1 Topography, Land Use and Population

This section describes the methodology employed to determine the population in the vicinity of the proposed site at Black Point as well as the population to be adopted in the Quantitative Risk Assessment (QRA) study. The QRA considers the years 2011 and 2021 in the analysis and so the population was estimated for these years.

1.1 Location and Topography

The proposed site for the LNG Terminal at Black Point is located adjacent to the existing Black Point Power Station in the west of the New Territories. The surrounding habitat, with the exception of the existing power station, is predominantly hillside and bare land with a scattered village development approximately 1km from the site. Figure 1.1 shows an aerial photograph of the proposed Black Point terminal site.

1.2 Current Land Use

The current land use within a 2km radius of the proposed site at Black Point includes Lung Kwu Sheung Tan village and Government Land for Temporary Use, as well as the existing Black Point Power Station.

Further from the site, there is Lung Kwu Tan village at about 3km. Castle Peak Power Station and the neighbouring industrial sites lie about 4km from the proposed terminal site (Figure 1.2).

1.3 Land Population Estimation

The following information sources were referred to for population estimation:

· Site Survey Data [1]

· Population Survey Report [2]

· Census Data [3]

· Land Records from Lands Department

· Road Traffic Data [4]

· Data on Key Individual Developments

· Marine Traffic Data [5-7]

Figure 1.1 Aerial Photo of Black Point Site

Figure 1.2 Population in Vicinity of Black Point

1.3.1 Residential Population

There is no residential population within 2km of the Black Point site, apart from the village of Lung Kwu Sheung Tan which has just one house [8]. For simplicity, this population of 3 was combined with the industrial population in this area.

The population in other nearby villages was obtained from site survey data [1] and scaled by appropriate growth factors for their respective Planning Vision Strategy (PVS) [9] zone to give the predicted populations for 2011 and 2021 (Table 1.1). The dense urban areas of Tuen Mun and Yuen Long are about 7km away, too far from the terminal for even the worst case accident scenarios to have an impact at a frequency greater than 10^-9 per year. Castle Peak at 583m high also provides effective shielding to reduce the risks even further.

Table 1.1 Estimated Residential Population Data

Location	Approx. Distance from Terminal Site	2011 Population	2021 Population
Lung Kwu Tan village Ha Pak Nai village Lung Kwu Chau	3km 3.7km 4km	753 216 0	1,297 372 0

1.3.2 Industrial Population

According to data provided by Planning Department, Lung Kwu Sheung Tan and the government land allocated for temporary use (part of TPU432) are the only areas assumed to hold population within 2km radius of the Terminal [9]. As mentioned above, the village of Lung Kwu Sheung Tan has just one house and so this population was combined with the industrial population in this area to give the “Black Point Site Surrounding” population. The main industry in this area comprises of construction material storage areas and a cement plant. The population was estimated at 76 [1]. As a conservative estimate the population in 2021 is assumed to increase by 30% and, for simplicity, the population in 2011 is taken to be the same.

A similar 30% increase was applied to other industrial sites to give the data presented in Table 1.2 [1].

Table 1.2 Industrial Facility Population

Location	Approx. Distance from Terminal Site	2011 Population	2021 Population
Black Point Site Surrounding WENT Landfill Castle Peak Power Station Green Island Cement Plant Shui Wing Steel Plant Siu Lang Shui Landfill Site Office	1km 3km 3.5km 4.5km 4.8km 4.9km	100 194 1,102 177 390 7	100 194 1,102 177 390 7

Ammonium Nitrate Facility

A site for manufacturing and storage of Ammonium Nitrate Emulsion Compound, trade name EP Gold Emulsion, is located near the Black Point site to the southeast of the proposed LNG terminal, about 1km away behind a hill.

The population of this site is included in “Black Point Site Surrounding”, however, the facility has a licence to store 2x20 tonne containers of Ammonium Nitrate and 1 x 5 tonne containers of Ammonium Nitrate Emulsion (‘EP Gold”), both classified as UN Class 5.1, Oxidising Substance.

Because of its distance from the terminal, together with the shielding effect provided by the hill, the impact on the LNG terminal due to the ammonium nitrate storage is considered to be negligible.

1.3.3 Road Traffic Population

Access to Black Point Power Station is via Lung Kwu Tan Road and this is the only road providing access to villages and industrial sites in this western region of New Territories.

The population estimation for Lung Kwu Tan Road is based on the 2005 Annual Traffic Census [4]. The AADT value is 4,380 vehicles per day for station number 5481 from Lung Fai St. to Tsang Kok. Assuming an average speed of 50km/hr and an average of 3 persons per vehicle, the number of persons on the road is:

No. of persons = (AADT x Vehicle Occupancy / 24 / Speed)

= 4,380 x 3 / 24 / 50 = 11 persons/km

The traffic along this section of road has increased at an average rate of 4.3% in recent years. Assuming this trend continues, the traffic will increase by 30% by the year 2011, and by 100% by the year 2021. The future population for both 2011 and 2021 is therefore conservatively estimated as 11 x 2 = 22 persons/km.

1.3.4 Occupancy and Indoor/Outdoor Fractions

The land population is categorised further into 4 time periods: night time, weekday, peak hours and weekend day. These are defined in Table 1.3.

Table 1.3 Population Time Periods

Time Period	Description
Night time Weekday Peak hours Weekend day	7:00pm to 7:00am 9:00am to 5:00pm Monday through Friday, 9:00am to 1:00pm Saturdays 7:00am to 9:00am and 5:00pm to 7:00pm, Monday to Friday 7:00am to 9:00am and 1:00pm to 3:00pm, Saturdays 3:00pm to 7:00pm Saturdays, and 7:00am to 7:00pm Sundays

The occupancy assumed [2] during these time periods is given in Table 1.4. Different occupancy figures are assumed for industrial, residential and road types of population. The proportion of the population outdoors is also assumed to vary according to type of population and time period (Table 1.4).

The hazards that can potentially affect offsite population are flash fires and thermal radiation from pool fires. Buildings are assumed to offer protection to its occupants for these events. The protection factor used is 90%, or equivalently the exposure factor is 10%. Scenarios are therefore assumed to affect 100% of the outdoor population and 10% of the indoor population.

Road vehicles are also assumed to offer some protection, although less than a building. An exposure factor of 50% is used for vehicles.

Table 1.4 Land Population Occupancy and Indoor/Outdoor Fractions

Population	Occupancy				% Outdoors
Type	Night	Peak	Weekday	Weekend day	Night	Peak		Weekday		Weekend day
Industrial Residential Road	10 % 100 % 10 %	10 % 50 % 100 %	100 % 20 % 50 %	10 % 80 % 20 %	5 % 0 % 0 %		10 % 30 % 0 %		10 % 10 % 0 %		10 % 20 % 0 %

1.4 Marine Population Estimation

Black Point is situated near Deep Bay. The marine traffic in the vicinity of Deep Bay includes passenger ferries, container ships and rivertrade vessels going to Guangzhou and other Pearl River Ports. Small fishing vessels and leisure crafts also contribute to the marine traffic in the Black Point region.

1.4.1 Vessel Population

The vessel population used in this study are as given in Table 1.5. The figures are based on BMT’s Marine Impact Assessment report [6] except those for fast ferries. The maximum population of fast ferries is assumed to be 450, based on the maximum capacity of the largest ferry operating in Urmston Road. However, the average load factors for fast ferries to Macau and Pearl River ports are 52% and 37% respectively while the overall average load factor considering all ferries is about 50% [7]. Hence, a distribution in ferry population was assumed as indicated in Table 1.5. This distribution gives an overall load factor of about 58% which is conservative and covers any future increase in vessel population.

Table 1.5 Vessel Population

Type of Vessel	Average Population per Vessel	% of Trips
Ocean-Going Vessel Rivertrade Coastal vessel Fast Ferries Tug and Tow Others	21 5 450 (largest ferries with max population) 350 (typical ferry with max population) 280 (typical ferry at 80% capacity) 175 (typical ferry at 50% capacity) 105 (typical ferry at 30% capacity) 35 (typical ferry at 10% capacity) 5 5	3.75 3.75 22.5 52.5 12.5 5.00

1.4.2 Marine Vessel Protection Factors

The population on marine vessels is assumed to have some protection from the vessel structure, in a similar way that buildings offer protection to their occupants. The degree of protection offered depends on factors such as:

· Size of vessel

· Construction material and likelihood of secondary fires

· Speed of vessel and hence its exposure time to the flammable cloud

· The proportion of passengers likely to be on deck or in the interior of the vessel

· The ability of gas to penetrate into the interior of the vessel and achieve a flammable mixture.

Small vessels such as fishing boats will provide little protection but larger vessels such as ocean-going vessels will provide greater protection. Fast ferries are air conditioned and have a limited rate of air exchange with the outside. Based on these considerations, the fatality probabilities assumed for each type of vessel are as given in Table 1.6.

Table 1.6 Population at Risk

Marine Vessel Type	Population	Fatality Probability	Population at Risk
Ocean-Going Vessel Rivertrade Coastal Vessel Fast Ferries Tug and Tow Others	21 5 450 350 280 175 105 35 5 5	0.1 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.9 0.9	2 2 135 105 84 53 32 11 5 5

1.4.3 Methodology

In this study, the marine traffic population in the vicinity of Black Point has been considered as both point receptors and average density values. The population of all vessels are treated as an area average density except for fast ferries which are treated as point receptors.

The marine area around Black Point was divided into 12.67km² grid cells, each grid being approximately 3.6km x 3.6km. The transit time for a vessel to traverse a grid is calculated based on the travel distance divided by the vessel’s average speed. The average speed [5] and transit time for different vessel types are presented in Table 1.7.

Table 1.7 Average Speed and Transit Time of Different Vessel Type [5]

Type of Vessel	Assumed Speed (m/s)	Transit Time (min)
Ocean-going vessel	6.0	9.9
Rivertrade Coastal vessel	6.0	9.9
Fast Ferries	15.0	4.0
Tug and Tow	2.5	23.7
Others	6.0	9.9

The number of vessels traversing each grid daily was provided by the marine consultant [5]. These are given in Table 1.8, where the grid cell reference numbers are defined according to Figure 1.3. The number of marine vessels present within each grid cell at any instant in time is then calculated from:

Number of vessels = No. of vessels per day x grid length / 86400 / Speed (1)

This was calculated for each type of vessel, for each grid and for years 2011 and 2021. The values obtained represent the number of vessels present within a grid cell at any instant in time. Values of less than one are interpreted as the probability of a vessel being present.

Figure 1.3 Grid Cell Numbering Scheme

Table 1.8 Number of Marine Vessels Per Day

OG = Ocean-going vessels

RT = Rivertrade coastal vessels

TT = Tug & tow vessels

FF = Fast ferries

OTH = others

Average Density Approach

The average marine population for each grid is calculated by combining the number of vessels in each grid (from Equation 1) with the population at risk for each vessel (Table 1.6). The results are shown in Figures 1.4 and 1.5. This grid population is assumed to apply to all time periods. Note however that fast ferries are excluded since ferries are treated separately in the analysis (see below).

When simulating a possible release scenario, the impact area is calculated from dispersion modelling. In general, only a fraction of the grid area is affected and hence the number of fatalities within a grid is calculated from:

Number of fatalities = grid population x impact area / grid area (2)

Figure 1.4 Marine Population at Risk by Grid, Year 2011

Figure 1.5 Marine Population at Risk by Grid, Year 2021

Point Receptor Approach

The average density approach, described above, effectively dilutes the population over the area of the grid. Given that ferries have a much higher population than other classes of vessel, combined with a relatively low presence factor due to their higher speed, the average density approach would not adequately highlight the impact of fast ferries on the FN curves. Fast ferries are therefore treated a little differently in the analysis.

In reality, if a fast ferry is affected by an accident scenario, the whole ferry will likely be affected. The likelihood that the ferry is affected, however, depends on the size of the hazard area and the density of ferry vessels. To model this, the population is treated as a concentrated point receptor i.e. the entire population of the ferry is assumed to remain focused at the ferry location. The ferry density is calculated the same way as described above (Equation 1), giving the number of ferries per grid at any instant in time, or equivalently a “presence factor”. A hazard scenario, however, will not affect a whole grid, but some fraction determined by the area ratio of the hazard footprint area and the grid area. The presence factor, corrected by this area ratio is then used to modify the frequency of the hazard scenario:

Prob. that ferry is affected = presence factor x impact area / grid area (3)

The fast ferry population distribution adopted was described in Table 1.5. Information from the main ferry operators suggests that 25% of ferry trips take place at night time, while 75% occur during daytime. Day and night ferries are therefore assessed separately in the analysis. The distribution assumed is given in Table 1.9.

Table 1.9 Fast Ferry Population Distribution for Day and Night Time Periods

Population	Population at Risk	% of Day Trips	% of Night Trips	% of All Trips (= 0.75 x day + 0.25 x night)
450 350 280 175 105 35	135 105 84 53 32 11	5 5 30 60 - -	- - - 30 50 20	3.75 3.75 22.5 52.5 12.5 5.0

The ferry presence factor (Equation 1) and probability that a ferry is affected by a release scenario (Equation 2) are calculated for each ferry occupancy category and each time period.

1.4.4 Stationary Marine Population

Stationary marine population in the vicinity of Black Point was also considered. Contributions to these populations come from the Tuen Mun Immigration Anchorage, Tuen Mun Rivertrade terminal, Tuen Mun Area 38 and Urmston Road Anchorage [5]. The population on each type of vessel (Table 1.5) was treated the same as mobile vessels and the same fatality factors (Table 1.6) were used to calculate the population at risk for each grid cell. The results are given in Figures 1.6 and 1.7. This population is assumed to be present during all time periods.

Figure 1.6 Stationary Marine Population at Risk (2011)

Figure 1.7 Stationary Marine Population at Risk (2021)

References

[1] ERM, Environmental and Risk Assessment Study for a Liquefied natural gas (LNG) Terminal in the Hong Kong SAR – Population Update Report, Dec 2004.

[2] ERM, Liquefied Natural Gas (LNG) Terminal and Associated Facilities – Marine Quantitative Risk Assessment, Population Survey Report, Jun 2006.

[3] www.censtatd.gov.hk

[4] The Annual Traffic Census 2005, Transport Department, Hong Kong SAR, Jun 2006.

[5] BMT Asia Pacific Ltd., personal communication, 2006

[6] BMT Asia Pacific Ltd, Marine Impact Assessment for Black Point & Sokos islands LNG Receiving Terminal & Associated Facilities, Pipeline Issues, Working Paper #3, Issue 6, May 2006

[7] Passenger Arrivals/Departures and Passenger Load Factors at Cross-Boundary Ferry Terminals, January to December 2005, Marine Department, Hong Kong SAR.

[8] Hong Kong 2030, Planning Vision and Strategy, Planning Department, Hong Kong SAR.

[9] Projected Hong Kong Resident Population by TPU, Planning Department, Hong Kong SAR, 2004