The collapse of the I-35W Bridge in Minneapolis in 2007, killing 13, was both a real and symbolic disaster. The word "infrastructure" quickly became a catch-all to describe a nation literally crumbling after decades of neglect - the philadlephia region included.

"Infrastructure" includes far more than bridges - it encompasses the region's roads, rails, waterways, utilities and open space. The city's Metropolitan Moment demands that we see all of these as part of a comprehensive and integrated system.

This region has more than its share of challenges.

* What was once a major shipping and rail center, exporting Pennsylvania coal as well as goods from the "Workshop of the World," was made obsolete by other fuels and deeper oceanfront harbors.

* The city's combined water and sewer system flows through century-old pipes, and their capacity is overwhelmed by every heavy rain, flooding streets and polluting rivers.

* The zoning code is antiquated and undergoing revision. Alan Greenberger, head of the Philadelphia Planning Commission, uses the current zoning map to illustrate just how out of balance old codes are. For example, the city's industrial area includes 21,000 acres, more more than twice the acreage of the Fairmount Park system.

The Planning Commission is working with Philadelphia Industrial Development Corporation (PIDC) on a study that inventories and makes recommendations for industrial land use throughout the city.

Infrastructure and land use go hand in hand.

Another priority for planning will be a focus on mixed-use zoning - how to develop and use a property in a way that includes different functions and uses.

Think of "It's a Wonderful Life" when George Bailey, with a new lease on life, runs down the avenue in Bedford Falls, yelling Christmas greetings to all the people and buildings, from the movie house to the cops to the "wonderful old Building and Loan." A mixed-used neighborhood is really just your basic Main Street USA. Or Main Street in Manayunk, for that matter. It's Germantown Avenue in Chestnut Hill and Mount Airy. Penn's campus, and, increasingly, Drexel's and Temple's.

Mixed use is really the essence of an old city like Philadelphia. But it also answers very modern needs.

"Mixed-use development is the best land-use policy and planning tools that we have for sustainability," said Natalia Olson de Savyckyj, an international planning specialist with the architectural firm H2L2, and a member of both the Zoning Code and City Planning commissions.

"This density is also a good thing for security reasons. People [feel safe] when they're near other folks, and when there is a mix of uses, there is also efficient management with lower energy usage."

THERE ARE good examples of new mixed-use development around the city.

Peter Kelsen is a veteran real-estate and zoning attorney at Blank Rome LP who also serves on the current Zoning Code Commission. Kelsen points to Two Liberty Place as a great example of an office tower seamlessly incorporating a full-scale modern hotel with interesting street-level retail that joins internal mall-like spaces. And now it's got successful condominiums, too, though only available to the wealthy (a mix of incomes and housing styles is also a major part of good mixed-used development).

He also likes the way developer Tony Goldman tackled the area roughly bounded by 13th, Chestnut, 11th and Walnut streets, just south of the Market East area. "With residential and retail and professional offices mixed in, within buildings or next to each other, he's created a very vibrant neighborhood because they all feed off each other," Kelsen said.

But for every Two Liberty or Comcast Center, there are a dozen Center City office buildings along Market Street or JFK Boulevard that are barren after 6 p.m. and on weekends.

And Delaware Avenue has suffered a long history of both neglect and lack of planning that began when I-95 cut the waterfront off from the rest of the city. Today, big box stores and high rise towers further cut people off from access to the water.

Fortunately, that's about to change. The Civic Vision for the Central Delaware, a project coordinated by Harris Steinberg, executive director of PennPraxis, the clinical arm of the University of Pennsylvania design school, proposes an extension of Center City to the eastern shoreline.

The plan includes a tight street grid that would expand downtown by 30 percent with mixed-use development on the riverfront. New housing on the Delaware would shift populations to the city, easing the jammed expressways to the suburbs. The plan also calls for a light-rail passenger line, and a necklace of riverfront parks.

And hope is at hand for the river itself. The much-debated dredging project will help create a world-class container-shipping facility in South Philadelphia.

The health of the river and the water/sewer system could be improved if Howard Neukrug gets his way. Neukrug, director of the Philadelphia Water Department's office of watersheds, has a multi-pronged approach, involving gray infrastructure (the old pipes), green infrastructure (environmental management of storm water) and blue infrastructure (the waterways).

MUNICIPAL leaders are paying attention to these visions. The creation of the Zoning Reform Commission may pave the way for big changes.

Nationally, a proposal for a National Infrastructure Reinvestment Bank that would invest $60 billion over a 10-year period for highways, technology and other projects could provide much needed funds for the city overall.

But now, one of Philadelphia's greatest resources is a bank of ideas. There is a timely intersection of planners, developers and municipal leaders with a common mission for a smarter, more-efficient and sustainable city that has the added benefit of being built for humans. *