Dual Phase Extraction, Reliable Equipment Company, Humboldt County, California

SHN Consulting Engineers & Geologists, Inc. has been awarded the Engineering Achievement Award by the California Water & Environment Association (CWEA) for its work on this Dual Phase Extraction Project.

This site had an extensive release of total petroleum hydrocarbons as gasoline that included the presence of free product floating on the shallow aquifer underlying the site. SHN designed a dual phase vapor extraction system and performed a feasibility study at the site. Results of the study indicated that the vapor extraction system was suitable for remedial use at the site. SHN submitted a Corrective Action Plan Addendum to the RWQCB, which was approved, and the system was installed. After three years of operation, hydrocarbon concentrations in the source area were reduced by 98%, and the system was subsequently shut down. The site is now in a monitored natural attenuation program. Initial hydrocarbons extracted were incinerated by thermal oxidation prior to discharge into the atmosphere. After one year of operation, vapors extracted from the dual phase system were low enough that they required no further treatment and the thermal oxidation unit was taken off line. Groundwater extracted by the system was discharged into a municipal sanitary sewer.

SHN has provided site investigation, engineering design, and installation and operation and maintenance of remediation systems for various ConocoPhillips (formerly Unocal/Tosco) bulk plants, throughout far Northern California and Southern Oregon, including sites in Eureka, Weaverville, Crescent City, Garberville, Redding, Susanville, and Fort Bragg, CA and Coos Bay, OR

Remediation and Groundwater Monitoring Activities, Former Tosco/Unocal Bulk Terminal #0201, Eureka, California.

Since 1998, SHN has performed numerous types of remediation work at this terminal including groundwater monitoring and reporting, underground storage tank (UST) removal, installation and maintenance of a stormwater carbon treatment system, two biosparge blower units, an air sparge system, passive free product recovery, and new stormwater drainage pipe placed within existing groundwater contamination. SHN designed and installed a dual-phase extraction system. The system design includes an innovative in-well phase separation which separates dissolved phase contamination and free product from groundwater. The system design was awarded the 2004 Project of the Year by the American Society of Civil Engineers, Northcoast Branch.

SHN currently performs biannual groundwater monitoring and all O&M activities at the site. Monitoring of the site includes groundwater monitoring wells for hydrocarbons, chlorinated solvents, and free product. SHN negotiated leaving in place a Bunker C plume located under several large above ground storage tanks (ASTs) using institutional controls to mitigate impacts to the environment. SHN recently negotiated with the RWQCB for the removal of approximately 30 monitoring points from the program.

Remedial Assessment, Sparge System, and Biovent System, Former Tosco/Unocal Bulk Plant #0848, Weaverville, California.

In 2000,SHN was retained to review existing site data and evaluate the remedial actions taken at the plant. The existing remediation equipment was a remediation trench equipped with an SVE/AS system (installed by others). SHN conducted a respirometry test in the source area (using the SVE trench) and in adjacent off-site wells. The respirometry testing evaluated bioventing at the site with the existing blower equipment, and estimated degradation rates for hydrocarbons. As a result of the respirometry testing, SHN converted the system over to a bioventing/biosparging mode. SHN also recommended pulsing the air injection into the trench to reduce operational costs and reduce the amount of preferential pathways in the formation. Part of the performance evaluation also identified the adjacent bulk plant as an additional source of dissolved phase hydrocarbons at the facility. SHN recommended operating existing and any future remedial systems in an injection vs. extraction mode to, limit on-site migration from the adjacent property.

Currently SHN conducts O&M of a biosparge/biovent blower unit. Monitoring of the site includes groundwater-monitoring wells for dissolved phase hydrocarbons and free product. SHN has selected an ozone sparge system to enhance remediation of MTBE at the facility and prevent off-site migration. SHN is currently in the design phase of the ozone-sparge system with construction slated to begin in the summer of 2004.

Site Investigation and Remediation, Former Tosco/Unocal Bulk Plant #0140, Crescent City, California.

SHN conducted a review of site data, installed additional off site monitoring wells (including one within a State Wildlife Refuge), and conducted additional site investigations using direct push technology. As a result of these site investigations, SHN identified a remaining on site source area in the vicinity of the oil/water separator. The separator was replaced, contaminated soils removed, and Oxygen Releasing Compound (ORC) was placed in the excavation cavity to enhance the natural degradation of hydrocarbons. SHN is currently assessing the effectiveness of ORC at the site to determine the next phase of remediation in another portion of the site. In addition, SHN has identified the adjacent bulk plant as an upgradient source for dissolved phase hydrocarbons on site.

Underground Storage Tank Removal, Remedial Action, and Ozone Sparge System, Former Tosco/Unocal Bulk Plant #0228, Garberville, California.

SHN conducted remedial excavation and underground storage tank removal at the former bulk plant in Garberville, California. The site historically operated as a bulk plant for the storage and distribution of petroleum products including gasoline, diesel, and

motor oil for over 40 years. Several ASTs and 4 USTs were used at the site, 2 of which had been previously removed.

Following excavation, SHN conducted an additional site investigation. The objective of the investigation was to assess soil and groundwater conditions, including testing for petroleum hydrocarbons, off-site and upgradient of a creek which is located to the south of the property.

SHN recommended continuing groundwater monitoring at the site. SHN further suggested that rushing into an interim corrective action program near the creek could be an uncertain process with limited potential for contaminant reduction. Therefore, SHN recommended implementing pilot testing followed by design and installation of a full-scale remedial system as the most efficient, productive, and cost effective method to prevent impacts of MTBE contamination in the adjacent creek.

SHN conducted SVE and air sparge pilot studies. The results of these studies indicated a more aggressive remedial system would be required to remediate MTBE. An ozone sparge system was identified as the preferred remedial solution.

SHN designed and supervised the installation of an 18-point ozone sparge system to remediate MTBE and prevent any impacts to the creek, which flows into the Eel River. After 24 months of operation, an approximately 75% reduction of MTBE and benzene in groundwater concentrations has been observed. SHN iscurrently conducting site operation and maintenance, and periodically modifying the sparge system to maximize efficiency.

Site Investigation Activities, Former Tosco/Unocal Bulk Plant #0629, Redding, California.

SHN reviewed site data, located additional off site monitoring wells, conducted a site investigation in the vicinity of a public sanitary sewer line, and identified an off site source for dissolved phase MTBE and hydrocarbons in groundwater in site wells. In addition, SHN facilitated the replacement of a down gradient domestic drinking water well that was impacted by the MTBE plume with a connection to the municipal water delivery system. Based on the results of groundwater modeling, SHN has determined that the adjacent bulk plant is responsible for the MTBE plume and that others remediate the MTBE contamination on site. SHN has prepared a work plan to investigate on-site sources to refine the model to demonstrate that responsibility belongs to the adjacent site. Fieldwork will be scheduled as soon as the work plan is approved by the regulatory agency.

Site Investigation and Corrective Action Plan, Former Tosco/Unocal Bulk Plant#0220, Fort Bragg, California.

In 1998, SHN conducted a subsurface investigation at the Former Tosco/Unocal Bulk Plant #0220, located in Fort Bragg, California. The objectives of this investigation were to identify the source area for the diesel contamination in the northern portion of the facility, and to conduct feasibility testing on bioventing and biosparging at the facility. As a result of the pilot testing program, a design for bioventing diesel in the vadose zone and ozone sparging gas and diesel in the groundwater has been prepared. SHN’s remedial action plan was approved by the regulatory agency and implemented in winter of 2003/2004. SHN used an MIP probe to confirm site lithology and determine the optimum depth for sparge point placement. SHN used direct push technology to install the sparge wells to minimize waste generation and speed the installation process. System start-up occurred in Spring 2004, and SHN is currently performing O&M of the system.

Site Investigation Activities, Former Tosco/Unocal Bulk Plant #0769, Susanville, California.

SHN reviewed site data, located additional off site monitoring wells, and demonstrated that an adjacent municipal well screened in the deeper aquifer has not been impacted by site activities. SHN is also reviewing the existing owner’s response to a spill and subsequent remedial activities, which occurred after Tosco/Unocal ownership, and recently proposed preparing an exit strategy for ConocoPhillips from the site.

Site Investigation Activities, Tosco/Unocal Bulk Plant #0954 and Terminal #0124, Coos Bay Oregon.

SHN performed a focused site investigation at a former Union 76 bulk plant in Coos Bay Oregon. The plant is located adjacent to the bay and wetlands areas. A Geoprobe® was used to collect soil and groundwater samples in an area adjacent to current and former above ground tanks and pipelines. SHN also oversaw a lead and asbestos survey of the entire facility. This information was used to determine appropriate demolition techniques in order to protect site workers and the adjacent residents. SHN currently performs quarterly groundwater monitoring at the site. SHN recently installed an air sparge trench to prevent any impacts to Coos Bay. SHN will be making recommendations to modify the original design (by others) with the addition of air sparge points to maximize protectiveness.

As its Northern California Environmental Engineering Consultant, SHN has provided a multi-disciplinary approach to the state's environmentally hazardous sites. Five sites were old facilities with storage tanks that had leaked or spilled, causing petroleum hydrocarbon contamination to the soil and/or groundwater.

In one case, facility ownership was scheduled to be transferred from the state to a local government entity. Because the state needed to expedite the transfer of this property, SHN initiated a fast track closure program that included overexcavation of 150 yds of contaminated soil for off-site bioremediation and removal of petroleum product and vent piping.

SHN was successful in fast tracking this important property transaction and achieved a site closure in less than 6 months. Other sites involved altering existing monitoring activities to characterize and subsequently remove or mitigate contamination. SHN has a reputation for fast, accurate site characterization and closure.