Alleviating Growing Pains

ST. LUCIE COUNTY, FLA., a scenic region on the Treasure Coast, is considered paradise by many of its residents. The combination of beautiful scenery and temperate weather inspires thousands of people each year to make the area their new home. Such an influx has given the county the distinction of being the second fastest-growing region in the country and has prompted officials to ensure that its solid waste infrastructure can accommodate the population explosion.

“No one could have anticipated that we would [see an] increase in population from 2 to 3 percent annually to 10 percent seemingly overnight,” says Leo Cordeiro, the county's solid waste manager.

Real estate and retail markets traditionally thrive when an area experiences a population boom, but such a dynamic can mean big problems for a local government's solid waste system. To avoid overburdening its 330-acre Glades Cut-Off Road landfill and creating the need for new landfill disposal cells, St. Lucie County built a construction and demolition (C&D) processing facility as well as a baling and recycling facility. Together, the structures have extended the landfill's lifespan by 20 years by expanding the amount of recyclables recovered from the waste stream and increasing the density of disposed waste.

The $3.6 million C&D facility receives roughly 600 tons of material each day. The material is sorted in the tipping area by a grapple operator and by county employees using manual sorting along with magnetic and air separation technologies. The recyclable material is sold to vendors. St. Lucie County recovers and sells cardboard, ferrous metals, aggregate, wood and tiles, among other materials.

“Why bury 600 tons a day when you can cover your costs with the sale of the material? Cordeiro asks.

The non-recyclable material is ground up and used as alternate landfill cover, Cordeiro says. Approximately 10 percent of the C&D waste that the facility processes each day is used to cover the Class I bales and for sideslope stabilization, he adds.

Meanwhile, the $10 million baling and recycling facility receives about 2,500 tons of household, commercial and industrial waste (Class I) per day. After being sorted on the center's 55,000 square foot tipping floor, the non-recyclable materials are compressed into dense bales and then transferred to the landfill for disposal.

The baling and recycling facility delayed the need for additional landfill cells by increasing the density of the landfilled material. The bales produced at the center allow solid waste to be buried at the landfill at a density in excess of 1,800 pounds per cubic yard. When the county used a traditional compaction process, material was buried at a density of 1,100 pounds per cubic yard.

By baling material at the facility rather than compacting it at the landfill, the county also has reduced fuel consumption at the Glades Cut-Off Road site. The county also is experiencing savings in operational costs related to landfill cover material, landfill gas generation and odor issues.

Once the landfill does close, the baling facility will be converted into a transfer station, saving the county millions of dollars in capital costs that would be required to construct a new station.

As the market for recycled goods continues to grow, the two facilities will provide the county with a consistent source of revenue. In 2004, the baling facility alone sold approximately $500,000 of recyclable materials, which allows St. Lucie County to hold down its municipal disposal fees. Before the facilities were built, the county earned roughly $10,000 a year from such sales. The county previously relied solely on its curbside recycling program.

When an area experiences a significant population boom such as St. Lucie County has in recent years, the strain placed on local solid waste infrastructure often is overlooked by the general public. Solid waste officials, however, know what a serious challenge responding to robust population growth can be.

With the C&D sorting center and the baling and recycling facility, St. Lucie County has met its considerable challenge in way that has allowed the local government to extend the life of its existing landfill and thereby preserve open and residential space in the area.
Eric Grotke
Principal Engineer, CDM
Vero Beach, Fla.