Landfill LeachateCollection Pipe Design

Solid Waste Association of North AmericaNorth Carolina ChapterSpring ConferenceApril 25-28, 2016

Ali Khatami, Ph.D., P.E.SCS Engineers

Discussions

• Clogging at Leachate Collection Pipes• Traditional Design of Leachate Collection

Pipes• Innovative Design of Leachate Collection

Pipes• Construction Details

Clogging Issue

• Large quantities of leachate passing through a small area of geotextile potentially causes clogging

• Clogging reduces flow of leachate through geotextile

• Clogging of geotextile at leachate collection pipe potentially impedes free flow of leachate into the pipe

Rule of Transmissivities

Leachate must always flow from a transmissive medium into another medium with equal or greater transmissivity

Transmissivity Value Order

Waste < Sand < Geotextile < Geonet < Gravel < Pipe

Flow of water from left medium to right medium would be an ideal arrangement

Examples:Geotextile → Geotextile (√)Geotextile → Geonet (√)Geonet → Geotextile (X)Geotextile → Gravel (√)Geotextile → Sand (X)

Traditional Design of LeachateCollection Pipes

Leachate Flow Path in Traditional Design

• from waste to sand layer (√)• from sand layer to upper geotextile of geocomposite (√)• from upper geotextile to geonet of geocomposite (√)• from geonet to upper geotextile of geocomposite (X)• from upper geotextile of geocomposite to geotextile

around gravel (√)• from geotextile to gravel (√)• from gravel to pipe (√)

Does Not Satisfy the “Rule of Transmissivities”

Solution

Eliminate geotextile

Innovative Design of LeachateCollection Pipes

Leachate Flow Path in Innovative Design

• from waste to sand layer (√)• from sand layer to upper geotextile of

geocomposite (√)• from upper geotextile to geonet of

geocomposite (√)• from geonet to gravel (√)• from gravel to pipe (√)

Follows the “Rule of Transmissivities”

Geomembrane at Base and throughLCS Trench

Geocomposite Drainage LayerTerminated at LCS Trench

Geotextile Cushion in LCS Trench

Geonet Cushion in LCS Trench

Geocomposite Tied to Geonet

Gravel above Geonet for Pipe Support

Pipe Placed above Gravel

Pipe in LCS Trench

Gravel Placement in Progress

Pipe and Gravel In-place

Geotextile Pulled Over Gravel

Geotextile Sewn to Geocomposite

Geotextile Installation

Geotextile In-place and Sewn

Sand Scooped Over Geotextile

Lower Portion of Completed Cell

Middle Portion of Completed Cell

Upper Portion of Completed Cell

Thank You for Your Time