In any case where—
the enforcing authority shall, in accordance with such procedure as may be prescribed and subject to the following provisions of this Part, serve on each person who is an appropriate person a notice (in this Part referred to as a "remediation notice") specifying what that person is to do by way of remediation and the periods within which he is required to do each of the things so specified.
Different remediation notices requiring the doing of different things by way of remediation may be served on different persons in consequence of the presence of different substances in, on or under any land or waters.
Where two or more persons are appropriate persons in relation to any particular thing which is to be done by way of remediation, the remediation notice served on each of them shall state the proportion, determined under section 78F(7) below, of the cost of doing that thing which each of them respectively is liable to bear.
The only things by way of remediation which the enforcing authority may do, or require to be done, under or by virtue of this Part are things which it considers reasonable, having regard to—
In determining for any purpose of this Part—
the enforcing authority shall have regard to any guidance issued for the purpose by the Secretary of State.
Regulations may make provision for or in connection with—