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Pombo Ranch Facility August 17,2004 Subsurface Investigation Report& Second Quarter Groundwater Monitoring A licensed surveyor in preparation for electronic submission of the laboratory data P rY surveyed all of the wells currently sampled on a quarterly basis for elevation, latitude and longitude. Groundwater Elevations 05/14/04 ' Well Collar Elevation DTW GW Elevation MW-1 53.47 10.6 42.87 MW-2 53.22 10.59 42.63 ' MW-3 55.02 11.29 43.73 MW-4 53.55 10.7 42.85 MW-5 53.46 10.8 42.66 ' MW-105 53.55 10.89 42.66 Well records for all wells within a 2000-foot radius of the site were requested from the Department of Water Resources. Water Resources reported records'of several wells in the northwest quarter of section 30 Township 2South/ Range 5 east but no wells records for wells within 2000 feet of the site. There were no well completion ' reports on file for the three domestic wells identified in an earlier receptor survey and shown on Figure 1. Construction details have not been recovered for the nearby ' wells and the well is reported to not been serviced for many years. 2.1 Drilling Permits were obtained as necessary for all wells (including borings) before ' drilling began. The soil boring was accomplished using a mobile mounted drilling rig employing the use of a hollow stem flight auger no less than 3 1/4- inch i.d. and 8 7/8 o.d. Geoprobe® Systems was used for a preliminary phase of sampling. All drilling equipment was thoroughly steam-cleaned before drilling began, to ' prevent the introduction of contamination from off site, and between borings to prevent cross contamination. The borings were logged under the direct supervision of a registered professional ' using the Unified Soil Classification System. The color, texture, moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil or bedrock characteristics, and any evidence of contamination will be noted. All water-bearing zones and the depths at which they were encountered are noted on these logs. All borings; were drilled in such a manner as to g prevent cross contamination between strata. Exploratory soil borings within the unsaturated zone were ' backfilled with Bentonite and cement. 6 1