Las Virgenes Population Spurt Foreseen : Rural Sewer Need Expected to Triple

Sanitation officials bracing for explosive growth in a rural area between Woodland Hills and Thousand Oaks said Tuesday that they may have to triple the size of their sewer system to accommodate thousands of homes and businesses.

Las Virgenes Municipal Water District administrators said they may be forced to build a network of small satellite sewage-treatment plants in Malibu, Agoura, Calabasas and eastern Ventura County to handle waste flow.

The plants would supplement the region’s lone waste-water facility, a controversy-plagued treatment plant in a Calabasas valley at the northern end of Malibu Canyon.

Officials said they have no timetable for the anticipated development boom. But they said their own recently completed demographic analysis suggests a threefold increase in population is coming in a 156-square-mile area of western Los Angeles County and eastern Ventura County.

Sanitation engineers said they will begin planning for the population increase with a public workshop at 8 p.m. Monday at the Las Virgenes district headquarters in Calabasas. Hearings will follow in the spring.

Slowdown May Be Sought

Officials acknowledged that the hearings could bring calls for a slowdown in sanitation-line construction by environmentalists and others who view the growth statistics with alarm.

Under state and local subdivision laws, cities and counties cannot issue building permits unless developers prove their projects can hook up with existing sewer lines or unless they build approved backyard septic systems. In urbanized regions and difficult geologic areas, private septic tanks are not allowed.

Slow-growth advocates in Agoura and Calabasas argued in the late 1970s that the Las Virgenes district should limit expansion of sewage-treatment facilities as a way of controlling home construction in the area.

Malibu residents took a similar stance last month when they urged Los Angeles County supervisors to reject a planned $86-million sewer system for the beachfront area. Opponents complained that the system would induce growth in Malibu. Supervisors voted Oct. 22 to postpone the matter, effectively killing the sewer plan.

Las Virgenes officials say their long-term sanitation expansion planning has nothing to do with land-use control--something handled by cities or county planning commissions.

“We’re not a planning body,” said Edward E. McCombs, manager of the Las Virgenes district. “We want to have thought the situation through and be ahead of the game.”

The sanitation facilities are jointly owned by the Las Virgenes district and the Triunfo County Sanitation District of Ventura County. They are operated for the partnership by Las Virgenes engineers.

The districts’ population study, finished two months ago, concluded that 189,600 people will live in Calabasas, Agoura, Agoura Hills, Westlake Village, Bell Canyon, Hidden Hills, Oak Park, eastern Thousand Oaks, Lake Sherwood and the mountainous northern Malibu area.

That total is about 50,000 more than previously predicted. The region’s population now is estimated at about 69,600.

The eventual population would probably generate 22 million gallons of raw sewage a day, contrasted with current flows of less than 8 million gallons, according to Las Virgenes officials.

The existing flow is easily handled by the district’s Tapia Sewage Treatment Plant above Malibu Canyon. Las Virgenes officials say they have begun a $2-million construction project to expand the Tapia plant to a capacity of 10 million gallons a day and have room to add 6 million gallons in the 1990s.

Promise Given

But officials have pledged to environmentalists and residents of the small mountain community of Monte Nido that the nearby plant will not be expanded beyond the 16-million-gallon level.

In past years, a series of leaks and floods at the plant prompted complaints and several investigations by state water-quality officials. They also led to cries of outrage from beachfront homeowners in Malibu, where untreated sewage washed into the ocean.

Las Virgenes engineers say they have solved the problems by installing pipelines, treatment filters and a sturdy flood wall to prevent Malibu Creek from overflowing into the Tapia plant during stormy weather.

Although further expansion of the Tapia plant is an option that will be studied in coming months, construction of extra satellite plants is more likely, officials said Tuesday.

McCombs said potential satellite sites include a 1-million-gallon facility near the Church of Perfect Liberty in the Malibu mountains south of Westlake Village, a 4-million-gallon plant off Kanan Road south of Agoura Hills, a half-a-million-gallon plant in the Oak Park area of Ventura County, a 1-million-gallon facility in the Ahmanson Ranch area in north Calabasas and a 4-million-gallon plant next to Las Virgenes Road in Calabasas.

Other Choices

Other options include attempting to divert 3-million gallons of sewage a day to the City of Los Angeles, he said.

If satellite plants are built, they will not be the first small-scale treatment facilities dealt with by Las Virgenes officials.

The agency briefly operated small developer-built treatment plants in the Mulwood and Malibu Canyon Park sections of Calabasas for a time in the 1960s. The plants were closed for economic reasons when the neighborhoods were connected by pipeline to the Tapia plant.

In the early 1980s, Las Virgenes officials briefly considered building satellite plants in the Agoura Hills area as an alternative to the current Tapia plant expansion. That proposal was dropped when nearby homeowners reacted icily to the idea.

Although the Tapia plant has largely been built with federal anti-pollution money, all further sanitation projects will be paid for with developer fees, McCombs said.