Federal wildlife agencies still have serious concerns about how two giant water diversion tunnels proposed in the Delta may harm imperiled species such as salmon and Delta smelt.
In comment letters made public Thursday, the U.S. Fish and Wildlife Service and National Marine Fisheries Service praised Gov. Jerry Brown's administration for making progress on many concerns they raised in so-called "red flag letters" released last year.
But the agencies also said the Bay Delta Conservation Plan still presents a number of major concerns, some of which they labeled "critical." The letters were based on revised draft chapters of the conservation plan released to the public over the past month.
The conservation plan proposes to divert a portion of the Sacramento River's flow into two 40-foot-diameter tunnels, fed by three new intakes along the Sacramento River near Courtland. It aims to balance potential harmful effects of the tunnels by restoring 100,000 acres of habitat to create a net benefit. The habitat restoration will begin during tunnel construction, which is expected to take a decade.
Among the concerns expressed by the National Marine Fisheries Service is the potential that, in combination with climate change, the tunnels may cause extinction of winter-run chinook salmon, an endangered species in the Sacramento River.
More broadly, the agency also says water diversions may leave insuffient flow in the Sacramento River, under some conditions, to facilitate fish migration -- and may even cause river flow to reverse in some situations.
Bay Delta Conservation Plan officials responded with a letter of their own, saying the plan will not make winter-run extinction more likely. It notes that the National Marine Fisheries Service itself, in 2009, reported that extinction would be likely with climate change alone unless upstream dams are modified for fish passage.
The service also says there is no evidence that habitat restoration will work, or even if it will work enough to offset harm to fish that may result from the new water diversion system.
"There is no specific analysis of the feasibility of acquiring 65,000 acres of land appropriate for tidally influenced habitat restoration," the service wrote in its letter. "All related analyses proceed as if restoration will be wholly successful."
Karla Nemeth, program manager of the Bay Delta Conservation Plan, said she is "very optimistic" such concerns will be addressed in the final plan, set for public release this summer.
"I think we've made some really good progress on addressing nearly all of their concerns," Nemeth said. "We'll just need to continue to work on them."
The new comment letters can be found online at: http://ht.ly/k5mk8.
Contact The Bee's Matt Weiser at (916) 321-1264. Follow him on Twitter @matt_weiser.