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I. METHODOLOGY 

1. Drilling MethodologyDrilling methods that advance the casing as drilling proceeds are veryefective methods to minimize the efects o drilling-uid invasion o theborehole wall. Casing-advance drilling methods include, or can be used with,cable-tool drilling, hollow-stem auger drilling, reversecirculation drilling usingdual- or triple-wall drill pipe, uid- and air-rotary drilling, rotosonic drillingmethods, and driven wells. I the tendency o this method is to overream thehole, contamination may move along the casing during drilling.

Drilling methods that do not use a drilling uid are preerable because theypreclude possible auier contamination rom such uids. !owever, in thisdrilling campaign, we will use water based drilling uid. "uch drilling methodsthat preclude the use o drilling uids include hollowand solidstem augerdrilling, hand auger drilling #only an efective shallow-drilling method whenused to drill above the water table$, buc%et auger drilling, resonant sonic-drilling method, and cable-percussion drilling methods. &ethods thatnormally reuire the use o a drilling uid or drilling include 'et-wash and 'et-percussion drilling, reverse-circulation drilling, and uid- and airrotary drilling.In cases where drilling-uid loss occurs during drilling, estimates o theamounts o uid loss and depth#s$ o these occurrences in the boreholeshould be documented. Drillinguid loss data may be useul in planning well-development techniues to be used upon completion o the borehole.(nother important actor to be considered when evaluating this data is well-screen placement.

(uger-drilling methods include using hollow-stem continuous-ight augers,solid-stem continuous-ights augers, buc%et augers, and hand-augers. (ll

auger-drilling methods are limited usually to drilling in unconsolidated soils orweathered roc%. (uger-drilling methods normally do not reuire the use o adrilling uid during the drilling process) however, in cases where water-bearing sands or silts are drilled, the addition o water or drilling mud to thehollowauger column may be necessary to inhibit the* blow in+ o these uid-li%e materials into the augers. he borehole is advanced by pushing the initialauger-column assembly below groundsurace and initiating a low-velocityrotation to the auger ights or buc%et-auger assembly. he lead auger sectionis euipped with a removable cutting head. he buc%et auger, on the otherhand, has hard-suracing material around the bottom cutting edge o thebuc%et. (s drillingprogresses, auger ights or %elly rods, in the case o abuc%et auger, are added to the drill stem until the desired depth is reached.

 he continuous auger ights carry drill cuttings to the surace.

Direct-otary Drilling with ater-/ased Drilling 0luid1Direct-rotary drillingand sampling, using various type soil2roc% sampling core barrels and devices,can be done in most soils and roc%s.

Direct-rotary drilling with water-based drilling uid is accomplished byinitiating rotation and applying a3ial pressure on the drill string and bit whilesimultaneously initiating and maintaining circulation o a drilling uid. he

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drilling uid is circulated down through the drill string and the cuttings-ladenreturn comes bac% up the annulus ormed between the drill string and theborehole wall. Cuttings rom the drilling operation are carried to groundsurace by the circulating drilling uid. (t the ground surace, the cuttings-laden drilling uid is discharged into a pit or series o pits where the drillcuttings settle out o the drilling uid.

(ter the cuttings have settled to the bottom o the circulation pit#s$, thedrilling uid is then recirculated as drilling progresses. Core samples o overburden soil materials can be obtained. oc% coring is accomplished bydrilling the borehole through the overburden, setting the casing through theoverburden into the roc%, and then coring the roc% through the casing.