This story has been updated.
Southern California gets about a third of its water from the Sacramento-San Joaquin Bay Delta east of San Francisco. But deliveries aren't always reliable because ecological concerns often slow the pumps conveying the water southward.
The state wants to build two new conveyance tunnels under the delta to reduce ecological harm and increase reliability, but the plan is in trouble for lack of funding. Now Southern California's biggest water agency — the Metropolitan Water District — is offering to help save the project. And its plan would cost ratepayers more.
Exactly how much more is a tricky question.
The tunnels could add an average per-household cost to monthly water bills of about $2.40 in a best case scenario. That’s one in which MWD puts nearly $11 billion into helping construct the tunnels and is reimbursed by other water agencies who pay to receive bigger water supplies. MWD’s ultimate investment in that case would be about $5.3 billion, officials estimated.
But home water bills could rise, on average, by as much as $4.80 in the worst case situation. In that picture, MWD puts up nearly $11 billion toward the tunnels construction, and no other water agency contracts to pay the costs of moving water under the delta, and the tunnels produce no other revenue. Officials say that scenario is unlikely. But the risk that MWD cannot recoup the investment would be a key concern when the MWD board votes on the plan next month.
MWD imports water from Northern California and the Colorado River and re-sells it to other public water agencies from Ventura County to San Diego. Those agencies sell water to individual homes and businesses. People who live in areas that use more imported MWD water would see higher average costs, and those in areas that use less imported water would pay less.
MWD is having to pay more to save the twin-tunnel idea because other water agencies that were seen as beneficiaries of the project didn't agree to pay their share of the $17 billion needed to build the project.. That led the state Department of Water Resources to call for a staggered plan for one tunnel now, and maybe one later.
The less-ambitious single tunnel plan didn’t sit well with some MWD directors, and on Tuesday, the board received the new cost estimates for what it would take to underwrite a larger portion of the two-tunnel project.
And the Central Valley agencies that didn’t want to be part of a two-tunnel plan? They can still get water from the completed project by reimbursing MWD for the construction and operating costs, said Assistant General Manager Roger Patterson told the board.
Their water would be somewhat more expensive per acre foot than what project participants pay, but it would spare them from having to put the construction money up front.
Agency officials said the twin tunnels would allow more water to be captured, especially during high intensity storms. Dual tunnels could also do more than a single tunnel to keep ocean water from flooding into the delta, damaging the ecosystem.
But some environmentalists argue the money for even one tunnel could be better spent to increase local sources of water.
The two-tunnel proposal has a few hurdles to clear before the MWD board votes next month. Other agencies that are part of the State Water Project would have to also increase their share of the project for the two-tunnel math to work.
Los Angeles City Councilwoman Nury Martinez has asked the city council to review the two-tunnel plan at its meeting Wednesday. Mayor Eric Garcetti has signaled his opposition to the plan, preferring instead to spend money increasing sources of local water through groundwater remediation, conservation and by capturing stormwater.
Correction: An earlier version misstated the amount MWD’s board expected to invest in the twin tunnel project when it voted in October. That amount was $4.3 billion.