Section 27-665. Boring methods

Borings shall be made by continuous driving
  and cleaning out of a pipe  casing  (including  telescoping  of  smaller
  sizes  inside of larger casing) except as permitted in subdivisions (a),
  (b), and (c) of this section. Where casing is used, it shall be  cleaned
  out  to  undisturbed  soil prior to sampling and the sample spoon driven
  into  soil  that  has  not  been  affected  by  chopping,  washing,   or
  hydrostatic imbalance.
    (a)  Uncased  borings.  Uncased  borings,  including borings where the
  casing is omitted for part of the depth, may be used if the  mud  slurry
  method  is  followed. The requirements for soil sampling and rock coring
  shall be the same for uncased borings as for borings made using  casing,
  except  that  prior  to each soil sampling operation the boring shall be
  substantially cleaned of disturbed material and the sample  spoon  shall
  be  advanced  through  any  settled  solids  before  counting  the blows
  required to drive the spoon.  Longer  sample  spoons,  having  a  sludge
  chamber,  shall  be  used  where  settled  solids  exceed  six inches In
  determining ground water levels, methods shall be  used  to  reduce  and
  replace the mud slurry so that the hydrostatic head may be measured. The
  procedures shall be described in detail in the records.
    (b)  Auger  borings. Borings may be made with augers except that short
  flight augers shall not be used in granular soils below the water level.
  Sampling procedures in auger borings for both soil and rock shall be the
  same as for cased borings. Full hydrostatic head shall be maintained  in
  granular soils below the ground water level during the boring operation.
    (c)  Maximum  diameter. Where the bore hole, as drilled by any method,
  is in excess of four inches in diameter, sampling  operations  shall  be
  performed  through a temporary casing having a four inch inside diameter
  or less.