Soil Vapor Extraction System at Commencement Bay, South Tacoma Channel (Well 12A), Phase 2, Tacoma, Washington

Site Name:

Commencement Bay South Tacoma Channel Superfund Site


Tacoma, Washington

Period of

Status: Ongoing
Report covers - 8/92 to 2/94


Full-scale cleanup
(Report documents demonstration phase)


Environmental Science & Engineering, Inc.

Soil Vapor Extraction - 22 wells used for vapor extraction, air inlet, and observation - Vapor-phase carbon adsorption (GAC) used for treatment of extracted VOCs - GAC beds regenerated on site with low pressure steam - Design flow rate for extraction system of 3,000 standard cubic feet per minute (scfm)

Cleanup Authority:
CERCLA, Local Requirements
- ROD Date: 3/85

SIC Code:
2851 (Paints, Varnishes,
Lacquers, Enamels,
and Allied Products)
Point of Contact:
Phil Stoa
Remedial Project Manager
U.S. Army Corps of Engineers
Seattle District

Chlorinated Aliphatics trans-1,2-Dichloroethene (DCE), 1,1,2,2-Tetrachloroethane (PCA), 1,1,2,2-Tetrachloroethene (PCE), Trichloroethene (TCE) - Average VOC concentrations in top 25 feet of soil ranged from 10 to 100 mg/kg -Average PCA concentrations in soil borings ranged from 6,200 at 30 feet depth to over 19,000 mg/kg at 40 feet depth - Approximately 571,000 lbs of VOCs present in unsaturated zone

Waste Source:
Storage - Drums; Other: Pour off from Processing Tanks

Type/Quantity of Media Treated:
Soil - Volume of contaminated soil reported as 98,203 cubic yards, based on an area of 66,300 ft2 and a depth of 40 ft - Upper aquifer (50 ft thickness) consists of unconfined sand and gravel - Surface soil permeability ranges from 2.8 to 3.6 x 10[Sup -3] cm/sec - Separate liquid phases of VOCs in soil and groundwater suspected - Tar-like compounds in soil suspected

Purpose/Significance of Application:
Application of soil vapor extraction with an on-site solvent recovery system; relatively large volume of contaminated soil; possible presence of separate liquid phases of VOCs and tar-like compounds in soil.

Regulatory Requirements/Cleanup Goals:
- No specific cleanup goals identified in Record of Decision - Local permit required for air emissions - Performance objective for air treatment system set at 99% removal

- Air discharge limits specified as follows: PCA0.149 lbs/hr PCE0.095 lbs/hr TCE0.344 lbs/hr

- No results provided for quantity of contaminants removed during demonstration phase - Computer modelling results show predicted removal rates for VOCs as a function of time - Pilot-scale results indicated that 3 to 4 lbs/day/well of VOC could be removed from the upper 30 feet of soil - No results provided for air emissions - treatment system removals or mass discharge rates - Problems were experienced with the operation of the solvent recovery system - Condensed mixed solvents formed an emulsion which did not readily separate from the water

Cost Factors:
Total Capital Cost - $5,313,973 (as of 5/94) (no breakdown of costs available) Annual Operating Costs - $100,000 (estimated) (no breakdown of costs available)

The Commencement Bay site was used from 1927 to 1964 for waste oil recycling, paint and lacquer thinner manufacturing, and solvent reclamation and hundreds of drums of material were stored at the site. Leaks from these drums, as well as the dumping of wastes directly on the ground and overflows from the solvent and waste oil recycling tanks, resulted in contamination of the soil and groundwater at the site. The primary contaminants of concern at the site included DCE (trans-1,2- dichloroethylene), PCA (1,1,2,2-tetrachloroethane), PCE (1,1,2,2- tetrachloroethylene), and TCE (trichloroethylene). VOC soil concentrations range from 10 to 100 mg/L.

A full-scale SVE system was constructed in 1992. Operation testing of this system began in August 1992 and this report covers the demonstration phase of the project. The SVE system includes 22 vapor extraction wells. Granular activated carbon (GAC), used to treat extracted vapors, is regenerated on site using low pressure steam, which was subsequently condensed. The on-site solvent recovery system is used to separate VOCs from the condensate.

As of May 1994, the total capital costs and annual operating costs for this application were $5,313,973 and $99,810, respectively. While no performance data are available at this time, it was noted that the SVE system seems to be performing adequately. Several problems were experienced in the operation of the solvent recovery system. Condensed mixed solvents formed an emulsion which did not readily separate from the water. The report identifies a need to perform pilot testing of the solvent recovery system to ensure that separation of VOCs and water can be performed.