Remediation and Restoration (Remedial Actions): Concord Naval Weapons Station, CA

Landfill Cap Construction, Concord Naval Weapons Station, CA
Landfill Cap Construction, Concord Naval Weapons Station, CAOTIE executed a $4.9M FFP task order for construction of a 15-acre landfill cap, installing and maintaining stormwater and erosion prevention controls, and site restoration at Concord Naval Weapons Station, CA. This was a challenging construction project with multiple stakeholder needs and unexpected site conditions that required multiple design modifications to ensure safety and avoidance of MEC materials.
The remedial action included the construction of landfill gas probes, construction of a landfill cover with subsurface MEC adjacent to marshlands. Surface and partially exposed MEC items were consolidated for demilitarization and final off-site disposition.
While excavating and consolidating landfill debris, OTIE encountered MEC which resulted in a pause-in-construction. Based on the landfill conditions and discovery of MEC, the Navy modified the landfill design, and OTIE developed an alternate method of construction. The modified design approach required a “non-intrusive” effort in which landfill debris would not be excavated for consolidation. The new design also called for an expansion of the landfill footprint and an increase in cap foundation and topsoil volumes. OTIE provided construction that required a 20% increase in the landfill footprint and a nearly 3 foot thicker cover from the original design.
OTIE resumed delivery of foundation materials. The OTIE construction team monitored and tracked the mass of materials delivered by truck. More than 8,000 truck trips delivered 180,640 tons of foundation layer material. This is an increase of 21,500 tons more than the originally targeted design mass.
OTIE coordinated with the Navy BRAC and IRP teams, as well as the Army tenants, for delivery of landfill foundation material during the 2008 construction season and to schedule construction of the geo-synthetic liner and placement of the top-soil layers during a 2009 construction season.
During construction, OTIE continued to perform MEC inspections for lower lifts of the landfill cap foundation placement and all work along the perimeter of the cap to ensure safety during construction.
Client Name: NAVFAC Southwest

Location: Concord Naval Weapons Station, CA

Contract Value: $4.9M

Project Features:

    • Resolved public and environmental issues and concerns through proactive community outreach.
    • Encountered unexpected MEC which required design changes
    • Successfully addressed multiple stakeholder needs and changing site conditions.