FEATURE
The study was expanded in 20092, emphasizing the
required development of minimization measures to protect fish
species listed under the Endangered Species Act, which has
resulted in costly project delays and has increased project costs
for the California Department of Transportation, transportation
departments and ports on the West Coast. This study is
a good reference on the topic, providing background discussion
on the measurement of sound using the decibel scale, noting
that the reference pressure in air is different than the reference
pressure in water. There is discussion of the logarithmic nature
of the decibel scale, with example underwater noise values from
background, ships, pile driving and explosives use. Definitions
are provided for the three decibel limits normally specified
by regulators: “peak,” root mean square (RMS) and Sound
Exposure Level (SEL). This report did generally discuss recommendations
for underwater noise thresholds for West Coast
fish, but did not mention noise frequencies and how different
fish are sensitive to noise based on audio frequency (periodic
vibration, not time frequency).
In comparison, this topic in the U.K. and Europe is more
developed with a database of findings from many larger projects
and includes underwater noise from multiple sources including
shipping, fishing, oil exploration, offshore wind farms and
marine construction. There are multiple references from the
U.K. that do discuss audio frequency sources and ranges for
frequency detection by various fish and marine mammals, and
duration of the noise, such as continuous pile drilling versus
impact pile driving3.
Permitting and engineering
Most marine construction in the U.S. requires some level of
local, state and federal environmental permitting. In New
England, the issues associated with construction-induced
underwater noise are typically addressed at the federal level, but
frequently are within state specific general permits issued by the
Army Corps of Engineers.
The most stringent standard restrictions on in-water pile
installations are in the current Maine General Permit. The
issue of underwater pile driving noise is addressed by limiting
pile installation to the winter work window or using a vibratory
hammer for installation of wood piles, concrete piles less than
18 inches in diameter or steel piles less than 12 inches in diameter
– with a hammer less than 3,000 pounds and a wood cushion
between the hammer and steel pile. With these methods,
the underwater noise levels must not exceed 187 dB SEL or 206
dB peak, measured from 10 meters away. From discussion with
an New England District Army Corps of Engineers regulator,
TIMBER PILE
UPLIFT ANCHORS
TP-807
TIMBER PILE POINTS
Hard cutting timber pile
points help make any job
run more smoothly and
dependably.
Timber pile points protect
pile tips from failure. Points
will help drive through rubble
and other tough conditions
without undermining the
strength of the pile. Points
are made in one piece of
1/4" low-alloy cast steel.
Advanced Uplift
Resistance Anchors
Our TP-807 timber
anchors are made from
TUFLOY cast steel
(90 ksi tensile, 60 ksi
yield) and are galvanized.
Quick assembly in the
field with just holes
drilled through the pile.
DFP casts integral teeth
into each uplift anchor
to provide extra “bite”
into the timber pile.
A full set is needed for
30 ton uplift and 1/2 set
for 15 ton uplift.
TP-337
PO Box 688 • Franklin Lakes, NJ 07417-0688
201-337-5748 • fax: 201-337-9022 • www.pileline.com
currahee / 123RF Stock Photo
60 | ISSUE 2 2018
/www.pileline.com
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