The phrase "transfer station" just doesn't do justice to ma-ny of today's multi-purpose solid waste facilities. For a variety of reasons, many MSW operators need to conduct several solid waste functions in one facility.
For example, public works officials in Ketchikan, Alaska, developed a progressive concept which required a single facility to transfer solid waste; receive, process and ship re-cyclable materials; temporarily store household hazardous wastes (HHW); and dispose of regulated foreign gar-bage from the cruise ships.
Ketchikan, a town and borough of 15,000 people (in addition to the influx of tourists during the summer cruise ship season), is approximately 800 miles northeast of Seattle on Re-villagigedo Island in Southeast Alas-ka. The city's landfill is located im-mediately outside the city limits. On an average day, the landfill receives 50 tons of waste; during the summer months, the average increases to more than 100 tons per day.
Ketchikan officials wanted to maximize the city's limited landfill space and minimize the transportation costs for exporting waste to an off-island landfill. These goals, in addition to wanting to discourage bears from foraging at the landfill, led design engineers to include a solid waste baler in the 20,000 square foot, $2.5 million facility.
The 1.5 acre Solid Waste Recycling and Handling Facility (SWRHF) was carved out of rock at the local landfill site. Since SWRHF will receive and bale all of the city's solid waste before transferring it to the landfill, it seemed logical to site the facility adjacent to the site. In addition, the public was already accustomed to bringing their waste to the landfill.
The city's public works staff had to be creative in order to fit a multi-purpose facility onto a one acre. In addition to needing flexibility for the future, the design criteria also in-cluded: waste transfer capacity; tipping floor sizes; recyclables receiving, processing and storage capacity; customer vehicle maneuvering re-quirements; and prevailing wind/ weather patterns (see diagram on page 44).
The site plan also was generated in concert with the floor plan. Proc-ess efficiency and customer safety were the main concerns when the material flow pattern was designed. Processing moves the solid waste, recyclables, marpol waste and HHW from the receiving area, across the width of the building and then out the ends of the building for disposal or marketing. The waste streams rarely cross paths.
Customers arrive from the west and pass over the vehicle scale. The scale computer system notes the type of waste, records a gross vehicle weight and stores the information along with a customer number. After the information is processed, the customer proceeds to six waste re-ceiving areas to unload according to their waste type. Next, the vehicle scale records the net weight and calculates the disposal charge.
Solid waste bales are removed from the building in two locations. If the city is using the existing landfill, bales are removed from the east end of the building and a rubber tired forklift transfers the material to the landfill. If the waste will be exported to an off-island landfill, bales are loaded into shipping containers parked at the west-end loading docks. The shipping containers are removed from the loading docks and exit from the southwest corner of the site so that they do not interfere with customer traffic.
Recyclables are loaded into shipping containers at the west-end loading docks and also exit from the southwest corner to avoid customer traffic. Empty shipping containers are kept in a paved area.
MSW is received on the east end through three doorways equipped with roll-up doors to insulate and secure the building. Inside, customers unload their waste onto a flat concrete tipping floor with a 10-foot high concrete pushwall.
The floor stores approximately two days of waste, at an average rate of 50 tons per day. A rubber tired-loader moves the waste from the tipping floor to a Krause Manufacturing bal-er loading conveyor which brings the waste to the baler. Due to the pitless installation, the baler can be repositioned to respond to changes in the marketplace. The conveyor is a four foot wide cleated slider chain belt which inclines to the baler hopper at a 30 degree angle.
The Mosley Machinery Co. baler reportedly bales 15 tons of solid waste per hour, producing 2,200-pound bales. Since this capacity is greater than the rate of waste re-ceipts, the baler operates a portion of the day.
Ejected bales are pushed out a roll-up door with a plastic strip curtain attached to the bottom.
Recycling And Incineration With no formal recycling program, but a strong public interest to initiate one, the facility has been de-signed to receive source separated recyclables, commingled recyclables and materials from a blue bag program. Blue bags can be brought to the same tipping floor as MSW. The bags must be manually tossed over the four-foot barrier which divides the tipping floor. The bags are manually opened at the recyclables tipping floor and the recyclables are gathered for processing.
If source separated materials are received in large loads, they can be dumped onto the recyclables tipping floor until the baler is available. Large loads of commingled recyclables can be dumped onto the recyclables tipping floor and accumulated for processing. Small loads of commingled recyclables can be separated by the customer into separate bins.
The loading conveyor transports the commingled material onto a manual sorting line with six sorting stations: three on each side and an Eriez self-cleaning magnet. From the sorting stations, materials travel in a chute to bins which are underneath the conveyor. The magnet discharges ferrous metal onto a slide chute where it falls into a bin. Remaining materials fall from the end of the belt onto a slide chute and into a bin be-low.
When the sorting line is run in a "positive sort" mode, the materials in the bins are moved by a forklift to the loading conveyor which brings them to the baler. Materials that need to be reduced are sent to the plastics perforator or glass breaker prior to baling. The materials in the bin at the end of the sorting line are treated as MSW.
When operating in a "negative sort" mode, the materials collected in the bins below the sorting stations are treated as MSW; the materials collected from underneath the magnet and at the end of the conveyor are transferred by a forklift to the baling conveyor, plastic perforator or glass breaker.
In an area adjacent to the recyclables tipping floor, white goods are stripped of their compressors and other non-recyclable materials. Next, they are transferred to outdoor storage before being crushed and loaded for shipping.
Weather sensitive recyclables are stored inside the building in an area adjacent to the recyclables tipping floor; the other recyclables are stored in a covered bay at the east end of the building. A forklift conveys the materials to the west loading dock so they can be placed into shipping containers.
Since foreign vessels dock at the Ketchikan port, the Coast Guard re-quires the city to dispose of the foreign garbage or "marpol" waste. Fol-lowing U.S. Department of Agricul-ture requirements, the city uses two modular waste incinerators to burn the marpol waste to an ash or sterilize it. The Advanced Combustion Systems incinerators, which reportedly can burn up to 450 pounds per hour of marpol waste, also will be used to burn the local hospital's wastes.
Marpol wastes enter the facility through the far west roll-up door and are unloaded onto the tipping floor. A rubber-tired excavator with a one-yard bucket is used to load the typically wet waste, with a high food content, into one-cubic yard bins. Once filled, the bins are brought to the incinerators. Automatic tipping equipment empties the bins into the incinerator's feed hopper and pushes it into the combustion chamber with a ram.
To keep the combustion chamber temperature at the desired level, every incinerator is equipped with oil burning lances (one for fuel oil and one for waste oil). Small bins are kept beneath the incinerators to collect the ash. Once the ash cools, it's disposed as MSW.
Ketchikan's SWRHF also includes a year-round collection center for HHW. The east end of the building receives HHW several days a week. A trained attendant identifies the wastes and packs it into a drum with compatible HHW. The full drums are placed in prefabricated steel containers with spill containment sumps and fire protection sprinklers. The storage containers with combustibles also have explosion venting panels. Container storage is available for 33 HHW drums.
Control Systems Odor And Dust Control Systems. The building has 11 wall-mounted ex-haust fans with motor operated louvers for ventilation. The fans can be controlled to target specific dust and odor conditions. When all fans are operating, the air is replaced every six minutes. Washdown hoses are placed at the tipping floor since the facility must undergo routine clean-ups and washdowns.
Wastewater Control Systems. Trench drains along the long axis of the building collect water from the tipping floor and processed wastes.
The tipping floor slab slopes from a high ridge in the middle toward the trench drains, which were positioned to ensure that the water would not travel towards the wastes waiting to be processed. This location also minimizes drain pluggage. In the end, the water discharges directly into the sanitary sewer system.
Noise Control Systems. The waste transfer and processing activities have been enclosed to control noise.
Building Fire Protection Systems. A dry pipe sprinkler system and handheld fire extinguishers have been instal-led. Several fire hydrants are spaced around the site.
Safety. For employee and visitor safety, eyewash stations are located around the building's perimeter.
A two-story administration building houses employee lockers, em-ployee and public restrooms, office space, a lunchroom and a large conference room with viewing windows into the main building.
The facility began operation last summer. The future came sooner than expected when the city council decided to export the city's waste to a regional landfill in Washington. As a result, the city will relocate the baler to the west end of the building to efficiently load the baled waste for export. This change, coupled with uncertain recycling program requirements, have made the Ketchikan Solid Waste Recycling and Handling Facility a challenging operation.