Assemblies

The Pacific Plaza retrofit project was a built through the cooperation of a public/private partnership between the City of Tacoma and the Pacific Plaza Development, LLC. The green roof was established with a combination of sedum cuttings distributed on the entire surface of the green roof and native and adapted perennials seeded into the center of the roof, establishing two separate planting zones. The green roof covers approximately 85% of the roof area and is visible from many of the adjacent buildings.

The climate of the Pacific Northwest drove the design of the green roof and the irrigation system which is fed with harvested rainwater and is not connected to the potable water supply. The green roof is irrigated at the level of the roots through base capillary irrigation which supplies rainwater from a below grade cistern and pump system. Water is delivered to the root zones of the plants on an as needed basis. The different zones are irrigated separately as the water requirements for the two areas are not the same. The Sedum species in the perimeter zone are able to tolerate windy conditions and minimal irrigation and the center meadow zone is more heavily irrigated as it has a greater need for water. The Irrigation system is designed to run only through the months of May-September and is connected to a rain sensor to avoid unnecessary water loss. When the cistern levels are low the irrigation levels are dialed back, and when the cistern is full irrigation levels are increased. The perimeter roof zone, which can survive without supplemental water, can be irrigated to make room for additional rainwater.

The green roof media was mined locally and included TAGRO products made from biosolids and other weed-free gardening components. The green roof in this parking garage-turned office building enhances the downtown area and represents one of the many progressive, green initiatives in this innovative rehab.