ARCHIVED REPORTS_XR0008804 - Laserfiche WebLink

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i . be obtained prior to beginning field work Three soil bonng/monitonng wells are proposed at the locations shown on Figure 2 All drilling equipment shall be thoroughly cleaned prior to drilling and ' between individual borings to prevent the introduction of contaminants from off site or between boring locations The soil borings shall be advanced with hollow-stem drilling equipment fitted with a bit with sufficient diameter to drill a boring in which a two-mch diameter monitoring well can be installed Borings shall be logged by a California Registered Geologist using the Unified Soil Classification System A log of each bonng, including soil and lithologic descriptions, depths of water bearing zones, petroleum contamination shall be kept during the drilling operation Soil samples shall be collected using industry-standard sampling and sample handling procedures Soil samples shall be collected at depths of four and eight feet bgs using a split-barrel sampler driven ahead of the bit The sampler tool shall be fitted with two-inch diameter, clean, brass sleeves to retain the sample for transport to the laboratory The brass sleeves shall be sealed with Teflon sheet and plastic end caps The well borings shall be advanced to 20 feet bgs or approximately 10 feet below the groundwater level The static groundwater level was measured at approximately nine feet bgs on 21 January 1999 The monitoring wells shall be constructed with two-inch solid PVC casing and 0 020-inch slotted casing (factory-milled well screen) The well screen shall be set from approximately five to 20 feet bgs The solid casing shall extend from to approximately 0 5 feet below ground surface to allow a flush surface completion A filter pack of #3 sand shall be placed around the well screen to approximately one foot above the screen A one foot filter seal of bentonite chips shall be placed on top of the filter pack The sanitary seal shall extend from the top of the filter seal to approximately one foot bgs The surface shall be completed with a traffic-rated vault box The monitoring wells shall be surveyed to obtain the relative elevations of the ground surface and top- of-casing(TOC), and the horizontal positions The depth to groundwater shall be measured from the TOC to determine the groundwater gradient The monitoring wells shall be developed until the water appears clear of sediment or until five well casing volumes have been extracted Water extracted from the monitoring wells shall be placed into appropriate containers and left on site for disposal by the property owner The groundwater in the well shall be allowed to stabilize for at least 24 hours after well development before commencing with sampling B Collection and Analysis of Groundwater Samples Prior to sampling, the static groundwater level shall be measured from the TOC for groundwater gradient determination As monitoring well purging proceeds, the extracted groundwater shall be evaluated for the field parameters pH, electrical conductivity, and temperature At least five well volumes shall be extracted in preparation for sampling WORK-PLAN FOR LIMITED SOIL AND GROUNDWATER INVESTIGATION SUNNYSIDE PRODUCE, THORNTON, CALIFORNIA PAGE 3