Underground Storage Tanks (USTs) Land Treatment at Lowry Air Force Base (AFB), Denver, Colorado

Site Name:

Lowry Air Force Base


Denver, Colorado

Period of

Status - Ongoing Report covers - 7/92 to 9/93


Full-scale cleanup (interim results)


Engineering Science, Inc.
1700 Broadway, Suite 900
Denver, CO 80290

Land Treatment - Soil spread on plastic sheeting to thickness of 14 to 18 inches - One-time addition of ammonium nitrate nutrients (C:N:P ratios of 200:10:1) - Soil aerated twice a month (April-November) - Soil moisture content 10%-15%

Cleanup Authority:
State: Colorado

SIC Code:
9711 (National Security)
Point of Contact:
Lt. Tom Williams
3415 CES/DEV
Lowry AFB, CO 80230

Benzene, toluene, ethylbenzene, and xylenes (BTEX) and Total Petroleum Hydrocarbons (TPH) - Contaminated soil - BTEX < 100 mg/kg; Total Recoverable Petroleum Hydrocarbons (TRPH) up to 11,000 mg/kg; 3,100 mg/kg average - Stockpiled soil - average TRPH of 3,983 mg/kg

Waste Source:
Underground Storage Tank

Type/Quantity of Media Treated:
Soil - Soil type firm sandy clay and medium to coarse-grained sand - Soil moisture content ranged from 6% to 11% - 5,400 yd[Sup 3] treated plus three additional truckloads of contaminated soil

Purpose/Significance of Application:
Land treatment to remediate soils contaminated with heating oil which contained relatively high concentrations of TPH and relatively low concentrations of soluble contaminants (e.g., benzene).

Regulatory Requirements/Cleanup Goals:
- Treated soil - TPH < 500 mg/kg; TRPH < 500 mg/kg; and BTEX < 100 mg/kg - Cleanup conducted under EPA and State of Colorado Underground Storage Tank Regulations and the Colorado Department of Health's Remedial Action Category III (RAC III) action levels

- Land treatment project was not complete at time of this report - No TRPH, BTEX, or TPH data are available at this time - Total Extractable Petroleum Hydrocarbon levels as of September 1993 ranged from 1,300-1,700 mg/kg

Cost Factors:
- Total Capital Cost - $104,257 (including site work, permitting, construction/mobilization/demobilization, pilot testing, project management); pilot testing was $76,000 of the total capital costs - Estimated Annual Operating Costs - $18,460 per year (including laboratory charges, maintenance, monitoring)

As a result of a leak of heating oil from an underground storage tank (UST) at Lowry Air Force Base in Denver, Colorado, soil at the site was contaminated with total petroleum hydrocarbons (TPH) and benzene, toluene, ethylbenzene, and xylenes (BTEX). An estimated 10,500 gallons of fuel oil were released. The USTs in the area were removed and the contaminated soil was excavated. Land treatment was selected for the excavated soil; treatment of about 5,400 cubic yards began in July 1992 and is ongoing at the time of this report. For this land treatment application, nutrients (ammonium nitrate) were added in a one-time application, the soil is tilled twice a month, and soil moisture content is kept between 10 to 15% by weight. The target cleanup levels for the soil are TPH to less than 500 mg/kg; Total Recoverable Petroleum Hydrocarbons (TRPH) to less than 500 mg/kg, and BTEX to less than 100 mg/kg. The cleanup is being conducted under the authority of the Colorado Department of Health Underground Storage Tank Program.

The estimated completion time for the land treatment operation was two years. However, as of September 1993, the treatment had not been completed. While no TPH, TRPH, or BTEX data were available at the time of this report, levels of Total Extractable Petroleum Hydrocarbons (TEPH) sampled as of September 1993 showed levels in the range of 1,300 to 1,700 mg/kg. These data and the results of a pilot test, which showed a general decrease in TEPH over time, appear to indicate that land treatment will be effective, though no projections for a completion date are available at this time.

The total capital cost for this project is $104,257 including $76,000 for pilot testing, and the estimated annual operating costs are $18,640. Available information to date indicates that the credibility of the land treatment soil assessment would have been improved if an adequate, random sampling program had been used for sample collection. In addition, laboratory analysis should have been consistent throughout the pilot test or an explanation of inconsistencies provided.