The federal government on Wednesday approved the start of construction for California’s $69 billion high-speed rail line, capping years of planning on the first leg of tracks in the Central Valley and likely kicking off a new round of lawsuits from opponents.

The state has been eagerly awaiting the Federal Railroad Administration’s endorsement of the Merced-to-Fresno section of the bullet train line since Gov. Jerry Brown and the Legislature gave the go-ahead two months ago.

Even though Congress and President Barack Obama previously approved enough funding to split the cost of the initial stretch of track, U.S. officials still needed to ensure the project met federal environmental laws. Wednesday’s 41-page ruling said that while the bullet train will have “significant” negative impacts on the environment and community — from loud noises to reducing property values — it’s still worthwhile.

“Over the next several years, this project will put thousands of Californians to work and provide the state with the transportation capacity and connectivity needed for long-term economic expansion,” FRA Administrator Joseph Szabo said in a statement.

But don’t expect shovels to start hitting the ground tomorrow. Through November, private construction firms will be bidding against each other for the first $2 billion contract, and the winner will need until spring to put together the crews and blueprints necessary to start construction. But prep work such as demolition and moving utility lines could begin later this year if the state survives a bevy of court challenges.

The decision is the last of four votes needed before the project could kick off, with the state and federal governments each approving funding and environmental planning for the line. The most significant — and controversial — verdict came in July when Brown and lawmakers approved $8 billion in funding. The environmental approval process is also pivotal, largely because it allows opponents to sue to block the railroad.

Three Central Valley groups in June filed lawsuits after the state signed off on its environment plan, and now they are expected to sue again over the federal approval.

“There are quite a few coalitions that have been ramping up for months waiting for this to drop,” said Anja Raudabaugh, executive director of the Madera County Farm Bureau, one of the groups suing. “I expect there will be a legal challenge mounted against this.”

The cases against the state face hearings in Sacramento Superior Court on Friday. A judge is expected to rule on Madera County’s request to hold an injunction hearing in November, when the county’s lawyers would argue that the project should be halted.

Stuart Flashman, an Oakland-based environmental attorney whose clients on the Peninsula are also suing the California High-Speed Rail Authority, said a federal lawsuit could become particularly important since Brown and lawmakers are weighing new policies that would make it much tougher for opponents to block projects in state court cases.

“I wouldn’t be at all surprised if some of the same folks who sued over the state (approval) will also end up filing a lawsuit under the federal” laws, Flashman said.

Contact Mike Rosenberg at 408-920-5705. Follow him at twitter.com/rosenberg17.