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Crushed Glass Fill at Little Rock Housing Project

Case Study by Chris van Daalen
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Crushed Glass Fill at Little Rock Housing Project
Building Material - Recycled
Glass Cullet as Fill/Bedding Material
John Darnall, City of Tumwater
Housing Authority of Thurston County
MWA Architects
Synergy Construction
Schock Brothers Construction
Awards Evergreen Sustainable Development Standard (V1.2)


Construction of a 40-unit apartment complex with a 1,000 square-foot community building. Plus an additional 8 units in a future phase, bringing the total to 48 units. Site was developed with Glass Cullet (made from crushed bottles diverted from municipal waste) as a 100% substitute fill material to construct a slab-on-grade foundation capillary break, and for waterline pipe zone bedding. Approval of the alternative material required endorsement of geotechnical engineer and warrant by subcontractor of product quality, using manufacturer supplied 3rd-party product testing data. Glass cullet provided a low-cost, highly workable, permeable and structurally stable (equal or better) alternative material that is also clean and safe for workers and the environment.

Permitting Process

The use of Glass Cullet as a 100% substitute for natural aggregate material is a known alternative material to the building officials and inspectors in Tumwater, WA. The Building Owner specified the product as an acceptable material for foundation backfill and pipe zone bedding, based upon the endorsement of the geotechnical engineer of record for the project. While some officials have applied WS DOT Standard Specification 9.03.(.09 - .21), it was not applied in this case as the owner, engineer and building department had already approved its use at 100% concentration (WS DOT limits to 15% blend). Testing requirements to determine the suitability of this material as bedding/fill/backfill material relate to appearance, absence of hazardous substances, permeability and compaction.

Code RequirementCompliance Path
International Building Code Sec. 1802.2 – 1802.6 Endorsement by Geotechnical Engineer; 3rd Party Testing Data certifying product quality
Washington State Department of Transportation Standard Specification 9.03.(.09 - .21) Review and approval of product use by Code Official & Inspector

Testing requirements applied to glass aggregate used as alternative fill material include:

  • AGI visual test for foreign debris content
  • EPA Method 3010/6010 for determining organic content and chemical contaminants
  • Visual test for compaction, rubber tire “roll test” results are “Firm and Unyielding” (or Compaction: nuclear densometer or sand cone test)

Project Description

Crushed glass cullet was used as a 100% substitute for natural aggregates (e.g. sand and pea gravel) as fill/bedding material to construct a slab-on-grade foundation capillary break, and for waterline pipe zone bedding. According to the Clean Washington Center’s Construction Inspectors Guide to Recycled Glass Aggregate glass aggregate and blends are strong, clean, safe and economical.”[1]

Glass cullet is manufactured out of crushed post-consumer bottles from municipal waste/recycling stream by secondary recycling processors and/or glass cullet supply companies, in this case Concrete Recyclers, Inc. of Tumwater, WA. It is crushed to a 3/8” minus size, sifted of debris and other impurities to create a consistent high-quality project with a ratio of coarse and fine material sizes which meets the WS DOT sieve test requirement[2] for the specified type of aggregate, the specification used by the building official as a requirement of approval.

Samples of product are sent to independent environmental laboratories to test for copper and lead content (samples collected according to ASTM D 75[3], tested using EPA method 3010[4]/ 6010[5]) and certified for total Lead content of no more than 250 ppm. The manufacturer supplied the test data and a Material Safety Data Sheet on the product to the subcontractor for material submittals. Using this data, the contractor warrants the product to satisfy the required specifications prior to delivery.

Field tests were also conducted to ensure the product conforms to allowable debris level (up to 10% by visual inspection, or 2% to 4% by weight using American Geological Institute[6] method).

Compaction was tested using the “roll test” method to ensure product is “firm and unyielding” under load. The use of the material was endorsed by the geotechnical engineer working on the project.

The residential and commercial building code has few specific requirements regarding the use of unbound aggregate for utility bedding, backfill, foundation materials, and drainage features (the applicable general code sections are International Building Code Sec. 1802.2 – 1802.6). Therefore the standard specification most cited in relation to the product is the DOT Standard, first adopted in 1994. However, this specification only allows a 15% blend of glass cullet with natural materials for foundation backfill and pipe zone bedding. While DOT’s quality specifications were used, the project deviated from the 15% limit due to the owners’ previous knowledge and experience, the subcontractors decision to use the product and the geotechnical engineer’s endorsement of the product as a 100% substitute material. The City of Tumwater inspector of the project approved the use based on contractor certification of the product.

The cost of glass aggregate is commonly 50-65% less than comparable natural sand and gravel material, offering a significant price advantage over natural materials when transportation costs are comparable. Hauling costs must be taken into account due to the fact that there are relatively few suppliers and distribution points for quality recycled glass aggregate material. Contractors who use the product report that a hauling distance of up to 30 miles farther than natural aggregate materials is viable.

Project Contacts:

Resources & References:

Clean Washington Center, September 1995.  Construction Inspector’s Guide to Recycled Glass Aggregate.  Technology Brief
Glass Aggregate Summit supporting materials
Washington State Department of Transportation, 2010.  Standard Specifications for Road, Bridge and Municipal Construction, M41-10

ASTM International, 1996-2011.  ASTM D75 / D75M - 09 Standard Practice for Sampling Aggregates.
U.S. Environmental Protection Agency, July 1992.  Method 3010A:  Acid Digestion of Aqueous Samples and Extracts for Total Metals for Analysis for FLAA or ICP Spectroscopy.
U.S. Environmental Protection Agency, February 2007.  Method 6010C:  Inductively Coupled Plasma-Atomic Emission American Geological Institute, Spectrometry.
Evergreen Sustainable Development Standard (V2.0), Washington State Department of Commerce:


Project Contacts
Builder: Dave Jorgenson Synergy Construction (425) 488-4500 Designer: Bill Lanning, Architect MWA Architects (503) 973-5151 Approving Offcial: John Darnall, Building Official City of Tumwater (360) 754-4180
Approving Offcial: Kelly Crawford, Inspector City of Tumwater Owner: Bob Ricks Housing Authority of Thurston County (360) 753-8292 ext 19 Subcontractor: Lorenz Schock Schock Brothers Construction (360) 704-7944
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