Public Works and Environmental Services

Fairfax County, Virginia

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Matthew Kaiser,
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Fairfax County Uses Crushed Glass in Construction Project for First Time

In the video above, Channel 16 interviews project manager Suzy Harding as crushed glass is placed in the trench to support a new sanitary sewer pipe.

Sanitary sewer replacement projects rarely make headline news. Digging up, repairing, and replacing aging pipes is just part of wastewater infrastructure’s life cycle. It happens all the time, and usually in places well away from public view. But when a project embraces sustainable practices and the idea of a circular economy and finds a constructive use for a waste product, it is worth mentioning.

One example, a project along Flatlick Branch in Fairfax County’s Sully Magisterial District, is currently underway. When the new sewer pipe is placed in the ground, it will rest on a bed of crushed glass instead of the traditional bedding of quarried stone.

 

Flatlick Branch III Map
A sanitary sewer replacement project in western Fairfax County is using crushed glass as pipe bedding and fill material.

 

The Glass Problem

Some people may ask, “Wait, used glass is a waste product? I thought my glass gets recycled?” Unfortunately, the market for recycled glass in our area has been declining for years, and glass is notoriously difficult to process. States with bottle deposit programs and communities that collect recyclables separately are able to recycle more glass, but Virginia doesn’t have a bottle deposit program, and Fairfax County has a single-stream recycling program (comingled recyclables in one bin), which was put in place to increase participation and ease of use.

Glass creates many problems for single-stream recycling. It is heavy, which adds cost to transporting recyclables to and from recycling centers.  Glass containers placed in curbside recycling bins break during collection and transport to material recovery facilities, or MRFs, where recyclables are sorted. The abrasive broken glass damages the machinery at the MRFs. Glass also contaminates bales of other more valuable items, such as cardboard and plastic. Contamination has become a major problem for the recycling industry in the past two years since China, the largest customer for recycled material, imposed strict standards on the quality of recycled material it accepts.

Tipping Floor at Recycling Center
Comingled recycling is dumped on the tipping floor at a recycling center. Broken glass contaminates other materials.

For years, most glass has passed through the recycling process as residue, or waste. Some of the glass is applied as landfill cover, an approved use by the Virginia Department of Environmental Quality, but most of it is simply landfilled with other unrecyclable waste.

Unrecyclable Waste is Trucked to a Landfill
Unrecyclable material, including glass, is loaded into trucks at the end of the sorting process and delivered to a landfill.

As recycling has become more expensive, many recycling programs around the country have removed glass from their collection programs, but Fairfax County has decided to weather the current market challenges until markets for recycled glass recover. In the meantime, MRFs are investing in improvements to their sorting equipment in an effort to remove glass at the beginning of the process, and the county’s Department of Public Works and Environmental Services is exploring a new use for glass.

A New Use for Glass

Residents are encouraged to deliver their clean glass to drop-off areas located at the I-95 landfill complex in Lorton, and the I-66 transfer station in Fairfax. Glass that is taken by residents to drop-off sites in Fairfax County, the City of Alexandria, and Arlington County is collected in large containers and delivered to Fairfax County’s glass processing plant, a large pulverizing machine that can crush up to 20 tons of glass per hour. The crushed glass has been tested and approved for construction uses, such as bedding and fill in the Flatlick Branch sanitary sewer replacement project.

The sanitary sewer replacement project is being completed as part of the larger Flatlick Branch stream restoration project in the Cub Run Watershed. The stretch of stream spans a little more than two miles from Route 50 to Route 28, and the work was divided into three phases (SlideShare: Phase I, Phase II). The first two phases have been completed successfully, and final phase is underway. Except for a 1,000-foot gap where easements could not be acquired, phases I and II of the once badly eroded stream corridor have been reconnected to the floodplain, stabilized, and replanted with native vegetation to provide food and habitat for wildlife. When phase III is complete, the result will be a healthy stream with improved water quality and rehabilitated infrastructure, and parkland and private property will be fortified against erosion.

Before and After Stream Restoration
The Flatlick Branch stream restoration project reconnected the stream to the floodplain, stabilized stream banks and stream bed, and installed native vegetation. Phase II before (left) and after (right) pictured. Phase III will proceed after the sanitary sewer replacement project is complete.

In addition to restoring the stream corridor’s ecological functions, the Department of Public Works and Environmental Services rehabilitated the sanitary sewer line that runs through the area, using the non-invasive Cured-in-Place pipe lining technique, in which a plastic tube is inserted into the pipe to increase the pipe’s lifespan by 50 years. This trenchless method is far less expensive and creates less land disturbance than replacing old sewer pipe; however, some replacement is necessary.

Sanitary Sewer Pipe Replacement

The section of sanitary sewer pipe to be replaced is approximately 175 feet long and crosses under the stream. The new pipe is made of ductile iron, which is required for pipes that pass under a stream. Upgrading the pipe will provide the capacity to handle anticipated larger flows, and encasing the pipe in steel ensures the pipe will be protected well into the future.

Crushed Glass in Trench
Contractors spread crushed glass to create a bedding for the new sanitary sewer pipe.

Sanitary sewer pipes are buried underground, and they need to be stabilized in place. Typically, pipes are placed on a six-inch-deep bed and then covered with four inches of crushed stone to secure the pipe in place before soil is backfilled into the excavated trench. Rather than quarried stone, the section of pipe in the Flatlick project will rest on crushed glass – and lots of it. An estimated 525 tons will be needed to secure the pipe in place.

Using glass recovered in Fairfax County reduces the county’s reliance on quarried stone, which lowers material costs and provides an alternative waste use for glass. The crushed glass should support the sanitary sewer pipe for decades to come. If this application produces the desired results, future stormwater and wastewater pipe replacement projects will include crushed glass in their plans.

Moving forward, the county’s Solid Waste Management Program is actively trying to develop relationships with potential sources of clean glass, such as bottling companies, breweries, and wineries. Reliable and consistent sources of glass feedstock are necessary to ensure enough material is on hand for the construction projects that need it.

Glass is still accepted in Fairfax County’s curbside recycling bin program; however, recovering glass from the private sector MRFs is currently not possible. That glass is accumulating in landfills outside the county. Residents who take their clean glass to drop-off areas can be assured that their glass will be reused in a beneficial way that contributes to the county’s environmental sustainability goals.

Container for Recycled Glass
Glass collected in containers at residential drop-off sites is delivered to Fairfax County's glass processing plant.
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