Long-Term Stewardship of Three Evapotranspirative Covers, 15 years - PowerPoint PPT Presentation

August 20 – 23, 2018 Grand Junction, Colorado 2018 Long-Term Stewardship Conference Long-Term Stewardship of Three Evapotranspirative Covers, 15 years Sue Collins, Long-Term Stewardship Program Lead Sandia National Laboratories Track 2.2: Understanding the Post-Closure Changes of Engineered Disposal Cell Covers, Part 1 Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nucl ear Security Administration under contract DE-NA0003525.

Other Contributors Michael M. Mitchell Robert Ziock GRAM, Inc. Sandia National Laboratories Dedication: To Mike and Robert who have remained with all 3 covers since design and construction To their invaluable knowledge and earnest stewardship Acknowledgement: NNSA 533: Richard Dasher and Tom Longo (retired) NNSA Sandia Field Office: Steve Black and David Rast Cover Tour Video SAND2018-8211V by John Sandlin, Sandia National Laboratories Environmental Geographic Information System Intern Presentation SAND2018-6824C 2018 LTS Conference 2

Cover Tour 3

ET Cover Maintenance since 2003 TIM IMELIN INE FOR 3 EVAPO-TRANSPIR IRATIV IVE COVERS AT SANDIA IA NATIONAL LABORATORIES CWL Backfill MWL Subgrade MWL ET Cover Phase 2 Construction Construction CWL Vapor CWL Backfill CWL ET Cover MWL Inspection Extraction Phase 1 Construction and Maintenance 1997 1997 1998 1998 1999 1999 2000 2000 2001 2001 2002 2002 2003 2003 2004 2004 2005 2005 2006 2006 2007 2007 2008 2008 2009 2009 2010 2010 2011 2011 2012 2012 2013 2013 2014 2014 2015 2015 2016 2016 2017 2017 2018 2018 CWL Landfill CWL Inspection Excavation and Maintenance CAMU ET CAMU Excavate Treated CWL Waste Soils CAMU Inspection Cover Construction the Fill Area Into CAMU and Maintenance Corrective Action Management Unit (CAMU) Chemical Waste Landfill (CWL) Mixed Waste Landfill (MWL)  2003 Corrective Action Management Unit (CAMU)  2005 Chemical Waste Landfill (CWL)  2009 Mixed Waste Landfill (MWL)  Size Range: 2.2 – 4.1 acres

ET Cover Layers Custom Seed Mix Top Soil: 0.7-1.5ft Native Soil: 2.5 - 3ft Local Soils from <1.5 miles away Soils Prepared/Screened/Tested on Site ET Design: ~9x ABQ’s Average Annual Precipitation Bio-intrusion Filter Sand Backfill of Layer Pea Gravel Clean Fill 1.25 ft 0.7 ft Soil Replaceable Subgrade Bedding Sand Soil Original Treated Soils unexcavated Stored in Landfill Lined RCRA C Biointrustion Crushed Rock 1 – 6 inch, no organics or friable fragments MWL CAMU CWL

ET Cover Construction at Chemical Waste Landfill 6

Seed Mix Changes and Gravel Mulch Seeds for CWL Mix Rate Indian Rice Grass 39% 7.8 lbs/acre Corrective Action Galleta 19.5% 3.9 lbs/acre Management Blue Grama Grass 29.5% 5.9 lbs/acre Unit, 2005 Sand Dropseed 6% 1.2 lbs/acre Alkai Sacaton 6% 1.2 lbs/acre Minor seed mix adjustments for MWL and Increased the Seed Rate. 7

Chemical Waste Landfill Seed mix Mulching, Crimping Seeding Prevent Wind Erosion 8

Achieve Vegetation Specification within 5 years Supplemental Watering was needed for 2 of the 3 covers Mixed Waste Landfill 9

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1-2 years Heavy Weed Coverage 11 Mixed Waste Landfill

Inspection and Maintenance Permits Requirements  Quarterly Inspections  Maintenance within 60 calendar days  Maintenance Summary Reports Operations  Sandia LTS staff perform Inspections  Maintenance Subcontract  Lesson Learned: Standard ‘Facilities’ services and practices, not a fit  Ordering Agreement: Small Business – Environmental (NAICS 562910)  Satisfies Grass Maintenance Needs  Satisfies Reporting Needs  Satisfies Compliance Timeliness 12

Mature Covers Primary Maintenance: • Clearing Fences of Wind- Blown Weeds Chemical Waste Landfill 13 December 2016

Chemical Waste Landfill Buffer Area: Herbicide 3 ft outside Perimeter Only 1 Pre-emergent Herbicide Application at CWL Scheduling Preventive Maintenance 14 Corrective Action Management Unit

Mixed Waste Landfill: June 2016 Mature Cover: Still Hand-Pulling Weeds, But Fewer Weeds Hand-Raking Grass Clumps 15 Chemical Waste Landfill: July 2017

Best Practices Erosion Controls Mixed Waste Landfill 2016 16 Mixed Waste Landfill 2018