ARCHIVED REPORTS XR0010670 - Laserfiche WebLink

Home Browse Search

CALIFORNIA GEOPHYSI ,4!NU,GR VPI' INC. O Box 578341, Modesto, CA 95357 ' ' ' ` ' "" ,.� Tel (209) 527-1247 March 19 , 1996 H AER _09 AN 10' 54 Fax (209) 527-4810 ' Public Health Services San Joaquin County P.O. Box 2009 Stockton, Ca 95307 RE: Activity Report March, 1996 Darpetro Service Station 749 E. Charter Way Stockton, Ca. Site # 1060 We presented a work plan to the Health Department on March 15, I 1995, which defined several areas of investigation. This plan was approved by a letter of August 1 , 1995. ' Between February 26th and March 4th, 1996 a series of seven (7) borings were drilled. One boring, B-2 was for testing the contamination in the northeast corner of the gas station property. ' Boring VW-2 was drilled to a depth of 62 feet which is about 14 feet below the water table surface at present. This boring was converted to an air sparging well to be used in the remediation. The well was constructed by placing 5 feet of slotted casing at the bottom of the well from 61 feet to 58 feet bgs. Coarse aquarium sand was placed around the slotted casing and 2 feet above it. Then a hydrated bentonite plug was place from 56 to 53 feet bgs. The purpose of the plug is to force the injected air out into the formation and not allow the air to rise in the annulus which would be the easiest path to the surface. The well was completed by placing cement above the plug to the surface. I The air will be injected into a poorly sorted sand which should accept the air without difficulty. The air will perform two functions. First, it will act as a stripping agent to remove some of the groundwater contamination from the water. Second, it will add oxygen to the groundwater which will promote active biodegration. The in]ected air will be removed from the subsurface by the vapor extraction system which was also installed. Borings VW-1 , VW-3 , 4, 5 and 6 were drilled to a depth of 45 feet bgs which is just above the present groundwater level . Each boring was converted into a vapor extraction well by placing approximately 35 feet of 2 inch Schedule 40 PVC slotted casing in the boring and placing coarse aquarium sand in the annulus around the slotted casing. A hydrated plug was placed above the sand in the annulus and the remainder of the annulus was filled with cement. The plug and the cement are located opposite a clay unit I' Page 1