Extreme Airport Construction
In most cases, it would be the rare day at work for employees to have to rappel down steep slopes to get to their job site. But that is exactly what Jerry Kallam, vice president of business and development at L&M Supply Co., encountered when he visited the Ecuador airport project in Quito. In addition to the employees, the company’s products and tools had to be moved the same way. But the challenges didn’t stop there. Winds surging at 60-75 miles per hour across the slopes picked up the fine granite-like soil particles, and sand blasted everything it came in contact with.
“The soil is a fine volcanic consistency that has the hardness of limestone and, in some cases, is hard as granite,”
Kallam explains. “This dirt was flying all around us. At times, we had to cover our heads with anything we could find, as it was like being sand blasted. Without glasses, you could not open your eyes for even a second.”
Quito is Ecuador’s capital city. In 1960, when the Mariscal Sucre Airport was first established, Quito had a population of approximately 350,000 residents. Since that time, the population has risen to 2.2 million, and flights into and out of Quito and connecting cities have risen as well. The airport begins servicing flights at 5:45 a.m. and continues until 2 a.m. Areas that used to be agricultural cornfields have grown to include many sleepless residents. And like other airports similar to Mariscal Sucre, geographical limitations leave slight room for error. In 1984, Quito experienced one of its worst airport accidents-in which 49 people lost their lives. Since then, the airport has been moving to a new location 12 miles northeast of the city along the new Collas Road. The new airstrip is nearly 3,300 feet longer than the previous 13,450 feet and the airport will cover nearly 6 square miles.
“On July 31, 2014, this part of the project was inaugurated-the Collas Road, leading to Mariscal Sucre International Airport. This work, carried out by the Ministry of Transport and Public Works, will benefit more than 2 million users, reducing travel time to the airport,” says Kallam. “With this new option, passengers save time and fuel. In addition, the Collas route will help the flower sector and exporters, since the transfer of goods to the airport will be easier and faster.”
The Collas Road project, with a budget of $198 million, will provide travelers a 11.7-kilometer road with two lanes in each direction and will include a bridge over the Guayllabamba River. It is expected that more than 5,000 vehicles will travel this route each day.
“This project generated movement of about 20 million cubic meters of earth,” says Kallam, “enough to fill 17 times the amount of the Atahualpa Olympic Stadium.”
To stabilize steep slopes in the cut-out portions of the project, says Kallam, crews used a high-performance turf reinforcement mat (HP-TRM) over approximately one million square yards. The HP-TRM, from US Erosion Control Products, is used for long-term control in areas with demanding and extreme conditions. Constructed from a high-strength woven polypropylene monofilament fiber, it provides a three dimensional (3D) pyramid matrix and creates areas for root and soil interlocking beneath. The HP-TRM also helps to stabilize erodible soils and enhance vegetation growth in difficult to establish areas.
“It was used on the cut slopes of the new Collas Road leading to the airport,” he says. “The road is located at the base of the Andes Mountains, at an elevation of 10,000 feet above sea level.”
Kallam explains the installation process for the permanent turf reinforcement mats. “The HP-TRM was used in lieu of a bi-axial geogrid, because it gave more UV protection and more soil loss protection, and it was aesthetically appealing in the color green versus the black of the geogrid.”
The HP-TRM was installed over 3D coconut fiber matting on the steep slopes. The terraces going up and down the sharp cutouts along the Collas Road were about 120 feet apart, with 12-foot plateaus between each. Workers had to scale a total of 1,500 feet while moving equipment on the 1:1 to 1.75:1 gradients.
“And all of the materials had to be hand-placed by rappelling,” Kallam emphasizes.
The workers at Quito were local residents knowledgeable of the terrain. They rappelled down to their work sites using ½-inch ropes tied to a 2-inch-diameter stake that was driven 4-5 feet into the hard volcanic soil. On some days, they brought wire baskets to tie to the ropes to transport materials, but Kallam said he eventually decided against this as a means of transporting anything heavy.
“It was a situation where the “˜basket’ could have ended up being a “˜casket’ . . . a scary situation,” he says. “They would rappel down onto the slope carrying a 25-pound jackhammer and tools to install the percussion earth anchors.”
As if the steep grades weren’t challenge enough, getting equipment into Ecuador proved difficult as well. But another problem Kallam grappled with was aesthetics. The owner/contractor on the site was going to use a geogrid product for slope stability and just leave it at that.
“I told him, “˜You’re going to use this geogrid and it will end up being a real eyesore,'” says Kallam. “About two miles away, he had already installed it, and sure enough, it was a big black spot out there. I had to show him some green pictures. So, yes, aesthetics was a big challenge there.”
On one of the 1.25:1 degree slopes, Kallam found his end point. About half a mile from the new bridge site, he says, he simply could go no farther. “This was so steep. I sat down and did not venture any further forward. I was afraid of the 400-foot drop below.”
However, with approximately 40 work crews, the Collas Road section of the project was completed in about 700 work days.
L&M Supply Company is headquartered in Willacoochee, a small town in south-central Georgia. It has manufacturing plants in Douglas, Nashville, and Pearson, GA, as well as distribution in Colorado and Indiana. L&M Supply has been in the erosion control industry for 35 years. It was founded by two pioneers in the trade, Quincy and Quentin McMillan, who began by taking geosynthetic products that were headed to the landfills and converting them into landscape fabrics.
“Repurposing and converting is nothing new to our company; protecting the environment with geosynthetics is a mission for us,” says Kallam. “We currently produce wire sod staples, silt fence, filter bags, landscape fabrics, and a full line of erosion control blankets and wattles. We manufacture our erosion control products through our US Erosion Control Products company.”
What to Do With High-Volume Traffic
Pennsylvania highway US 202 includes a 59-mile stretch that connects New Jersey at the north and Delaware at the southernmost point. It’s a crucial link to business and economy in the tri-state area, as well as being a major commuter route in the region. Varying in size from a two-lane road to a major four-lane expressway, it is travelled by up to 105,000 people each day.
A Pennsylvania Department of Transportation (PennDOT) report concludes, “Some of the fastest growing areas in the Greater Philadelphia Region are located along US 202. Many of these areas have experienced rapid residential, commercial, and light industrial growth, the result of acres of undeveloped land and the corridor’s reputation as a high-tech growth area.”
While addressing this growth and acknowledging the importance of US 202, joint public and private partnerships assembled to develop options to relieve congestion and meet existing and future travel demands. Admittedly, there was a huge need to increase the highway’s capacity. The project was divided into eight sections, including a segment know as Section 320. In addition to major road construction and the addition of an Intelligent Transportation System (ITS), Section 320 needed bridges reconstructed, retaining walls, improvements to the stormwater drainage systems, and other additions.
RAM-T Corp. worked closely with Richard E. Pierson Construction Company, the lead contractor on the “Congestion Mitigation Program on U.S. 202 Sect. 320″ in Chester County. RAM-T’s part of the massive highway project was basin stabilization and stormwater mitigation at East Whiteland Township. RAM-T Corp. of Bernville, PA, is a leading manufacturer and installer of erosion control products, and with owner/president Deborah Turner leads the way as Pennsylvania’s largest woman-owned business.
Christine Rovner, purchasing agent with RAM-T Corp., explains that the stormwater mitigation basins along Section 320 incorporate many erosion and sediment control best management practices (BMPs), each used for different purposes. “The basin bottoms were stabilized with seed and fiber mulch so that the inlets and culverts do not fill with the typically used straw mulch, causing clogs,” says Rovner. “The side slopes were stabilized with the designated seed and S1 matting, and the emergency spillways were installed with seed and P2 matting to ensure permanent, heavy stabilization.”
Working with the erosion and sediment control plans designed by Michael Baker Jr. Inc. and landscaping plans prepared by Menke & Menke LLC, both of Horsham, PA, the crews from RAM-T Corp. began by protecting the mitigation areas first with super silt fence and compost filter socks.
“These were PennDOT mitigation projects,” explains Don Holladay, RAM-T Corp. site superintendent. “These sites are for stormwater control in particular. And the plants will act like a rain garden.”
Using a large Finn HydroSeeder, crews hydraulically applied the bonded fiber matrix mixed with, primarily, a Formula L seed mixture from Seedway Seeds. Formula L seed mix incorporates hard red fescue (Festuca longifolia), creeping red fescue (Festuca rubra), and annual ryegrass (Lolium multiflorum) and is seeded at a rate of 24.0 pounds per 1,000 square yards, unless otherwise specified. It’s all in the specs,
Holladay notes. For instance, at some other highway projects, crews can dry-seed the mixtures. However, for the Section 320 area, the engineers had specified that seed was to be applied with the fiber mulch mixture.
“It was mixed with rye seed, which gives instant germination so you get a good plant stand,” he says. “The mulch keeps it all warm and the rye comes up right away. Then the other seeds get a chance to germinate.”
Annual ryegrass, like that used in the mix applied at Section 320, is considered very ecofriendly. It’s nonaggressive, provides vigorous growth, and provides soil stability with its root system. It typically germinates in five to 14 days. It offers some nematode control and will die off after a year cycle in most climates. At Oregon State University Hyslop Farms, where grass seed is grown and studied in the Willamette Valley, the grass reaches maturity, then lodges and goes to seed. The lodging, or lying down of the plant stand, is what allows other seeds to have protection to germinate.
In seed mixes like the Formula B that was used elsewhere along the US 202 corridor, perennial ryegrass (Lolium multiflorum) usually takes longer to germinate but is a more
permanent choice because it handles the cold and warm extremes better than annual ryegrass. With both ryegrasses, planting is most successful when soil temperatures are between 50 and 65°F, which usually correlates with 60-75°F. air temperature. The nature of ryegrasses allows the seeds to germinate with less soil contact, which makes them a good selection for roadways and conservation areas, but because the mixtures usually include the one or more fescue grasses, soil contact and good seedbed preparation is critical. For this, good single- or double-net matting helps hold soil and seed contact through germination and plant stand.
To ensure protection on the lower basin bottoms, those with 3:1 slopes, RAM-T crews installed ECS-1 single-net straw blankets, and on the side slopes along the highway with 2:1 slopes, they used ECS-2 double-net straw blankets, both manufactured by East Coast Erosion Blankets of Bernville, PA. Other matting used included ECP-2, a TRM, and jute matting for erosion control.
“Flexterra was used above a roadside retaining wall in place of the originally specified matting,” says Ashley Kreutzer, vice president with RAM-T Corp. “This substitute was made to ensure slope stabilization in an area that was too difficult to access by hand. The use of the HydroSeeder and a man-lift allowed us to safely stabilize the slope with a matting equivalent.”
Flexterra is a high-performance flexible growth medium (HP-FGM) from Profile Products that bonds immediately to soil, even on severe slopes. Because it gives increased sheet flow resistance, turbidity is reduced, and soil loss is minimized, thereby giving seeds a good start.
“The sites were then planted with riparian plantings to help with post-construction stormwater control,” says Kreutzer. “With the removal of existing earth and the addition of nonpervious roadways, more plants were needed to control the additional water runoff on the project.”
Woody plants native to Pennsylvania, Canada, and the eastern United States were planted in riparian zones; they included dogwood (Cornus sp.), arrowwood (Viburnum sp.), elderberry (Sambucus sp.) and alder (Alnus sp.), says Holladay. “Some of the areas got live stakes. When we do that, mostly it’s dogwood and the live stakes get driven in the back on the slopes. They take hold really well.”
Construction on the US 202 project is estimated to continue through 2016. When finished, it will include a 2-mile two-lane collector-distribution road, two new bridges, new sign structures, retaining walls, sound barrier walls, improved stormwater drainage systems, and
additions to the ITS that allow traffic notices and estimated distances and times to be displayed to travelers.
The major bid for this portion of the project was awarded to Richard E. Pierson Construction Company Inc. of Woodstown, NJ; the $105,415,093 budget included 80% federal and 20% state funding. The overall Section 320 project also included widening 4 miles of highway to three lanes in each direction, installing glare screen barriers to separate the northbound and southbound lanes, and rehabilitation of the bridges that crossed Valley Creek and Valley Road.
Timing Is Everything
The timing, along with a little help from Mother Nature, helped quickly stabilize a critical slope area in Vaughan, ON, in August 2011. After a major storm battered the area, sheet runoff from one of the major highways, Rutherford Road just east of Highway 27, was creating gullies and rill erosion problems. Previously installed riprap was not enough to slow the volume or velocity of water gushing down the embankment.
“With a slope of approximately 2:1, erosion protection measures were required,” explains J. J. Breede with Terrafix Geosynthetics Inc. With the use of a backhoe, the contractor, Maram Building Corp., prepared the subgrade.
“Panels of 200-millimeter-deep Terraweb, which are 2.54 meters wide by 6.5 meters long, were stretched out and pinned down with 450-millimeter steel J-Pins. After they were laid in place, the cells were filled with topsoil and hydroseeded, followed by coverage with C200 double-net coconut blankets for additional erosion protection. Within a few days, vegetation had taken place, coalescing with the surrounding marsh area,” says Breede.
Terrafix coir mats are made of coconut husk fiber and are completely biodegradable. Because the mats are more flexible than matting made from bristle coir fiber, they have better interface with the soil surface, thus encouraging seed germination. Additionally, the fiber can absorb water, so it acts much like mulch on soil surfaces or as a “wick” in the soil layer. Other uses of the coir mats and logs include slope and channel stabilization, stream and riverbank stabilization, wetland construction, dams, and detention ponds.
Coir mats, with their high tensile strength and extreme durability, are suitable for the most severe erosion control problems and can have a lifespan of three to six years, allowing for vegetation to become fully established. Woody or shrubby plants grow readily through the open mesh construction in the mats, while receiving nutrients from the biodegradation of the materials. All of these features help to accelerate seed germination and the development of riparian habitat.
Good uniform soil coverage is one of the keys to having an effective erosion control project that prevents water from forming rills, such as was originally the problem at the Vaughan site. After the proper erosion control BMPs were installed, says Breede, the difference was easy to see once the grass and native seed was established. Breede added that such good germination was also due to planting in spring and then getting a good, wet summer.