DSWMA SOUTH LANDFILL FINAL COVER CONSTRUCTION Engineering and - - PowerPoint PPT Presentation

DSWMA SOUTH LANDFILL FINAL COVER CONSTRUCTION

Engineering and Environmental Solutions, LLC Blaine Litteral

CLOSURE OVERVIEW

§Final cover was completed in three phases. §Phase I of closure was completed in 1997 & 1998 closed 6.59 acres. §Phase II was completed in 2013 closing 11.05 acres. §Phase III was completed in 2016 closing the final 5.27 acres of the south landfill. §Active gas collection was installed in 3 phases in 1997, 2012 and 2016.

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South Landfill Map

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CLOSURE OVERVIEW

§Phase I included PVC cover FML over areas lined with single PVC liner. §Phase II and III included a composite cover system of LLDPE FML and GCL materials over areas lined with a double composite liner system that included GCL, HDPE FML, and drainage composite components.

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SETTLEMENT ISSUES IN DESIGN

§Observed significant settlement of final cover between construction of each phase. §Required redesign of cover grades resulting in loss of airspace. §Expect field adjustments at the tie in to older cover areas.

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Adjustment between 2013 and 2016 final cover.

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LIMITTING AIRSPACE LOSS DUE TO SETTLEMENT

§Use of temporary covers to increase time before closure to allow refilling settled areas. §Avoid terminated closure phase perpendicular to the slope and avoid closure boundary that runs across slope when possible.

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The flow from the secondary collection system began exceeding regulatory limits following construction of the second phase of final cover.

SECONDARY FLOW EXCEEDANCES

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INVESTIGATION OF SOURCES

§Analytical testing showed liquid was representative of storm water. §Investigation into the source identified two suspected points of entry for the storm water.

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Leakage around leachate pump station and poor drainage combined with flaws in primary to secondary welds at site perimeter.

TWO CAUSES IDENTIFIED BY THE INVESTIGATION

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LEAKAGE AT PUMP HOUSE

§It was discovered that storm water was building up on top of the final cover/exposed primary liner. §Attachment of liner system to pump house provided liquid entry to secondary.

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Primary liner connection at building corner.

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Leakage around leachate pump station was addressed by sealing apparent openings, installing a rain flap to direct storm water away from the building liner connection and providing additional drainage.

PUMP HOUSE LEAK CORRECTIVE ACTION

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PERIMETER ANCHOR TRENCH

§Storm water was also found to be building up within the perimeter anchor trench . §Flaws in the primary liner within the trench were believed to be a source of water to the secondary collection system. §Road at perimeter of site prevents drainage away from lined area.

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Recommended Cover - Primary - Secondary Liner connection at perimeter.

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A rain flap and toe drain was installed

• ver the perimeter welds to prevent

storm water from collecting over the perimeter anchor trench.

PREVENT STORM WATER ACCUMILATION IN THE COVER

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OTHER CONSIDERATIONS

§Pump houses should be set sufficiently away from liner system so liner does not need to be connected to the

• building. Standard side slope riser pumping system may

be preferred. §Provide space between landfill liner system and perimeter road to allow storm water to be drained away from landfill.

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ANY QUESTIONS?

Blaine Litteral - 616.566.4609 blaine.litteral@goeeesolutions.com Engineering & Environmental Solutions, LLC www.goEESolutions.com