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SECOR INTERNATIONAL INCORPORATED STANDARD PROCEDURE FOR GROUNDWATER MONITORING WELL CONSTRUCTION HOLLOW STEM AUGER METHOD Groundwater monitoring wells are constructed by Inserting or tremming well materials through the annulus of the hollow stem auger In general, the groundwater monitoring wells are constructed with 15 feet of screen below groundwater and 10 feet above groundwater, for a total screen length of 25 feet Where shallow groundwater 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 are 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 PVC casing with 0 01 to 0 02 machine 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 Lonestar 2112 or No 3 sand, or equivalent, for the 0 01 and 0 02 Inch slots, respectively Once the borehole has been drilled to the desired depth, approximately six Inches of filter sand are tremmied to the bottom of the boring The well screen and blank well casing are then Inserted through the annulus of the hollow stem augers The well screen Is sandpacked by tremmmg the appropriate filter sand through the annulus between the casing and augers while slowly retracting the augers During this operation, the depth of the sand pack In the auger Is continuously sounded to make sure that the sand remains in the auger annulus during auger retraction to avoid shortcircuiting the well The sand pack is tremmied to approximately one to two feet above the screen, at which time pre- development surging is performed to consolidate the sand pack Following construction of the sand pack, a two foot thick bentonite seal Is tremmied over the sand and hydrated In place The remainder of the borehole Is backfilled with bentonite grout, pellets, or chips The well head Is 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 damage with traffic 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, each well Is developed by surging the length of the screen interval and removing at least ten casing volumes of water Development of each well Is determined to be sufficient once pH, conductivity and temperature stabilize to within the 10 percent of the previous two readings Wastewater collected during development Is contained in 55-gallon DOT approved drums and stored on site pending laboratory results and disposal A label Is affixed to the drums Indicating the contents of the drum, suspected contaminants, date of generation and the monitoring well number from which the waste water was generated IConocoPhillipslRetad Sites1111931Reports111193 Off-Site Well Install 1-05 doc