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i gradient of approximately 0 0026 feet per foot in a northwest direction Details of the groundwater gradient review are provided in Kleinfelder's letter to SJCPHS, dated January 8, 1993 Based on the groundwater gradient review, Kleinfelder proposed the installation of a single monitoring well northwest of the previous tank excavation to assess groundwater. FIELD ACTIVITIES Prior to conducting field activities at the site, Kleinfelder prepared a work plan dated October 29, 1992 for County approval The work plan included a map of the proposed well location, a drilling permit application, a health and safety plan, a description of Kleinfelder's drilling and well installation protocol, and the proposed well construction details. Kleinfelder also prepared a work plan addendum dated January 8, 1993, which summarized the results of the groundwater gradient review and Kleinfelder's recommendation to install a single monitoring well Drilling and Well Installation On February 3, 1993, Klemfelder installed one monitoring well northwest of the former tank excavation as shown on Plate 1 The well was installed in a boring drilled using a truck- mounted dnll ng, equipped with 8-inch hollow stem augers While drilling, soil samples were collected approximately every 5 feet for field screening and logging An experienced environmental geologist classified the soil, logged the stratigraphy of the boring, and collected soil samples for potential laboratory analysis if organic vapors were detected. Drilling and sampling details are provided in Attachment A, Section A-2 Upon completing the boring, a 2-inch PVC well was constructed in the boring The well was screened approximately 5 feet above and 15 feet below where groundwater stabilized (at a depth of approximately 19 feet) and consisted of 0 02-inch factory-cut slots The filter pack consisted of clean Lone Star Industries #2112 Monterey sand Well installation details are described in Attachment A, Section A-3. Soil encountered in the boring consisted of brown sand with some silt from the ground surface to an approximate depth of 15 5 feet Silt with some sand was present below this depth to a depth of 24 feet. First encountered groundwater was encountered approximately 25 feet below the ground surface in a 1.5-foot thick sand layer Silty sand was present below the sand layer to the termination of the boring Soil above first encountered groundwater was generally moist Groundwater eventually stabilized approximately 19 feet below the ground surface Well Development and Groundwater Sampling On February 9, 1993, the well was developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the well. The well was first sampled with a clean disposable bailer to visually inspect for hydrocarbon layer or sheen No product layer or sheen was observed on the water. The well was then developed by hand baling. Surging along the screened interval of the well was performed to draw the sediment from the formation into the filter pack and the well, and to set the sand pack Development continued until approximately 20 well volumes were purged. FR1O-26(1993) Page 2 of 4 24-220172-AOO Copyright 1993 Klemfelder, Inc KLEINFELDER 3077 Fite Circle, Sacramento, CA 95827 (916) 366-1701