New marine docking facility, Chignik, Alaska
Details of the project:
Chignik, Alaska, is a remote fishing community located 250 miles southwest of Kodiak Island with a population of about 90 people. Chignik is only accessible via plane or ferry.
Pacific Pile & Marine (PPM) was contracted by the Alaska Department of Transportation & Public Facilities (ADOT&PF) to construct a new marine docking facility that will allow improved berthing and mooring for the Alaska Marine Highway System ferries and other vessels.
The new Chignik Public Dock is an OPEN CELL SHEET PILE (OCSP) design, developed by PND Engineers to provide high load capacity with minimal sheet pile toe embedment. The design can also be modified for increased loading or unforeseen conditions and accommodates for longterm settlement. The OCSP structure was backfilled and vibracompacted.
Thirteen OPEN CELLs were constructed, incorporating 905 sheet piles with lengths ranging from 30 to 75 ft. Additional project elements include a 3-SPIN FIN pile mooring dolphin, five fender systems along the dock face and three new sections of armor rock slope protection surrounding the dock.
The construction of the OCSP structure presented many challenges, mainly due to soft soil conditions. Each sheet had to be anchored to the template to prevent pile slippage or unwanted movement of the sheet prior to it being driven to grade. Additionally, the installation of 75-ft-long sheets in shallow water at the end of the tail walls provided further challenges.
PPM drove the pile using a combination of guidewire support and tiered templates to maintain plumbness and wall stability throughout installation. The design incorporates an existing stockpile of fill, dredged during the construction of the town’s boat harbor in 2012.
Using an existing stockpile of dredged fill provided a cost-effective design element for the new public dock. Additional challenges came to light when the team discovered the specified fill material could not support compaction equipment at the elevation required. PPM worked with ADOT&PF to mitigate the issue by adding a barge load of rock on top of the fill material placed within the OCSP structure.
More information on the Pacific Pile website.