OII Landfill and Casmalia Resources Superfund Site

Scope of Services Provided by AES

OII Landfill – AES has been continuously working on this 140-acre Superfund site from its original closure design and closure construction completed in 2000 through current remedial construction of slopes. Our firm was an integral part of the Design-Build team for the $100M final closure and the 30-acre North Parcel. AES professionals provided solid waste engineering, site investigation, design, construction management (CM) support and CQA services during the design, construction, and post-construction phases of closure of this federal superfund site. The site location, adjacent to residences, commercial properties and the 60 Freeway, and featuring relatively high and steep landfill slopes adjacent to the freeway (250-foot high, 1.5:1 slope), presented some unique challenges for the design and construction of final cover.

Our scope of services has included:

• Design Services – AES performed solid waste and geotechnical engineering services for various design phases of the final closure and post-closure maintenance plans, design report, and plans and specifications for construction.
• Unsaturated Flow Modeling – To support the design and approval of the alternative final cover, AES performed computer modeling of the alternative evapotranspirative cover, and obtained the unsaturated hydraulic characteristics of potential cover soils. Based on the models, AES developed and implemented a moisture monitoring system and monitoring plan incorporating Time Domain Reflectometry (TDR) probes.
• CQA Services – AES performed a full range of geotechnical CQA services during construction, including field and laboratory testing on earthworks and geosynthetics, borrow site evaluation of over 25 potential borrow sites, and geotechnical monitoring of approximately 1 million cubic yards of final cover placement.
• Regulatory Agencies Coordination – AES prepared reports and participated in presentations and meetings with regulatory agencies including the U.S. Environmental Protection Agency (EPA), U.S. Army Corps of Engineers, DTSC, RWQCB and Caltrans.
• Post-Closure Maintenance – During the post-closure period AES performed annual inspections, provided recommendations for slope, cover and bench road repairs, monitored and evaluated the TDR moisture readings, performed CQA services, and prepared annual monitoring and inspection reports.
• Long Term Performance Modeling and Sustainability Evaluation – AES performed modeling of the long-term performance of the landfill cover system and slopes to estimate long-term maintenance and major repair costs over the next 60 years. Long-term performance modeling included evaluation of settlement, lateral displacements and deformed shape of steep slopes using finite element program SIGMA/W.

Casmalia Resources Superfund Site – AES provided CQA services for the first phase of the final closure of the Central Drainage Area (CDA) Cap. The CDA Cap consisted of an RCRA-compliant cap consisting of from bottom to top, GCL, HDPE Geomembrane, Drainage Geocomposite, Biotic barrier and Protective Soil Cover. The cap was designed to tie into the existing landfill caps and completely cover the area extending from the downslope end of the four previously capped landfills to the southern (downgradient) boundary of the impacted area. The CDA cap covers a footprint previously occupied by several waste containment ponds. The CDA Cap covers approximately 25 acres and finish grades range from about 450 to 640 feet MSL. The earthworks for CDA Cap grading included approximately 275,000 cy of engineered foundation fill, 40,000 cy of cut, and 85,000 cy of vegetative cover soil. AES’ CQA services included:

• Review of Contractor submittals for conformance with specifications
• Review of MQC data for geosynthetic materials
• Performing conformance tests on soils and geosynthetics materials prior to their use
• Providing field CQA observations and testing of: earthworks activities including clearing and grubbing, material processing, engineered fill placement, subgrade preparation and vegetative soil layer placement
• Field CQA services for geosynthetics installation including GCL, geomembrane, geocomposite drainage layer and geonet (biotic barrier)
• Field CQA services for surface drainage and erosion protection including subdrains, CMP storm drains, concrete, and geoweb lined channels, Turf Reinforcement Mat (TRM) lined drainage swales, and drainage and erosion control improvements
• Development and maintenance of daily written and photographic documentation of construction progress and CQA activities
• Preparation of a Construction Certification Report for submittal to EPA