Designed with Growth in Mind

Each municipality's population, including the unincorporated county population in its southern half;

State agency population projections; and

U.S. Environmental Protection Agency (EPA) data for average solid waste generation (per capita) in the United States.

Unfortunately, two of these assumptions underestimated the reality for the city and its successor agency, the South Utah Valley Solid Waste District.

Additional Facility Challenges

When the Springville Transfer Station was built, it also faced geological constraints, partially attributable to its location over soft, silty/clayey, fine, sandy soils deposited under a lake, and a water table about 3 feet below ground level. Combined with a commitment to close the Provo Landfill during 1991, these conditions severely limited the contractor's ability to design the site to accommodate a 16- to 18-foot grade separation for truck-top loading of transfer trailers.

Ultimately, these conditions drove Provo to build, and operate a side-load, pre-load compaction transfer station, which 10 years later, still is the only facility of its type in the world. By 1997, however, the accumulated wear and tear on the facility became obvious because of the design and waste generation underestimates.

Although the facility operated for less than 11 months during its inaugural year, the facility was handling more than 10 percent more waste than expected. Waste generation also was growing at an average of 6 percent annually during the first 6 years, compared to an annual state estimate of 2 percent.

Together, these underestimates meant that the Springville Transfer Station was processing 10 years of its planned wastes within its first six years. Or, put another way, the site had processed nearly 100 percent more waste than when it was planned in 1988.

Sensing an impending emergency, the SUVSWD began planning facility renovations that would ensure effective waste management, as well as allow for future growth.

Original Facility Design

In its original design, the Springville Transfer Station was built with five structurally separated unloading bays, each capable of accepting packer trucks or citizen drop-off vehicles. The site also included a pre-load compaction bay fitted at bed level to 18-wheel over-the-road (OTR) tractor trailer rigs. And a lift-and-load bay was fitted to OTR tractor trailer rigs when the pre-load compactor was undergoing maintenance. Additionally, plans existed to retrofit the lift-and-load bay to accept a second pre-load compactor.

Unloading bays 1, 2, and 3 primarily were designed for packer truck unloading, storage and pre-load compactor charging. Unloading bays 4 and 5 primarily were designed for unloading citizen drop-off vehicles. However, each bay was capable of accepting either vehicle type.

The transfer station design and construction also included: in- and out-bound vehicle weighing; one-way (clockwise) flow of drop-off vehicles; one-way (clockwise) flow, parking and loading of transfer vehicles; on-site leachate collection, treatment and discharge; and on-site stormwater management.

By 1997, the Springville Transfer Station was processing 200 percent of its initial year planned capacity and was approaching or exceeding its intended peak hourly or daily design capacity for two of its three design parameters: tipping floor storage capacity and pre-load compactor capacity. Vehicle off-loading capacity was not a problem in 1997.

Equipment also needed refurbishing. The initial pre-load compactor had processed its expected 10-year throughput. The compactor's manufacturer estimated the equipment rehabilitation in 1997 to cost 75 percent of its initial 1991 cost, indicating that it was approaching the end of its useful life.

And it was apparent that the compactor's cooling system was inadequate for the high desert environment surrounding Provo. During hot, dry summer conditions, the compactor repeatedly overheated. At least part of this overheating was attributed to the placement of the heat dissipation core directly on the compactor body within the Springville Transfer Station.

Based on these problems, the city planned its retrofit to alleviate the pre-load compactor capacity shortfall, which would alleviate the storage capacity shortfall for a few years. (Even with the retrofit, the transfer station is expected to exceed its tipping floor storage capacity, and/or its vehicle off-loading capacity by 2005.)

Although some of the cooling systems' heat build-up could be dissipated by spraying the core with water, the core and its cooling fluid reservoir were moved into a separately conditioned clean room. To do this, the district had to detach the cooling core, pumps and reservoir from the compactor body, then reattach these processes outside the transfer station building.

Retrofit Design and Construction

The SUVSWD solicited bids for the retrofit and eventually decided on HDR again because it had constructed the original transfer station. After soliciting bids from two manufacturers, the district also selected an updated compactor similar to its original model.

Approximately 8 weeks before the new compactor's scheduled delivery, the district shut down the old compactor and the contractor removed it. Concurrently, SUVSWD began lift-and-load operations at the transfer station.

Lift-and-load is less efficient than pre-load compaction, which required district staff to load 15 percent more transfer trailers and required 40 percent more time per day to process its waste.

The contractor then began constructing the transfer station addition that would house support equipment for both compactors. It also began reconstruction of the foundations in Bay 1 to accept the new compactor and began demolishing and reconstructing the push floor at the throat of the compactor in Bay 1.

The new compactor was installed into Bay 1, and about 12 weeks after construction began, SUVSWD resumed normal operations.

Then, the contractor began demolishing Bay 2's floor and constructing new foundations to support the old compactor in its new location. A new push wall consisting of steel structures that could be removed for lift-and-load operations also was constructed for Bay 2.

Meanwhile, the district rehabilitated the original compactor by replacing worn steel, platen and other components at a cost of approximately $300,000. Then, the rehabilitated compactor was installed in Bay 2.

The retrofitted facility now is more efficient and reliable because the old compactor became the backup to the new unit.

SUVSWD admits that the retrofit required some fairly heroic efforts from its employees, who put in mandatory overtime for more than 12 consecutive weeks. But because the Springville Transfer Station had been designed with growth and expansion in mind, the district was able to install the second compactor without much difficulty and was able to complete the retrofit without having to refuse any solid waste.

The retrofitted Springville Transfer Station is expected to meet the South Utah Valley Solid Waste District's waste handling needs until a second transfer station is constructed in the area in 2005, approximately seven years after the latest retrofit.

Richard Henry is manager of the South Utah Valley Solid Waste District, Provo. Dick Sprague and Dwayne Muff are vice presidents for HDR Engineering, Omaha, Neb.