The Geosynthetic Matrix
From wetlands reconstruction to channel reinforcement, geosynthetics plays an integral part.
Cal Callahan of Merlin Cal Callahan Associates in Destin, FL, is often called upon as a contractor in erosion control products along Florida’s coastal areas. Over time, he has become an advocate of soft armoring versus the hard armoring of cement walls, seawalls, and planking.
Callahan cites a host of reasons for his choice: It’s more economically feasible, it offers the benefits of stormwater control and containment without the heavy application of stormwater conveyance systems, and it eliminates lost property to retention ponds and heavy drainage swales.
Often, geosynthetics and geogrids have become the erosion control tools of choice, with projects incorporating geocellular confinement systems, filter fabric, barricades to curb beach erosion, erosion control blankets and turf reinforcement mats, silt fencing, and reinforcement for segmental retaining walls.
Callahan’s first experience with geosynthetics was in the spring of 1998. In Niceville, FL, an old landfill construction site was to be reclaimed. A 700-foot wall meandered near a creek and around the border of wetland area in the town. “It was an environmental issue where they were using a cellular confinement system to provide a filtering process to contain and filter all runoff before it got into wetland areas or creeks, and to eliminate the heavy runoffs,” he explains.
Eight-inch layers of geocell ranging from 15 to 18 layers in height were used to form a boundary around the area, where several businesses—a motel, a restaurant, and an auto parts center—were later added.
Two years later, Callahan turned to Envirogrid, manufactured by GeoProducts, for a project in conjunction with the Volusia County Mosquito Control District in Florida. The district installed the HDPE cellular confinement system along a canal area. Excavation had taken place between the canal and an adjacent subdivision, and the project helped the property owners regain about 40 feet of land, turning it into a green area that serves as a natural barrier between the subdivision and the canal area. The Envirogrid was installed in a recessed area, and vegetation was planted in the open cells to give the area a natural look.
For Callahan, using these products is somewhat like building a layer cake. “The first engineers I worked with pointed out that it’s necessary to establish a solid foundation that will be able to adjust to the different levels—since you are tying into wetland areas—in a floating mat reservoir type of structure,” Callahan says.
What Callahan’s company has since recommended, based on that advice, is #57 stone encapsulated in the appropriate nonwoven filter fabric. “In our projects, we recommend the 8-ounce nonwoven fabric because it is strong enough to contain the filtered materials as well as absorb the runoff and filter it. It also withstands all the various stress pressures,” he says.
Callahan says the cases in which his company is involved usually include heavy runoff situations, filtering processes or wetlands, or environmentally sensitive areas. “You create a solid foundation,” he says. “You also allow for the stormwater containment, filtering, and also the slower dissipation of the runoff back into the wetlands or natural areas.”
Cement, on the other hand, tends to create a scouring action. “On seawalls, such as on the top inside of the seawall and the lower outside—the water side—you always have severe scouring actions that remove your materials,” Callahan says. “With this type of application, you’ve got a constant soft-armoring process that eliminates the scouring action that takes place. It contains filters and absorbs with the same strength that these hard-armoring processes react to.”
Callahan’s projects are engineered so that every third layer of the cell structure has a fabric containment, not allowing any migration outside of those areas.
“It also will handle any stress being applied on the wall,” says Callahan. “With anchoring, which is done with rebar or stakes, it totally locks in each area in encapsulated compartments.”
In another project in October 2003 at Santa Rosa Beach in Florida, a group of three- and four-story high-end vacation homes were bordered by a 6-foot solid-wall fence on one side, and on the front side, the property was well below the level of the road. Recent road improvements caused considerably more runoff to course down driveways and toward the houses than originally anticipated. In one case, the runoff scoured out the full length of the house.
Callahan’s company addressed the problem by using a 100% biodegradable coconut blanket as a liner, and then placed geocells on that, filling them with sand and continuing the process for four layers. Landscapers planted various dune-type plants. With all of the weather events that have since affected the area—including hurricanes—there has not been an inch of property loss, Callahan notes.
Callahan’s company addressed the nearby asphalt roadway as well, where there had been a 5-inch height variation between the road and gravel shoulders. “We put down porous pavers and filled them with number-89 stone that would collect the water as it came off the road and dissipate all those runoff energies,” he says.
In 2004, Callahan’s company was involved in a project on the Choctawhatchee Bay in the Niceville area. Residential property bordered wetlands and the bay. The original plan called for 10- to 12-foot-high retaining walls and plank walls, but Callahan’s company recommended the use of the cellular confinement system instead.
“It would allow them to expand the property out to the edge of the property line, whereas with that wall, they would have had to have an 8- to 10-foot buffer between the wall and the wetland area,” Callahan explains. “This way, they have full use of the area. Its original acceptance was based on the fact it added about 15 feet to their garage, parking, and turnaround apron, so they could back out safely, park their cars, and handle more cars. The house was set below the street level at a 35% incline, and the garage level was about 10 feet below the street.”
Callahan’s company used a 16- to 18-inch depth of #57 stone wrapped in 8-ounce nonwoven fabric to create a self-contained foundation system. They alternated each layer with a permanent coir turf reinforcement mat; the coir portion will biodegrade in three to four years, but the geogrid system will last indefinitely as a permanent stabilizing liner.
Lining every layer ensured there would be no problems for the homeowner or filtering processes, Callahan says. At higher levels, where strength wasn’t a consideration, Callahan’s company used a 4-ounce nonwoven fabric as a liner.
“That particular project started out as 40 feet long and five to six layers high, and in working with the US Army Corps of Engineers in the property delineation, it came out to be about 140 feet long and 15 to 18 layers high, so that it totally encapsulated the boundaries of the property, contained all of the structure around the pool, and terraced down into the wetlands and bay area so that they would have a surrounding containment of their property,” explains Callahan. “But it would handle all of the runoff from their pitched roofs that were metal without gutters and the runoff from the 30% slopes.”
When high waters come in from the bay, such as from hurricanes, the system can absorb and dissipate the wave action without damage to the system or loss of property.
“Works Like Concrete, But Better”
In San Juan Capistrano, CA, an open channel constructed in the 1960s that feeds into the San Juan Creek basin and eventually drains into the Pacific Ocean was severely eroding and undercutting the concrete sideslopes. During the 1997 to 1998 El Niño era, a large summer storm began to undermine the walls, causing major erosion.
“We were worried about a possible risk created to the neighborhoods,” says Joe Mankawich, associate engineer for the City of San Juan Capistrano. The city formed a list of objectives in rehabilitating the channel: Minimize erosion during precipitation events, increase aesthetics along the channel, minimize long-term maintenance problems, reduce chemical particulate matter from residential runoff, and minimize the costs of construction and maintenance. While examining the options, the city instituted temporary measures, such as repairs to the riprap and concrete portions of the channel walls.
But in considering more permanent measures, city officials became concerned about the use of riprap on the steep channel sides. Additionally, the channel flowed between two affluent neighborhoods, so aesthetics was a concern.
 |
PHOTO: COLBOND |
| Concrete-lined channel before matrix was added. |
“The idea of a geofabric-lined channel came up,” Mankawich says. “Also, the city had recently started building a groundwater recovery plant, and we were looking at ways to recharge the basin, because now we were going to be using basin water for drinking water with the reverse-osmosis plant we were putting in. When you start thinking along those lines, you realize a concrete-lined channel will direct rainwater straight out to the ocean.” Any chance of the water percolating down to the groundwater would be lost.
City officials thought the channel presented a good opportunity to address the challenge with something that not only looked good but also functioned better to retain some of the water and percolate it down into the ground.
P&D Consultants, an environmental planning and engineering firm in Orange, CA, calculated the flow of water within the localized tributary that flows into the channel, which collects runoff from more than 300 acres in a valley with hillsides more than 200 feet high. Storm drains from existing development discharge directly into the channel. The water flows into the channel from a 10- by 4-foot concrete box culvert. The trapezoidal channel is 1,700 feet long and 4 feet deep, with a 10-foot bottom and sideslopes of 1.5:1. The estimated flow rate of the channel was 500 cubic feet per second, a flow that generates a shear force on the channel bottom of about 4.5 pounds per square foot for an extreme storm event.
P&D reviewed many options to address the problem, including riprap, Reno mattresses, concrete, and turf reinforcement mats. The firm, along with the city, decided a root reinforcement matrix that would not restrict vegetation growth—but that would meet the required flow conditions—would be the best solution. Enkamat R2M, a three-dimensional nylon root reinforcement matrix from Colbond Geosynthetics, was chosen. The matrix keeps the vegetation and soil from eroding during extreme hydraulic flow conditions. It does not unravel or lose its structural integrity during or after installation; therefore aquatic life within the basin would not be compromised from loose synthetic fibers floating downstream. Cost was another factor in the choice. Riprap was estimated to cost 15% to 20% more and concrete, 40% more.
During the 2000 installation, a mulch was applied on top of the Enkamat to ensure rapid germination, minimize seed displacement, and assist in the establishment of mature vegetation. Installation was completed in two weeks. In 25 rain events that followed, neither the channel nor the vegetation was damaged, even during peak rainfall and hydraulic activity. City officials were pleased that the project met federal and state requirements for the National Pollutant Discharge Elimination System Phase II and intend to use the material in future projects.
There have been a number of large storms since the installation, and city officials were worried that the native plants on the bottom of the water would be washed out in the first rain, but that didn’t happen.
“Now we have a beautifully lined channel and it has worked perfectly,” says Mankawich. “It works like a concrete-bottom channel, but it looks a lot better.”
Wally Ariand, president of ASW Construction in Edmonton, AB, Canada, a company that works in erosion control, is using geosynthetic materials to protect and line ditches, the edges of creeks, bridge piles, and building berms.
Ariand is an advocate of using geosynthetics and geogrids in erosion control projects. “When you look back 20 years ago and you see the products that are out there today, it’s making a big difference on protecting our waterways and our streams,” he says. “I think there should be more of it used.”
Ariand says his company is becoming increasingly driven by the requirements of the general contract for Alberta’s government; 75% of his company’s work is government, and the remaining is commercial. Applications that lend themselves to geosynthetics and geogrids include new subdivisions, new highway projects, and oilfield work, notes Ariand, who uses EMCO Ltd. products. Geogrids are also used in retaining walls, holding back the earth from moving as new structures are constructed.
“It stops the eroding, it’s going to protect streets, and it seems to be a good product for what it was designed to do. It is working,” Ariand says. “And that’s what most of the engineering firms are requiring.”
Ariand says there are no particular challenges involved in using geosynthetics and geogrids in terms of the installation. “It’s straightforward,” he says. “If you can read the blueprints, you’re going to have it made.”
Meanwhile, in Virginia Beach, VA, AGVIQ Environmental Services was called upon in late 2003 to assist in erosion control in a 2-acre wetland construction project. Dave Leadenham, program manager for AGVIQ, says that after much field investigation, the client noted that the existing clay onsite was not consistent throughout the proposed parcel of land for wetlands.
Many alternatives had been considered to address the erosion control issue, but cost and installation ease and time were major considerations. Quality Lining’s 40-mil LLDPE geomembrane liner was chosen. The product is widely used for wetland construction and landfill caps, two applications where earth fill will be placed on top of the installed geomembrane. Compared to HDPE, LLDPE features higher elongation properties, so it doesn’t break as easily, and a puncture resistance that is preferable when a subgrade is unstable or where compaction is not possible, Leadenham notes.
Quality Lining did the installation. The wetlands are in an hourglass shape that required many different lengths of the rolls of materials, and the sheets were deployed in a sequence, Leadenham says. The installation methods are essentially the same as used with all polyethylene geomembranes. Straight seams are typically achieved with a double-track wedge welder, and specialty seams, such as a tie-in to an existing liner or installation of pipe penetration “boots,” are made with an extrusion welding method. A quality check was performed.
“We probably had nearly 30 sheets and seams over every couple hundred foot lengths, so that was the most critical part,” Leadenham notes. “They did a visual [inspection] on the subgrade to make sure there were no sticks or twigs or anything poking out. We rely on our subcontractor’s quality check throughout the connection. All you need is one stick to come up through and potentially puncture the liner. The lining material itself is very susceptible, and in similar jobs like this, we’ve used other textured materials for landfill caps and covers.”
Leadenham says he has used different types of geomembrane materials in his 30 years in the environmental industry.
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“What the state requires and what the client requires is something that allows the water in as it infiltrates wetlands and not just to seep out to let the wetlands dry out and all of the plants die,” he says. “So we had to have that permeable layer below. This particular liner material forms very well to the existing contours so if there were any dips or bends in the liner material, they smoothed over the top of it.”
AGVIQ coordinated efforts with Quality Lining by covering the liner with soil. The last step entailed flooding the wetland areas and plantings. Leadenham says the job was successful: “The wetlands are starting to grow, and that’s an important thing.”
Author's Bio: Carol Brzozowski is a journalist living in Coral Springs, FL.
July-August 2005
The Geosynthetic Matrix
From wetlands reconstruction to channel reinforcement, geosynthetics plays an integral part.
Cal Callahan of Merlin Cal Callahan Associates in Destin, FL, is often called upon as a contractor in erosion control products along Florida’s coastal areas. Over time, he has become an advocate of soft armoring versus the hard armoring of cement walls, seawalls, and planking.Callahan cites a host of reasons for his choice: It’s more economically feasible, it offers the benefits of stormwater control and containment without the heavy application of stormwater conveyance systems, and it eliminates lost property to retention ponds and heavy drainage swales.
Often, geosynthetics and geogrids have become the erosion control tools of choice, with projects incorporating geocellular confinement systems, filter fabric, barricades to curb beach erosion, erosion control blankets and turf reinforcement mats, silt fencing, and reinforcement for segmental retaining walls.
Callahan’s first experience with geosynthetics was in the spring of 1998. In Niceville, FL, an old landfill construction site was to be reclaimed. A 700-foot wall meandered near a creek and around the border of wetland area in the town. “It was an environmental issue where they were using a cellular confinement system to provide a filtering process to contain and filter all runoff before it got into wetland areas or creeks, and to eliminate the heavy runoffs,” he explains.
Eight-inch layers of geocell ranging from 15 to 18 layers in height were used to form a boundary around the area, where several businesses—a motel, a restaurant, and an auto parts center—were later added.
Two years later, Callahan turned to Envirogrid, manufactured by GeoProducts, for a project in conjunction with the Volusia County Mosquito Control District in Florida. The district installed the HDPE cellular confinement system along a canal area. Excavation had taken place between the canal and an adjacent subdivision, and the project helped the property owners regain about 40 feet of land, turning it into a green area that serves as a natural barrier between the subdivision and the canal area. The Envirogrid was installed in a recessed area, and vegetation was planted in the open cells to give the area a natural look.
For Callahan, using these products is somewhat like building a layer cake. “The first engineers I worked with pointed out that it’s necessary to establish a solid foundation that will be able to adjust to the different levels—since you are tying into wetland areas—in a floating mat reservoir type of structure,” Callahan says.
What Callahan’s company has since recommended, based on that advice, is #57 stone encapsulated in the appropriate nonwoven filter fabric. “In our projects, we recommend the 8-ounce nonwoven fabric because it is strong enough to contain the filtered materials as well as absorb the runoff and filter it. It also withstands all the various stress pressures,” he says.
Callahan says the cases in which his company is involved usually include heavy runoff situations, filtering processes or wetlands, or environmentally sensitive areas. “You create a solid foundation,” he says. “You also allow for the stormwater containment, filtering, and also the slower dissipation of the runoff back into the wetlands or natural areas.”
Cement, on the other hand, tends to create a scouring action. “On seawalls, such as on the top inside of the seawall and the lower outside—the water side—you always have severe scouring actions that remove your materials,” Callahan says. “With this type of application, you’ve got a constant soft-armoring process that eliminates the scouring action that takes place. It contains filters and absorbs with the same strength that these hard-armoring processes react to.”
Callahan’s projects are engineered so that every third layer of the cell structure has a fabric containment, not allowing any migration outside of those areas.
“It also will handle any stress being applied on the wall,” says Callahan. “With anchoring, which is done with rebar or stakes, it totally locks in each area in encapsulated compartments.”
In another project in October 2003 at Santa Rosa Beach in Florida, a group of three- and four-story high-end vacation homes were bordered by a 6-foot solid-wall fence on one side, and on the front side, the property was well below the level of the road. Recent road improvements caused considerably more runoff to course down driveways and toward the houses than originally anticipated. In one case, the runoff scoured out the full length of the house.
Callahan’s company addressed the problem by using a 100% biodegradable coconut blanket as a liner, and then placed geocells on that, filling them with sand and continuing the process for four layers. Landscapers planted various dune-type plants. With all of the weather events that have since affected the area—including hurricanes—there has not been an inch of property loss, Callahan notes.
Callahan’s company addressed the nearby asphalt roadway as well, where there had been a 5-inch height variation between the road and gravel shoulders. “We put down porous pavers and filled them with number-89 stone that would collect the water as it came off the road and dissipate all those runoff energies,” he says.
In 2004, Callahan’s company was involved in a project on the Choctawhatchee Bay in the Niceville area. Residential property bordered wetlands and the bay. The original plan called for 10- to 12-foot-high retaining walls and plank walls, but Callahan’s company recommended the use of the cellular confinement system instead.
“It would allow them to expand the property out to the edge of the property line, whereas with that wall, they would have had to have an 8- to 10-foot buffer between the wall and the wetland area,” Callahan explains. “This way, they have full use of the area. Its original acceptance was based on the fact it added about 15 feet to their garage, parking, and turnaround apron, so they could back out safely, park their cars, and handle more cars. The house was set below the street level at a 35% incline, and the garage level was about 10 feet below the street.”
Callahan’s company used a 16- to 18-inch depth of #57 stone wrapped in 8-ounce nonwoven fabric to create a self-contained foundation system. They alternated each layer with a permanent coir turf reinforcement mat; the coir portion will biodegrade in three to four years, but the geogrid system will last indefinitely as a permanent stabilizing liner.
Lining every layer ensured there would be no problems for the homeowner or filtering processes, Callahan says. At higher levels, where strength wasn’t a consideration, Callahan’s company used a 4-ounce nonwoven fabric as a liner.
“That particular project started out as 40 feet long and five to six layers high, and in working with the US Army Corps of Engineers in the property delineation, it came out to be about 140 feet long and 15 to 18 layers high, so that it totally encapsulated the boundaries of the property, contained all of the structure around the pool, and terraced down into the wetlands and bay area so that they would have a surrounding containment of their property,” explains Callahan. “But it would handle all of the runoff from their pitched roofs that were metal without gutters and the runoff from the 30% slopes.”
When high waters come in from the bay, such as from hurricanes, the system can absorb and dissipate the wave action without damage to the system or loss of property.
“Works Like Concrete, But Better”
In San Juan Capistrano, CA, an open channel constructed in the 1960s that feeds into the San Juan Creek basin and eventually drains into the Pacific Ocean was severely eroding and undercutting the concrete sideslopes. During the 1997 to 1998 El Niño era, a large summer storm began to undermine the walls, causing major erosion.
“We were worried about a possible risk created to the neighborhoods,” says Joe Mankawich, associate engineer for the City of San Juan Capistrano. The city formed a list of objectives in rehabilitating the channel: Minimize erosion during precipitation events, increase aesthetics along the channel, minimize long-term maintenance problems, reduce chemical particulate matter from residential runoff, and minimize the costs of construction and maintenance. While examining the options, the city instituted temporary measures, such as repairs to the riprap and concrete portions of the channel walls.
But in considering more permanent measures, city officials became concerned about the use of riprap on the steep channel sides. Additionally, the channel flowed between two affluent neighborhoods, so aesthetics was a concern.
|
PHOTO: COLBOND |
| Concrete-lined channel before matrix was added. |
“The idea of a geofabric-lined channel came up,” Mankawich says. “Also, the city had recently started building a groundwater recovery plant, and we were looking at ways to recharge the basin, because now we were going to be using basin water for drinking water with the reverse-osmosis plant we were putting in. When you start thinking along those lines, you realize a concrete-lined channel will direct rainwater straight out to the ocean.” Any chance of the water percolating down to the groundwater would be lost.
City officials thought the channel presented a good opportunity to address the challenge with something that not only looked good but also functioned better to retain some of the water and percolate it down into the ground.
P&D Consultants, an environmental planning and engineering firm in Orange, CA, calculated the flow of water within the localized tributary that flows into the channel, which collects runoff from more than 300 acres in a valley with hillsides more than 200 feet high. Storm drains from existing development discharge directly into the channel. The water flows into the channel from a 10- by 4-foot concrete box culvert. The trapezoidal channel is 1,700 feet long and 4 feet deep, with a 10-foot bottom and sideslopes of 1.5:1. The estimated flow rate of the channel was 500 cubic feet per second, a flow that generates a shear force on the channel bottom of about 4.5 pounds per square foot for an extreme storm event.
P&D reviewed many options to address the problem, including riprap, Reno mattresses, concrete, and turf reinforcement mats. The firm, along with the city, decided a root reinforcement matrix that would not restrict vegetation growth—but that would meet the required flow conditions—would be the best solution. Enkamat R2M, a three-dimensional nylon root reinforcement matrix from Colbond Geosynthetics, was chosen. The matrix keeps the vegetation and soil from eroding during extreme hydraulic flow conditions. It does not unravel or lose its structural integrity during or after installation; therefore aquatic life within the basin would not be compromised from loose synthetic fibers floating downstream. Cost was another factor in the choice. Riprap was estimated to cost 15% to 20% more and concrete, 40% more.
During the 2000 installation, a mulch was applied on top of the Enkamat to ensure rapid germination, minimize seed displacement, and assist in the establishment of mature vegetation. Installation was completed in two weeks. In 25 rain events that followed, neither the channel nor the vegetation was damaged, even during peak rainfall and hydraulic activity. City officials were pleased that the project met federal and state requirements for the National Pollutant Discharge Elimination System Phase II and intend to use the material in future projects.
There have been a number of large storms since the installation, and city officials were worried that the native plants on the bottom of the water would be washed out in the first rain, but that didn’t happen.
“Now we have a beautifully lined channel and it has worked perfectly,” says Mankawich. “It works like a concrete-bottom channel, but it looks a lot better.”
Wally Ariand, president of ASW Construction in Edmonton, AB, Canada, a company that works in erosion control, is using geosynthetic materials to protect and line ditches, the edges of creeks, bridge piles, and building berms.
Ariand is an advocate of using geosynthetics and geogrids in erosion control projects. “When you look back 20 years ago and you see the products that are out there today, it’s making a big difference on protecting our waterways and our streams,” he says. “I think there should be more of it used.”
Ariand says his company is becoming increasingly driven by the requirements of the general contract for Alberta’s government; 75% of his company’s work is government, and the remaining is commercial. Applications that lend themselves to geosynthetics and geogrids include new subdivisions, new highway projects, and oilfield work, notes Ariand, who uses EMCO Ltd. products. Geogrids are also used in retaining walls, holding back the earth from moving as new structures are constructed.
“It stops the eroding, it’s going to protect streets, and it seems to be a good product for what it was designed to do. It is working,” Ariand says. “And that’s what most of the engineering firms are requiring.”
Ariand says there are no particular challenges involved in using geosynthetics and geogrids in terms of the installation. “It’s straightforward,” he says. “If you can read the blueprints, you’re going to have it made.”
Meanwhile, in Virginia Beach, VA, AGVIQ Environmental Services was called upon in late 2003 to assist in erosion control in a 2-acre wetland construction project. Dave Leadenham, program manager for AGVIQ, says that after much field investigation, the client noted that the existing clay onsite was not consistent throughout the proposed parcel of land for wetlands.
Many alternatives had been considered to address the erosion control issue, but cost and installation ease and time were major considerations. Quality Lining’s 40-mil LLDPE geomembrane liner was chosen. The product is widely used for wetland construction and landfill caps, two applications where earth fill will be placed on top of the installed geomembrane. Compared to HDPE, LLDPE features higher elongation properties, so it doesn’t break as easily, and a puncture resistance that is preferable when a subgrade is unstable or where compaction is not possible, Leadenham notes.
Quality Lining did the installation. The wetlands are in an hourglass shape that required many different lengths of the rolls of materials, and the sheets were deployed in a sequence, Leadenham says. The installation methods are essentially the same as used with all polyethylene geomembranes. Straight seams are typically achieved with a double-track wedge welder, and specialty seams, such as a tie-in to an existing liner or installation of pipe penetration “boots,” are made with an extrusion welding method. A quality check was performed.
“We probably had nearly 30 sheets and seams over every couple hundred foot lengths, so that was the most critical part,” Leadenham notes. “They did a visual [inspection] on the subgrade to make sure there were no sticks or twigs or anything poking out. We rely on our subcontractor’s quality check throughout the connection. All you need is one stick to come up through and potentially puncture the liner. The lining material itself is very susceptible, and in similar jobs like this, we’ve used other textured materials for landfill caps and covers.”
Leadenham says he has used different types of geomembrane materials in his 30 years in the environmental industry.
“What the state requires and what the client requires is something that allows the water in as it infiltrates wetlands and not just to seep out to let the wetlands dry out and all of the plants die,” he says. “So we had to have that permeable layer below. This particular liner material forms very well to the existing contours so if there were any dips or bends in the liner material, they smoothed over the top of it.”
AGVIQ coordinated efforts with Quality Lining by covering the liner with soil. The last step entailed flooding the wetland areas and plantings. Leadenham says the job was successful: “The wetlands are starting to grow, and that’s an important thing.”