overliner or landfill mining?

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Overliner or Landfill Mining?

Best Approach for a Landfill Expansion for an Unlined Landfill

Prentiss A. Shaw, P.E. Martin L. Ryan, P.E., P.P.

Patrick M. Bell, P.E.

Global Waste Symp: June 25, 2014

© 2014 Cornerstone. All rights reserved. | Confidential 2

Potential of Expanding Unlined Landfills

400 MILLON CUBIC YARDS OF AIRSPACE WITHOUT A SINGLE FACILITY EXPANDING FROM CURRENTLY

PERMITTED AREA


Introduction

Why Redevelop an Unlined Landfill?

• Capture Available Airspace w/o Lateral Expansion

Two approaches:

1. Overliner: Install containment system above waste and possibly overfill connecting adjacent cells (piggyback)

2. Landfill Mining: Excavate waste and install traditional baseliner system on soil


Introduction

How do you decide which approach to pursue?

Five Key Decision Making Criteria:

1. Site Life Remaining

2. Groundwater Compliance

3. Existing Grades

4. Age of Waste

5. Economics


Challenges for Overliner & Landfill Mining

• Comfort Level of Digging into Old Waste

• Unique Design Elements

• Unique Construction Elements

© 2014 Cornerstone. All rights reserved. | Confidential

Gaining that Comfort Level

Conduct an Extensive Test Pit Program to Determine Waste Characterization & Delineation of Limits

1. Waste Disruption Permit

2. Numerous test pits at varying depths

3. Testing/Monitoring - BMP, Exposure (O2/LEL/H2S), Composition

4. Visual – decomposition, soil percentage, odor, moisture, perched conditions


Design – Overliner

• Differential Settlement

• Cut-Fill Analysis

• Subgrade Gas

• Liner Tie-ins

• Infrastructure Access /Relocate


Design – Landfill Mining

• Exposed Waste Slopes

• Bottom of waste uncertainty

More traditional baseliner design

• Liner Tie-ins

• Infrastructure Access /Relocate


Construction – Overliner

• Varying Subgrade Conditions

• Defined Waste Excavation – Not Mass Excavation

Soil, Alt Fill, or Waste

Waste


• Excavation & Processing Rate

Construction – Landfill Mining

• Screening Operations

• The “Unknown”

• Run-on Controls

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=mprpLwtdejAD2M&tbnid=YQh4VnzEX2o78M:&ved=0CAYQjRw&url=http://waste360.com/Landfill_Management/mining-landfill-space-201002&ei=X9wqU4vlH4602AW-wYBI&bvm=bv.62922401,d.b2I&psig=AFQjCNFh6Lamt8gBMzpdTkyDZiYWg3zQtw&ust=1395404254643725


OCEAN COUNTY LANDFILL CASE STUDY


Introduction

• Ocean County Landfill (OCLF) is a privately owned and operated sanitary landfill located in Manchester Township, New Jersey, approximately 50 miles east of Philadelphia, and 70 miles south of New York City

• The landfill serves the 33 municipalities comprising the County of Ocean

• Area of 915 square miles

• Population of 580,000


Early Analysis of Landfill Reutilization

• Height restrictions of 175*No vertical exp.

• Wetlands & Neighbors*No Lateral exp.

• Focus for expansion then shifted to a 60-acre parcel known as the Existing Landfill.


Test Pit Program

• Waste Disruption Permit – 2006

• Test Pit Program 2007

• Goal: Waste characterization & Cap soil delineation

Key Takeaways:

Biochemical Methane Potential (BMP) testing concludes that waste was largely decomposed

Cover soils above and below the liner were thicker than anticipated

Large amount of daily cover soil used during waste placement

No perched leachate encountered


Overliner Design

DESIGN ELEMENTS:

• Steeper slopes of leachate collection lines to ensure positive drainage of the overliner.

• A rather complex subgrade design with leachate laterals draining the subcells south to north, and west to east in areas.

• Installation of subgrade gas collectors in the Original Landfill waste remaining in place.

• A construction staging plan with a goal of balancing and timing the cuts to fills to the greatest extent possible.

Pursuing overliner design - Sustainable Landfill Project (SLP)

Reasons for that decision:

• Most efficient way to redevelop without large scale waste disruption

• 6,000,000 CY of additional airspace

• Still unknowns about waste mass


A Change of Direction…?

Acquisition and excavation of adjacent “orphaned” landfill

• Manchester Township Landfill

• 600,000 CY of material excavated from 1/2009 – 4/2010

Key Takeaways:

Odor from the excavation activities was negligible.

Extensive air monitoring revealed no health and safety concerns.

Leachate and stormwater issues were easily managed by proper construction staging.

No extensive nuisance control measures were necessary for issues such as vectors, dust or litter.

A large quantity of cover soil was used during the landfilling operations, some of which was able to be recovered for reuse at OCLF.


Back to the Drawing Board: Landfill Mining Considered

Reasons for that decision:

• Comfort level achieved• Overliner needed over 1

million CY of fill material• Ability to change Operational

Sequence• Need for daily cover

Results:

• Additional 1,250,000 CY of waste to be placed in the same envelope of airspace

• 1.5 years of additional site life• 2,000,000 CY of cover soil anticipated

to be generated• The construction cost of an overliner at

Ocean County Landfill is $16.51 per cubic yard while the construction cost of LF mining is $13.99 per cubic yard.

• Mitigate potential liability of an unlined landfill

• More typical cell subgrade design with standard slopes


Status of SLP Redevelopment

The Permitting Process:

• Pre-Application Meeting with NJDEP – 6/2012

• Waste Disruption Permit required for excavation

• Minor Solid Waste Facility Permit Mod. required

• Waste Disruption Permit approved by NJDEP 3/2013

• Solid Waste Permit Mod. approved by NJDEP 11/2013


Status of SLP Redevelopment (cont’d)

OCLF and Cornerstone are currently finalizing construction plans for Phase 1 of the Waste Excavation Project, which entails excavation and screening of approximately 1,500,000 CY, and incorporating temporary capping of exposed slopes, interim gas collection, and necessary stormwater controls.

• OCLF has also filed a permit modification to the facility’s Title V Air Operating Permit, to authorize the large scale screening operation that will occur during the waste excavation activities.

• It is anticipated that excavation activities will commence in Summer 2014, with the first phase of SLP baseliner construction projected for 2020.


THE DECISION PROCESS


Key Evaluation Criteria

Site Life Remaining

GW Compliance

Existing Grades

Age of Waste

Economics

Landfill Mining Overliner

Decision Process


Remaining Site Life

Greater than 5 YRS

Landfill Mining

Less than 5 YRS

Overliner


Groundwater Monitoring Compliance

Poor Compliance Record

Landfill Mining

Good Compliance Record

Overliner Landfill Mining


Existing Grading of Unlined Cell

Relatively Flat

Landfill Mining

Greater than 10 Percent

Overliner


Age of Existing Waste

Greater Than 20 Years Less Than 20 Years

Landfill MiningOverliner


Economics

• Revenue Additional Airspace• Value Recovered Soil• Value Recyclables Recovered• Avoided Costs• Cost per CY of Airspace Gained

Landfill Mining

• Total Cost of Construction

Overliner


OCLF Decision Process

Greater than 5 YRS

Landfill Mining

Good Compliance Record

Overliner

Landfill Mining

Relatively Flat

Landfill Mining

Greater Than 20 Years

Landfill Mining

• Revenue Additional Airspace• Value Recovered Soil• Avoided Costs• Cost per CY of Airspace Gained

Landfill Mining

Economics

Site Life GW Compliance Grades

Age of Waste


Factors that could push an owner towards an Overliner

• Need airspace now

• “Dirt-rich” site

• Conducive grading

• Contractual issues for large projects

• Regulatory/Permitting issues (cap/GCCS/air)

• High BMP

• Stability concerns

• Financial considerations and results of cost/benefit analysis


Factors that could push an owner towards LF Mining

• Positive site life outlook

• “Dirt-poor” site

• GW issues

• Overliner differential settlement

• Use of own forces (excavation/screening)

• Financial considerations and results of cost/benefit analysis


THANK YOU! You can contact me:

Prentiss A. Shaw, P.E.Cornerstone Environmental Group, LLC

[email protected]

Phone: (845) 695-0202

mailto:[email protected]

overliner or landfill mining?

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