Laserfiche WebLink
AEGIS ENVIRONMENTAL, INC. <br /> STANDARD OPERATING PROCEDURE <br /> �RE: HOLLOW-STEM AUGER MONITORING WELL INSTALLATION AND <br /> DEVELOPMENT <br /> SOP-6 <br /> Boreholes for monitoring wells are drilled using a truck-mounted, hollow-stem auger drill rig The <br /> borehole diameter will be a minimum of 4 inches larger than the outside diameter of the casing when <br /> installing well screen The hollow-stem auger provides minimal interruption of drilling while permitting <br /> soil sampling at desired intervals Soil samples are collected by either hammering or hydraulically <br /> pushing a conventional split-barrel sampler containing pre-cleaned 2-inch-diameter brass tubes A <br /> geologist or engineer from Aegis Environmental, Inc , continuously logs each borehole during drilling <br /> and constantly checks drill cuttings for indications of both the first recognizable occurrence of <br /> groundwater and volatile hydrocarbons using either a portable photoionization detector,flame ionization <br /> detector, or an explosimeter The sampler is rinsed between samples and either steam cleaned or <br /> washed with all other drilling equipment between borings to minimize the potential for cross- <br /> contamination <br /> Monitoring wells are cased with threaded, factory-perforated and blank Schedule 40 PVC The <br /> perforated interval consists of slotted casing, generally with 0 020-inch wide by 1 5-inch long slots, with <br /> 42 slots per foot A PVC cap may be secured to the bottom of the casing with stainless steel screws, <br /> no solvents or cements are used Centering devices may be fastened to the casing to ensure even <br /> distribution of filter material and grout within the borehole annulus The well casing is thoroughly <br /> Washed and/or steam cleaned, or may be purchased as pre-cleaned, prior to installation <br /> After setting the casing inside the hollow-stem auger, sand or gravel filter material is poured into the <br /> annular space to fill from boring bottom to generally 1 foot above the perforated interval A 1- to 2-foot <br /> thick bentonite plug is set above this filter material to prevent grout from infiltrating into the filter pack <br /> Either neat cement, containing about 5 percent bentonite, or sand-cement grout is then tremmied into <br /> the annular space from the top of the bentonite plug to near surface A traffic-rated vault is installed <br /> around each wellhead for wells located in parking lots or driveways, while steel "stovepipes" are usually <br /> set over wellheads in landscaped areas <br /> After installation, the wells are thoroughly developed to remove residual drilling materials from the <br /> wellbore, and to improve well performance by removing fine material from the filter pack that may pass <br /> into the well Well development techniques used may include pumping, surging, bailing, swabbing, <br /> betting, flushing, and air-lifting All development water is collected either in drums or tanks for temporary <br /> storage, and properly disposed of depending on laboratory analytical results To minimize the potential <br /> for cross-contamination between wells, all development equipment are either steam cleaned or properly <br /> washed prior to use <br /> 0 <br /> ATTACHMENT1SCP-wsurfEMBER 1992 <br />