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ne moldenhauer L.ALEX MOLDENHAUER,L.S.,P.E. engineering PRINCIPAL company 337.871 � a SEP 2 7 1OM9 September 24, 1990 LENVIRONMENTAL HEALTH PERMIT/SERVICES Ray Borges San Joaquin County Public Health Services P.O. Box 2009 Stockton, CA 95201 Subject: DESIGN ALTERATION ON SAN JOAQUIN COUNTY DRILLING PERMIT APPLICATION FOR SOUTHWEST HIDE COMPANY'S 250 FOOT DEEP MONITORING WELL #20. Dear Ray: As per your conversation with Kurt Balasek on September 20, Moldenhauer Engineering is submitting a design alteration for the Southwest Hide Company 250 foot monitoring well #20. The design on the drilling permit application indicates a single bore hole with three separate casings within the same hole. Because of Regional Board staff's concerns of vertical contamination between the individual casings, the new well design will consist of a single 4 or 6 inch diameter casing within the bore hole. During construction of the proposed well a 140 foot conductor casing will be installed to prevent surface cross contamination. The well will be screened from 250 to 240 feet below surface grade and will have a sand pack from the bottom of the well to 237 feet. Above the gravel pack will be a 2 foot thick bentonite plug followed by neat cement grout to the surface. The use of geophysics has been proposed to aid in the construction of this deep monitoring well . If geophysics is brought in. it will be used to determine the existance of contamination at depth. If contamination is found to exist at 250 feet below surface grade, the drilling may continue down until no contamination is found. As a result of the possiblity of contamination at 250 feet, the proposed well design may be extended below the 250 foot depth to avoid constructing a completely new well . t ✓ JCS _ � �e� 1107 KENNEDY PLACE, SUITE 7, DAVIS, CA 95616 • (91 6) 756-2250 E N G I N E E R I N G C O N S U L T A N T S P R O J E C T PLANNERS