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i <br /> acid as a preservative Our geologist checks to see if headspace is present If headspace is present, we <br /> collect more samples until none is present Chain of Custody Records are initiated in the field by the <br /> geologist, updated throughout handling of the samples, and sent along with the samples to the <br /> laboratory Copies of Chain of Custody Records are included in our report <br /> ! Gradient Evaluation. <br /> ! ERI evaluates the direction of flow and gradient at the site The elevation of the top of each well <br /> casing is measured relative to mean sea level by a Iicensed land surveyor Water-depth measurements <br /> are made from the top of the casing in the well to the nearest 0 01 foot with an electronic water-level <br /> indicator The well is vented to atmosphere for a minimum of 0 5 to 1 hour before obtaining depth-to- <br /> water measurements Ventmg is conducted to allow the groundwater to equilibrate with barometric <br /> pressure These data are combined to evaluate the relative elevation of the groundwater surface in each <br /> ! well and the slope of the groundwater surface across the site <br /> Quality Assurance/Quality Control <br /> ! The sampling and analysts procedures employed by ERI for groundwater monitoring and sampling <br /> follow regulatory guidance documents for quality assurance/quality control (QA/QC) Quality control <br /> is maintained by site-specific field protocols and quality control checks performed by the laboratory <br /> Laboratory and field handling of samples may be monitored by including QC samples for analysis QC <br /> samples may include any combination of the following The number and types of QC samples are <br /> selected and analyzed on a project-specific basis <br /> Trip Blanks - Trip blanks are sent to the project site, and travel with samples collected from the project <br /> site to the laboratory They are not opened, and are returned from the project site with the samples for <br /> ' analysis <br /> Field Blank - Prepared in the field using organic-free water Field blanks accompany samples collected <br /> at the project site to the laboratory and are analyzed periodically for specific chemical compounds <br /> present at the project site where they were prepared <br /> Duplicates - Duplicate samples are collected from a selected well and project site They are analyzed <br /> at two different laboratories, or at the same laboratory under different labels <br /> Equipment Blank - Periodic QC samples are collected from field equipment rmsate to verify adequate <br /> cleaning procedures <br /> ! <br /> i <br /> 1 <br />