Emergency Response for Landfill Gas

Mitigation and Full-Scale Remedy Design

Authors: Omer J. Uppal, Neil Rivers, Stewart H. Abrams, Sachin Sharma,

and Matthew Ambrusch

Presentation Outline

Site Conceptual Model

Rapid Emergency Response

Pilot Testing

Temporary Mitigation System

Full-Scale Design

Conclusions

LANDFILL

VILLAGE

Site Layout

Formerly closed sanitary landfill

Site Conceptual Model

Former passive gas collection system

Ineffective vapor capture due to water in pipes

Passive SSDS’s in nearby residences

High Methane Detections

Colorless/Odorless

5.00% by volume CH4 = 100% LEL

1.25% by volume CH4 = 25% LEL

Historic Results 2004-2008

Rapid Response – April 2011

Baseline methane survey – April 2011

Temporary activation of existing venting system – April 2011

Pilot testing – May 2011

Pilot Test Results May 2011

Pilot Testing – May 2011

Temporary Mitigation System – April 2011 through Current System extracts landfill gas from the shallow trenches and two deep SVE wells.

Within 6 weeks, methane concentrations in the shallow monitoring points declined from 74% methane by volume to ND

Consistent decrease in methane gas concentration in blower discharge

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

Feb-11 Sep-11 Apr-12 Oct-12 May-13 Nov-13 Jun-14

Met

han

e C

on

cen

trat

ion

(%

by

Vo

lum

e)

Time

Full-Scale Design Objectives

Prevent landfill gas migration from landfill towards residential

properties through both the shallow and deep pathways

Utilize as much of existing system as possible

Utilize passive and active soil gas venting and treatment systems to

increase effectiveness

Create well network for proper monitoring

Design Basis

Shallow Fine-Medium Sands

Deep Fine Sands

Fill

LG Migration Pathways Site Lithology

Pneumatic Modeling

Why Modeling?

Simulate air flow field in subsurface

Determine design parameters

Approach - MDFIT

Outputs

Ki, ROI, FD , PV exchanges

Benefits

More cost-effective design

Valuable tool for SVE, VI Mitigation & Air Sparging design

Full-Scale Design

Active LG Venting Component

Existing LF gas venting trench

Thermal flare for off-gas treatment (optional)

10 Passive venting wells

Barrier SVE Component (contingency)

8 Paired SVE well locations

3 Deep vapor points

FULL-SCALE SYSTEM DESIGN

Proposed Methane

Mitigation System

Active LG Venting Barrier

SVE

VILLAGE

LANDFILL

SHOPPING CENTER / LANDFILL

Passive Vent Points

Existing Vapor Collection Trench (Active LG Venting) System Shed

PROPOSED METHANE MITIGATION SYSTEM

N

Legend: PASSIVE VENT PTS SYSTEM SHED EXISTING SYSTEM

FULL-SCALE SYSTEM DESIGN

Proposed Methane

Mitigation System

Active LG Venting Barrier

SVE

VILLAGE

LANDFILL

SHOPPING CENTER / LANDFILL

Passive Vent Points

Existing Vapor Collection Trench (Active LG Venting)

Barrier SVE Wells SVE 1 & 2 (Existing)

System Shed

Deep VPs

PROPOSED METHANE MITIGATION SYSTEM

N

Legend: PASSIVE VENT PTS SYSTEM SHED EXISTING SYSTEM SVE WELLS DEEP VPs

Beats the Alternative

Cost-Effective Alternative to a Barrier Trench

Substantial Cost Savings: ~ $3 Million

Elimination of slope stability and trench construction issues

Conclusions

RAPID ACTION (in less than one week)

Mobilized, installed, and activated temporary gas collection

system

Protected dozens of private homes

System continues to effectively operate

Innovative Design Strategy Benefits

Questions?