Partner is engaged to assess and remediate an oil and natural gas production facility located in California, which is being shut down by the owner to allow for the sale and redevelopment of the site. The main oil production tank farm, gas plant, cogeneration system, and maintenance yard are approximately 7.6 acres in size. The site is under contract for sale to a new owner, and the terms of the agreement specify milestone dates, regulatory agency involvement, and clean-up levels.

Project Approach

To expedite site clean-up and transaction completion, assessment work was started while the facility was in operation. This required planning and coordination with the oilfield operator, the deconstruction/demolition contractor, the property owner, and the buyer. With areas of soil and soil vapor impact identified, remedial excavation work was started in areas that were not essential to oilfield operations. Following the ending of oil and gas production, full-scale remedial excavation work, concurrent with demolition activities were undertaken.

Partner’s primary remedial approach includes the targeted excavation of impacted soils, waste profiling, and off-site hauling for proper disposal. Secondarily, deep impacts to soil gas are being remediated by soil vapor extraction. Soils generated during demolition activities are tested on an ongoing basis to determine if they can be reused on site for backfill of the voids created by the removal of sub-structures or in completed remedial excavations. To minimize the volume of soil being removed for costly off-site disposal, excavated soils are separated at the time of excavation and stockpiled in separate areas, with one area designated for known impacted soils, a second stockpile area for discolored or odorous soils, and a third stockpile area for visually clean soils. Each of these soil classes is sampled and analyzed to determine which require off-site hauling using the frequency described in California EPA guidance documents. When necessary, expedited laboratory analysis was requested to allow for rapid re-use or off-site hauling of materials. During all excavation activities, removed soils are monitored for volatile organic compounds (VOCs) with a photoionization detector (PID) for compliance with SCAQMD Rule 1166. In addition, Partner measures and oversees dust control, with real-time dust monitoring to ensure compliance with SCAQMD Rule 1466.

With the limited space for demolition activities, excavation confirmation samples are collected and analyzed on an expedited basis to allow for rapid backfill. Depending on the location of the excavations, Partner’s geotechnical team provided guidance for sloping of excavations to verify safe and stable conditions and monitor for stability. Once an excavation is completed and confirmed to be remediated to the site-cleanup goals, Partner’s Geotechnical Team is immediately notified that backfill operations can begin at that location. Partner’s Environmental team also notifies the geotechnical staff when on-site soils are cleared for re-use so that geotechnical testing can be completed in our laboratory to determine the soil-specific criteria needed to obtain 95% compaction.

Partner geotechnical engineers provided guidance and approval for drying and otherwise remediating the base of excavation to prepare it for structural backfill. Partner-certified engineering technicians and laboratory staff tested backfill soils for approval for use as structural fill. Then they tested and monitored the placement of backfill soils to verify that they meet the project specifications for quality, in-place moisture, and density.

Using these procedures, Partner has minimized the soils materials being hauled off-site and reduced the amount of clean import needed for backfill materials. Further, we have been able to ensure that all soils are disposed of in the most cost-effective manner by separating materials suitable for daily landfill cover from those requiring formal landfill waste burial. Further, we have reduced the cost of soil import for backfill by facilitating Site reuse. Based on this approach, approximately 1/3 of the excavated soils to date (estimated quantity of 20,000 cubic yards) has been re-used on the site based on laboratory analytical results. The work has been conducted in a timely manner to the client’s satisfaction, with no complaints from the adjacent residences.

Project Highlights

• Time savings through concurrent demolition, excavation, and geotechnical backfill work.
• Cost saving through strategic soil stockpiling and sampling to allow reuse or lowest cost disposal, expedited completion of excavation and hauling activities with no monitoring exceedance or neighbor complaints.