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�1 NOW, V GeologicaI Technzrs Inc. Page 3 BioventingBiosparging Pilot Test Work Plan Project No.770.2 June 9,2006 as 38 feet in CPT-5 to as deep as 49 flet in MW-1. The layer varies in thickness from seven feet in CPT-1 to less than two feet in CPT-10.�A visual analysis of the subject depth soil samples retained in chip boxes at GTI's office affirm that the samples appear to be from the same unit(s). In a predominantly silty/clayey soil profile this feature has the potential to be a preferential pathway for contaminant migration. Other sand units with a thickness of less than a few feet to several inches were identified at the site but they were not shown to be continuous in lateral extent. • As documented in our April 20, 2006 "Site Conceptual Model (March 2006 Revision)" veins and/or fractures identified in soil samples appear to be a direct route for the vertical migration of the diesel. 2.2 Hydrogeology There are no surface water bodies near the area of sufficient size or volume to act as a hydrogeologic boundary. An irrigation ditch/canal is adjacent to the north of the parcel and it may act as a shallow aquifer recharge source. Regionally, groundwater is utilized as a source r for domestic, agricultural, and industrial supply water. The groundwater elevations observed in the water table wells ranged from approximately -31 to -44 feet mean sea level (MSL) since August 2000. This corresponds to a depth to groundwater of 56 - 67 feet below grade surface (bgs). The site's shallow aquifer displays highly variable shifts in groundwater direction. But the groundwater direction has been predominantly to the southeast since additional wells were installed in May 2002. The horizontal gradient measurements for the study area range from 0.0001 to 0.017 ft/ft during the 2000—2005 monitoring period. The deep well groundwater elevations also ranged from approximately -31 to -44 feet mean sea level (MSL) since August 2000. This corresponds to a depth to groundwater of 56 - 67 feet below grade surface (bgs). The deeper aquifer flow has been consistently to the east except for the April 28 and May 23, 2003 events, during which time the gradient reversed 180°from an easterly direction to a westerly direction. This suggests that the regional well pumping causes significant fluctuations in groundwater direction. The horizontal gradient measurements for the deeper aquifer level ranged from 0.001 to 0.007 ft/ft during the 2000— 2005 monitoring period. Vertical gradients have been calculated for the MW-5/105 &MW-6/106 well pairs during the investigation. Similar to the historical lateral directions, the direction of groundwater in the vertical plane also fluctuates at the site. Both positive and negative vertical gradients have been calculated for the site. The magnitude of vertical groundwater flow direction ranged from—0.02 to 0.01 for the site investigation.