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• Above ground and underground tanks were not evaluated for this work plan. • Records of tests and repairs of fuel lines and tanks were not reviewed for this work plan. • The location of maintenance shops, chemicals used in the shops and method of chemical storage were not reviewed for this work plan with the exception of a review of historical practices for the disposal of chlorinated wash water. Prior to 1988, chlorinated wash water was disposed in an unlined former rinse water pond located in Figure 2 of the Revised Work Plan. That disposal practice was discontinued in 1988. The presumed source of chloroform in groundwater was removed when this disposal practice was discontinued. _ 5.1.2 Topographic Map of Site Vicinity • A topographic map is provided in Figure Al of this Addendum. • Topography in the vicinity of the site slopes to the north-northwest. • An expanded site map of the Triple E facility is provided in Figure A2 • Location of known storm water catchments are indicated on Figure A2. • Location of existing monitoring wells are indicated on Figure A2. • Location of above ground and underground storage tanks were not considered. • Location of the former rinse water pond is shown on Figure A2. • Location of the existing wash water treatment plant, and disposal spray field are shown on Figure A2. • Location of a major body of water, namely the water exposed in gravel mining excavations are shown as dark shaded areas within excavated areas (light shaded) on Figure Al. • Location of nearby municipal well #1803 is shown on Figure A2. • Location of other major physical and man-made features are shown on Figure A2. 5.1.3 Geology/Hydrogeology Groundwater occurs at approximately 65 feet bgs in an unconfined aquifer of alluvial material composed of sands, gravels, silts and clay. Chloroform has been detected in monitoring wells screened between 61-90 feet. No chloroform has been detected in well MWAB screened below 117 feet in the heart of the identified plume. The shape of the chloroform plume has been interpreted from well monitoring data as discussed in the Revised Work Plan and is shown on Figure A2. Also shown on Figure A2 is the variation in direction and magnitude of the groundwater gradient based on calculations from two different measurement times. An extraction well (XW-1) was proposed in a location near MW-6 as indicated on Figure 2 of the Revised Work Plan. The boring for the extraction well will be logged by a geologist under the direct supervision of a California Registered Geologist, who will record the depth (elevation) and a physical description of the soil types encountered during drilling. When first ground water is encountered, as indicated by the driller or the nature of returned cuttings, the supervising geologist will make a determination of the likelihood that water is under confined conditions based on the texture of the material immediately overlying the water-bearing zone. If confined conditions are suspected, the •. 2 t,J CONDOR