TranslateMemphis Dry Cleaner
Project Year
2014
Project Duration
8 months
Contaminants of Concern
Remediation Technologies Used
- • Enhanced Bioremediation
- • EHC® Substrate Injection
- • Direct Push Technology
- • Reductive Dechlorination
Key Results
- ✓Substantial PCE and TCE reduction achieved
- ✓Complete dechlorination pathway to ethene
- ✓Sustained biological activity over multiple years
- ✓Successful treatment in urban environment
- ✓Low-impact remediation suitable for developed areas
Target Contaminants
Site Background
This former dry cleaning facility in the Memphis metropolitan area (Bartlett, Tennessee) operated for many years, resulting in PCE and TCE contamination of subsurface soil and groundwater. The urban location added complexity to remediation planning and implementation.
The site required a low-impact remediation approach suitable for the developed area while still achieving effective treatment.
Remediation Strategy
IET implemented an enhanced bioremediation program using substrate injection to stimulate reductive dechlorination. The approach included:
- Controlled-release carbon substrate (EHC®) for sustained electron donor supply
- Strategic injection point placement to maximize treatment zone coverage
- Creation of strongly reducing conditions favorable for dechlorination
- Minimal surface disturbance suitable for urban environment
The biological approach provides ongoing treatment for years after injection, making it cost-effective for long-term remediation.
Implementation
The substrate injection program was conducted using direct-push technology, which allowed for rapid deployment with minimal site disruption. IET's field crew worked efficiently to complete all injections while maintaining low visibility in the urban setting.
Multiple injection locations were established to ensure adequate substrate distribution throughout the contaminated zone, targeting both source areas and dissolved plume.
Results
The enhanced bioremediation program delivered strong performance:
- PCE and TCE concentrations substantially reduced
- Complete dechlorination pathway established
- Daughter product degradation to ethene observed
- Sustained biological activity over multi-year monitoring period
- Successful treatment in challenging urban environment
The project demonstrated that effective bioremediation can be achieved even in complex urban settings with proper planning and execution.
Technical Approach & Enhanced Bioremediation Chemistry
This Memphis project utilized EHC® substrate injection — a proprietary combination of controlled-release organic carbon and zero-valent iron (ZVI) designed for enhanced reductive dechlorination (ERD) of chlorinated solvents. EHC creates strongly reducing conditions (ORP below -200 mV) that favor the growth of dechlorinating bacteria, while the ZVI component provides both abiotic reductive dechlorination and ferrous iron that sustains the anaerobic geochemical environment needed for biological treatment.
The direct-push delivery method enabled rapid, low-impact deployment across multiple injection locations in the urban Memphis setting. Direct push technology advances injection rods to the target depth without drilling fluid or casing, generating minimal cuttings and allowing the field crew to complete all injections with minimal surface disturbance — a critical advantage for remediation in developed areas where site disruption must be minimized.
The 8-month project duration with multi-year monitoring demonstrates the sustained treatment approach characteristic of enhanced bioremediation. Unlike ISCO which provides rapid contaminant destruction over weeks to months, ERD establishes a self-sustaining biological treatment system that continues degrading chlorinated solvents for years after the initial injection. The complete dechlorination pathway to ethene documented in the results confirms that the biological community was successfully established and maintained throughout the treatment zone.
Memphis Site Context & Tennessee Geology
Memphis, Tennessee is located in Shelby County within the Mississippi Alluvial Plain physiographic province. The shallow geology consists of Quaternary-age alluvial deposits of the Mississippi River floodplain — predominantly sand, silt, clay, and gravel — overlying the Tertiary-age Claiborne and Wilcox formations. The alluvial deposits are characterized by high permeability and a shallow water table (typically 10–30 feet bgs), creating conditions favorable for in-situ remediation but requiring careful reagent distribution to address the heterogeneous alluvial stratigraphy.
The Memphis aquifer system is a critical drinking water resource for the region, making effective source zone treatment essential to protect downgradient water supply wells. The urban setting of this project — with the contamination located in a developed area requiring minimal surface disturbance — demonstrates the advantage of direct-push ERD delivery over conventional drilling and excavation approaches. The 2014 project date and 8-month duration reflect the established track record of IET's bioremediation programs in the Tennessee market.
