MTA Probe Centers on Burst Pipe : Sinkhole: Officials are trying to determine why water was not turned off when trouble was reported. DWP says crews responded quickly to the emergency.

Transit officials probing last week’s sinkhole collapse along Hollywood Boulevard are trying to determine why no one turned off a water main for nearly four hours after the first report of trouble, allowing hundreds of thousands of gallons of water to soak the area before half a block of the famed strip collapsed into the subway below.

In the early morning before the street gave way June 22, records show, subway crews summoned immediate help from the Department of Water and Power to track down a water leak in the tunnel, and they warned that the subway was “in danger of possible collapse.”

Water crews found no initial leak, but they returned several hours later and found a water main that they believe had broken in the interim.

Water officials say that a local ground water source--not a city line--may have triggered the episode and that city crews responded quickly to the emergency. But Metropolitan Transportation Authority officials--under fire from all sides over the sinkhole and other recent problems--said they believe the 70-by-70-foot sinkhole would have been much smaller, or not occurred, if the main had been turned off sooner.

“It was the major contributor to the size of the hole in the street,” MTA project manager Charles Stark said in an interview. “We asked them to come because we were experiencing excessive water, and waited for them to turn off the water. . . . Response time is certainly going to be an issue” in the ongoing investigation by the MTA.

Resolving the dispute could prove critical, as dueling government agencies trade blame for a mess that has closed the street and caused widening cracks in the tunnel walls. Damage and repairs are expected to total millions of dollars.

The sinkage has spurred calls by several elected officials for ending Los Angeles’ $5.8-billion subway construction.

One critic, state Sen. Tom Hayden (D-Santa Monica), is pursuing allegations that the safety of about 20 subway workers who were realigning the tunnel was endangered because supervisors refused to evacuate them for several hours.

Hayden’s office has interviewed one worker who alleges that in the initial hours of the emergency, project officials misled state authorities about how many men remained underground, Hayden aide Rocky Rushing said. “This is a clear sign that safety procedures are being ignored,” he added.

Bill Heard, an MTA spokesman, said officials are investigating conflicting reports about the evacuation procedure and the safety of the workers. “There’s a lot we don’t know about that--what happened and who knew what,” he said.

The incident began just after 3 a.m. on June 22, when subway crews noticed increasing water flows in the south tunnel on Hollywood Boulevard near Vermont Avenue, where workers were removing segments of a concrete liner to realign the route.

The first call for help from subway supervisors came into the DWP’s trouble-shooting team at 3:21 a.m. In shorthand account, DWP records show that the subway team reported “Leak. Check source. Flooding. Water flowing into the Metro Rail tunnel at the Barnsdall Park construction site. Needs crew ASAP.”

Robert Simmons, assistant engineer for water operations at the DWP, said a water worker searched Hollywood Boulevard for about 40 minutes but “didn’t see any water on the ground, no water, no leak.”

The DWP worker offered to go down into the tunnel to search for the source of the water but was turned down, according to DWP records. “The [MTA] inspector said ‘No, don’t worry about it,’ ” according to the department’s chronology.

The flooding worsened, however, and subway officials called the DWP again at 4:56 a.m. “The tunnel is still full of water, feels that there is a leak coming from somewhere, requests crew to come back out again, danger of possible collapse,” according to DWP records.

Another water worker was dispatched, but did not arrive until after 6 a.m. By then, according to the DWP, a 10-inch main running about three feet below Hollywood Boulevard had ruptured. Water officials say they believe they can pinpoint the time of the break--a key issue in the dispute with the MTA. Simmons said records show a sharp drop in water pressure and sudden increase in water demand for the area about 6 a.m.

By 6:10 a.m., the ground above the subway had begun to collapse. About 7 a.m., Simmons said, water workers managed to shut down all four gates of the ruptured line, cutting off the flow of water into the hole. Water officials estimate that about 383,000 gallons of water had spewed from the main by then.

Once the rupture was identified, Simmons said, “it was a very quick shut-off.” But the hole widened over the next several hours. A second major collapse hit about 11:15 a.m. as a stream of mud and water descended into the cavern.

Grace Crunican, deputy administrator of the Federal Transit Administration, toured the sinkhole Thursday and asked MTA officials about the emergency response time. “That’s one of the facts we would like to have more information about,” she said.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

Sinkhole Under Repair

The gaping sinkhole that opened on Hollywood Boulevard has been filled in, but life is not yet back to normal for residents and commuters. Transit officials were forced to shut down Hollywood Boulevard once again. All four lanes between New Hampshire Avenue and Edgemont Street remain closed, and officials estimate it will take a few more days to complete the repairs.

What Happened?

Crews working on the subway were tunneling under Hollywood Boulevard when water and mud started pouring in.

MTA officials say: A broken 10-inch water main, four feet below the street, caused the sinkhole, 70 feet wide by 70 feet deep, and, in turn, the cracks in the subway tunnel beneath it.

Water officals say: It was the MTA’s re-mining of the tunnel in an effort to correct alignment errors that made the ground unstable and set off last week’s chain of events.

The Repair Effort 1. After pumping out the water, crews stabilized the hole by pouring in 4,000 pounds of Bentonite, a clay that acts as a sealant.

2. Once the Bentonite hardened, workers filled the hole with two layers of slurry, a mixture of concrete, sand and water.

3. A 12- to 18-inch layer of asphalt was poured on top of the slurry.

4. Workers re-striped the westbound lanes and installed signs, traffic control devices and concrete barriers to separate lanes of traffic. Street lights were adjusted and one lane in each direction was opened to traffic.

5. Inspectors first discovered cracks in the concrete of the north tunnel on Sunday, three days after the street near the subway construction collapsed.

* By Tuesday, inspectors found the fissures had worsened, forcing the re-closure of the street for tunnel repairs. Crews have installed steel-rod reinforcements in the tunnel to encircle the temporary concrete liner and brace it in an area 20 to 30 feet in length.

Detours

* To assist area residents, a free bus shuttle runs every 15 minutes from 7:30 a.m. to 8:30 p.m., making eight stops as shown at left. * The following MTA bus lines have been rerouted:

Line 206 (Normandie Avenue)

Line 1 (Hollywood Boulevard)

Line 180 (Hollywood/Glendale/Pasadena/Altadeana/North Lake Avenue via Colorado Boulevard)

* Barnsdall Park remains open, with access off Edgemont Street. Source: MTA: Researched by Cecilia Rasmussen/Los Angeles Times