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King Pine Tower Braces

Thursday, January 26, 2017

If you have ridden on the King Pine Lift recently, you've probably noticed the braces installed on the bases of towers 4 and 5.

As you may remember over the summer, the top terminal of the Spruce Peak triple chair lift at Sunday River overturned. After further investigation, it was determined that the particular gypsum -based grout used in the foundation anchoring of the terminal had deteriorated, causing it to overturn.

Following that incident, our lift mechanics and a third party professional engineer inspected all of our lifts and found that two, Whiffletree and King Pine, had towers with a similar form of pinning and grout anchoring. As a result, we contracted S.W.Cole of southern Maine to bore into the rock ledge and retrieve a sample of the grout used in the pinning process for composition analysis.

The samples were sent to a petrographic laboratory in Wisconsin, where they were able to determine that the foundations contained a cement-based grout, as opposed to gypsum-based, and therefore not susceptible to overturn. However, throughout the process we found that King Pine tower foundations were susceptible for ice jacking-which occurs when water gets into a the structural support, expands when it freezes, and damages the foundation.

The Whiffletree towers were not found to be susceptible to ice jacking.

The braces that have been installed on towers 4 and 5 of the King Pine lift are rock anchor hold-down frames that affix to the rock ledge underneath the tower foundations. These devices consist of cross beams that are welded to the existing tower and feature 4 William's spinlock mechanical rock anchors that that are drilled into the ground to reinforce the tower foundation. Unlike the former pinning system, the mechanical rock anchors do not rely on the grout for their holding force.