Geotechnical Investigations, Design Support & CM/CQA Services for Unit 2 Phases 3‑2, 4, and 5‑1 Composite Liner Expansions

The San Timoteo Sanitary Landfill is a 366‑acre Class III landfill located in the southwest corner of Redlands, California, with 114 acres permitted for refuse disposal and an average intake of 2,000 tons per day. Verdantas provided comprehensive geotechnical investigations, design support, and Construction Management/Construction Quality Assurance (CM/CQA) services for multiple major expansion phases of Unit 2, enhancing landfill capacity, stability, and regulatory compliance.

Unit 2, Phases 3‑2 and 4 – Composite Liner Expansion

Verdantas supported a large‑scale excavation and liner installation program involving 2.5 million cubic yards of earthwork and buttress construction, along with 16 acres of composite canyon bottom and side slope liner. Key work included:

• Geotechnical investigations using drilling, coring, and downhole geophysical logging to characterize geologic conditions and inform excavation and buttress design.
• Static and seismic slope stability analyses for 1.5H:1V cut slopes reaching up to 250 feet in height.
• Evaluation of onsite soils for their suitability as a low‑permeability subgrade layer supporting an alternative liner system.
• Development of an alternative composite liner system featuring a 1‑foot low‑permeability layer and geosynthetic clay liner (GCL) encapsulated between dual HDPE geomembranes.
• Preparation of design documents and a Technical Memorandum for regulatory agency submittal.
• CM/CQA oversight for liner construction, 480,000 cubic yards of buttress fill, leachate collection and removal system (LCRS), operations layers, drainage structures, stockpiles, access roads, and associated site improvements.
• Preparation of a complete As‑Built CQA Report for agency review.

Unit 2, Phase 5‑1 Expansion

Verdantas also provided CM/CQA services for an additional 11 acres of liner (7 acres of composite side slope liner and 4 acres of base liner) involving 188,000 cubic yards of excavation and buttress construction. Work included CQA oversight for approximately 1.0 million square feet of geosynthetics installation and preparation of a regulatory‑ready As‑Built CQA Report.

Client Commendations

The County of San Bernardino commended Verdantas for technical quality, responsiveness, professionalism, and consistent on‑schedule deliverables across more than a dozen landfill projects—highlighting Verdantas’ deep expertise in landfill engineering, liner systems, and regulatory compliance.