Dig a trench of an appropriate depth and width, cover it with a quality geotextile, fill it with correctly layered and sized aggregate, and place paving stones of brick or concrete block on top. This is the basic formula for not only a beautiful surface for pedestrians and vehicles, but also a system that stores, reduces, and improves the quality of stormwater runoff-and may be less expensive in the long run than asphalt.
The possibilities and the variations are endless. The projects highlighted below show the creative ways that three cities have used permeable pavers to achieve their goals.
Intersection of Plum and Walnut Streets, Lancaster, PA
The city of Lancaster, PA, had three problems.
During heavy rains, the combined sewer system used to overwhelm the treatment plant, resulting in raw sewage being released into the Conestoga River. Downtown, the intersection of North Plum and East Walnut streets used to flood. And a merge lane at one corner of the intersection used to be dangerous for vehicles and pedestrians alike.
“We wanted to keep stormwater out of the system and not have to treat it,” says Charlotte Katzenmoyer, the city’s director public of works, “and we wanted to reconstruct the street to make it safer for vehicles and pedestrians.”
Katzenmoyer had a vision for what would come next, and city designers made it possible. Ultimately, the city removed the sidewalk in front of a red brick brewery and pub, as well as the merge lane and the concrete traffic island beside it, and replaced them with rain gardens and a patio built of permeable pavers.
The city chose StormPave permeable pavers from Pine Hall Brick Co. in Winston-Salem, NC.
“We have a local supplier, Penn Stone, who provides a lot of different building materials,” Katzenmoyer says. “He came to the city and offered Pine Hall Brick Co.’s natural brick. It fits in well with typical Lancaster brick, it’s sturdy, and it holds up well. For us it was a natural decision.”
The city won the grand prize for the project in a contest sponsored by the Chesapeake Stormwater Network, a network of nearly 7,000 stormwater professionals primarily within the Chesapeake Bay watershed. The overall goal of the network is to clean up the bay.
The contest, the Best Urban BMP in the Bay Award (aka the BUBBA), recognizes the best urban best management practices that have been installed in the watershed during the past year. The city won in the Ultra-Urban BMP category, for stormwater practices built in infill or redevelopment projects in urban areas with more than 75% impervious cover.
“It was their first year for doing this,” Katzenmoyer says. “It’s an honor to be the first winner. It’s also an honor that our peers saw the benefits of this project.”
Before the project began, approximately 1.4 million gallons of stormwater from the surrounding buildings and parking lots would flood the intersection every year.
Whenever a large thunderstorm with intense rain struck, the storm flow would overwhelm the sewer system. Twenty percent of the total volume of flow would be released to the city’s permitted overflow locations, which lead to the Conestoga River and from there into the Susquehanna River and finally the Chesapeake Bay.
In 2008, in response to a request from EPA, the city began updating its long-term plan for combined sewer overflows. In 2010, it created and began implementing its Green Infrastructure Plan, which includes the installation of permeable pavers and rain gardens to increase stormwater infiltration.
“The stars aligned,” Katzenmoyer says, and the project took place in the spring of 2013. The city used its own funds as well as grants from the Pennsylvania Department of Transportation, the Pennsylvania Department of Community and Economic Development, and the National Fish and Wildlife Foundation.
The contractor, Horst Excavating Co. of Lancaster, removed the sidewalk in front of the brewery, the merge lane, and the concrete traffic island. For the patio, crews generally excavated 18 inches, but because the subgrade slopes away from the building, they excavated only 12 inches where necessary to achieve a level base.
They built curbing for both sides of all the rain gardens, and also between a sidewalk garden and the sidewalk in front of the patio. To slow traffic through the intersection and improve pedestrian safety, the lanes along Plum Street were reduced to 10 feet wide.
All the businesses in the vicinity remained open while the work took place.
“Horst was so great in terms of accommodating all the customers-including the customers of the buildings next to the property-and the motorists and pedestrians passing by,” she says. “They always have these people in mind when they’re working.”
The patio and the gardens in front of the brewery and pub, Lancaster Brewing Co., are charming. The patio is approximately 75 feet long and 25 feet wide. The StormPave pavers are two-and-a-quarter inches by 4 inches by 8 inches in size. The garden in front of the brewery replaced the traffic island.
Five diagonal parking spaces beside the brewery on Walnut Street are made of the same pavers. The subcontractor that installed the pavers, Erosion Control Services of Sinking Spring, PA, used contrasting pavers for the stripes.
Crews placed a geotextile fabric on the soil and filled the area with aggregate. Then they placed the pavers by hand and swept very fine gravel between them. These pavers have one-quarter-inch joints, which meet ADA surface opening requirements.
Tudbinks of Conestoga, PA, installed the rain gardens, or bioretention basins, at each corner of the intersection and planted them with native shrubs, perennials, ornamental grasses, and tree species. The company also installed an underdrain and an overflow pipe in each garden. These are connected to the sewer system in case the gardens are overwhelmed by stormwater.
“Tudbinks does a lot of our plantings,” Katzenmoyer says. “Their work was exceptional in making the area look good.”
The infiltration provided by the pavers and the rain gardens results in less overflow at the treatment plant and less raw sewage going to the river. Any runoff is minimal and usually gets to the treatment plant after the rest of the storm flow has passed through.
“Our green infrastructure plan will save on the back end as well,” she says. “There will be less wear and tear on the treatment plant, less chemical and energy use, and less sludge production.”
There is also a private aspect to the project. Lancaster Brewing Co. worked with the city to install a 700-gallon cistern to collect the rainwater that used to pour from its roof into the intersection during rain events. The brewery will use the runoff to irrigate the produce it grows in raised planting beds. Designed by Austin-Mergold of Philadelphia, the cistern doubles as a public art project.
The only maintenance that Pine Hall Brick Co. recommends is that the pavers be vacuum swept annually. The brewery has taken over the maintenance of the patio.
“It was a great public/private partnership,” Katzenmoyer says.
During the winter, the patio was shoveled by hand. The parking spaces were cleared by equipment with a rubber-tipped blade.
The pavers performed extremely well. Because the runoff from melting snow and ice went directly through to the gravel, there were no problems with frost heave. Salt didn’t affect the pavers, and they required less salt than the impermeable surfaces.
“I believe they will stand up better,” Katzenmoyer says. “It was a great project. The patio area used to be very ugly and uninviting. It has really become a gem in that neighborhood.”
Jefferson Street
The city of Goshen, in the northern part of Indiana, lies between lakes Michigan and Erie on flat, low-lying, sandy soil. During significant rain events, a storm sewer on Jefferson Street in the Downtown Historic District used to back up into nearby basements, including the police department’s.
“The storm sewer emptied into the existing storm sewer trunk line along Fifth Street, which discharges to Rock Run Creek,” explains Mary Cripe, the civil city engineer in the city’s engineering department. “The trunk line is far too undersized to handle storm events. Like most cities in the Northeast, Goshen has a combined sewer system with no designated stormwater drainage system downtown. Stormwater drainage wasn’t looked at back then like it is now.”
In addition, the roadway surface had deteriorated to a state of disrepair.
One solution to the problem was to reconstruct approximately five blocks of storm sewer to completely eliminate the various flooding that occurred during significant storm events.
Instead, Cripe and the others in the engineering department worked on a design using permeable pavers on the block of Jefferson Street between Main and Fifth streets. The pavers would achieve all the city’s goals: eliminate the need for a storm sewer under the street, the basement flooding, and the ponding, as well as upgrade the surface of the street.
In addition, Cripe says, “We liked the brick-paved look, and driving over a brick street gives you a historic feel, which is great in a historic area.”
The city chose the PaveDrain System, manufactured by PaveDrain LLC in Milwaukee, WI, and distributed by D2 Land & Water Resources in Indianapolis.
The city had some concerns about the maintenance of permeable paver surfaces, because the limestone chips or aggregate used between some types of pavers can be removed by the power of the vacuum of the city’s street sweeper, and without the chips, brick pavers can move easily, Cripe says. However, PaveDrain articulating concrete blocks are shaped so they interlock without the use of washed limestone chips between the blocks.
In addition, each PaveDrain block has an arch that creates a gap of air between the block and the aggregate base. During storm events, the gaps become reservoirs that can store up to 1 inch of water per square foot.
“To our knowledge, this is the first installation of the PaveDrain system as a roadway in the state,” Cripe says. “Anytime you’re the first, you tend to have some reservations, for example, about the cost. PaveDrain costs a little bit more, but once you calculate in resurfacing, maintenance, and lifespan, long-term we’re anticipating that it will be a savings.”
The Elkhart County Soil and Water Conservation District presented the city of Goshen with the 2013 Urban Conservationist of the Year award. The award recognized the city’s installation of green infrastructure to reduce the impact of stormwater runoff on local rivers, streams, and lakes, resulting in cleaner water.
The project took place between mid-September and mid-November 2013. It was funded with local monies.
The contractor, HRP Construction of South Bend, removed the street, the curbing, and the sidewalk. Crews removed and replaced the existing water main, sanitary sewer, and storm sewer below the street. During the excavation, “they found a buried treasure”: an underground fuel storage tank leading to an old Masonic Temple on the block, which they pumped out and removed.
Once all the underground infrastructure was installed, HRP crews constructed the concrete curb and gutter. They poured the concrete for the sidewalks, sometimes working at odd hours to give it time to cure before it had to open for foot traffic the next morning.
They placed a geotextile on the subgrade for the pavers and covered the geotextile with an 18- to 24-inch layer of washed limestone aggregate base, which they leveled and compacted.
They installed a total of 17,186 square feet of the PaveDrain system. The installation took one week. Although it rained, the work didn’t have to stop-another advantage of the system.
PaveDrain blocks come in a variety of colors and have a quarter-inch gap between the blocks. Individual blocks can be connected together by polyester cables to form an articulating mat, which allows for the placement of a large mat of blocks at one time. The mats can be preassembled in a variety of configurations. In addition to roads and parking lots, they also can be adapted to small areas where retention ponds aren’t practical.
The mats arrived onsite on a flatbed truck. From there, each mat was hooked to a spreader bar and placed onto the road. The mats connect to each other like a zipper.
“Each mat is measured as it’s laid,” Cripe says, “but the first couple are the trickiest because each one depends on the one before. The first one has to be done perfectly.”
Another challenge is to ensure that there’s just the right amount of tension on the spreader bar. Too much can create a hairline fracture in the center of the pavers. “They had to replace a few blocks, but it’s very easy to do,” she says. “We also requested a few extra blocks in case some need to be replaced later on.”
To finish off the edges where the blocks meet the curb, crews used PaveDrain blocks that are manufactured without an arch so they can be cut off at different angles.
The only maintenance required is that the pavers have to be vacuum-swept regularly.
“We had a really good experience with the contractor and the PaveDrain reps,” Cripe says. “The reps were onsite during the work and they assisted us with design needs and questions we had. HRP Construction did a great job. Gary Newcomb, the project manager, was amazing.”
The winter of 2013-2014 was the worst in more than 100 years in Goshen. There was a record snowfall and the ground froze as deep as 5 feet. The city cleared the snow from the pavers with equipment with a rubber-tipped blade and spread the same sand/salt combination that is used on all city streets. There were no ill effects on the pavers.
In the spring, there was minimal settling of the pavers because of frost heave. Participants in a bicycle race reported no problems with the surface.
There were multiple spring rains, and no basement flooding. In addition, after one especially hard rain, the storm sewer started backing up at a catch basin and overflowing into the street.
“The street was taking it,” Cripe says. “I’m very happy with PaveDrain. We’re getting ready to do another street.”
Downtown Pedestrian Alley, Pueblo, CO
As boom-and-bust cities go, the city of Pueblo, CO, near the confluence of the Arkansas River and Fountain Creek, probably comes out near the top.
“Pueblo is on Colorado’s Front Range, adjacent to the southern Rocky Mountains, and is relatively flat river valley terrain,” says John Batey, executive director of the Pueblo Urban Renewal Authority (PURA). It receives only 12 inches of precipitation annually, but that precipitation can result in flash floods.
The city boomed in the late 1880s when it had the largest single-site steel mill west of Pittsburgh and was a manufacturing, mining, and railroad hub. It struggled when the silver market crashed, and then recovered, until a massive flood in 1921 wiped out Union Avenue, its main commercial district. It boomed again with the price of steel, struggled through the Depression, and boomed again with World War II.
City leaders began to encourage more stable industries to develop, including tourism. In 1959, they established PURA to stimulate the city through urban renewal projects, many of which have increased tourism.
“PURA built the convention center downtown and the city built the Historic Arkansas Riverwalk, both of which act as anchors for our growing regional tourism industry,” says Batey.
When the city decided to tear up the old asphalt in an alleyway in the commercial and historic district, PURA proposed a design from its conceptual plan, which originally called for impermeable pavers with a central drain.
“When we got to the city’s stormwater enterprise, they had some concerns about the water quality that would be created,” he says. “They said it was a 20th century design.”
The contractor for the project, Tony J Beltramo & Sons Inc. of Pueblo, asked Steve Schroeder, the owner of Southside Lawn & Landscaping, also in Pueblo, to give a presentation on the features of permeable versus impermeable pavement to the city and PURA. Schroeder pointed out that permeable pavers improve water quality by allowing storm flow to infiltrate into the ground. As a bonus, they cost a little less than impermeable pavers and their associated drainage infrastructure.
Schroeder, a certified Pavestone installer, was given the go-ahead to install permeable concrete pavers from Pavestone Co., which has 20 regional manufacturing locations in more than 40 states.
Pavestone pavers come in a variety of hues and textures, including one with a series of bumps on the surface to provide visual and textural contrast for people with physical or sensory disabilities. Their pavers are designed to withstand freeze-thaw conditions.
Phase 1 of PURA’s conceptual plan involves a three-block stretch of an alleyway that connects the riverwalk channel with B Street, the location of Union Depot, the city’s refurbished historic railroad station.
“We thought it was important to tie in Union Depot with the riverwalk,” Batey says. “Union Avenue and downtown are coming back to life. A lot of restaurants along Union Avenue back onto the alley and have alleyway patios. Until recently, they opened onto a visual mess.”
Phase 2 of the plan is being contemplated by PURA staff and would involve another 3-block stretch of alleyway also extending from the riverwalk.
For this project, PURA chose Pavestone’s Antique Terra Cotta permeable pavers. The pavers are rated for heavy commercial truck weight, which was necessary because the alleyway is still used by utility, garbage, and delivery trucks.
The project began early May 2014 and finished mid-June. The cost was split between PURA and the city’s Wastewater Enterprise.
Beltramo first removed the asphalt, a storm drain, and the stormwater sewer line. “It was the original sewer line from 1911,” Batey says. “An old clay pipe. They had to dig 10 to 12 feet deep to expose it.”
Crews placed TerraTex geotextile from Hanes Geo Components in Winston-Salem, NC, over the excavated trench, then a layer of fine gravel over the geotextile and a perforated pipe on the gravel bed to ensure that the below-grade collection of stormwater occurs efficiently. Then they replaced the fill to about 8 inches below grade and compacted the bed again before putting the pavers into position.
“The perforated pipe is the key to the whole permeable paver installation,” Batey says. “Stormwater infiltrates through the bricks to the compacted subgrade fill. The fill acts as a natural filter for oils, chemicals, and other pollutants before they reach the pipe, and then the stormwater drains to a series of detention lakes and ponds associated with the Arkansas River.”
There were a couple of challenges, he says. Soon after the project began, a downtown festival put the work on hold. In addition, “When there is a roadway surface as old as this, there are real-world elevations to deal with. Some of the manholes were higher than they should have been. Beltramo had to make sure everything was on grade.”
PURA’s design engineer, JR Engineering of Colorado Springs, was onsite when South Side installed the pavers and swept number 9 aggregate between them. “They did an excellent job,” Batey says.
“It was my design,” says Schroeder. “I knew exactly how it was going to go. All the utilities did their jobs great. This was one of the smoothest jobs I’ve worked on.”
The city will maintain the pavers; maintenance consists of sweeping with a vacuum truck on a regular basis.
“The alleyway enhancements will not only make the alleyway patios more inviting, but will also provide business owners with a “˜second front door’ to their establishments,” Batey says. “Everything worked out beautifully. Everything is gorgeous. I’m looking forward to doing the next two blocks, as well as phase 2.”
