2Introduction waters such as streams, reservoirs, and lakes—our drinking water. This runoff also harms vegetation and wildlife withHistory of Porous Paving increased water volumes, velocities, and higher temperatures.Pebbles, cobblestones, and wood decking structures have been The Grasspave2 and Gravelpave2 systems protect against thisused since the dawn of civilization to reinforce where we walk dangerous runoff by processing and cleaning the water, thusand the roads we use. Little did we realize that these methods safeguarding the natural water cycle.had benefits over the modern trends of sealing up the groundwith asphalt and concrete. Porous, permeable or pervious State of the Earthpaving—whatever you prefer—became a method for addressing Invisible Structures, Inc. has developed an entire line of productsstormwater issues in the early 20th century. Concrete turfblock to address stormwater and environmental concerns. Rainstore3,for grass paving began in the mid-1940s Slopetame2, Draincore2, and Beachrings2and plastic versions were invented in the can work in addition to, or in conjunctionlate ’70s and early ’80s. Great advance- with, Grasspave2 and Gravelpave2 toments have occurred in pervious concrete, provide your site, home, or office withpervious asphalt, and other permeable sur- stormwater and environmental enhance-faces. We introduced Grasspave2 in 1982, ments. Our products can store and collectimproving upon these earlier concepts. In rain, provide erosion and sediment control,1993, Gravelpave2 was unveiled, the only efficiently convey and deliver water, andproduct specifically developed for gravel protect natural areas.porous paving. Fast forward to this millen- Advanced Technologynium, and Grasspave2 and Gravelpave2 are The Grasspave2 and Gravelpave2 systemsconsidered by most, the finest porous Grasspave2 large rolls and Gravelpave2 large rolls are based on a simple, but impressivepavers developed. (notshown)installquicklyandconformtothe contours technology—a series of rings (cylinders)Infiltration of the ground. connected on a flexible grid system. ThePorous paving allows rainwater to percolate cylinders are engineered to withstandthrough the pavement’s surface and back into the ground significant structural loads and the grid provides stability,(infiltrating), where the water is cleaned and returned to ground flexibility, and continuity for large areas. The grid system alsowater supplies. Porous paving improves upon impermeable sur- has the unique ability to be rolled up for easy shipping,faces, such as concrete or asphalt, which do not allow for this handling and installation.natural filtration. Rain collects airborne and surface pollutants This engineered design allows for any street-legal vehiclesuch as sediment, brake dust, chemicals, vehicle exhaust, oil, (and sometimes larger) to park or drive on our Grasspave2 orsalts, fertilizers, bacteria, and animal waste. On impermeable Gravelpave2 surfaces. The point load pressure is transferredsurfaces the polluted rainwater runoff (non-point source pollu- from the top of the ring, through the fill material and cylinders,tion) is collected, concentrated, and discharged to downstream to the engineered base course.Wallace Residence,Savannah,GA—Gravelpave2 creates a wheelchair-accessible surface by stabilizing gravel and supporting tire pressure.7% dry cement was mixed with gravel before filling rings.Cover photo: Westin Kierland Resort and Spa, Scottsdale, Arizona—Grasspave2 fire lane and Gravelpave2 fire lane (concrete widening).
Pentagon Remote Delivery Facility, Arlington, VA—Grasspave2 was selected for the helicopter landing pads (the four grass squares in center) on the largest “green roof” east of the Mississippi.
4The ring and grid structure is 92 percent void space allowing for under all conditions. It’s also a good design practice to strengthenthe healthiest root zone for grass (in Grasspave2) and more deco- concrete sidewalks and curbing that will be mounted by fire trucks.rative gravel (in Gravelpave2) for some of the most attractive CSI 32 12 43 Flexible Porous Paverspaved surfaces around. Less plastic means more natural looking In 1997 The Construction Specifiers Institute (CSI) came outsurfaces. This technology also makes for better runoff coefficients with a generalized listing (02795) for all porous paving products.and better percolation rates. However, since performance and application is varied even in the120 psi Maximum on Public Highways! porous paving industry, the 2004 CSI MasterFormat™ has adopt-Even empty, Grasspave2 and ed a new number 32 12 43 FlexibleGravelpave2 will support 2,100 psi Porous Paving, to recognize that(14,470 kPa)—well over the 120 psi Grasspave2 and Gravelpave2 arehighest truck tire pressure allowed in a class by themselves.on public highways. This is a safety Best Management Practicefactor of 17 times. When Grasspave2 Porous paving is recognized as ais filled with sand for part of the root Best Management Practice (BMP)zone medium, the strength increases by the Environmental Protectionto 5,700 psi (39,273 kPa). The safety Agency, the Center for Watershedfactor increases from 17 to 47 times. Protection, the U.S. Army Corp ofThe heavier a vehicle, the more axles Engineers, and countless other feder-and tires it needs to support the load al, state, regional and local authori-being carried. Grasspave2 and ties. In addition, Grasspave2 andGravelpave2 will meet and exceed Gravelpave2 are often mentionedall loading criteria. by name, as the product of choiceVehicle Loading Examples: for many of these agencies. Auto tires: 40 psi Truck tires: 110 psi DC-10 tires: 250 psi Applications The University of South Alabama, Mobile used Gravelpave2 in parking aisles F-16 tires: 350 psi Stormwater Management and Grasspave2 in the spaces. Fire truck with outriggers: 78psi The Grasspave2 and Gravelpave2(An 85,000 lb. truck distributed to systems can easily handle stormfour outrigger pads is equal to 21,250 lbs. for each outrigger pad water from an intense storm dropping three inches of rain in lesswith 12 18 surface contact with Grasspave2.) than thirty minutes! In one square meter (40 40 ) there areAll these vehicles are well within our 5,700 psi loading capability. 144 rings, two inches in diameter by one inch high. With one inchWith a sturdy base course design, our rings will easily perform of fill in the rings and a standard road base of sandy gravel sixBowditch Point Regional Park , Fort Myers Beach, Florida—Gravelpave2 parking bays blend in with the natural surroundings.
The Lincoln Hills Club, Lincoln, California—This amphitheater’s grass is reinforced with Grasspave2 to prevent compaction, and provide a stable, attractive surface for visitors.
6inches thick, our porous systems will percolate approximately Pedestrian, Horse Trails and Bicycle Paths1 ⁄2 inch of rain per hour! A seven-inch section can store 2.4 inches Garden paths, greenhouse aisles, sidewalks, park paths, andof water (about 20 percent void after compaction). Alternatively, wilderness trails paved with Grasspave2/Gravelpave2 providehard surfaces, such as asphalt and concrete, shed 95 percent of a stable surface for strollers, bicycles, wheelchairs, and horses.storm water. There are no puddles or mud and traction is very good. Tree roots break up hard surface sidewalks, but our mats flex toAesthetics accommodate such shifts and gradient changes. Plus, with theAs a designer, engineer, contractor, or homeowner, you can be sure high proportion of air, roots are discouraged from moving upward.Grasspave2 and Gravelpave2 can deliver a more beautiful surface Mountain bikers will not be able to tear up paths reinforced withand add a unique look to a site. Grass simply looks better than Grasspave2/Gravelpave2.asphalt and decorative gravel has been used for centuries in Our products can resistlandscaping. Space constraints can be dealt with by combining the destructive forces ofthe beauty of grass or gravel with the utility of paving. mountain bikes, allowingTrees and other vegetation not only survive, they thrive with your trails to be reopenedGrasspave2 and Gravelpave2. Porous paving has the ability to to bikes.deliver water, oxygen and carbon dioxide through the cross sec- Fire Lanestion—all essential to root survival. Concrete and asphalt suffo- By far, the most commoncate and starve the root zones of water and air. With Grasspave2 application for Grasspave2 andand Gravelpave2, you can now design in as many trees and plants Gravelpave2 installations is foras your site will allow. Grasspave2 and Gravelpave2 prevent com- fire lanes. Our long and establishedpaction while allowing for ample amounts of water and air. Cars history of providing safe, well-can then drive and park below tree canopies. Saving existing, constructed fire lanes began inmature trees is also possible with our products—our structures 1982 with our first installa-can come within inches of the mature tree trunk without damage. tion in Snowmass, Colorado,Our mats have the ability to flex with the tree root growth that near Aspen Ski Resort.would otherwise damage and crack hard surfaces. Since then, we have firmlyEnvironmental Benefits established credibility forGrasspave2 and Gravelpave2 not only protect the environment, this application. Tests havethey enhance it. All of our products are made from 100 percent been conducted by severalrecycled plastic—plastic that goes into improving the environ- fire departments in Aurora,ment and not into a landfill. Through bioremediation, porous Colorado and Irvine,pavers have the ability to clean pollutants (heavy metals, 96–99 California. Nearly everypercent; suspended solids, 95 percent; phosphorous, 65 percent; major U.S. metropolitannitrogen, 82 percent, hydrocarbons, up to 100 percent) out of area has accepted and usedstormwater. Our products also reduce erosion and soil migration, Grasspave2 in a firereduce site disturbance, and contribute to airborne dust capture lane. You will mostand retention. likely find a fire laneCooling the atmosphere and reducing the “urban heat island installationeffect” (cities being up to 10 degrees hotter than undeveloped in yourland) are added benefits of Grasspave2 and Gravelpave2. Both area.products can mitigate these increased temperatures. In addition,Grasspave2 promotes the conversion of carbon dioxide (green-house gas) into oxygen and has an “air-conditioning effect.”DrivewaysEnvironmental, economic, and aesthetic enhancements aredrawing homeowners and designers to use Grasspave2 andGravelpave2 in driveways. Most residential driveways are goodcandidates for our porous duo because of the reduced speed andlimited frequency of traffic. Our products can add beauty toresidential and commercial driveways.Parking LotsParking for churches and synagogues, stadiums, arenas, andoverflow at shopping centers, campuses, parks and more areideal for Grasspave2 and Gravelpave2. These sites generallysupport large numbers of vehicles but only on periodic basis.Stormwater management and green space can be combined withparking, reducing maintenance, real estate, and developmentcosts. A great design idea is combining durable Gravelpave2 All fire fighting vehicles can safely navigate even a wet Grasspave2 or Gravelpave2drive aisles with attractive Grasspave2 parking bays. surface. In a 1983 test this 100-foot ladder truck was lifted off the Grasspave2 by rear outriggers, and no ruts were caused by either outriggers or tires. The ladder was extended, rotated, and loaded with no depressions in the road surface.
Apartment complex, Concordville, Pennsylvania—Several overflow Gravelpave2parking lots encompass the majority of the perimeter area on the west and south sides of the property. Grasspave2 (not shown) is installed on site in two grass fire lanes.
8Grasspave2 Installation—Mats can be rolled out in minutes!600 m2 (6,000 sf) per two-person hour! For steps shown below—100 m2 (1,080 sf) per two-person hour! 1 2 3Place and compact sand and gravel base course. Apply Hydrogrow mixture. Roll out Grasspave2. 4 5 6Fill rings with clean sharp concrete sand. Hydroseed or lay sod. Roll sod with heavy roller. 7 8Ready for use after two mowing cycles. Use a regular lawn mower for maintenance. Do not aerate! TheGrasspave2 porouspavement system is comprised of a sandy gravel base course, Hydrogrow polymer-fertilizer mixture, the Grasspave2 ring and grid structure, sharp concrete sand, and grass seed or sod.
9Grasspave2 Installation Procedures Roll out Grasspave2, aligning the side hole fasteners over the side pegs. The warmth of the sun will relax the plastic so it laysThis installation section is only intended as an overview. Please flat. Cut the grid between rings using pruning shears. Incorporatereview our Grasspave2 Technical Specifications (available at the cut pieces in other areas, as needed, keeping the distancewww.invisiblestructures.com or call 800-233-1510) for between the rings uniform.comprehensive installation instructions. Fill rings with clean sharp concrete sand (AASHTO M6 or ASTMExcavate a space for the base course as determined by site soils C-33) using large rakes and brooms so that the tops of the ringsand loading requirements. Place and compact sandy gravel which show when done.should be a mixture of clean sharp sand and gravel varying in sizebut not exceeding 3⁄4 of an inch. To check porosity, use a hose to see Lay turf over the rings. On warm days, wet the sand first to lowerthat water flows into the base and drains away. Add subsurface sand temperature and provide moisture for grass roots. Seedingdrainage as necessary to low spots or locations with poor draining and hydromulching is also an accepted vegetating method at this soils. Install irrigation lines and sprinkler heads if necessary. stage. Repeated hydromulching/seeding may be necessary. Apply the Hydrogrow mixture that is included Roll sod with heavy roller to eliminate air pockets and make free with your order. Hydrogrow is a mix- sure roots are in contact with the sand fill. Water lawn as usual ture of polymer and fertilizer according to climatic requirements. designed especially for our Whether the area has been seeded or sodded, wait to drive on Grasspave2 system. grass until two mowings have been completed, by which time the root system will be established and the sod pieces locked into place. In an emergency such as the need for fire truck access, grass may be driven on immediately after installation. Use a regular lawn mower for maintenance. There should be no paver parts protruding through the surface that would damage mowers. Do not aerate!
10 1 Gravelpave2 Installation— Gravelpave2 Size/Shape Fill Requirements Sharp Angular Pea Gravel, Elgin, IL. You will need 1 of gravel fill, compacted. Be Do not use rounded pea gravel. careful to order enough for the compaction process and choose a gravel size that will nest well into the rings. We have found that 3⁄16 minus crushed stone and sometime 3 8 with limited small sharp screenings (#40 to #100 screen) works well. Washed gravel will roll within the rings Place and compact sand and gravel road base. and will also “roll about.” For this reason, we do not recommend pea gravel, even though it is 2 often very attractive. A visit to your local quarry is suggested. We have found that some geological Sonoran Tan 3 8 , Tucson, AZ. areas of the United States have limited types of sharp gravel available. It has been necessary to import gravel from a neighboring state, but remember the amounts are relatively small— the top one-and-a-quarter inch of the cross sec- tion. Gravel should be as free of fines as possible. To maintain porosity, avoid soft stone materials with low durability that will break easily. Roll out Gravelpave2, aligning the snap fit fasteners. Other Fill Materials for Gravelpave2 Please ask our staff for assistance with this 3 category since it is use-specific and often experi- Carbon Canyon 5 16 minus, San Diego, CA. mental. Ground rubber, crushed glass, crushed brick, and many other materials can be useful as attractive fill materials for various applications. Thermoset (epoxy, polyurethane, etc.) binders may be cost prohibitive for most projects, but offer unique design possibilities, including clarity, color enhancement (wet look), flexibility, and durability. Our technical support staff will assist with Secure mats with anchors provided (size and type selection of gravel sources. The photographic Hard Limestone 3 8 , Chicago, IL. may vary). samples shown on this page will help you narrow Add 25-30% clean sharp mason’s sand your gravel choices. Should you have questions to maintain porosity. 4 concerning the selection, please submit a small sample for approval prior to specifying or securing the materials. Decomposed Granite 3 8 Fill rings with clean gravel. 5 5. Crushed Granite 3 16 Compact gravel with vibrator roller or flat plate compactor (not shown).
11Mats can be rolled out in minutes!Gravelpave2 Installation Procedure process. Anchors should be placed inside the rings as close to the center as possible. Begin anchoring from one corner in aThis installation section is only intended as an overview. Please radial pattern.review our Gravelpave2 Technical Specifications (available atwww.invisiblestructures.com or call 800-233-1510) for Gradually place gravel fill (see suggested fill material on facingcomprehensive installation instructions. page) into rings by using a front-end loader and shaking out the fill as the machine drives forward. Carefully lower the bucketPrepare sandy gravel base course to a depth as determined when empty and back up while dragging it above the rings toby a soils engineer. Compact with a vibrating plate compactor or smooth out the gravel, finishing with a stiff broom. Wheel barrowuse a heavy motorized roller for large jobs. To test porosity, water and shovel works well for small jobs. Contractor tip—you canwith a hose and check to see that water drains readily through store excess material for future maintenance, top dressing asthe base course before installing the Gravelpave2 mats. may be necessary. Use rakes and/or push brooms to distributeRoll out mats with the grain (in the same direction) so that the gravel fill to a level slightly above rings so that compactingthe snap fit fasteners can be used with neighboring mats. To the fill will not uncover the rings.fit around boxes and curbs, cut the grid between the rings with Use a vibrating plate compactor or large driving roller again topruning shears and scissors or a small portable electric hand saw. compact the gravel fill. Additional gravel may be necessary toFasten the mats together using the snap fit fasteners that are finish filling the rings. Compact again until the material appearsmolded into the product inserting the prongs into the rectangular solid in the rings. Wetting the gravel may help it to interlock.openings. Tuck the fabric underneath the fasteners to keep joints Drive on the installation when finished. If car tires make aclosed. A quarter-inch nut driver head (6 mm) fits nicely over the pattern, there may be too much gravel or it may need additionalfastener to compress the pieces together. A piece of lumber placed compaction. It is expected that tops of the rings may be visible.under the Gravelpave2 mat will provide stability to aid in fastening. If sides of the rings show, then add more fill material and repeatSupplied anchors must be used to secure the mats to the the compaction process.base. Hammer anchors with washers at a rate of oneanchor per six rings in both directions. Useextra anchors around the perimeter ofthe Gravelpave2 install and in hightraffic areas. Reciprocatinghammers can be usedto speed up theanchoring
12Golf Industry Large RollsGravelpave2 and Grasspave2 golf cart paths give the look of a Our patented systems have a shipping, handling and installationnatural path through trees, along fairways, and around greens. advantage as well—large rolls. Our standard roll size (modelThe flush surface requires no trimming or edging. Traction is 2020) covers 431 sq. ft. (40 m2) and weighs 192 pounds (87 kg).excellent with Gravelpave 2 and Grasspave2 traction is slightly Other roll sizes are available. Installers of our products havebetter than grass. Grasspave2 repeatedly commented that theyand Gravelpave2 can enhance enjoy the easy installation.your golf cart staging area, Lab Compression Test Results Rolling out Grasspave2 ispedestrian traffic area, parking Load-bearing capacity of filled Grasspave2/Gravelpave2 similar to rolling out carpetinglot, road shoulder, and mainte- rings vs. concrete, and vehicle loading examples and coverage is fast and effi-nance yard. cient. The mat system can be easily cut to fit around trees,Automobile Dealership Displays irrigation, curbing, or otherCar dealerships have discovered 2 and Gravelpave2 terrain. The rolls have snap-fitthat Grasspave connectors to attach to adjacentare perfect for automobile dis- Grasspave2/Gravelpave— rolls, making one unified, con-play areas. Dealerships now 5,720 psi capacity (filled) tiguous system. This unifiedhave an option when it comes mat system adds stability andto adding paved areas for car continuity in design. Grasspave2transport and display. Dealerships Concrete—3,000 psi capacity can just as easily be snapped to Fire Truck Outriggers—81 psilike the “soft” attractive look grass Gravelpave2 to add stability andand decorative gravel provide. F-16 Tires—350 psi DC-10 Tires—250 psi product variation. Truck Tires—110 psi Auto Tires—40 psiUtility and Maintenance Vehicle Access HydrogrowProviding your site with impor- Another reason Grasspave2tant utilitarian functions with- is the industry leader is theout compromising beauty addition of Hydrogrow soilis simple. Grasspave2 and amendment, which is suppliedGravelpave2 can incorporate a Runoff Comparison Chart with your order. Hydrogrow isstructural road without inter- Runoff coefficients, Grasspave2/Gravelpave2 and engineered to help grass growrupting your landscaping. No sandy gravel base over various soil types in our sand based root zone.obtrusive concrete or asphalt The results are amazing andaccess roads are necessary to Asphalt our Grasspave2 areas oftenget to window washing areas, 2 over cla y look healthier than surroundingpump stations, microwave tow- velpave ve2 /Gra turf. By using this special mix-ers, tanks, or electrical boxes. Grasspa ture in the sand, porosity will 2 er loa m/clayUnique Applications ave ov be maintained, turf will be 2 /Gravelp ve attractive, and aeration willOur mats are installed in some Grasspa m not be necessary.unique and interesting places: 2 over sa nd/loaHelicopter landing pads, race car 2 rave lpave ave /G Sand Filldisplay areas, outdoor amphithe- Grassp Grasspave2 is the only grassater seating, under picnic tables, paver on the market specifyingunder concrete pavers (support), sand as part of its cross section.airplane display and transport, Grasspave2/Gravelpave2 over sand Sand is the best medium to pro-cemetery marker reinforcement, vide water and air to the rootseave drip lines and more. Inches of Rain During 24 Hours and still provide high compres-Installations are not limited 2 2 Calculations include GP /GV placed over 6 of sandy gravel base course, laid over native soils indicated. sive strength. The United Statesto traditional paved areas. Golf Association uses sand for every USGA golf course and nearly every professional and colle-Grasspave2 Characteristics giate turf athletic field uses a sand cross section as well. Topsoil (or other organics fill material) in the rings will eventually compactRing and Grid Structure and damage the root zone. Sand negates the need for mechanicalGrasspave2 is by most accounts the best flexible grass paver aeration, which can damage Grasspave2 and other grass pavers.made today. Its unique ring and grid structure allow for flexibility,stability, and exceptional grass growth. With 92 percent void Strength When Installedspace for healthy roots and 100 percent grass coverage, Grasspave2 When installed over a thick base course and compacted to 95is the industry’s preeminent choice. Our installations are hard to percent modified Proctor, sand-filled rings can support 5,700find because they are invisible! With so little plastic near the pounds per square inch (psi) without deflection or compromise tocrown of the grass, the blades of grass are not smashed by prod- safety. The cylinder is the strongest shape to support compressiveuct. Root development is not interrupted from spreading laterally. loads because it has no corners. Supporting heavy loads with theThe rings are strong and rigid, keeping grass root systems pro- rings allows us to use less plastic in the product creating a 92tected from harm. The roots grow directly downward, deep into percent void area for root development, combined with strength!the sandy gravel base course. Less plastic means a lower cost for you.
Fort Shantok State Park, The Mohegan Tribe, Uncasville, CT—Low-maintenance parking lot stable for cars, strollers, and wheelchairs. This lot is plowed in the winter.
14Traffic Frequency Should the fasteners of one mat not align over the distance ofGrass as a surface material can withstand from two to six (varies another mat, then anchor pins (or eight inch ring shank nails andwith grass species and environmental conditions) trips daily over large washers) can be used to secure the mats along the seam.the same spot. This suggests that most parking applications we Forcing the alignment can cause the mats to ripple and not laypave with asphalt today could be paved with Grasspave2 instead. down evenly.Vehicles can remain parked on grass for extended periods oftime, provided some relief can be given for a few days for the Traffic Frequencygrass to recover. Gravelpave2 has no limits on frequency or duration of traffic on the system. Park or drive as often as you like onLifespan Gravelpave2. However, speeds should be keptGrasspave2 has a projected at or below about 20 mph (30 km/h).lifespan of 60 years.Compared to asphalt Durabilitywith a lifespan of 15 Grasspave2 and Gravelpave2 areyears; and concrete made from flexible High Densitywith a lifespan of 25 Polyethylene (HDPE) plasticyears, Grasspave2 will with UV inhibitors, whichsave you money on withstands repeatedreplacement costs. freeze-thaw cycles and continuous subzero tem-Irrigation peratures without crack-Grass needs water and you ing. HDPE resists aggres-may need to have irrigation sive chemicals such as roadinstalled. Grasspave2 has a sand salts, motor oils and fuels. HDPEbased root zone which usually Standard colors include: is highly abrasion-resistant and isrequires slightly more water than a Tan, Black, Pewter Grey, Terra Cotta. unaffected by extremes in pH. A well-normal topsoil or organic root zone. If maintained Gravelpave2 installation willgolf courses in your area use irrigation last 25 years in most climates.systems, you probably should inyour Grassapave2 installation. Aesthetics Part of what draws many designers to use Gravelpave2Gravelpave2 Characteristics Invisible Structures—Standard Product Roll Sizes is the ability to have an area maintain a natural look. ManyFabric, Ring and Grid Width Length Diameter Area Weight times native soils or gravel canWhen we developed Model m ft m ft m ft m2 ft2 kg lbs be used as fill material, comple-Gravelpave 2 in 1993, our 1010 1 3.3 10 32.8 0.5 1.7 10 108 22 48 menting surrounding areas.goal was to provide designers Gravelpave2 is available in foura second option for a porous 1020 1 3.3 20 65.6 0.8 2.7 20 215 44 96 standard colors—black, tan,pavement that can tolerate 1520 1.5 4.9 20 65.6 0.8 2.7 30 323 65 144 gray, and terra cotta (customhigh frequency and low-speed 2020 2 6.6 20 65.6 0.8 2.7 40 430 87 192 colors are available at addition-traffic. By molding our ring al cost). Ring colors are intend-and grid structure onto a non- 2520 2.5 8.2 20 65.6 0.8 2.7 50 538 109 240 ed to blend with the gravelwoven polyester filter fabric, 2 2 2 Rolls can be installed manually (2 people advised). Rolls apply to Grasspave , Gravelpave , Draincore , color so they will be less visible 2 and Slopetame .we were able to create a new should some portion of the ringsproduct that contains gravel show. A small amount of excessand prevents particle migration stone fill should be left above the top of the rings to provide visu-and rutting. al cover and additional UV protection. This excess will migrate,Gravelpave2 is the only system specifically designed for aggregate but usually not very far.containment porous paving. The cylinders displace the load onto an Size and Shape Requirements for Gravel Fillengineered base course and hold the decorative gravel in place. The You will need one and a quarter inch (3.2 cm) of gravel fill,fabric keeps the top-dress gravel from compacting into the road before compaction. After compaction the gravel should be onlybase, acts as a weed and vegetation barrier, and suppresses dust. be slightly higher than the rings (1⁄8 inch, 3 mm above). TheTraditional pavements, including gravel roads, are designed to following criteria for gravel fill will make the most of theshed water and keep it away from the pavement’s cross-section. systems performance:Gravelpave2 is designed to do the opposite—welcoming water • Hard—resistant to breaking, crushing or crumblingdown through the system. Plus, Gravelpave2 will not rut, wash- • Sharp and angular (do not use rounded pea gravel)board, or puddle like traditional gravel roads. • Clean, washed (free of fines) • Size 3⁄16 to 3⁄8 inch (5 mm to 1 cm)Snap-Fit FastenersDesigned into Gravelpave2 is a snap-fit fastener, a two-pronged Other fill material may be used in certain situations, but may bearrow that fits into a rectangular slot. Simply push the slot over considered use-specific or experimental. Please consult with ourthe prongs to easily snap together panels of Grasspave2. To take technical support staff regarding fill material not meeting thethem apart, just squeeze the prongs together and lift off the slot. above criteria or for installations requiring “binders.”
Denver Tech Center Corporate Client, CO—Curving Grasspave2 firelanes around both buildings lends opportunity for private outdoor lounge areafor employees who can also enjoy the garden view from their office windows.
16Dust Suppression In addition to cost savings in the design phase, you may be ableDirt and gravel roads have the potential to kick up dust and dirt to eliminate other components during installation such as rootwhen traversed. Many communities have regulations limiting or protection for trees, grates, manholes, curbing, and tree andeliminating gravel surfaces from new construction. Rest assured, vegetation removal costs.if you design a Gravelpave2 surfaceyou will be getting a virtually dust- Maintenance and operationsfree surface. The clean and washed costs are significantly reducedfill material required to fill the over asphalt and concrete surfaces.rings will not have any more dust A. (Andy) E. Lindsey, Director ofthan an asphalt-paved surface. Grounds Maintenance, UniversityGravelpave2’s geotextile fabric of South Alabama, in his writtenwill prevent the dust-sized particles analysis dated February 18, 1999,contained within the base material compared the cost of our porous(existing gravel surface or dirt), systems to asphalt pavement usingfrom being displaced by moving historical data from universitytire or wind forces. records. The conclusion was a $56,000 savings over 20 years, by using Grasspave2 and Gravelpave2.Industry Advantages Our products can save you the mostEconomic Advantages money by combining your surfaces’Whether you are an engineer, uses into one area. Multiple surfacearchitect, landscape architect, use means savings on real estate,contractor or homeowner you will design costs, maintenance, insur-be concerned with the cost of you ance and more. You can have a fireproject. Grasspave2 and Gravepave2 lane that doubles as “green space”will save you money. Our products for employees or visitors, combinewill save on design costs, installa- a parking lot with a bio-swale andtion costs, component materials, stormwater mitigation system, andmaintenance/operations expenses expand your lawn into the driveway.and lifecycle costs. We can find a The Grasspave2 and Gravelpave2way to reduce your site expenses Oakdale Nature Preserve, Freeport, Illinois—Gravelpave2 reduces erosion and installations at Reliant Stadium,with our porous pavers. rutting in this ADA accessible trail. Houston, Texas, pull quadruple duty, providing over seven acres ofWhen designing, you may be able to eliminate or reduce storm- parking, stormwater mitigation, required “green space,” and anwater filters, detention basins, conveyance lines, modifying outdoor festival site which generate additional income.grading requirements, or many other “necessities” associatedwith asphalt or concrete. A great deal of your stormwater As mentioned above, Grasspave2 and Gravelpave2 have a longermitigation plan can be built into Grasspave 2 and Gravelpave2. lifespan than asphalt. Compound the above savings with the longer lifespan, and you can have a lifecycle cost which can saveInstallers have been astounded by the speed and efficiency thousand of dollars on even moderately sized installations.for which large areas can be accommodated by our large rolls.Unrolling our mats, snap fitting, and cutting is easy and requires Competitive Advantagesno special machinery. Please view our technical specifications Our porous pavers not only have advantages over impervious(from www.invisiblestructures.com, call 800-233-1510, or avail- surfaces, we are proud to compete with any other plastic porousable through our partner network) for the installation procedure. pavers manufactured. Our products are the strongest on theA brief installation overview is also on pages 8 and 10). market 5,721 psi installed (39,273 kPa, 823,844 psf or 7,414,416 psy), or 2,100 psi empty. Grasspave2 and Gravelpave2 have Compacted sandy gravel road base placed above compacted subgrade, 95% modified For Grasspave2: Proctor density. Gravelpave2 rolls are laid, pinned, and filled with clean, sharp gravel. Compacted sandy gravel road base placed above compacted subgrade, 95% modified.
Reliant Stadium at Reliant Park, Houston, TX—The largest engineered grass poroussystem 30,800 m2 (317,000 sq ft) provides parking, stormwater management, anda cool surface for festivals and concerts.
1892 percent void space for the best root development and grass • Keep the porous paving area free of sediment and erosion fromcoverage (Grasspave2) and the most volume available for desired adjacent areas as they can cause drainage and aestheticfill (Gravelpave2). Most other plastic pavers come in rigid unit issues. Extra care should be taking for use in swales or berms.blocks, which are cumbersome to install and difficult to cut • Slope should be considered. Grasspave2 and Gravelpave2and shape. Grasspave2 and Gravelpave2 rolls are considered perform the best for all vehicles when the slope is no greaterthe favorite to work with by installers, than 8 percent. Light vehicles (golffor the flexibility, continuity, and speed carts), bicycles, and pedestrian areasof installations. Grasspave2 is the only can have up to a 20 percent slope.product on the market specifying sand Grasspave2 in fire lanes should notinfill for the grass roots. Sand is recom- exceed five percent (consult your localmended as the infill of choice for grass fire departments).pavers by Professor Bruce K. Ferguson, • Check the permeability of existingUniv. of Georgia, author of the book, underlying soils. Percolation rates“Porous Pavements.” should be .64 cm to 1.3 cm of water per hour (EPA guidelines).Competing Technologies • The water table should be aboutPorous paving technology has made three feet (approx. 1 m) below basegreat strides not only in flexible plastic course in most instances.pavers but in other areas as well. • Bedrock should not be closer thanPermeable asphalt, permeable con- two feet (0.6 m) below base course.crete, interlocking unit blocks, rein- • Avoid use of Grasspave2 andforcement mats, and concrete grid Gravelpave2 in areas where high-pavements, have all improved and speed acceleration or braking andadvanced to meet the growing demand turning occur. Examples arefor environmentally friendly technolo- Vancouver City Works Yard, Vancouver, British Columbia—main staff entrances and exits to parking lotsgies. It is Invisible Structures’ firm parking lot, done in Gravelpave2. that connect to higher speed roads.belief that you should use porouspaving, even if it is not our product If your site varies from these condi-line, whenever possible. The more tions, please consult ISI directly,you use these technologies, the better 800-233-1510, as some conditionsaccepted they become: If you have to can be overcome with design andpave, porous pave! component adjustments.Invisible Structures also contends Base Course Designthat while these competing tech- Calculating the depth and compositionnologies have their place, in most of materials for the base course incor-instances, our Grasspave2 and porates the same design criteria as forGravelpave2 systems outperform, other pavements:last longer, require less maintenance, • Load-bearing capacity of native (orlook better, and are easier to install. fill) subsoil,Check with our technical specialists • Plasticity or impact of moisture onat 800-233-1510 for the latest data. strength and longevity, • Frostheave potential, and • Traffic load, frequency and/orDesigning for Grasspave2 and duration.Gravelpave2 Sample Base Course DepthsDesign for Use Please consult with a soils engineerThere is an area in your development, for site-specific base requirements.site, or home that will most likely ben- Generally, the depth that is used underefit from Grasspave2 and Gravelpave2. asphalt will be the requirement underWe advise that you take a look at prop- Fire lane, San Mateo, CA—Many native grasses and other attractive Grasspave2/Gravelpave2. Golf carts ander use patterns, site conditions, and vegetation can be grown in Grasspave2. pedestrian traffic may require nothingother specifications to get full advan- over sandy gravel soils, and just two totage and long life out of our products. Invisible Structures, four inches of base course (5–10 cm) over very weak soils. Cars800-233-1510, is available for preliminary design assistance and usually need a six- to eight-inch base course (15–20 cm). Buses,consultation. Please note that other porous paving systems are trucks, and fire engines can easily require eight to 12 inchesNOT interchangeable with Grasspave2 or Gravelpave2, consult (20–30 cm) or more. The use of geotextiles, below the base is notour technical specifications for full installation instructions. required, but will prevent integration with subsoils and is strong-Considerations for Design: ly advised in areas of clay or silt soils and frost heave. Do not use • High use, low speed, and unlimited traffic volume is optimal 100 percent limestone base as limestone will compact and become for Gravelpave2 impervious—If limestone must be used, mix with 25–30 percent • Low to moderate use, low speed, with recovery time is sand (AASTO M6 or equal). perfect for Grasspave2 or Gravelpave2
Garden of the Gods Park, Colorado Springs, CO—Horse and pedestrian trail stabilization toprevent ruts previously as deep as three feet. Horse traffic contributes to loose soil erosionwithout Gravelpave2. Terra Cotta rings were used to match existing sandstone soils.
20Bedding Sand Not Necessary seems to be no problem with sod selection for fire lanes. If theDo not use a sand setting base with our products. Unlike concrete Grasspave2 area has just been seeded or sodded, drive on it onlypavers, bricks, and other rigid pavers—our Grasspave2 and in an emergency.Gravelpave2 are flexible and do not require sand to level. Gravelpave2 MaintenanceEdge Protection Potholes will only appear if the base course has not beenFor aesthetic and maintenance considerations, you may want to compacted properly before laying the rings or if the base materialdesign in a durable edging material to separate our porous is allowed to mix into clay soils below (use nonwoven fabric topavers from adjacent areas of turf or to simply delineate a fire keep separate). Should this occur, remove a section by vacuuminglane or path. With Gravelpave2, an edging can prevent vegetation the gravel from the rings, unfasten the snap fit fastener, bringfrom encroaching onto the system and can prevent the gravel fill the base course to the proper grade and compaction, put thefrom migrating at the edge. Steel, aluminum, wood, brick, or con- Gravelpave2 square back in place, anchor, and fill to the top ofcrete are all acceptable edging materials. Keep the edging flush the rings. Seasonally check the rings in high-traffic areas andor slightly higher than the porous paver grade. entrance lanes for lower levels of fill and replace by sweeping gravel from other areas to bring it level again. Leaves should be raked or vacuumed and not allowed to decay. Organic matter willMaintenance and Operation stimulate weed growth and reduce porosity. To attack any occa-Grasspave2 Maintenance sional weeds that may locate within the Gravelpave2 installation,Irrigation is required in dry climates. Any popular pop-up system simply spray them with a weed killer (such as Roundup™) andcan be used. Simply cut out rings to reveal the irrigation head. If remove them when dead.golf courses in your area use irrigation systems, you probably Cold Climate Concernsshould in your Grasspave2 installation. Be careful not to over- Porous pavement thaws faster than conventional pavementswater as this will encourage shallow root development. because it allows melted water to flow directly through theFertilize once a year with an NPK slow-release fertilizer that pavement, increasing the temperature in the cross-section.contains trace elements. There are many brands on the market. Grasspave2 and Gravelpave2 are made from flexible HighDo not aerate! You’ll end up with product damage. When installed Density Polyethylene (HDPE) plastic with UV inhibitors, whichusing sand in the rings, there will not be a compaction problem. withstands repeated freeze-thaw cycles and continuous subzeroBe careful not to use clay-based sods in pedestrian or vehicular temperatures without cracking.traffic areas—use sandy soil sod, or seed and mulch. TherePrivate Residence, Houston, TX—Grasspave2 supported grass sections in this custom home driveway.
Grand Canyon Trust, Flagstaff, AZ—Thirty-car employee parking lot after several years of snow removal and excellent maintenance. Spaces are defined with concrete bumpers.