SITE INFORMATION AND CORRESPONDENCE_1987-1992

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Lincoln Center Workplan -2- 15 October 1987 site.- The screened interval should bridge the water table during dry and wet seasons of the year, and should screen this permeable zone. Background information which should be considered in well design includes: a. A 13 June 1985 letter from Eugene Delucchi, Deputy Director of the San Joaquin County Public Works Department, to Robert Grimshaw of the Department of Health Services states, "A major separation of the casing was located at a depth of 42 feet from the surface, and it was evident that water was entering at this point. " This is in reference to Lincoln Village Well No. 1. The letter was in our files which have been copied by a representative for Leedshill- Herkenhoff. b. Water level in a monitoring well at the Chevron station at Benjamin Holt and Pacific Ave. was 47 feet below ground surface in January of 1987. Information from this investigation is attached. 5. The plan to log boreholes based on the determination of lithology made by a geologist during boring using the direct rotary drilling method without any sampling is unacceptable. Proper hydrogeologic characterization of the site will require sampling of the borings. This can be accomplished using a hollow stem auger and a continuous core sampler, or a split spoon sampler. It will also be difficult to determine location of the water table, and the interval to be screened using the proposed method. 6. I encourage Lincoln Properties Limited to cooperate with Chevron USA, Inc. They are involved in a ground water investigation at the corner of Benjamin Holt Drive and Pacific Avenue. Perhaps permission may be granted to use their existing monitoring well for determination of ground water gradient. The easternmost monitoring well proposed in this workplan may not have to be constructed at this time if access to the existing well at the Chevron site is secured. The contact for Chevron is Mr. Mike Manos, Chevron USA, Inc. , 2 Annabel Lane, Suite 200, San Ramon, CA 94583 . 7. Fluids used in the direct rotary drilling method should be free of additives which would cause downhole contamination, or interfere in the analysis for PCE and TCE. 8. Well development techniques which introduce air into the water- bearing formation should be avoided. Air entrainment may reduce the permeability of the formation, and create headspace at the, entrance to the well. Since the contaminants of concern are easily volatilized, samples taken from these wells may not represent the true quality of the ground water, especially in the period shortly following development. 10. Nearby domestic wells should be located in this phase of the investigation. Once gradient is established, those wells down-