Landfill Cap Design and Installation for Texas Refinery
At a Texas petroleum refinery, Trihydro designed and managed the construction of a custom landfill cover system to address slope stability and leachate issues—delivering cost savings for our client and creating a safer site.
Trihydro has supported more than 100 environmental projects at this refinery since 2017. Among these projects, Trihydro was tasked with closing a hazardous waste landfill. Our team’s approach included:
- Analyzing alternatives
- Removing out-of-service equipment
- Designing and constructing a stormwater channel
- Stabilizing and grading an adjacent slope
- Repairing the existing bottom liner
- Designing and overseeing the installation of a 3½-acre landfill cover system
- Obtaining closure certification
The site was originally a double-lined, hazardous waste surface impoundment, later converted into a nonhazardous waste landfill. The refinery used the remaining headspace to store remediation-related waste materials, primarily hydrocarbon-impacted soil. As the landfill neared capacity, the site owner asked Trihydro to assist with the closure. The site was also producing leachate that required frequent sump pumping—multiple times a week—resulting in significant costs and increased health and safety risks. Additionally, the existing stormwater outfall was unstable and eroding the adjacent slope.
Enhancing Site Surveys with UAS
Before finalizing the cover system design, Trihydro used Unmanned Aircraft Systems (UAS) to collect aerial photography and topographic survey data of the landfill. The high-resolution UAS survey provided a far more detailed view of the site than conventional survey methods, enabling more precise design decisions.
Approaching Challenges with Innovative Solutions
To address the long-term operations and maintenance costs and challenges our client had experienced with other landfill caps—including revegetation and mesquite tree infiltration—our team took an innovative approach by incorporating ClosureTurf® into the cover system design. We collaborated closely with our client and another consultant to submit a Class 3 permit modification for the revised design. This process involved several submittals and meetings with the Texas Commission on Environmental Quality (TCEQ), which ultimately approved the use of ClosureTurf®, marking the first time TCEQ had authorized this solution for a landfill cover system.
Providing Comprehensive Project Support
Trihydro prioritized close coordination with our client—holding regular meetings to align on timelines, contracting strategies, and construction readiness. In addition to developing design plans and specifications, our team solicited bids for cover system installation and quality assessment and quality control scopes of work, hosted a pre-bid meeting, reviewed bids, and selected contractors with our client. Weekly status calls and ongoing communication ensured that our client remained informed and engaged throughout the project.
We also provided construction oversight and general contracting for the cover system installation. Following its completion, Trihydro managed, oversaw, and contracted the installation of a perimeter fence around the closed landfill.
Ultimately, our team submitted a closure certification report for the completed project that was approved by TCEQ. The successful landfill closure addressed both the slope stability concerns and costly leachate problem.
