A former bus maintenance facility operated during 1960’s through 1980’s approximately 1,500ft from the environmentally sensitive Willamette River in the heart of Portland, Oregon. Operations resulted in groundwater contamination. Eighteen years of groundwater remediation resulted in no persistent reduction of measured PSH thickness. Heavily saturated soil with sequestered petroleum served as a secondary leaching source for PSH. The property was placed under contract. Regulatory closure then became an urgent matter.
Remaining 60,000ft2 PSH plume approximately 0.20ft thick prevented site closure. Proprietary surfactant/oxidant technology was selected to rapidly achieve closure goals. Three 5-day field events were scheduled. The initial phase desorbed PSH in the vadose zone to eliminate future leaching potential and to place the PSH into a micro-emulsion just under the critical micelle concentration prior to oxidative destruction. Measured PSH thickness was reduced to 0.01-0.03ft. This process was repeated for the second phase resulting in no measureable PSH (<0.01ft.). A final polishing phase resulted no visible sheen in any monitor well. Dissolved phase concentrations were degraded below the pre-treatment baseline.
The Oregon Department of Environmental Quality concurred that remediation goals had been met. The site was approved by the ODEQ and closed in time for re-development.
J. Scott Poynor, PG
Geologic Science and Technology Group, Inc.
Leonard C. Albright, President, Green Star Environmental, Lewisville, Texas, USA