ARCHIVED REPORTS XR0010010 - Laserfiche WebLink

Home Browse Search

Ms Vicky McCartney Page 2 of 6 establishments The elevation of the ground surface at the site is approximately 50 feet above mean sea level (MSL), and slopes gently downward to the north The nearest natural drainage feature is Sugar Cut, located approximately 2'/4 miles north-northeast of the property Tom Paine Slough is located approximately 23/4 miles northeast of the property Shallow groundwater beneath the site has been encountered at depths between 10 5 and 12 5 feet below ground surface (bgs) 2.2 Inveshgahons Undertaken Four previously undiscovered USTs were encountered during earthmoving activities at the subject site The location of the USTs are shown on Figure 2 The USTs were removed under permit from EHD between June 2001 and September 2001 Soil samples collected beneath the USTs contained low levels of gasoline and diesel/kerosene constituents Groundwater samples collected from the bottom of the tank excavation(s) also contained elevated levels of gasoline and diesel/kerosene constituents Three shallow groundwater monitoring wells were installed at the site in November 2001 Relatively low levels of petroleum hydrocarbon constituents were detected in the soil and groundwater Groundwater analytical results indicate that petroleum hydrocarbon contamination is present in groundwater at relatively low levels Groundwater quality has been monitored on a quarterly basis since well installation No contaminants exceeding drinking water Maximum Contaminant Levels (MCLS) have been detected in any site well since September 2002, which suggests that groundwater has not been significantly impacted beneath the site A request for site closure was submitted to EHD on August 13, 2003 3 0 INVESTIGATIVE PROCEDURES On March 16, 2004, Sean Garvey of Ground Zero arrived at the site to supervise drilling and sampling activities Ms Vicky McCartney of San Joaquin County Environmental Health Department (EHD) conducted the site inspection and observed field activities Vironex advanced borings SBI/SBla and SB2 (Figure 3) under the supervision of field geologist Sean Garvey, and project manager John Lane, a California Registered Geologist, to further explore the lateral extent of soil and groundwater contamination Boring SB 1 located approximately 20 feet southeast of well MW3 was advanced to a depth of approximately 26 feet below ground surface (bgs) Boring SB l a was advanced immediately adjacent to boring SBI for the sole purpose of collecting a discrete groundwater sample at a depth of approximately 21-24 feet bgs Boring SB2 located approximately 70 feet north of well MW3 (approximately 45 feet north of MW 1) was advanced to a depth of approximately 25 feet bgs Vironex utilized both a truck-mounted and a Bobcat® tractor-mounted Geoprobe 5400 direct push rig to advance the borings and collect soil and groundwater samples Soil samples were collected continuously from the hollow stem auger and direct push borings using a 4-foot long core sampler lined with inert plastic sleeves, which afforded soil identification and subjective evaluation of contamination A photo ionization detector (PTD) was used to monitor the presence of volatile organic compounds (VOCs) in the soil Soil samples selected for G 1GROUNDZE\Souza\Reports\ADD_SUBSURF_SUM doc