Page 20 - Spring 2015

The Underwater sound field from Impact Pile Driving and Its Potential effects on Marine life
The increased use of impact driving to install steel piles for in-water construction has with it a responsibility to assess the possible effects of related underwater noise on aquatic life.
Introduction
Impact pile driving is a method used to install piles for marine and inland wa- ter construction projects using high-energy impact hammers. The installation of hollow steel piles in this manner can produce extremely high sound levels in the surrounding waters (as well as in the air). Given the large-scale development of offshore wind in European waters and plans for such development in US waters, along with an increasing need for upgrades in the in-water infrastructure, there is a growing concern about the potential effect of construction-related underwater sounds on marine mammal and fish populations.
Postal:
TNO, PO Box 96864 2509 JG The Hague The Netherlands
Email:
christ.dejong@tno.nl
Arthur N. Popper
Postal:
Department of Biology University of Maryland College Park, Maryland 20742 USA
Email:
apopper@umd.edu
Peter H. Dahl
Postal:
Applied Physics Laboratory and Department of Mechanical Engineering University of Washington Seattle, Washington 98195 USA
Email:
dahl@apl.washington.edu
Christ A. F. de Jong
The impact hammers (Figure 1) must accommodate piles with diameters typically ranging from ~0.5 to 6.5 m, with increasing hammer energy required for increas- ing pile diameter. Both full-scale observational (Robinson et al., 2007; Dahl and Reinhall, 2013) and detailed (Zampolli et al., 2013) numerical studies suggest that ~0.5 % of this hammer energy goes into acoustic energy that ultimately gets into the water column. Examples of peak underwater sound pressure levels (see Met-
Figure 1. (a) Typical hammer for impact driving of ~1-m-diameter steel piles often used in bridge and ferry dock construction, delivering a hammer energy of ~200 kJ. (b) Typical ham- mer for impact driving of ~4-m-diameter and larger steel piles larger used in construction of offshore wind turbine foundations in the North Sea, delivering a hammer energy of ~2,000 kJ. The piles are enclosed in an IHC Noise Mitigation System.
18 | Acoustics Today | Spring 2015 , volume 11, issue 2 ©2015 Acoustical Society of America. All rights reserved.