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After setting the casing,sand or gravel filter material is use in the next well,and is analyzed along with the other
<br /> poured into the annular space to fill from boring bottom to samples. The field blank analysis demonstrates the
<br /> generally 1 foot above the perforated interval. A one to two effectiveness of the in-field cleaning procedures to prevent
<br /> foot-thick bentonite plug is set above this filter material to cross-contamination.
<br /> prevent grout from infiltrating the filter pack. Either neat
<br /> cement,containing about five percent bentonite,or sand- To minimize the potential for cross-contamination between
<br /> cement grout is then tremmied into the annular space from wells,all well development and water sampling equipment
<br /> the top of the bentonite plug to near surface. A traffic-rated not dedicated to a well is either steam cleaned or properly
<br /> vault is installed around each wellhead for wells located in washed between uses. As a secondary precautionary
<br /> parking lots or driveways,while steel"stovepipes"are measure,wells are sampled in order of least to highest
<br /> usually set over wellheads in landscaped areas. concentrations as established by available previous
<br /> analytical data.
<br /> After installation,the wells are thoroughly developed to
<br /> remove residual drilling materials from the wellbore,and to In the event the water samples cannot be submitted to the
<br /> improve well performance by removing fine material from the analytical laboratory on the same day they are collected
<br /> filter pack that may pass into the well. Well development (e.g.,due to weekends or holidays),the samples are
<br /> techniques used may include pumping,surging,bailing, temporarily stored until the first opportunity for submittal
<br /> swabbing,jetting,flushing,and air-lifting. All development either on water ice in a cooler,such as when in the field,or
<br /> water is collected either in drums or tanks for temporary in refrigerator at Apex's office.
<br /> storage,and properly disposed of pending laboratory
<br /> analytical results. To minimize the potential for cross-
<br /> contamination between wells,all development equipment is SOP-9
<br /> either steam cleaned or properly washed prior to use. MEASURING LIQUID LEVELS USING WATER LEVEL
<br /> Following development,the well is allowed to stand METER OR INTERFACE PROBE
<br /> undisturbed for a minimum of 24 hours before its first
<br /> sampling. Field equipment used for liquid-level gauging typically
<br /> includes the measuring instrument(water-level meter or
<br /> interface probe)and product bailer(s). The field kit also
<br /> SOP-8 includes cleaning supplies(buckets,solution,spray bottles,
<br /> GROUNDWATER PURGING AND SAMPLING and deionized water)to be used in cleaning the equipment
<br /> between wells.
<br /> Prior to water sampling,each well is purged by evacuating a
<br /> minimum of three wetted well-casing volumes of Prior to measurement,the instrument tip is lowered into the
<br /> groundwater. When required,purging will continue until well until it touches bottom. Using the previously established
<br /> either the discharge water temperature,conductivity,or pH top-of-casing or top-of-box(i.e.,wellhead vault)point,the
<br /> stabilize,a maximum of ten wetted-casing volumes of probe cord(or halyard)is marked and a measuring tape
<br /> groundwater have been recovered,or the well is bailed dry. (graduated in hundredths of a foot)is used to determine the
<br /> When practical,the groundwater sample should be collected distance between the probe end and the marking on the
<br /> when the water level in the well recovers to at least 80 cord. This measurement is then recorded on the liquid-level
<br /> percent of its static level. data sheet as the"Measured Total Depth"of the well.
<br /> The sampling equipment consists of either a"Teflon"bailer, When necessary in using the interface probe to measure
<br /> PVC bailer,or stainless steel bladder pump with a'Teflon" liquid levels,the probe is first electrically grounded to either
<br /> bladder. If the sampling system is dedicated to the well, the metal stove pipe or another metal object nearby. When
<br /> then the bailer is usually"Teflon,"but the bladder pump is no ground is available,reproducible measurements can be
<br /> PVC with a polypropylene bladder. In general and obtained by Gipping the ground lead to the handle of the
<br /> depending on the intended laboratory analysis,40-milliliter interface probe case.
<br /> glass,volatile organic analysis(VOA)vials,with"Teflon"
<br /> septa,are used as sample containers. The probe tip is then lowered into the well and submerged in
<br /> the groundwater. An oscillating(beeping)tone indicates the
<br /> The groundwater sample is decanted into each VOA vial in probe is in water. The probe is slowly raised until either the
<br /> such a manner that there is no meniscus at the top of the oscillating tone ceases or becomes a steady tone. In either
<br /> vial. A cap is quickly secured to the top of the vial. The vial case,this is the depth-to-water(DTW)indication and the
<br /> is then inverted and gently tapped to see If air bubbles are DTW measurement is made accordingly. The steady tone
<br /> present. If none are present,the vial is labeled and indicates floating liquid hydrocarbons(FLH). In this case,
<br /> refrigerated for delivery,under strict chain-of-custody,to the the probe is slowly raised until the steady tone ceases. This
<br /> analytical laboratory. Label information should include a is the depth-to-product(DTP)indication and the DTP
<br /> unique sample identification number,job identification measurement is made accordingly.
<br /> number,date,time,type of analysis requested,and the
<br /> sampler's name. The process of lowering and raising the probe must be
<br /> repeated several times to ensure accurate measurements.
<br /> For quality control purposes,a duplicate water sample is The DTW and DTP measurements are recorded on the
<br /> collected from each well. This sample may also be analyzed liquid-level data sheet. When FLH are indicated by the
<br /> or put on hold at the laboratory. When required,a trip blank, probe's response,a product bailer is lowered partially
<br /> prepared at the laboratory,is placed in the transport cooler. through the FLH-water interface to confirm the FLH on the
<br /> It is labeled similar to the well samples,remains in the cooler water surface and as further indication of the FLH thickness,
<br /> during transport,and is analyzed by the laboratory along particularly in cases where the FLH layer is quite thin. This
<br /> with the groundwater samples. In addition,a field blank may measurement is recorded on the data sheet as"FLH
<br /> be prepared in the field when sampling equipment is not thickness."
<br /> dedicated. The field blank is prepared after a pump or bailer
<br /> has been either steam cleaned or properly washed,prior to
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