2530 MADISON ST 2016-01-01 MF Import

lAirTouch Cellular 7-91 M•1 7 9G"a-0 3 Octo6er 1997 Pape 5 IFrozen S��bara es: If earthwork takes place dur�rig freezing conditions, we recommend that all exposed subgrades be ai!owed to thaw and then be recompacted, i� necessary, � prior to placing subsequent lifts of structural fill or foundation r,omponents. 4_2 Equionent Shelter Foundations VJe an;icipate that the prefabricated equipment shelter will be placed on shallow concrete faotings and that bearing pressures will be relatively low. Our specific conclusions and recemmendations are presented below. ' Subarade Condit�ons: Footing subgrades should consist of firm, unyielding structural fill or granular native soils. Footings should never be cast atop soft, loose, organic, or frozen ! soils, nor a[op subgrades covered by standing water. An AEE representative should be allowed to observe all subgrades before any concrete is poured and to verify that they have baen adequately prepared. '_ Footina Deoths: For frost and erosion protection, a!I exterior footings should be embedded at least 18 inches below exterior finish grades. ':� '. �_ � �_ � � r Bearina Caoacities: We recommend utilizing a maximum allowable bearing capacity of 1,500 pounds per square foot (psf) for the equipment building foundations supported on the loose to medium danse, silty sands with some gravei. The allowable bearin� capacities may be increased by one-third to resist short-term transient loads such as wind and seismic forces. Lateral Resistance: Lateral forces on the fou-�dation caused by seismic or transient lo,idi�ic� conditions may be resisted by a combination of passive soil pressure against the sidtr eS the foundation and shear friction resistance along the base. An allowable 6ase friction value of 0.35 would be appropriate, in our opinion. An al:�wable passive earth pressuie of 250 pounds per cubic foot (ncf), expressed as an equivalent fluid unit weight, may be used for that portion of the foundation embedded rrore than 1 fout below finished exterior subgrade elevation. Settlements: lNith the footing subgrade areas prepared as described abrve, we would not expect settlements greater than 1 inch. Settiaments may be greater than this if ioose subgrade soils are leit �vithin footing areas. On the other nand, we would expect less settiement if the actual foundaiion Ioa:ls are less than the allowable maximum soil bearing pressure given above. 4_3 Tower Foundati;ens The foundation support for a self-supporting communications tower typically consists of either drilled piers or a mat footing, in order to provide adPquate resistance to vertical, horizontal and overturning forces. In our opinion, drilled pirrs and mat footings are both 7�B1M•11906-0 I