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PUBLIC NOTICE . Proposed No Further Action Determination Former ARCO Station No . 6100 25775 S . Patterson Pass Road , Tracy , San Joaquin County Case #390265 GeoTracker Global ID . T0607700192 The Central Valley Regional Water Quality Control Board ( Central Valley Water Board ) invites public comment on the proposed No Further Action Determination and closure of the Former ARCO Station No . 6100 underground storage tank case , located at 25775 S . Patterson Pass Road in Tracy , CA ( site ) . A map showing the site investigation area and the current remaining extent of petroleum impacts to groundwater above water quality objectives is attached as Figure 1 . PUBLIC COMMENT PERIOD . 17 February 2020 through 22 April 2020 (65 days ) CASE SUMMARY . The site property is currently occupied by an active Mobil -branded fueling station located west of the intersection of South Patterson Pass Road and Interstate 580 in Tracy , California . Aboveground facilities consist of a station building containing a mini - mart , two dispenser islands , associated product lines , and a restroom building . The site currently utilizes four 10 , 000 -gallon gasoline underground storage tanks ( USTs) . An on -site domestic water supply well , sourced in a deep aquifer located between 396 and 536 feet below ground surface ( bgs ) , is used as a source of drinking water at the site . The majority of the site is paved with an asphalt parking lot and has common landscaping throughout . The area surrounding the site is undeveloped land zoned for agricultural or industrial use . According to the United States Geological Survey , the elevation of the site is approximately 290 feet above mean sea level sloping down toward the southeast . The closest open bodies of water are the concrete- lined California Aqueduct , which is located approximately 1 , 000 feet northeast of the site , and two intermittent streams located northwest and southeast of the site at approximate distances of 1 , 000 and 1 , 500 feet , respectively . Excavation and assessment activities completed between 1990 and 2018 generated 381 soil samples from 122 locations collected at depths ranging from approximately 2 . 5 to 200 feet bgs ; 25 shallow zone wells with screen depths ranging between 9 . 5 and 88 feet bgs and 13 deep zone wells with screen depths ranging between 43 . 5 and 115 feet bgs were also installed . The majority of elevated soil concentrations around the former USTs and associated product piping suggest a fuel release occurred beneath the dispensers , product lines , and /or former USTs . Approximately 2 , 500 cubic yards of impacted soil were excavated during the gasoline UST replacements in February 1991 , and approximately 315 tons of soil were excavated during replacement of dispensers and product piping in February 2002 . Approximately 284 gallons of light non -aqueous phase liquid ( LNAPL ) were removed from site monitoring wells between September 2000 and March 2010 . Measurable LNAPL has not been observed at the site since February 2015 .