City budget officials have prepared a projection that shows it could take both a sales tax and property tax increase to fund a list of Lawrence Police Department facility and staffing needs that have grown to $42 million.

Now, we’ll see if the idea sets off any red lights and sirens with city commissioners who are working to put together a 2013 city budget.

“I sure would like to see us do this in a way that is less impactful to the taxpayers rather than doing this all at once,” Mayor Bob Schumm said.

But last month city commissioners asked staff members to produce a report that estimated how much the Police Department would need to meet its most pressing facility and staffing needs. A new report by City Hall budget officials does that, and presents at least one funding scenario. Here’s a look:

• A previously discussed police headquarters building is still anticipated to cost about $30 million, but now staff members have included an additional $12 million to add 46 positions to the city’s police force over the next four years.

• To pay for the $42 million price tag, the city report says a new 1 percent sales tax may be needed. The tax, which would require voter approval, would sunset after it collects about $32 million. City officials estimate the tax would be in place for about 14 months.

• In addition to the sales tax, a property tax rate increase of nearly five mills would need to be implemented to pay for the additional police officers. The current scenario pegs the increase at 4.7 mills and estimates it could be phased in over a four-year period. A mill is $1 in property tax for every $1,000 in assessed valuation. A 4.7 mill increase on a $200,000 house would amount to an extra $108 a year in property taxes.

City commissioners are scheduled to hear more details about funding issues related to the possible project at an afternoon study session Tuesday. But commissioners are not scheduled to take any action Tuesday to move the project forward.

“It took us a lot of years to get in this position in terms of not keeping up with Police Department needs,” Schumm said. “To do this all at once may be difficult for the public to handle. This is going to need a lot of study and discussion.”

But City Commissioner Hugh Carter said he doesn’t want the city to put off the issue. He brought up the need for more resources devoted to the Police Department nearly two years ago when he began campaigning for the City Commission.

“The need is there regardless of what we end up doing,” Carter said. “The need isn’t going to go away just because we wait.”

City Manager David Corliss said he is convinced the Police Department is reaching the point where it will need new facilities and additional officers, or else it will have to change how it operates.

“Right now, the force is in a reactive mode, and we’re not able to react to everything the community is putting in front of us,” Corliss said. “I think we will have to start looking at what type of services in the department we want to say no to in the future, if we aren’t able to add resources.”

But Corliss stressed a scenario of adding to both the sales and property tax rates is just one option for funding the project. He said staff members could come up with multiple funding options. One option could include the city taking out more traditional bonds to finance the facility over a 20-year period. But a recent city staff memo said city commissioners likely would have to change the city’s debt policy to do so.

The city’s current debt guidelines say the city should not have general obligation debt of more than $1,100 per person. Once an $18 million library expansion is added to the city’s debt totals, the city would not have room to add a $30 million police facility and still meet the debt guidelines.

But Corliss said the city has the ability to change its own debt guideline and may need to do so because the $1,100 figure hasn’t been adjusted since 2002. The city still has sufficient room to add the project and stay within state-imposed debt limits for cities.

Carter said he will want to consider changing the city’s debt policy so the project could be financed in a way that perhaps would be more palatable to taxpayers.

“If we’re ever going to push that debt number higher, with rates the way they are right now, this is the time to do it,” Carter said.

Commissioners will meet in a budget study session at 4 p.m. Tuesday at City Hall.