BioCycle May 2006, Vol. 47, No. 5, p. 19
The Transportation Office in Portland, Oregon integrates its role in street maintenance operations with full-scale recycling to reduce disposal costs and encourage the reuse of materials.
THE PORTLAND Office of Transportation’s Bureau of Maintenance (BOM) in Oregon has embraced the challenge of developing cost-effective methods to recycle materials generated when performing street maintenance operations. BOM’s recycling program is conducted at the Sunderland Recycling Facility, and is designed to meet Portland’s sustainability goals by: Lowering fees and hauling costs for the disposal of material; Reducing the need to purchase virgin rock; and Offsetting operating costs through the sales of compost and recycled products.
Since the mid-1980s, BOM employees have been experimenting with various techniques to economically recycle materials such as leaves, concrete, asphalt and street-sanding rock. In 1997, BOM purchased a 20-acre site committed to this recycling effort. At present, 30,000 to 50,000 cubic yards of material are processed annually at the facility. City crews use this material for maintenance and repair projects. Some of the recycled material, such as leaf compost, blended soil, and crushed rock, is sold to the public as part of BOM’s outreach program.
Currently the following processes are conducted at the Sunderland Recycling Facility: Leaf composting, asphalt crushing, concrete crushing, and street sanding material cleaning. BOM’s recycling program has been so successful that in October 2004, an additional 14-acre parcel of land adjacent to the existing site was acquired. This second property adds capacity for current programs and provides opportunities for savings and revenue for new programs.
The next waste that BOM will process for reuse is street sweeping debris. Portland generates approximately 25,000 cubic yards of street sweeping debris each year. Disposal of this material in a landfill impacts landfill capacity, and costs hundreds of thousands of dollars in transportation and disposal fees. In the summer of 2005, BOM partnered with other local transportation agencies to conduct a pilot project to determine treatment and reuse options for street sweeping debris. The results of the study are currently being reviewed, and a second project focused on the reuse aspect is being developed.
The leaf collection program begins the first of November and runs through December. This program focuses on picking up the leaves that fall on to the streets. This helps reduce slippery road conditions, increasing the safety of motorists, pedestrians and bicyclists.
Street leaf removal also reduces localized flooding caused by clogged drain inlets. The city infrastructure also benefits from the reduced amount of leaves entering the storm drains.
Leaves are brought into the facility by city crews and placed in windrows. Frequency of pile turning, done with a Scat windrow turner, is determined by temperature monitoring with Reotemp probes. Moisture is monitored daily as well. A trommel screen is brought to the yard during the summer to screen finished compost. Overs are mixed back into the windrows with the fresh material.
Anywhere from 15,000 to 25,000 cubic yards/year of leaves are composted at the Sunderland Recycling Facility. Finished compost is sold for $16/cubic yard. The site also makes blends with other by-products recovered there, including sand and soil.
Asphalt and concrete are processed into rock, which is used for city infrastructure maintenance projects. Asphalt processed at the facility is generated by either a crew that is repairing failures on local streets, or by a crew which mills (grinds down) streets to prepare them for a new wearing layer of asphalt.
The asphalt generated by the repair crews is usually oversized and requires some downsizing to make it usable for the production of rock. The asphalt is mixed with concrete as it is fed into the crushing machine to ensure an end product that meets construction specifications.
Minor amounts of asphalt grindings are brought in from the city’s Milling Crew. These are also used in the production of many different construction materials.
Concrete chunks brought to the facility are downsized using an excavator with an attached demolition tool. The material is mixed with asphalt as it is fed through the crushing machine to make 1 1/2-inch minus aggregate.
Asphalt and concrete recycling provides the raw materials to make aggregates that are reused by the city. The city generates much more waste asphalt than concrete. To maintain the correct blend of material to meet specifications, some concrete is accepted at the facility from private contractors and citizens. The facility currently has the capacity to recycle approximately 40,000 cubic yards/year of concrete and asphalt-laden materials.
Most of the asphalt grindings generated are sold to local asphalt plants to be used in recycled asphalt product (RAP) mix designs. The city follows Oregon Department of Transportation Specifications for materials and is currently allowed to use up to a 30 percent RAP mix design.
Recycling the asphalt grindings saves money for the Bureau of Maintenance in a couple of different ways. The Bureau avoids the disposal costs of a landfill and the material does not use up valuable space. It is operating a sustainable program that reuses nonrenewable natural resources, and saves money on the end-user product for our paving operations by using the RAP mix asphalt.
STREET SAND RECYCLING
Sand applied to the city streets during snow and ice operations is collected with street sweepers at the end of each event. The quantity of sand used and collected varies greatly each year.
The sand collected from the city streets is processed to separate out trash and other debris, leaving behind the street sanding material, a one-quarter inch minus rock. The rock is transported to the facility where the material is run through a CEC Screen-It screen plant that separates the reusable rock from the dirt. Finished product is taken back to storage piles located around the city for use in the next snow and ice event.
Sand recycling capacity of the Sunderland Facility is great enough that the city is able to accept sanding materials from other local jurisdictions and to process it into a reusable product. The dirt or fine sand removed from the street sanding material can be mixed with soil to make a sandy loam, which is used for backfill behind new concrete curbs installed by city crews.
PROVIDING SERVICES TO CITY BUREAUS
Currently, the Sunderland Facility receives leaves from Portland’s Bureau of Housing and Community Development, Water and Parks Bureaus, as well as neighboring cities of Hillsboro, Gresham and Lake Oswego. Concrete and asphalt come in from the Bureau of Environmental Services’ Materials Testing Lab, the Water Bureau and the City of Vancouver. Finished product such as composted leaves are utilized by the Parks, Water and Environmental Services Bureaus, Portland Public Schools and the Columbia River Correctional Institute. Processed concrete and asphalt are also used by these agencies.
The 20-acre site, of which 12 acres are used for recycling purposes, also has become a showcase for alternative energy sources. A 10-kilowatt wind turbine on a 100-foot lattice tower was recently constructed and provides power to a city building used for office and meeting space. Solar panels will be used to provide power to the scale house (Summer 2006). The Facility’s office includes “green building” and energy efficiency techniques. The facility also hosts equipment and erosion and sediment control training.
The site was also designed to incorporate water quality techniques. In addition to landscaping with native plants, it includes a drainage system and detention pond facility, constructed wetlands, and a water quality swale.
Sunderland Recycling Facility helps the city to be fiscally prudent and responsible with taxpayer funds. Financial benefits include reducing disposal costs by eliminating tipping fees for many materials, reducing the need to purchase virgin aggregates, and offsetting some operating costs through the sale of leaf compost and aggregate material.
Jill Jacobsen is Program Manager for the Portland, Oregon Office of Transportation’s Bureau of Maintenance. E-mail Jill.Jacobsen@pdxtrans.org. The Sunderland Recycling Facility is located at 9325 NE Sunderland Avenue in Portland.
May 24, 2006 | General
Mixing And Matching At The Sunderland Recycling Facility
BioCycle May 2006, Vol. 47, No. 5, p. 19