|
| Castillo de San Marco
during construction. Photo taken from a basket suspended from
the crane. The new roof underlayment is going in one section
at a time. |
The Castillo de San Marcos in St. Augustine Florida is an incredible sight.
Built between 1672-1695, the fort was an outpost
of the Spanish Empire, guarding the first permanent
European settlement in the continental United States.
It is the
oldest and largest fort in the United States. This was a unique restoration
project due to the difficulty involved in working on it caused by
the surrounding moat and way wall.
 |
| Some of the cannons
at Castillo de San Marco are valued as high as $250,000. |
The fact that the entire area is historic and sacred ground—an
Indian burial site, typhoid fever grave site and a 300 year old fortification—made
moving a 360 ton crane onsite a very delicate challenge. The 90,000
square foot concrete terreplein that had been poured on top of the
casements in the 1930s had to be removed and replaced with a modern
multi-layer roofing system and a new multi-layered concrete deck.
Twenty-five historic cannons, mortars, and gun platforms,
some weighing 8,000 pounds had to be remved, stored and then replaced.
Restoration of historic coquina with Jahn
Mortar was also part of the process.Everything had to be moved
270' by crane within
a very short period of time. The removal of the concrete slab made
tumbling the 6' high
and 5' thick
solid coquina parapet into the moat a possibility. Ancient sand
fill that had washed out left 5' by 30' cracks
under the old concrete deck. The project involved a lot of asbestos
and concrete demolition and we met with the client on a daily
basis to determine which part of the tourist attraction could
be opened to the one million plus yearly visitors.
 |
| Site prep and crane set up at Castillo de San
Marco, National Monument, St. Augustine FL |
To complete the work we installed a 400 yard crushed limestone road leading
from San Marco Blvd. We installed a 4' thick pad (crushed limestone)
base to set the 360 ton crane on top of the palisade. It sank several
feet into the ground. We had to disassemble it, move it, and install
another 5' (thick) layer of crushed limestone so the crane would
set up on top of the palisade.
The palisade, or high ground around the fort, is a Historic American Indian
burial ground so we were unable to dig down into the palisade to
build a foundation for our crane.
Because the grounds around the
fort are also a historic typhoid fever burial ground we were not
allowed to dig down more than 6" deep. In spite of these constraints
we finished on time and within the NPS budget.
Protective scaffold was installed around and over the edge of the scarp walls
to protect the fort. "The
approach to this project, like all of our projects, is to put together
a team of craftsmen who are dedicated to the craft and the task
at hand."Specially made Dura-Base Mats used by the petro-chemical
industry to drive very heavy vehicles over marshland was used to cover the crane pad and keep the crane from sinking
into the ground. Two layers were used under our crane, and below that 8 feet of crushed limestone.
A simular ground cover was used under the base camp and
staging area. When the restoration work was complete the crushed limestone pad and road were completely removed.
|
