On a recent Wednesday evening, with hours of summer daylight left, dozens of people were out enjoying the Bloomingdale line, a dormant railroad right-of-way that runs 2.7 miles across the northwest side, 15 feet above its namesake street. They strolled, they jogged, they cycled, and they exercised their dogs, oblivious not only to the carpet of glass, weeds, and garbage but to the law: the Bloomingdale line is private property, and everyone on it was trespassing.

The idea for the conversion was first documented in a 1997 update of the Chicago Metropolitan Agency for Planning’s regional trails plan, which noted the line’s potential as a greenway. The last train came through in 2000, and in 2002 the city began planning an elevated multiuse trail to run from Ashland to Ridgeway (three blocks west of Central Park), connecting Bucktown, Wicker Park, Humboldt Park, and Logan Square. In 2003 advocates formed Friends of the Bloomingdale Trail to promote the concept and prevent the railroad embankment from being leveled and the land sold to developers. The following year the Chicago Plan Commission approved the trail as part of a plan to remedy the shortage of open space in Logan Square, which has the city’s second-worst parkland-to-people ratio.

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In November 2008, the city issued a request for proposals for the preliminary design and engineering for the trail. According to CDOT’s Brian Steele, 23 firms applied and five were selected for further screening. In mid-July the city announced its choice: Arup, a London-based multinational firm whose projects include the Sydney Opera House, the “Water Cube” aquatics center for the Beijing Olympics, and the LEED Platinum-certified California Academy of Sciences in San Francisco. Arup’s nine subconsultants would include Chicago’s Ross Barney Architects, which worked on the Wacker Drive reconstruction and Chicago Riverwalk, and Brooklyn’s Michael Van Valkenburgh Associates, a landscape design firm that worked on New York’s High Line, a park similar in concept to the Bloomingdale Trail.

The Bloomingdale Trail is often compared to the high-profile High Line, which in June opened a half-mile stretch of its planned 1.5-mile conversion of an old elevated rail line on Manhattan’s lower west side. The new space features native plants and shade trees, sleek surfaces, an undulating planked walkway, and lots of seating, including reclining wooden deck chairs for contemplating the unique city views. It’s already had half a million visitors.

Joan Fox says her house, which comes as close as two inches to the trail, has been hit by rocks and Roman candles fired from the trail, and taggers have defaced the back wall three times this year, leaving graffiti below her three-year-old son’s window. “That makes me really nervous,” she says. A group of eight or nine “squatters” often camps out near the house, she says, smoking, drinking, and playing music, although she doesn’t think they’re to blame for the vandalism. “They urinate by my son’s bedroom window and I can hear them snoring,” she says. “I call the police and they’re usually very responsive but sometimes after an hour I have to go out at 10 PM and ask them to move. They’ve been cool about it but it could have been a lot worse.”

Fox says she and about 15 neighbors sent a letter to 32nd Ward alderman Scott Waguespack on May 31 requesting action to secure the Bloomingdale line. On July 7 Waguespack held a closed meeting to discuss the issue with representatives from other affected wards, the railroad, the 14th District police, CDOT, Friends of the Bloomingdale Trail, and the Trust for Public Land.

Colón did tell me a week later that he’s interested in cheaper, quicker ways to build the trail than the current projections allow. “I’m not an engineer but I do see people using the line right now,” he said. “I’d like to know, could we start with ten million dollars and get the trail up to an acceptable level of safety and then sort of pay as we go to improve it?” He also told me he and Waguespack discussed this possibility while cycling together on the boulevards during the Active Transportation Alliance’s Open Streets event on August 1.