Landscape Architect Articles

Winning on Two Fronts07-05-18 | Department

Winning on Two Fronts
Permeable Pavement Meets Regulations / Ingenuity Meets Demand

David Aquilina, Strategic Storyteller

The typical way to install Porous Pave, a permeable pavement material that consists of 50 percent recycled rubber chips and 50 percent kiln-dried, crushed aggregate, is to mix it on site with a liquid binder in small batches in a portable mortar mixer, pour it inside guides, screed the material to the desired depth, and finish it with standard tools like trowels and bull floats. However at the LOT42 Global Flex Campus in Kitchener, Ontario, 12,400 square feet of the material had to be installed. Jim Roth, the president of the company that distributes the permeable paving material in Canada, devised two screed boxes: one 3' 1/2" wide and one 6' wide, which were pulled by a skid steer. With them, the contractors could mix and install larger batches of the material. The plate compactor is to create vibration, which helps improve surface finish and prevent sticking of the polyurethane binder to the screed and float.

Kris Zehr's story will be familiar to other experienced and successful landscape contractors who install hardscapes. Zehr Interlock & More (Tavistock, Ontario) has been in the business for more than 20 years. As the company name implies, they specialize in interlocking pavers.

"With concrete pavers, I know what I am doing, and I know I do it well," he said. "I have been cautious about using materials I am not familiar with. When Porous Pave Ontario first introduced me to permeable pavement, I just was not sure why I should take it on - and take the risk."

That was four years ago. Today, municipalities in Ontario issue increasingly strict stormwater management regulations. Many impose higher utility fees on properties that exceed allowed amounts of runoff into storm sewers. Developers and builders need methods and materials to retain more stormwater on site. That has increased the demand for permeable pavement.

"Good companies take on challenges and innovations," said Zehr. "To stay successful, you have to keep up with changes in the market. For us, that meant getting into permeable pavement."

Zehr decided to build one patio with Porous Pave XL. He became convinced. "I have now completed 20 permeable pavement projects with the material, XL is a highly porous, pour-in-place paving material that contractors mix on site with a liquid binder.

"With 27 percent void space, the product can infiltrate 5,800 gallons of stormwater per hour per square down into the underlying aggregate base on which you install it," said Jim Roth, president of the Stratford, Ontario, company that distributes the material in Canada. "It can endure freeze-thaw cycles, frost and ground movement without heaving or cracking, an important advantage with our winter weather in Ontario."

According to Zehr, his largest project in 2017 totaled 12,400 square feet at the LOT42 Global Flex Campus (Kitchener, Ont.): a 17-acre performance venue and events complex. To meet the city's stormwater regulations, and thereby decrease long-term municipal utility costs, the project incorporated a 1,000-square-foot French drain as well as the permeable pavement.

"It is not only permeable, its recycled rubber content makes it a green material. The chips of recycled rubber in the pavement we installed came from rubber processed from about 3,500 discarded tires," said Patrick Doyle, managing partner, LOT42. "It also has the strength and durability we needed for our truck dock."

The city of Kitchener has strict stormwater regulations to help decrease long-term municipal utility costs. To meet them, the project incorporated a 1,000-square-foot French drain as well as the permeable pavement.

With permeable pavers, the only permeable area is the space in the joints between them. In contrast, the entire surface of permeable pavement is porous. "To get an equivalent amount of stormwater reduction, an installation of concrete permeable pavers would need to be larger and therefore more costly," said Roth.

"Installing permeable pavement is easier and faster than laying pavers," said Zehr. He explained that it requires less extensive excavation and base preparation. Contractors pour it inside guides they put in place with screed boards, screed the material to the desired depth, and finish it with standard tools like trowels and bull floats. Permeable pavement conforms to any shape, versus the time-consuming work of cutting pavers to shape and fitting the pieces together like a jigsaw puzzle.

The rubber chips come in different colors. The distributor created a custom green-tan color mix, which was alternated with the standard green color.

Contractors usually mix the material in small batches in a portable mortar mixer, dump it into a wheelbarrow, and shovel it out. That works well for smaller projects, such as patio or a set of permeable tree surrounds along a sidewalk (see sidebar), or where access is limited. To more efficiently pave long, wide rows of the material at LOT42, Roth devised a screed box and constructed two versions, 3-1/2-feet-wide and 6-feet-wide. The boxes are pulled by a skid steer. With the screed boxes, Roth and Zehr could mix and install larger batches of the material.

Was the project a success for Zehr Interlock & More? "LOT42 is having us install more in the courtyard area," said Zehr. "It is a high-profile project we are using with (the distributor) to sell other big, commercial projects."