As part of the Bolsa Chica Military Reservation, a Radar Station was established on the Mesa which consisted of several buildings, all of which have disappeared. In the 1940s hundreds of yards of earth were moved and removed in order to install an immense subsurface concrete bunker, covered by numerous buildings including a radar tower camouflaged by a water tower. Situated on and near a prehistoric Native village site, the questions became how much of the archaeological site was destroyed by these activities and how much remained. One of the non-destructive approaches to examining the condition of the subsurface deposits is geophysics. The 2010 geophysical investigation on the Goodell parcel on Bolsa Chica Mesa was also designed to determine how many of the previous 28 historic structures, once located on archaeological site CA-ORA-83/144, penetrated the surface and still had subsurface remains. The initial approach included compiling 26 historic aerial photographs, documenting visible surface features, and profiling soils subsurface strata from the edges of the Mesa. These data provided a model for interpreting the subsequent geophysical work. A geophysical survey was then conducted using both a ground penetrating radar and a terrain conductivity, in order to locate features that may exist but are not visible on the surface. Upon completion of fieldwork, all data were processed and integrated into a GIS map for comparison to the historic aerial photographs. The soils profiles complemented the geophysical readings and collectively showed areas with building remains and areas likely still relatively intact. This allowed for establishing set-asides for what appeared to be intact archaeological deposits and planning development around them.
SRSinc, along with Southwest Geophysics, Inc., conducted a general background investigation and a geophysical survey of a defined area on and around a known rock cairn on the Rincon Reservation of Luiseño Indians. Background research identified previously recorded historical/archaeological resources in or near the project site and existing cultural resources reports pertaining to the area. Additional research material was also provided by Rincon Tribal representatives. The geophysical work showed that there was disturbance located under the rock cairn. Given the size, shape, and probable depth of this disruption, it was concluded that the disturbance possibly represented a burial. Once a geophysical "feature" or "anomaly" is located, a process called "ground-truthing" begins, where subsurface investigations are conducted in order to verify the location of the feature and explore its character. To test the geophysical results, SRSinc conducted an archaeological excavation over a span of three days. The work revealed a layered rock feature and a small number of artifacts; however, there were no signs of a burial.
A subsequent ethnographic study of known Luiseño use of rock cairns was carried out in order to provide hypotheses for the probable uses of this feature, other than human burial, since this possibility had been ruled out. The information gathered through the ethnographic analysis and research indicated that the rock cairn could be the remains of a boundary or event marker, of a utilitarian pit such as one-time barbeque, or be an integral part of a past traditional ceremony. The function may not necessarily be an "either-or-scenario" as many of the known functions and explanations of cairn use within Native culture can be identified as serving multiple purposes. Looking at ethnographic accounts of documented ceremonies practiced within Luiseño culture, there are a number that include pit excavation. Some ceremonies also included heat or controlled fire in some capacity and may aid in putting this feature into context. There are 19 recorded Luiseño ceremonies recorded in six categories. For these ceremonies, 15 characteristics have been recognized: 9 require pits but of those, only 4 require rocks piled as cairns. Based on the known ceremonial attributes, the heat-affected rocks pieces found in the unit with other possibly ceremonial material (tourmaline, quartz crystal, etc.), and the types of sites located within the region, puberty ceremonies, especially girls' puberty rites, would be the most likely use and it is an interesting possibility.