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THE - III MARK _ rib GROUP _ - ENGINEERS & GEOLOGISTS, INC. - February 1, 1993 92-1177102.10= _FEg-:0 2 1993 ENVIRONMENTAL H San Joaquin PHS PERMIT/SERVICES L Environmental Health Services 445 N. San Joaquin Stockton, CA 95201- Attention: Ms. Diane Hinson, Unit IV Supervisor = Subject: Abandonment of Monitoring Wells. MW-1, MW-2 and .MW 3 at Stockton Scavenger Association, Stockton, CA Dear Ms. Hinson: As discussed with you on January 28, 1993 The MARK Group, Inc. (MARK)`is preparing for the abandonment of three existing -monitoring wells (see Drawing 1) at 1240 Navy Drive, Stockton, California. Two techniques will be used to formally abandon. these wells. :MW-1 and, MW-3 will be abandoned using_the methods described below:- ■ The monitoring _well shall be destroyed by removing all material within the- original borehole (including.the well casing; screen,7filter pack, and annular seal). ■ The created hole will be filled completely with the appropriate sealing material. Typically, neat cement with 5% bentonite is preferred. - In addition, well MW-2-is located within .the proposed excavation area. Since- the excavation activities are expected to destroy well-,MW-2, MARK proposes that the following procedures be.used in order to properly abandon MW-2: ■ Neat cement is mixed and pumped to a pressure grout system consisting of a slip -cap, tremie pipe, water release valve; and a pressure valve (see drillers schematic. Drawing 2): ■ Grout is pumped through the water,release valve until the well is filled. - This -enables the-grout.to be forced through the perforations of the well screen and permeate into the wells annulus. _ ■ The water valve is closed and grout is pumped for one'oto two more minutes. If you should have any questions regarding this letter, or_any other matters, pleased do- not o-not hesitate to call Robert S. Spare, or the undersigned.- 7 - Hookston Square, Suite 120 3480 Buskirk Avenue Pleasant Hill; CA 94523 • (510) 946-1055. • FAX (510) 946.9813