Porter Ranch Plan to Add Smog, Cars, Study Says : Development: Growth in the northwest Valley will cause massive congestion and tax city services in the next 20 years, report claims.

Development in the Chatsworth-Porter Ranch area over the next 20 years will increase smog, harm plants and wildlife in the Santa Susana Mountains, and strain city services, according to a new environmental study.

The additional residences, businesses and industries, many of them in the massive Porter Ranch development, will generate a demand for nearly 26.4 million gallons of water a day, said the draft of an environmental impact report prepared for the city by EIP Associates. The development also will cause massive traffic congestion that could be alleviated only by millions of dollars in street improvements, the report said.

The study, presented during an informal workshop at Lawrence Junior High School on Tuesday, reviewed consequences to the northwest San Fernando Valley if the city adopts the modified Chatsworth-Porter Ranch District Plan, introduced to residents two years ago.

The revised plan, which modifies the original district plan completed in 1974, sets standards for future growth and development in an area bounded by Roscoe Boulevard on the south, the city limits on the north and west, and Tampa Avenue on the east.

The environmental report found that the new development would increase traffic, straining already overcrowded intersections and causing more smog. Also, the Police Department would have to hire 17 officers to keep the department to the ideal ratio of three officers for every 1,000 people in an area, the report concluded.

Despite the problems, city planners said the new plan is better for the community because it allows less industrial development.

The 1974 plan allows six times as much industrial development per acre as that existing in the area now, city planner Philip Hall said. The revised plan would allow no more than double the current density, he said.

The new plan, however, allows for about 25% more housing on residential land--enough for about 5,600 more people--than allowed under the 1974 guidelines, the environmental impact report said. The new plan also converts 12 acres surrounding Mason Avenue and Devonshire Street, now zoned for mixed residential and commercial use, to commercial use only.

The district plan revisions do not include the approximately 3,395 residences and 6 million square feet of commercial development proposed for the Porter Ranch project. The 1974 plan for that area was revised last year when the City Council approved the project. The environmental report, however, considered the effects of the entire plan, including Porter Ranch.

Hall and city planner Frank Fielding said most of the additional traffic foreseen in the environmental report would result from increased growth in the Chatsworth industrial area rather than from Porter Ranch.

The revised plan represents several years of work by a citizens’ advisory committee appointed by Councilman Hal Bernson, planning officials said. A public hearing on the plan and environmental report is scheduled for 5:30 p.m. Tuesday at Lawrence Junior High School.