La Mesa Miracle

WASTE AGE STAFF

When La Mesa, Calif., visitors try to identify the attractive new building nestled in a smartly landscaped mesa in a central part of town, they often speculate about whether it's an upscale commercial building, a high-tech cleanroom facility, a health club or even a condominium development. But the new facility actually is a solid waste transfer station and materials recovery facility (MRF) owned and operated by EDCO Disposal Corp., Lemon Grove, Calif., and designed by the architectural and engineering firm J.R. Miller & Associates Inc. (JRMA), Brea, Calif.

Situated in a large public works yard owned by the city of La Mesa, a suburb of San Diego with a population of 56,000, the project is visible from densely inhabited commercial and residential areas nearby. When planning for the new facility began, there was widespread public concern that the transfer station and processing facility might be an industrial eyesore. Of course, aesthetics - although a dominant factor - were by no means the only concern.

In planning the project, EDCO, JRMA and the city joined forces to resolve a variety of waste management and recycling issues, meet tight time and budget constraints, and find a practical, affordable way to construct the facility on a confined and difficult site.

"The city of La Mesa needed a better, more flexible approach to waste management," says Sandy Schultz, assistant city manager. "County landfill fees were rising rapidly, but long-distance hauling to a less-costly landfill site was not a viable option."

La Mesa also needed to pull more material out of the waste stream to meet state-mandated reduction goals for landfilling. The city wanted a "one-stop shopping" facility that would be more convenient for local businesses and residents, Schultz says. Although the city needed the facility, people were concerned about how it would look and affect the area. La Mesa turned to EDCO, its franchised hauler, for a solution.

Solid Waste Considerations EDCO and its various consultants came up with an approach that successfully met all La Mesa's goals. Once deciding that constructing a transfer station and solid waste processing facility was essential, EDCO selected JRMA because of the firm's experience in planning solid waste transfer and processing projects, its ability to assist with community outreach and the track records of its completed facilities.

La Mesa is a middle-class, highly developed San Diego suburb that contains a shopping mall, numerous retail and professional businesses, and a small industrial area.

Based on a waste characterization study, the transfer facility was designed and permitted to process 1,000 tons per day - 30 percent residential, 55 percent commercial and 15 percent industrial waste.

Residential customers have a fully automated two-barrel collection system, and the recyclables are taken to an EDCO materials recovery facility in an adjacent city.

The first task for the project team was to determine the station's goals. La Mesa wanted to be able to receive and transfer all non-recyclable wastes, including those from self-haul customers. This meant that equipment to recover recyclable materials from the commercial waste stream also would be needed.

Additionally, the city wanted a drop-off for antifreeze, batteries, oil and paint, and a buy-back center for recyclable materials. Based on the anticipated future growth and the possibility of accepting wastes from other cities, the team set the 1,000 ton per day target design volume.

The project team also had to quantify the MRF's needs to allow adequate floor space for the equipment. The team estimated tipping floor size, number of loadout ports, and size and speed of conveyors by considering the throughput requirements based on hours of operation. At that point, the preliminary building size could be determined.

Project Challenges Because La Mesa has few undeveloped areas, only three eligible project sites were available. The project team rejected one site because of unsatisfactory access and distance from collection routes, and rejected a second site because of extensive demolition requirements.

The city yard was selected because of its convenient location - almost precisely in the center of town - and freeway access. Although it was the most desirable site for the proposed project, the yard presented many architectural, environmental and engineering challenges.

The site included a steep hillside with a 43-foot elevation change from top to bottom. At one side is a steep embankment with a trolley line at the bottom of the slope. Across the tracks is one of La Mesa's main commercial streets with a residential area beyond that.

The team determined the building would need a minimum floor area of 60,000 square feet and a wall height of approximately 45 feet. Because of the elevation change across the site and the enormity of the building, it would be prominent when viewed from the adjacent areas. Thus, the architectural design demanded sensitivity to the building's scale and location.

Construction was complicated by undocumented fill areas along with the possibility of contaminated soils and a large water main traversing the site. The city required access through the site to remote parts of its yard and maintenance of a rail spur without disruption. Also, construction could not affect the trolley line or a $1 million per day fine would be imposed.

Because the facility would be surrounded by other development, controlling dust, odor and noise emissions during construction and operation was another crucial factor that had to be resolved in the design.

EDCO, JRMA and the city's design review board, a panel of staff professionals and volunteer architects held a number of meetings to resolve the complex design and engineering issues posed by the project. To help gain approval from the city council, the project team used computer-imaging techniques to simulate how the building would look on the site.

For aesthetic reasons, the original concept called for hardwall construction such as masonry or concrete. However, after analyzing this option, the design team determined these materials would not be practical because of the slope and lack of space on the confined site, as well as the seismic and foundation requirements for the significant weight.

A pre-engineered metal building with preformed metal walls seemed to be the best solution. But because of aesthetic sensitivities, the city would not have approved a conventional metal "box."

JRMA, working with the design review board, created an attractive exterior design based on two types of metal wall panels: a smooth, flush-faced panel used on both the building's upper- and lower-wall sections, and a deep-fluted, horizontally applied panel used across the wall's middle section, to create a contrasting band of hue and texture.

"This wall design uses and reveals shadow lines to create a richer texture than concrete or masonry could have provided, and the panel variations work to subdue the massive building," explains James R. Miller, president of JRMA.

The design also features a largely conventional attachment of the wall panels to the building. "We were able to design an unconventional-looking building while staying within the confines of metal-building technology," Miller says.

"The building is nestled into the slope of the site so that it appears considerably smaller than its actual 61,900-square-foot size," Miller continues.

Metal Architecture Magazine recently gave the project a design award for its outstanding aesthetics.

Mitigating Environmental Issues The facility now can receive and dispatch more than 100 trash collection or transfer trucks per day. Public hours are from 8 a.m. to 5 p.m., but facility operations may be conducted 24 hours a day, seven days a week.

Because of the hours of operation and large traffic volume, noise, dust and truck visibility were concerns. The building team resolved these issues by using site walls and landscape screening, selecting a building orientation that would best locate truck queuing and loading operations, and fully enclosing the building.

To further address air pollution concerns, an air freshener misting system controls dust during trash transfer operations. This system causes the moisture-laden dust to sink to the floor and mingle with the trash, preventing dust and odors from migrating outside. It is controlled by a timer set to activate for five minutes on 15-minute cycles or continuously when the large truck door is opened. It can be activated manually, depending on types of waste in the facility, temperature or wind conditions.

Plastic curtains also help to contain odors, and doors are closed quickly after trucks enter or exit. In addition, the building alignment was chosen to provide the most dust control for load-out ports exposed to prevailing winds.

To avoid environmental issues related to possible exposure of contaminated soils under the old building, the existing concrete slab from a demolished building was left in place for use as a loading and rail-access area. The portion of the slab that conflicted with the new station was saw cut and removed without disturbing any soil.

Meeting Time and Cost Constraints With landfill fees rising rapidly, La Mesa needed to stabilize costs as quickly as possible. Equally pressing were stringent state mandates, which required the city to reduce the amount of trash sent to landfills by 25 percent initially and 50 percent by 2000. California required a fast-track project schedule to implement the plan.

To achieve this, Riha Construction, La Mesa, was added to the team as construction manager, advising on schedule and cost impacts of various design considerations. This teamwork proved key to completing the entire project -including planning, permitting, design and construction - in only 585 days.

The choice of a pre-engineered metal building with preformed metal walls brought significant savings in weight and, consequently, in foundation costs. The weight reduction resulted in lighter framing because of seismic loading. A pre-engineered building also provided the most economical way to achieve clear spans up to 230-foot wide and a minimum 30-foot clear height to accommodate waste transfer operations. The design also incorporated many other cost- and energy-saving features, including translucent roof panels for day lighting.

The architectural upgrades increased costs 4 percent to 5 percent compared to a standard metal building, but overall costs still were more economical than hardwall construction. American Buildings Co., Eufaula, Ala., designed and fabricated the pre-engineered building system by using JRMA's design criteria. Shook Building Systems, Mira Loma, Calif., erected the metal building system.

Resolving Site, Engineering Concerns To address the complexities of the site and the project itself, the design team, including Nolte Associates Inc., Corona, Calif., a civil engineering subconsultant to JRMA, had to resolve several engineering challenges. Overcoming the challenges eventually earned the design team an award from the San Diego Chapter of the American Society of Civil Engineers.

The design had to accommodate circulation of a wide variety of vehicles. A significant feature of the design is a ramp from the tipping floor that swings out and over the load-out tunnel. Another unusual feature is the positioning of the recycling loading dock, which takes advantage of a 4-foot drop to the street. This allows access to and from the loading dock, and simplifies truck egress.

Using the rear wall of the building as a retaining wall, the design team eliminated the need for a large, unsightly retaining wall along the trolley tracks and avoided conflict with the transit facilities. A masonry screen wall was placed above a 1-to-1 reinforced slope, screening the view of the building's exposed concrete.

Reinforced-earth technology was used at two locations: along the trolley line, which was landscaped with ground cover and shrubs; and along the existing 42-inch water line, which could not be disturbed because it supplies critical agricultural water to growers. A colored gunite finish was added to the reinforced slope along the water line to prevent further erosion.

Because there are many grade changes throughout the site driveways, the ramp and load-out tunnel had to be designed and checked for vertical clearances of the trucks and trailers. Considerations included critical overhead clearances and clearances of the kingpins under the trailers. Turning radii calculations were made to alter existing circulation patterns around the site. Existing driveways were converted to one-way to accommodate the turns. The team widened and redesigned one driveway vertically to allow access to the rail spur.

Satisfying "One-Stop-Shopping" Needs The new station is a multi-functional facility designed to handle all aspects of solid waste - disposal, recycling, household hazardous waste, drop-off, buy-back, public self-haul and solid waste processing, says Steve South, EDCO chief operating officer. In addition, recyclable materials can be transported out using the existing rail spur.

Consumers and business owners who previously had to make a one-hour round trip to the nearest landfill now can drop off trash at a convenient, easy-to-access facility. Since the new station opened, the city has reduced commercial and residential collection costs and has passed along these savings to customers, who are saving money as well as time. La Mesa anticipates long-term revenue gains as other neighboring jurisdictions begin to haul waste to its facility.

Another interesting aspect of the project is the unique leasing agreement. EDCO is leasing the site from the city, which plans to use the leasing revenues to fund much-needed improvements to the public works yard. "Without this arrangement, we would not have been able to accomplish this goal in the foreseeable future," Schultz explains.

According to Schultz, the single biggest accomplishment of the project is its aesthetics. "During the planning stages, city council members toured a number of transfer facilities that were quite attractive, but this facility is much nicer than anything else we saw."

The community also has responded favorably. The building's aesthetics conceal its true function, and efforts to address environmental concerns also have paid off. Despite the large volume of truck traffic, some neighbors have said they didn't know the facility was running.

The city, its residents, the operator and the building team received a lot more than they expected, and perhaps set a new standard for solid waste transfer station design in the process.

"The building outshines everything in the area," Schultz says. "It's certain to be a catalyst for other improvements."