Soil Vapor Survey, Indoor Air Sampling, and Soil Borings at Pepper Oil Company Facility and SoCal Truck Stop

The proposed project would allow for the geotechnical investigation and geophysical surveying of an approximately 2.6-acre site owned by the Pepper Oil Company, Inc. (Applicant) in the city of National City, California. The proposed surveying would be carried out as part of a Corrective Measures Study, per request of the California Department of Toxic Substances Control (DTSC), due to the Department’s regulatory oversight for the investigation and remediation of the proposed site. The northern portion of the proposed project site operates as the SoCal Truck Stop (SCTS), which includes a fueling station and convenience store; the southern portion of the site, which was historically used as an underground fuel storage and transfer facility, is currently utilized by the Applicant for chemical mixing of emulsion products, the storage of retail materials for sale at SCTS, and the dispensing of kerosene. Both portions are owned and operated by the Applicant. In 2004, a soil vapor survey of the Pepper Oil Company and SoCal Truck Stop (STCS) facilities were conducted to assess the extent and concentration of volatile organic compounds (VOCs) in the vadose zone and to identify potential areas of concern. The previous survey included 36 soil vapor sampling locations at Pepper Oil and 30 soil vapor sampling locations at the SCTS facility to a depth of five (5) feet below ground surface (bgs). The results of the soil vapor sampling indicated that, at the Pepper Oil portion of the site, 29 of the 36 locations did not contain detectable concentrations of VOCs; seven (7) of the 30 sampling locations within the SCTS portion of the site did not contain detectable concentrations of VOCs. The soil vapor sample containing the highest concentrations was located in an area where two (2) former underground storage tanks had been removed, which also coincides with the areas of the highest soil and groundwater contamination identified during soil and hydropunch sampling. A second round of soil vapor sampling at both sites was also conducted in 2016, in which a total of 35 soil vapor samples were collected. Concentrations of VOCs at and/or above the reporting limit were not detected at 10 of the 35 sampling locations. Activities associated with the proposed investigation and surveying would include, but not be limited to, subsurface soil borings, soil vapor sampling points, and methane assessments to help develop a remediation plan for the site in vicinity of the former underground storage tank locations. The proposed project would specifically consist of the drilling and sampling of approximately four (4) temporary soil borings and approximately 43 temporary soil vapor sampling points into the subsurface to a depth of up to approximately five (5) feet bgs. Subsurface methane assessments would also be conducted at each soil vapor sampling point, as well as at approximately six (6) locations within the SCTS convenience store, to evaluate if methane is generated as a byproduct of the petroleum hydrocarbons degradation process. Following the completion of all borings and soil vapor sampling, borings and vapor sampling points will be backfilled and the surface restored to match the existing surface. Work at the proposed soil vapor sampling locations is anticipated to occur in Fall 2025 and would take approximately one (1) week to complete. Additional sampling and analysis may be conducted, as necessary, dependent on initial sampling results. A work crew and mechanical equipment, including but not limited to a drill and rotary hammer, would be required to complete the proposed sampling. It is anticipated that approximately one (1) drum of soil cuttings would be produced as waste. The Applicant is responsible for the proper handling and disposal of drilling spoils and other associated debris. Due to its nature and limited scope, construction of the proposed project would generate a minor amount of vehicle trips and would require limited use of equipment. Therefore, impacts related to air quality, greenhouse gas emissions, and transportation and traffic are not anticipated to occur. Furthermore, the Applicant would be responsible for complying with all applicable federal, state, and local laws regarding construction demolition debris, hazards and hazardous materials, and stormwater.