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Permeable Pavers and Rainwater Harvesting

Pavers & Slabs

There’s an emerging environmental consciousness across society that’s becoming ever more mainstream, and it’s expressed with the most clarity by the way consumers wield their wallets. It’s as much about how purchases fit into an eco-friendly lifestyle as it is about the products and services themselves. And we’re talking about far more than solar panels and electric cars. Conservation-focused consumers are looking for eco-friendly designs in all product categories, and a purchase decision may well hinge on just how “green” a particular product is perceived to be.

What does that have to do with interlocking pavers? Potentially, quite a bit. Permeable interlocking concrete pavers (PICPs) can play a significant role in water-wise conservation and rainwater harvesting – two hot-button topics at the core of the environmental conversation.

Permeable pavers can be used both in passive rainwater retention and in “catchment” areas as part of more ambitious, active water recovery systems. In the simplest case, their role is to drain runoff and pooled surface water back into the local ecosystem, a quality that also has the potential to control flooding and prevent surface ice formation. In more elaborate designs, PICPs can compose ‘catchment’ areas in the form of driveways, patios, or walkways that capture and channel rainwater directly into purpose-built storage for later use – a defining characteristic of a more sophisticated harvesting and reuse system.

The most well-known rainwater catchment structure is, of course, a roof. Rain sheets off the roof into gutters, perhaps passing through a coarse-grained filter, before being channeled into a rain barrel below. That’s commonplace worldwide, but, as you might imagine, driveways, patios, and walkways are hardly the first things that come to mind when people talk about water harvesting or conservation. That kind of awareness will undoubtedly build over time; until then, as the most abundant resource on the planet becomes increasingly costly to buy from utilities, opportunities multiply for businesses that can offer alternatives to centralized utilities and further educate already eco-aware prospects –ultimately monetizing and profiting from the blossoming eco-revolution.

The bottom line? Eco-friendly products, practices, and lifestyles are as on-trend as it gets.

What’s a Permeable Paver?

The defining property of permeable pavers is drainage – rapid drainage. Not through, but around the pavers, at the joints. Water that flows down a surface built of traditional pavers is often just diverted into the street, into sewers, or off property. Either way, its value is lost to the local ecosystem, and it becomes yet another contributor to more contaminated runoff downstream. Permeable pavers, on the other hand, help retain water in the property’s local ecosystem, and prevent runoff right at the source.

PICPs are utilitarian in a very “green” way, yet there’s no aesthetic penalty for choosing them – they’re available in a wide variety of styles, textures, and colors, and they look very similar to traditional ICPs.

Unilock Permeable Products

The trick to PICPs is the additional spacing between pavers, which is typically filled with small, open-graded stone, and the shape of the paver itself strategically designed to facilitate drainage beneath. Rain and surface water seeps through the gaps, while the stone filler acts as an initial filtering stage for whatever happens downstream. Whether the water subsequently just soaks into the soil or gets channeled into storage, the drainage helps prevent local flooding, control stormwater, and, incidentally, mitigate ice formation on the paver surface, since standing water drains before it gets a chance to freeze.

A Primer on Rainwater Harvesting and Reuse

So, what does happen downstream of the PICP catchment area? The options are practically endless. The design of a rainwater recovery system is driven by the needs, budget, and goals of the property owner, but constrained by both statutory limitations and the characteristics of the available soil and terrain.

At its most basic, the function often referred to as rainwater harvesting amounts more precisely to stormwater management – trapping water to prevent runoff, but with no active system or strategy for reuse.

Options quickly get more sophisticated from there.

While it’s true that property owners can reap benefits from permeable systems without elaborate storage, piping, or active distribution systems, it’s worth noting that there is nevertheless a market for exactly that: extensive recovery systems capable of both storage and reuse. It seems that some homeowners feel compelled to take a more serious approach to water reuse, and the motivating factors are only getting stronger.

Between 2008 and 2016, water rates charged by various utilities across the U.S. increased at staggering annual rates – as much as 15%, according to the U.S. Department of Energy. The city of Seattle, hardly the driest region in North America, saw average municipal water rates increase 9% every year during that period.

The incentives are building for homeowners to adopt increasingly capable and sophisticated systems for water conservation, often with a DIY approach. Captured rainwater can be stored in subterranean tanks, or “cells,” then redistributed as needed with either passive, gravity-driven drainage, or with active pumping to the point of reuse.

Rainwater harvesting can also be part of an integrated conservation strategy by augmenting existing gray water recovery systems that capture drainage from laundry drains and kitchen sinks. Gray water isn’t potable, but it’s perfectly suited to irrigation of non-edible garden plants, and, in many instances, it’s arguably better for the garden than the municipal water supply (credit the nitrates from detergents and other household products). Other uses include vehicle washing, filling header tanks for toilet flushing, and, ironically, hosing down the permeable driveway or patio.

Identifying Opportunity and Overcoming the “It’s Just Too Dry Here” Objection
The most effective rainwater collection requires, as you might surmise, rain. Therefore, it might seem like common sense that rainwater recovery is only viable in regions with the greatest precipitation. Surprisingly, though, the vanguard of rainwater harvesting is being led by some of the most arid regions in the country – think California, Arizona, and New Mexico. These states, even in heavily urbanized areas, are, by definition, deserts. Moreover, climate scientists see overall rainfall actually decreasing in these regions in the coming decades.

So, how can they justify, and how could they possibly benefit from, a rainwater harvesting project?

Homeowners in climate zones with infrequent yet heavy rain, who are also experiencing increasing charges and tiered-rate systems from water utilities, can often benefit from appropriately-sized catchment and storage facilities. In several recent instances, municipalities have announced head-turning rate increases that may change the equation sufficiently to merit reassessment of personal conservation practices.

The Role of the Hardscape Contractor

Luckily, regardless of the complexity of the overall recovery system, permeable pavers are at the front end of the water flow – the catchment end of things. What happens downstream from there doesn’t redefine a successful installation for your team. That said, there are some requirements for site preparation, bedding, and installation that must be observed to ensure success.

Manufacturers like Unilock work closely with contractors to provide education and installation guidelines. It’s not that seasoned hardscape contractors don’t already have the core expertise required, it’s just that doing it right makes a little education worthwhile.

Then there are the rules and regulations. Legislation is still catching up with the practicalities of private water harvesting systems. Up until 2016, it was illegal to capture rainwater at all in Colorado. The rationale for that was based on some pretty archaic principles (land and water rights), but it hints at the possible legacy statutes that may lurk on the books in other states, cities, and counties across the country.

What’s It All Mean?

Millennials, like no generation before them, treat conservation as a central priority in their lives. As they spill into the workforce, become homeowners, and build their spending power, eco-friendly products will go from environmentally savvy luxuries to core requirements.

Consumers in general are looking for ways to conserve, to edge away and establish enduring independence from centralized utilities. They’re looking for opportunities to express their environmental consciousness, and vendors, in any field, who can address that desire in a meaningful way will be best positioned to win their business.

But without some education during the sales process, even a prospect with his and hers Prius’ in the driveway and a passion for water conservation may not make the strategic connection between a new driveway or patio and the opportunity to add substantial conservation capacity to their ecological strategy.

Permeable pavers have the potential to capture not only rainwater, but for savvy contractors willing to invest in a little learning, they might also help capture a lucrative new market in the process.

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