On May 13, 1993, ZymoGenetics began a $25 million year-long renovation of the The Seattle City Light Steam Plant building. The Steam Plant was decommissioned in September, 1987 after years of minimal use, except for occasional firing of the boilers.

Construction was completed in Jun. 1994. On Aug. 1, the ZymoGenetics Lake Union Steam Plant and Hydro House were designated City of Seattle landmarks, and on Sept. 8, ZymoGenetics dedicated Seattle’s historic Steam Plant. The renovated 113,000 s.f. plant doubled Zymo’s existing facility footage.