A Des Moines apartment development is being used as a demonstration project for an effort by the city and the state of Iowa to promote green infrastructure.

Sherman Associates Inc. could hold a clinic on how to clean and slow stormwater runoff once its Edge at Gray’s Landing project is completed about this time next year.

The Edge at Gray’s Landing is a $15.25 million, four-story, 90-unit apartment project that is part of the River Point West development that stretches roughly from Southwest Ninth to Southwest 16th streets south of Martin Luther King Jr. Parkway.

It is one of three Greater Des Moines projects that have been approved for federal Community Development Block Grants that carry bonus funds to defray the costs of installing a range of features that reduce and filter stormwater before it reaches municipal systems.

Green infrastructure is gaining increased attention from state and local officials who encourage developers to incorporate it in their projects.

When the Iowa Economic Development Authority approved $52 million in requests for the federal disaster recovery funds earlier this year, it tacked on an additional $1 million for six projects across the state, including $750,000 for The Edge at Gray’s Landing and $75,000 for Windsor Crossing Senior Apartments in Windsor Heights.

The federal funds come from a pool of $890 million that has flowed into the state for new developments and renovations in counties affected by the floods of the 2008.

The state has approved 15 projects that will attempt on-the-spot management of stormwater with a target of treating 1¼ inches of rain over 24 hours.

“Managing rainwater where it falls can alleviate flooding and provide a chance for stormwater to be cleansed and cooled before entering our streams and lakes,” IEDA spokeswoman Tina Hoffman said in an email. “We also believe green infrastructure practices can add durability, resiliency and beauty to the landscape while reducing future long-term infrastructure costs.”

The federal funds come from a pool of $156 million that was made available to the state for new developments and renovations in counties affected by the floods of 2008.

One of the conditions for the U.S. Department of Housing and Urban Development disaster recovery funds received by the state is to invest a portion in practices that will mitigate future hazards, including strategies to reduce and prevent flooding, Hoffman said.

IEDA’s funding recipients are receiving technical assistance through these two partnerships with the Iowa Department of Agriculture and Land Stewardship’s Urban Conservationist Program and the Des Moines office of BNIM architects.

Tim West with Snyder & Associates Inc. said the Sherman project should stand as an example of stormwater management in an urban setting, especially given the number of features that will be included, everything from a living wall to a storage tank that will hold rainwater that in turn can irrigate community gardens.

The rainwater storage tank originally was intended to be located underground. However, with its potential to serve as a focal point for the various stormwater best management practices at The Edge, a decision was made to locate it above ground.

“That’s part of the outreach part of this project,” West said.

It also was an element that drew some criticism when the project was presented to the city’s Urban Design Review Board, with some members of the board saying that it was an unattractive educational tool.

That sentiment didn’t bedevil landscape architect Dennis Reynolds, who is a member of the board.

“I think it should be celebrated,” he said during the meeting.

West said various elements of The Edge stormwater system will be used in other Sherman developments at River Point West.

Stormwater management plans for Windsor Crossing Senior Apartments have not been finalized but could include permeable paving, a green roof and rain gardens, according to a city staff report.

Features of Sherman’s urban stormwater management project:

Permeable pavements: 
Permeable pavements are proposed in the exterior parking lot, drive aisles, plazas and at the transit stop. Permeable pavements allow for the infiltration of stormwater over a large area, slowing down the runoff as well as providing a filtering effect to larger contaminant particles. 

Rainwater harvest, storage and reuse: 
A 7,000-gallon aboveground storage tank is proposed to hold rainwater collected from the roof. The rainwater would be used to water community gardens and to serve a drip irrigation system. West said the development could have 
two storage tanks.

Bioretention: 
Three large bioretention areas are proposed on the site. Drive aisle widths have been adjusted to accommodate for larger bioretention areas on the west side of the site. Bioretention areas capture petroleum products, trash, pesticides and silt within a basin area and allow them be filtered and absorbed in layers of various soil types while rainwater seeps into a storm sewer that continues on to a local stream or drainage way. 

Soil quality restoration:
1,250 cubic yards of soil will be improved by amending sand, compost and in some areas aggregate layers to increase soil permeability. This can successfully increase the soil’s quality without requiring mass excavation of existing soil.

Native plantings: 
Grasses, flowers and shrubs help absorb some pollutants and reduce the amount of stormwater that flows out of the site.

Underground filtration chambers: 
This series of pipes and tubes reduces water flowing to Des Moines’ stormwater system and also filters out pollutants. It had been planned as the sole means of meeting city requirements. Under the current plan for the Edge, it is an additional feature that will act as a last resort when runoff exceeds capacities of the other other stormwater management features.

Living walls: 
This system consists of a series of planters attached to the exterior walls. They can absorb rainwater and reduce heat.