The New Look of Storm Water Management

By Peter Blundell, president of Ultrablock Inc.

Pictured is the remodeled Amtrack Train Station in Oregon City, Oregon that implemented a comprehensive storm water management plan. John Burrell, project manager/erosion control officer for the city, decided to use the Xeripave??????oe pavers as part of the plan. Photos courtesy of Ultrablock Inc.

Xeriscape has been defined as: ''A landscaping method developed especially for arid and semiarid climates that utilizes water-conserving techniques.''

Xeripave??????oe pervious paver is a water-conserving paver that is used to allow rain water (storm water) to infiltrate through the surface into the soil below.

It is common knowledge that wet aggregate tends to look better then dry aggregate. Therefore using a clear polymer gave the rock the wet look while binding it together. The pavers are 2-inch thick, 12x12-inches or 16x16-inches in size and come in five standard colors. Custom colors and shapes are available as well.

The pavers fall into the same classification as pervious concrete or pervious asphalt. However upon first seeing a paver, most people think of it as a Rice Krispy Treat except you wouldn't want to bite into one.

They are made with natural aggregates bonded together with a clear high-strength polymer. The end result is a paver that looks like it was made with polished stone that is highly pervious. The paver matrix is so pervious that it has a flow through rate of over one gallon/second/square foot or over 3,600 gallons per hour per square foot.

The partial coverage utilizing the company's 16x16-inch Northwest pavers intermixed with standard concrete paver bricks. This shows the benefits of the 12 to 18-percent coverage. Pavers were installed by Thompson Construction Company for Terrebonne Parish Consolidated Government at the new North Houma Library in Gray, Louisiana.

These pervious pavers were developed by Xeripave LLC out of Vancouver, Washington. The managing partners realized a need for a highly pervious paver after reviewing the attributes of pervious concrete/asphalt along with other products that had certain functional as well as aesthetic limitations.

One of the first applications for the pavers was a courtyard at the Adventist Hospital in Portland, Oregon. The owner and architect wanted to utilize company colors in the design of the courtyard. Red and light gray pavers were used in a design that was both aesthetic and functional. The pavers performed so well that one of the contractors commented how dry the courtyard was during a major rain event when the surrounding streets and grounds were flooded. Another application well suited for the pavers is tree surrounds.

The cost savings of using Xeripave??????oe pavers as a tree surround could be 50 percent or greater compared to a metal grate. The pavers are already a preapproved product for tree surrounds in Portland, Oregon, as seen at Adventist Hospital.

Traditionally, tree surrounds would be a metal grate fitted in a sidewalk opening. The new focus is to use the pavers to form the tree surround as well as being part of the surrounding sidewalk. This approach allows the tree roots access to more air, water and nutrients, reducing the surface travel of roots and potential buckling of the surrounding area.

The Amtrack Train Station plan called for using these new pavers as tree surrounds, to promote deep root watering, and aeration for the trees due to the high pervious nature of the pavers. The pavers extend the tree surrounds into a bench seating area. Gray pavers were used to help blend in with the natural landscape and give the added slip resistant/ADA surface required. The final outcome of the job gave everybody the wow factor along with getting the desired end results.

The pervious pavers can be used for a variety of applications. As Rick Ianello, a managing partner with the company said, ''We have not even begun to realize all the applications for these pavers. When you first show it to people, their minds start to work and before you know it, a new application has been created!''

The applications of pervious pavers include strip drains as shown here at Thatcher School in Ojai, California. The sidewalk was poured with a French drain along the edge, and 12x12-inch Montana pavers were installed as the cover to the drain.

Tim Faulkner, Public Works Director for Rancho Cucamonga, California, liked the fact that the pavers would keep the area from getting muddy but were easy to clean and maintain. The city is already constructing a second dog park utilizing the pavers. Interestingly, the pavers have also been used with great success for indoor kennels.

The pavers can be used in partial to full-surface coverage. Company technical salesperson Ron Putz said that in many cases 12 to 18 percent of the paved surface only needs to be pervious when using these pavers because of the high porosity. With a proper subsurface utilizing the right type of aggregates and compaction, a reservoir can be built to collect the surface water runoff through the pavers.

One of the unanticipated applications for the pavers is in dog parks. Rancho Cucamonga, California, used the pavers in the watering area of a dog park they constructed over a year ago.

Then depending on the native soil, the water could be perked back into the ground or piped off into another area. The benefits of the 12 to 18 percent coverage are that there is less pervious area to maintain, pavers that are easy to clean and lower costs, initially and long-term.

When asked about vehicle traffic on the pavers, Putz pointed out that light vehicle traffic is acceptable but the subsurface preparation is key for good support of the pavers. He said that in-house tire abrasion tests were performed that showed these pavers, utilizing a rounded rock, resisted abrasional forces and stood up without issue in the tests. Pavers can also be made up to 4-inches thick for heavier traffic areas.

Another benefit of using pervious pavers is that the gross contaminants (garbage, leaves etc) are prevented from getting down into the recessed area of the drain and eventually plugging it up. The contaminants are kept on the surface and the pavers are easy to clean (vacuum or pressure wash).