As engineers-of-record, Coastal Engineering Co. has a long-standing relationship with PMPM, dating back to the award-winning 2012 restoration of the monument’s structural system. Coastal’s structural and historical expertise guided the restoration of the Pilgrim Monument in the direction of a cost-effective, state-of-the-art fiber technology that addressed corrosion-related issues and improved the Monument’s structural integrity. The work also included upgrades to the observation platform and viewing stations. The unique project was performed during the off-season and had aggressive deadlines, all of which were met.
In the inclined elevator project, Coastal Engineering Co. has been involved at multiple levels. The Coastal civil engineering team has developed civil site plans and performed precise field survey layout, the Coastal structural engineering team has designed the foundations and connection points that will support the elevator, as well as the buildings and frames according to the vision of the architect, while the Coastal permitting team has assisted the client through the difficult permitting process.
“The outer Cape surficial geology is essentially a giant sand dune formed from the post glacial deposition of sand and silt from the last advance and retreat of the ice sheet. As such, slope stability and the integrity of the rail support structure were the main considerations of the project.” - John Bologna, P.E., Coastal Engineering Co. President/CEO
The planning process started with an evaluation of the site existing conditions. Cape Cod juts far out into the North Atlantic Ocean and bears the brunt of major storms coming up the Northeast coast. Over the past 100 years, the Pilgrim Monument has stood tall, withstanding the forces from Great New England Hurricane of 1938, Hurricanes Edna and Carol in 1954, and Hurricane Bob in 1991. “The site locus is subject to 138 mph, 3-second gusts of wind and is a designated hurricane prone area,” says Bologna. “The elevator foundation structure had to be designed for high winds and snow using gravity, wind, and seismic specifications from Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-16).”
Helical piles installed up to 45 ft deep will not only support the foundations but also improve the global stability of the site. There are over 50 helical piles associated with the project. Some will be installed at an angle, serving as tiebacks for the tension load produced by the mechanism itself. Others act as conventional compression piles, and still others (at the bottom of the hill) act to resist buoyancy in the event of area flooding.