synthetic turf system solves landfill erosion challenge

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Landfll Case Study

Synthetic Tur SystemSolves Landfll Erosion ChallengeAlexandria Hayes

A ter our yeArs As lAnd ill districtmanager or IESI Corp., Delaney Lewis wasdiscouraged. Although one o the Louisiana landfllsor which he was responsible exhibited ideal geology,the soil characteristics were not conducive to sideslope maintenance.

The soil o the LaSalle/Grant landfll was highly

erodible, exhibited a high plasticity index and hada natural pH o 4.0. Consequently, Lewis had spentevery spring repairing the slopes, amending thesoil with lime (4 tons per acre), seeding and hydromulching, only to watch his hard work end up atthe bottom o the landfll in sediment. He had triedeverything he knew how to do, yet had ailed at everyattempt to recti y the problem. It became evident thatsuccess would require an unconventional approach.

Lewis and IESI South Region Engineer MikeFriesen asked industry veteran, Juene Franklin o Houston engineering frm Riley, Park, Hayden andAssociates, Inc. i he knew o a solution. He directedthem to a recently patented product developed to

reduce greenhouse gas emissions and lower post-closure liabilities or states and landfll owners.Franklin thought the product, a synthetic tur system,could mitigate slope ailures such as those IESI hadbeen experiencing.

A New ApproachThe synthetic tur system, AgruAmerica’s

(Georgetown, SC) ClosureTur ™, consists o threemajor components: 1) two layers o woven geotextileswith tu ted UV-resistant polyethylene grass that islaid over,k 2) a 50 mil. LLDPE structured drainagegeomembrane and inflled with 3) sand(see Figure1). The geomembrane layer serves as the containmentliner atop the landfll’s immediate soil cover. Integral3.6mm studs on the top sur ace acilitate drainage,while integral 4.4mm spikes on the undersur aceprovide riction.

The tur ’s grass blades are interlocked with ¾ to1 inch o sand ballast, which, combined with theliner’s sur ace studs, provides su fcient inter ace

The LouisianaLaSalle/Grant Landfllsaves time and makesmoney with a synthetictur landfll cover.

Figure 1 The synthetic tur system’s tu ted geotextile layer, laid on top o a 50-mil LLDPE structured drainagegeomembrane, eliminates the top two eet o soil.Images courtesy o Mike Ayers, ClosureTur , LLC.

Figure 2 The synthetic tur system can handle rain all intensity o up to 4 inchesper hour.

WasteAdvantage Magazine October 2010 47

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riction that the structured geomembrane and tur layers do not requireanchoring or stability; they are anchored or termination purposes only at thetoe or on the outside o a perimeter swale, depending on the site design.

Rain all penetrates quickly through the sand and into the high tranmissivitydrain liner below. Hence, erosion energy resides in the structured geomembraneand not in the sand sur ace(see Figure 2, page 47) .

The ProjectThe LaSalle/Grant Landfll sits on 232 acres 50 miles northeast o Alexandria,LA. Opened in 1991, it is owned by the local LaSalle government and operatedby IESI. The landfll accepts 500 tons combined o municipal solid waste andindustrial waste per day. The landfll’s current working area has a 65-acreootprint and side slopes that range rom 3H:1V to 4H:1V.

The tur system’s 43-degree inter ace riction (more than a 3.0 sa ety actoragainst sliding ailure) looked promising as an e ective side slope stabilizer(see Figure 3) . Lewis and Friesen were intrigued. “I elt we didn’t have anyother options, so why not just try it,” said Lewis.

In October 2008, Friesen and Lewis oversaw the installation o the new tur system over 2.5 acres o landfll. The installation was ast and easy and it looked“just beauti ul,” says Lewis. But he wondered whether a system so simpleto implement could fx an intractable problem. However, the IESI team wasintrigued enough by the initial results that in February 2009, the company

moved on to phase two o theproject, covering another threeacres.

Surprising ResultsIt was only when Lewis and

his colleagues saw the cover inaction during spring runo thatthey became truly convincedo the tur ’s ability to providelong-term erosion control. In the

frst year ollowing installation,the covered area endured 73.5inches o rain all, including somein excess o 3 inches per hour.Three months a ter phase one wasinstalled, a tornado spinning across the ront o the landfll (about a quarter o a mile rom the tur cap) generated 70 mph shear winds. Then a levee situatedabove the tur area broke, loosing 5 acres o water to wash across the tur . Noneo these events a ected the tur . “The grass looks great; the sand didn’t moveand there was no erosion,” said Lewis.

Two recent tests support these feld results. Large-scale ASTM erosion testssubjected a 3:1 slope to the equivalent o 7 inches per hour o rain all withvirtually no erosion o infll. During wind tunnel tests, the material withstoodwinds in excess o 120 mph, without any subsur ace anchoring o the material.“We’d been killing ourselves working and reworking these slopes and now itappeared we had a really good answer,” said Lewis. “A ter we put the tur down,we didn’t have to do anything again.” The tur system required no mowing,reduced leachate, emitted no ugitive gas and stayed in place under extremeweather conditions.

Operational E fcienciesSpeed

It took a work crew about our days to install the frst 2.5 acres o tur system. Even in the wettest season, tur can be installed in just a ew clear days.

Figure 3 The synthetic tur system’s high riction coe fcient makes it ideally suited or step slopes.

Figure 4

The synthetic tur system’s grass, tested under extreme conditions, is projected to retain nearlythree times the required strength over its 50-year li etime.

s h t s m s v la f e cha g

48 WasteAdvantage Magazine October 2010

The LaSalle/Grant Landfll management team chose a synthetic tur system to controlintractable erosion problems.

A work crew covered the frst 2.5 acres in our days.

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synthetic turf system solves landfill erosion challenge

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