The Advance of Permeable Surfaces
According to the World Resources Institute, the flood damage in urban areas of Canada, encompassing residential properties, commercial establishments, and public infrastructure, amounted to around $3 billion in 2010. However, if no measures are taken to tackle this issue, the think tank predicts that these expenses could surge to more than $8 billion by 2030.
If you were to ask a planner, an environmentalist, or someone working in a municipal road, water, or sewer department, they would all agree that hard, impermeable surfaces, especially roads and driveways, play a significant role in urban flooding. Craig Reid, senior advisor for the Association of Municipalities Ontario, emphasizes that while AMO members are pro-development and interested in affordable housing, they are also focused on managing externalities, such as flooding and runoff.
Reid explains that due to years of urban growth, many municipalities now face the challenge of dealing with water runoff from a high concentration of roads, roofs, driveways, and hardscapes, which carry water much faster than natural surfaces. As a result, cities like Burlington, Toronto, and Peterborough are experiencing intense storms that overwhelm local stormwater management systems, leading to water backing up into people’s homes.
However, instead of solely blaming residential homeowners or builders for the problem, some city officials are now actively involving these groups in finding solutions. The City of Kitchener, for example, recognizes its dependence on groundwater and is encouraging developers and home builders to maintain the natural hydrological cycle as much as possible. Nick Gollan, manager of planning and programs for Kitchener’s sanitary and stormwater utilities, explains that the city offers up to a 45% reduction in the stormwater portion of a monthly utility bill as an incentive for homefront improvements like rain barrels, rain gardens, or permeable paving. These improvements can be implemented in existing homes or new residential projects.
According to RAIN, an organization that collaborates with municipalities and homeowners to minimize runoff and effectively handle rainfall, the stormwater credit program has achieved remarkable success by redirecting over 500,000 m3 of rainwater annually from Kitchener’s sewer system.
In spite of this achievement, Gollan approximates that the city continues to bear an annual expense of $15 million due to costs linked to water runoff. He emphasizes that repairing the harm caused to water courses and nearby infrastructure can easily amount to $3 million to $5 million per location.
Besides the encouragement to minimize water runoff, home builders are well acquainted with the prevalence of restrictions on hard-surface usage in new residential communities, particularly in environmentally sensitive areas.
To prevent such a scenario and avoid a significant decrease in his profit margin, Pomeranc sought the assistance of two providers specializing in permeable paving solutions. The first provider, PurePave Technologies based in Ottawa, offers a highly porous surface that can absorb an impressive 14,000 liters per cubic meter per hour. This surface is made up of natural aggregate combined with a polymer bonding agent and permeable base system. The second company, LID Paving based in Toronto, distributes the Ecoraster permeable paving system, which utilizes plastic grids filled with gravel or grass.
For the Perth site, Ecoraster was utilized for the residential driving lanes, while PurePave was chosen for the walkway and vehicle parking pads. Looking back, Pomeranc states that selecting these solutions was an obvious choice for the project. Not only did it contribute to profitability, but it also enhanced the company’s reputation. As a luxury rental home builder, Pomeranc emphasizes that his company invests a substantial amount of money into landscaping for each project, and the addition of PurePave surfacing further enhances the overall image due to its stone aggregate finish.
“It’s also satisfying to be able to highlight that we have implemented a low-impact development approach, where stormwater runoff is effectively managed as part of our green infrastructure.”
Addagrip, a UK company that introduced its aggregate, resin-bound surfaces in the 1980s, is recognized as one of the pioneers in this field. While the product offers environmental benefits in terms of porosity and water control, managing director Roger Critchley acknowledges that Addagrip’s primary motivation in the early days was to create an attractive surface that could be installed more efficiently in parks and schools.
Addagrip’s product has gained popularity among various professionals in the UK, ranging from builders to landscape architects. Initially, it was primarily utilized for high-end homes, but it is now increasingly being employed in mid-range residences as well. According to Critchley, the surface is often chosen for its visual appeal, as the driveway is the first element that catches the eye.
This aspect has proven to be a significant selling point. The company’s success has led to widespread adoption, with installers present in every major town across the UK. Critchley attributes this achievement to economies of scale and the rapid acceptance of the product, which have contributed to a reduction in its cost over time.
Builders and developers often find the initial cost to be a significant drawback. While the average expense of paving a 400 sq. ft. new home driveway with asphalt is approximately $1,800, PurePave comes at a higher price of around $10,500 (although the company does offer volume discounts beyond 1,000 square feet).
Nevertheless, there are other important factors to take into account. PurePave surfaces have the advantage of resisting ice build-up and melting snow 50% faster. In contrast, concrete and asphalt driveways require regular touch-ups and are more susceptible to buckling caused by freeze/thaw cycles. Additionally, asphalt has a notably shorter lifespan. On the other hand, interlocking brick driveways take longer to install and may experience heaving over time if not properly installed.
Permeable surfaces, such as the one developed by PurePave Technologies, require regular maintenance to ensure their effectiveness. It is recommended to perform an annual pressure wash at the bottom end of a driveway where cars enter to prevent any clogging of the surface openings. Although some clogging may occur, it does not significantly impact the surface’s ability to absorb and retain water.
While Addagrip, a similar product, has gained popularity in the UK and parts of the southern U.S., it has not been introduced in Canada due to its inability to withstand the harsh freeze and thaw cycles common in this country.
PurePave Technologies CEO Taylor Davis recognized the success of Addagrip and the need for a surface that could withstand Canada’s weather conditions. To address this, Davis collaborated with top construction materials chemists in Canada to develop a polymer/aggregate surface that is highly porous and specifically designed to endure the climate.
To validate the durability of PurePave, the University of Ottawa conducted rigorous freeze-thaw tests. The tests involved filling several PurePave samples with water and subjecting them to extreme temperatures of -40°C in a freezer for an hour, followed by a transfer to a room with a temperature of 30°C for an hour. The results showed that the surfaces maintained a flexural strength of 6.1 MPa (62.2 kg/cm²), which is six times stronger than asphalt at room temperature. This testing method was a first for the university, as no degradation in flexural strength was observed.
Impressed by these performance numbers, Flato Developments Inc., a builder based in Markham, considered using PurePave for its Palgrave Estates community in Caledon. Similar to other projects, Flato must comply with municipal water runoff restrictions, making the use of permeable pavers a requirement.
Senior project manager Dan Lacroix of Flato Developments Inc. stated that they have been in discussions regarding the use of PurePave for their project in Caledon. This aligns with the urban guidelines set by the town for estate developments, emphasizing the importance of using this type of surface.
Lacroix highlights PurePave’s porosity and durability as one of its appealing features. Additionally, he emphasizes the surface’s appearance and its non-slippery nature, even when wet.
While homeowners primarily focus on upgrading kitchens and bathrooms, Lacroix remains optimistic about the potential adoption of permeable paving products.
He acknowledges that mindsets are constantly changing and evolving. Reflecting on his own experience, Lacroix recalls a time when installing nine-foot ceilings seemed unconventional, but now ten-foot ceilings have become the norm. This demonstrates the possibility for innovative and creative solutions in the industry.
Residual Cost Savings
In regards to the Flato development, Davis from PurePave suggests that there is an opportunity to completely transform the entire neighborhood into a net-zero runoff site, all while enhancing its curb appeal. This means that the only runoff that would occur on the street would be from the street surface itself, and not from the properties of homeowners. As a result, this would provide greater protection for the local watershed.
Although some builders may be discouraged by the costs associated with implementing such a solution, there are additional savings that builders can achieve by incorporating permeable paving into their development on a larger scale. This is according to Craig Applegath, a founding partner of Dialog’s Toronto studio, which is a multidisciplinary architecture, engineering, planning, and urban design firm.
“A more porous site could be eligible for a higher-density, potentially more profitable development.”
Applegath emphasizes that one area where development costs can be reduced is parking areas, particularly in multi-unit residential projects. The expense of having a stormwater retention pond on site can be significant. However, Applegath suggests that by using permeable paving for the parking surfaces, more site area can be utilized.
Taking a more innovative approach, Applegath suggests that if permeable paving is used for both the driveways and the roads, the stormwater issue can be effectively managed within the area where the storm occurs. Although permeable paving may come at a higher cost, the benefits of a more porous site could potentially offset this by allowing for higher-density and more profitable development.
Applegath further explains that in order to achieve density, it is not feasible to have large sites with extensive retention ponds. Therefore, careful planning is required to ensure that the entire site is capable of absorbing water.
In line with this mindset, Ellise Gasner, CEO of LID Paving, mentions that the Ecoraster product is commonly used in residential settings to expand driveways when zoning regulations do not permit additional solid surfacing. In these cases, it serves as a driveway extension.
From a broader community perspective, Gasner explains that their product is frequently utilized for access roads in and around stormwater ponds. These ponds often require access roads for service vehicles, and Ecoraster can provide a grass-filled permeable surface that blends in with the surroundings while still supporting heavy vehicles when necessary.
Similarly, PurePave claims that their product is capable of withstanding the weight of a 40,000 lb. loader driving over it.
The Incentive to Change
Some cities are exploring ways to encourage and expedite the transition to more permeable surfaces, taking into account the cost implications. The City of Ottawa has recently introduced a rebate program that offers homeowners up to $5,000 to install a permeable driveway instead of a traditional hard-surface one. Similarly, the City of Kitchener is considering implementing a similar initiative as part of their market incentives for service providers, such as builders, landscape architects, and driveway paving companies. This program would require providers to submit two quotes: one for a regular paved driveway and another for a permeable paved driveway. The aim is to create a fair competition and address the higher cost associated with installing a permeable paver driveway compared to asphalt. The City may cover some or all of the cost difference to realize the environmental benefits of reduced runoff.
Kitchener, like many other cities in the country, is grappling with a historical mindset that originated in the 1800s, where the main focus was to divert unwanted water away from residential areas. This decision-making approach has had lasting effects, and the city is now working towards reversing it. However, there is still a significant journey ahead to fully achieve this goal.