The true costs of building a Purple Line in the Maryland suburbs would reach $2.65 billion — about $650 million more than the light-rail project’s proposed contract would cover, according to a legislative analysis.

Under the contract, on which the state’s Board of Public Works is scheduled to vote on April 6, the line’s design and construction costs would total about $1.99 billion. However, the legislative review found that that dollar figure doesn’t include $447 million in construction costs that aren’t part of the contract. Those costs include buying right-of-way, doing off-site environmental mitigation, doing utility work, reviewing the final design and overseeing construction.

It also doesn’t include $198 million that the state has spent on planning the light-rail line, according to the analysis by the General Assembly’s Department of Legislative Services. The $2.65 billion figure doesn’t include financing costs, according to the analysis.

The $5.6 billion Purple Line contract for a public-private partnership would span 36 years – six years of final design and construction and 30 years of operations and maintenance. The companies would help finance construction and design, build, operate and maintain the line in exchange for the state reimbursing construction costs and then making monthly “availability payments” based on the companies meeting certain service requirements.

The contract is attracting national attention because it would make the 16-mile Purple Line connecting Montgomery and Prince George’s counties one of the largest public-private partnership deals in the country and only the second U.S. transit project to include private financing.

The General Assembly has until April 2 to review the proposed contract but may not make any changes.

The legislative analysis also found that the state would pay for the line’s electricity and fare collection enforcement in addition to the monthly availability payments. State officials have said those monthly payments would average $150 million annually.

Electricity to run Purple Line trains is estimated to cost $2 million annually, with an additional $579,000 annually to provide power to stations and other facilities.

The estimated cost for fare enforcement wasn’t included in the analysis. Fare enforcement is critical for light-rail lines because, unlike Metrorail and other subway systems, there are no turnstiles at stations. Passengers have monthly passes or buy a fare card or ticket before boarding, and inspectors do random checks aboard trains. State officials have said Purple Line fares would start at $2.

How much fare revenue is collected on the Purple Line is critical because the state plans to use that money to pay off the private team’s construction debt. Any debt service costs that the Purple Line fare revenue doesn’t cover would be covered by other state transit revenue. The state plans to use money from the Transportation Trust Fund, which pays for road and transit projects statewide, to cover the Purple Line’s operating, maintenance and other costs.

The Purple Line trains would consist of a single light-rail car.

The Maryland Department of Transportation has previously mentioned some of the additional costs outside the scope of the contract, even as MDOT officials have repeatedly referred to the line’s construction as costing $1.99 billion. In a March 4 report to the General Assembly, MDOT said it will use state, federal and local money to pay for “costs outside the P3 contract,” though it didn’t specify the amount. MDOT officials also recently referred to “approximately $400 million” in Purple Line “associated costs” in response to the Post’s questions seeking more details about the financial arrangement.

The Purple Line would have 21 stations between Bethesda and New Carrollton. If the contract is approved April 6, construction would start in late 2016 and trains would carry passengers by March 2022.