Injection plan raises earthquake concerns

Responding to public concern over the City of Malibu’s plans to inject millions of gallons of treated wastewater into land above an active earthquake fault line in Malibu’s Civic Center, county officials have asked the city to further study whether the injections would affect seismic activity along the Malibu Coast fault. 

The request for further seismic study is part of an eight-page comment letter sent last week to City Manager Jim Thorsen by Samuel Unger, the executive officer for the Los Angeles Regional Water Quality Control Board. 

When contacted Tuesday about the letter, Thorsen downplayed the concerns about the potential for earthquakes. 


“I don’t doubt that these seismic issues can be addressed,” Thorsen said. 

Plans to inject groundwater into shallow levels of bedrock are a crucial aspect of a large-scope project to build a centralized sewer system in the Civic Center. All businesses in the Civic Center area must cease septic system discharges by 2015 and hook up to the centralized treatment facility as part of a 2011 agreement between the Malibu City Council and the regional water board. 

The city has spent $2.5 million so far on plans for the project, with another $4 million remaining to be spent on an environmental impact report, further testing, permits and design work, according to Thorsen. 

After passing through the facility, the treated wastewater will qualify as Title 22 effluent that falls short of drinking water standards but is largely harmless to the environment. 

The city plans to reuse some of the treated wastewater for irrigation, but it will still have to dispose of excess water by other means. Originally the city had planned to dump the excess water in leach fields, but opposition by local environmental groups kept the idea from going very far. Thus, the plan for some time has been to dispose of the water by injecting it underground. 

Currently, the city estimates that up to 347,000 gallons of treated wastewater will be pumped underground every day once the system is up and running, which multiplies out to about 126.7 million gallons per year—enough to fill the Malibu Community Pool 253 times. 

The groundwater injection plan proposed by the city concluded that based on three test wells, the best spot to inject groundwater is at a site on Malibu Rd. behind the Malibu Colony Plaza shopping center. But the proposed injection site is believed to be traversed by the 23-mile (37 kilometer) Malibu Coast fault, which raised red flags from concerned parties. 

In studies conducted in the early 1990s, geologists with the United States Geological Survey concluded that the Malibu Coast fault had the potential to cause a 6- or 7-point magnitude earthquake, contrary to the prior belief that it was an inactive fault. Studies also found that the fault had been active within the last 11,000 years, enough to classify as an active site, according to the Los Angeles Times

The goal of the injection is to trap treated wastewater between hard bedrock, approximately 140 feet below the surface, and shallower layers of clay. 

Thorsen claims that shallow drilling will not have any impact on the fault, which he repeatedly has said lies “miles below” the surface.

But in comments attached to the regional water board’s letter, officials with Heal the Bay criticized the city’s plan as conducting insufficient research into whether injecting the water will “aggravate the earthquake fault.” 

Local citizen activist Hans Laetz also argued that the plans were put together too quickly and lacked sufficient evidence to support Thorsen’s long-held argument that the injections are a sound option. 

“The [regional water board], the City and its contractor have leaped headlong into injecting tons of water … into the very top of this very active earthquake fault. No study of any sort — not even a literature review — has been done to gauge the effects of this,” Laetz wrote. 

Now Unger’s office has asked for more details on the envisioned site, including how far the injections are projected to travel horizontally once the treated water is drilled underground. 

In an interview with The Malibu Times on Tuesday, Thorsen dismissed the skeptics and said a pending environmental impact report (EIR) assessing plans for a wastewater treatment center in the Civic Center should show that the fault line won’t be affected by the injections. Thorsen said he had yet to thoroughly read through the board’s comments, which are dated Jan. 16, 2013. 

“All these comments are something our engineers can address,” he said. 

Thorsen remained unsure as to how the City of Malibu will go about responding to Unger’s comments, specifically the need for seismic evaluation, but said it is likely the city can address each of the 50 concerns listed by the regional water board in the upcoming EIR its letter. When asked if further seismic evaluation meant more dollars, Thorsen said he was unsure. 

“It could cost the city more,” he said. “We’ve already got a scope of work we need to get done outside of these comments.” 

The city is now nine months behind on plans for the EIR, which, according to the agreement between Malibu and the regional water board, was supposed to be completed by March 2013. 

The Malibu Times is the first newspaper in Malibu, serving the community since 1946.

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