Figure 1. GPR survey of a Colonial smuggling road used prior to the Revolutionary War. Study area was an agricultural field (left). Historic roadway and structures were identified in the radar data.
An array of systems are used for geophysical surveys including: a GSSI SIR3000 GPR system, a Geonics EM-31 terrain resistivity/conductivity meter, a MF-1 Fluxgate magnetometer, and a Strata-Scout electrical resistivity system. Seramur and Associates is skilled in processing geophysical data to identify anomalies associated with buried structures, underground storage tanks, utilities and waste disposal areas.
Ground Penetrating Radar
Seramur & Associates has used GPR and magnetometer surveys at a wide variety of sites to map the location of structures at a historic quarry, a 1660’s cart road and a late 19th century industrial facility.
GPR system with the SIR 3000 digital control unit locating historic features prior to a DOT road widening.
GPR data, unprocessed profile on left and processed data in transparency view on right.
The GPR is very effective at delineating roads, building footprints and buried infrastructure.
Ground penetrating radar survey to locate homestead at historic archaeology site (upper). Two images of processed GPR data showing a rectangular footprint and adjacent ellipsoid anomalies (lower).
Cemetery surveys are one of Seramur & Associates’ specialties. Geophysical surveys at historic cemeteries are used to identify unmarked graves allowing the cemetery boundaries to be delineated. These boundaries typically include burials of indigent people outside of formal cemetery walls. Local or family cemeteries are not uncommon on historic properties. Graves were often marked with wooden crosses or field stone now dislodged from its original location.
GPR survey to located unmarked graves in historic cemetery (left) and three-dimensional view of GPR grid showing reflections off the base of the grave shaft (right).
Projects involving critical infrastructure development can require that historic cemeteries be moved. Our staff has experience working with families of the descendants and our cemetery maps have assisted in providing closure in these sensitive situations.
GPR anomalies marked during survey of a field where a cemetery was recorded on an early 19th century plat (left). Grave locations were verified with plow zone stripping prior to moving the cemetery for construction of a new high school (right).
Electric Resistivity (ER) Surveys
Electrical resistivity surveys can detect buried metallic objects (USTs, drums, utilities...) and identify areas of subsurface disturbance such as former waste disposal pits or unmarked graves. An ER survey is also used to map the footprint of former structures by imaging changes in soil compaction or composition along the footer. Seramur and Associates uses a Soil Test, Strata-Scout electrical resistivity system with a linear, four-electrode Werner Array for most of these applications.
Strata-Scout set up with variable distance electrode array for imaging the depth to buried features (left). The ER system with a fixed distance electrode spacing for imaging anomalies in the upper 3-5 feet such as unmarked graves (right).
Results of an ER survey at a historic cemetery showing north-south aligned rows of unmarked graves.
Seramur and Associates provide two options for magnetometer surveys. A MF-1 Fluxgate magnetometer provides an excellent method for identifying buried ferrous objects such as tanks, pipelines, drums, or buried industrial debris. It is a quick, inexpensive and nonintrusive method for locating USTs and buried ferrous objects.
For more sensitive surveys a Geometrics Cesium Vapor G858 Magnetometer is used to measure very slight changes in the earth’s magnetic field due to the presence of subsurface features including footers, fence lines, historic roads and trails. This system is commonly used in archaeology surveys. The magnetometer data is downloaded and processed to produce an image of anomalies across the survey grid.
Gradiometer survey at a historic archaeological site for DelDOT using the Geometrics Cesium Vapor G858 Magnetometer.
Seramur & Associates provide a variety of services to address environmental concerns during restoration of historic properties. We have over 20 years of experience dealing with regulatory agencies and remediating potentially hazardous situations. We combine this experience with our knowledge of the cultural resources industry to develop environmental solutions that are compatible with preservation goals.
The planned restoration of a 1938 Post Office did not include cleanup of contaminated soil from the abandoned tank discovered during installation of footer drains. Seramur & Associates assisted the Town in removing the UST and filing the required reports with NC DENR, allowing the restoration work to proceed.
Subsurface investigations using geophysical surveys are useful in locating septic tanks and drain fields, underground storage tanks and assess soil conditions associated with foundation settling.
Magnetometer survey with the Fluxgate MF-1 to determine the number, size and orientation of USTs at a closed, mid-20th century manufacturing plant (left). MF-1 locates the end of the first UST (right).