SACRAMENTO, Calif. (AP) — The largest dam removal project in United States history is underway along the California-Oregon border — a process that won’t conclude until the end of next year with the help of heavy machinery and explosives. Over the next decade as workers, partnering with Native American tribes, will plant and monitor nearly 17 billion seeds as they try to restore the Klamath River and the surrounding land to what it looked like before the dams started to go up more than a century ago. When demolition is completed by the end of next year, more than 400 miles of river will have opened for threatened species of fish and other wildlife. The project will empty three reservoirs near the California-Oregon border, exposing soil to sunlight in some places for the first time in more than a century. For the past five years, Native American tribes have gathered seeds by hand and sent them to nurseries with plans to sow the seeds along the banks of the newly wild river. Helicopters will bring in hundreds of thousands of trees and shrubs to plant along the banks, including wads of tree roots to create habitat for fish. A power company, known today as PacifiCorp, built the dams starting in 1918 to generate electricity. The dams halted the natural flow of the river and disrupted the lifecycle of salmon, a fish that spends most of its life in the Pacific Ocean but returns to the chilly mountain streams to lay eggs. The fish are culturally and spiritually significant to a number of Native American tribes, who historically survived by fishing the massive runs of salmon that would come back to the rivers each year. A combination of low water levels and warm temperatures in 2002 led to a bacterial outbreak that killed more than 34,000 fish, mostly Chinook salmon.The project will cost $500 million, paid for by taxpayers and PacifiCorps ratepayers. Crews have mostly removed the smallest of the four dams, known as Copco No. 2. The other three dams are expected to come down next year after the reservoirs behind them are drained. That will leave some homeowners in the area without the picturesque lake they have lived on for years. The Siskiyou County Water Users Association, which formed about a decade ago to stop the dam removal project, filed a federal lawsuit. But so far they have been unable to stop the demolition.