The return of marine borers to New York Harbor has had devastating consequences to many of New York City's waterfront structures that are supported by fast deteriorating timber piles. In recent years, New York City Economic Development Corporation (NYCEDC: New York, NY) has responded by developing a waterfront management and rehabilitation program for its piers and wharves including the St. George Fishing Pier's Pier 1; just steps away from the Staten Island Ferry.
As part of their recent redevelopment of the Staten Island Ferry Terminals that connect with the southern tip of Manhattan, NYCEDC deemed that the 60+ year-old Saint George Fishing Pier required below deck timber pile rehabilitation/encasement due to years of extreme marine erosion. A key component of a larger renaissance of St. George’s wharf, pier, and bulkhead properties, the refurbishment and stabilization of the 845-foot-long pier would ensure the continued opportunity for the public to catch bluefish, flounder, blackfish, porgy, and striped bass from the shoreline that feeds into Upper New York Bay.
To determine the scope of restoration and most efficient construction solution, Turner Construction, in behalf of NYCEDC, retained the services of Pennmax Engineering (Pound Ridge, NY) to provide underwater inspection and Bid Documents for the repairs. Based on their assessment of encasement repairs required to prevent future deterioration and extend the life of the structure, Pennmax specified 121, twenty-foot long, stay-in-place FRP (fiber-reinforced polymer) pile jackets which would be filled with lightweight concrete.
According to Pennmax's principal owner John Pensiero, "The most critical performance spec was durability to extend the life-cycle integrity of the concrete. We chose a stay-in-place form to provide additional durability, protection, and economic efficiencies since no stripping was required. We also specified a 1/4-inch form thickness to withstand ice / debris impact forces and prevent erosion of the concrete from tidal action."
The NYCEDC approved the Pennmax drawings for the project and awarded the contract through national general contractor Turner Construction (New York, NY). Trevcon Construction Company, Inc. (Liberty Corner, NJ) was selected to perform the underwater construction and Molded Fiber Glass Construction Products (MFG-CP: Independence, KS) was selected to satisfy the project specifications for the FPR pile forms. Because of the underwater construction of the pile restoration; Pier 1 will remain open to the public during construction. The project began in October 2008 and is scheduled for completion in summer 2009.
PILE JACKET PERFORMANCE / SPECS: To help restore the structural integrity to the deteriorating piles, MFG-CP, a division of Molded Fiber Glass Companies (EST: 1948), met Penmax's performance specs in providing a structurally stronger single seam FRP solution designed to leave in place - which meant no removal assembly time.
Made from chop strand mat and woven roving, the two materials provide better physical properties so the jackets meet/exceed specifications vs. gun-roving/chopper gun applied which is not as strong. The resulting FRP composition benefits provide resistance to abrasion while adding structural stability and impact resistance when concrete or grout is properly placed in the form. Additionally, they are chemically resistant to acids, alkalis and most solvents and are durable in seawater.
Pier 1 / Pile Jacket Specs: Thickness: 1/4-inch thick (vs. 1/8” standard) Diameter: 30 inches Length: 20 foot lengths Weight: 400 lbs. per form
According to Pensiero, "Because the forms extend up twenty-plus feet and would initially contain fluid concrete, they had to be strong enough to endure the concrete pumping operations and prevent blow-out. MFG-CP's pile forms m the required thickness and tensile strength to ensure that they wouldn’t blow-out during the pour."