GEOPHYSICAL SURVEY OF A HISTORIC COLONIAL NEIGHBORHOOD IN PORTSMOUTH, NEW HAMPSHIRE

The electromagnetic induction survey described herein is to be conducted at the Strawbery Banke Museum in Portsmouth, New Hampshire; specifically, the area previously known as Puddle Dock. Strawbery Banke is an outdoor history museum dedicated to preserving the colonial Portsmouth, New Hampshire neighborhood for which the museum is named. It is one of the oldest continuously occupied neighborhoods in the United States, with the Museum exhibiting 42 restored houses, dating as far back as 1695. The Puddle Dock area of the neighborhood, once a waterway connecting to the Piscataqua River, was filled in during the early 1900’s, and is now an open field. This survey will determine if saltwater from the Piscataqua River is flowing through the fill and into the Puddle Dock field and is further intruding into the foundations of nearby historic residences. A Geophysical Survey Systems Inc. Profiler EMP-400, in vertical dipole orientation with triple frequency measurements, will be used to measure ground conductivity to locate areas of saltwater concentrations. As the conductivity of seawater is 4.8 Siemens-per-meter (S*m^-1), areas with conductivity significantly higher than dry soil’s 0.5-0.001 S*m^-1 range of conductivities can be presumed to contain seawater.