1. Abstract The U.S. Geological Survey, in cooperation with the State of New Hampshire, Department of Environmental Services, Water Resources Division has assessed the geohydrology and water qualtiy of stratified-drift aquifers in the middle Merrimack River basin in south-central New Hampshire. The middle Merrimack River basin drains 496 square miles; 98 square miles is underlain by stratified-drift aquifers. Saturated thickness of stratified drift within the study area is generally less than 2,000 feet squared per day but locally exceeds 6,000 feet squared per day. At present (1990), ground-water withdrawals from stratified-drift for public supply are about 0.4 million gallons per day within the basin. Many of the stratified-drift aquifers within the study area are not developed to thier fullest potential. The geohydrology of stratified-drift aquifers was investigated by focusing on basic aquifer properties, including aquifer boundaries; recharge, discharge, and direction of ground-water flow; saturated thickness and storage; and transmissivity. Surficial geologic mapping assisted in the determination of aquifer boundaries. Data from 757 wells and test borings were used to produce maps of water-table altitude, saturated thickness, and transmissivity of stratified drift. More than 10 miles of siesmic-refraction profiling and 14 miles of siesmic-reflection profiling were also used to construct the water table and saturated thickness maps. 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. 3. Attribute discussion TMAX -- The upper limit of the transmissivity zone TMIN -- The lower limit of the transmissivity zone 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 97 = undifferantiated (city of Manchester) 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, therefore, have a transmissivty of nearly 0ft2/d. Transmissivities were interpreted on 1:24,000 or 1:25,000 scale-stable mylar USGS quadrangle maps and digitized into a geographic information system (GIS), using ARC/ INFO version 7.0. The quadrangle maps were then merged into one study-wide coverage and edited for errors and discrepancies. The finished study-wide coverage were clipped and erased with the hydro- graphy coverage ( 1:24,000 or 1:25,000 scale hydrography representaion obtained from converting USGS Digital Line Graphs (DLG) into ARC/INFO cover- ages), 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 1.0 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 Other data sets available from this study include, aquifers boundaries, saturated thickness, water table, and seismic lines. 8. References cited GEOHYDROLOGY AND WATER QUALITY OF STRATIFIED-DRIFT AQUIFERS IN THE MIDDLE MERRIMACK RIVER BASIN, SOUTH-CENTRAL NEW HAMPSHIRE. U.S. Geological Survey Water-Resources Investigations Report 92-4192 by Joseph D. Ayotte and Kenneth W. Toppin 9. Notes: The Projection is as follows: PROJECTION STATE UNITS FEET ZONE 4676 DATUM NAD83