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| Publications— Scientific Investigations Map |
U.S. Geological Survey Scientific Investigations Map 2995
By Lindsay B. Hale
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View Scientific Investigations Map 2995 (sheet 1) in PDF (26 inches x 32½ inches) 4.7 MB
View Scientific Investigations Map 2995 (sheet 2) in PDF (26 inches x 38 inches) 4.3 MB
Since 1984, the U.S. Geological Survey (USGS) has been mapping the altitude and configuration
of the potentiometric surface in Chester County as part of an ongoing cooperative program
to measure and describe the water resources of the county. These maps can be used to determine the general direction
of ground-water flow and are frequently referenced by municipalities and developers to
evaluate ground-water conditions for water supply and resource-protection requirements.
For this study, the potentiometric surface was mapped for an area in south-central Chester
County. The northern part of the map includes portions of Highland, East Fallowfield, Londonderry,
and West Marlborough Townships and South Coatesville and Modena Boroughs. The southern part of the map
includes portions of Londonderry, West Marlborough, Penn, London Grove, and New Garden Townships and West
Grove and Avondale Boroughs. The study area is mostly underlain by metamorphic rocks of the Glenarm Supergroup
including Peters Creek Schist, Octoraro Phyllite, Wissahickon Schist, Cockeysville Mrable, and Setters Quartzite;
and by pegmatite, mafic gneiss, felsic gneiss, and diabase. Ground water is obtained from these bedrock formations
by wells that intercept fractures.
The altitude and configuration of the potentiometric surface was contoured from water levels
measured on different dates in available wells during May through July 2006 and from the altitude of springs and
perennial streams. Topography was used as a guide for contouring so that the altitude of the potentiometric surface
was inferred nowhere to be higher than the land surface. The potentiometric surface shown on this map is an
approximation of the water table. The altitude of the actual potentiometric surface may differ from the water table, especially in
areas where wells are completed in a semi-confined zone or have long open intervals that reflect the
composite hydraulic head of multiple water-yielding fractures. A composite head may differ
from the potentiometric-surface altitude, particularly beneath hilltops and valleys where
vertical hydraulic gradients are significant.
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View Scientific Investigations Map 2995 (sheet 1) in PDF (26 inches x 32½ inches) 4.7 MB
View Scientific Investigations Map 2995 (sheet 2) in PDF (26 inches x 38 inches) 4.3 MB
For more information about USGS activities in Pennsylvania contact:
Director
USGS Pennsylvania Water Science Center
215 Limekiln Road
New Cumberland, Pennsylvania 17070
Telephone: (717) 730-6960
Fax: (717) 730-6997
or access the USGS Water Resources of Pennsylvania home page at:
http://pa.water.usgs.gov/.
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