(1)While a disposal licence issued by a disposal authority is in force, then—
(a)subject to any regulations in force by virtue of subsection (1) of the preceding section, the authority may—
(i)on its own initiative, serve a notice on the holder of the licence modifying the conditions specified in the licence to any extent which, in the opinion of the authority, is desirable and is unlikely to require unreasonable expenditure by the licence holder, and
(ii)on the application of the licence holder, serve a notice on him modifying the said conditions to the extent requested in the application ; and
(b)it shall be the duty of the authority to serve a notice on the licence holder modifying the conditions specified in the licence—
(i)subject to subsection (4) of this section, to the extent which in the opinion of the authority is required for the purpose mentioned in section 9(1)(a) of this Act, and
(ii)to the extent required by any regulations in force as aforesaid.
(2)Subsection (4) or, in relation to Scotland, subsection (5) of section 5 of this Act shall with the necessary modifications apply to a proposal to serve a notice in pursuance of paragraph (a) or paragraph (b)(i) of the preceding subsection as it applies to a proposal to issue a disposal licence, except that—
(a)the disposal authority may postpone the reference in pursuance of the said subsection (4) or (5) so far as the authority considers that by reason of an emergency it is appropriate to do so ; and
(b)the disposal authority may disregard any other authority for the purposes of the preceding provisions of this subsection in relation to a modification which, in the opinion of the disposal authority, will not affect the other authority.
(3)Section 5(6) of this Act shall apply to an application in pursuance of subsection (1)(a)(ii) of this section as it applies to an application for a disposal licence.
(4)Where a disposal licence issued by a disposal authority is in force and it appears to the authority—
(a)that the continuation of activities to which the licence relates would cause pollution of water or danger to public health or would be so seriously detrimental to the amenities of the locality affected by the activities that the continuation of them ought not to be permitted ; and
(b)that the pollution, danger or detriment cannot be avoided by modifying the conditions specified in the licence,
it shall be the duty of the authority by a notice served on the holder of the licence to revoke the licence.
(5)A notice served in pursuance of this section shall state the time at which the modification or revocation in question is to take effect.