Thermal Desorption at the Sand Creek Industrial Superfund Site, OU 5 Commerce City, Colorado

Site Name:

Sand Creek Industrial Superfund Site


Commerce City, Colorado

Period of

June 28 - July 29, 1994




Earth Tech (formerly Rust Remedial Services, Inc.)
5575 DTC Parkway, Suite 200
Englewood, CO 80111-3016
Phone: (303) 694-6660
Fax: (303) 694-4410

Thermal Desorption

- System consisted of a rotary kiln, two sulfur-impregnated vapor-phase carbon units, four liquid-phase carbon units (1,000 lb each), cyclones, a baghouse, and a packed bed scrubber

- Contaminated soil was screened and then fed to the kiln and heated to 500F for 6.5 minutes by a hot air stream

- System throughput was 35-40 tons/hour

Cleanup Authority:
CERCLA - ROD Date 9/8/93
- Federal Lead/Fund-Financed

ARCS Contractor:
Chris Stotler
URS Consultants, Inc.
1099 18th Street, Suite 700
Denver, CO 80202-1907
Phone: (303) 291-8271
Fax: (303) 296-6117
Point of Contact:
Armando Saenz
U.S. EPA Region 8
999 18th Street, Suite 500
Denver, CO 80202-2466
Phone: (303) 312-6559
Fax: (303) 312-6897

- Organochlorine pesticides - concentrations as high as 419 mg/kg for toxaphene, 28.8 mg/kg for DDD, 184 mg/kg for DDT
- Metals - concentrations as high as 131 mg/kg for arsenic

Waste Source:
Improper storage of pesticides and fires at the site

Type/Quantity of Media Treated:

- 8,254 yd3 (approximately 13,000 tons)
- Sandy loam, approximately 35% clay
- pH 7-10

Purpose/Significance of Application:
Treatment of soil contaminated with orgnochlorine pesticides, arsenic, and chromium

Regulatory Requirements/Cleanup Goals:
- The soil action levels for 12 organochlorine pesticides ranged from 1.45 mg/kg (for aldrin) to 104 mg/kg (for DDD); for two metals the soil action levels were arsenic 12.7 mg/kg and chromium 56.2 mg/kg

- Soil action levels (except for chromium) were developed based on an evaluation of risk to public health using carcinogenic effects and a residential land use scenario; the soil action level for chromium was developed using the hazard index approach

- Stack gas emission action levels ranged from 0.006 mg/m3 to 0.0238 mg/m3 for the organochlorine pesticides and were set at 0.0012 mg/m3 for chromium and 0.0048 mg/m3 for arsenic

- Contaminated soil was treated on a batch basis, with each batch containing approximately 100 yd3; at least one confirmation sample was taken from each batch to test for compliance with action levels

- Confirmation sampling results showed that the action levels for pesticides and chromium generally were achieved after a single pass through the treatment unit; two soil batches did not achieve action levels for pesticides after a single pass through the treatment unit, however these batches were retreated and met the action levels

- Arsenic levels in treated soil batches exceeded the residential land use action level of 12.7 mg/kg in the majority of samples (75 of 89); EPA determined that the residential land use action level for arsenic could not be met using the LTTD system at OU 5, and that an industrial land use action level of 25 mg/kg could be used instead of the residential land use action level

- Stack gas emissions from the LTTD system were periodically monitored and found to be below action levels

Cost Factors:
- Actual costs were $1,995,481 ($1,804,337 capital plus $191,144 O&M), which corresponds to a unit cost of $230 per cubic yard for 8,254 yd3 of soil treated, or $150 per ton for approximately 13,000 tons of soil treated

- Activities that contributed to lower costs included use of a decision tree sampling strategy (resulting in a cost savings of $330,000), additional field sampling to better characterize extent of contamination, and several reductions in the scope of work, such as eliminating a requirement to perform soil stabilization

The Sand Creek Industrial Superfund Site (Sand Creek), located in Commerce City, Colorado (a suburb of Denver), is a former industrial property that was used for the manufacture of agricultural chemicals, the production of petroleum, and the storage and distribution of chemicals. The Colorado Organic Chemical (COC) Company manufactured pesticides and insecticides at the site in the 1960s and 1970s. During this time, improper storage of pesticides, as well as fires at the site in 1968 and 1977, resulted in contamination of soil and groundwater. During the 1970s and 1980s, several administrative and enforcement actions were taken by the State of Colorado and EPA. The site was placed on the National Priorities List in September 1983.

Sand Creek was divided into six operable units for remediation. This report focuses on Operable Unit 5 (OU 5), which covered approximately 17 acres and consisted of shallow surface soils (1-5 ft bgs) contaminated with pesticides and heavy metals. (A separate cost and performance report covers soil vapor extraction at OU1). An initial Record of Decision (ROD), signed in September 1990, selected soil washing. An amended ROD, signed in September 1993, changed the remedy to on-site low temperature thermal desorption (LTTD). The ROD was changed based on the results from additional site characterization and treatability testing. LTTD system operations were conducted from June 28 - July 29, 1994. A total of 8,254 yd3 (approximately 13,000 tons) of soil were treated during this application.

Soil action levels for organochlorine pesticides and chromium were met in nearly all batches treated after the first pass through the unit. The action level of 12.7 mg/kg for arsenic was not achieved in most treated soil batches. EPA established an industrial land use action level of 25 mg/kg for arsenic at OU 5 and approved backfilling of all treated soil batches as long as the surface soils (0-1 ft bgs) were below the industrial action level. EPA reported that actual costs for treatment were $1,995,481, which corresponds to a unit cost of $230 per cubic yard for 8,254 yd3 of soil treated, or $150 per ton for approximately 13,000 tons of soil treated.