Ten years ago - Oct. 12, 2006 - Philadelphia Mayor John F. Street signed an executive order authorizing the creation of a civic vision for the Central Delaware.

Of all of the guiding tenets that emerged from that public planning process, captured in the landmark 2006-2007 A Civic Vision for the Central Delaware, the extension of Philadelphia's archetypical street grid to the waterfront is the single most important principle to inform the future development of the waterfront - bar none. It is also one of the more difficult to enact politically and the one that the city and the new Delaware River Waterfront Corp. have shied away from tackling. Perhaps not so coincidentally, some developers of large waterfront parcels along the Delaware are now trying to exploit this lack of a street grid by proposing car-oriented development that is antithetical to the values of the vision.

Philadelphia's signature calling card is undoubtedly the plan for Philadelphia that was created by Thomas Holme and William Penn in 1682. A work of landmark urbanism, the Penn/Holme plan influenced the quintessential American street grid for English-speaking cities in the New World. This radical grid of streets and five public parks, stretching over two square miles from the Delaware to the Schuylkill, is the same grid of streets and parks within which we live, work and play to this very day.

Penn had a very different idea of what would be built within his grid from what we see today. He imagined large houses set within ample garden lots spreading from river to river in a kind of exurban idyll. The housing market soon took care of that, and the grid was immediately subdivided and developed on a micro scale along the Delaware. Penn could not have foreseen that a building of the size and scale of the new, 1,121-foot Comcast Innovation and Technology Center would rise within his grid the same way as the tiny houses on Elfreth's Alley do.

But therein lies the beauty and genius of the grid. It is eminently flexible. It is human-scaled. And, it is what gives Philadelphia it's je ne sais quoi.

Over the centuries, the Delaware waterfront went from being Philadelphia's front door to being its thrumming industrial dockyards. Following World War II, as industry left Philadelphia and the middle class began to move to the suburbs, planners such as Ed Bacon sought to create a modern waterfront. Ironically, they also placed the interstate along the river. This singular act of urban cruelty ensured that the large post-industrial parcels along the shoreline would never be easily accessed on foot, as one has to battle more than 16 lanes of highway and Delaware Avenue traffic in some places.

For the Delaware riverfront to be truly integrated into the life of the city, we must extend the street grid both over to the river and along the river - it is within the power of a city to do just this; to plat or map its desired city form and compensate owners of private property when these streets become part of the public right-of-way.

Without this extension of the street grid - and without finding ways to reduce or eliminate the impacts of I-95 (which is being planned right now by PennDOT, to be rebuilt over the next 20 years), the Delaware riverfront will continue to be seen by developers as isolated and car-oriented. No amount of parks, trails and bike lanes will change that. We see that today with plans for the parcel at the base of Washington Avenue and for the former Foxwoods site between Reed and Tasker. These large lots - each more than 14 acres, isolated by the high-speed chasm of the highway and Columbus Boulevard and surrounded by ill-informed big-box retail land-use decisions in the 1990s and early 2000s - have no official street grid to guide the development. Rather, we have a master plan that suggests streets to extend without the teeth of the city's official street plat, and are leaving it up to the development community to be good planners and hope that they create a walkable waterfront.

The waterfront has come a long way in the past 10 years, with a master plan and new zoning regulations that codify the plan and beautiful pier parks and public spaces that show what the future could be all along the river. But, as we've seen, the development community already is requesting variances, which City Council and the Zoning Board of Adjustment continue to entertain, despite official zoning controls. Some developers claim that the Delaware will always be car-oriented. And as long as the city and the waterfront corporation continue to turn a blind eye to creating the street grid and forcing I-95 to go on a road diet, they may be right.

High-quality public access and connectivity to the Delaware River are too important to negotiate on a parcel-by-parcel basis. It's time for the city to stop bargaining what form our city will take and instead demonstrate the leadership our citizens have entrusted it with. They need only look to our founder, Penn himself, for a model of how to balance private interests with public good to create a form that is timeless, urban, urbane and classically Philadelphia.

Harris M. Steinberg is executive director of the Lindy Institute for Urban Innovation at Drexel University. He led the civic engagement process that culminated in the Civic Vision for the Central Delaware.