Level 10 Construction Announces Completion of Benchmarks at 181 Freemont Street

SUNNYVALE, Calif. — Level 10 Construction, the general contractor for 181 Fremont Street, announced that extensive caisson drilling at the site will be completed by July 1 and that excavation of the basement will begin later in July. Level 10 will bring a unique 700B Luffing Tower Crane on site in the fall to help finish the basement construction after shoring is complete. Construction will begin to go vertical at the site during the October to November timeframe.

The 800-foot, 55-story high rise will be the second tallest building in San Francisco, California. It is owned and developed by Jay Paul Company, and includes 404,000 square feet of Class A office space on the lower 36 floors, and 67 condos on the top 17 floors. It is pre-certified LEED Platinum.

Steve DeWees, project executive and manager of Level 10’s San Francisco office, said the 44 caisson shafts being drilled at 181 Fremont are believed to be the deepest shafts ever prepared for a building in San Francisco. Some 23 caissons are currently drilled. Each shaft averages 262 feet and measures 5-6 feet in diameter. Caissons are drilled at such depth because 181 Fremont sits on landfill where the bay used to encroach.

DeWees said Level 10 Construction first drills the caissons into “hardpan” or hard rock and then drills a rock socket for the caisson to be seated. Each caisson shaft takes three days to complete: on the first day, the shaft is drilled; on the second day, debris is cleared from the hole and the rebar cage is set and, on the third day, concrete is poured.

The structural engineer for the caisson drilling is ARUP; the drilling subcontractor is Malcolm Drilling Company.

DeWees said the digging for the basement begins in July and is expected to be completed by November. Erection of most of the basement floors will be done with the help of the 700B Luffing Tower Crane, which will be brought to the site in October.

The 700B Luffing Tower Crane, the only crane of its kind on the West Coast, will remain on site for about a year. With a full height of about 1,000 feet, it is being used for the project because it can handle extremely heavy loads at a very fast line speed. The crane can move over 40,000 pounds in a load and has a line speed of 623 feet per minute. There is one other 700B Luffing Tower Crane in the U.S., in New York City.

Caisson drilling photos courtesy of Level 10 Construction.
Rendering courtesy of Heller Manus Architects.