ARCHIVED REPORTS_XR0012330 - Laserfiche WebLink

Home Browse Search

i ERI 205503 ROI Unocal Service Station 5886 Stockton California lune 3 1997 either be treated on site or removed to an appropriate disposal facility Monitoring Well Construction Monitoring wells are constructed In borings using thread-pointed, 2-inch inner diameter, Schedule 40 polyvinyl chloride (PVC) casing No chemical cements, glues, or solvents are used in well construction The screened portion of each well consists of factory-perforated casing with 0 020-Inch wide slots If unconfined aquifer conditions exist, the well screen is Installed from the total depth of each well to approximately 10 feet above the uppermost water-bearing unit If confined conditions exist, the uppermost water-bearing unit is screened exclusively Unperforated casing is Installed from the top of each screen to the ground surface The annular space In the well is packed with number 3 sand to approximately 1 to 2 feet above the slotted Interval A bentonite plug is added above the sand pack to prevent cement from entering the well pack The remaining annulus is backfilled to grade with a slurry of portland cement The monitoring wells are protected with a traffic-rated, cast-aluminum utility box equipped with a PVC skirt The box has a watertight seal to protect against surface-water Infiltration and must be opened with a special wrench The design of this box discourages vandalism and reduces the possibility of accidental disturbance of the well Well Development ERI waits a minimum of 24 hours before development of the monitoring wells to allow the grout to seal Initially, a water sample is collected for subjective analysis before development of the monitoring wells This sample is collected from near the water surface in the well with a Teflon® bailer cleaned with a laboratory-grade detergent and delonized water The wells are developed with a surge block and pump Well development continues until the discharge water is clear of silt and sand Clay-size sediments derived from the screened portion of the formation cannot be eliminated by well development Product is bailed from the well and stored in appropriately labeled drums on site ERI apprises Tosco of appropriate disposal options for product bailed from the well ()uali!y Assurance/Quality Control The sampling and analysis procedures employed by ERI for groundwater monitoring and sampling follow regulatory guidance documents for quality assurance/quality control (QA/QC) Quality control is maintained by site-specific field protocols and quality control checks performed by the laboratory Laboratory and field handling of samples may be monitored by including QC samples for analysis QC samples may include any combination of the following The number and types of QC samples are selected and analyzed on a project-specific basis Duplicates - Duplicate samples are collected from a selected well and project site They are analyzed at two different laboratories, or at the same laboratory under different labels