Steel Sheet Pile Bulkhead – Gales Ferry CT
Allyn’s Point Plant
Gales Ferry, CT
Completion Date: 2004
Total Project Value: $1,200,000
Relevant Project Features:
- Prepared Plans and Specifications for Construction
- Pile Foundation Design and WEAP Analyses
- Prepared Construction Budget Estimates
- Prepared DEP Permit Applications
- Provided Bidding Assistance
- Provided Construction Observation
RT Group, Inc. (RTG) was retained by the Dow Chemical Company, Allyn’s Point Plant to prepare plans and specifications and obtain all local, state, and federal permits for a new Steel Sheet Pile Wall located at their plant on the Thames River. The new Steel Sheet Pile Wall was installed immediately in-front of a deteriorated timber sheet pile wall (i.e., over-sheet project) that was installed in about 1936. Based on its deteriorated condition, granular backfill material was migrating over, under, and through the timber sheets and sinkholes were developing behind the wall. Sinkhole development was particularly troublesome following a heavy rain or storm event.
RTG worked closely with Allyn’s Point Plant personnel in designing the new Steel Sheet Pile Wall, including the relocation of fire protection lines, site lighting, and the installation of a new Marine Facility Office. RTG prepared a series of Design Basis Memorandums (DBMs) for review by Dow Chemical Company staff in order to solicit input and agree on a course of action for each major design element.
The new Steel Sheet Pile Wall was about 340-feet-long, and the sheet piles ranged from about 30-feet-long (in an area of shallow bedrock) to over 50 feet-long (where bedrock sloped steeply toward the Thames River). In addition to the Sheet Pile Wall, about 20 linear feet of seawall was repaired (north end) and riprap armor stone was re-built (on the south end). The Sheet Pile Wall was anchored to a new H-pile supported concrete dead-man anchor system using 1.75-inch-diameter tie rods.
Based on RTG’s recommendation, the new Steel Sheet Pile Wall was coated (the sheets were coated at the mill) with an epoxy paint system. In addition, a passive cathodic protection system, consisting of sacrificial aluminum anodes, was installed after the sheet piles were installed. If properly maintained, the combined paint and cathodic protection system will extend the service life of the Steel Sheet Pile Wall from about 20 to 25 years to at least 50 years.
RTG provided periodic inspection during construction, which included vibration monitoring during anchor pile installation adjacent to several large steel raw material tanks, and troubleshooting as required. One issue that arose was the presence of subsurface obstructions along one segment of the new Steel Sheet Pile Wall and anchor wall. Based on these obstructions (e.g., old timber piles, old timber crib wall), some re-design was required, but the project was completed within the budget established by RTG. The majority of construction was completed in 2003.
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