L.A. officials missed possible sign of quake fault in Hollywood
Los Angeles officials missed signs in a geological report that suggest a $200-million residential and commercial development now under construction in Hollywood might be located above an earthquake fault, according to city records and interviews.
The information was contained in reports written by a geotechnical engineering consultant hired by the developer of the Blvd6200 project and filed with the city. The report, obtained by The Times under the California Public Records Act, said groundwater levels varied by as much as 30 feet below the property.
Geologists generally consider uneven groundwater levels in California a strong indicator of an earthquake fault.
The city Department of Building and Safety did not raise concerns about an earthquake fault when it reviewed and approved the report in 2007 without requiring any in-depth seismic study.
California state geologist John Parrish said the uneven groundwater cited in the report suggests that the project could sit on top of the Hollywood fault, which is capable of producing a devastating 7.0 earthquake.
“One of the most common indicators of the existence of a fault is the presence of an offset groundwater table,†Parrish said. “It can be logically construed that the break in groundwater table elevations is because of the presence of a fault.â€
Parrish and another geologist who read the report said the differing water levels should have prompted further underground investigation, such as digging a trench and deep holes in the ground to determine whether there is actually a fault.
A spokesman for the Los Angeles Department of Building and Safety said Thursday that the agency still believes a seismic study was unnecessary.
“We agree that variations in groundwater levels are sometimes the result of faulting,†Luke Zamperini said.
But the agency determined Blvd6200 was far enough away from the Hollywood fault that a fault study was not necessary, he said.
Zamperini said the city’s normal practice is to require seismic studies on sites within 500 feet of a known fault.
The 2005 California Geological Survey map that city officials consulted placed Blvd6200 at just over 500 feet from the fault.
But before groundbreaking in 2012, the state published a major update to that map that placed the fault less than 200 feet from the project.
Zamperini said the department’s map technician had not been aware that he was using an outdated map until The Times showed the agency a copy of the updated map last week. The city asked the state for a copy of the map this week.
“Looking back in time, we don’t think we made a mistake,†Zamperini said. “We’re not going to go back and make them remove the building that they’ve built so far to do a fault investigation.â€
Structures built on top of faults are particularly vulnerable to damage or collapse during the violent shaking of a major quake. Because of this, California law generally requires seismic studies for any new building proposed within roughly 500 feet of a fault in a state-designated earthquake fault zone.
The Hollywood fault has been known for decades. But California geologists have not yet formally certified it as a fault zone, and the law is not in force in Hollywood until they do.
The soil report filed by the developer’s consultant to the city cited an even earlier fault map produced in 1991 showing the Blvd6200 project was 1,000 feet away from the Hollywood fault.
The developers, Clarett West Development and DLJ Real Estate Capital Partners, said in a statement that Blvd6200 “obtained all necessary approvals and is under construction in compliance with those approvals.â€
They said the environmental impact report certified by the city says “that the project site is not located within an earthquake fault zone, and that no active or potentially active faults lie beneath the project site. Each of these conclusions remains accurate today.â€
The developers also said a geologist was on site when construction crews removed 220,000 cubic yards of dirt to make way for construction.
“The geologist confirmed the absence of any subsurface faults on the project site. This excavation was more extensive than exploratory trenching,†the statement said.
The developers declined to provide The Times with further documentation about the geologist’s conclusion. The Los Angeles Department of Building and Safety received the same assurance over the phone from one of the developer’s consultants in the last few days, but has not received a written report that makes that declaration, Zamperini said.
Blvd6200 is one of several developments near the Hollywood fault that have come under scrutiny in recent months because of their proximity to the fault.
The project is a massive six-story development next to the Pantages Theatre that would remake the block east of Hollywood Boulevard and Argyle Avenue.
Plans approved by the City Council in 2007 called for 500 apartments and 74,000 square feet of retail space in the first phase of the development.
A series of reports showing the water levels were submitted to the city between 2006 and 2012. The developer commissioned it as a routine soil analysis required by the city, and the study did not address whether the water levels could be tied to the fault.
The developer’s consultant asserted that “the potential for surface ground rupture at the subject site is considered low.†He cited “research of available literature and results of site reconnaissance†and the fact that the state has not drawn a fault zone around the site.
Bruce Clark, a retired engineering geologist and former chairman of the California Seismic Safety Commission, said that ordinarily, groundwater levels vary by about 1 or 2 feet underneath a property.
The developer’s consultant found groundwater 30 feet higher on the north side of the property than on the south side.
The report was filed with the developer by engineering geologist Reinard Knur of Geotechnologies Inc. of Glendale, and eventually submitted to the city. It said the uneven water levels could be related to a clay barrier.
“Fluctuations in the level of groundwater may occur due to variations in rainfall, temperature, and other factors not evident at the time of the measurements reported herein,†the report said.
Knur referred questions to the developer.
The developer’s geology report was signed off on by the city geologist’s office. But Zamperini said the city geologist, Dana Prevost, was unaware of the uneven groundwater levels because the soil reports were reviewed and approved by a lower-level staffer.
Clark and Robert Sydnor, a retired senior engineering geologist who worked for 25 years with the California Geological Survey, said the water level difference by itself is not conclusive of a fault without further underground investigation. But it’s an important piece of evidence.
“The reason why the groundwater can get trapped that way is because when it comes to a fault … the water can’t get through,†Clark said.
Geologists have used uneven groundwater levels to pinpoint the path of the Hollywood fault in other spots.
Near Cahuenga Boulevard north of Hollywood Boulevard, there’s a difference of 30 feet in elevation between the groundwater levels on the north and south sides of a section of the Hollywood fault, according to data published in the 1990s.
Faults can act as a barrier for water because during repeated earthquakes, rocks are ground up into a fine powder and clay.
This keeps water from flowing through it, said U.S. Geological Survey seismologist Lucy Jones.
“It’s a warning sign†of a fault, Jones said, “without being definitive.â€
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