Maine has three major public construction projects under way — the redesign and consolidation of the state prison system, the renovation of a Vassalboro school into a police training academy, the installation of a new legislative computer system as part of the State House/State Office Building makeover. The three face major cost overruns of as much as 20 percent, for a total that could exceed $30 million.

The explanation given is that the booming economy has driven up the price of contractor services and materials. It’s an explanation, just not a very good one. Nor is it acceptable.

When it was approved by the Legislature last year, the project to modernize Maine’s dilapidated and inefficient prison system was expected to cost $137 million. Bids on one component suggest the total price tag could be $20 million higher, perhaps even $30 million. The police training academy was supposed to cost $11.3 million. With work under way, it’s now $2.5 million more. The computer upgrade, replacing a system that’s as close as high-tech can get to an antique, is part of the $52 million state complex remodeling and is pegged at $5 million, maybe $6 million, over budget.

The King administration is looking for ways to lower the projects costs by substituting cheaper components, which is exactly what any real-world businessperson or homeowner would have to do when bids exceed budget. The governor’s statement that this is a “good news, bad news kind of thing” may be a true observation, but requires investigation.

It is good news that the Maine economy has improved and has put contractors and their crews back to work. To expect Maine taxpayers to pay for this improved economy isn’t just bad news, it’s bad policy. And paying for any part of the overruns from the $250 revenue surplus must be a last resort. The surpluses Maine has generated the last two years are largely the result of the state failing to meet its education-funding obligation during bad times. To continue to fail because of good times would be absurd.

Sen. Philip Harriman, the ranking Republican on the Appropriations Committee, wants the consultants who made these lowball estimates to explain to the committee why they were so far off. They should — consultants who develop project costs are paid to see at least as far into the future as the date of bid openings. The economy has improved, but it hasn’t just started improving. Its current condition, while relatively robust, is hardly the Gold Rush.

The full Legislature will have to deal with issue one way or another, either by approving significantly scaled-back projects or by appropriating more money. Before it does either of those things, it should ask the kind of questions any real-world businessperson or homeowner would ask. Exactly how much of the cost overruns are due to higher material costs, over which a contractor would have no control? How much is due to higher wages and better benefits for workers, the folks who are supposed to gain from an improved economy? How much is just plain gouging?