Drycleaner Site Profiles

Denver Colorado Dry Cleaner, Denver, Colorado

Description
Historical activity that resulted in contamination.

The site is a former drycleaner located at a shopping center in Denver, CO.

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


Contaminant Media Concentration (ppb) Nondetect
Tetrachloroethene (PCE) groundwater 18,200 ppb
Trichloroethene (TCE) groundwater 12,600 ppb

Site Hydrology

Deepest Significant Groundwater Contamination:   12ft bgs
Plume Size:  
Average Depth to Groundwater:   9ft

Lithology and Subsurface Geology

 
  clay
Depth: 0-9ft bgs
9ft thick
Gradient: 0.121ft/ft
 
  permeable sand and gravel
Depth: 9-12ft bgs
3ft thick
 
  siltstone
Depth: 12ft bgs

Pathways and DNAPL Presence

checkGroundwater
Sediments
Soil
DNAPL Present

Remediation Scenario

Cleanup Goals:
 

Technologies

In Situ Chemical Oxidation
 

Why the technology was selected:
ISOTEC's Modified Fenton’s Reagent was chosen as the remedial technology due to the time constraints related to a real estate transaction involving the contaminated property. Modified Fenton’s Reagent was recognized as a cost effective and expeditious approach to remediating the property.

Date implemented:
April 2001

Final remediation design:
The remediation program for the site involved two phases of field activities: two injection events for the area inside of the former drycleaner building to treat the contaminant source, and three injection events to treat the entire groundwater plume. The first phase of the remediation program involved the introduction of Modified Fenton’s Reagent into the subsurface through 18 direct push locations (nine points per event) inside the former dry cleaner building. These direct push locations were located on 15-ft centers and shifted laterally between events. The second phase was comprised of three injection events to treat the entire groundwater plume at the site. Direct push injection points were used to deliver reagents to the groundwater plume at the site. These points were spaced on 30-ft centers based on a conservative radius of influence (ROI) of 15 ft determined from a pilot test. The direct push locations for the second and third injection events were shifted laterally from the first event locations to ensure complete reagent coverage across the site. Using this spacing arrangement, approximately 75 points were required during each injection event to treat the groundwater plume. A total 26,987 gallons of ISOTEC reagents were injected through 244 temporary injection locations.

Results to date:
Following the final injection event, PCE concentrations ranged from 70 µg/L to non-detect (ND), and the average PCE concentration across the site was reduced from 3,267 µg/L to 39.6 µg/L, a reduction of 99%. The maximum PCE concentration reduction in existing monitoring wells was observed in monitor well MW-5. The PCE concentration in MW-5 was reduced from 925 µg/L to 51 µg/L, a reduction of 94%. Following the final injection event, TCE concentrations ranged from 170 µg/L to ND, and the average TCE concentration across the site was reduced from 1,387.8 µg/L to 64.9 µg/L, a reduction of 95%. The maximum TCE concentration reduction was observed in monitor well MW-5. The TCE concentration in MW-5 was reduced from 550 µg/L to 52 µg/L, a reduction of 90%. Following Modified Fenton’s Reagent treatment, the site underwent four additional quarters of sampling and monitoring. During this time frame, further reductions in groundwater concentrations were achieved since the contaminant source mass was removed and the associated mass flux was greatly reduced. This allowed the dissolved phase plume to shrink as new equilibrium conditions were established between the saturated soil and the aqueous phases. The TCE average of all wells (including source area wells) was reduced by 98%.

Costs

Cost for Assessment:
 
Cost for Operation and Maintenance:
 
Total Costs for Cleanup:
  $39/yard3 of saturated soil treated Costs include pilot scale tests, full-scale treatment, and direct push injection equipment and labor.

Lessons Learned

1. Immediately following treatment, the dissolved phase and saturated soil are in dis-equilibrium. As the site re-equilibrates,
dissolved phase concentrations come down as there is insignificant amount of contaminant mass in the saturated soil to drive high dissolved phase concentrations.

Contacts

Kathy Wahlberg
Hazardous Waste Corrective Actions Unit
Colorado Department of Health and Environment
Denver, CO
303-692-3372
Kathy.wahlberg@state.co.us

Eliot Cooper
ISOTEC
5600 S Quebec Street, Suite 320D
Greenwood Village, CO 80111
303-843-9079 x 20
ecooper@insituoxidation.com