1. Abstract
 
        Communities in the lower Merrimack River basin and coastal river basins
     of southeastern New Hampshire are experiencing increased demands for water
     because of a rapid increase in population. The population in 1987 was
     228,495 and is expected to increase by 30 percent in the next decade. As of
     1987, five towns used the stratified-drift aquifers for municipal supply
     and withdrew an estimated 6 million gallons per day. Four towns used the
     bedrock aquifer for municipal supply and withdrew an average of 1.6 million
     gallons per day.
 
        Stratified-drift deposits cover 78 of the 327 square miles of the study
     area. These deposits are generally less than 10 square miles in areal
     extent, and their saturated thickness ranges from less than 20 feet to as
     much as 100 feet. Transmissivity exceeds 4,000 square feet per day in
     several locations. Stratified-drift aquifers in the eastern part are pre-
     dominantly small ice-contact deposits surrounded by marine sediments or
     till of low hydraulic conductivity. Stratified-drift aquifers in the
     western part consist of ice-contact and proglacial deposits that are large
     in areal extent and are commonly in contact with surface-water bodies.
 
 
 
   Descriptors:
     *Geohydrology, *Ground Water quality, *Stratified-drift aquifers,
     *Lower Merrimack and coastal river basins, *southeastern New Hampshire
 
 2. Applications that use this data
       This data can be used for producing maps, illustrations, and
      performing a geographic analyis to assist in hydrologic studies.
 
   2.1  Intended use of data
       This data can be used by federal, state, and local government
    agencies, involved with resource management and plannning. Private
    engineering firms and educational institutions may also benefit
    from this data.
 
   2.2  Limitations of data
       Transmissivity values should be considered estimates only and
    are a result of existing data in the study area.
 
 3. Attribute discussion
 
      TMAX -- The upper limit of the transmissivity zone, in feet squared
              per day.
 
      TMIN -- The lower limit of the transmissivity zone, in feet squared
              per day.
 
      RANGE -- A single value that defines the transmissivity zone
               (in feet squared per day). The folowing table explains
               coding for the RANGE item.
 
              1 = 0
              2 = less than 500
              3 = 0 to 1000
              4 = 500 to 1000
              5 = 0 to 1500
              6 = greater than 1500
              7 = 0 to 2000
              8 = 1000 to 2000
              9 = 2000 to 3000
             10 = greater than 3000
             11 = 2000 to 4000
             12 = greater than 4000
             13 = 4000 to 6000
             14 = greater than 6000
             15 = 4000 to 8000
             16 = greater than 8000
             98 = unable to contour transmissivity
             99 = unable to contour transmissivity
                  and saturated thickness
 
     For example a zone with transmissivty greater than 8000 feet
     squared per day has a TMAX of 99999, a TMIN of 8000, and range
     of 16.
 
 
 
 4.  Procedures used to create or automate data
        Transmissivites of stratified-drift aquifers, in feet squared per day
     (ft2/d), were estimated from test-boring logs by calculating hydraulic
     conductivity for specific intervals, multiplying these values by the
     saturated thickness of the interval, and summing the results. Transmis-
     sivity values report by published engineering consultants were used as
     well as calculating transmissivites from unpublished aquifer test data.
        The transmissivity coverage is a polygon coverage where each polygon
     represents a range a transmissivity; for example, 0 to 1,000 ft2/d. Some
     polygons are hills of till that protrude the stratified-drift and, there-
     fore, have a transmissivty of 0ft2/d. Transmissivities were first inter-
     preted on paper topographic maps, then transferred to 1:24,000 or 1:25,000
     scale-stable mylar USGS quadrangle maps. The maps were then digitized into
     ARC/INFO coverages by Complex Systems, in Durham, NH.
        The finished study-wide coverage was clipped to the hydrography
     coverage ( 1:24,000 scale hydrography representaion obtained from conver-
     ting USGS Digital Line Graphs (DLG) into ARC/INFO coverages), so that
     transmissivity did not extend into rivers (those that were wide enough to
     be a polygon in the hydrography coverage) or other surface water bodies
     such as lakes or ponds.
 
 
 5.  Revisions made to data
        Revision after colleague and editorial review.
 
 6.  Reviews applied to data
        Data was reviewed by the USGS and N.H. Dept. of Environmental Services,
     Water Resources Division.
 
 7.  Related spatial and tabular data sets and programs
        Aquifers boundaries
 
 
 8.  References cited
     GEOHYDROLOGY AND WATER QUALITY OF STRATIFIED-DRIFT AQUIFERS IN THE
     LOWER MERRIMACK AND COASTAL RIVER BASINS, SOUTHEASTERN NEW HAMPSHIRE.
     by Peter J. Stekl and Sarah M. Flanagan   U.S. Geological Survey
     Water-Resources Investigations Report 91-4025
 
 9.  Notes:
     The Projection is as follows:
     PROJECTION STATE
     UNITS FEET
     DATUM NAD83
     ZONE 4676