By Seth Daniel
Some 16 cranes sit waiting this week on the Wynn Boston Harbor site.
Hundreds of workers, likewise, are waiting in the wings.
Wynn Boston Harbor folks were counting the minutes Tuesday afternoon and into Wednesday, Aug. 3, waiting simply to get one piece of paper that they said would unleash construction on one of the largest private development projects in the history of the state.
Wynn Boston Harbor officials did receive their Chapter 91 waterways license yesterday (Aug. 3) , and construction on the only resort casino in Greater Boston would finally begin.
The company has been amassing heavy equipment such as cranes and slurry plants on the site for the last week, all with permission by the state. Twelve cranes arrived just this week on the site, and more heavy equipment is expected.
Work is finally slated to start later this week on the Wynn Boston Harbor casino, with some 400 workers converging on the site immediately once the Chapter 91 license is in hand.
Already, work on the site has begun with a great deal of utility construction going on – such as a trench for a large sewer main. All of that work had to happen outside the Chapter 91 zone by the waterfront. However, that restriction is expected to be lifted in grand fashion later this week so that construction, in earnest, can finally start.
Wynn officials are expected to move forward with construction before scheduling any groundbreaking ceremony, though one is expected to take place later in the summer or fall.
One of the first things that will begin is an innovative slurry wall foundation around the entire perimeter of the building site. Instead of digging down three levels and excavating, they will pour the concrete first and then dig out the dirt material – which will have to be taken off site.
Wynn engineer Chris Gordon said one of the first things to do is to build two walls more than 100 feet deep that will anchor into the bedrock. From there, they will begin pouring 20-foot sections of the foundation around the perimeter. Those sections will be deeper around the parking garage area, which is in the center of the building. The outer arms of the building, which will house the retail/function hall parts and the back of the house/mechanical parts, will be build on a traditional slab and won’t require the digging that the garage does.
On the garage section, Gordon said a crane with a grinder attached will dig out the wall area, and the slurry machine will dump the liquid into the hole. The slurry, a liquid substance that acts only as a placeholder, is dumped into the excavation. While the slurry rests in the hole and holds back the earth, steel rebar cages are inserted into the slurry wall. Then, concrete is poured into the slurry.
“You fill the hole with slurry and then you bring in the concrete and start pouring concrete from the bottom,” he said. “The concrete is heavier and the slurry rises to the top and we remove it, filter it and reuse it again. You do that same process in 20-foot increments all over the foundation…The slurry wall process takes less time and gives you a better foundation.”
Once the perimeter foundation is poured, Gordon said they would begin digging out the dirt materials – essentially building a bowl and then emptying it out.
In the garage area, there are four levels of parking, but only three are below grade. Crews will dig out 10 feet of materials at a time, building “pinning walls” on the perimeter after going down each 10-foot mark. Once the three levels of garage are dug out (about 40 feet down), they will build a concrete slab six feet thick at the bottom of the garage. That, Gordon said, would have to be pinned down to the bedrock or it would end up “floating.”
“We will have to secure that slab to the bedrock because it will want to float with the tide,” he said. “The anchors on the slab act like wood screws and go into the bedrock and hold it in place. They really keep the slab from being buoyant.”
That entire process, he said, is expected to take six months.
The parts of the building not covering the garage – which is about half of the building – will not be dug out in the same manner, but will be built on a traditional slab with pilings.