21. —(1) Workers engaged in essential or emergency works—  where they have travelled to the United Kingdom in the course of their work.  (2) For the purposes of sub-paragraph (1)—  22. —(1) Workers engaged in essential or emergency works relating to flood and coastal erosion  risk management on behalf of—  (2) For the purposes of sub-paragraph (1)—  23. —(1) Workers engaged in essential or emergency works—  (a) related to water supplies and sewerage services; and  (b) carried out by, for, or on behalf of a water undertaker, sewerage undertaker, water supply  licensee, sewerage licensee or local authority,  (a) “essential or emergency works” includes—  (i) inspections, maintenance, repairs, and asset replacement activities,  (ii) monitoring, sampling and analysis of water supplies under the Private Water  Supplies (England) Regulations 2016( a ), the Water Supply (Water Quality)  Regulations 2016( b ), the Private Water Supplies (Wales) Regulations 2017( c ), or the  Water Supply (Water Quality) Regulations 2018( d );  (b) “sewerage licensee” means the holder of a sewerage licence under section 17BA of the  Water Industry Act 1991( e );  (c) “sewerage services” has the meaning given in section 219(1) of the Water Industry Act  1991( f );  (d) “water supply licensee” has the meaning given in sections 17A(7) and 219(1) of the  Water Industry Act 1991( g ).  (a) the Environment Agency; or  (b) a lead local flood authority in England.  (a) “flood” and “coastal erosion” have the meanings given in section 1 of the Flood and  Water Management Act 2010( h );  (b) “lead local flood authority” has the meaning given in section 6(7) of that Act;  (c) “risk management” has the meaning given in section 3 of that Act( i ).  (a) related to—  (i) a generating station,  (ii) an electricity interconnector,  (iii) a district heat network as defined in regulation 2 of the Heat Network (Metering and  Billing) Regulations 2014( j ),  (iv) communal heating as defined in regulation 2 of the Heat Network (Metering and  Billing) Regulations 2014,  (v) automated ballast cleaning and track re-laying systems on a network, or  (vi) the commissioning, maintenance and repair of industrial machinery for use on a  network; or  ( a ) S.I. 2016/618; relevant amending instruments are S.I. 2017/506, 2018/707 and 2019/558.  ( b ) S.I. 2016/614; relevant amending instruments are S.I. 2017/506, 2018/706 and 378, 2019/526 and 558.  ( c )  S.I. 2017/1041 (W. 270), as amended by S.I. 2018/647 (W. 121), S.I. 2019/460 (W. 110) and S.I. 2019/463 (W. 111).  ( d ) S.I. 2018/647 (W. 121), as amended by S.I. 2019/463 (W. 111).  ( e )  1991 c. 56. Section 17BA(6) was inserted by section 4(1) of the Water Act 2014 (c. 21). The reference to “sewerage  licensee” was inserted in section 219(1) by paragraph 120(2)(f) of Schedule 7 to the Water Act 2014.  ( f )  The definition of “sewerage services” was amended by paragraph 120 of Schedule 7 to the Water Act 2014.  ( g ) Section 17A was inserted by section 1 of the Water Act 2014.  ( h ) 2010 c. 29.  ( i )  And see section 2 of the Flood and Water Management Act 2010 for the meaning of “risk”.  ( j )  S.I. 2014/3120. There are no relevant amending instruments.  40