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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Gay Head Light Move Successful

By Catherine A. Cardno, Ph.D.

A historic lighthouse completed on Martha's Vineyard in 1856 has been successfully moved 134 ft to the southeast to rescue it from an eroding cliff's edge.

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A 200 by 175 ft area around the lighthouse was excavated and dewatered to create the path along which the structure would move to reach its new concrete pad foundation. Drew Kinsman

June 23, 2015—Just two years ago the National Trust for Historic Preservation—a nonprofit organization chartered by Congress to save historic sites within the United States—named the Gay Head Light on the westernmost tip of Martha's Vineyard as one of the 11 most endangered historic places in the country. Today, the lighthouse is no longer endangered, thanks to the efforts of community members who rallied to save it and to the expertise of the team they assembled to move the 465-ton, 159-year-old structure back from the edge of the red, black, and white Gay Head Cliffs. 

The threat to the lighthouse was posed by the erosion of the cliffs, which are themselves significant, having been designated by the National Park Service as National Natural Landmarks in 1965. Rising 150 ft above sea level and providing a cross section of preglacial sediments overlain by fossil-bearing sands, the Gay Head Cliffs constitute the most extensive and scenic exposure of Cretaceous and Tertiary formations of the New England islands and Cape Cod. 

"The cliffs are considered sacred to the Wampanoag Tribe, so we had to make sure that we did nothing that would jeopardize the cliffs," says Len Butler, a building contractor on Martha's Vineyard and the volunteer chairman of the lighthouse relocation committee. "Because not only were we saving the lighthouse, we were trying to save the cliffs as well." 

Bettina M. Washington, the tribal historic preservation officer for the Wampanoag Tribe of Gay Head (Aquinnah) on Martha's Vineyard, explained: "Our Aquinnah traditional cultural landscape covers Nantucket, Nantucket and Vineyard sounds, Martha's Vineyard (Noepe), and the Elizabeth Islands to the eastern side of Rhode Island," she said in written responses to questions posed by Civil Engineering online. "Our stories are bound to this landscape, therefore so is our identity." Of the approximately 1,200 members of the tribe, approximately one-third live on the island.

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Two transverse beams were placed through the clay underneath the original granite foundation of the lighthouse, and then two cross beams were threaded through the soil before the entire assemblage was lifted. International Chimney Corp.

Concern over the extent of the erosion of the colorful cliffs in the town of Aquinnah—known as Gay Head until it was renamed in 1998 to reflect the heritage of the Wampanoag tribe—was first brought to the attention of the town seven or eight years ago, according to Butler. "It was at that time we contacted [Williamsville, New York-based] International Chimney Corporation, which did a feasibility study and came and looked at it and told us that in order to move this structure, we needed at least 30 feet of room from the edge of the bluff to safely excavate."

The move was reminiscent of the relocation of the historic Cape Hatteras Lighthouse, in Buxton, North Carolina—at 198 ft tall the world's tallest brick masonry lighthouse. The lighthouse had been teetering on the brink of destruction—threatened by continuous beachfront erosion—but was successfully moved a distance of 2,900 ft  in the summer of 1999, just weeks before Hurricane Dennis descended upon the Outer Banks. (See "Back from the Brink" by Anne Elizabeth Powell, Civil Engineering , October 1999, pages 52-57.)  

Sourati Engineering Group LLC, from Tisbury, on Martha's Vineyard, was hired in August 2012 to study the erosion rates of the bluff and discovered that on average the area was losing 2 ft of cliff per year. However, in 2013 a 5 ft portion of the bluff collapsed, leaving only 46 ft from the lighthouse to the edge of the bluff, according to George Sourati, P.E., the founder of Sourati Engineering Group. "This accelerated the urgency to relocate the lighthouse," Sourati notes.

The Gay Head Light is a 52 ft tall conical, red brick and sandstone tower with a black lantern and a focal plane height of 170 ft above the mean high water level, according to the U.S. General Services Administration (GSA). Within the lighthouse a round central steel column supports a circular stairway that provides access to the upper floors.

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The support frame, comprising 6 in. by 8 in. I beams, was located immediately beneath the lighthouse’s existing granite block foundation. Derrill Bazzy

The lighthouse has an average radius of 18 ft, and at its base its 3 ft thick walls are located atop a foundation of two circular courses of stepped granite blocks, according to Rick Pomroy, a principal and the owner of East Bridgewater, Massachusetts-based project management firm Pomroy Associates LLC. Pomroy was the project manager hired by the town of Aquinnah to oversee the project.

The town of Aquinnah (which means "end of the island") acquired the property from the U.S. Department of the Interior and the National Park Service for the grand sum of $1 earlier this year after raising the necessary $3.4 million to move the lighthouse. (The National Historic Lighthouse Protection Act made it possible for ownership of listed lighthouses to be transferred from the U.S. Department of the Interior to local governments, agencies, or organizations for the purpose of maintaining and preserving them. The U.S. Coast Guard still retains the right and responsibility of maintaining the aid-to-navigation light that is within the lighthouse, and the lighthouse remains under the jurisdiction of the Department of the Interior and the National Park Service.)

Due to the speed at which the cliffs were eroding near the lighthouse, Sourati Engineering Group was hired to undertake detailed annual surveys for the past three years. Once it became clear that the lighthouse had to be moved—and soon—the Woburn, Massachusetts, office of GEI Consultants was hired to conduct geotechnical analyses of the potential sites to which the lighthouse could be relocated.

"In order to maintain [the lighthouse's] status as an active aid to navigation, which is something we certainly wanted...we had to maintain nearly, if not exactly, the same elevation," Butler noted. "That left us with two potential sites that had enough elevation that we could do it without building it on top of a tremendously high pedestal."

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Once the frame was complete, the lighthouse and its frame were jacked 2 ft into the air so that two travel beams, functioning effectively as train tracks, could be laid beneath them. Derrill Bazzy

Borings were taken of the potential relocation sites themselves, as well as the haul routes that it would be necessary to determine in order to move the lighthouse. The team discovered that the location nearest to the existing footprint "was a much stronger subsoil—it had a greater weight-bearing capacity," than the farther site, Butler says. "The other relocation site was on an ancient dune, so it was a lot looser material [that] would have required a lot of overdigging and filler," he noted. "Not only was that a longer distance, it would have been more costly in terms of site preparation."

"Our geologist [Byron Stone, Ph.D., from the East Hartford office of the U.S. Geological Survey] realized by looking at historic data of recession in different areas of the cliff that there was what he has called a red spur of clay, a very stable clay formation of early Cretaceous deposits that was almost like a spine that ran through the cliff," Butler says. This line of red clay "now has a bit of a prominent point in the cliff, and the erosion is to the north and south of that," Butler explains. 

Erosion along the line of red clay was less than 6 in. a year, whereas the areas to the right and left of the spur had averaged a loss of about 1 ft per year, with a 5 ft loss within one year occurring just two years ago. "It became pretty obvious to us at this point that this was where the relocation was going to be," Butler says. It is hoped that the new site of the lighthouse will remain stable for 150 years.

Once the new location for the lighthouse was determined-and the 129 ft long route to the site was deemed capable of supporting a structure weighing close to 500 tons—preparations for the move could begin. 

Sourati and his team designed the excavation and the dewatering system necessary for the move path, as well as the lighthouse's new concrete pad foundation and the curved retaining wall that is located behind the lighthouse. The overall disturbed area for the excavation was 200 ft in the length, the bottom of the excavation measuring 175 ft long.

The team was asked to excavate the minimal amount of soil necessary for the move to protect the cliffs, both for the Wampanoag Tribe and because undisturbed cliffs would be likely to erode more slowly than disturbed ground. As such, the entire excavated site measured only 0.7 acres, "which was a challenge," Sourati notes.

The lighthouse was excavated down to the base of the existing granite foundation, and then the team stepped back 4 ft and excavated down another 4 ft, according to Jerry Matyiko, owner of Expert House movers of Maryland, who performed the move. (The International Chimney Corporation was the contractor for the project, prepared the lighthouse to be moved, and performed the structural engineering for the move itself.)

In all, "[the bottom of the excavation] was about 10 ft deep, 55 ft wide, and 175 ft long so that we could get all of our move steel and move apparatus around the lighthouse, and create the work area that we could get underneath the lighthouse," Pomroy notes. (This also included space for the new concrete pad foundation at the lighthouse's new site.) 

"The hardest part was excavating out from under [the lighthouse] without it settling," Matyiko says. "We were fortunate with a good clay that stayed damp the whole time, though one side was a better clay than the other."

During the excavation, two transverse beams were placed through the clay underneath the original granite foundation of the lighthouse and then two cross beams were threaded through the soil and put into place. "We had surveyors give us four perpendicular lines so that we could drop plumb lines down and make sure our trenches were straight so that [the lighthouse] wouldn't settle," Matyiko notes. At this point, jacks were placed so that the lighthouse could be jacked up and the remaining soil excavated and beams placed underneath it.

After all of the beams for the lighthouse's support frame had been threaded into place, the lighthouse was locked into place. The support frame was located immediately beneath the existing granite block foundation and was composed of a layer of 6 in. by 8 in. I beams, referred to as needle beams, which were placed perpendicular to and atop a layer of 16 in. by 12 in. transverse beams (the first beams placed), which themselves were perpendicular to two dual sets of double W24x162 main beams. 

As the support frame was built, the soil was carefully excavated in 4 ft sections so that jacks could be placed and pressured up to take the load of the lighthouse during the excavation work, Matyiko explains. Once the frame was complete, the lighthouse and its frame were jacked 2 ft into the air so that two W14x145 travel beams with hardened T-1 steel welded to the top—functioning effectively as train tracks—could be laid underneath the lighthouse and its support frame and atop a double layer bed of 6 in. by 6 in. hard wood oak timbers. The framework supporting the lighthouse was then slowly pushed along rollers positioned atop the travel beams and below the main beams of the lighthouse's supporting frame. 

The entire traveling framework had to be precisely placed because, once in motion, there was no opportunity to turn the load—it had to move in a perfectly straight line, along perfectly aligned, perfectly parallel, and perfectly angled tracks, according to Butler, who described the lighthouse's supporting framework in a video located on the lighthouse's website. Indeed, the tolerances for the tracks were a mere 1/8 in., according to Matyiko.

Keeping the lighthouse perfectly stable during the move was the key to success.

"Probably the biggest challenge is trying to remove the unknown or unexpected conditions that can occur along the haul path during the move," says Douglas Aghjayan, P.E., G.E., M.ASCE, the project manager from the Woburn, Massachusetts office of GEI Consultants, Inc. "Once the lighthouse starts its move, the grades have to stay the same and the lighthouse can't change direction to go around poor soils."  

"The first day we went 52 feet," Matyiko says. "The next day we unbolted the [travel] beams that were originally on, sort of leap frogged them around front, bolted them up, and just kept on going until we got to the new site." The lighthouse was moved in just 2 ½ days. (See time lapse photography of the move here.)

During the move, the door and windows of the lighthouse were braced with concrete blocks so there was no possibility of movement or shifting during the move. The upper portion of the lighthouse was protected with a so-called wooden and cable "corset" during the move, in which wooden posts attached to plywood were wrapped tightly with cables. A second, similar corset was also wrapped around the two stepped layers of the granite foundation. 

"We also added two I beams through the center of the lighthouse, up about 5 feet from the floor, to grab the interior cylindrical column that supports the lighthouse floors, as well as the circular stairs going up," Pomroy says.

A concrete pad is the new base for the relocated lighthouse, atop which the original granite block foundation and the lighthouse now rest. "The lighthouse will keep as much of the old foundation as is feasible, but it will sit on mortared brick infill that rests on a 32-foot-square reinforced-concrete mat," Aghjayan says. "The infilling is necessary so that the lighthouse remains at the same elevation," he notes. "Once the backfilling and landscaping around the lighthouse are complete, the top 12 in. of the original granite foundation blocks will be visible, which will actually be a nice visual feature that was not there before." (Settlement of the lighthouse over the years had concealed the granite foundations from view; they were discovered as plans to move the lighthouse progressed).

To protect the future of the site, GEI observed and documented the soil types and in situ densities of the soil layers as they were excavated, so that the soils could be segregated and stockpiled by soil type during the move. "The underlying soil conditions around the lighthouse and along the haul path are fairly complex for such a small area," Aghjayan says. With the lighthouse established in its new site, the excavated soils were returned to the ground in the reverse order that they were removed. 

The move was completed on May 30 and come July, the Gay Head Light will once again be turned on.

 

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