Former Retail Store, Culver City, California

The former client property and existing UST system are currently owned and operated by a private party. MTBE was discovered in wells supplying drinking water to the City of Santa Monica (the Charnock wellfield) in the fall of 1995. In correspondence dated June 19, 1997, the RWQCB and the United States Environmental Protection Agency Region IX, required that potentially responsible parties investigate their sites. Because our client previously owned USTs at the site, located approximately 2,500 feet south of the Charnock wellfield, they were named a potentially responsible party. The site is designated as PRP Site No. 1 by the agencies.

We were initially contracted by our client in 1997 to respond to the Environmental Protection Agency Region IX and RWQCB in response to the MTBE contamination and shut down of the City of Santa Monica Charnock Wellfield. The investigations initiated after 1997 included:

• 18 monitoring wells installed at site
• Screened in different water-bearing zones
  • ~20 MSL (perched zone)
  • 5 to 20 MSL (Shallow Aquifer)
  • 60 MSL ( Upper Silverado )
• Active quarterly ground water monitoring since 1997
• Soil sampling conducted in 1997, 2000, 2001, 2002
  • Majority of samples in vicinity of dispensers; few in tank areas
  • Soil analyses prior to 2000 characterized by:
    • Weathered, non-oxygenated hydrocarbons
    • Low to ND levels in shallow soils (>40 feet MSL)
  • Soil analyses from 2000 and later characterized by elevated levels of oxygenates (MTBE and TBA) in shallow soils

Remediation activities undertaken at the site have included:

• 2000 : Interim Soil Remediation
  • Excavated approximately 1,050 yards of soil from locations of dispenser islands
  • Soil impacted primarily with TPHg, with average MTBE concentrations three orders of magnitude lower
• 2002: Limited Ground Water Extraction at MW-3 (Shallow Aquifer)
  • Limited mass in shallow aquifer indicated by decline in MTBE concentrations to less than MDL after less than 8 hours of pumping
• 2006: Dual Phase Extraction
  • Applied vacuum at MW-2 (26" Hg for 48 hours)
  • April, June, July, August (September)
  • Negligible lateral influence
  • Cumulative Recovery (4 events):
    • ~1,000 gallons of water
    • ~600,000 scf of vapor
    • ~70 lbs of VOC (~11 gallons of gasoline)

The dual phase extraction events described above were initiated in response to requirements of the RWQCB directives following recent detections of elevated MTBE (13,000 µg/L) and TBA (120,000 µg/L) in perched ground water underlying the site.

The concentration trends observed during the dual phase extraction events did not indicate significant depletion of the source mass. This information and the widespread detection of ethanol vapors suggest that recent releases have occurred at the site and that the existing impacts are derived from post-1997 releases. The recent release(s) are possibly associated with the Super Petrol line and dispenser removal or tank repair performed from March to August 2000. Nevertheless, Our client's stated goals for this site are to:

• Proactively respond to the RWQCB regarding the elevated TBA
• Mitigate the threat posed by the elevated TBA with respect to the City of Santa Monica planned Charnock Wellfield treatment facility construction
• Mitigate potential impacts to the perched zone prior to commingling with the Shallow Aquifer
• Successfully argue post-1995 releases are source of current contamination

Future activities planned in response to the elevated MTBE and TBA include:

• Delineating the dissolved plume within the perched zone
• Evaluating natural attenuation within the perched zone
• Evaluating hydraulic conditions in the vadose zone

Retail Store, Culver City, California, Major Oil Company

We took over responsibility for this site in 2004 because of our experience with and sensitivity to issues related to regional MTBE contamination. The site is approximately 2,400 feet southeast of a City Wellfield. Remediation had been ongoing at the site since early 1990. At this time all USTs and piping have been removed from the site as well as the underground components of the hydraulic containment system. The site is owned by our client, fenced and unoccupied. Our activities include continued monitoring of wells screened in the drinking water aquifer (Silverado), demolition of the aboveground portion of the remedial system formerly operated at the site, and participation with other regional esponsible parties in a regional Monitored Natural Attenuation study in Culver City, California. Soil confirmation sampling identified petroleum hydrocarbon impacts generally at 65 ft below ground surface (located approximately 15 feet below current water table. RWQCB is the responsible agency for the ground water investigation and remediation at this site and may require additional assessment once the City wellfield is brought back on-line and water table declines. The anticipated water level at that time will be approximately 85 ft below ground surface.

Truck Maintenance Facility, Northern Sacramento Valley, California, Major Transport Company

We are currently managing environmental monitoring activities at a truck maintenance and fueling facility in the northern Sacramento Valley, California. The facility was formerly owned and operated by our client. An array of 15 domestic and municipal wells and 24 ground water monitoring wells is monitored quarterly. The well arrays access six distinct wetted zones. We have prepared a contingency plan as directed by the State of California to present proposed environmental management responses to potential changes in ground water conditions at this site. The site is managed collaboratively with consultants for the current owner of the site. The site is surrounded by other sites having past fuel hydrocarbon releases, and dissolved-phase COCs are believed to be co-mingled in more than one wetted zone in the vicinity. Future site characterization work will address this issue.

Confidential Client, Large Oil Company: One of our professional staff was responsible for establishing remediation engineering capability for the Northern California region on a national project for a large oil company client. His responsibilities included soil and ground water system design and installation, updating existing remediation systems, junior staff training, and providing assistance to other company offices in the design and installation of advanced oxidation processes for soil and ground water remediation.

He designed an advanced oxidation and bioremediation process and equipment, a fully automated soil and ground water multi-gas and liquid injection system adopted by the company as the lead technology for remediation at all sites in the national project, and assisted three company regional offices in construction and installation of these systems.

He also designed three soil and ground water remediation systems using advanced oxidation and bioremediation systems for other project sites. He modified four existing soil vapor extraction CATOX systems to include ozone sparging for ground water remediation. He designed two soil vapor extraction systems to assist existing ozone sparge units. He assisted regional offices in design and installation of six advanced oxidation and bioremediation systems. He designed a free product recovery system for another project. In addition, he conducted six subsurface resistivity-induced polarization surveys to further characterize soil contamination.

Confidential Client, Regional Oil Company : We provided environmental consulting services for this regional oil company at 54 sites, including operating retail gasoline service stations, truck stops, and sites now owned by other parties. Geographically, we handled sites from Bakersfield to Redding, including several in the San Francisco Bay Area. The examples below are representative of work conducted for this client.

• Retail Gasoline Service Station: At an operating gasoline service station site in Northern California, we operated and maintained a ground water pumping and soil vapor extraction system to remove hydrocarbons from the subsurface. The system used a catalytic oxidizer for vapor emissions control. After 6 months of operation, the results of confirmation borings and quarterly monitoring indicated that cleanup goals had been achieved.
  
  We prepared a Closure Request Report containing data on the amount of hydrocarbons recovered from soil and ground water, the maximum amount estimated to remain, an assessment of exposure risk to potential receptors, historic ground water quality monitoring data, and a review of ambient ground water quality. After review by the RWQCB, closure was granted. We then assisted the client with disposal of stored waste, disassembly of remediation equipment, and proper abandonment of monitoring wells.
• Retail Gasoline Service Station: At a former gasoline service station in Central California, we designed, permitted, installed, and operated a remediation system that included ground water pumping and soil vapor extraction, which used thermal oxidation for emissions control. After operating for 11 months, the system had recovered approximately 12,474 pounds of hydrocarbons. We then had the emissions permit modified for activated carbon use to control the reduced emissions until remediation was complete, and the thermal oxidation unit was then used at another site.

Confidential Client, Major Oil Company : One of our professional staff managed a 3-year soil vapor extraction research project for a major oil company. The objective of the project was to assess the effectiveness of soil vapor extraction as an alternative for the remediation of soil and ground water impacted by petroleum hydrocarbons. Research fieldwork was undertaken at two operating retail service station sites with documented petroleum hydrocarbons in underlying soil and ground water. The scope of work included the following:

• Finalization of a scope of work to assess the extent of petroleum hydrocarbons in soil and ground water.
• Drilling and installation of approximately 20 ground water monitoring wells.
• Drilling and installation of seven multi-level vadose zone monitoring wells. Each vadose zone monitoring well contained a vapor port and thermocouple at three discrete depths for collecting vapor samples and measuring pressure and temperature.
• Sampling and laboratory analysis of soil and ground water for petroleum hydrocarbon constituents.
• Interpretation of field and analytical data and design of remedial systems, including ground water pump and treat and soil vapor extraction systems.
• Drilling and installation of ground water recovery and soil vapor extraction wells.
• Monitoring and data acquisition during remedial system operation.
• Preparation of reports documenting findings, conclusions, and recommendations regarding the effectiveness of soil vapor extraction at the research sites.
• Preparation of closure plans for the research sites.