ARCHIVED REPORTS XR0001489 - Laserfiche WebLink

Home Browse Search

C A M B R I A w installed seven onsite groundwater monitoring wells (MW-I through MW-7) and four offsite monitoring wells (MW-8 though MW-11) TPHg was detected in soil from these borings and wells at concentrations ranging from ND to 2,500 ppm and benzene at concentrations ranging from ND to I I ppm These activities are also summarized in GTI's October 9, 1990 Environmental Assessment Status Report In April 1992 GTI installed four soil vapor extraction (SVE) wells (VEW-1 though VEW-4) and conducted an SVE pilot test These results are described in GTI's September 16, 1992 Summary Report of Soil Vapor Extraction Test Sampling Activities In September 1993, GTI Installed five offsite monitoring wells (MW-13 though MW-17) Soil from these borings contained TPHg at concentrations ranging from ND to 3 7 ppm and benzene at concentrations ranging from ND to 0 23 ppm During the first groundwater sampling event in September 1993, the wells contained TPHg concentrations ranging from ND to 12,000 parts per billion (ppb) and benzene concentrations ranging from ND to 2,700 ppb This investigation is documented in GTI's December 16, 1993 Summary Report of Drilling Activities • Separate phase hydrocarbons (SPH) have historically been detected in well MW-I, but no measurable SPH has been observed since March 1993 From May 1989 to December 1989, approximately 45 gallons of SPH were recovered from well MW-1 An SVE test was conducted in June 1992, and the SVE system began operation in August 1995 SECOR International Incorporated of Huntington Beach, California detail this in their September 12, 1996 Soil Vapor Extraction System Installation and Start-up Report Between January 1996 and March 1998, the SVE system removed approximately 6,250 pounds of TPHg The SVE system was shut down March 9, 1998 due to declining influent concentrations and rising groundwater level Quarterly groundwater monitoring and sampling have been performed at this site since May 1989 Currently, depth to groundwater ranges from approximately 19 to 22 fbg Since 1992, groundwater has risen approximately 20 feet Groundwater flow direction at this site has been variable, but generally to the north or northeast WORK TASKS Over-excavation- Based on field observations and preliminary analytical results from tank removal and soil sampling activities performed on June 25, 1999, over-excavation is 40 warranted in the eastern half of the tank pit and beneath the northwest, southwest, and 241-1399 2