A historic palm-covered gem at the corner of Polk Street and Cedar Alley is about to get a major makeover, should the Planning Department approve plans to expand the building. Project sponsor Natoma Architects is proposing to convert the currently vacant structure, which was previously used as office space, into a mixed-use development containing nine new rental units, which would include six one-bedroom and three two-bedroom apartments. According to the preliminary project assessment letter, the units would be be located in a brand-new 14,240-square-foot vertical addition that would rise to 85 feet in height. The 1920 building's second story would still be used as office space, with the ground floor reserved for 1,300 square feet of retail. There's no word yet on when the project would break ground, but Natoma estimates that construction would take a full 14 months to complete. With jackhammers already rattling over at California Pacific Medical Center's massive new Cathedral Hill campus just a block away, it may be time for the residents of Lower Polk to start investing in lavish amounts of earplugs.