Historical Grave Mapping, San Ramon Valley Unified School District, CA

san ramon valley california gravesite scanning

san ramon valley california gravesite scanningIn today’s world, it can be incredibly expensive to fire up a backhoe, begin job site excavation, and discover unknown gravesites. Lost time is a tremendous factor all by itself, but if the burials should be determined as historic and protected, the entire project may be at risk. San Ramon Valley Unified School District made the intelligent move to bring in GPR Data Inc. and assess the area of their swimming pool expansion early in their planning stages.


An area roughly 173 feet by 206 feet needs to be analyzed for unknown burials up to 6′ down from the surface. A 3D map of utilities in the area will supplement the grave mapping and assist with future construction. Roughly half of the area to be scanned is an asphalt parking lot which is the main thoroughfare for the High School’s summer sports camps, and relatively unobstructed other than the constant traffic. The second half of the survey area comprises the existing Olympic-size pool and surrounding features. This portion of the survey is heavily obstructed by fencelines, safety boundaries, bleachers, pool features, the pumphouse, and the like. The surface materials include asphalt, reinforced concrete, and grass, creating a variety of radar interfaces to correct for.


The survey are is divided into two logical units at the lower pool fenceline. The asphalt area is collected first, with a full spread of high resolution GPMR data from the tennis courts to the football field and up to the pool fence. Collection is relatively quick and straightforward, with allowances for both lower corners of the grid to be obstructed by the sports zones. The pool area is collected next, with unique profile sets surrounding each obstruction. High resolution 3D mapping is produced over the sidewalk, the grass, behind the pumphouse, around the pool, behind the diving board — no area is left unscanned. This collection takes more time, both for accurate antenna placement and for precise field notes, but the result is a degree of collection accuracy which is unparalleled in this industry.


This complete GPMR analysis has allowed construction to begin without fear of hemorrhaging time and money due to the surprise discovery of unmarked human graves. The cost of GPR Data’s services was meager when compared with the potential loss from any unexpected excavation of historic burials.


Posted on

July 25, 2017