Laserfiche WebLink
Clayton Group Services Page 3 <br />Standard Operating Procedures <br />SPO -5 - Monitoring Well Installation <br />Registered Geotechnical Engineer (GE), or Professional Civil Engineer (PE). They <br />also may require that boring logs be signed by an RG, CEG, or PE. <br />13. Soil Sampling - Unless indicated otherwise in the Work Plan, soil samples generally <br />are taken at the following depths: <br />• At 5 -foot intervals. <br />At each change in lithology or change in observed contamination. <br />From low permeability or high moisture content units if the units are thicker than <br />5 feet. <br />Soil sampling procedures are described in SOP -1, Split -Barrel Sampling of Soils. <br />14. During drilling, one of the most important responsibilities of the on-site geologist is <br />to assure that aquitards beneath contaminated aquifers are not fully penetrated by <br />drilling thereby permitting the downward migration of contamination. <br />15. Commonly, drilling will terminate at a depth that will permit screened casing 20 feet <br />below the water table. However, for dense non -aqueous phase liquids such as <br />chlorinated solvents where a free -phase is present, it may be necessary to screen the <br />lower portion of the aquifer. If the aquifer is thick enough and for hydrocarbon <br />contamination, typically commercially slotted screens are placed a minimum of 20 <br />feet below and 10 feet above the water table. <br />16. Upon completion of the boring, confirm borehole depth by measuring with engineers <br />tape inserted through the augers. <br />17. If the bottom of the borehole is deeper than the bottom of the proposed depth of the <br />screen and casing by more than 2 feet, bentonite chips should be added to fill the <br />borehole to about 1 foot below the bottom of the proposed screen depth. <br />18. The driller will set casing consisting of a sediment plug at the bottom, slotted casing <br />(well screen) in the interval as indicated above, and blank casing to the surface. <br />Threaded joints between casing sections should be used and not glued or solvent <br />welded joints as these may alter the chemistry of groundwater samples. Care must be <br />taken so that the casing is not resting against the sides or bottom of the hole prior to <br />setting in place. <br />19. The well screen should be new, machine -slotted or continuous wrapped wire -wound, <br />and generally made of PVC or stainless steel. <br />20. It may be necessary to install centralizers at the bottom and top of each screen <br />interval to insure proper placement of the screen. <br />S_yEnn-\ProiASPOs\SOP-5.doc <br />