Wrecking Corporation of America is nearing completion of one of the largest demolition projects in the Washington, D.C., area.
As part of the redevelopment of southwest Washington, D.C., and to make room for the new 2.5-million-sq.-ft. (232,258 sq m) mixed-use development called Waterfront, the general contractor, Clark Construction Group, has hired Wrecking Corp. to perform the demolition and earthwork for the project located at M and 4th streets on the Potomac River’s Washington Channel.
Alexandria, Va.-based Wrecking Corp. started the demolition project in November 2007. Wrecking Corp. will be finishing the job by removing the last of the footings, finishing concrete crushing, working on the foundations, and performing more earthwork. Some final work also will be performed around the entrance to the Waterfront-Southeastern University Metro Station.
Terry Anderson, Wrecking Corp. executive vice president, said that the project will be “substantially complete going by May.”
The old Waterside Mall, a four-story, heavily reinforced structure consisting of 1.3 million sq. ft. (120,774 sq m) of concrete, has been razed.
“It was one of the hardest we’ve taken down in a while,” admitted Anderson. He is baffled as to why a decades-old mall would have been built with heavy 20-in. (50.8 cm) floor slabs when the standard is 9 in. (22.8 cm). Workers had to remove 2,240 lbs. (1,016 kg) of rebar that was 1 to 1.5 in. (2.54 to 3.81 cm) thick. “We had to fight down every step of the four-story structure.”
The structure was not only difficult to take down, but it also was the largest contiguous building the company has taken down in the Washington, D.C., area.
“When we [demolished] the Washington Convention Center at 800,000 square feet, it seemed big,” Anderson said, “but 1.3 million square feet is massive.”
For the demolition work, Wrecking Corp. made use of an ultra high-reach excavator, which was a 100,000-lb. (45,359 kg) Komatsu PC400 with an 85-ft. (26 m) boom and a 5,000-lb. (2,268 kg) universal.
Kinshofer dedicated shears with 360-degree rotation were used for cutting steel. The shears were recently purchased by Wrecking Corp., and Anderson said that the shears have enabled operators to “work comfortably next to a building.”
With the advances in equipment and technology over the years, some might consider using a wrecking ball for demolition antiquated — not Anderson. On this job, the company makes use of a 90-ton (82 t) truck crane with a wrecking ball.
“It never breaks,” said Anderson. “There is nothing better than gravity, and it leaves a small carbon footprint.”
Additional equipment used for demolition include a 140,000-lb. (63,503 kg) Caterpillar 365 track-mounted excavator, three Hitachi 450 excavators with Brokk bucket attachments, and four Hitachi 330 excavators with attachments, such as concrete pulverizers and demolition hammers. The company also has three Cat 973 track loaders on hand for moving debris.
To break the large slabs and footings, a variety of powerful hammer attachments were needed. Wrecking Corp. has a collection of demolition hammer attachments: 3,500, 5,000, and 6,000 ft. lbs. The largest is an 8,000-ft.-lb hammer that is attached to a 70,000-lb. (31,751 kg) excavator. In addition, one of the hammers was mounted on a Gradall excavator, which “can get into tight areas,” said Anderson.
Since demolition is occurring in these tight areas and in proximity to structures that will remain after the job is finished, extraordinary precautions must be taken. Anderson described the site as being “hemmed in on three sides.” Sometimes, in this type of environment, work is referred to as “hand separated,” which means the job is very labor-intensive. Anderson explained that hand-separated means selective removal of structures and structural parts that often involves using small equipment.
For this type of work, Wrecking Corp. has on hand three to four Bobcat skid steers. The company also is using Takeuchi mini-excavators with hydraulic hammers up to 750 ft. lbs., which Anderson said are great for performing selective slab demolition. This job included selective demolition of 19,000 slabs.
One of the labor-intensive aspects of the project included work around a deli attached to the Safeway grocery store. The deli had to be preserved, and certain areas of the building to be demolished were on top of the deli. The parts that were demolished had to be surgically removed; this included two levels of concrete deck. “We had to saw cut a 20-inch slab of concrete,” explained Anderson.
In addition, there were two unoccupied office towers and an active metro station tunnel entrance at 4th Street that the contractor had to take special care with. The entrance to the metro was roughly 70 ft. (21 m) away from the razed structure.
“The metro creates a vacuum, and if the wind is blowing in the wrong direction, the dust gets sucked down,” said Anderson.
To control the dust, Wrecking Corp. rented a DustBoss for dust mitigation.
“Concrete creates dust,” Anderson said. “We’re constantly fighting dust; it’s part of being a good neighbor.”
The DustBoss is hooked up to a fire hose and a generator while an oscillating fan spreads mist. Anderson was so impressed with the DustBoss that the company is considering purchasing a couple of the units.
Wrecking Corp. will be self-performing concrete crushing and recycling on the job site. An Extec C10 crusher is being used to crush 70,000 cu. yds. (53,519 cu m) of concrete. The crushed concrete will not be a screened product. About half of the crushed product will be used on site as non-structural fill. Also, the general contractor will use the crushed concrete for backfill.
Excavation for the new Waterfront development is currently under way. Earthwork consists of 75,000 cu. yds. (57,342 cu m) of excavation and 35,000 cu. yds. (26,759 cu m) of backfill. Workers are making cuts of 12 to 15 ft. (3.6 to 4.6 m) and are going to subgrade as well at various depths. According to Anderson, crews have to be very careful when performing the excavation because an existing 8 ft. (2.4 m) storm sewer that is L-shaped and contains two 45-degree turns cuts right through the site. This storm sewer will remain as the new development is being built.
The amount of the contract awarded to Wrecking Corp. hovers around $5 million. Anderson personally budgeted and closed the deal. There are multiple supervisors on the job site, and Anderson is daily costing the job. “You’ve got to be out there on top of it,” he said.
To determine if the work being performed is cost effective, the entire work site is monitored by Sky Cams set up on adjacent towers. “It is a great tool,” Anderson said. “The site changes rapidly, hour to hour, and we are making sure we’re efficient.”
The Sky Cams also ensure that safety regulations are being followed. “Safety is paramount on a job like this … Safety is a religion,” he said.
In the end, Anderson believes that the key to success on any project is communication. There has to be communication among the on-site workers and supervisors as well as upper management. CEG