4.—(1) This paragraph applies where—
(a)a person is operating a highway drain, and
(b)that activity might lead to a discharge mentioned in paragraph 3(1)(a) or (b).
(2) The regulator may serve a notice on the person operating the highway drain requiring the person, from the date the notice takes effect, to hold an environmental permit authorising the carrying on of that activity.
(3) A notice under this paragraph takes effect on the date specified in it, which must be at least 6 months after it is served.