In downtown Riverside, CA, Tho sand Oaks-based developer Moshe Silagi, with contractor Snyder-Langston, recently topped-out the 10-story Regency Tower complex on the corner of 10th and Orange streets. With three levels of parking underground and some 260,000 square feet of office space above, the building will be one of the tallest in the area at 155 feet. About 60,000 cubic yards of earth was excavated and off-hauled in some 4,000 truck loads for the parking structure. The building was recently sold to the County of Riverside to become the new headquarters of the District Attorney's Office. The high-rise project is the first major privately owned building to be constructed downtown since 1991. The tower should be ready for occupation within two years.