Closing L.A. County’s Largest Landfill

March 28, 2013

Southern California’s Puente Hills Landfill, one of the largest landfills in the country, will shut down operations on October 31, 2013, with 127 million tons of waste in place and 10-plus million tons short of its permitted capacity. The site has been in operation since 1957, first as a private dump, and since 1970 as a sanitary landfill owned and operated by the Sanitation Districts of Los Angeles County (LACSD).

According to LACSD Division Engineer Robert Asgian, although procedures for shutdown of the 1,365-acre site are in the main routine, its closure is expected to send ripples throughout the county, including a hike in waste disposal costs for communities who currently use the landfill, a scramble for alternative disposal sites and the loss of 50 MG of clean energy to the Southern California electric grid, which is currently supplied by the landfill’s gas to energy project, the largest in the world. On the other hand, there will be a smile on the face of Los Angeles County Supervisor Don Knabe and homeowners in the communities the supervisor represents close to the landfill.

The Sanitation Districts are a public agency created under state law to manage wastewater and solid waste and consists of 23 independent special districts serving some 5 million people in Los Angeles County. The service area covers approximately 815 square miles and encompasses 78 cities and unincorporated areas. The Districts currently provides about one-fourth of the county’s solid waste disposal needs through the operation of three sanitary landfills, three landfill energy recovery facilities, three materials recovery/transfer facilities, and two refuse-to-energy facilities. The Puente Hills Landfill has received three 10-year extensions of its original land use permit, and as a condition of its final 2002 land use permit it agreed not to apply for any further extensions and would close the landfill as scheduled. No subsequent waste management facilities will be allowed to be constructed on site, including composting. The Puente Hills Materials Recovery Facility, which is located adjacent to the landfill, is permitted as a separate facility and will continue operating after the landfill’s closure.

According to Mike Mohajer, former assistant deputy director of Los Angeles County Department of Public Works, the final conditional use permit issued by the county requires the LACSD to maintain the landfill in perpetuity. The County Department of Public Health’s Solid Waste Management Program is the local enforcement agency. At issue will be landfill gas migration, water and air quality issues, and the integrity of the final cover.

The Specifics
As Mohajer points out, Los Angeles County’s regulations concerning landfill gas migration date back to 1975, when he rewrote revisions into the county building code, requiring that all structures and their occupants located on a landfill or within 1,000 feet of the sealed area containing decomposable materials must be protected from potential landfill gas migration. “We were the first jurisdiction in the nation to require that,” says Mohajer. “Since then, the US EPA and the state waste board have adopted it along with the City of Los Angeles.”

“We pioneered landfill collection systems,” says Asgian, “and we have a vast network of wells and trenches that collect landfill gas at the site. We will continue to collect the gas and use it to generate electricity during post-closure until it degrades in quality, at which point we will flare it. California in general and the South Coast Air Basin in particular have stringent requirements on emissions from landfills, and we will continue to do the monitoring and maintain our gas collection system so that we are in compliance with those regulations.”

As part of its closure plan, the Districts has concluded extensive site evaluations with the Los Angeles Regional Water Quality Control Board to demonstrate that the final landfill cover design meets state regulations. “All of our slopes to date meet the requirements,” says Asgian, “and we have an onsite stockpile of final cover material. When the landfill stops taking waste, we’ll start installing the cap on the remaining area that doesn’t have an approved cap on it right now, which is essentially the top area. The cover material is a native silty clay material that we have demonstrated, through numerous field and laboratory tests with the regional board, meets state requirements. We will be applying it a minimum of 5 feet thick, compacting it into place. We’ll be covering approximately 200 acres, and while we’re doing that, we’ll be removing inbound scales and infrastructure that will no longer be needed.”

Long-term Planning
“We’ve been constructing the various systems we will operate post-closure as we’ve built up the site,” says Debra Bogdanoff, senior engineer in the Districts’ Facilities Planning Department. “So once we get to closure we won’t have to go over the entire site and put in the gas system or landscaping and irrigation, only that portion that hasn’t been done since the last projects were completed. Typically, we do one gas system and one irrigation project a year, which will cover a lift or two as we build up. This means for closure itself, it will only be a matter of finishing up those unfinished portions near the top of the site and putting the final cover on.

California regulations require that a landfill operator continue to monitor a closed site until it’s is no longer deemed to be a threat to groundwater. In that aspect, the Regional Water Quality Board considers a closed landfill an active facility, but a spokesperson said the board would likely revise existing waste discharge requirements to focus on post-closure maintenance. One of the areas of concern will be what the board calls a “corrective action” being undertaken on a portion of the landfill that is unlined.

According to Salomon, the unlined sections are in the oldest part of the landfill and date back to when it was privately owned. “Monitoring wells detected discharges and we constructed subsurface barriers to block the flow, catch the water and treat it appropriately. There is limited treatment onsite but mostly the water is sewered.”

Slowdown in Tonnage
The landfill has experienced a drop in tonnage during the recent economic downturn that has affected not only the final closure design but also the waste-by-rail operation the LACSD was required to construct as a condition of its final land use permit. Although permitted for 13,000 tons per day, the landfill has been receiving roughly 6,000-8,000 tons per day, at one point dropping as low as 4,000-4,500 tons per day. “The reduction in tonnage certainly will change what the final contours look like,” says Bogdanoff. “We were sensitive to this in the preparation of the closure plan and post-closure maintenance plan. We actually went through several iterations of what the landfill would look like when we close and came to the realization that we were going to put forward our best estimate of what we thought, with the recognition that should tonnages go up for whatever reason, we would need to come back and make sure the plan as we had constituted it captured what we were going to do. If the fill plan changes, we’ll have to change the drainage to keep water off the filled areas. We’re not going to be as high, so the top decks aren’t necessarily going to be as small, and the drainage will have to change somewhat to accommodate that. The final cover will be compacted clay soil, 5 feet in depth on top of the 2 feet that we’ll already have in place.

Financial Guarantees
California regulations require that cost estimates covering landfill closure and post-closure monitoring and maintenance be figured at the rate it would take for a third party to perform those activities in case the landfill operator walks away and the state has to step up to the plate. “In the past when landfill sites got to the last day of taking trash, typically they closed the site and their solid waste facility permit was rescinded,” says Salomon. “With recent changes in financial assurances regulation, Cal Recycle thought it appropriate to continue five-year review of the closure and post-closure maintenance plans through the closure period to facilitate an ongoing look at whether the landfill operator could reduce the amount of money that had been set aside for closure. Aside from protecting the state, this is absolutely important to the landfill owner as well, because maintaining a landfill for potentially a very long time after it closes and isn’t generating revenue is something to be concerned about.

The new regulations also put the burden of proof on the landfill operator to demonstrate that the site has basically stabilized or has arrived at the point where there’s no further threat to the environment and public health, the goal being to encourage a consolidated look at the data to evaluate how the site is performing. “The details of the procedure haven’t really been worked out,” says Salomon, “but it’s going to mean several of the monitoring groups within the LACSD sitting down together to look at things such as the reduction of methane gas generation, settlement and water collected from behind the liner systems or behind the barriers. Once we see things are relatively stable, we will go back to the local enforcement agency and ultimately Cal Recycle and the Regional Water Quality Control Board with our conclusion that the landfill has stabilized and with the data to support it.”

Replacement Capacity
At the time its final permit was approved, county managers were concerned about the loss of capacity as an effect of the landfill’s closure. To comply with permit Condition No. 58, which required the development of a waste by rail operation, the LACSD secured the necessary permits for the Mesquite Regional Landfill, a 2,300-acre site in Imperial County to receive waste transferred by railroad. The landfill has a total capacity of 600 million tons and a maximum tonnage of 20,000 tons per day, with 1,000 tons reserved for Imperial County, and a projected 100-year life. Current regulations allow less than 4,000 tons a day to be delivered by truck. To handle shipping via rail the LACSD is constructing an intermodal facility in the City of Industry that when completed will have a permitted capacity of double that amount. Waste at MRFs and transfer stations in L.A. County will be loaded in sealed containers, trucked to the intermodal system rail yard, then shipped the 200 miles to the 5-mile spur that will deliver it to the landfill, the first in Southern California permitted to receive waste by rail.

But with the downturn in the economy, and given capacity at other landfills in the county, Asgian admits it won’t be economically feasible to operate the waste by rail system in the short term. The current plan is to contract for local landfill capacity until such time as the LACSD sees a need for waste by rail to operate. Aside from issuing advance warning for cities to begin planning for alternative waste disposal, waste by rail inadvertently resulted in decrease tonnage at Puente Hills along with operational changes among the county’s private haulers. “Puente Hills used to be the cheapest game in town,” says Asgian. “But when the 2002 CUP mandated we develop a waste by rail system, we began raising our rates to collect the half-billon dollars necessary to develop that system. As rates have increased, it’s become more cost effective for some of the vertically integrated companies like Waste Management and Republic and Allied to take their wastes to their own landfills, even though in some cases this requires hauling it longer distances.

Aside from challenges related to capacity and ease of disposal, materials that are now being beneficially used onsite at the Puente Hills landfill will also have to find new homes, including asphalt reused for road base, dirt from residential and commercial construction sites imported at no cost for daily cover, and particularly greenwaste, which the landfill uses as alternative daily cover, Mohajer estimates, at the rate of 900-1,000 tons a day. “According to state law the use of greenwaste for ADC is defined as “˜recycling not disposal,’ which means that under AB 8939, the communities whose greenwaste is currently going to the Puente Hills landfill get diversion credits, which average, I would say, about 6% of their mandated 50% reduction.

Options include composting or use as mulch for agricultural operations, although both applications will require more long-distance hauling.

Another fallout from the Puente Hills closure is the loss of $100,000 annually toward the county’s goal of changing state legislation to be more amenable to the development of conversion technology facilities in Southern Californian. Likewise, the Puente Hills Landfill Native Habitat Preservation Authority will lose the one dollar per ton it has been receiving from the landfill, which, according to Executive Director Andrea Gallo, will total $65 million by the time the landfill closes. Among other things, the funds have been used to acquire some 3,854 acres of open space to preserve native habit and to build the first wildlife underpass in Southern California. “We’ve been planning for this,” says Gallo. “The Sanitation Districts will continue to be on our board, and we look forward to their continued support and guidance.”

Another of the substantial fallouts from the closure will be personnel. Currently 130 people work onsite. “It’s our biggest site,” says Asgian, “so obviously this is a big hit. We’ve held certain positions open throughout the districts and contracted out some of that work. The plan is to provide continued employment of the Puente Hills staff in some capacity. Obviously they can’t all be working in their same positions, but the plan is to make the transition without layoffs.” 

Landmarks in the Operation of Puente Hills Landfill

1957: Site first permitted as a privately owned landfill

1960s: Asphalt diversion begins

1970: Site purchased by LACSD (1,214 acres)

1981: Additional 151 acres purchased

1982: Two gas turbines are installed

1986: Gas-to-Energy Facility, Phase I, constructed

1988: Tire diversion begins

1988: Site stops accepting nonhazardous liquid wastes

1988: Greenwaste recovery program begins

1990: Landfilling in Canyon 9 begins (north side of site)

1992: LACSD is first in nation to build a system to produce vehicle fuel from landfill gas

1992: Refrigerator and air-conditioner salvaging begins (expanded to all metallic discards in1994)

1995: Landfilling in the Eastern Canyons begins

2003: Gas-to-Energy Facility, Phase II, constructed

2005: E-waste collection begins.

Courtesy Sanitation Districts of Los Angeles County

About the Author

Penelope B. Grenoble

Penelope B. Grenoble writes on issues concerning waste operations, equipment, and technology.

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