ARCHIVED REPORTS XR0008680 - Laserfiche WebLink

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£ gin a 4 S [EC ® IR r, • is encountered or perched water dictates otherwise, the screen is adjusted as appropriate, to maintain a proper seal at the surface (minimum three feet) and to avoid penetrating low permeable horizons or aquicludes All groundwater wells were installed in accordance with the conditions of the well construction permit issued by the regulatory agency exercising jurisdiction over the project site The well screen generally consists of schedule 40 polyvinyl chloride (PVC) casing with 0 01 to 0 02 factory slots As a general rule, 0 01 inch slots are used in fine-grained silts and clays and 0 02 inch slots are used in coarse-grained materials The screen is then filter packed with #2116 or#3 sand, or equivalent, for the 0 01 and 0 02 inch slots, respectively y Once the borehole was drilled to the desired depth, approximately six inches of filter sand was tremmied to the bottom of the boring The well screen and blank well casing were then ' inserted through the annulus of the drive casing The well screen was sandpacked by tremming the appropriate filter sand through the annulus between the well casing and drive a° casing while slowly retracting the outer casing During this operation, the depth of the sand pack in the auger was continuously sounded to make sure that the sand remains in the outer casing annulus during auger retraction to avoid shortarcuiting the well The sand pack was tremmied to approximately two feet above the screen, at which time pre-development surging was performed to consolidate the sand pack Additional sand was added as necessary to assure that the sand pack extends a minimum of two feet above top of screen Following construction of the sand pack, a two foot thick bentonite seal was tremmied over �� ' the sand and hydrated in place The remainder of the borehole was backfilled with bentonite grout The well head was then capped with a locking cap and secured with a lock to protect the well from surface water intrusion and vandalism ' ' The well head is further protected from traffic damage with a rated well box in paved areas or locking steel riser in undeveloped areas The protective boxes or risers are set in concrete The details of well construction are recorded on well construction logs ' Following well construction, the wells were developed in accordance with agency protocols by intermittently surging and bailing the wells Development is determined to be sufficient once pH, conductivity and temperature stabilize to within the 10 percent of the previous two ' readings and turbidity is below 10 nephelometric turbidity units (NTUs) Groundwater Sampling The sampling procedure for each well includes measuring the water level and checking for the presence of separate-phase hydrocarbons (SPH), using either an electronic indicator and a clear Teflon® bailer or an oil-water interface probe Wells not containing SPH are purged of approximately three casing volumes of water (or to dryness) using a submersible pump, centrifugal pump, gas displacement pump, or bailer The equipment and purging method used for the current sampling event will be noted on field data sheets During purging, ' temperature, pH, and electrical conductivity will be monitored in order to document that these parameters are stable prior to collecting samples After purging, water levels are allowed to partially recover Groundwater samples will then be collected following purging using a disposable Teflon® bailer, placed into appropriate EPA-approved containers, labeled, logged ' onto chain-of-custody documents, and transported on ice to a California state-certified laboratory Sampling equipment will be thoroughly cleaned prior to and following the collection of each sample 1 Laboratory Procedures Selected soil samples were analyzed for the presence of TPHg, BTEX, fuel oxygenates ' (MtBE, TAME, DIPS, EtBE, TBA, ethanol), and lead scavengers (1,2-DCA and EDB) using