Client/Site: EnPro/Central Moloney Inc. Site, Pine Bluff, Arkansas
Project Description: EnSafe was tasked in 2019 with assessing and improving a groundwater pump and treat system, initially installed in 2013 following a Remedial Action Decision Document (RADD) from the Arkansas Department of Environmental Quality (ADEQ) in 2007. Since 2020, EnSafe has completed several upgrades and optimizations, including well installations, system controls upgrades, and treatment system improvements, significantly enhancing system performance. We have also conducted in-situ pilot tests using various amendments for off-site plume control (in 2021) and source area treatment (2023-24) to expedite the transition to natural attenuation monitoring and site closure.
Engineering Team:
- Bridget Morello, Client Manager
- Bernie Lauctes, Senior Engineer
- April Cameron, Project Engineer
- Ken Callahan, Project Manager
Business Development’s Raven Kraft had the privilege of sitting down with this incredible team and delving into the intricacies of this complex remediation project.
Q: Let’s start with you, Bridget. As the Client Manager on this complex project, can you provide an overview of the project and its objectives?
Morello: Certainly. In 2019, EnPro enlisted EnSafe to conduct a comprehensive review and evaluation of the site conditions and remedial efforts. We developed a new remedial strategy involving phased assessment and data gap filling, upgrades to the exiting groundwater remedy, and phased off-site and on-site source area in-situ chemical oxidation and enhanced reductive dechlorination pilot testing.
We obtained regulatory approval for remedial enhancements and negotiated new NPDES and air discharge permits, performed design/build of the upgrades to the groundwater pump and treat system and improved system uptime from ~40% to ~98%. Our assessment, aquifer testing and groundwater modeling efforts ensured placement of new recovery wells would provide plume containment and prevent off-site migration. This upgraded pump and treat system features a tray air stripper and carbon filtration with sophisticated instrumentation and controls for remote monitoring and alarm notification purposes, and has reduced the frequency of O&M visits and overall costs significantly. The current in-situ pilot study was designed as a phased approach to knock down high PCE source area concentrations using chemical oxidation with PersulfOx and RegenOx (Phase 1), followed by enhanced reductive dechlorination using 3-DME, micro-Sulfidated ZVI, and bacterial amendments (Phase 2). The initial source area pilot study results indicate 70-80% concentration reductions after two chemical oxidation injection events.
Q: Wow, so this project started long before EnSafe got involved.
Morello: Yes, the prior consultants’ efforts produced lackluster results and permit compliance concerns. Our reassessment included lateral and vertical groundwater plume delineation, slug/aquifer testing, well integrity survey, potable well survey, groundwater modeling and capture zone evaluation – all of which led to an updated Conceptual Site Model and identified off-site plume impacts, and our strategic closure path.
Lauctes: And this continues to be an ongoing project. We are in the process of continuing the source area pilot study and perform routine operations and maintenance, with post-active remediation monitoring expected to continue into 2025.
Q: This all sounds like a significant undertaking. What were some of the key challenges you’ve faced during the project?
Callahan: One of the main challenges was ensuring the effectiveness of the existing P&T system and optimizing its performance. We also had to address immediate concerns raised by the ADEQ regarding remedy performance and capture zone.
Cameron: And conducting offsite pilot study and delineation work posed logistical and technical challenges to minimize disruption to an adjacent school, active railroad line, and residential community. Not to mention needing to build a road to access areas for the offsite pilot study work.
Q: How did you approach these challenges, and what were the outcomes?
Callahan: We took a multifaceted approach, starting with a thorough review of historical documents and site hydrogeology. This led to the implementation of several improvements to the existing P&T system, including the installation of new extraction wells, upgrades to the water treatment filtration and carbon system, and installation of a remote monitoring system. These efforts significantly enhanced the system's run-time from less than 40% to more than 98% and improved groundwater recovery rates creating a well-defined capture zone for plume control.
Cameron: We developed talking points and FAQs to share with ADEQ and the community in the event questions arise during the off-site work. We also located wells in rights-of-way versus private property to minimize disruption and eliminate the need for access agreements over the long term.
Q: And that’s exactly why the client brought in EnSafe, to review and offer improvements to the existing remediation system, right?
Lauctes: Exactly. The client is pleased with the aggressive remedial strategy and long-term site closure pathway EnSafe developed and our efforts to coordinate regulatory approval of plans and permits. And even better, our completion of the construction of the remedial system upgrades ahead of schedule and under the approved budget.
Q: Looking ahead, what are the next steps for the project, and what is the long-term outlook?
Callahan: In the short term, we are focused on streamlining O&M activities, completing the phased source area pilot study, and completing offsite plume delineation. The current source area in-situ pilot study results will be reviewed in order to develop an expansion design to address the rest of the source area, thereby limiting the long-term use of P&T. The ultimate goal is to expedite the transition from active remediation to natural attenuation monitoring and achieve site closure.
Q: It doesn’t get much more important than that. Thank you all for sharing insights into this important project. It's clear that your team's dedication and innovative approach are driving positive change in environmental remediation.
Lauctes: We’re certainly proud. Our remediation efforts will pave the way for a more sustainable and cleaner future for the site and surrounding areas.