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Federal Register / Vol. 86, No. 157 / Wednesday, August 18, 2021 / Notices TABLE 1PILE SUMMARY
Socket depth feet ft
Structure
Size and type of pile
Pier Abutment
Pier
Retaining Wall
Wave Attenuator Piles
Rigid Hull Inflatable Boat Fender
Template Piles temporary
Sheetpile Removal

32 or 36-in. diameter steel pile in approximate 38-in. diameter holes
36-in. steel pile in approximate 38-in. diameter holes
H pile inserted in 24-in. diameter hole
24-in. steel pile
24-in. steel pile
24-in. steel pile
3/8-in

30
20
10
20
20
10
0

Number of piles 4.
Up to 18.a Up to 9.a 2.
3.
32.b 20.

a Includes b 16

2 piles as a contingency for design flexibility.
of these piles are removed once they are no longer needed as templates.

The primary source of underwater noise that may result in takes during construction would be from the
installation and removal of piles to support the pier and fenders. Table 2
shows project components and activities
that could result in the take of marine mammals.

TABLE 2PROJECT COMPONENTS: POTENTIAL FOR MARINE MAMMAL TAKE
Potential for marine mammal take yes/no
Project component
Equipment
Pile/Sheetpile Removal

Excavator and loader operated above water
Crane operated above water
Vibratory hammer
Underwater cutting tool 1
Crane operated above water
DTH drill
Impact hammer
Vibratory hammer
Pneumatic hydrogrinder or needle scaler 2
Hoe ram

Pile Installation

Anode Protection
Rock chipping optional

No.
No.
Yes.
Yes.
No.
Yes.
Yes.
Yes.
Yes.
Yes.3

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1 Underwater cutting tool operation, if necessary, would occur on the same days as vibratory extraction. Estimated take associated with cutting tool operation was calculated by utilizing higher underwater source levels associated with vibratory extraction.
2 These tools scrape off surfaces for rust, paint, etc. Use of these tools would be limited and would occur once pile installation is complete. Underwater source levels are estimated at 146 dB at 10m and have been accounted for in the take estimate.
3 Rock chipping may not be necessary. However if it does occur it would occur on the same days as DTH pile installation.

Piles would be socketed in place since the substrate comprises rocky or exposed bedrock. This involves drilling and hammering into the rock to create a socket hole deeper and larger than the pile diameter. The primary technique for creating the socket holes and their piles would be by DTH pile installation.
DTH installation uses both rotary and hammering actions on a drill bit i.e., like a hammer drill hand tool to create a hole in the bedrock or sediment. It uses the rotation of the drill system and a typically pneumatic hammering mechanism to break up rock to create a hole. Since construction techniques could vary depending on specific site conditions, a small impact hammer may also need to be used at the end of the process to firmly seat the pile in the hole. This may require no more than 10
strikes. It is unlikely that a vibratory hammer would be used to install piles.

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Once the pile is set, the remaining void space is filled with a high-performance cement-based sealing grout. Temporary template piles used during construction would be removed with a vibratory hammer or cut off at the mudline.
Approximately one to two piles would be installed over a 12-hour work day. As a precautionary measure, it is assumed that two installation activities would be occurring at the same time i.e., simultaneous. The main method of pile installation would be by DTH. Two DTH systems would be available on site and could be used simultaneously. One vibratory hammer would possibly be used to remove existing piles, and one impact hammer could be used to proof piles.
Rock chipping may be required to ensure accurate pile location and alignment with the sea bottom at pile locations. Rock chipping involves the use of excavators fitted with hydraulic
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breakers or powerful percussion hammers used to break up large concrete structures. If rock chipping is necessary, it would likely occur prior to but on the same days as DTH pile installation.
The project design includes installation of anode corrosion protection for the major submerged steel components. Divers would install aluminum alloy anodes below the waterline by welding and using a pneumatic hydrogrinder, needle scaler, or similar equipment. They would use these tools to scrape rust, paint, etc. off surfaces. This activity would occur only after pile installation is complete. The hydrogrinder or needle scaler would only be used approximately one hour per day over an 18-day period.
Table 3 provides the number of piles and the estimated number of days of installation.

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