CTLGroup was retained by Zurich Insurance Company to investigate claims that long-term blasting had damaged seventeen buildings in the vicinity of a quarry in the southeastern United States.
In performing this work, CTLGroup reviewed and analyzed thousands of pages of historical blasting records in the form of shot reports and seismic analyses over a thirty-year period of quarry operation. Shot reports provided information such as the blast date and time, blast location, charge weight, delay time, and number of boreholes. Seismic analyses provided the measured ground vibration and air overpressure resulting from the blast event. The data was used to determine the expected ground vibration and air overpressure at the buildings of interest resulting from each blast event. The building damage potential resulting from both single and cumulative blast events was then analyzed.
CTLGroup also inspected each of the buildings to document observed distress. Both nondestructive test methods and invasive exploratory openings were utilized to document the building construction and investigate underlying conditions. Any observed distress was then compared to the calculated damage potential from the blast events to provide opinions regarding causation. A recommended repair scope was developed to address any observed distress, regardless of its cause.
Based on our investigation, CTLGroup also provided expert opinions in a subsequent mediation for litigation.