Where it appears to the appropriate agency that—
the appropriate agency shall be entitled to serve a works notice on any responsible person.
In this section "responsible person" has the same meaning as in section 161 or 161ZA) (as the case may be).
For the purposes of this section a works notice is a notice requiring the person on whom it is served to carry out such works or operations as may be specified in the notice.
The works or operations that may be so specified are works or operations which may be carried out under section 161(2) or (3) or section 161ZA(4) (as the case may be).
Where the appropriate agency has carried out any such investigations as are mentioned in sections 161(4) or 161ZA(5) and serves a works notice on a responsible person in connection with the matters to which the investigations relate it shall (unless the notice is quashed or withdrawn) be entitled to recover from that person the costs or expenses reasonably incurred in carrying out those investigations.
The appropriate national authority may, if it thinks fit in relation to any person, give directions to the appropriate agency as to whether or how it should exercise its powers under this section or section 161AA.
In this section and sections 161AA and 161AB "controlled waters" has the same meaning as in Part 3 of this Act.