15
Impact from Electric and Magnetic Field
15.1.1.1
This section presents the assessment on the potential impact
from exposure to electric and magnetic field generated from the overhead
electricity cables. The assessment on impact from electric and magnetic field has been
conducted in accordance with the requirements in Section 3.4.15 of the EIA
Study Brief (ESB-363/2023).
15.2.1.1
Guidelines on limits of
exposure to electric field (ELF)
and electro-magnetic field (EMF)
were issued by the International Commission on
Non-ionizing Radiation Protection (ICNIRP) in Year 1998 [1]. The guidelines were updated
in Year 2010 [2] and were recognised by the
World Health Organization.
According to the ICNIRP (1998) guidelines, ELF and EMF generated from
the overhead cables shall comply with the limits stated in Table 15.1.
Table 15.1 Guidelines
on Limits of Exposure to 50 Hz Power Frequency Electric and Magnetic Fields
Issued by ICNIRP
|
Exposure
Characteristics
|
Electric
Field Strength, V/m (1)
|
Magnetic
Flux Density, ¦ĚT (1)
|
|
General Public
Continuous
|
5,000 (2)(3)
|
100 (2)
200 (3)
|
|
Occupational
Continuous
|
10,000 (2)(3)
|
500 (2)
1000 (3)
|
Notes:
(1) Unperturbed
root-mean-square (rms) values.
(2) The
standards stipulated in Guidelines following the ICNIRP (1998) limits for 50 Hz
electric and magnetic fields.
(3) The standards stipulated in
Guidelines following the ICNIRP (2010) limits for 50 Hz electric and magnetic
fields.
Hong Kong Planning Standards and Guidelines
15.2.1.2
As stated in Clause 2.3.10 of
Chapter 7 of the Hong Kong Planning Standards and Guidelines (HKPSG), the EMF
exposure limits promulgated in the guidelines issued by ICNIRP in 1998 are
adopted. The relevant standards are
presented in Table 15.1.
15.2.1.3
As the ICNIRP (1998) guidelines
on magnetic flux density are more stringent than that in the ICNIRP (2010), the
ICNIRP (1998) guidelines was adopted
as the assessment criteria in this Study as a conservative approach.
15.3.1.1
ELF and EMF are present everywhere in our environment. ELF is generated
by difference in voltage. The
higher the voltage, the stronger the resultant ELF will be. EMF is created by electric current. The greater the current, the stronger
the EMF will be. ELF and EMF are
produced by virtually all electrical consumer appliances, computer terminals,
wiring in homes, offices and power lines.
15.3.1.2
A portion of the 400 kV overhead cables of approximately 350 m long is located within
the Development Area near Ching Yau Road and Wang Ping Shan South Road. The areas within the Development Area
underneath the overhead cables are currently zoned as Green Belt and
Comprehensive Development Area (Figure 15.1 refers). These areas are largely occupied by open
storage areas and villages.
Residents in these areas, as well as workers in the open storage areas
and brownfield sites, may be exposed to ELF and EMF associated with the
overhead cables to varying degrees.
15.3.1.3
The overhead cable and
associated pylons are situated near / at the southern and eastern portions of
the Development Area (Figure 15.1 refers). As such, the potential ELF and EMF
impacts to the proposed developments at these portions of the Development Area
were assessed. According to the Recommended
Outline Development Plan (RODP), the proposed land uses of Development Area
under/in the vicinity of the overhead cable are presented in Table 15.2 and illustrated in Figure 15.1.
Table
15.2 Proposed Land Use under / in the Vicinity
of the 400 kV Overhead Cable
|
Proposed Land Use
|
Approx. Horizontal
Distance between the Proposed Land Use and 400 kV Overhead Cable, m
|
|
Site ID
|
Land Use
|
|
OU(RDCRD).1(1)
|
Other Specified Uses (Railway Depot with Commercial / Residential Development)
|
0
|
|
A.5(2)
|
Amenity
|
0
|
|
A.6(2)
|
0
|
|
OU(RF).1(2)
|
Other Specified Uses (Railway Facility)
|
8
|
|
GB.2
|
Green Belt
|
61
|
|
G.5(1)
|
Fire Station Cum Ambulance Depot
|
8
|
|
G.8
|
Integrated Hospital
|
72
|
|
G.9(2)
|
Electricity Substation for the Integrated Hospital
|
80
|
|
G.11
|
UniTown
|
72
|
|
G.12
|
48
|
|
G.13(3)
|
Government, Institution or Community
|
12
|
Notes:
(1) The proposed buildings, which would be subject to continuous exposure of
ELF and EMF, would be situated at no less than 31 m away from the existing 400
kV overhead cables.
(2) Occupants of this land use are transient in nature and therefore
continuous exposure of ELF and EMF is not expected.
(3) The land use and building layout at Site G.13 is not available in the
preparation of this assessment.
15.4.1.1
In assessing the electric and magnetic
field impact arising from the existing 400 kV overhead cables, reference was made to two approved EIA reports,
namely Development at San Hing Road and Hong Po Road, Tuen Mun (Register No.:
AEIAR-227/2020) (SHR & HPR EIA report) and San Tin / Lok Ma Chau
Development Node (Register No.: AEIAR-261/2024) (STLMC DN EIA report).
Given that the strength of ELF and EMF depends only on the voltage and
distance from the sources, both of these approved EIA
reports provide valuable measurement results for assessing the potential ELF
and EMF impact from the 400 kV overhead cables. It is
worth noting that the existing 400 kV overhead cables near / at the Development Area are exactly the ones
assessed in the approved STLMC DN EIA report.
15.4.1.2
According to the approved SHR
& HPR EIA report, the maximum ELF measured directly underneath
the overhead cables was 288 V/m (rms), while the magnetic field peaked at 4.88 ¦ĚT (rms). Similarly, the approved STLMC DN EIA report documented a maximum
electric field of 198 V/m (rms) and a magnetic field of 1.40 ¦ĚT (rms) were measured directly underneath the overhead
cables. ELF and EMF measurements in
both EIA studies were carried out in accordance with the ELF and EMF standards
stipulated in Chapter 7 of the HKPSG and the ICNIRP (1998)
guidelines. Notably, the measured ELF and EMF values
in both approved EIA reports are only a few percentage
of the exposure limits set out in the ICNIRP (1998)
guidelines.
15.4.1.3
This consistent observation across
two separate EIA studies strongly indicates that the electric and magnetic
fields generated by 400 kV overhead cables are well within safe and acceptable exposure
standards, even at locations direct underneath the cables. According to the RODP, although few
sites will be directly beneath or in proximity to (i.e. less than 10 m) the existing 400 kV overhead cables, the proposed buildings within Sites OU(RDCRD).1 and G.5 will both be situated at no less than 31 m away horizontally from the overhead cables, while no continuous exposure is anticipated at Site
A.5, Site A.6 and Site OU(RF).1 in view of transient use of occupants of these
sites. For Site G.13 where continuous exposure is expected, the entire site will be situated at no less than 12 m
horizontally away from the overhead cables. Based on the findings as discussed in Section
15.4.1.2, it is anticipated that the existing overhead cables would not pose adverse electric and
magnetic field impact to the Development Area.
15.5.1.1
No adverse impact due to
exposure to ELF and EMF from existing 400 kV overhead cables is anticipated. Thus,
mitigation measure is deemed not necessary.
15.6.1.1
No residual impact due to
exposure to ELF and EMF from existing 400 kV overhead cables is anticipated to the
Project.
15.7.1.1
No adverse impact due to
exposure to ELF and EMF from existing 400 kV overhead cables is anticipated to the Project. Thus, environmental monitoring and audit
is deemed not necessary.
15.8.1.1
According to the RODP, the
existing 400 kV overhead cables are situated near/at the southern and eastern
portions of the Development Area. Based on the measurement results in previous
EIA studies, the ELF and EMF generated by the existing 400 kV overhead
cables, even at the area directly underneath the overhead cables, were only a
few percent of the general public and occupational exposure standards stated in
Table 15.1,
which are well below the stipulated limits in the ICNIRP (1998) guidelines. Hence, it is expected that the existing
400 kV overhead cables located within/in the vicinity of the Development
Area would not pose adverse impact on the proposed developments of the Project.