The non-invasive seismic method of multi-channel analysis of surface waves (MASW) was utilized in conjunction with traditional soil test borings to enhance site modeling for undocumented landfill cells at an existing landfill site in the Atlanta South Metro area. The MASW survey was utilized to delineate vertical and horizontal variations in the area’s subsurface properties in order to provide an indication of the location and depth of cells of buried waste and debris within the site. The data was collected using 4.5-Hz vertical-displacement geophones connected to a 24-channel Geode seismograph, manufactured by Geometrics, Inc. Once collected, the data was processed utilizing the SurfSeis v3.0 software package, developed by Kansas Geologic Survey (KGS), to provide the initial 2-D profiles of the shear wave velocity (Vs) for the subsurface. The 2-D profiles and available boring records were reviewed and compared. Based on the available ground-truthing data, a review of available literature, and the resulting velocities within areas of non-homogeneity in the Vs profiles consistent with landfill cells suggested that the interface between buried waste and undisturbed soils at this site is on the order of Vs=500 ft/sec. The 2-D contoured Vs profiles were used to interpret the anticipated depth to the soil/waste interface at regular intervals across each profile. The 500 ft/sec shear wave velocity, continuity of contour lines, homogeneity within the underlying layers, and congruency between boring data and intersecting MASW lines was considered when interpreting the depth of landfill material. The interpreted depths were assigned coordinates based on surveyed locations of the MASW alignments. Surfer v9.0 software was used to provide a generalized contoured plan view for the site modeling the anticipated location and depth of landfill material. A Natural Neighbor gridding algorithm provided the most appropriate model. Subsequent to the MASW survey, fifteen (15) additional soil borings were preformed along and adjacent to one of the MSAW alignments traversing the site. The data was examined in order to test the validity of the predicted MASW model. The preliminary results suggested that the interpreted model successfully predicted the location of the buried waste cells 56% of the time, and within that 56%, the depth of the waste was predicted to within 6 feet or less.


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