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Stockton Promenade—N. Edison Street USTs& Utility Corridors Page 5 Underground Storage Tank Removal Report June 8,2009 WKA No.7345.09 On December 5, 2008, Johnson Petroleum began excavating to expose the surface of UST#1 (State Board of Equalization ID#039-0517543) under SJCEHD Permit No. SR0055962. All excavated soil encountered was field screened using a photo-ionization detector(PID)to determine suitability for use as backfill or for off-site disposal. Once the surface of Tank#1 was reached, excavation continued in order to expose the UST sidewalls. Soil removed from the excavation exhibited hydrocarbon odors, discoloration, and evidence of elevated PID readings. A Lower Explosive Level (LEL)meter was also used to measure oxygen levels in the UST. Access to the interior of Tank#1 was gained through accessible fill ports in the roof of the UST. The openings were vented and the atmosphere inside the UST was monitored for LEL,percent oxygen, and PID readings during the cleaning and removal process. Johnson Petroleum cleaned the interior of the USTs by removing all liquid products remaining in the UST. The interiors of the USTs were then pressure washed twice,with soap sprayed between each washing event. The atmosphere inside the UST was rendered inert using dry ice to displace the UST atmosphere. A discussion of the conditions of the UST and confirmatory sampling activities are provided in Sections 2.4 and 2.5. 2.2 Additional UST Removals During initial excavation and removal of Tank#1, an approximately 550-gallon UST(Tank#2) was identified immediately to the east of the first tank. Tank#2 was constructed of corrugated- steel that was galvanized on the interior and filled with soil. Soil from inside Tank#2 was removed and stockpiled on-site for disposal profiling. Upon field approval by Mr. Ray von Flue, SJCEHD, Tank#2 was crushed on-site, and hauled off as scrap metal for recycling. Confirmation soil samples were then collected from beneath the former UST and from the soil stockpile. In early January 2009, Power Engineering Contractors, Inc. (Power) conducted underground utility excavation activities in the vicinity of the two removed USTs to abandon and relocate a nearby fire hydrant and water supply line. Power notified WKA of the presence of two additional USTs (Tank#3 and Tank#4) found in the same area as the first two USTs. These two additional USTs were ultimately removed on January 15, 2009, following the same procedures as Tanks#1 and#2, and under the same SJCEHD permit. Abandoned underground petroleum piping was identified immediately south of Tanks#3 and #4. The piping extended northward from beneath the adjoining WOTOA parking lot and then a 90- degree east to run approximately six feet south of and running parallel to Tanks#3 and#4.