Porous Pave

Permeable

DowntownCommonsBy David Aquilina, Strategic Storyteller PHOTOS: POROUS PAVE

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Above, Left When the Downtown Commons, located in the heart of Minneapolis, Minn., was created, a key goal was to reduce harmful stormwater runoff. The Commons is a 4.2-acre park, and 22,000 square feet of Porous Pave permeable pavement was installed there in July and August 2016. The shredding and processing of discarded tires produces the recycled rubber chips incorporated into Porous Pave. The Com-mons installation includes rubber recovered from approximately 5,000 scrap tires.

Above Right & Below Left A total of 19,000 square feet of Porous Pave XL permeable pavement was installed in seven areas, all of it along 4th Street, which borders the Commons on the north side. In addition, 3,000 square feet of Porous Pave XLS was installed to create 129 permeable tree surrounds. The Commons — comprised of two distinct sections, with the eastern and western blocks on either side of Portland Avenue — is near U.S. Bank Stadium (in the background), the new home of the NFL’s Minne-sota Vikings. The Commons features three different permeable surfacing materi-als: the product’s permeable pavement, loose decomposed granite (in the western block) and permeable pavers (along the south side of the eastern block).

TThe Downtown Commons in Minneapolis, Minn., is a public park adjacent to U.S. Bank Stadium, the new home of the NFL’s Minnesota Vikings. The Commons is located at 425 Portland Avenue South — bounded on the north by 4th Street, on the south by 5th Street, Park Avenue on the east, and the new Edi-tion Apartments building on the west.

Portland Avenue runs down the center and divides the Com-mons into two distinct parts. The more expansive eastern block is next to the stadium. It is used for game day and community events on the “Great Lawn,” a large oval-shaped grassy field. The smaller western block is more intimate and tranquil. It features rolling landscaping and more trees, benches and table

seating. The Commons brings much needed green space to the downtown and improves stormwater management, especially important with the Mississippi River just four blocks away.

“The Commons is the centerpiece of the revitalization and re-development of the Downtown East neighborhood,” said Jacob Frey, Minneapolis City Council member whose Ward 3 includes the Commons. “The reduction in harmful stormwater runoff and water pollution is one of its many environmental benefits for the entire city.”

“As is typical for highly urbanized areas, much of downtown Minneapolis is impervious. The Great Lawn is a prominent ele-ment of the Commons, designed as open space and for deep

DOWNTOWN COMMONS

Paving

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Above, Left & Right The surfacing product is an eco-friendly, highly porous and durable poured-in-place paving material. Blackstone Contractors, LLC (Corcoran, Minn.), the installation contractor, poured the XL (50 percent aggregate and 50 percent fine-cut, 1/8-1/4 inch recycled rubber chips in the tan color) at a depth of two inches atop a 2” aggregate base for the paved permeable areas. The workers applied two inches of XLS directly over the soil of the tree wells. The 100 percent rubber XLS for the tree surrounds features special-size three-quar-ter inch recycled rubber chips in the cypress color to mimic bark mulch. The availability of different sizes and colors of recycled rubber chips makes the material versatile for landscape design. Porous Pave’s different textures and colors add visual contrast. In contrast to permeable pavers that infiltrate stormwater only in the spaces between them, the entire surface of Porous Pave is permeable. It infiltrates stormwater at a tested rate of up to 6,300 gallons per hour per square foot.

A Step-by-Step Guide to the Installation>> 1) Before installing each of the seven sections of permeable pavement, the Blackstone crew measured the base of each tree, drove in metal stakes to define the circumference of the tree wells, and affixed heavy-duty cardboard around the stakes to establish and protect the areas for the tree surrounds.2) They put down a two-inch base of compacted aggregate in the sections to be paved and covered the edges of bordering sidewalks with plastic sheeting.3) Using a pressured hand sprayer, they coated all tools and equipment with vegetable oil and periodically reapplied it.4) The recycled rubber chips and the dry, clean, chipped granite aggregate for the XL come in pre-measured bags. The binder is in five-gallon pails. In a portable mortar mixer, Blackstone mixed the rubber and aggregate chips with the binder in the proportion specified by the manufacturer. Workers wore gloves and were careful to protect adjacent surfaces from the binder, which is very sticky.5) They dumped mixed batches of Porous Pave XL into wheelbarrows, spread the material with concrete come-along rakes, used oil-coated boards to screed it with a back and forth motion to achieve a depth of two inches, using oil-coated, measured wood screed boards for guidance. They finished the corners and edges with trowels, and then smoothed the surface with well-oiled bull floats.6) All tools and equipment were rigorously cleaned with bio-diesel and stiff brushes.7) For the tree surrounds, the Porous Pave XLS all-rubber formulation was mixed with its special binder, shoveled into the wells atop the soil, and the workers finished it with trowels. Blackstone tapered and thinned the material at the tree trunks.

infiltration of stormwater,” said Mary Lydecker, RLA, LEED AP, senior associate, Hargreaves Associates (San Francisco), the landscape architecture firm that led the project. "Extensive native and adapted tree and groundcover plantings as well as various permeable surfacing materials make the Commons very effective at decreasing stormwater runoff."

According to Ryan Potvin, operations manager, Pe-terson Companies (Chisago City, Minn.), the land-scape contractor for the Commons, Porous Pave was selected for its permeability, durability and ease of in-stallation and maintenance.

With the rubber content, the material is safe and suitable for foot traffic and wheelchairs and slip-re-sistant when wet. The rubber also gives the material durability and flexibility to expand and contract, so it withstands high heat and freeze-thaw cycles without cracking, crumbling or heaving. These are important attributes for application in regions with challenging climates like Minnesota — where summer tempera-tures can soar over 100 degrees, and winter tempera-tures fluctuate and plunge to double digits below zero.

“The Downtown Commons is one of our largest projects to date in the Upper Midwest,” said Dave Ouwinga, president, Porous Pave, Inc. “It helped us reach an important environmental milestone. In 2016, we surpassed a total 7.5 million pounds of re-cycled rubber used in manufacturing our permeable paving material.” LC DB

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