he Bloomberg administration moved ahead yesterday with its plans to transform an abandoned elevated rail line into a 1.6-mile-long park and make it the centerpiece for new commercial and residential developments along the western edge of Chelsea.
At a news briefing, city planning officials unveiled a detailed proposal to carve out a special redevelopment district along 10th and 11th Avenues, between West 16th and West 30th Streets. The plan is part of the city's overall effort to encourage and control development on the West Side, Manhattan's most undeveloped area.
Zoning there would be changed from manufacturing and commercial uses to allow up to 4,200 units of new housing, primarily along the avenues.
Running through it would be the High Line, a railroad viaduct from the 1930's that extends from Gansevoort Street to 34th Street. Development along the line would be restricted to protect the open views. The plan also restricts development of midblock areas throughout the district to preserve the low-lying warehouses that are home to more than 200 art galleries.
In a concession to those who own land directly under the High Line, the proposal would allow those property owners to sell their air rights as much as one million square feet to high-rise developments on the avenues.
Amanda M. Burden, the city's planning director, said the High Line would open up parkland in a part of the city that does not have enough while adding character to a once thriving manufacturing area.
Members of Manhattan Community Board 4 said, however, that they were concerned about the proposed height of some of the buildings and wanted more assurances that there would be enough housing at prices for lower- and middle-income people. City officials estimate that developers could set aside as much as a quarter of the new units at below market rates.
"There really are some very good things there, but there are still some glitches," said Lee Compton, co-chairman of the board's Chelsea preservation and planning committee.
City officials will seek comments on their proposal at a public hearing on Oct. 2, and could adopt the special district as early as next fall. The final proposal would have to be approved by the City Council.
The neighborhood has been much coveted by developers in recent years, prompting the city to insist on an overall plan for the area. Much of the discussion has centered on the future of the High Line.
The last boxcar rumbled over the line more than two decades ago, and many New Yorkers have pushed to save the rusty relic. The rail line has even inspired its own group of patrons, the Friends of the High Line, which has enlisted the help of celebrities like Edward Norton to drum up support for preservation efforts.
Council Speaker Gifford Miller, who keeps a giant color photograph of the railway in his home, has committed to spending more than $15 million over the next four years to transform the High Line into a public space. City officials estimate the project's cost at more than $65 million.
"I'm probably the High Line's biggest supporter," Mr. Miller said. "I've had the opportunity to walk on it, and it's a transforming experience. You see the city in a different way than before."