Section 27-670. Lateral loads

(a) Earth and ground water pressure. Every
  foundation wall or other wall serving as a retaining structure shall  be
  designed  to  resist,  in addition to the vertical loads acting thereon,
  the incident lateral earth pressures and  surcharges,  plus  hydrostatic
  pressures  corresponding  to  the  maximum  probable ground water level.
  Retaining walls shall be designed to resist at  least  the  superimposed
  effects  of  the  total  static  lateral  soil  pressure,  excluding the
  pressure caused by any temporary surcharge, plus an earthquake force  of
  0.045wsh¥  (horizontal backfill surface), where ws equals unit weight of
  soil and h  equals  wall  height.  Surcharges  which  are  applied  over
  extended  periods  of time shall be included in the total static lateral
  soil pressure and their earthquake lateral force shall be  computed  and
  added  to  the  force  of  0.045wsh¥. The earthquake force from backfill
  shall be distributed as an inverse triangle over the height of the wall.
  The point of application  of  the  earthquake  force  from  an  extended
  duration  surcharge  shall be determined on an individual case basis. If
  the backfill consists of loose saturated  granular  soil,  consideration
  shall be given to the potential liquefication of the backfill during the
  seismic loading using reference standard RS 9-6.
    (b)  Wind  and  other superstructure loads. Provision shall be made to
  resist lateral loads imposed on the superstructure due to wind or  other
  causes.
    (c)  Soil movements. Buildings shall not be constructed in areas where
  the soil is subject to lateral movements unless  positive  provision  is
  made to prevent such movements.