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Musco Family Olive Company - 2 - 29 September 2006 • The companion boring (MW-21) proposed to be drilled southeast of well W-2 will be continuously-cored. The Discharger should drill well MW-21 first since it is located in the vicinity of well MW-17, where known groundwater is located. Staff will be present for,the advancement of well boring MW-20 and MW-2.1. J, •° 1f.very:mo.Jst,oriwet (saturated) zones are encountered in the target zone of 50 to .70 feet bgsin.any•of the shallow well borings, the Discharger shall construct a groundwater monitoring well. • Due to the variable nature of groundwater conditions beneath this site, the quantity of groundwater, and the time of year drilling is being proposed, the Discharger shall maintain the open borehole overnight at all shallow well boring locations that do not have conclusive evidence of very moist to wet (saturated) conditions in the target zone of 50 to 70 feet bgs. This will allow time for groundwater to flow into the borehole from - "' water bearing'zones missed by d'_ill'loggerS""""""'`� • The Discharger shall utilize downhole geophysical techniques to correlate geologic strata between well borings and verify water-bearing zones. Downhole logging of the well borings will significantly improve characterization of the borehole subsurface. The Discharger shall log the well boreholes using a Neutron-Neutron Porosity Log or equivalent technique and a downhole camera. if multiple techniques are required to confirm the findings, then the Discharger shall perform these also. Downhole logging shall be supervised by a California Professional Geophysicist. Employing these additional field measurements, field staff, Musco management, and the Regional Water Board will gain a greater degree of confidence associated with the field observations and the decisions made concerning well installation. If very moist or wet (saturated) zones are identified in the target zone of 50 to 70 feet bgs by either visual logging or downhole geophysical techniques, then groundwater monitoring wells shall be constructed, as discussed in the previous point above. • The Discharger has proposed to drill the well borings using a truck mounted drill rig equipped with 6-inch diameter hollow stem auger. The wells will be constructed with 2-inch diameter well casing fitted with 20-feet of machine-slotted well screen. The Discharger is proposing to adjust screen lengths in the field based on lithology and -�- groundwater zones encountered. Staff disagrees with this plan. The Discharger shall not install short screen intervals in an attempt to screen discrete intervals observed in the field. The Discharger shall base screen length on anticipated highs and low of groundwater fluctuation recorded in Well MW-17. Well MW-17 is screened from 45 to 65 feet bgs with a recorded depth to water (DTW) high of approximately 50 feet bgs and DTW low of approximately 60 feet bgs. The Discharger shall maintain the proposed 20-foot screen interval. • According to Department of Water Resources (DWR) Bulletin 74-90 (Supplement to Bulletin 74-81), Section 9. C. Radial Thickness of Seal states- "aminimum of two inches of sealing material shall be maintained between at/casings and the borehole wall." The outside diameter of 2-inch polyvinyl chloride (PVC) well casing is 2.375 inches. The outside diameter of a 6-inch diameter hollow stem auger is 6.25 inches leaving