Mayor Rahm Emanuel introduced his plan to revamp the city’s zoning rules for the floor area bonus system, which allows downtown construction projects to increase their height and size in exchange for voluntarily paying into a fund that would help support commercial projects and job creation in the city’s poorest neighborhoods. Aldertrack will provide a more in-depth report on the ordinance tomorrow, but here are some of the highlights from our preliminary read of the measure.

The plan completely revamps the floor area bonus system, which currently gives developers up to 20 different ways that developers can add more density than is allowed under the zoning code. The Emanuel Administration anticipates the changes would net the city an additional $50 million over the “next several years.”

It replaces bonuses with three separate funds that developers would voluntarily pay into to build taller or bigger buildings in the city’s downtown area, and would simultaneously expand the boundaries of the downtown district by 25 percent. New projects in the expanded D-designated zoning district would be eligible to take advantage of the bonus system.

The formula the city would use to calculate payment is based on an existing formula the city uses to calculate the cost of each additional square foot of space added to a project:

Cost of 1 square foot of floor area = 80% x median cost of land per buildable square foot

Eighty-percent of the money collected through the new voluntary bonus would go into a Neighborhood Opportunity Fund. That pot of money would support projects within “underserved neighborhood commercial corridors,” and could include grocery stores, restaurants, and cultural facilities. The Department of Planning and Development would be in charge of administering the fund and all projects funded under the new initiative. But any project that costs more than $250,000 would need approval from the full City Council.

The remaining funds collected would be evenly split among a citywide Adopt-A-Landmark Fund and a Local Impact Fund. As the zoning code is currently written, the Adopt-A-Landmark bonus could only be used for a city-designated landmark located within 2,000 feet from the development site. The changes would make that money available to any city-designated landmark.

The money collected for the Local Impact Fund would help support improvements to local transit, streets, open spaces, river walks and other public amenities located within 2,640 feet of the development site.

Similar to the city’s affordable housing requirements, payment would be due upon receipt of a building permit, unless the project is designated a planned development to be constructed in phases. Phased projects would pay on a “pro-rata” basis for each new permit applied for.

Six aldermen co-sponsored the plan: Zoning Chairman Danny Solis (25), Pat Dowell (3), Emma Mitts (37), Michael Scott, Jr. (24), Michelle Harris (8), andWalter Burnett Jr. (27).