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Clayton Group Services <br />WELL DEVELOPMENT <br />The process of drilling and installing a groundwater monitoring well creates some <br />clogging, coating, and/or compaction of the borehole and subsurface formations with fine <br />material that may interfere with the measurements of the formation's hydraulic properties <br />and water quality analyses. Well development serves to remove this finer material (silt, <br />clay, fine sand and drilling fluid residue) from the well screen and filter pack and restore <br />the groundwater properties and hydraulic communication within the formation and <br />between the well and the formation. <br />Well development procedures should follow California Department of Water Resources <br />Bulletin 74-90 (Supplement to Bulletin 74-81) - California Well Standards and ASTM <br />standards, Designation D 5092-90 - Standard Practice for Design and Installation of <br />Ground Water Monitoring Wells in Aquifers. By reference, these standards are <br />incorporated into these Standard Operating Procedures. <br />Procedures <br />The well development procedure consists of the application of energy in the well to <br />create a groundwater flow reversal (surging) in and out of the well, filter pack, and <br />natural formation to draw fines into the well and to pump or otherwise draw drilling <br />fluids and fines out of the well, filter pack, and natural formation. <br />In general, the monitoring well should be developed as soon as possible after the well has <br />been installed and the annular seal materials have cured. The California Regional Water <br />Quality Control Board - Los Angeles Region (CRWQCB-LA) in their May 1996 <br />Guidebook (Interim Site Assessment & Cleanup Guidebook) recommends waiting no less <br />than 48 hours; However, this long a wait may not be practical when a driller, if contracted <br />to develop the well, is already on site. <br />Well development should be started slowly and gently and be increased in vigor as the <br />well is developed. The following well development methods are recognized by ASTM: <br />Mechanical Surgin - Using this method, water is forced to flow into and out of <br />the well by lifting and lowering a plunger (or surge block) or bailer up and down <br />