Steam Enhanced Extraction and Electro-Thermal Dynamic Stripping Process
RCRA Corrective Action
Environmental Restoration Program Manager
U.S. Department of Energy
Telephone: (727) 541-8943
S. M. Stoller Inc.
Telephone: (970) 248-6502
Scientist and Engineer
SteamTech Environmental Services, Inc.
Halogenated Volatile Organics, Petroleum Hydrocarbons, DNAPL, and LNAPL
TCE and toluene present as free product; concentrations in soil boring samples were as high as 2,900,000 µg/kg for TCE and 1,000,000 µg/kg for toluene
Dissolved phase VOCs included TCE, cis-1,2-DCE, vinyl chloride, methylene chloride, and toluene; methylene chloride detected as high as 12,000,000 µg/L and TCE as high as 26,000 µg/L
Past operation and disposal activities
Type/Quantity of Media Treated:
Soil and Groundwater
- Site hydrogeology at Area A consists of 30 ft of a surficial, unconfined aquifer composed of relatively fine-grained sand, underlain by Hawthorn clay, which acts as a local aquitard; surficial sands range in thickness from 26 - 34 feet (ft) and typically consist of fine-grained, moderately to well-sorted sand, with variable amounts of silt and clay
- Local water table ranges in depth from 1- 6 ft bgs; ground water flows toward the east-southeast at a very low gradient
- Horizontal hydraulic conductivity range from 3.5x10-4 to 3.5 x10-3 centimeters per second (cm/sec); vertical hydraulic conductivity ranges from 1.06 x10-6 to 1.06x10-4 cm/sec.
Purpose/Significance of Application:
Steam Enhanced Extraction and ET-DSP were combined treat NAPL contamination in soil and groundwater
Regulatory Requirements/Cleanup Goals:
- Soil cleanup goals: TCE - 20,400 µg/kg; DCE - 71,000 µg/kg; methylene chloride - 227,000 µg/kg; toluene - 15,000 µg/kg; TPH - 2,500,000 µg/kg
Groundwater cleanup goals: TCE - 11,000 µg/L; DCE - 50,000 µg/L; methylene chloride - 20,000 µg/L; toluene - 5,500 µg/L; TPH - 50,000 µg/L
- Target temperature of greater than 84°C established across entire treatment cell at a depth of 14 - 34 ft below ground surface (bgs) within 35 days; bulk of the site (14 - 34 ft bgs) was maintained at or above 100°C for a period of at least 70 days until the beginning of active cooling
- All soil and groundwater samples were below the cleanup goals; many groundwater samples met the more stringent MCLs; an estimated 3,000 lbs of VOCs were removed
- The total project subcontract cost was approximately $3,800,000, including all aspects of the project from design, permitting, drilling, construction, operations, sampling, waste disposal, demobilization, and reporting; no additional cost data were provided
The Young-Rainy Star Center (formerly Pinellas) Northeast Area A, located in Largo, Florida, was the site of NAPL contamination in soil and groundwater. NAPL constituents included TCE, DCE, methylene chloride, toluene, and petroleum range organics. Contaminant concentrations were as high as 2,900,000 µg/kg for TCE in soil and 12,000,000 µg/L for methylene chloride in groundwater. Area A covered approximately 10,000 ft2 by 35 ft deep, for an estimated cleanup volume of 13,000 cubic yards. A combination of steam-enhanced extraction and ET-DSP was chosen by DOE to remediate the site because of the challenges at the site including low permeability sediments and the suspected presence of TCE DNAPL and oily LNAPL. The initial system of 66 wells included steam injection, ET-DSP, and combined wells. Results from additional soil sampling resulted in the installation of 12 shallow steam injection wells to improve the steam delivery and heat distribution in the subsurface in Area A.
After 4.5 months of operation, all soil and groundwater cleanup goals had been met, with many groundwater samples showing contaminant levels having been reduced to below the more stringent MCLs. During this application, several ways to improve system efficiency were identified. These included more rapid heating or flushing of the upper 10 ft of the treatment cell, lowering the water discharge rate, and using a more robust GAC system.