Streams Drying Up in Hills Near Tunneling
Even in Los Angeles, where ocean beaches and snowcapped mountains are part of the everyday landscape, a 50-foot waterfall in the neighborhood is a wonder to behold.
At least it was. The waterfall, which spilled from a rock precipice high over John Chickering’s house in Nichols Canyon in the Hollywood Hills, has dried up. So have several streams that watered the canyon and the hills nearby that residents say had run uninterrupted for at least 50 years.
Although it has been a dry year, some fear that the weather has less to do with it than the subway.
The drying up of springs and streams in Nichols Canyon and neighboring hillsides over the last few months, experts say, is evidence that boring subway tunnels through the splintered, porous bedrock of the Hollywood Hills just west of Cahuenga Pass is having a much greater impact on the natural environment than predicted.
For the thousands of people like Chickering living in the verdant hills above the subway route, the loss of the streams is more than a matter of aesthetics. The year-round flow supports deep-rooted trees and plants that retard the spread of fire and bolster the slopes against erosion and mudslides. The lush vegetation also supports deer, coyotes and a variety of smaller animals.
“It was unbelievable,” Chickering said. “I looked out of my window one morning, and the falls were no more. The water had stopped. It was like a curse. Then I remembered the subway and what people had been saying about all the underground pumping going on.”
As powerful pumps drain the advancing tunnels of unwanted moisture at a rate of nearly 1 million gallons a day, the water table that fed the waterfall and the streams, as well as the area’s abundant vegetation and wildlife, has dropped as much as 134 feet, officials say.
Pumping has been draining an untapped water source--the Hollywood basin--of up to one-third of its annual capacity. Virtually all the water pumped out of the tunnels winds up in Santa Monica Bay.
The area most affected by the pumping is a stretch of canyons and hillsides between Laurel Canyon and the Cahuenga Pass that includes one of the city’s most popular urban parks, 133-acre Runyon Canyon.
The tunneling, which is passing 165 feet to 900 feet under the Santa Monica Mountains on its way from Universal City to Hollywood, has gone more slowly than expected. The boring machines are expected to reach Hollywood this fall.
Late in July, MTA consultants noted “a substantial decrease” in the water flowing from two streams in Runyon Canyon.
Nichols Canyon, where three year-round streams have dried up, is just to the west. The beauty of the area--which has been the subject of paintings by artist David Hockney--has not been lost on MTA officials.
“It’s spectacular. The water comes down from two different directions. If you’ve driven up Nichols Canyon, part of it looks like a rain forest,” said James Sowell, the MTA’s manager of environmental compliance.
Los Angeles County supervisor and MTA board member Zev Yaroslavsky, who represents the area, points out that some of the streams in the area dry up every year and that this year is an especially dry one.
“We haven’t had any rain since January. You can find dry creek beds and brown hillsides all over the Santa Monica Mountains,” Yaroslavsky said.
“But some of the problem is undoubtedly due to the tunneling,” he added.
MTA Replaces Water in Streams
Although MTA officials say they aren’t sure what is causing the springs and streams to dry up, they are paying to replace a portion of the lost flow with water from the Los Angeles Department of Water and Power.
“You can acknowledge an effect without having any clue as to what the cause is,” Sowell said. “We are responding to the community’s concerns. They see MTA as the cause. . . . We’re attempting to be good neighbors.”
In recent weeks, the MTA began tapping into several mains, allowing up to 34 gallons per minute of DWP water to flow into the stream beds and over Chickering’s waterfall.
Chickering and his neighbors say the supplemental flow is a thin stream compared to what it was.
“It’s enough water to provide an illusion of normalcy,” said Nichols Canyon Assn. President Herschel Gilbert. “But it doesn’t replenish natural flows, even at this time of year. And if the springs don’t come back, these canyons will lose the rich array of plants and animals that make them special.”
Unfortunately, there is no record of what the normal flow has been, according to Yaroslavsky’s office.
“People are saying everything should be returned to normal, but nobody knows what normal is,” said Howard Katz, a land-use lawyer retained by Yaroslavsky to monitor the impact of the tunneling.
The pumping beneath the Hollywood Hills is part of the ongoing dewatering of the subway route that in the past has sucked out as much as 380 million gallons a year.
That’s about the same amount of water consumed by 2,300 families in a year.
The loss of that water in a city frequently battling other communities over water rights has not gone unnoticed by state officials, who asked the MTA to look into ways to conserve the water that the agency is pumping into the ocean.
In a study conducted last year, the MTA stated that it would be prohibitively expensive to recycle water into the hills.
Transit officials made up their minds more than a decade ago that tunneling under the Hollywood Hills wouldn’t have much of an environmental consequence.
“By confining ground-water control activities to the immediate area of excavation, the Metro Rail project will avoid potential adverse impacts on urban flora caused by a lowered water table,” said the project’s environmental impact report.
MTA officials now say that any impact from pumping will be temporary and predict that affected stream flows will resume after the excavation is done.
But officials also acknowledge that some dewatering will continue indefinitely to relieve hydrostatic pressure on the tunnel walls.
And no one, including the MTA, is certain what the effects of that pumping will be.
Effect on Plants Could Be Severe
But if the water table does not rise and perennial streams do not come back, the effects on the adjacent hills could be severe, according to a consultant hired by a coalition of residents.
The most deeply rooted trees and plants, among them Western sycamore, acacia, laurel sumac and California holly--which stabilize the steep hillsides--would be hard-pressed to survive. In addition, lush canyon bottoms that depend on year-round stream flows will lose the verdure that has made them oases for wildlife.
“The flora which draws its water from the springs will be severely stressed,” said a 1996 report by MHB Technical Associates of San Jose.
“Effects could include increased dieback of deep-rooted plants like laurel sumac, which could result in increased erosion, slides and flooding,” said the report. “Mammals and some bird life will either migrate, diminish in abundance or die.”
The study predicted that if the water table was lowered by more than 50 feet, streams in Runyon Canyon and adjacent canyons “would most certainly dry up.”
Armed with those findings, the neighborhood coalition sued the MTA to require the agency to conduct another environmental impact report. The suit was settled last year, with the MTA agreeing to take a variety of measures to prevent the underground pumping from harming streams, plants or wildlife.
All along, MTA officials said they could seal water out of the tunnels by using grout to plug fractures in the rock. After the consent decree, the agency augmented the grouting operation, working both ahead of and behind the tunnel-boring machines.
In early March, about nine months after the MTA had begun tunneling under the hills, Chickering first noticed a change in the waterfall that spilled dramatically down a stairway of rocky ledges to a stream flowing to the mouth of Nichols Canyon at Hollywood Boulevard, about two miles south.
By midsummer, the falls, the stream and two tributary streams in Nichols Canyon had dried up.
For the first time, the free-flowing water supply that ran the length of the three-mile canyon had stopped, said Gilbert, who has lived in the canyon for 47 years.
Meanwhile, two canyons away, Vivian Harrison was observing a similar phenomenon. A spring that bubbled out of the ground on her property for the 23 years she has lived there had suddenly gone dry.
Officials estimate that the MTA will spend about $50,000 a year replacing water that nature used to supply to Chickering’s waterfall, Harrison’s spring and two other streams.
In addition, the MTA is watching at least 30 other streams in the area. Some are seasonal and dry up every year during the summer and fall.
But the MTA is not promising to monitor springs or supply replacement water indefinitely.
Long-Term Needs, Remedies Uncertain
Agency officials say they are hopeful that once the tunneling is finished and the rock walls are thoroughly grouted, there won’t be any more need to pump: The drawdown will cease, and with the help of winter rains, springs and streams will be recharged.
“A lot depends on the effectiveness of the grouting program,” said Sowell, who conceded that figuring out where to grout is something of a guessing game. “It’s a difficult art. It’s not a science, by any means.”
And what will the agency do if the springs don’t return?
The consent decree requires the MTA to take remedial action for five years. After that, Sowell said, “we have the option to continue to grout over time. What is a reasonable amount of time? We’re going to try to get a handle on that.”
Yaroslavsky took a harder line.
“If the tunnels have to be pumped forever and that causes a problem, why assume we couldn’t pump the water back up into the hills? I wouldn’t have any reservation in requiring that.”
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Water and the Subway
A drop in ground water levels near construction of the MTA’s Red Line is suspected to have caused some natural waterfalls and springs to cease flowing. The MTA is replenishing the falls, pumping fresh water through a pipe at the site. When tunnel construction is finished, ground water levels will return to normal, MTA engineers believe.
* When tunneling began: east tunnel, May 10, 1996; west tunnel, July 29, 1996
* Footage mined since start of construction: more than 10,000 feet in each tunnel
How Water Surfaces
The MTA is pumping 850,000 to 1.5 million gallons of water per day from its tunnel sites, This water flows into drainage channels and on to the L.A. River, eventually emptying into the ocean. Here’s how a change in ground water levels can affect springs:
[A] Water from precipitation passes down through porous soil, collecting atop a nonporous layer.
[B] Pushed by gravity or pressure, water flows underground, surfacing through cracks or faults.
[C] Pumping water from below ground can cause the ground water level to subside, drying up springs and falls.
The MTA’s Monitoring Program
MTA workers had been monitoring 37 streams in the vicinity of tunnel construction and are now widening the monitoring area.
* The level of the water table above the tunnels has dropped as much as 134 feet since the start of construction.
* Of the 37 streams and springs under observation, four have dried up. In several locations, water is being replenished by the MTA.
Source: Metropolitan Transportation Authority
Researched by RICHARD SIMON and FRANK CLIFFORD / Los Angeles Times
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