Sound Source Characterization of Down-the-Hole Hammering: Thimble Shoal, Virginia
October 2019 — Virginia, United States
Client: Chesapeake Tunnel Joint Venture
An acoustic measurement study to determine the underwater sound levels produced by DTH (down-the-hole) hammering, a new technology for creating casings for installing dock piles. Measurements were obtained with three bottom-mounted flow-shielded moorings at Thimble Shoal along the Chesapeake Bay Bridge Tunnel in Virginia. The sound footprint was determined for DTH hammering, both with and without bubble curtain mitigation, and compared to regulatory thresholds for onsets of behavioural disturbance and injury to marine mammals. The results suggest that only behavioural disturbance is possible.
