TranslatePinehurst Former Dry Cleaner
Project Year
2016
Project Duration
12 months
Contaminants of Concern
Remediation Technologies Used
- • Biological Reductive Dechlorination
- • EHC® Controlled-Release Substrate
- • Direct Push Injection
- • Multi-Event Treatment
Key Results
- ✓Over 75% PCE reduction achieved
- ✓Complete dechlorination to ethene documented
- ✓Sustained biological activity for multiple years
- ✓Progressive plume reduction over time
- ✓Cost-effective long-term solution
Target Contaminants
Site Background
This former dry cleaning facility in Pinehurst, North Carolina, operated for several decades, resulting in perchloroethylene (PCE) contamination of soil and groundwater. The contamination included PCE and its breakdown products (TCE, DCE, and vinyl chloride).
The site required a sustainable, long-term approach to address the persistent chlorinated solvent plume.
Remediation Strategy
IET implemented a biological reductive dechlorination program using electron donor injection. The approach included:
- EHC® controlled-release substrate for sustained electron donor availability
- Creation of strongly reducing conditions to promote dechlorination
- Strategic injection locations targeting source and plume areas
- Multiple injection events to maintain biological activity
This biological approach provides sustainable, long-term treatment that continues to function for years after injection.
Implementation
The electron donor injection program was conducted using direct-push methods to place the EHC® substrate throughout the treatment zones. Injection depths and locations were carefully selected based on site characterization data.
The field work was completed efficiently by IET's experienced technicians, minimizing disruption to the property and surrounding area.
Results
The biological reductive dechlorination program achieved substantial improvements:
- PCE concentrations reduced by over 75%
- Complete dechlorination to ethene documented
- Sustained biological activity for multiple years post-injection
- Progressive plume reduction over monitoring period
- Cost-effective long-term solution compared to active treatment
Technical Approach & EHC Controlled-Release Chemistry
EHC® is a proprietary controlled-release substrate combining complex organic carbon sources with zero-valent iron (ZVI) for enhanced reductive dechlorination (ERD) of chlorinated solvents. The organic component slowly ferments over 3–5 years, releasing hydrogen donors that stimulate dechlorinating bacteria, while the ZVI creates strongly reducing conditions (ORP below -200 mV) and provides abiotic reductive dechlorination. This dual-mechanism approach — biological + abiotic — is particularly effective at dry cleaner sites where PCE DNAPL has created persistent source zones.
The direct-push delivery method enabled rapid, low-impact placement of EHC throughout the treatment zones. Direct push technology advances injection rods to the target depth without drilling fluid, generating minimal cuttings and allowing the field crew to complete all injections with minimal surface disturbance — a critical advantage for remediation at former dry cleaner sites in developed commercial areas like Pinehurst.
The 75%+ PCE reduction with complete dechlorination to ethene demonstrates successful establishment of the full dechlorination pathway — from PCE through TCE, DCE, and vinyl chloride to the benign end product ethylene. The sustained biological activity for multiple years post-injection is the hallmark of EHC's controlled-release design: the substrate continues fermenting and releasing hydrogen long after the initial injection, maintaining the anaerobic conditions needed for ongoing dechlorination without the need for repeated mobilizations.
Pinehurst Site Context & North Carolina Geology
Pinehurst, North Carolina is located in Moore County within the Sandhills physiographic province of the Piedmont region. The shallow geology consists of Cretaceous-age unconsolidated sediments of the Middendorf Formation — predominantly sand, clay, and gravel — overlying older crystalline basement rocks. The sandy soils in this area are moderately permeable, creating favorable conditions for in-situ bioremediation via direct push injection.
Former dry cleaning facilities like this site commonly have PCE contamination from decades of solvent use. PCE is a dense chlorinated solvent that migrates downward through soil as a DNAPL, accumulating at lithologic interfaces and creating persistent source zones that sustain dissolved-phase plumes for decades. The biological ERD approach used here — with sustained hydrogen release from EHC over multiple years — is ideal for these sites, as it provides the long-term reducing conditions needed to completely dechlorinate PCE to ethene without the cost and disruption of source excavation.
