrate transport is much less and typically limited to stream-bank seeps that flow across the floodplain. In parts of south-central Maryland and southern Delaware the surficial aquifer sediments are complex with surficial sandy sediments generally less than 20 ft thick (indicated as 19 ft on the map). They include the Parsonsburg Sand and some surficial sandy facies of the Omar Fm. underlain by predominantly fine-textured sediments of the Walston Silt and Omar Fm. (Denney and others, 1979; Owens and Denney, 1979). Even though the surficial aquifer is relatively thin in this area, extensive ditching of flat poorly drained farmland allows seasonal transport of nitrate from groundwater to streams when the water table is above the base of the ditches (Lindsey and others, 2003). Geologic units of the Coastal Lowlands that surround the Peninsula are relatively thin in many areas and are primarily composed of fine-grained estuarine deposits with some coarse-textured sediments, in particular remnant beach-ridge and dune deposits (Ator and others, 2005). The Kent Island Fm. (Owens and Denney, 1986), which is part of the Coastal Lowlands on the western side of the Peninsula, has predominantly fine-grained sediments and is not included in the surficial aquifer in Maryland, as defined by Bachman and Wilson (1984); the surficial aquifer is shown to have 0 ft thickness on the map in the area mapped as Kent Island Fm. Also shown on the map as 0 ft thickness are

This point shapefile consists of digital points that represent water level altitudes in the Lloyd and North Shore aquifers of Long Island, New York. The U.S. Geological Survey measured 58 observation wells and 8 supply wells screened in the Lloyd aquifer and the contiguous and hydraulically connected North Shore aquifer. This point shapefile is a digital representation of the water levels presented in sheet 3 of Scientific Investigations Map 3326.

The data set pp1773_extents contains polygon datasets that represent the areal extents of each of the 16 hydrogeologic units of the of the Atlantic Coastal Plain of North and South Carolina. [The total areal extent includes a small area in southeastern Virginia, the Atlantic Coastal Plain within North Carolina and South Carolina, and a region in southeast Georgia within the Atlantic Coastal Plain.] Each hydrogeological unit is referred to as its model layer number as represented in the report PP1773. For clarity, they are listed below along with the aquifer unit or confining unit name in North Carolina and its correlated unit name in South Carolina. L1 Surficial aquifer L2 Yorktown confining unit / Upper Floridan confining unit L3 Yorktown aquifer / Upper Floridan aquifer L4 Castle Hayne - Pungo River confining unit / Middle Floridan confining unit (To be referred to as "Castle Hayne / Middle Floridan confining unit" in this document) L5 Castle Hayne - Pungo River aquifer / Middle Floridan aquifer (To be referred to as "Castle Hayne - Middle Floridan aquifer" in this document) L6 Beaufort confing unit / Gordon confining unit L7 Beaufort aquifer / Gordon aquifer L8 Peedee confining unit / Crouch Branch confining unit L9 Peedee aquifer / Crouch Branch aquifer L10 Black Creek confining unit / McQueen Branch confining unit L11 Black Creek aquifer / McQueen Branch aquifer L12 Upper Cape Fear confining unit / Charleston confining unit L13 Upper Cape Fear aquifer / Charleston aquifer L14 Lower Cape Fear confining unit / Gramling confining unit L15 Lower Cape Fear aquifer / Gramling aquifer L16 Lower Cretaceous confining unit and aquifer Spatial data set pp1773_layer1_extent represents the extent of the top of the surficial aquifer, which is Layer 1 in the groundwater model used to simulate the aquifer system described in PP 1773. The surficial aquifer is the uppermost aquifer. It is an unconfined aquifer that is uniformly present except where it is incised by streams. The top of the surficial aquifer is equivalent to the land surface. The extent was derived primarily by geologic and hydraulic properties, as the surficial aquifer is an unconfined layer primarily composed of sediments of Quaternary age, plus some older sediments in areas due to a different stratigraphic position of the first underlying confining layer. Spatial data set pp_1773_layer_2 is the Yorktown/Upper Floridan confining unit. It is not composed of a single unit because the unit's series of clay and silt beds vary greatly in stratigraphic position. Spatial dataset pp1773_layer3_extent represents the extent of the Yorktown/Upper Floridan aquifer. The Yorktown aquifer is present only in the northern half of the North Carolina Coastal Plain. Outliers exist in Robeson, Bladen and Dublin counties, but are not separated from the surficial aquifer by a confining unit, and not considered a distinct aquifer in these areas. The Upper Floridan aquifer extent covers a southern portion of South Carolina and southern portion of Georgia. Spatial dataset pp1773_layer4_extent represents the extent of the Castle Hayne/Middle Floridan confining unit. The Castle Hayne confining unit consists of beds of clay and silt that vary in stratigraphic position and are absent in a number of areas in the central and southern North Carolina Coastal Plain. The Middle Floridan confining unit extends from South Carolina to southern Georgia. It is not continuous with the Castle Hayne confining unit. Spatial dataset pp1773_layer5_extent represents the extent of the Castle Hayne/Middle Floridan aquifer. The Castle Hayne aquifer is located in the central and southern North Carolina Coastal Plain; the Middle Floridan aquifer is more south, in southern South Carolina and southern Georgia. Spatial dataset pp1773_layer6_extent represents the extent of the Beaufort/Gordon confining unit. The Beaufort confining unit is located in northeastern North Carolina and southeastern Virginia. It is best developed in

This dataset includes "smoothing points" used in the creation of the Jamestown hydrogeologic framework. Smoothing points were manually added and were used to enhance interpolated layers using geologic assumptions and include: valley edge points, centerline bedrock points, and upland bedrock SSURGO points.