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Walin!f: Grove Ficvocr Prc&cL Loo;aLer i Imu a Soh -Moil Our ProjecL WuEtzh _r: May :L4, 200Y pressures should be used for walls that are free to rotate at the top. The following table presents the lateral earth pressures that may be used in the design of the wet wells. Lateral EarthPressure - Condition Equivalent fluid pressure, above groundwate Equivalent fluid pressure, below groundlwater, pcf At -rest 60 90 Active 40 80 Earthquake -induced 18 9 For the section of the structure below the groundwater, we recommend an additional equivalent fluid pressure of 19 pcf be used for the effects of hydrodynamic forces. This is in addition to the lateral earth pressures listed above. The resultant of the earthquake -induced lateral earth pressure force should be applied at a distance of 0.6 H (H being the height of the wet well wall) above the base of the wet wells. The above equivalent fluid pressures assume a granular backfill will be used against the sides of the wet wells. We understand a canopy structure will be Constructed over the electrical pad. The canopy structure will be supported on drilled piers. The drilled piers can be designed as friction piers. We recommend the drilled piers be designed using an allowable skin friction value of 750 pounds per square foot per foot: of depth. The upper two feet of subgrade soil should be neglected as providing any support to the drilled piers. The drilled piers should be a minimum of 12 inches in diameter and extend a minimum depth of 5 feet below the existing ground surface. If the piers extend below a depth of 8 feet, it will be necessary to case the pier or place concrete using the tremie method. The concrete mix design should take into account whether or not the pier will extend below the groundwater table. The drilled piers should be spaced at least 21/2 pier diameters, center to center distance, The reinforcing for the drilled piers should be provided by the structural engineer. 6.6 Testing, %nspectiorus and Revie w Our office should be afforded the opportunity of reviewing the completed foundation and grading plans to verify that our recommendations have been properly interpreted and incorporated. Unless our office is allowed this opportunity, we disavow any responsibility from problems arising from failure to follow geotechnical �� NEIL O. ANDERSON AND'(ASIS)OCIA T ES codc f�a 95a10 02007 NO O. Anderson & Assodates. nc.