ARCHIVED REPORTS XR0001049 - Laserfiche WebLink

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AM B R I A Ms Vicki McCartney April 6,2006 PREVIOUS WORK 1989 Subsurface Investigation and UST Removal During February 1989, Delta Environmental Consultants (Delta) drilled eight soil borings to assess site conditions prior to UST removal and replacement activities In November 1989, four USTs were excavated and removed Soil samples were collected from former tanks and product Iine trench excavations 1989-1990 Well Installations Between December 1989 and January 1990, Delta installed groundwater monitoring wells MW-1 through MW-7 Underground piping was installed to wells MW-2 through MW-5 and MW-7 for future remediation Two additional groundwater monitoring wells (MW-8 and MW-9) were installed in March 1990 1990 Groundwater and Vapor Extraction Tests During March 1990, groundwater pumping and vapor extraction tests were conducted to obtain hydrogeologic data, hydrocarbon concentration levels, and flow parameters for remedial system design 1990 Free-Product Skimmer Installation In April 1990, a free-product skimming system was • installed to collect free product from well MW-2 The skimmer was later moved to well MW-7 Approximately 180 gallons of free product were skimmed from the wells 1991 Well Installation Off-site groundwater monitoring well MW-10 was installed in July 1991 1992 Soil Vapor Extraction (SVE) System Installation An SVE system was installed and then operated full time from September 1992 to September 1993 During the first year of operation, the system removed an estimated 14,980 pounds of hydrocarbons from the subsurface The system operated intermittently through November 1996, removing a total of 17,628 pounds of hydrocarbons from the subsurface 2000 Subsurface Investigation During March 2000, four cone penetrometer test (CPT) borings (CPT-I through CPT-4) were advanced on site Cambria collected depth-discrete groundwater samples from each of these borings Total petroleum hydrocarbons as gasoline (TPHg) and benzene were detected in groundwater from all the borings at concentrations ranging from 688 to 439,000 parts per billion (ppb) and from 1 52 to 13,200 ppb, respectively The highest concentrations came from the sample collected at 47 feet below grade (fbg) from boring CPT-4, located adjacent to the existing USTs Complete investigation results may be found in Cambria's July 20, 2000 Site Investigation Report 2002 Subsurface Investigation During June 2002, Cambria advanced seven CPT borings . (CPT-5 through CPT-11) Soil samples were collected from CPT-5 only, and they provide vertical definition of TPHg, benzene, and methyl tertiary-butyl ether (MTBE) near the existing USTs Depth-discrete groundwater samples were collected from all borings Groundwater 2