The final demolition of a former Sacramento police building has been halted again while concerns over an adjacent power station are worked out.

Advantage Demolition was preparing to demonstrate Monday how the last two exterior walls could be pulled down safely next to transformers at a historic power station, now known as SMUD Station A, at Sixth and H streets. The station, whose origins date to 1895, supplies power to up to 40 percent of downtown Sacramento, said Sacramento Municipal Utility District spokesperson Dace Udris.

Demolition of the building at Seventh and H streets began several months ago to make way for a 160-unit affordable housing project being built by the Sacramento Housing and Redevelopment Agency, Mercy Housing California and Mogavero Notestine Associates. Demolition was suspended until Monday, when officials from SHRA, SMUD and the city visited the site to watch a demolition demonstration. The work was halted for further discussion of the process that will be used.

"SMUD is uncomfortable, and I understand why," said Robert Scott of Advantage Demolition, a family-run company based in Eldorado Hills.

The company's most technical demolition jobs are handled by Scott and his uncle Peter Scott, who owns the business. For this building, Robert Scott will put 13 years of experience to work running the excavator, which will pull the concrete block walls into the interior of what's left of the building, he said. The exterior was built to resemble brick.

After Christmas, the Scotts will meet with officials to address concerns and to demonstrate the technique on a roughly 26-foot section of wall facing H Street. The most concern arose over the possibility concrete chunks could fly out from the other wall, which runs along one side of the substation, and hit electrical equipment. The company will install tarps between the substation and the wall to control debris, Robert Scott said.

"I've been in this situation many times," he said. "I have yet to have an accident."

The demolition could be completed within days once the go-ahead is given. Demolishing the rest of the walls should take a few hours. Prepping — installing tarps and making the site safe — will take a day, while cleanup will take two to three days, Scott said.

For years, the building under demolition was the city's patrol station. Patrol officers were based there, while patrol cars were housed in a garage where the federal courthouse now sits. Police administration headquarters were located at the site of the present Sacramento County Public Law Library, said Sacramento Police Department spokesperson Norm Leong.

In 1994, the building was converted into the city's first non-live-in police academy. Forensics also was based there. The building had so much history for Sacramento police that some officers grabbed concrete "bricks" as mementos once it started coming down, Leong said.

"There's history there," he said.

SHRA is overseeing the nine-story project to build one-bedroom and studio apartments, along with ground-floor retail and a clinic, to replace low-income, single-residency occupancy units on K Street Mall or elsewhere downtown and to help develop permanent supportive housing for chronically homeless people. The tenants would be primarily single people with low-wage jobs. Mercy Housing California hopes to establish one-third to half of the units for "special needs" tenants who have been homeless or at-risk in other ways, according to an SHRA staff report.