A proposal to demolish an office building in downtown Palo Alto and replace it with an office-and-condominiums development that would have more than twice the square footage is raising alarms among residents who believe it will worsen the area's traffic conditions and clash with the adjacent residential neighborhood.

The proposal for 550 Hamilton Ave. is still in its preliminary stage. So far, there haven't been any formal applications or public hearings. Furthermore, for the plan to become a reality, developer C.M Capital Corporation has to convince the City Council to rezone the site to allow the greater density -- a tough sell at a time when the city is trying to limit office space in the city's major commercial areas.

The proposal, which the council will consider on May 16, calls for demolishing the 43,272-square-foot office building, located between Webster and Cowper streets, and constructing two new buildings: one with 57,475 square feet of office space and the other with 57,292 square feet for between 35 and 50 condominiums. The developer is also proposing an underground garage with 297 parking spaces. Because part of the project would be built on what is now a parking lot of 115 spaces (and redwood trees), the net increase in parking space would be 182 spaces.

There is nothing unusual about commercial developers proposing to exceed existing density requirements, but the proposal from C.M. Capital stands out in one respect. Historically, developers looking to exceed zoning regulations seek "planned community" (PC) zoning, which requires an offer of "public benefits" (such as a grocery store, funds for parking facilities or ap piece of art) in exchange for greater leniency in height and density standards.

In this case, however, the site in question is already a planned-community site, and C.M. Capital is requesting that the zoning be changed to "downtown commercial" -- the same designation that exists at an adjacent site. Other parcels around the site of the proposed development are zoned for multi-family residential use, along with one planned-community zone for The Marc, a 12-story residential complex.

The proposed development would be 50 feet tall -- 6 feet shorter than the existing office building, according to a report from the Department of Planning and Community Environment. But while the existing office building only occupies 25 percent of the 57,500-square foot site, the mixed-use development would fill up the bulk of the property, with the exception of a 9,500-square-foot courtyard in the middle. As such, it could have a significant impact on an eclectic neighborhood that includes professional offices, two-story residential buildings, single-family homes and the First United Methodist Church.

The report notes that redevelopment "would result in a much different visual environment from the current development pattern, with properties along Webster Avenue being more impacted by the loss of mature redwood trees and proposed residential building." While normally, buildings that are within 150 feet of residential uses are restricted to 40 feet in height, the city's zoning code allows an additional 10 feet of height for properties that abut a residential "planned community" district, as this parcel does.

The developer's design narrative states that the "overarching goal" of the project's design is to create "a vibrant, mixed-use setting that benefits the immediate neighborhood and downtown Palo Alto as a whole." The zone change, the application argues, "allows the design the flexibility to achieve this goal and to be compatible in both land use and physical context." Each building would have a base element of stone and terra cotta and upper stories that "step back" to minimize the visual impact of the height.

The residential building, which would be primarily located along Webster (with a small portion on Hamilton), would be four stories tall with an entrance from the courtyard. As the building turns from Hamilton to Webster, its massing "breaks up into smaller volumes clad in cement plaster and wood, responding to the scale and materiality of the single-family houses along this street."

The design narrative also states that planters, seating areas and bike racks will be added to make the buildings attractive to pedestrians. The developer also plans to have on-site electric-vehicle-charging stations and a host of green features, with the goal of achieving LEED certification.

The new two-level underground garage would be accessed from Hamilton. The two existing driveways along Webster would be closed off and replaced with a new curb and landscaping.

But while the design narrative stresses that the building will be compatible with the surrounding context, area residents are far from convinced. Earlier this week, 15 residents co-signed a letter calling the proposal "massive," "out-of-scale" and "an intrusion into our residential neighborhood."

"The new construction will increase traffic and population density significantly," states the letter, which is signed by longtime land-use watchdog Elaine Meyer, Roberta Ahlquist, Adolfo Otero Lopez,

Marie Louise Starling Bell, Bill Cane, Bonnie Berg, Chan Kam Chu, David Foster, Jeanette Revelas. Lin Jiang, Linda Otero Lopez, Paul Bundy, Peter Revelas, Stephanie Munoz and Walter Bliss.

"Children from north of University walk and bicycle to Addison School along Webster Street. This project will turn our residential neighborhood into a noisy, congested, dusty, long-term construction site. It will also encourage more development."

The council has also grown exceedingly cautious about new office development, recently adopting an annual 50,000-square-foot cap on new office space in three commercial areas: downtown, El Camino Real and the California Avenue Business District. The project at 550 Hamilton, however, stands just outside the downtown boundary where the office cap applies.

The council will consider the project on May 16 in a "prescreening" hearing, which typically involves comments from members but no formal votes. The discussion is intended to inform the developer as to whether to submit a formal application.