projects

City of Atlanta – Four Closed Landfills Post-Closure Services

Atlanta, GA | 2011 – Ongoing

Scope of Services

Notable Accomplishments

Oasis’s efforts with the GCCS upgrades at Cascade Rd., Gun Club Rd., and Key Rd. Landfills increased the gas flow and concentration from each of the wellfields, which in turn helped to maintain a stable flame at the respective flares. As a result, outages and downtime at each landfill were decreased, and the enhanced gas collection ultimately controlled the gas migration.

As a result of Oasis’s efforts installing the new open flare at Cascade Rd., the flare operation was stabilized in spite of challenges presented by the gas flow and concentration from the wellfield, and outages and downtime were substantially decreased.

While providing the slope stability and drainage improvements at Cascade Rd., Oasis was able to mitigate unforeseen subsurface conditions and provide comprehensive solutions for problems encountered with the slopes. We also kept the project on schedule in spite of other issues such as poor weather conditions. As a result of the installation of the Redi-Rock® gravity retaining walls, previous ongoing difficulty with mowing and maintaining the slopes was eliminated. Oasis’ design-build approach utilizing the Redi-Rock® gravity walls cost approximately half of the previous $3+ million estimates which would have relied on traditional designs and design-bid-build methods, providing substantial savings to the City.

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Project summary

The City of Atlanta has four landfills which were closed in 1998 and 1999 and which are currently in Post-Closure Care. Under subcontract to ARCADIS/BPA J.V., Oasis was retained by the City of Atlanta as a part of their Landfill Post-Closure and Operational Maintenance Contract to provide groundwater and surface water monitoring, laboratory analysis, statistical analysis, and reporting services at Cascade Road Landfill, Gun Club Rd. Landfill, Key Rd. Landfill, and East Confederate Rd. Landfill in Atlanta, Georgia. Services also include gas collection and control system (GCCS) installation and maintenance services, design and construction, permitting, and resolving a slope stability issue.

As Oasis/ARCADIS/BPA J.V. began the post-closure contract in the latter half of 2011, one of their first tasks was to perform a full inspection and evaluation of each of the City’s four landfills. In 2013 Oasis provided design, installation, CQA monitoring, and final certification services for the construction of the gas collection and control system (GCCS) upgrades at Key Rd. Landfill, Gun Club Rd. Landfill, and Cascade Rd. Landfill. Services at Cascade Road included GCCS upgrades, new flare installation, and slope repair.

Oasis prepared GCCS Evaluation Reports which detailed the current status of each landfill. We also outlined a three-phased approach for recommended repairs and upgrades for each system in order to improve gas control and maintain perimeter methane gas compliance to ensure optimal operation. The first phase was implemented in May and June of 2012, and generally consisted of replacing wellheads, well hoses and clamps; replacing well tops and fittings with Fernco style seals; and installing a FleetZoom Telemetry System for real-time on-line monitoring via internet to provide critical feedback to operational personnel. Phase 2 repairs and upgrades, implemented in September 2012, were more specific to the needs of each landfill. Each site was recommended for the determination of liquid levels.

At Gun Club Road Landfill, Phase 2 generally entailed a liquid level pumping study on all gas extraction wells; replacement of the oversized enclosed ground flare with an open (candlestick) flare; the dismantling and removal of existing enclosed flare stacks; installation of a three-phase air compressor and new pumps in three condensate sumps; and installation of a 6-inch header jumper line to bypass a blocked section of header. Additionally, a new airline/forcemain system was installed to provide air to pneumatic sumps and to enforce the discharge of collected liquid to a new double-wall condensate tank. The recommended Phase 3 approach was to design and install 10 new vertical gas extraction wells, which were connected to the existing GCCS with new laterals tied to existing headers. Implementation of the 2013 GCCS upgrades was initiated, beginning with well drilling and progressing to piping installation in late 2013. The work was completed in early 2014.

At Key Road Landfill, Phase 2 generally entailed a liquid level pumping study on all gas extraction wells, installation of a three-phase air compressor, new pumps in three condensate sumps, and rebuilding blower bearings for three blowers. The recommended Phase 3 approach was to design and install 10 new vertical gas extraction wells, which were connected to the existing GCCS with new laterals tied to existing headers and laterals. Construction commenced April 30, 2013, and was substantially completed in June 2013. Wellheads were installed in late August, at which time a commissioning phase was begun to bring the new wells on-line.

At Cascade Road Landfill, Phase 2 generally entailed a liquid level pumping study on all gas extraction wells, repair of flare blowers (bearing replacement), repair of flare stack louvers, repair of flare knock-out pot level sensors and discharge pump, repair of refractory lining, and installation of a three-phase air compressor and new pumps in three condensate sumps. The recommended Phase 3 approach was to design and install 20 new vertical gas extraction wells, which were connected to the existing GCCS with a new 6-inch header and new laterals tied to existing headers. In April 2013 Oasis prepared construction plans for the Phase 3 GCCS upgrades.

Services at Cascade Road Landfill included construction of slope stability and drainage improvements. The City of Atlanta had tasked ARCADIS and Oasis with developing improvements to the very steep southern and eastern slopes of the capped area to mitigate the risk of slides since a slide had already occurred in 2009, when emergency repairs were undertaken but the resulting slopes were still steeper than the recommended 3H:1V configuration. A solution was provided with the construction of two Redi-Rock® gravity retaining walls, which totaled 827 feet in length and had an average height of 10 feet, with a maximum height of 14 feet. This design was approved by GAEPD in April 2014 and construction began in July. The walls, which achieved maximum 3H:1V slopes, improved slope stability and storm water control. Additionally, a leachate collection system was installed which includes pneumatic pumps in numerous wells in the vicinity of the
Redi-Rock® walls that discharge to a collection sump near the base of the walls. The sump contains a float controlled electric pump which pumps collected fluids to a permitted waste water treatment plant discharge location. GCCS upgrades in the slope repair area were designed in conjunction with the slope repair and focused additional vacuum in the area immediate to MM-10, where the greatest perimeter methane concentrations exist.

Further GCCS upgrades were incorporated into the design, both to replace existing minimal GCCS components and to enhance vacuum in the southeast corner of the site. These plans were completed and submitted to GAEPD, and the complete GCCS upgrades were brought on-line in early 2014.

The GCCS upgrades at Cascade Rd. also included design and installation for the construction of a new open (candlestick) flare. Decreasing landfill gas flows, combined with aging equipment, dictated the need for replacement of the original enclosed ground flare. Oasis completed Minor Modification permitting with GAEPD and performed a turnkey design-build installation and start-up of a new skid-mounted open flare. Concurrently Oasis installed a new Atlas Copco air dryer to mitigate moisture buildup and to address any other operational issues which could occur with the existing air compressor. The new flare was successfully brought online February 1, 2016.

Oasis’s services included achieving an approved Assessment of Corrective Measures Report for Key Rd. Landfill. The other three landfills had already merited approval and, having gone through the required public participation process, are in the implementation phase of approved Corrective Action Plans (CAPs). Key Rd. Landfill, however, did not receive initial approval for the ACM Report which had been submitted in 2006. In early 2011 GAEPD concurred with the delineation of the volatile organic constituents (VOCs) so that the ACM process could be completed, and Oasis prepared a Revised ACM based on new data and statistical analysis and successfully met the regulatory deadline by completing and submitting the Revised ACM to GAEPD in April 2012.

Changes to site conditions warranted an update to the ACM in late 2013 through early 2014. After GAEPD reviewed and approved the updates, the public meeting was held in September 2015 and Oasis prepared for implementation of the CAP which included use of an Enhanced Anaerobic Degradation (EAD) remedy via chemical injection. The EAD process has been designed to treat methylene chloride (the main contaminant of concern) as well as 1,4-dichorobenzene and DCE (potential future contaminants of concern) at three wells (KR-GWC-4, KR-GWC-4D, and KR-GWC-13). Oasis contracted REGENESIS® Remediation Services (RRS) to conduct the Chemical Injection activities and this work was completed in April 2017.

Post-injection laboratory results, when compared to the data from the March 2017 sampling event, have indicated that the concentrations of the release constituents initially decreased although based on the July 2017 laboratory data some rebound has occurred. As specified in the CAP, data from future semi-annual monitoring events through 2019 will be used to evaluate the effectiveness of this corrective action. Oasis performed this work as a full-service turnkey solution for the City of Atlanta.