November 09, 2017
The Most Valuable
Information Free To All

Could a Simpler Delta Tunnel Solve Years of California Water Conflict?

A decade ago, the state passed up a chance to embrace a cheaper, single water diversion tunnel in the Sacramento-San Joaquin Delta. Now a groundbreaking vote by a Silicon Valley water agency could turn the tide.

by Matt Weiser

CALIFORNIA’S AMBITIOUS PLAN to build two giant water tunnels under the West’s largest estuary has been deemed too expensive by some of the water utilities that would have to pay for it. As a result, attention is turning back to a cheaper option: One tunnel instead of two.

On October 17, the board of directors of the Santa Clara Valley Water District unanimously rejected the $17 billion twin-tunnel project, known as WaterFix, and instead expressed support for a smaller, single-tunnel alternative. The district serves more than 1 million people in Silicon Valley.

A single tunnel was also recently endorsed by Los Angeles mayor Eric Garcetti, who represents a big share of the urban customers who would help pay for it. And the Public Policy Institute of California, a prominent think-tank, came out in support of the idea last year.

Ironically, it is an option the state’s top water agencies rejected out of hand a decade ago. This occurred even though environmental groups actually supported it and encouraged the state Department of Water Resources and its water contractors to investigate a single tunnel, which could save nearly $8 billion.

What’s even more striking is that a single tunnel was first proposed not by environmental groups dabbling around the edges of the water industry. It came from an expert at another Bay Area water utility with lots of experience building big water projects.

“We told them back in 2007 that the right thing to do was build one tunnel, and see if it works,” said Greg Gartrell, who was then assistant general manager at Contra Costa Water District and is now retired. “If you need two tunnels later on, do that. But if you do two tunnels right up front, you’re basically stranding an asset. Half your investment is doing nothing for you.”

State officials looked at a single-tunnel option in the Sacramento-San Joaquin Delta as one of more than a dozen alternatives for their WaterFix project. The route, shown here, includes a single 3,000cfs tunnel and one intake on the Sacramento River, near Clarksburg. (Image courtesy California Department of Water Resources)

Gartrell said that is because the state’s own analysis of the tunnel concept shows water yield from the project doesn’t increase much, no matter how big the tunnels are. One reason is that, very often, the flow in the Sacramento River restricts how much water can be diverted into the tunnels.

For obvious reasons, the project would never be allowed to divert so much water that it would dry up the Sacramento River. This resulted in a basic ground rule stating that no water can be diverted into the tunnels until river flows reach about 15,000 cubic feet per second (cfs). Such flows generally occur only during winter and spring. Even then, only minimal diversions are allowed until river flows ramp up much higher.

As a result, Gartrell said, river conditions allowing the dual tunnels to operate at their full 9,000cfs capacity would exist only about 7 percent of the time.

In contrast, a single tunnel sized at 3,000cfs would be able to operate at full capacity much more often. On balance, it would fall just a few hundred thousand acre-feet short of matching the total annual water diversions of the dual tunnels, Gartrell said.

The state’s own analysis in 2013 showed that a single-tunnel project sized at 3,000cfs would deliver only 10 percent less water annually.

That’s not a significant loss, he said, from a project expected to deliver more than 4 million acre-feet annually. And the $8 billion saved could be spent on other water projects that would more than make up the difference.

The $17 billion dual-tunnel project is intended to create a bypass for freshwater exports from the Sacramento-San Joaquin Delta, an estuary that provides freshwater for 25 million Californians and 3 million acres of farmland.

For decades, this water has been diverted using massive pumps at the southern edge of the South Delta, near the town of Tracy. The pumps kill millions of native fish and are powerful enough to reverse the Delta’s natural river flows, disrupting habitat and causing water quality problems.

The tunnels would switch diversions to a location 40 miles upstream on the Sacramento River. This would prevent the reverse-flow conditions and, with modern fish screens in place, would reduce the fish kill.

Gartrell’s single-tunnel idea was subsequently embraced by a number of environmental groups as a promising solution to the Delta’s troubles.

In 2010, the Planning and Conservation League released a package of eight water solutions for California that included a single Delta tunnel.

Then in 2013, the Natural Resources Defense Council released its so-called portfolio-based alternative, which supported a single Delta tunnel along with numerous regional water-supply projects.

If the state had chosen to pursue a single tunnel years ago, said NRDCattorney Doug Obegi, it’s likely construction could have been well underway by now given its smaller size and fewer logistical and environmental complications.

“It does seem like a missed opportunity,” Obegi said. “We’ve wasted significant time and millions of dollars studying this larger project that doesn’t make sense economically or ecologically.”

The question now is, what would be required now to embrace a single tunnel as a serious alternative?

The state did include a single tunnel (known as alternatives 5 and 5A) among its formal alternatives in the final environmental impact study adopted in December 2016. This alternative called for a single intake on the Sacramento River and a single tunnel with a capacity of 3,000cfs. This single tunnel would follow the same approximate route under the Delta as the dual-tunnel project.

The state estimated in 2013 this single-tunnel alternative would cost $8.6billion – about $8 billion less than the dual tunnels.

Officials at the Metropolitan Water District of Southern California have said they are open to considering a single tunnel. The district is the largest water agency to support the more costly dual-tunnel project so far.

“We’re always willing to talk about it,” Roger Patterson, Met’s assistant general manager, told Water Deeply in December. “I get it: In order to get something done, you gotta do horse trading. But it also still has to work.”

It is unclear if the single-tunnel alternative was investigated sufficiently by the state to become its new project choice. Obegi said it was not, and much deeper analysis will likely be required.

“How it would be operated is really the most important thing in determining whether this is something that would be OK for the environment or would be detrimental for the Delta,” he said. “There’s very little to nothing that has been said about how they would operate a smaller facility.”

Such details may be moot, because the state Department of Water Resources is still officially wedded to the $17 billion dual-tunnel project, said spokeswoman Erin Mellon.

DWR is continuing to advance WaterFix as it is currently structured: A two-tunnel project with three intakes with a combined capacity of 9,000 cfs,” she said.

Originally published on | Photo Credit: Wikipedia Commons

Leave a reply