Application of Surface Geophysics for Providing a Detailed Geotechnical Assessment of a Large Resort Development Site in Anguilla, BWI

N.S. Nettles & Associates (NSN) has completed extensive geophysical investigations that have guided engineering practices for a resort community in Rendezvous Bay, located in Anguilla, BWI. Located in a modern carbonate depositional environment, the project site is characterized by surficial and sub-surface karst features that were of concern to the geotechnical engineer for structural stability issues and proper design criteria. Diverse technologies were used including Multi-Electrode Resistivity (MER), Continuous Resistivity Profiling (CRP), and Multi-channel Analysis of Surface Waves (MASW). Resistivity techniques allowed for differentiation of geologic units and the identification of karst features and sub-surface anomalies. To determine sub-surface density variability, MASW transects were performed. This multi-method approach provided confidence in the location of anomalies that were later targeted for drilling practices. Borings, including Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), and rock cores were used to investigate anomalies and calibrate the geophysics. Additionally, a stagnant salt pond was mapped using CRP and MER to determine unconsolidated sediment thickness and the competency of underlying limestone. Results provided accurate volume calculations for dredging, the first phase in the transformation of the hypersaline pond to a functional marine habitat. Combined results have provided the geologic framework for engineers to implement a successful construction strategy for the Rendezvous Bay Resort.