COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

The existing underground storage tank (UST) systems include one 10,000-gallon and one 15,000-gallon gasoline USTs which were installed in 1999 (19 years ago). Based on the review of the recent integrity testing results, the database and regulatory agency records, there is no report that a subsurface release of petroleum hydrocarbons or other hazardous materials has occurred since 2011. However, based on the age of the UST systems (approximately 19 years), there is an increased risk of undetected releases, and this risk increases over time as the systems age. In addition, although integrity testing is a valuable tool to evaluate UST systems, such testing does not always detect low-level (slow) leakage from USTs and/or piping. PEI's experience indicates that even properly operated gas station facilities can experience undetected releases. The most definitive way to evaluate whether the on-site UST systems have leaked/failed is to conduct a subsurface investigation in the vicinity of the UST systems and fuel dispensers. Therefore, given the length of time since the prior subsurface investigations (9 years), the age of the UST systems (19 years), the shallow groundwater (4 feet below ground surface), and the potential for undetected releases from the on-site UST and dispenser systems, a baseline subsurface investigation of these systems would be prudent and is recommended. Subsurface investigation may be the sole measure to ascertain underlying soil and groundwater conditions and potential vapor intrusion at the subject property in relation to the long-term gas station operation. Based on the historical information review and conclusions, FR Environmental recommends a subsurface investigation. Scope of Work/Field Investigations A geophysical survey via ground-penetrating radar and electromagnetics will be conducted at the subject property to identify any potential subsurface anomalies indicative of remaining, out-of-use USTs, clarifiers, fill areas, drains area, and subsurface utilities in the proposed drilling area. A geophysical survey report will be included in the Phase II Subsurface Investigation Report. A drilling permit of 6 borings to groundwater will be obtained with San Joaquin County Environmental Health Department prior to any drilling activities on site (permit cost is approx. $912). A total of six soil borings will be advanced through a direct push Geoprobe drilling rig to a maximum depth of 15 or 20 feet or 5 feet below the first groundwater occurrence (whichever comes first, estimated depth to groundwater is approximately 5-10 feet bgs) near USTs and dispensers. Soil samples will be collected every 5 feet to 15 or 20 feet bgs. A total of six selected soil samples will be analyzed for full-range volatile organic compounds (VOCs) with fuel oxygenates and total petroleum hydrocarbons (TPH) as gasoline via EPA Method 8260B, and TPH as oil and diesel range organics via EPA Method 8015. The six proposed soil boring locations map is attached. A total of six groundwater samples will be collected through a temporary well point should groundwater be encountered prior to 15 or 20 feet bgs, and analyzed for full-range Fulcrum Resources Environmental 574 W. Grant Line Road, Tracy, CA 95376 Phase II Work Plan 3