Section 24-521. Excavations for public works

a. Notice to public service
  corporations. Whenever any sewer, culvert, water main or pipe is  to  be
  constructed, altered or repaired in any street in which the pipes, mains
  or  conduits  of  public  service  corporations are laid, the contractor
  therefor shall give notice thereof in writing to such  corporations,  at
  least  forty-eight hours before breaking ground therefor. Such provision
  shall be included  in  every  contract  for  constructing,  altering  or
  repairing  any  sewer  or  culvert, water main or pipe, in any street in
  which the pipes, mains or conduits of public service corporations  shall
  be laid at the time of making such contract.
    b.  Public  service  corporations shall protect their property. Public
  service corporations whose pipes, mains or  conduits  are  about  to  be
  disturbed  by  the  constructing,  altering  or  repairing of any sewer,
  culvert, water main or  pipe,  shall,  on  the  receipt  of  the  notice
  provided  for  in the preceding subdivision, remove or otherwise protect
  and replace their pipes,  mains  and  conduits,  and  all  fixtures  and
  appliances  connected  therewith  or  attached thereto, where necessary,
  under the direction of the commissioner of design  and  construction  in
  accordance  with  chapter  fifty-five  of  the charter, unless otherwise
  directed by the mayor pursuant to such chapter.
    c. The enforcement of subdivisions a and b hereof shall be pursuant to
  sections 19-149, 19-150 and 19-151 of the code.