The Puente Hills Landfill in Los Angeles County, California, is the largest operating landfill in North America based on daily tonnage received. Located in an unincorporated area of Los Angeles County near Whittier, California, it is owned and operated by the Sanitation Districts of Los Angeles County. It has received approximately 118 million tons of solid waste as of April 2008, raising the original site elevation by over 350 feet and earning it the nickname 'Garbage Mountain.' Liquid management and groundwater sampling pumps from Geotech's pump and remediation equipment supplier, QED help keep the landfill operating at peak efficiency.
When construction on the Puente Hills landfill began in 1957, it was known that someday the site would require liquid management, so both 2' monitoring wells and 4' leachate wells were drilled throughout the landfill during construction. As the landfill expanded, even more wells were added. By 1995, there were over 500 4' leachate wells. But by 1999, landfill liquid had become a problem; methane was being produced and condensate was beginning to collect in the wells along with plant and tree irrigation water. Landfill operators were using electric pumps moved portably from well to well; liquid levels would rise in one area of the landfill, they would pump it dry, remove the pump and move to another area. In 1999, 6 QED AutoPump Model AP2/TL submersible pneumatic pumps were installed as a pilot test in the original section of the landfill, Canyon 9. This was the beginning of the working relationship between QED and the Puente Hills Landfill.
In 2002, some of the old wells were abandoned and over 150 new wells were drilled. This time the wells were larger diameter, 6-8', to accommodate QED's AP4 4+ pumps. The combination of the 2' and 4' pumps worked well in all of the wells under vacuum and at depths of 200 to 300 feet. Everything was fine until a problem developed in the Phase Two area of the site.
The Phase Two area of the landfill was where winter cover asphalt had been dumped over the years. These wells were deeper than the previous Phase One wells (over 200 feet) and reached temperatures of 190 degrees. At the water-air interface in the Phase Two wells, calcium carbonate formations were crystallizing, plugging both the pumps and the wells. Pumps were being pulled to undergo extensive cleaning and repair but it was difficult to remove the pumps from the wells. In fact, 3 to 4 pumps were lost down well when support cables snapped as winches tried to pull the pumps to the surface but were unable to breach the calcium carbonate 'plugs' at the liquid surface. The landfill decided to look for a pump that did not have air/water contact and would be easier to repair if necessary. They found a piston pump that had been developed for groundwater remediation use. With this pump there was no air/water contact, the only fixed equipment down well was 1-1/4' diameter drop pipe with a foot valve on the bottom, and the pump driver was located at the surface for ease of repair. At the time, QED did not make a piston pump so Puente Hills purchased 250 of these remediation piston pumps.
Oil field piston pumps
Soon after the landfill installed these pumps they realised that remediation piston pumps were not suited to their heavy duty, 24/7 pumping demands. Down well, pistons were wearing out every 2 to 3 days, requiring 2 labour hours per well to replace. The level control was not reliable due to the constant pressure changes in the wells from trapped methane. The surface driver required frequent adjustment of the external limit switches that control the up/down piston stroke and there were no local service technicians who could help them with pump problems.
The Sanitation Districts asked QED engineers if they could design and produce a landfill piston pump to help them with this serious problem. QED jumped at the opportunity, engineering a heavy duty, long-lasting piston pump: The Iron Horse.
Iron Horse Extended Duty Piston Pumps to the Rescue
Over the course of 18 months QED developed a pump that was simple in design, required little or no regular maintenance, and met the rigorous demands of landfill service by delivering a life expectancy of 12 to 18 months instead of just two to three days.
QED placed five Iron Horse piston pumps in wells the Sanitation Districts had selected as especially difficult to monitor and evaluate. The pumping systems in these wells were tracked for 12 to 15 months. After their performance was reviewed and documented, Puente Hills ordered 30 new Iron Horse pumps. Iron Horse pumps are now the piston pump of choice at Puente Hills Canyon nine (the original landfill), along with Puente Hills North and South - all three areas of the landfill.
Over the years, QED has tested different types of pumps under operating landfill conditions with the Sanitation Districts' assistance. This has given QED valuable insight on what works and what does not work with a specific pump design.
The Sanitation Districts
The role of the Sanitation Districts of Los Angeles County is to construct, operate and maintain facilities to collect, treat and dispose of wastewater, and to provide for disposal and management of solid wastes. The landfill is currently limited to a maximum of 13,000 tons of solid waste per day, an amount that is usually received before noon. It also receives over 3,000 tons of recyclables per day that is diverted to a one million square foot, state of the art MURF Facility. As a result of these programs and efforts, the Districts recycled more than one million tons of material during fiscal year 2004-2005.
The Sanitation Districts are leaders in the landfill industry, installing extensive networks of LFG collection systems on all of their sanitary landfills. The majority of the collected landfill gas is utilized for electrical power generation. PERG, Puente Hills Energy Recovery from Gas, produces enough methane to generate 46 MW of net electricity, enough to power 75,000 homes every day. The Puente Hills Landfill is also involved in a Cleanfuel Program that uses a highly purified landfill gas to create vehicle fuel on site. The landfill is permitted until 2013.
A new landfill to ultimately replace the Puente Hills operations is under construction in an abandoned gold mine in the California desert. Rubbish will be sent from Los Angeles by rail to Mesquite for processing. The new landfill already has 50 Well Wizard groundwater sampling pumps in place at depths of 600-700 feet. It is envisioned that proven QED AutoPumps will be utilized to address the new site's liquid management requirements when the new landfill site becomes operational in 2013.