Virgin Islands Waste Management Authority (VIWMA) – Three Landfills Engineering and Environmental Services

US Virgin Islands | 2012 – Ongoing

Scope of Services

  • Closure Design and Permitting
  • Contract Documents, Technical Specifications, CQA Plan
  • Construction Management, Oversight, and Permitting
  • Construction Quality Assurance
  • Bidding Assistance
  • Closure and Post-Closure Care Cost Projections
  • Accounting Services Cost Estimate Review
  • Financial Auditing
  • Grant Research, Identification, and Writing
  • GCCS Design, SEM Scans, Wellfield Monitoring
  • Landfill Gas Migration Control
  • Subsurface Fire Assessment and Remediation
  • Groundwater and Surface Water Monitoring, Reporting, and Compliance
  • Site Permitting
  • Annual Surveys
  • Annual Airspace Assessment

Notable Accomplishments

Throughout the duration of our contract, Oasis has worked closely with VIWMA to provide the following:

• Strategic Engineering and Environmental Planning
• Closure Evaluation and Assessment
• Detailed Design (Cover, MSE Walls, GCCS System)
• Specifications
• A CQA Plan
• An Operations and Maintenance (O&M) Plan
• Construction Cost Estimating
• Air Permitting for the GCCS System
• O&M Cost Estimating

Successful regulatory negotiations, which include USEPA Region 2 RCRA and CAA, have been achieved with the Coastal Zone Management (CZM), the FAA, the Dept. of Planning & Natural Resources (DPNR),  and the State Historic Preservation Office (SHPO).

Oasis successfully negotiated on behalf of VIWMA with USEPA Region 2 for acceptance of the use of a synthetic closure system, combined with a horizontal gas collection system, to save VIWMA $2 million in capital costs for the gas collection system, as well as $1.6 million in post-closure care costs.

Oasis also successfully negotiated on behalf of VIWMA with USEPA Region 2 for the inclusion of a mechanically stabilized wall system which achieved the following:

• mitigated disturbance of adjacent mangroves to the landfill
• provided for additional airspace volume during closure
• met USEPA’s closure requirements

The result of utilizing the MSE wall to enhance vertical capacity was 6 years of additional airspace at the Bovoni Landfill.

Finally, by increasing the frequency of fill progression monitoring from annually to quarterly, Oasis was able to identify near-term air space opportunities and consequently provide VIWMA with time to solicit closure funding.

All of these efforts were undertaken in conjunction with VIWMA staff to preserve precious on-island natural resources, provide VIWMA with over $5 million in cost savings, and to comply with the 1999 USEPA Consent Order for closure of the Landfill.

Project Gallery

Project summary

In 2012 Oasis Construction Services, Inc. (Oasis) was awarded the Engineering, Environmental, and Accounting Services Contract for services at the Anguilla Landfill in St. Croix, the Bovoni Landfill in St. Thomas, and the Susannaberg Landfill in St. John, USVI.

The Anguilla Landfill is located on 42 acres which has been used as a landfill since approximately 1967.  In 2002 the U.S. Environmental Protection Agency (USEPA) issued an Administrative Order which required the proper operation and maintenance of the solid waste disposal facility in compliance with federal regulations.  The site is currently working under two Administrative Orders of Consent (Nos. RCRA-02-2001-7302 and RCRA-02-2005-7302), which require a number of activities mandated by the Court.

The Bovoni Landfill is located on an approximate 30-acre parcel of land adjacent to Bovoni Bay on St. Thomas.  The United States of America, on behalf of the USEPA, filed a complaint alleging that the Government of the U.S. Virgin Islands (GVI) and VIWMA violated Sections 111(d), 112, 114, and 503 of the Clean Air Act (CAA), 42 U.S.C. § 7401, et seq. and § 7003(a) of the Solid Waste Disposal Act, as amended, 42 U.S.C. § 6901, et seq. (RCRA) at the Bovoni Municipal Solid Waste Landfill (Bovoni).

In 2012 the USEPA and the GVI entered into a consent decree which required landfill operations and closure to be in compliance with CAA and RCRA regulations.  To fulfill Consent Decree requirements, Oasis has been responsible for quarterly groundwater monitoring and methane surface sweeps.  Although pollution prevention measures have been cost-prohibitive, and the landfill is established as unlined, measures to protect groundwater exist naturally as a significant massive rock layer exists beneath the site.

Oasis has been using state-of-the-art technology to maximize performance and minimize cost impacts at both landfills.

Closure Designs

Development of closure designs for both Anguilla and Bovoni Landfills was overseen by USEPA, which required the inclusion of a GCCS Plan for both sites.  For both landfills the design provided a final cover of thickness and structural capacity suitable to promote surface water runoff, conveying it to designated locations where it could be appropriately managed.  The design also mitigated infiltration.  In order to advance the geotechnical design for the cap and the mechanically stabilized earth (MSE) wall, both of which were included in the designs, preliminary geotechnical testing for design basis purposes was completed at each landfill.

Closure Design – Anguilla Landfill

The closure process for the Anguilla Landfill began in 2009, and design and permitting were completed in less than 4 years.  During that time the primary regulatory focus was the cessation of accepting waste for disposal in the landfill by 2012. In support of VIWMA’s  original closure design package for Anguilla Landfill, and to address groundwater flow and quality, Oasis was authorized to install 6 groundwater wells and 4 soil borings. This work was completed in June 2009.

Like the Bovoni Landfill, pollution prevention measures that might have been employed were unfortunately cost-prohibitive, and the landfill is established as unlined; however, measures to protect groundwater exist naturally as a significant clay layer exists beneath the site.

In 2013, Oasis prepared a 100% closure design for Anguilla which provided the following:

• Space which had been allocated for the design and development of a waste transfer station, recycling center, and scrap tire and metal center, the construction of which have been completed by VIWMA
• An active gas control system, which contains horizontal wells on spacing of 100 feet to control the migration of methane gas from the site, and which was connected with lateral and header piping to a gas flare station.

With permit design and the introduction of a bale waste facility transfer station, Oasis also developed a fill sequence plan for placing bales to achieve final grades for closure.  Oasis applied for, and successfully achieved, permitting with USEPA and the Federal Aviation Administration (FAA) for the bales so that they could be placed in order to achieve the final closure grades.  Everything is now filled to closure grades in preparation for landfill closure.

Closure Design – Bovoni Landfill

The closure design process for Bovoni Landfill began in 2012, after progressing through a series of design and closure modification permitting challenges which were necessary, because of steep slopes, to minimize waste relocation and in order to ensure long-term stability.  Oasis worked closely with VIWMA and USEPA to complete the design and permitting for the Bovoni Landfill Closure, which was accomplished from start to finish in one year.

The closure design process for Bovoni Landfill began in 2012, and provided the following:

• Upgrades to an active gas control system, which contains horizontal wells to control the migration of methane gas from the site, and which is connected with lateral and header piping to a gas flare station and engine
• Preservation of the environment, as the surface water management system is designed to cut off leachate flow to the mangroves.

One of the greatest challenges at Bovoni has been the continuous dwindling of available airspace.  By developing a plan for construction of the west berm, Oasis was able to provide airspace for an additional eight months.  Our services included bidding assistance, CQA services, and construction management for the construction.  By helping VIWMA develop an interim waste fill sequence for the east side of Bovoni, we were also able to provide  additional airspace for two years.

Annual Survey

For both the Anguilla and Bovoni Landfills, Oasis has been providing an annual aerial survey with required controls and additional ground run topography.  For Anguilla, VIWMA had only pieces of incomplete ground run surveys dating back to 2006.  For Bovoni, a new annual flyover was completed in 2012 to benchmark the landfill and evaluate remaining airspace.  An annual flyover with an airspace report was required by USEPA as a part of managing both landfills.  To stay abreast of the amount of remaining airspace throughout the duration of our contract, Oasis has been using an annual topographic survey and a calculation of annual fill capacity usage.

Groundwater Monitoring

Oasis has been performing the following services for both Anguilla and Bovoni:

• Gather information required for a general site area description (such as proximity to roads, airports, railroads, national historic sites, floodplains, streams, wetlands, public and private water supplies, etc.)
• Waste boundary determination
• Topographic map of general site area (1:24,000)
• Hydrogeological Characterization
• Geological Characterization
• Determination of Groundwater Flow Direction and Hydraulic Gradient
• Upper Aquifer Determination
• Monitoring Well Placement Determination
• Quarterly Groundwater Monitoring
• Information gathering
• Hydro and Geological Characterization, groundwater flow direction and hydraulic gradient, upper aquifer determination, monitoring well number and placement
• Quarterly Groundwater Monitoring
• Assessment of Corrective Measures

Grant Research and Identification

Oasis researched and submitted applications for two potential grants, one for groundwater resources protection, and the other for surface water protection, which included monitoring and training VIWMA staff.  Both grants were awarded to VIWMA.

Additional Services Cost Estimate Review

Throughout the tenure of our contract Oasis has been developing annually proposed budgets for the review of cost estimates associated with the three landfills at St. Croix, St. Thomas, and St. John.

Additional Services at Anguilla and Bovoni Landfills

Additional services for the Anguilla Landfill included assisting VIWMA with managing FAA permit compliance for achieving maximum landfill height elevation.  Additional services specific to the Bovoni Landfill include the following:

• Air Permitting
• Stormwater Pollution Prevention Plan (SWPPP)
• Subsurface Investigation for MSE Wall
• Technical assistance with a subsurface fire investigation, to determine the cause and mechanism of a subsurface fire.

In addition, Oasis provided assistance with evaluating new landfill expansion and/or siting options at both Bovoni and Anguilla.


One of Oasis’s most significant contributions has been keeping VIWMA current with compliance activities as mandated by the Federal District Judge’s Order on Consent for landfill closure activities at both Anguilla and Bovoni Landfills.  When providing expert testimony at the Federal District Court Hearings, Oasis’s preparation included providing documentation showing timelines that demonstrated the sequence of events to provide proof of compliance.  We have continued to provide VIWMA with USEPA Region 2 and Department of Justice (DOJ) technical assistance for Consent Order compliance.