Turner Construction Co. is the general contractor for construction of the $148-million Mirabella Continued Care Community for Pacific Retirement Services Inc. in Seattle.

When complete, Mirabella will be the first new continuing care retirement community opened in Seattle in nearly 20 years. Built in the Cascade neighborhood of Seattle's South Lake Union district, the project is a 13-story, U-shaped structure containing 400 living units including independent, assisted, skilled nursing, and dementia care.

"We are proud to have been selected by Pacific Retirement Services Inc. to construct this important addition to the Seattle area and help the company achieve its business objectives," said Jack Beaudoin, vice president and general manager of Turner's Seattle operations.

PRS marked the state of construction at the two-acre site on Aug. 12, 2006, with a groundbreaking celebration that drew 517 future residents, neighbors, executives, and local dignitaries.

Soon Seattle-based DBM Contactors Inc. was busy on the design-build of temporary excavation support for Mirabella. Shoring design engineer was Ground Support PLLC.

The shoring project required installing 156 soldier piles to a length of 33 feet, 106 tiebacks to a length of 50 feet and 17,000 square feet of lagging. Many of the tiebacks were at steep angles (up to 60 degrees down angle) to avoid deep electrical duct banks along the east, south and west walls.

DBM completed its work in March 2007.

While shoring was under way, work was starting on the foundation itself. The project is split into four slab-on-grade zones or quadrants, each containing one elevator core. The work is progressing sequentially counting down from Zone 4 (the corner of Fairview and Denny) through to Zone 1 (the corner of Fairview and John Street).

Matt footings 5 feet 6 inches thick support each of the elevator cores. Besides the mat footing, additional spread footings and strap beam footings in Zone 3 were poured at the same time, resulting in a pour consisting of more than 1,400 cubic yards of concrete. The contractor utilized two large pump trucks with each pump being fed simultaneously by two concrete trucks. The pour took 150-plus concrete trucks and was completed in about 6.5 hours of continuous placement.

With Mirabella taking up a complete block along with the shape of the building following the perimeter of the block, two tower cranes are needed to complete the work and to reach all areas required. The second crane went up in mid-February.

The project also required construction of a large storm water detention vault in the northeast corner of Zone 2. All roof and exterior water drains from the building go into this detention vault to remove any sediment prior to entering the city of Seattle's storm water system.

In late March, as this story was being written, underground work on the mechanical, plumbing and electrical work was under way in Zone 2. Due to the concentration of systems and vaults in this zone, the underground work is quite extensive and was expected to take around two weeks of production before the slab-on-grade could be poured for this zone. Meanwhile, the first floor was being formed across Zones 3 and 4 and concrete pours were beginning.

Construction is scheduled for completion in the summer of 2008.

Across town, Turner also is serving as the general contractor for the $89-million Harborview Ninth and Jefferson Medical Office Building for King County.

The 14-story, 460,000-square-foot medical office building will house critical public services including medical clinics, research laboratories, medical offices, and coroner services as well as retail space and loading docks for materials management to serve Harborview Medical Center, King County and University of Washington's School of Medicine. The project also includes a four-level, 260,000-square-foot parking garage. Completion is scheduled for March 2009.

This is the third job Turner Construction Co. has done on the Harborview Medical Center Campus and the sixth for King County.