As part of its 200th anniversary celebration this year, the Town of Southbridge is hosting a number of Walktober events. Late this morning I joined a crowd at the Southbridge Landfill (of all places) on Barefoot Road where one of these events, an Open House, had been in swing since 10 am. I came for a tour of the facilities which got underway shortly after I arrived. About eight of us jumped into a shuttle bus hired for the occasion, and off we rode with Site Manager Tracy Markham, a thirteen year veteran of the department, as our guide.
Opened in the early 1980s, the 52-acre landfill, the state’s largest active landfill, is owned by the Town and is currently operated by Casella, a firm specializing in municipal solid waste management. In the early years, the landfill only accepted construction debris, but today is it a full-service operation using modern techniques of waste disposal and adhering to rigid environmental standards. The landfill is permitted for a maximum of 2000 tons of waste per day; the trucks bringing in the garbage are carefully weighed at the scale house, so that the tonnage accepted at the site is recorded and monitored.
From the bus, we watched the 60-ton cat compactor, which works continuously, its 10-inch spikes crushing the garbage delivered by as many as sixty vehicles per day. Here’s one now:
In the background you can see the million dollar compactor (the photo doesn’t do it justice):
The landfill uses the double-liner methodology. Made of HDPE, this material is laid down in 20-foot wide strips and heat-fused together (a sample was passed around for us to examine). The regulations concerning landfills have changed over the years: at first, they could be unlined, then they were supposed to be clay-lined, then the standard changed to single-layer then finally double-layer plastic, which is state-of-the-art today (notice the pipes sticking out the top).
The maximum height of the landfill, 850 feet, is constrained by the site’s proximity to Southbridge Airport. Other factors also play into when the landfill reaches capacity. Insofar as this landfill has been in use for over thirty years, the Town is considering options for that scenario. Here’s part of the landfill which has been capped (I think this is what I photographed):
The information we received from our tour guides, together with the brochure I picked up, describe a highly-designed system engineered for health, safety, and efficiency. The land is first excavated to the layer of least permeable soil (in this case, clayey glacial till), then an underdrain system is installed, consisting of perforated pipe wrapped in a geotextile. On top of that is the double-liner system. The secondary liner consists of 24 inches of compacted clay, a layer of geosynthetic clay, the 60 mil plastic liner, then the geocomposite drainage layer. The primary liner consists of the same three layers: geosynthetic clay, 60 mil plastic, geocomposite drainage. When a site is filled to capacity, another composite liner will cap the landfill. Even after the landfill is closed, the two processes described below, collection of leachate and the combustion of gas, will continue for decades, and will be closely monitored.
The drainage layer collects water which is then pumped out. The water which percolates through the landfill is called leachate and is collected through perforated piping. It is pumped into these blue storage tanks; the little one has a 72,000 gallon capacity and the big one can hold 500,000 gallons of liquid. From here, this wastewater goes to a wastewater treatment plant where it is processed. These tanks here in Southbridge are kept at 50% full for safety reasons, mainly having to do with the capacity of the treatment plant to accept the leachate (and not because it’s inherently dangerous to store the liquid here).
At this point in the tour, we disembarked to visit the landfill gas-to-energy conversion plant, which was also fascinating. Gas collection wells, which are pipes sticking out of the landfill, collect gas generated by decomposing waste. First the gas has to be treated to remove sulfur, then most of it is flared off (two-thirds of it, if I understood correctly), and a third is converted into electricity, which is sent to the grid (inasmuch as the power is generated from a natural process, it is considered a renewable source). This particular generator has a 6 megawatt capacity, which is sufficient to power 2000 homes. The black tower is where the gas is burned off.
This building houses the 20-cylinder conversion engines, which are very powerful (and loud):
Our final stop on the tour was the C&D materials recycling plant, a 47,000 square foot facility operated by Complete Material Management, LLC. This facility accepts only construction and demolition debris, 80% of which can be recycled. When waste is brought in, it must first be separated; often the first pass is done manually. Other machinery can sort the material by size or by type, such as wood, metal, and “ABC” (asphalt, brick, concrete).
This is the where the dump trucks arrive:
You can see a lot of wood in this pile. Much of the wood can be chipped; the product is eventually shipped to Canada for processing into particleboard.
The yellow machine in the background is the first step in the sophisticated sorting process:
Our guide to this facility, the company’s CFO, praised their relationship with both Casella and the the Town; he also mentioned that the facility employs between 20 and 40 people, which is a benefit to a town like Southbridge, with its persistent high levels of underemployment. One might instinctively react with dismay at the thought of working in this industry, but protecting worker health is a priority; moreover, the recycling of these materials is a critical component of sustaining environmental quality. The construction materials recycling industry also uses sophisticated technologies as well as skilled equipment operators, which would make employment more interesting and appealing, I would think.