Laserfiche WebLink
San Joaquin County Public Health Services <br /> Environmental Health Division <br /> November 1, 1994 <br /> Page 6 <br /> 2 2 Monitoring W lI Construction <br /> A monitoring well will be installed in the soil boring Monitoring well specifications and <br /> well development are discussed below Based on an anticipated depth to water of 65 feet the well <br /> will be screened from 60 to 75 feet <br /> Well Installation <br /> The groundwater monitoring wells will be installed through the hollow-stem of the augers <br /> The monitoring well will be constructed of four-inch diameter flush-threaded Schedule 40 PVC <br /> casing and fifteen feet of horizontally machine-slotted well screen The well will be assembled <br /> without the use of chemical bonding <br /> The screened interval will be filtered packed with a prewashed filter sand from total depth <br /> to approximately two feet above the top of the screened interval Both the screen size and filter pack <br /> used will be chosen based upon laboratory sieve analysis or on-site sieve inspection of the materials <br /> found at the interval to be screened Two well screen and filter sand sizes will be on hand to prevent <br /> delays caused by not having the proper sizes available If sieve analysis indicate that more than 50 <br /> percent of the finest soil in the screened interval is finer than 0 020 inches (0 75 millimeters) then <br /> a 0 01-inch slot screen with a #2 sand will be used If less than 50 percent of the soil is finer than <br /> 0 02 inches then a 0 02-inch slot screen and a #3 sand will be used Following placement of the <br /> sand filter, the well will be bailed or surged to set the sand filter <br /> A two-foot thick bentonite seal will be placed above the filter pack using bentonite pellets <br /> An appropriate quantity of distilled water will be added to the bentonite after it is in place to produce <br /> an effective seal before backfilling The filter pack and bentonite will be placed by using the auger <br /> as a tremmie pipe <br /> After removing all auger equipment from the borehole, the remaining annular space will be <br /> backfilled with a three percent prehydrated bentonite/cement grout mixture The mixture will be <br /> SACI28 18 Page-6 DAMES & MooRE <br />