Scope and field context
Project scope and field context
GeoView and ATI Drilling provided Geophysical Services and Geotechnical Drilling to Assess the Areas of Expansion of the Orange County Convention Center GeoView completed a Geophysical Investigation at the Orlando County Convention Center (OCCC) in Orlando, FL. The investigation was performed on the east and west sides of the existing facility in areas where a major expansion is planned. Ground penetrating radar (GPR) and Multichannel Analysis of Surface Waves (MASW) were used to evaluate near-surface geological conditions in the two planned areas of expansion (see map below). The investigation was designed to identify buried potential karst (sinkhole)-related geological features within the two areas. ATI Drilling provided Geotechnical Drilling services. A total of 21 SPT Borings were performed to depths ranging from 25 to 75 feet. The purpose of the Geotech Drilling was to help confirm the results from the geophysical investigation and to provide an overall evaluation of site conditions. Asphalt and Concrete Coring and Patching: at 15 locations water samples were collected. As part of the water sampling effort coring (with associated patching) needed to be performed in the asphalt and concrete. Utility Location and Designation was provided using GPR and EUL (Electronic Utility Locator). This was done to identify any underground utilities or other obstructions at all planned drilling locations. Results of the GPR survey identified a relatively continuous GPR reflector at a depth range of approximately 8 to 16 feet below land surface (bls) across the project site. This reflector most likely corresponds to the lithological contact associated with the surficial sand (SP) stratum and underlying silty sand (SM) stratum that was identified in the SPT borings. This GPR reflector was continuous and near-horizontal and did not indicate any type of sinkhole activity within the near-surface soils at the site. Results of the MASW Survey indicate the presence of three seismic layers which in order from shallow to deep were moderate velocity, low velocity and moderate to high velocity layers. The upper layer is represented as cyan to green colors with shear wave velocities ranging from approximately 800 to 1,300 ft/sec. The second layer is considered low velocity and represented by cyan to dark blue colors on the MASW transects with shear wave velocities ranging from approximately 500 to 800 ft/sec. The third lowermost-layer is considered to have a moderate to high velocity range as represented by green to orange colors on the MASW transects with shear wave velocities ranging from approximately 1,300 to 1,800 ft/sec. This layer continues to the maximum depth for the MASW results (90 ft bls). Both the second and third velocity layers occur within the interbedded sequence of sands, silts and clays as identified in the SPT borings. Possible karst-related anomalies were identified on three of the MASW transects. The anomalies were characterized by a continuation of low-velocity sediments to the maximum depth (90 ft bls) of the MASW results. These deeply occurring low-velocity areas are considered to have an elevated probability for being representative of potentially unstable buried karst features. SPT borings were performed within each of the anomaly areas. Zones of low blow count and weight of hammer (WOH) were identified at depth ranges of 40 to 70 ft at each location. MASW was considered to be successful in identifying buried karst features are the site.