DES MOINES, Iowa (AP) — Hubbell Realty Co. is gearing up to break ground on downtown Des Moines' biggest housing development yet — a project that will add the equivalent of a small city to the north bank of the Raccoon River.

Called Gray's Station, the project aims to turn 75 acres of abandoned rail yards on the north bank of the Raccoon River into an upscale neighborhood with more than 1,100 housing units, some small commercial districts and a network of parks linked to a new pedestrian bridge to Gray's Lake Park.

"It's a new downtown neighborhood," said Rick Tollakson, CEO of the West Des Moines-based development firm. "It's the only really large tract of land you're going to have to do something like this."

Hubbell announced plans for Gray's Station in January, but it is now releasing new details as the project approaches key votes at City Hall.

The Des Moines Plan and Zoning Commission heard a request from Hubbell earlier this month to rezone the property to allow the project. The commission delayed a vote until July 20, asking city planners for more detail before making a decision.

The City Council is expected to review a development agreement for the project in late July, with a final vote scheduled for Aug. 14.

The agreement would refund a majority of the development's property taxes over 17 years to help Hubbell pay for environmental cleanup at the former industrial site.

If approved, Hubbell plans to close on the purchase of the land from Norfolk Southern in September and would begin construction in spring 2018. Tenants would start moving into the first phase as early as spring 2019.

Tollakson said the $250 million development could take 20 years to build and, depending on how many housing units ultimately are built, could bring 3,000 to 5,000 new residents downtown.

Gray's Station would cover most of the empty land south of Martin Luther King Jr. Parkway. It's the largest empty spot downtown and is a property that city leaders have described as an eyesore.

Around downtown Des Moines, the 75-acre development would be unparalleled in size. West Gateway Park, by comparison, covers 13 acres.

"It's a huge project," said Rita Conner, an economic development coordinator for the city. "If you look at the 30,000-foot view and look at all the elements, it's a small town, really."

Tollakson and other officials from Hubbell gave The Des Moines Register (http://dmreg.co/2tBrJ05 ) a tour of the site earlier this month to lay out their vision for Gray's Station.

They described a dense neighborhood that would prioritize pedestrians and cyclists over cars. In the middle of the development, blocks would be lined with townhouses and tightly packed single-family homes. Instead of individual yards, houses would open to shared park space.

Six- to eight-story buildings with some mix of apartments, condos, or co-ops would border the neighborhood.

Commercial developments with retailers or office space would anchor opposite ends of the development.

The pedestrian bridge has been on the city's drawing board for years and included in the 2019 budget.

A network of protected bike lanes and trails would form a grid through the neighborhood. There would be two main parks linked by a series of greenways.

The design aims to mesh natural areas with dense, walkable housing, said Justin Platts, a principal with Des Moines-based RGD Planning and Design, which developed the concept for Gray's Station over the past year.

"In one of our focus groups, someone told us, 'When you walk out your front door, you should feel like you are in a park,'" he said. "That's very difficult to do in an urban environment, but I think we accomplished it."

Officials at Hubbell and RDG looked at similar developments around the country, drawing inspiration from neighborhoods that preach walkability and conservation, such as Stapleton in Denver and Mueller in Austin, Texas.

Both developments turned former airport land into communities that mix densely packed homes with main street-style commercial districts to create pedestrian-friendly neighborhoods that command premium home prices.

The design of Gray's Station is the result of asking how a Des Moines neighborhood can compete with those in cities such as Denver, Colorado, Austin, Texas, Portland, Oregon, and Minneapolis, Minnesota said Kris Saddoris, Hubbell's vice president of development.

"We've come a long way downtown and we've done beautiful things, but what's the next step?" she said. "Not only for the people who are here but also for the people we are trying to attract: What are they looking for? What are they doing today in Denver and Portland that we can do in Des Moines?"

Gray's Station wouldn't be the first neighborhood in central Iowa to promise walkability, shared green space and main street commercial districts. Similar principles have been implemented at suburban developments including Ankeny's Prairie Trail and The Village at Ponderosa in West Des Moines.

While Hubbell has been a major player in downtown's recent housing boom, the company has decades of experience building sprawling suburban subdivisions.

But officials at Hubbell said Gray's Station will be distinctly not suburban.

"It's a high-density urban development with lots of green space, with biking and people preferred over cars," said Cornelison said.

What makes Gray's Station stand out from other developments is the diverse mix of housing, Hubbell officials said. Plans call for both rental and for-sale properties, including detached single-family homes, townhouses, apartments, condos and possibly co-ops or senior housing.

The goal, Saddoris said, is to offer a mix of housing that attracts a variety of different age groups, from young professionals to families with children to retirees.

But the designs and the exact mix of housing could change with buyer preferences and market conditions. Such flexibility is critical to Gray's Station's long-term success, Tollakson said.

"We know within a 20-year period there are going to be two to three times when the market is going to dip down into some type of recessionary trend," he said. "We have to have the flexibility to respond. We're going to be tied to this thing for a very, very long time."

In conjunction with Hubbell's project, the city plans to overhaul three flood basins on the north bank of the Raccoon River. Initial plans call for turning the basins into a string of wetlands and ponds that help filter sediment and pollutants before the water flows into the river.

Hubbell wants the flood basins to function like park space, with areas for bird watching and docks for fishing. Saddoris dreams of elementary school students taking field trips to the site to learn about water quality and wildlife.

Tollakson, a leading proponent of a plan to promote recreation on local rivers, wants the new pedestrian bridge to include a place to launch kayaks and canoes.

The flood basin overhaul is expected to cost up to $2.3 million, much of which the city hopes to fund with state environmental grants, Conner said.

Like much of downtown, the land where Gray's Station is planned was once owned by F.M. Hubbell, the real estate and business mogul who founded Hubbell Realty Co. 160 years ago.

For years, it served as an industrial area and rail yard.

Today, it's overgrown with saplings and brush. Trees rise through abandoned rail tracks. Thousands of old rail ties are buried.

Cleaning up the debris and environmental issues is expected to cost $6.5 million.

Hubbell has experience with such cleanup. It's currently building a 300-plus-unit apartment complex called CityVille on 9th on an adjacent property that Tollakson said had similar environmental problems.

Hubbell isn't the first developer to dream of overhauling the Norfolk Southern property.

About a decade ago, Minneapolis-based Sherman Associates laid out plans for developing offices and other commercial properties, but the project fell victim to the recession.

About two years ago, Orton Homes negotiated a contract to purchase the land but walked away before closing the deal. The site's complicated environmental problems would have been challenging for the Clive-based homebuilder, Conner said.

"They had some good ideas, but this is not a property that just anyone can come in and undertake," she said.

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Information from: The Des Moines Register, http://www.desmoinesregister.com