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06/30/99 WED 16:51 FAX 510 8 8205 CH2M HILL IM002 2. .;Grab groundwater samples can be collected of various depth intervals prior to installing 'wells.Thus will give us a vertical profile of the'grcundwater,and will ensure that we did not"miss" the plume. Adding this step may lend more credibility to our assumptions of where to screen.I have proposed that we use CPT for collecting these samples,CPT is a rapid tool,and the methodology eliminates most cross-contamination issues with multiple sample depths.I have included this as an additional item to the cost estimate. The scope is as follows: • Install"I boring to total"dep6of 150'using Resonant sonic drilling.Temporary conductor casing will be instilled to a depth of approximately 100 ft bgs. • Grab groundwater samples to be collected at depths of 110, 130,and 150 ft bgs, using Hydropunch'rll or similar tool,and rushed to the lab for overnight analysis. • This boring to remain open overnight,assuming a sufficient clay layer is encountered that the conductor casing can 'key' into. • Convert this boring to'a 2-inch PVC monitoring well.The exact depth of this well will be determined by the results of the of the grab groundwater samples. • "Install twa additi6&l2-i7nch PVC monitoring wells with 20-feet of 0.010 screen downgradient of first location using hollow-stem auger. These'wells to be installed on the freeway shoulder,and 4ill be separated by approxlmately60 to 80 feet. • Exact depths of wells to be determined by the results of the grab groundwater samples collected at first location.'Assume 90 ft bgs for costing purposes.'These wells to be installed at a depth that corresponds with to the most contaminated zone beneath the site (i.e.likely between 70 and 90 ft bgs.) • Additional scope for-CPT grab'groundwater samples for 3owngradient wells: ' • Install 1 CPT boring for lithologic interpretation to a total depth of 130 ft bgs. • Install 2 CPT borings to 40 ft bgs and collect a grab groundwater sample from each boring. • Install 2 CPT borings to 70 ft bgs and collect a grab groundwater sample from each boring_ • Install CPT borings to 110 ft bgs and collect a grab groundwater sample from each boring. • If'two additional S'VE"wells are to be installed during this scope of work,add an c additional$5000 to this scope of work. Please call me at the above listed number of you have any questions. please call if pages ars missing or illegible or if you receive this fax In error. 06/30/99 WED 15:47 [TX/RX NO 86421