WORK PLANS - Laserfiche WebLink

Home Browse Search

V CG.>afagicafTechnics 7m. `�` >1 Page 2 *&B Equipment Additional Site Characterization WP Addendum Project No. 336.2 April 7, 1997 2.0 LATERAL DEFINITION OF THE GROUNDWATER PLUME .. The following work is proposed to define the lateral extent of the groundwater plume at C & B Equipment. Except where noted, all drilling and sampling will be conducted as per the Geological Technics Inc. June 15, 1996 Monitoring Well Installation and Groundwater Monitoring Work Plan. 2.1 Soil Boring To further investigate the extent of gasoline range petroleum hydrocarbons in the groundwater environment, Geological Technics Inc. proposes to install five exploratory borings, to be completed as monitoring wells, surrounding the point of release. The borings will be advanced using continuous flight hollow stem augers (HSA). Leh The HSA boreholes will be advanced to the capillary fringe and soil samples will be collected at 3 foot intervals down to the capillary fringe. In four of the borings, samples will 2 continue to be collected at five foot intervals, in order to define geology, to a total depth of 20 feet. Groundwater at this site ranges from approximately seven to eight feet below grade. �- For the fifth borehole see section 3.2 "Drilling and Sampling". 2.2 Monitoring Well Installation We propose to install four shallow monitoring wells screened through the water table (MW- 4-8) in order to define the lateral extent of the plume in the predominant down gradient and cross gradient directions from the point of release and to allow the detection of free phase `- floating product if present. The well boring will be drilled using a 8.0 inch outside diameter continuous flight hollow .. stem auger owned and operated by V&W Drilling (C579 720904). Soil cuttings will be placed in drums and stored on site until their disposition can be determined. MW-4-8 will be constructed using 2.0 inch diameter schedule 40 PVC casing with flush threads. A 15 foot screened interval will extend from 5 feet to 20 feet below surface grade (Figure 3 Well Construction Schematic). A #3 sand filter pack will surround and extend two eyfeet above the 0.020" screened interval. A granular bentonite transition seal will be installed �- r and hydrated. A surface seal will be achieved by pumping a neat cement grout (augmented b� 4 with < 4% bentonite) via a tremie tube. The well will be secured with a locking watertight cap encased in flush mounted traffic rated well box. After the well sealing materials have set (>24 hours) the well will be developed (using �►�� mechanical surging and pumping methods) until a clear stream of water is obtained. The well will be purged and groundwater samples collected no sooner than 24 hours after well development. All development and purge water will be containerized in 55 gallon DOT approved drums and stored on site until their disposition can be arranged. V V V