Starting this month, about a third of Simi residents must reduce their water consumption by 15 percent each billing cycle, according to a new rationing plan by Golden State Water Company.

The California Public Utilities Commission last week approved Golden State's water shortage plan, which calls for mandatory conservation and imposes fines and penalties on those customers who are not in compliance.

About 70 percent of Simi residents get their water through Ventura County Waterworks District No. 8, which is headed by the city, while the rest receive it from Golden State. Both the city and Golden State purchase water from Calleguas Municipal Water District, which gets its water from the Metropolitan Water District. Golden State serves about 13,300 households in Simi Valley.

Because Calleguas implemented mandatory water use allocations for all retailers beginning this month, Golden State likewise had to institute a rationing plan.

In May, the City Council passed water conservation ordinances for both the waterworks district and the entire city. Skip Faria, superintendent for Golden State's Simi Valley customer service area, said the company worked with the waterworks district in crafting its plan to make the two as similar as possible.

"(We) have been trying to work together to make the plans as close as possible to avoid confusion because sometimes we service one side of the street and Waterworks District 8 serves the other side," he said.

Both plans include limits on water use, prohibit runoff from irrigation, set fines for violations and have progressive stages of enforcement. But the major difference between the plans is that, unlike Golden State, the waterworks district has not given customers a mandatory water reduction percentage.

Each household's allocation is based on its historical average from 2004-06. For example, if a property's average over those base years for July-August was 100 Ccf, then the allocation is 85 Ccf.

There are penalties for going over one's allocation. Usage within a household's allocation will be billed at the regular rate of $2.48 per Ccf (1 Ccf equals 748 gallons). But each unit over an allocation will be charged two times the regular rate, or about $5. In addition, every unit that is 15 percent or more over the allocation will be charged three times the regular rate.

Current and future allocations will be printed on customers' billing statements.

Faria said the 2004-06 timeframe was chosen because many customers have tried to conserve water in the past three years. If 2006-08 had been used as the baseline, then those customers who heeded the call to conserve during that time and thus had lower averages over that period would have even lower allocations now.

"The whole system was put together to be as fair and equitable as possible," he said.

Golden State's plan has seven stages, with each calling for a greater reduction in water use and further restrictions on outdoor watering. At implementation of the plan, the water company will already be at stage 3, which not only prohibits outdoor watering from 9 a.m. to 5 p.m. but allows outdoor watering only every other day, no more than three times per week.

The fine for violating nonessential water use restrictions like this one is $100 in stage 3 and increases $50 for every stage after. However, Golden State officials hope not to move to the next stage.

Customers can apply for an exemption, but Golden State is encouraging residents to first give the new program a try. Dewey said many people have already responded to calls for voluntary conservation and will find they've already changed their behavior to meet the allocation.

Faria said most people will find it easiest and most beneficial to reduce their outdoor water use.

"In Simi Valley, about 80 percent of the water is used outside the home, especially in the summertime when it's so hot," Faria said. "Adjustments on water time and frequency outside pay big dividends."

Though the water shortage plan will expire once the statewide drought has ended, Golden State will move to a tiered rate structure in September to promote long-term conservation.