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ereologual recluucs ItW, Page 4 Monta Additional Site Characterization Report Project No 724 2 April 19,2004 ' previous days' rainfall and the drill rig became stuck in the mud in the vicinity of the proposed MW-110/-210 location After trying for half an hour the rig was freed from the mud and no further attempts were made to set up in this location On December 23, 2003, the drill company returned with a tracked vehicle and the last two wells were installed on that date (GTI retains photographic documentation of the mud problem) ' 2.1 Soil Boring Installation Prior to commencing work, a soil boring/monitoring well permit was secured from the ' County, an encroachment permit was secured from the City of Stockton and the SJC/EHD was notified at least 48 hours in advance The subsurface was cleared of underground utilities by notifying Underground Service Alert The borings were drilled using an 8 00-inch outside diameter continuous flight hollow stem auger owned and operated by V&W Drilling of Isleton, CA (C57# 720904) Soil cuttings were stockpiled on plastic and drilling decontamination water was placed in DOT-17 approved 55 gallon drums and retained at the site until their disposal can be arranged 2.2 Soil Sampling ' Soil samples were collected for geological evaluation at 5-foot intervals in borings MW-11, MW-208, MW-209 & MW-210 Borings MW-108/-1091-110 were free drilled to total depth due to their proximity to wells MW-208, MW-209 & MW-210 Boring MW-202 was M free drilled to 60 feet, then sampled every 5 feet to total depth due to it's proximity to well MW-2 In similar fashion, boring MW-111 was free drilled to 45 feet, then sampled every 5 feet to total depth due to it's proximity to well MW-11 Boring logs providing sediment ' description using the Uniform Soil Classification System (USCS) and field observations were completed by GTI geologists working under the supervision of Mr Ray Kablanow, a registered geologist Soil samples were collected using a 2 0 inch modified California split ' spoon sampler The following information was noted during borehole logging • Sediment type, including grain size, clay content and color • Moisture content Visible evidence of contamination, i e , color change due to reduction of iron or ' discoloration from hydrocarbons and other pollutants • OVM (Organic Vapor Meter) readings ' Details on the geology encountered during the completion of the boreholes as well as the field observations of contamination are included in Section 4 0, Geology and Field Observations ' 2.2 Monitoring Well Installation The monitoring wells were constructed using 2 0 inch diameter schedule 40 PVC casing ' with flush threads The following table illustrates the construction details