Section 27-666. Probings and geophysical explorations

(a) Footings, pier or
  wall designs. Where the foundations for a proposed building  consist  of
  footings  or  foundation  piers  or walls bearing on rock of class 1-65,
  2-65 or 3-65, the use of probings, auger borings or geophysical methods,
  made without the recovery of soil samples or rock cores, may (except  as
  hereafter  specified) be substituted for up to one-half of the number of
  borings required by the provisions of subdivision (a) of section  27-663
  of  this article, provided that such probings, borings, etc. are carried
  to adequate depth and are of a nature that will  reasonably  define  the
  surface  contours  of  the  rock.  The  accuracy of such surface contour
  definition shall be confirmed by recovering rock cores at the  locations
  of  at  least one-fifth of the probings or auger borings or, in the case
  where geophysical methods are used, those borings which are  made  shall
  be  so  distributed  as  to  permit  confirmation of the accuracy of the
  geophysical  investigations.  The  provisions  of   paragraph   two   of
  subdivision (a) of section 27-663 of this article, shall not apply where
  the provisions of this section are invoked.
    (b)  Pile  support.  Where  the  foundation  for the proposed building
  consists of piling bearing on rock of class  1-65,  2-65  or  3-65,  the
  provisions of subdivision (a) of this section shall apply, provided that
  the  borings consistently show that the soil overlying the rock consists
  solely of deposits of class 6-65 through 11-65 and is free  of  boulders
  or other obstructions.
    (c) Geophysical methods. Geophysical investigations shall be conducted
  by  experienced  and  qualified personnel acceptable to the commissioner
  who may reject the results and require additional exploration by borings
  if the results of the geophysical explorations cannot be  satisfactorily
  correlated to the logs of the borings.