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Soil Investigation and Background Groundwater Monitorin*ell Installation Workplan January 17, 2007 C A M B R I A Underground Utility Location: The proposed drilling locations will be marked and Underground Service Alert will be notified of our site activities to identify utilities in the site vicinity. The area immediately around the proposed borings will be cleared to 8 fbg to minimize the potential for damaging underground utilities. Soil Borings: First of all, soil boring B-1 will be advanced in the center of the proposed infiltration/evaporation pond and will be continuously sampled to approximately 45 fbg or until bedrock is encountered. Next, three additional borings will be advanced and converted to groundwater monitoring wells MW-1 through MW-3.Borings MW-1 through MW-3 will be sampled every 5 feet to a depth of approximately 35 fbg.Soil borings will be observed by a Cambria geologist ® under direct supervision of a registered California Professional Geologist. The 10-inch diameter borings will be advanced with an air rotary drill rig.Soil samples will be collected with a split spoon sampler. Soil samples will be used for lithologic description and logged using the Unified Soil Classification System (USCS) in a boring/well log, in accordance with the standard operating procedures presented in Attachment B.All drilling equipment will be steam cleaned before use and in between borings. Well Installation:Well installation will be observed by a Cambria geologist under direct supervision of a registered California Professional Geologist. Groundwater is anticipated to be between approximately 15 and 25 fbg depending on the location and elevation of the proposed wells.The soil borings will be advanced to approximately 10 to 15 feet below the first encountered water table.The soil borings will be converted to groundwater monitoring wells and constructed with four-inch diameter,schedule 40 PVC casing with 0.010-inch screen,and#2/12 sand filter pack.The length of the screen interval will depend on the thickness of the aquifer and the depth to fust encountered groundwater.The screen interval will likely extend from approximately 5-to 10-feet above and 10- to 15-feet below the first encountered groundwater. Likely, no more than 20-feet of screen will be installed.The filter pack will extend from the bottom of the boring to approximately two feet above the top of the well screen.The sand filter pack will be settled by agitating the groundwater in the well before the placement of the sanitary seal.A two foot layer of hydrated bentonite chips will be placed on top of the filter pack. A portland cement grout will be placed continuously from the top of the bentonite to approximately one fbg. In accordance with local regulations, a San Joaquin County Environmental Health Department representative will be contacted to observe and direct grouting activities.Wells will be completed with watertight locking caps,an above grade,steel standpipe well- housing and,three bollards to protect the steel standpipe. Cambria's standard operating procedures for soil borings and well installation and a typical monitoring well construction diagram are included as Attachment B. 5