Geophysical survey of Emory Grove United Methodist Church parking lot using ground-penetrating radar

Abstract

Project Background and Objectives In 1864, freed African Americans founded the Emory Grove community in Gaithersburg, Maryland. For about 100 years, since its inception, this community was vibrant and close-knit. At its height, Emory Grove was 300 acres and home to roughly 500 residents. The Emory Grove community hosted Methodist gatherings, called “camp meetings.” During the 1960s and 1970s, urban renewal led to the destruction of this once spirited community. With the goal of reestablishing community cohesion, Montgomery County’s Housing Opportunities Commission (HOC) and the Emory Grove United Methodist Church envision a redevelopment project known as Heritage Emory Grove (HEG). This plan centers redevelopment efforts around the Emory Grove United Methodist Church and prioritizes historic programming and cultural amenities. The issue with the redevelopment is predominantly associated with the unmarked graves around the church and nearby cemetery that have been lost over time. Before proceeding with the redevelopment, local officials and community members want to ensure that any unmarked graves in the vicinity are identified and properly marked to avoid disturbing them during the redevelopment process. The objective of this study is to conduct a geophysical survey of the church parking lot and yard area (from hereafter referred to as the “landscaped area”) using ground-penetrating radar (GPR). Ground-penetrating radar is a non-intrusive method of surveying the shallow subsurface to investigate underground structures. It uses electromagnetic radiation in the microwave band frequencies of the radio spectrum to detect reflected signals from subsurface structures. It is typically used for the investigation of buried utilities such as pipes, cables, masonry, asphalt, and metals, and will be invaluable in locating and identifying potential unmarked gravesites. Geological Context Montgomery County has varying geology depending on the region (Singewald et al., 1953). The central portion of the county is made up of Ijamsville phyllite, the Wissahickon formation, and the Sykesville formation. Gaithersburg is situated in a region of predominantly Wissahickon formation (i.e., banded, or laminated quartz-rich phyllites and schists containing magnetite quartz veins), but Emory Grove is situated on a strip of serpentine bedrock. The soil makeup is as diverse as the region within the Piedmont Plateau, which has experienced deep stream valley incisions and complex structural geomorphology that has resisted erosion (Maryland Dept. of State Planning, 1973).