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k" KLEl N FELDER July 21, 1993 Park Environmental Corporation 2140 Professional Drive, Suite 130 Roseville, California 95661 Attention: Mr. Dick Zipp Subject: Review of Excavation Conditions Calkins Trucking Site North Highway 99 Acarnpo, California Dear Mr. Zipp: This letter contains a review of excavation conditions observed at the Calkins Trucking Site along North Highway 99 in Acampo, California. The purpose of this review was to evaluate an existing excavation, review available subsurface information, and provide recommendations for additional excavations at the site. On June 30, 1993, a senior soils engineer from Kleinfelder visited the subject site to observe existing conditions. An excavation approximately 8 feet deep was observed. We understand this excavation was made in order to remove buried fuel stora&e tanks. The excavation sidewalls are in a near vertical orientation and have exhibited minor sloughing during the 2 year period since excavation. The soils exposed in the excavation sidewalls consist of weakly to moderately cemented silty sand and sandy clayey silt. Boring logs performed by others at the site indicate these conditions exist to depths of about 35 feet. Of potential concern is the impact of additional excavation (both lateral and vertical extent) near the existing office building located northeast of the excavation. Based on the conditions observed, the boring logs completed by others, and our understanding of the proposed excavation sequence, we recommend additional excavations not extend within a 1 horizontal to 1 vertical projection from the base of the existing foundations. During the excavation process, we recommend the office building should not be occupied. Further, all electrical power and gas lines should be abandoned during the excavation process. Neither construction equipment nor stockpiled soil should be located at the top of the excavated slopes (this includes the automobile parking area along the east side of the existing excavation). No personnel should enter the excavation without proper shoring and/or bracing. The recommendations contained in this letter are based on our field observations and borings completed by others. It is possible conditions may exist which would cause us to revise these recommendations. A representative from Kleinfelder should be present at the site when excavations occur adjacent to the office building to review actual conditions encountered. 23-4590-01/R2438 Page 1 of 2 July 21, 1993 Copyright 1993 Kleinfelder,Inc. KLEINFELDER 3077 Fite Circle, Sacramento, CA 95827 (916) 366-1701