Landfill Energy – Permitting, Design, Closure and Construction, Prince William County, Virginia

scs engineers landfill monitoring permittingSCS Engineers provided design, construction plans, specifications and construction quality assurance (CQA) support for a landfill in heavily populated Prince William County.

Among these services, we instituted a gas collection and control system (GCCS) to serve the project’s goals.

Landfill Gas Engineering Services

  • commercial feasibility of recovering and utilizing LFG, with an emphasis on markets and the economics of recovery
  • on-site LFG migration control investigation and LFG remediation plan
  • model LFG emissions in compliance with EPA’s NSPS
  • GCCS Design Plan and Landfill Gas Management Plan
  • GCCS expansion and improvements
  • LFG treatment skid & LFG-fired heaters
  • Title V and GHG reporting, Title V operating permit renewal application and
    permit to construct & operate candlestick flare
  • utilization of treated gas in animal crematory
  • controlling potential LFG migration through leachate pipes.
  • designed a small, low-cost subslab extraction system for the garage and office building and provided methane detectors/alarms. (County staff constructed the control system under SCS oversight.)

Permit Modifications

SCS Engineers undertook Part A permit amendment services to modify the facility boundary due to changes in property limits. Part B amendment efforts included a 115-acre expansion at the existing site.

This effort included HELP and Multimed modeling of an Alternative Bottom Liner (ABL) to reduce construction costs. The ABL was permitted and consists of two layers of 60-mil HDPE geomembranes with a geocomposite clay layer (GCL) in between. Landfill phasing plans were also included in the permit application.

Landfill Construction Bid Documents

Construction plans included multiple landfill cells that utilized the ABL, as well as overfills onto the existing landfill, collection pipes at the cell bottom along with perimeter HDPE leachate collection manholes, an HDPE leachate pump station.
Construction Administration and CQA.

Bid assistance, contract addenda, bid review, recommendations regarding award, review of contractor submittals, resident engineering, construction oversight, and preparation of a certification report to the Virginia Department of Environmental Quality (VDEQ).

Oversight also included an active LFG collection system providing fuel to a three-megawatt power plant.

Closure Plans

Our services addressed technical operations and cost evaluations of alternative cover systems for the areas of the landfill where overfilling will occur in the near future and in the long term. SCS prepared written closure/post-closure plans and construction bid documents for landfill closure.

Solid Waste Budget

An enterprise fund finances the county’s solid waste program. Annually, SCS reviews the County’s budget in accordance with the requirements of the Landfill Revenue Bond Covenant of the Virginia Resource Authority. The reviews examine the expenses incurred, revenues earned, operation loss/profit, et cetera.

Furthermore, we review current-year budgets and projections for long-term costs of future development, in addition to closure and post-closure costs for Phases I, II, and III.

Groundwater Consulting

SCS performed a review of existing geologic and hydrogeologic data, including Part A permit submissions and groundwater monitoring data. Upon completion of the review, SCS recommended that four additional wells be installed at the site in order to monitor the older sections of the landfill and the newer section separately.

  • Provided statistical analysis of existing data for compliance with regulations.
  • Exceedances in downgradient wells were identified during final detection monitoring.
  • Provided statistical analysis of the data from semi-annual sampling under the assessment monitoring program hydrogeological evaluations, and preparation of annual reports for submission to VDEQ.