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r N Northern CaiifoTnia Office 5075 Commercial' Circle Suite A Concord ; CA 94520 ( 9 2 5 ) 363 - 7322 Fax ( 925 ) 363 - 7275 terminated at ten (10) feet below grade, unless further penetration is refused, or groundwater is encountered, whichever occurs first. In either of the latter cases, the boring and/or probe push will be terminated and a sample of the soil will be collected for laboratory analysis. Prior to commencing work, all drilling and/or probe equipment will be decontaminated by steam cleaning and pressure washing. (Cleaning with Alconox with a distilled water rinse is acceptable.) Auger and other sampling equipment will be decontaminated between Borings and between probe pushes. Undisturbed soil samples will be collected throughout the entire depth at 5'intervals, using split-spoon drive samplers or Shelby tubes, and of all probe pushes inside of the hollow push rods. All samples will be field screened for the presence of hydrocarbons using a portable hydrocarbon vapor analyzer(PID or equivalent). Field screening values shall be recorded on the boring logs. A total of(3) soil and (3) water samples (if encountered) will be collected from each site for laboratory analysis. One sample from the UST area exhibiting the highest PID or equivalent, one sample from the dispenser area exhibiting the highest PID or equivalent, and one more sample based on consultant's expertise. If groundwater is not detected during the initial investigation onsite, a minimum of two borings may be completed to a depth where groundwater is encountered, or to a maximum depth of 50 feet from the surface. The basis will be one of two criteria: A) GW is anticipated to be found between 25' to 50' B) Based on Soil and site conditions, consultant believes UST release plume would not be detected at 25'. If groundwater is not encountered within 50 feet of the surface, the boring will be terminated, and 2 soil samples from each boring, chosen by the Consultant, will be submitted for laboratory analysis. From any boring in which groundwater is still not encountered, 2 soil samples from each boring, chosen by the Consultant, will be submitted for laboratory analysis. (Subject to soil sample criterion) If groundwater is encountered, the following shall be conducted: In a Probe Assessment, a "pull back" sampling screen toot shall be used in the probe or a temporary well shall be installed. A groundwater sample shall be collected by purging the screen or well and following standard industry protocol for groundwater sampling. A temporary piezometer sealed to prevent surface intrusion may be used in lieu of a temporary well. Soil at the groundwater interface should be field screened to determine I whether or not soil at the interface should be collected for laboratory analysis. I