By Wendy Wert
Sewer Leaks Editor
On March 22, 2007 the Los Angeles Basin Section (LABS) of CWEA hosted a dinner and training meeting at Taix French Restaurant in downtown Los Angeles.
John Robinson presents at Taix in Los Angeles John Robinson of MWH discussed key design, permitting and construction features for the largest fully enclosed indoor composting facility in the world. With limited biosolids application sites in California, Inland Empire Utilities Agency and Los Angeles County Sanitation District formed a Joint Powers Authority in order to construct the facility – the Inland Empire Regional Composting Authority.
A team of consultants worked with IEUA and LACSD to prepare the preliminary design, permitting, final design and construction support to build a 150,000 ton per year composting facility in San Bernardino. Half of the facility capacity (75,000 TPY) is allotted to each partnering agency. This state-of-the-art compost manufacturing facility cost approximately $55 million in construction fees to retrofit an existing 400,000 square foot building.
Odor concerns were a high priority both for the operators of the facility and air quality regulators. The South Coast Air Quality Management District (SCAQMD) established a number of rules that govern air turnovers in a composting facility and odor control. The SCAQMD requires six air changes per hour, partly to control odor.
However, to ensure sufficient odor dilution, this baseline was doubled to 12 air changes per hour for the active composting area of the facility. In this way the facility exceeds the regulated standard. To accomplish this standard a 150 foot long 8 foot high biofilter and 120 process fans supports 813,000 cfm of air scrubbing.
An aerated static pile (ASP) was selected to manufacture exceptional quality compost. The aeration system is operated 90% of the time in the negative mode and the remaining 10% in the positive mode. The process is designed to achieve 21 days of active composting and 28 days of curing. Mixing at the facility will be accomplished using a continuous flow pug mill with one dedicated backup for redundancy. 110 cubic yards of active compost material will be processed by the system each day. Materials will move through the facility via conveyors and 6 front-end loaders (John Deere) with cubic yard buckets.
The innovative project will recycle water from an adjacent IEUA wastewater treatment plant (RP4) for on-site non-potable uses such as vehicle washing, landscape irrigation, and process water applications such as biofilter wetting.
Permitting the project was on the critical path with respect to schedule. The IEUA has developed a program Environmental Impact Report (EIR) for all of their facilities. An amendment to the program EIR served as environmental documentation for this project.
A conditional use permit (CUP) was required for the project. The SCAQMD permit required 18 months to finalize. In addition CIWMB and RWQCB permits were also required. John advised that “there is no such thing as over communicating with the regulators.” The facility will be able to process biosolids at a cost of $65 to $80 per ton.