Concrete cutting recently played a key role in a major remediation effort at a rocket propulsion testing facility in California's Santa Susana Mountains. Overlooking Simi Valley and the San Fernando Valley, this 2,800-acre facility is situated in an area where natural beauty and a rich wildlife habitat coexist with leading edge technology. Since 1950, rocket engine tests conducted at the facility have allowed for the development and testing of engines used in almost every space program, from the earliest satellite and astronaut launches through the Apollo program and on to the Space Shuttle.

Rocketdyne Propulsion & Power, which merged with The Boeing Company in 1996, led much of this historic testing beginning in the mid 1950s. The first engine tests at the site launched an era of propulsion innovation that is the hallmark of Rocketdyne. Since the company was founded in 1955, Rocketdyne has evolved into a global leader in applied power, from the world's most sophisticated aerospace propulsion systems to space-borne electrical power.

Now decades later, the Safety, Health and Environment Affairs team at Boeing is leading a multi-million-dollar program to clean up environmental contamination that resulted from these historic operations. This thorough remediation aims to restore the site's natural environment and ensure the health and safety of the company’s workers and neighbors.

As part of the remediation program, Boeing planned the demolition of a concrete building that housed a nuclear reactor used in the space program during the 1960s. The upper portion of the building would be demolished with hydraulic hammers and excavators. But at 40 feet below grade, the concrete was "activated" from close contact with the nuclear reactor. That area of concrete, which formed a protective barrier that absorbed most of the radiation, had been bombarded with radioactive particles that were still present in the concrete as low-level radiation. A more careful method would be required to cut this concrete into 20,000-pound pieces while ensuring that no radioactive dust be released into the atmosphere. The only solution for completing the demolition without the release of dust was to specify precision cutting with diamond tools.

Acting as the general contractor on the job, Boeing was in charge of selecting a specialty contractor to perform the sawing and drilling needed to dismantle the structure's walls and slabs. The sawing and drilling operation was part of a separate contract and only a select list of qualified contractors were allowed to bid. Soundness of technical approach, cost, schedule, safety and relevant experience were used as criteria to award the contract. In the end, Boeing chose CSDA member Concrete Coring Company-Los Angeles (CCCLA) of California to perform the sawing and drilling on this sensitive site.

Boeing devised a cutting sequence for removal of the building components. Sawing and drilling efforts were to begin at 38 feet below grade and extend down to the 55-foot level with the removal of a 3-1/2-foot-thick slab. The walls and slabs were heavily reinforced and their thickness ranged from 18 to 55 inches. The plan called for cutting 3,700 square feet of concrete and core drilling 120 pick holes for rigging, all to be done in eight weeks.

CCCLA began initial preparations in July 2004. First, a complete plan and schedule were submitted. The building was set on a solid sandstone base, and specifications required that no cutting water be allowed to seep into the stone surrounding the structure. CCCLA set up water containment plastic and gutters to keep all cutting water flowing back into the structure. All slurry was to be recycled and the clean water re-used. Job site safety training, radiation training, and respirator and fit testing were conducted. Fit testing included a physical check of the operators' lung capacity and ability to function while wearing a respirator as well as a technical check to ensure the respirator was working properly. Special care and methods were planned to protect the area from radioactive release into the environment.

CCCLA began the dismantling from the top down. First, operators wall sawed the 18- to 24-inch-thick vent stack. Special rigging was attached to the sections for safe lifting via crane. Next, they proceeded to cut the ceiling slab of the pipe chase room, an area into which pipes and vents emptied. To allow for rigging, operators core drilled pick holes 1-1/8 inches in diameter, 30 inches deep. The pipe chase was next to the main room that had contained the reactor and had a 2-1/2-foot-thick ceiling. This concrete contained #7 rebar, double mat with 6-inch centers. The ceiling slab was shored from below and cut in an order that provided complete safety. CCCLA cut the ceiling using a Pentruder 4-speed, 400-cycle wall saw with a 66-inch-diameter blade from Diamond B.

Operators then wire sawed the 3-1/2-foot-thick upper walls using a new wire saw from Golz. CCCLA modified the Golz KS 600 wire saw to equip it with a 20-HP, 400-cycle drive with auto feed control. The saw had a unique guard that allowed full coverage of exposed wire for safety. As a secondary safety measure, ¾-inch plywood was used to protect workers.

After removal of the ceiling, operators cut the 2-foot-thick lower walls from the inside using a Diamond Tech 400-cycle wall saw. The walls were cut just short of full depth to contain the slurry inside the structure. Each section was rigged before the final cut was made.

Flat sawing was used to separate the 2-foot-thick slab on grade. Again, operators completed the cut just short of all the way through to keep from contaminating the sandstone below. Flat sawing was performed with a Mercury 4-speed, 65-HP flat saw with blades up to 54 inches in diameter.

Meanwhile, the reactor cell walls in the adjacent room were being wire sawed at the same time as the pipe chase room work. Wire sawing of the 30- to 55-inch-thick walls and removal went like clockwork.

After the cell walls were cut, the next task was to cut the slab directly below where the reactor had been positioned — the most highly activated part of the structure. Operators carefully stitch drilled the 3-1/2-foot-thick slab on grade using high horsepower 400-cycle drills. The coring was stopped short of the bedrock but went through the bottom mat of steel. An excavator was used to pull the pieces free.

The project unfolded smoothly despite several complications. The work area was very tight and only three saws could be used at a time for safety reasons. The presence of low-level radiation forced operators to wear Tyvek suits and gloves at all times, which was uncomfortable in the 100-degree heat. The work site was 55 feet below grade and required daily inspection of the excavation for safety. All the water used for cutting had to be contained and recycled. All blocks had to be cleaned and wrapped before being lifted out of the hole, causing some delays.

Safety was the number one concern on this project and everyone on the job site adhered to strict safety requirements. Because of the tight work area, CCCLA had to take extra measures to protect all workers. Remote control/automatic feed of all cutting equipment was used. Fall protection, including safety cables and harnesses, was needed for working on the ceiling. With the high temperatures, frequent water breaks were required to keep operators hydrated.

In the end, operators line drilled 475 5-inch-diameter cores 3-1/2 feet deep, drilled 120 1- to 6-inch-diameter cores for pick holes and drilled 100 6-inch-diameter cores for overcuts and water control. Operators also cut 3,700 square feet of heavily-reinforced concrete. This totaled close to 1,000 tons of cut concrete, which was removed by crane.

The project was accomplished in 39 working days, one week ahead of schedule, with four operators and two apprentices on the job. After a complete survey of the site, the Department of Energy concluded that no contamination was released into the surrounding sandstone.

With a high level of professionalism and cooperation between Boeing, CCCLA and the crane company, the project was completed safely and within budget. "Our operators performed the work to the highest level of professionalism," said Dennis Richens of Concrete Coring Company-Los Angeles. "We worked very well with Boeing. That teamwork and cooperation made the job happen."

Richens believes that his company's technical approach, experience and safety record earned them the job. CCCLA will perform sawing and drilling of a similar scope on two more buildings containing radioactive elements as a change order to this contract.

Founded in 1961, Concrete Coring Company-Los Angeles operates 25 trucks with 37 employees. CCCLA has partners in most states to take on the largest of jobs. Their line of 400-cycle equipment performs the following applications: core drilling, flat sawing, wall sawing, hand sawing, grinding, grooving, wire sawing and demolition. The company specializes in large and deep coring and deep wall, wire and flat sawing. CCCLA is a charter member of CSDA.

RESOURCES

General Contractor:
The Boeing Company
Sawing & Drilling Contractor:
Concrete Coring Company-Los Angeles
Paramount, CA
Methods Used:
Wall Sawing, Wire Sawing, Core Drilling
Tel: 562-634-4021
Fax: 562-634-2305
Web: www.concoring.com
e-mail: dennisr@concoring.com