Appendices to Integrated Resources & Solid Waste Management Plan - Dec 2009

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HAWAII COUNTY MECHANICAL - BIOLOGICAL TREATMENT FACILITY CONCEPTUAL DESIGN Amendments It is a normal practice in composting and MBT facilities to recycle a portion of the oversized material screened from the finished compost back into the initial feedstock mix. In addition to inoculating the bacterial population, this practice can be used to help adjust moisture levels, nutrient requirements, and porosity. The amount of oversized material recycled back into the mixture depends on a number of factors, including particle size, moisture of incoming feedstocks, and amount of non - organic materials present in the oversized materials. Facility Capacity The two MBT facilities are intended to process MMSW collected through recycling and transfer stations, and MMSW delivered direct to the facility by collection trucks. The waste stream quantities provided previously in this technical memorandum serve as the basis for determining the required capacity of each facility. It is proposed that the facilities be developed in two stages. The first stage would include development of facilities with a capacity sufficient to handle annual waste tonnages during an initial ten year period. A second phase of development would be initiated in Year 7 based on a reassessment of waste quantities, and also an assessment of the performance of the Phase 1 facilities. This phased approach has the advantage of lowering the required initial capital investment, allows for the potential success of zero waste programs, and allows for future advancements of technology in this field. Initial design capacities of the two facilities, which are based on projections of overall waste tonnages for the year 2022, and the composition of the waste stream, are as follows: • West Hawaii MMSW facility: 134,000 tons per year (515 tons per day based on 5 -day week). • East Hawaii MMSW facility: 82,000 tons per year (315 tons per day based on 5 -day week). A breakdown of the waste tonnages which form the basis of the facility capacities is provided in Exhibit 33. Feedstock Receiving It is expected that MMSW would be delivered to the facilities directly from recycling and transfer stations, and from collection vehicles operated by private sector collection firms. As a result, the facilities would be required to accommodate a range of waste collection vehicles, including rear and side load trucks, front -end trucks, roll -off trucks, and walking floor trucks. Materials that are obviously not compatible with the MBT process (e.g., concrete and asphalt, treated wood waste, segregated household hazardous waste) will bypass the facility and be sent directly to the appropriate handling or disposal facility. Since material would be received throughout the year, maintaining year -round access to the facilities for feedstock deliveries is required. 3 These tonnages are based on initial forecasts made during development of the IRSWMP Update. The final forecasts are lower than shown above, thus, 10 -year plant capacity needs and capital costs would be lower than shown in this document.