Study Recommends State Water Hookup : Castaic Lake: The report says the 38-mile pipeline is the cheapest option to raise supplies and would have fewest environmental effects.

A report released Thursday concludes that the best way to increase water supplies in western and northern Ventura County is to build a $90-million pipeline to link up with the state’s water project at Castaic Lake.

The 38-mile pipeline stretching from the Ventura/Los Angeles County line to the city of Ventura is the least expensive alternative of six plans considered and would have the fewest harsh effects on the environment, according to the study.

A seawater desalination plant would cost an estimated $215 million, more than double the cost of the preferred option, according to the report prepared for the Casitas Municipal Water District, the city of Ventura and United Water Conservation District.

The three entities commissioned the study last year to determine the best way to augment the limited water supply for Ventura, Port Hueneme, Channel Islands Beach Community service district, Santa Paula, Fillmore and Piru, which have a total of about 187,500 people.

The city of Ventura is also considering building a pipeline or desalination plant on its own.

But a draft summary of a separate report, also released Thursday, concludes that the city of Ventura should join Casitas and United in a joint project to save money, said Shelley Jones, director of public works for the city of Ventura.

“There is significant savings working with all the agencies,” Jones said. “We have thought all along that there are economies of scale.”

The Ventura City Council will hear presentations on both reports at its meeting Monday. All three agencies are expected to decide by June whether to move forward with a plan to import state water to put a measure on the November ballot.

The cost for the new water could double monthly bills in the city of Ventura, Jones said. Elsewhere, monthly increases would range from $5 to $13 per household, the report says.

“It’s going to be expensive, but at least it’s going to be (more) water,” Jones said. “The need was certainly demonstrated in these past couple of years, and the weather patterns can repeat themselves.”

The study evaluates the impacts on the environment of plans ranging in cost from $90 million to $215 million. In one scenario, the pipeline snakes from the county line to Santa Paula, where it turns north and west to Ojai.

In another plan, preferred by the United Water Conservation District, the state water comes not from Castaic Lake but from Pyramid Lake, farther north. The water would be released from Pyramid Lake, down Piru Creek to Lake Piru, a reservoir run by the United district. But the city of Ventura would not support the plan because of the lower quality of the water, Jones said.

In the preferred option, which would cost $872 per acre-foot, the pipeline would begin near the Ventura/Los Angeles County line, hooking up to an existing pipeline leading east and north to Castaic Lake. Castaic Lake is connected by the California Aqueduct to Northern California water supplies.

From the county line, the pipeline would wind westward along the north side of the Santa Clara River, with turnouts in Piru, Fillmore, Santa Paula and Port Hueneme before it reaches its terminus at the city of Ventura.

The city of Ventura would then decrease its demand from Lake Casitas near Oak View by 5,000 acre-feet per year. That would augment the Casitas district supply, even if it never receives a drop of the imported water.

Because all of the proposed pipelines run adjacent to the Santa Clara River or the Piru Creek, each would disturb wetlands habitat, some of which is home to endangered species of birds and plants.

But the report concludes that all of the impacts could be reduced to an insignificant level. Other potential problems with the pipeline include danger of earthquake from the many active faults that cut across the region, the report said.

The report’s estimate that desalination would cost $215 million to produce up to 20,000 acre-feet of water is in sharp contrast with the city of Santa Barbara, which reports that it built a seawater desalination plant for $30 million.

But officials at Casitas said that not all the cost factors were considered in the Santa Barbara plant, including the cost of land that was already owned by the city of Santa Barbara. Also not included in the cost of the plant are additional environmental studies and the cost to fix potential problems that the studies may uncover.

The summary of the draft released by the city of Ventura on Thursday concluded that if the city did decide to build a project by itself, the cost of a much smaller desalination plant would be about equal to that of a pipeline, Jones said.

Each would cost about $100 million. The ongoing cost per acre-foot of water from the desalination plant would be about $1,800. But that water would be blended with water pumped from the ground, bringing the cost of the water down to about $1,100 an acre-foot, Jones said. The cost to import state water would also be about $1,100 an acre-foot, he said.