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METHODOLOGIES AND PROCEDURES <br />I. Calibration of MiniRAE Lite Model 7300 PID <br />Prior to each field usage, the MiniRAE Lite photoionization detector (PID) will be calibrated in the field using <br />a 100-ppm isobutylene standard in accordance with the instructions outlined in the MiniRAE Lite User’s <br />Manual. The results will be recorded on the calibration log located in the PID carrying case along with the <br />date, time, and project information. An additional calibration verification check will be conducted by <br />attaching the calibration gas to the instrument and then removing to make sure the instrument reading <br />returns to zero. <br />II. Soil Sample Collection, Screening, and Analysis <br />Soil samples will be classified in the field consistent with the Unified Soil Classification System (USCS). <br />Field notes will be maintained describing the sample collection location, soil composition, field methods, <br />and environmental monitoring data such as visual and olfactory observations and photoionization detector <br />(PID) results. <br />Soil samples collected during sampling activities will be screened for the presence of organic vapors using <br />a PID equipped with a 10.6 or 11.7 electron volt (eV) lamp depending on the type of contaminants expected. <br />The PID will be calibrated prior to daily field activities. For each sample, a clean polyethylene freezer bag <br />will be half filled with soil and immediately sealed. Any clumps of soil present in the bag will be manually <br />broken up. The bag will be shaken for approximately 15 seconds and then stored for a minimum of 10 <br />minutes for headspace development. The bag will then be shaken for another 15 seconds and the PID <br />probe inserted through a small opening in the bag avoiding water droplets and soil particles. The highest <br />PID reading within approximately 2 seconds after insertion will be recorded for each sample. A new pair of <br />disposable nitrile gloves will be used during the collection of each sample to reduce cross contamination. <br />Soil sampling tools will be decontaminated with Alconox detergent (or similar) and rinsed with distilled water <br />prior to each sample collection. <br />Soil samples selected for laboratory analysis will be placed in laboratory‐prepared containers, labeled, <br />stored on ice, and shipped with the chain of custody form to a Minnesota‐certified laboratory. The respective <br />sample containers will be labeled with the following information: <br />Unique sample number <br />Site name <br />Name of sampler <br />Time and date <br />Desired analysis <br />III. Water Level Measurement <br />Water level measurements will be collected from the temporary wells using a battery powered tape-guided <br />water level meter. The water level meter will be inspected and cleaned using an Alconox solution and <br />rinsed with distilled water prior to each measurement to reduce the risk of cross contamination. If the probe <br />encounters free product or highly contaminated groundwater, the probe decontamination process will <br />include using a desorbing agent (dilute solution of water and isopropanol or methanol) followed by a <br />thorough tap water rinse and a final distilled or deionized water rinse. Each boring will be allowed to rest <br />for at least 5 minutes prior to measuring (this allows the well to adjust to the isostatic pressure). The <br />distance from the ground surface elevation to the well water surface will be measured and recorded to the <br />nearest 0.01 foot. The measurement results will be recorded on boring logs along with any other general <br />well observations.