Consultants to Los Angeles County have recommended enlarging the first phase of a proposed Malibu regional sewer system, adding about 150 properties in geologically unstable areas.
The consultants also have increased their cost estimate for construction of the system, originally expected to be a $60-million project, by about $5.4 million.
The County Board of Supervisors is expected to hold a public hearing on the controversial sewage proposal Sept. 24, said Brian Scanlon, county sewer maintenance superintendent. Scanlon originally planned for supervisors to consider the project earlier this year, but the matter was postponed until an amended report could be prepared by James M. Montgomery Consulting Engineers. The report was released Tuesday.
Malibu residents have voted three times against paying for sewers, but the supervisors can now impose an assessment for the system without voter approval because the county health officer has declared that septic tanks in Malibu pose a health hazard. Local civic groups in turn have contended that the county is trying to build a much larger system than needed, at residents' expense, to accommodate growth in their beachfront community.
This week's report suggests adding sewer service to the Las Flores/Rambla Pacifico area, Carbon Mesa, Kellers Mesa (along Sweetwater Canyon Road) and some areas between Pacific Coast Highway and Malibu Road.
In those neighborhoods, the report says, high ground water "is a major contributing element to instability problems." Eliminating septic tank effluent in favor of sewage flowing in enclosed pipes to a distant treatment plant "will significantly benefit the stability," the report says.
The first phase of the proposed system was to have served only the Topanga area, Big Rock, the Malibu Civic Center, Latigo Point and houses bordering Pacific Coast Highway.
The changes in the report bring the number of properties recommended for first-phase assessments to about 1,700. The first phase, expected to be built about 1990 or 1991, would stretch from Topanga Canyon to the west end of Malibu Road. The second phase, which is expected to be built about 20 years later, would extend the system west past Trancas Canyon.
Sewage would be transported in pipes under Pacific Coast Highway, most of it to a new treatment plant in Corral Canyon. Sewage from areas east of a major landslide at Big Rock would be sent to the Hyperion treatment plant near Los Angeles International Airport.
The consultants' latest report focuses mainly on the pipes that would bring sewage from neighborhoods to the main pipelines under the coast highway. These secondary pipelines are known as collector sewers.
Consultants wrote that they refined their cost estimate of that part of the system from $20.2 million to $25.6 million.
The estimate of individual costs ranges from $13,000 to $26,000, which would include the assessment and the cost of house connections. That connection cost, which covers the pipe laid on private property, is projected by consultants at between $2,000 and $5,000.
In the most recent report, the consultants found that about 15% of the properties will require the most expensive type of connection, which pushes sewage uphill to the main pipeline. Most of those properties are south of Pacific Coast Highway.
The report also says construction of the collector sewers, which will take one month in some neighborhoods and four months in others, will cause traffic problems in residential areas and at the Civic Center, where county government offices and courts are located.
Some narrow streets may be temporarily closed to traffic. Driveway entrances and intersections may be blocked at times by construction crews.
As in earlier reports on the impact of building the main pipeline along the coast highway, consultants recommend limiting construction to weekdays from mid-September to mid-May to avoid affecting summer and weekend beach traffic.
Leon Cooper, president of the Malibu Township Council, said he had not yet received the latest report. But he said he had concerns about construction of sewer lines in unstable areas and that he was not surprised that the estimate for collector sewers had increased.
"I'm frankly distrustful of any numbers" from the county and its consultants, he said.