PORTLAND, Maine — The Cumberland County Board of Commissioners on Monday unanimously green-lit a preliminary budget for 2015 operations that would increase the county property tax rate by 5.2 percent.

County spending would increase by $1.3 million to a total of $26.7 million under the proposed budget. The spending plan must still undergo further review and receive final approval from the five-member board, likely in December.

The increase is slightly more than the hike made last year, when commissioners approved an increase of 4.3 percent for 2014 spending.

Under the proposed 2015 budget, a homeowner whose property is valued at $200,000 would see a county tax bill increase of $6.90, for a total bill of close to $139, according to a county memo.

The modest tax increase was reflected in the board’s agenda for its meeting, which required less than an hour to complete. While public testimony was invited, no one stepped forward to comment on the budget.

Much of the increase stems from bookkeeping changes designed to maintain the county’s AA+ bond rating, and to reduce the drain on the county’s fund balance.

“This is in many respects a structural budget,” County Manager Peter Crichton said in the memo.

Other changes are related to personnel, such as a mandatory $111,000 increase for retirement funding.

In addition, the county’s finances have had to withstand the lingering effects of economic recession, said board Chairman James Cloutier, who represents county District 5, covering most of Portland.

“We’ve been in entrenchment mode for several years now,” Cloutier said, calling county revenues “draggy.”

Spending also focuses on the former Cumberland County Civic Center in downtown Portland, now renovated and renamed the Cross Insurance Arena, he added. Costs of operating the venue represent nearly half of the proposed spending increase.

In addition to the arena operations, which are now being outsourced to a private management firm, the county is responsible for a variety of regional functions. They include the Sheriff’s Office, emergency communications and handling legal matters such as deeds and probate.

With more than 280,000 residents, Cumberland is by far the most populous and most densely populated of Maine’s 16 counties. It includes 28 municipalities, ranging from the state’s largest city, Portland with a population of 66,000, to one of the smallest hamlets, Frye Island, with a population of five.