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Initially,four hydrogeologic zones(A, B, C, and D zones)were identified at the Facility(SECOR, 2002). The currently understood conditions suggest that the A and B zones are not as continuous as previously reported and are likely hydraulically connected. The stratigraphy underlying the northern portion of the Facility dips to the east, with little to no dip underlying the southern portion of the Facility. Based on the 2008/2009 investigations, the water-bearing zones in the southern portion of the leasehold can be summarized as follows: • A/B Zone. The A/B zone is comprised of laterally discontinuous and intermittently connected sand and clay layers of various thicknesses. At the Facility, the A/B zone is first encountered at ground surface (with the exception of locations where surface fill or pavement is present) and ranges from 20 to 40 feet in thickness. • C Zone. The C zone is generally separated from the A/B zone by 2 to 10 feet of silt and clay and is typically hydraulically isolated from the A/B zone except in the eastern portion of the Facility (near location OW-7). The C zone generally ranges from 10 to 28 feet in thickness and is the most laterally and vertically continuous sand layer under the Facility. • D Zone. The D zone is generally separated from the C zone by 3 to 10 feet of silt and clay and consists of thin, laterally discontinuous sand layers that are interbedded with silt and clay. At the Facility, the D zone is generally encountered at a depth of 47 to 70 feet below ground surface(bgs). More detailed descriptions of the hydrogeologic conditions and currently understood nature and extent of hydrocarbons at the Facility are presented in the Vertical Groundwater Investigation Results Report(Ash Creek,2009a)and the Subsurface Investigation Report(Ash Creek, 2009b). 3.0 Well Relocation Activities The following work is proposed to relocate two monitoring wells to accommodate construction of a new railroad spur. 3.1 Scope of Work The scope of work is described below. Work will be conducted consistent with NuStar drilling protocols (NuStar, 2003). Pre-Field Activities. An underground utility locate request will be submitted to the Underground Service Alert (USA) North. In addition, a private utility locator will be retained to clear the locations prior to performing the subsurface work. ' ■ Work Plan for Monitoring Well Relocation Page 2 " NuStar Stockton Terminal-Stockton,California May la 2011 1014-10