The intersection of Market Street and Van Ness Avenue looms large on the map, with two of San Francisco’s best-known and broadest thoroughfares overlapping at a sharp angle.

The reality isn’t nearly so grand — a crossroads marked by a car dealership, a doughnut shop and two drab office blocks. Nearby, parking lots and ratty alleys rub against buildings that never aimed high and now are worn down. The street life is spotty at best, sketchy at worst.

All this would change under an evolving city plan that includes a cluster of towers on the skyline, a variety of public spaces below and as many as 7,280 housing units in between. And the first major project within the area could be approved next week — one that hints at a livelier future, but also shows how tough it is to fit ambitious visions into a complex setting.

If nothing else, the proposal for 1500 Mission St. — down the block from Market and South Van Ness Avenue — that goes to the Planning Commission on March 23 shows how this part of San Francisco could be transformed.

The 2.5-acre site is home to Goodwill Industries, which sells donated goods within a two-story concrete-block structure at the corner of Mission and South Van Ness, and uses a former Coca-Cola bottling plant at 11th and Mission streets as a warehouse. There’s a large parking lot in between.

By contrast, developer Related California’s 1500 Mission would replace the Goodwill store with a 39-story apartment tower. A 16-story office complex for city employees would line the north and east sides of the site. In between, there would be walkways lined with retail space in the base of the residential tower and meeting rooms, and an art gallery in the office building.

A 40-foot-deep portion of the old bottling plant along Mission Street would be retained, including the streamlined clock tower above the entrance.

Aesthetically, there’s a lot to like about the design by the San Francisco office of Skidmore, Owings & Merrill.

The residential tower would be wrapped in precast concrete, a light cloak that would part above the corner of Mission and South Van Ness to reveal an angled slope with landscaped terraces within. The city office building would be clad all in glass, but at a low enough height that it would be a backdrop rather than a centerpiece, and translucent glass fins would add depth while deflecting harsh sunlight.

The walkways, meanwhile, would make it easier for pedestrians to navigate the large and awkwardly shaped block. And the restoration of the clock tower — itself a 1941 makeover of an industrial structure erected in 1925 — preserves one of the few visual landmarks in the immediate area.

To planners, the mix of forms and materials and activities anticipates what they hope to see elsewhere in what they’re calling the Hub, a onetime nickname for the Market-Van Ness crossroads that fell out of use generations ago. Planning began last year, and a final set of recommendations is expected this summer so that environmental studies can begin.

The collision of large and small blocks, and large and small buildings, with the boutiques of Hayes Street to the north and big-box stores like Costco to the south, is also what 1500 Mission’s developer describes as the appeal of an area that now can be a confusing traffic-clogged void.

“This neighborhood, because of its adjacency to the Mission and Hayes Valley and Civic Center, has the potential to really feel like part of San Francisco,” said Matthew Witte of Related California.

But fitting new towers into this patchwork quilt isn’t simply a question of aesthetics. Wind also factors in.

That’s why 1500 Mission would include a canopy of overlapping metal triangles that would extend as much as 20 feet beyond the edge of the building. It’s a striking visual gesture driven by necessity — to dampen the winds that barrel in from the ocean through Hayes Valley and then careen down Van Ness, deflected south by taller buildings already nearby.

Under planning regulations established in 1985, new buildings in most of downtown aren’t allowed to make wind conditions worse on public sidewalks. That’s why the two new buildings at 1500 Mission drop to three stories along South Van Ness, to reduce the potential downdraft at the main entrance to the site. It’s also why the tower is pulled back 15 feet from the sidewalk — the canopy would serve as an artful muffler while providing afternoon shade.

“The idea was to slow down and redirect the wind,” said Mark Schwettmann, part of Skidmore’s design team. “Wind is basically lazy. It goes where it’s easiest to go.”

A different back-and-forth is the partial preservation of the former Coca-Cola building. And the solution hasn’t made everyone happy.

By retaining the distinctive clock tower, and most of the facade along Mission Street, an architectural thread from the past would enrich the mosaic of what’s to come. It’s also the part of the building that people know the best.

But this would be a skin-deep salvation, with much of the exterior demolished and nothing left of such aspects as the structural trusses inside. The city’s Historic Preservation Commission opposes the compromise as a well-meaning gesture that falls short. So does San Francisco Heritage, a preservation advocacy group.

As facadism goes, this could turn out to be one of the better examples. The 1500 Mission design could also help bring life to nearby 11th Street, as dreary a block as any downtown. Still, it’d be nice if there were more depth. But that would hinder the city’s office-space needs, no doubt a factor in the final design approach blessed by planners.

The balancing acts at 1500 Mission are indicative of what lies ahead through the Hub as a whole.

Wind is an obvious example, since every new tower will face the same challenges. This includes the next tower likely to move forward — Build Inc.’s 39-story One Oak, designed by SCB and Snøhetta with its own set of canopies at the base of the carefully rounded shaft.

And more towers will follow. The area already was rezoned in 2009 to allow a quartet of 400-foot towers that would signal the prominence of the Market-Van Ness intersection. The Hub plan would lift heights further, adding several midsize towers to the west and allowing three sites at the intersection to reach peaks as high as 600 feet.

The urban design argument is that the changes would allow for a more distinctive and tapered neighborhood skyline. But political factors are at work as well.

The extra heights would allow as many as 1,750 more housing units — one-third of them affordable — than what would fit within the 2009 framework. The new plan would also introduce a “community facilities district” fee that could raise $200 million to help fund a landscape of narrowed boulevards and small plazas.

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These changes can be beneficial. But as the city revises plans for this small district and other parts of San Francisco, it isn’t enough to say that density is good as long as we get measurable benefits in return.

If density itself becomes the goal, there’s a danger. San Francisco could pack things in so snugly that when the construction dust settles, what we see around us won’t be the city that we love.

John King is The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron

More information on the planning effort: www.sf-planning.org/market-street-hub-project

John King is The San Francisco Chronicle's urban design critic, taking stock of everything from Salesforce Tower to sea level rise and how the pandemic is redefining public space. A two-time Pulitzer Prize finalist and author of two books on San Francisco architecture, King joined The Chronicle in 1992 and covered City Hall before creating his current post. He is an honorary member of the American Society of Landscape Architects.