One Drop At A Time

Challenge

The primary challenge was to design and implement this project on a small budget with limited labor resources. In addition, the use of native plants, rain gardens, green roof, bioswales, and rain barrels would create a very different overall site appearance from the traditional suburban neighborhood aesthetic. The design had to find a balance between implementing green infrastructure and appeasing conventional expectations of how a residential yard should look.

Solution

The landscape architect developed a phasing strategy in order to spread project costs over a four-year period to coincide with each new addition to the stormwater treatment train. A close working partnership between the landscape architect and property owner also ensured maximum reuse of existing materials, limiting new purchases and reducing labor costs. A $7,500 grant from the DuPage Community Foundation was vital in covering the cost of installation of the green roof.

To ensure local acceptance of the project, the design strives to manage stormwater onsite while appearing as “normal” as possible. This was achieved by balancing carefully planned hardscape elements adjacent to patches of native vegetation. Some small patches of turf were retained for children’s play and parties and for use by future tenants. Moreover, the educational component of the project – including the website, signage, and tours – increased neighborhood understanding of the site’s stormwater management approach and perhaps influenced the local perception of the aesthetics.

• The on-site rainwater and stormwater management feature include a 250 sf green roof, 6 rain barrels, an underground cistern, 1162 sf of porous pavement, 258 sf of gravel grass, a 2,000 sf of rain garden and a 393 sf bioswale.
• 2,000 sf of rain gardens collect and store runoff, while also creating valuable habitat with native grasses and sedges. In the front yard, the maximum rain garden depth is 12 inches, while in the back yard the maximum depth is 15 inches. These varied depths are not particularly visible due to the prolific plantings.
• A 1,200-gallon, underground cistern collects runoff from the north roof and stores it for use in irrigating the vegetable garden. The Victorian house included the cistern, but it had been out of use for several decades. It was brought back online after clean-up and repair.
• A 393-sf bioswale flanks the north side of the property and is designed to infiltrate overflow from the cistern. Because of its location in the shade, the bioswale is planted with native woodland and savanna species.
• The 6 rain barrels on the site were salvaged or reused. Each has the capacity to hold 55 gallons of roof runoff, which can be stored and used for irrigation. On the south side of the property, three rain barrels are tied together to store water from the roof.
• 162 sf of permeable pavement replaced impervious concrete pavement. This concrete pavement was demolished and broken into 2-3-inch pieces, to create a gravel base. For the new permeable pavement, salvaged brick pavers were surrounded by stone chips and more pieces of recycled concrete. Layers below the surface include stone chips, porous aggregate, and recycled concrete.
• A conventional, compacted gravel parking stall in the backyard was replaced with a 258-sf patch of gravel grass to create a functional spare parking stall that infiltrates the precipitation it receives along with overflow from the rain garden. Any excess water flows into the alley behind the property.
• Nearly 30 species of native prairie grasses, sedges, and forbs are in the rain gardens, bioswale, and gravel grass. Species planted include asters, bottlebrush grass, columbine, black-eyed susan, coneflowers, foxglove, golden alexander, little bluestem grass, switch grass, wild quinine, copper-shouldered oval sedge, and long-bracted spiderwort. The addition of these plants led to a noticeable increase in insects, butterflies, and birds on the site.
• The 250-sf green roof, which sits over the Victorian home’s front porch, comprises 3 inches of growing medium and 1 inch of drainage aggregrate, or gravel. The roof is estimated to weigh about 25 pounds per sf when saturated and is estimated to capture 50-75% of the rain falling on it. Green roof plantings on the roof include sedums, blue gamma grass and Mexican hat flowers.

• The design team saved nearly $5,400 by using salvaged materials and reusing materials found on-site. These savings included $997 from reusing 125 cubic feet of old concrete path materials as subbase and urbanite, $1,167 from reusing soil from the property for the rain gardens and bioswales, $640 from turning salvaged soap barrels into rain barrels, $699 from reusing the existing cistern after repair, and $1,896 from using salvaged Holland stone pavers to create permeable pavement.

• An annual spring burn, as well as weeding of the prairie grass, is imperative for enforcing the “controlled” appearance of the landscape. Simply trimming the vegetation leads to a messy and unkempt appearance. In order to burn the landscape in this setting, the landscape architect applied for a natural area management permit from the Illinois Environmental Protection Agency. This was then approved by the local fire department, which in turn issues a burn permit.
• Neighbors to the site took a “wait and see” approach regarding the installation of the green features like the green roof and bioswale. After witnessing the success of these features, local residents became more interested in adopting similar features on their own properties.
• Existing stormwater modeling programs were found to be overly conservative in estimating surface runoff at this building scale, thus causing over-engineering of the treatment train. During a rain event exceeding 50-year storm levels, the rear rain garden filled to only 1/3 of its capacity at the storm’s peak.

Project Team

Landscape Architect: de la fleur LLC
Civil Engineer: Conservation Design Forum/Conservation Research Institute
Landscape Maintenance Contractor: Conservation Land Stewardship

Role of the Landscape Architect

A resident of 168 Elm Avenue, the landscape architect worked closely with the property owner to design and construct this landscape demonstration project. The landscape architect was the lead designer and planner, working pro-bono to develop the site design through a series of phases that spanned several years of construction. After project completion, the landscape architect widely promoted the project, launching a project website and providing tours for local professionals, residents, and community groups.