20.—(1) The regulator may vary an environmental permit on the application of the operator or on its own initiative.
(2) A variation under this regulation must not reduce the extent of the site of a regulated facility.
(3) Paragraph (2) does not apply if the variation relates to any part of an environmental permit (or if applicable, the whole permit) that authorises the operation of a regulated facility of the following description—
(a)a Part B installation, except to the extent that it relates to a waste operation;
(b)a stand-alone water discharge activity or stand-alone groundwater activity.
(4) With respect to any part of an environmental permit (or if applicable, the whole permit) that authorises the carrying on of a stand-alone water discharge activity, a regulator must not, without the agreement of the operator, on its own initiative—
(a)within 4 years after the grant of the permit, vary any condition of the permit that relates to the water discharge activity; or
(b)within 4 years after the variation of a condition of the permit that relates to the water discharge activity, further vary that condition.
(5) Paragraph (4) does not apply if—
(a)the regulated facility is a standard facility; or
(b)the regulator, on its own initiative, varies an environmental permit, or any condition of a permit, in order to comply with—
(i)an obligation of the United Kingdom under the Community Treaties; or
(ii)a direction given by the appropriate authority under regulation 61.
(6) Part 1 of Schedule 5 applies in relation to an application for the variation of an environmental permit or a proposal to vary an environmental permit on the initiative of the regulator under paragraph (1).