In what may be the final chapter of one of California’s longest and most bitter water battles, the federal government this week bowed to pressure from state officials and all but dropped plans to build the massive Auburn Dam on the American River in Northern California. The Bureau of Reclamation announced that it will abandon a tunnel that diverted water from the river and was linked to plans to build the dam. The turn of events is a victory for enviros and other opponents who said the dam, estimated to cost nearly $1 billion, would be too expensive and environmentally destructive. The dam project had been embroiled in controversy since it was authorized in 1965, and in 1992 the House voted overwhelmingly not to fund it, but a number of California Republicans and Southern California water agencies continued to press for its construction.