The U.S. Army Corps of Engineers is starting work on a massive scope of flood control projects in Puerto Rico that are expected to help protect communities from damages inflicted by flooding like that caused by hurricanes Maria and Irma. The work will total at least $2.5 billion when completed over the next decade.

The money, authorized in February by Congress as part of the $14-billion appropriated to the Corps in the federal Bipartisan Budget Act, won’t require a local match—100% will be paid for by the federal government.

“In this island there are Corps flood control projects that have gone unfinished for years, which contributed in many cases to the flood damage we experienced, which could have been contained had there been the funding for full completion,” Puerto Rico’s representative in Congress, Jenniffer González-Colón, said in a statement.

Because of its mountainous terrain and relatively narrow river beds, the island has repeatedly experienced devastating flash floods during heavy rains and hurricanes. The Corps has studied and even started on flood control projects, but there has been no money to complete the work.

The Corps has identified 13 projects, including six major projects, that it will build or complete with the federal funds including: $1.55 billion for the Río Puerto Nuevo project, $500 million for Río de La Plata, $250 million for Río Grande de Loiza, $82.9 million for Río Grande de Arecibo, $60 million for Río Guanajibo at Mayagüez and $50 million for Río Nigua at Salinas. Additionally, the Corps will spend $10.5 million for studies in five other areas.

The largest project, Rio Puerto Nuevo in the city of San Juan, will require lining 9.5 miles of the river with concrete, the construction of 1.5 miles of earth-lined channel, replacement of 17 bridges, construction of five new bridges and modification of eight existing bridges. That work will also involve two major expressways.

“This is probably one of the hardest projects that the Jacksonville district has ever embarked on,” says Millan Mora, chief of water resources for the district. “There are commercial gas stations, homes that are adjacent to channels. It’s a very complicated project because of location. Think about building the Los Angeles River now. That is what we are doing.”

Work for the other projects will be similar and include flood walls, mitigation, levees and diversions.

Before any work begins, engineers will re-examine the studies and engineering completed and apply lessons learned from hurricanes Irma and Maria to ensure the projects will protect from similar flooding, he says. The Corps is working with the territorial and local government to determine land acquisition. After that, the Corps will develop a schedule and begin putting together bid packages.