Houston Dry Cleaner, Houston, Texas

State Coalition for Remediation of Drycleaners Site Profiles

Description
Historical activity that resulted in contamination.

During a due diligence review, a shallow chlorinated solvent plume was discovered surrounding an area dry cleaning facility from historical operating and handling practices. The shallow soil was relatively permeable, which allowed for the rapid migration of the perchloroethylene (perc or PCE) into the shallow ground water. The plume had migrated off-site and underneath an apartment complex, which caused a concern for potential vapor intrusion hazards. To address the ground water plume, a pump-and-treat system was installed; the pump-and-treat system successfully decreased the source area, but the operating and maintenance costs were exceeding the on-going remedial benefit. After nine years, the system was shut down. For further reduction of the contaminant plume, other remedial technologies were investigated, including in-situ chemical oxidation and enhanced bioremediation.

Remediation Status: In groundwater monitoring

Contaminants
Contaminants present and the highest amount detected in both soil and groundwater.

Contaminant	Media	Concentration (ppb)	Nondetect
cis-1,2-Dichloroethene	groundwater	34,000 ppb
1,1-Dichloroethene	groundwater	50 ppb	ND
Tetrachloroethene (PCE)	groundwater	4,100 ppb
Trichloroethene (TCE)	groundwater	2,500 ppb
trans-1,2-Dichloroethene	groundwater	160 ppb
Vinyl Chloride	groundwater	50 ppb	ND

Site Hydrology

Deepest Significant Groundwater Contamination:
Plume Size:
Average Depth to Groundwater:		15ft

Lithology and Subsurface Geology

Chicot aquifer

discontinuous layers of sand and clay, later classified as sand to silty sand
Depth: 15-20ft bgs
5ft thick
Conductivity: 11.33858268ft/day
Gradient: 0.002ft/ft

Pathways and DNAPL Presence

Groundwater

Sediments

Soil

DNAPL Present

Remediation Scenario

Cleanup Goals:

Tetrachloroethene: 0.005 mg/L
Trichloroethene: 0.005 mg/L
1,1 Dichloroethene: 0.007 mg/L
cis-1,2-Dichloroethene: 0.07 mg/L
trans-1,2-Dichloroethene: 0.1 mg/L
Vinyl Chloride: 0.002 mg/L

Technologies

In Situ Bioremediation

Why the technology was selected:
Even though the pump-and-treat system was effective on the source area, the off-site migration needed to be addressed. Additional remediation alternatives were carefully reviewed. In-situ bioremediation from CL Solutions, LLC was chosen because of the decreased levels of dissolved phase contaminants present, the presence of dissolved oxygen, and the reduced risk of vinyl chloride formation. In addition, the microbes could easily colonize in the pore spaces of the soil with longer treatment residence times.

Date implemented:
Three applications of CL-Out® were conducted on July 19, 2005, October 27, 2005, and February 23, 2006. A total of 7 units was injected during this 9 month period.

Final remediation design:
CL-Out® is a consortium of Pseudomonas microbes that are sent as a freeze-dried powder to ensure a high microbial count. Prior to injection, the CL-Out® is hydrated with clean tap for 24 hours. Immediately before the injection, food grade dextrose is added to the microbial mixture. The CL-Out® mixture was injected, under low pressure, into the contaminated ground-water zone through temporary injection points. The first injection applied 3 units to 16 points, and the remaining injections applied 2 units to 10 points. The spacing between the points was roughly 20-25 feet.

Results to date:
The total chlorinated VOC concentrations were reduced from 40,600 to 115 µg/L in the source area (MW-6). Concentrations in the peripheral wells were reduced from 1,386 to 9 µg/L (MW-4) and from 734 to less than 5 µg/L (MW-7). The total contaminant concentrations were reduced by more than 98 percent across the contaminant plume.

Next Steps:
Quarterly monitoring to the regulator

Cost to Design and Implement:
CL-Out® aerobic bioremediation for the ground-water treatment cost less than $20,000. Please note that this price does not include monitoring and reporting to the regulatory agencies.

Ex Situ Pump and Treat

Next Steps:
Quarterly monitoring to the regulator

Costs

Cost for Assessment:
Cost for Operation and Maintenance:		In comparison, the operating cost for the pump-and-treat system was approximately $75,000 per year, excluding capital expenditures.
Total Costs for Cleanup: