By Bradley Kelley, GBB Senior Project Engineer
In June 2020, operations began at the Davis Material Recovery and Transfer Facility owned by the Wasatch Integrated Waste Management District, in Layton, Utah. The new state-of-the-art facility recovers valuable resources from residential waste and commingled recyclables generated by the 370,000 residents served by the District.
Waste is processed in a highly mechanized system that recovers recyclable materials for sale to market. Materials currently recovered for recycling include clean cardboard, aluminum cans, empty steel cans, and plastic bottles (#1 and #2). Paper and plastics (#3 through #7) are recovered to create an engineered fuel that can be used by industrial sources to offset the use of coal. Organics, such as food waste and grass, are concentrated and can be used as feedstock for anerobic digestion that generates renewable natural gas. Remaining residue from the facility is transferred to a regional landfill, which extends the life of the local landfill.
While this successful operation is impressive, the journey leading to one of the industry’s newest mixed waste processing facilities is of particular interest to industry professionals. Let’s peak behind the curtains!
Looking at Possibilities
The District provides solid waste management services to two Counties and 15 member communities, managing approximately 340,000 tons per year of Municipal Solid Waste, and exercising ownership of the new MRF, 2 landfills (local and an alternate 80 miles away), a green waste recycling facility, a thrift reclaim store, and a household hazardous waste and electronic waste recovery facility. In 2017, as the District’s waste-to-energy (WTE) facility was due for major upgrades, the district learned that the steam contract from the WTE facility would not be renewed. With this loss of revenue, the decision was made to close the facility, leading to a much higher fill rate for the landfill, which was due to reach capacity within 20 years. Due to the need to reduce landfilling and increase material diversion, the District evaluated its options and asked GBB to perform a feasibility analysis — with preliminary layouts, costing scenarios and financing options — for developing one of the following:
- Transfer station to move materials to a regional landfill
- Transfer station with a mixed waste processing facility to recover recyclable commodities
- Transfer station with a mixed waste processing facility to recover recyclable commodities and produce a cement kiln fuel
Procurements are not without challenges and require extensive planning, intense focus, and a tireless effort from all stakeholders. After deciding to proceed with the development of a transfer station with a mixed waste processing facility to produce recyclable commodities and cement kiln fuel at the site of the old waste-to-energy facility, the rigorous procurement process, approached from a strategic standpoint, was initiated. Individuals with complementary expertise came together to form the RFP team. Various contracting approaches were considered — including contracting each step separately; design/build; and design/build/operate – and selection criteria were discussed and set forth. The RFP document was then structured to encourage proposers’ participation and creativity to develop a versatile and flexible system.
Once the proposals were thoroughly evaluated by the team, a second independent opinion was sought to ensure that the selected system:
- Fulfilled the needs of processing and recovering materials
- Created the appropriate outputs
- Avoided unaddressed design issues/bottlenecks
- Identified and addressed potential hazards/confined spaces
- Included adequate maintenance access
As part of the final contract development process, negotiation points included factors such as payment schedules; performance guarantees; testing protocols; spare parts inventory supplied with system; break‐in/startup support period; construction sequencing; performance schedule; liquidated damages; and insurance.
From Signed Contract to Start-up
Once the winning vendor team was selected and the contract finalized, time was required to create the final conceptual design that was to be the basis of the engineered design, including the necessary details not present in the proposal design. Final permitting for each stage of the process was addressed, along with other key design considerations such as infrastructure needs; traffic, scales, and fire suppression considerations; and maintenance needs. Agreements for incoming materials had to be reworked as necessary while offtake agreements for residue, fines/organics, recyclables, and fuel had to be identified and acquired. All in all, when the facility was completed, 39 change orders – 5.5% of the original contract – were necessary for items such as snow drift modifications; additional site grading; additional OCC transfer conveyor needed, etc. This is a very reasonable change order amount, and the installation and start-ups were very smooth and timely, mostly due to the level of discussion and time reviewing the engineering concept design prior to moving into the construction phase. It is easy to feel that no progress is being made at that time in the process, but it is imperative to allow proper time and discussion when the equipment is still a line in a computer and not a steel structure connected to concrete.
Team Training, Punch Lists and Final Testing and Commissioning
Ultimately, the employees had to be trained in the new facility with a focus on safety, maintenance, and equipment operations. Prior to officially opening the facility, a robust 4-day system test, with statistical analysis, was performed by an independent third party to verify that the equipment performed as was promised.
During the COVID-19 pandemic, the District performed key public education activities that included a revamped website with new education material; production of video and graphics highlighting and explaining the new facility and its capabilities; and development of tours and an education center.
Preliminary Results and Next Steps
After just over a year of operations, the new facility is a success with up to 700 tons per day transferred and the processing equipment running at about 85% to 90% of availability. Diversion statistics include:
- Producing high quality recyclables moving to market: 3.5% diversion
- Producing well-accepted feedstock for cement plant: 7.5% diversion
- Potential for 20% to 40% diversion on organics offtake – still working on it!
Future projects may include:
- Mattress processing
- RDF densification
- Organics/fines outlets
- Potential source for alternative conversion experimentation with Universities or other entities
The eventual goal is to reach close to 50% diversion from landfill with the organics being used to create renewable natural gas, and additional materials recovered for recycling or to be included in the kiln fuel. The organics processing is to occur at another site that has not been ready for this material at the time of this blog entry, but steps are still being made to have the new location as an offtake for the organics/fines.
Increasing the fuel and recycling recovery will likely require some equipment additions or modifications, as the fuel requirements were a big unknown going into the design of the facility. It is hoped that this system can help prove to other coal utilizers that a viable and useful coal alternative can be produced at these facilities. Another unknown was the composition of the single stream recyclables that are also processed at this facility, which had a lot more cardboard than anticipated. It is recommended that a characterization study be implemented prior to designing one of these facilities to make sure the system can handle the anticipated materials.
The District now has a modern facility that it can be proud of and that provides residents the services and results they deserve. See the facility in this 9-minute tour produced by the District: