Explosive offshore structure removal noise measurements

The underwater structures that support wind turbines and oil drilling rigs must eventually be removed. Explosive severing is a commonly used removal method in which charges are inserted into a pile and placed below the seafloor to sever the pile. The open-water source level of an explosive charge is readily determined from its composition and weight (Urick 1986). However, the sediment and pile absorb much of the explosion’s energy. A recent study (BSEE project M13PX00068) measured explosive removals in the Gulf of Mexico. Peak pressure, impulse and energy flux density metrics were measured with a 12-element, two-dimensional array spanning 90 ft vertically and at distances out to 200 ft. Peak amplitudes, compared with theoretical open-water predictions, were reduced from 76% (75 lb charges) to 54% (200 lb charges). Measured results were also compared to predictions from the UnderwaterCalculator (Dzwilewski and Fenton 2003) that included pile and sediment attenuation effects. It accurately predicted the pro...