SACRAMENTO — A proposal to construct two huge water diversion tunnels beneath the Sacramento-San Joaquin Delta includes plans for rerouting three, two-lane highways — previously undisclosed projects that carry a preliminary price tag of at least $265 million, a newspaper reported.

Highway 160 in Sacramento County would be detoured around three water intakes proposed as part of the tunnel project, and new interchanges would be built on highways 4 and 12 to accommodate heavy construction traffic, according to engineering documents obtained by the Sacramento Bee (http://bit.ly/Y6mEnh ).

Plans for the highways have not been included in thousands of pages of documents about the twin tunnel project that have been released so far, the Bee reported on Sunday. The possible costs of the work have also not been included in estimates of the conservation plan, which are currently at $14 billion, according to the Bee.

Gordon Enas, a principal engineer at the state Department of Water Resources, said the highway changes are being studied, but he described the plans as “way preliminary.”

“It’s all kind of conceptual at this point, so I’d hate to have you think we’ve finalized our design,” he said.

The work would be part of the Bay Delta Conservation Plan — a federal and state initiative financed by California’s water contractors aimed at restoring and protecting the delta ecosystem and guaranteeing a stable water supply for millions of Californians.

The 35-mile twin tunnel project would carry water south to vast farmlands and thirsty cities. Construction and operation costs of almost $20 billion would be covered by water contractors.

The plan also calls for creation of more than 100,000 acres of new habitat — floodplains, tidal marshes and grasslands.

Farmer Daniel Wilson, who relies on Highway 160 to get his cherries, pears and corn to a packing shed and then to market, said he worries how the proposed changes would affect the distribution of his crops.

“We run a trucking company during our harvest season,” Wilson said. “I can’t see anything but total disruption of that for 10 to 15 years. It’s hard to imagine that you wouldn’t destroy the whole road system.”

With its views of the Sacramento River and path through historic agricultural areas and small towns, Highway 160 has been designated a state scenic highway.

It’s not clear whether the river views would remain under the proposed reconfiguration.

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Information from: The Sacramento Bee, http://www.sacbee.com