TRASH ON SPEED

Michael Fickes

TWO NEW TRANSFER STATIONS, one in Puente Hills, Calif., and the other in Washington, illustrate a coast-to-coast trend toward larger, more productive and more automated facilities.

As close-in urban landfills permitted decades ago approach closure, municipal solid waste departments and private waste management companies in large cities are constructing a new generation of transfer stations designed to move waste to regional landfills that may be located hundreds of miles away. “Today, waste is traveling greater distances than ever to find cost effective and environmentally sound disposal facilities,” says Mark Clinker, director of environmental engineering and compliance with Ft. Lauderdale, Fla.-based Republic Services Inc. “As a result, we're seeing an increase in the number of transfer stations being constructed.”

The size of those transfer stations is increasing, too. Often five times larger than their predecessors, today's newest transfer facilities are being built to process 3,000 to 6,000 tons of waste per day (tpd), compared to the 1,000- to 1,500-tpd facilities considered large in the 1990s. Republic Services, for example, operates three 6,000-tpd facilities in Las Vegas alone.

More and more transfer stations also are serving dual purposes. For instance, the Puente Hills station includes substantial materials recovery facility (MRF) equipment that separates and re-routes recyclable materials to appropriate handlers, while sending only residual trash to landfills.

The new facilities are also advancing the art of transfer station design with carefully planned traffic patterns, automated scale houses, multiple transfer pits, sophisticated scale systems in the pits, overnight storage capabilities, and elaborate odor and dust control.

Technology is making transfer facilities more productive than ever. The Washington facility, for example, can load a transfer trailer in 10 minutes.

While some facilities — the Washington station, for example — will continue to move trash to landfills by semi-trailer, Puente Hills and others like it will combine trucking operations with lower-cost rail transportation.

Crunch Time at Puente Hills

In 2013, the 13,200-tpd Puente Hills Landfill is expected close, and the Los Angeles County Sanitation Districts (LACSD) will have to find another home for one-third of the county's trash. “Obviously, there will be a crunch,” says Bob Asgian, supervising engineer with the Whittier-based LACSD.

A waste-by-rail system will bridge the gap beginning in 2010. And the new Puente Hills MRF and transfer facility, located on 25 acres adjacent to the landfill, about 14 miles east of downtown Los Angeles, forms a lynchpin in the county's waste-by-rail plan.

Scheduled to open sometime this summer, the facility is designed to handle 4,400 tpd and will immediately handle about 4,000 tpd as soon as it opens. About 500 tpd of recyclables will be diverted. The remaining refuse will, for the time being, be moved by truck to other county landfills. In 2010, the transfer operation will begin loading refuse into intermodal containers set on trailers. The containers will transfer to trains at a local rail yard and travel to the 20,000-tpd Mesquite Regional Landfill in Imperial County, which is owned by and is being developed by LACSD.

The facility, which cost $38 million to design and build, looks more like an office building than a transfer station.

“Permitting requires the facility to be architecturally compatible with office buildings in the area,” Asgian says. “We want people to feeling comfortable visiting, so we could show them what we're doing here.”

Bird's Eye View

A three-story office building fronts the facility and houses the lion's share of LASCD's management and administrative offices. On the third story of the building, a gallery-bridge spans a truck corridor below and cuts into the MRF and transfer facility located behind the office building. “The bridge is for public tours,” says Jim Miller, CEO of JR Miller and Associates Inc., the Los Angeles design/architectural firm that worked with HDR Engineers to design the facility.

From the bridge above the MRF and transfer floor, touring public groups will look out on a 219,000-square-foot (sq. ft.) floor — an area equal in size to approximately 10 football fields. Shaped like a rectangle with the long sides running east to west, the floor design accommodates recycling as well as transfer operations.

At the north end of the east wall is the truck entrance. Just outside the building, there is an automated scale house with three inbound scales. Two outbound scales sit to the south, also just outside of the east wall. Most of the arriving trucks have recorded tare weights and won't need to weigh out. The few un-tared trucks, as well as the transfer trailers and the trucks carrying recyclables, will use the outbound scales.

Arriving trucks will tip directly onto the massive central floor, travel to the southwest corner of the floor, leave the building, turn left, or east, and travel through a passage cut between the office facility and the tipping floor to the exit scales on the southeast side of the building.

Inside, a two-tiered series of conveyors and screens supplied by CP Manufacturing, San Diego will sort the trash. The first tier of conveyors will capture cardboard, while the second tier will grab intermediate fiber materials. Smaller materials will fall through to the floor where employees will manually separate paper, plastics, metal and wood.

“Our initial target is paper and cardboard,” Asgian says. “Once we're underway, we'll design additional equipment sets to separate other materials.”

Recycling workers will push smaller, unseparated recyclable commodities into bunkers under the floor. From there, conveyors will deliver recyclables to a MacPresse baler provided by Sierra International Machinery LLC, Bakersfield, Calif.

Material handling equipment on the floor includes two forklifts, two front-end loaders, a telescoping lift and a mid-sized loader. All equipment will run on alternative fuels, such as propane and liquefied natural gas.

The two front-end loaders will push the remaining refuse into six pits along the south wall of the rectangular floor. Below, two wheeled excavators will tamp down the trash as it falls into the transfer trailers, redistributing the trash as necessary to meet California's axle and gross weight limits. Cabs and transfer trailers in each of the pits will sit on three scales, for the trailer axles, the drive axles and the steering axles.

On the tipping floor, a large digital readout will report the weights on each axle as well as an overall total, making it easy for loader operators to maximize loads without exceeding legal limits.

The system is fast. According to Asgian, test runs have loaded the trailers in 12 minutes.

Controlling Odors

A misting system built into the ceiling of the building controls dust inside the building. “Because dust carries odors, this system also helps control odor,” Asgian says.

A number of other active controls and passive design features suppress odor. The building itself was carefully oriented to the prevailing winds, which blow from the northwest corner of the rectangle to the southeast corner. “We placed the entrance doors in the northeast corner and the exit doors in the southwest corner of the building to avoid the prevailing winds,” Asgian says. “We also located the loading pits on the south side of the building to separate them from the air flow through the building.”

Each of the building's air exhaust fans has been combined with a misting system that injects odor-neutralizing agents into air flowing out of the structure.

The facility design includes high-speed automatic doors that open or close in 10 to 15 seconds, and only when trucks enter or leave. The exit lane has an interior wall positioned to cut off the flow of air if both the entrance and exit doors happen to open simultaneously.

Recycling An Incinerator

Not all communities are as fortunate as the LACSD, which found a site for its MRF and transfer station on virgin land adjacent to the Puente Hills Landfill. Instead, land and siting issues often force many municipal solid waste departments to recycle existing facilities when they need a new transfer station.

For most of the 20th century, Washington disposed of its waste through a network of small transfer stations, incinerators and landfills. In 1992, the city got out of the incineration business and began to rely solely on transfer stations and landfills.

Many of the incineration sites were converted to makeshift transfer stations. In the early 1990s, the Benning Road incinerator in the southeast quadrant of the city received what solid waste officials call a Rube Goldberg makeover. With the addition of a conveyer system to feed the incinerator's old bridge cranes, the station could load open top transfer trailers. “It took 35 minutes to load one truck,” recalls Tom Henderson, solid waste administrator for the city Department of Public Works (DPW). “It was so slow, it was like watching water freeze.”

Between 2000 and 2001, the city council appropriated money for a city-wide infrastructure rebuilding effort, and DPW received funding to renovate and upgrade two of its makeshift transfer stations: the Benning Road station and another located on the other side of the city called Ft. Totten.

The $11 million renovation of the Benning Road station began in 2002 with the demolition of the old incinerator's smoke stacks and pollution control equipment.

While the old incinerator could dispose of 300 tpd, the new transfer station, which opened in June, can handle 3,000 tpd. “We took out a wall and built a 10,000-sq.-ft. addition with three loading pits on the long wall of the rectangular building,” says Michael Kalish, senior project engineer with SCS Engineers, Reston, Va., which designed the facility.

Trash trucks approach the building from the east after turning off of Benning Road, a major thoroughfare that connects to an interstate. The trucks move through a scale house with two inbound scales just outside the northeast corner of the building. Automated RF transponders identify the trucks, virtually all of which have recorded tare weights in the system. The few new trucks using the facility weigh in, dump their loads and loop back around to the scale house to weigh out.

After recording inbound weights, the trucks enter the building on the east side, veer south inside the building and back up to one of the three pits set on the north side of the building. The vehicles dump their loads and leave on the opposite side of the structure. The expansive floor is designed to accommodate three trucks at once.

Front-end loaders push the trash into the pits. Behind each pit on the tipping floor level, hydraulic cranes distribute and tamp down loads in the transfer trailers positioned below.

Equipment Innovations

Today's larger transfer stations would not be successful without the help of better equipment. The Benning Road Transfer Station has implemented several operational innovations common to most large, new facilities.

Multi-platform scales weigh all of the truck axles, for example. As transfer trailers arrive, the drivers insert cards into readers on the lower level when they are ready to begin loading. A green light on a large LED status board upstairs tells the loader and crane operators that a trailer is ready and tracks the axle weights recorded by the scales. Another status board in the pit enables the driver to monitor weights as well. “Each pit uses two status-boards, which eliminate hand signals and walkie-talkies, and speeds the process,” Henderson says.

Larger facilities also are helping to provide storage backups. For instance, while Benning Road's renovation covered half of the old incinerator pit along the south side of the rectangle, the original pit's remaining space has been set aside for storage. “After major snowstorms, you often have to wait to pick up waste,” Henderson says. “There will be a surge the day after. The old incinerator dealt with surges by storing waste. We've left half of their old storage pit uncovered so we can take advantage of the incinerator's surge capabilities.”

The facility also has been designed with an odor control system. “It is a neutralizing spray system that sprays a biodegradable mist into all the building's vents,” Kalish explains. “The system also helps to control dust at the exits. Another water spray system has been installed above the tipping area for dusty loads — this is only used as needed.”

To date, Kalish says the renovation has paid off. In the first month of operation, the facility transferred between 2,000 and 2,200 tpd of refuse. Washington says its next step will be to renovate the Ft. Totten transfer station and upgrade it to the level of the Benning Road facility.

The Puente Hills MRF and Transfer Station in California and the Benning Road Transfer Station in Washington illustrate the waste industry trend of larger transfer stations designed to feed larger landfills located farther away. “It's the only way to make it feasible to move trash to mega-landfills hundreds of miles from urban centers,” Kalish says.

Michael Fickes is Waste Age's business editor based in Cockeysville, Md.