Colton Sanitary Landfill | Projects

The Colton Sanitary Landfill encompasses 113 acres, with 88 acres historically used for waste disposal. The County originally planned to close the landfill using a 4‑foot soil monocover requiring approximately 600,000 cubic yards of material, but insufficient onsite soil availability prompted a redesign. Instead, the County selected Agru’s ClosureTurf® system—a synthetic, turf‑reinforced geosynthetic final cover—making this the largest ClosureTurf® installation in Southern California, constructed on steep, highly visible slopes.

Verdantas provided comprehensive Construction Management (CM) and Construction Quality Assurance (CQA) services for the landfill’s final closure, ensuring regulatory compliance, long‑term performance, and technical excellence throughout construction.

Final Cover CQA Services

Verdantas oversaw installation of the engineered final cover system, which consisted of a 50‑mil LLDPE geomembrane barrier layer topped with Watershed Geosynthetics’ ClosureTurf® and a sand‑infill ballast layer for wind protection. CQA responsibilities included:

Subgrade preparation and engineered fills for the cover system.
Review of Manufacturer Quality Control (MQC) documentation and performance of conformance testing for all geosynthetic components.
Oversight of installation of approximately 4 million square feet of LLDPE geomembrane and 4 million square feet of ClosureTurf® across 80 acres of 2:1 slopes and the top deck.
Inspection of drainage improvements, onsite road construction, and gabion wall installations.
Preparation of the As‑Built CQA Report for regulatory agency review.

Construction Management Services

Verdantas provided full CM support, including contract administration, cost and schedule control, material quantity verification, progress payment review, contractor submittal processing, RFI and change order responses, weekly construction meetings, and coordination with the County and design engineers.