TABLE OF CONTENTS

5.    WATER QUALITY.. 5-1

5.1       Introduction.. 5-1

5.2       Environmental Legislation, Standards and Guidelines.. 5-1

5.3       Description of Environment. 5-4

5.4       Water Sensitive Receivers.. 5-10

5.5       Assessment Methodology.. 5-10

5.6       Identification of Environmental Impacts.. 5-10

5.7       Evaluation of Environmental Impacts.. 5-11

5.8       Mitigation Measures.. 5-16

5.9       Residual Environmental Impacts.. 5-19

5.10     Environmental Monitoring and Audit. 5-19

5.11     Conclusion.. 5-19

 

List of Tables

Table 5.1         Summary of Water Quality Objectives for Tolo Harbour and Channel WCZ

Table 5.2         Summary Statistics of Marine Water Quality in Tolo Harbour and Channel WCZ (TM6 & TM7) in 2019

Table 5.3         Summary of Baseline Water Quality Survey Results

 

List of Figures

Figure 5.1           Locations of EPD’s Marine Water Quality Monitoring Stations

Figure 5.2           Locations of the Representative Water Sensitive Receivers and Baseline Water Quality Survey Stations

 

List of Appendix

Appendix 5.1      DSD’s “Contingency Plan for Incidents Possibly Encountered in Sewage Treatment Facilities having a Potential of Generating an Environmental Nuisance”

 

 

5.                    WATER QUALITY

5.1                 Introduction

5.1.1.1        This section presents the findings and recommendations of the assessment for water quality impacts associated with the construction and operation of the Project.  The water quality impact assessment was conducted in accordance with the guidelines in Annexes 6 and 14 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) and the technical requirement in Section 3.4.3 and Appendix D of the EIA Study Brief. 

 

5.2                 Environmental Legislation, Standards and Guidelines

5.2.1             Environmental Impact Assessment Ordinance

5.2.1.1        The Technical Memorandum on Environmental Impact Assessment Process (Environmental Impact Assessment Ordinance) (EIAO-TM) was issued by EPD under Section 16 of the EIAO.  It specifies the assessment method and criteria that are to be followed in an EIA Study.  Reference sections in the EIAO-TM provide the details of assessment criteria and guidelines that are relevant to the water quality impact assessment, including:

l   Annex 6 – Criteria for Evaluating Water Pollution

l   Annex 14 – Guidelines for Assessment of Water Pollution

5.2.2             Water Pollution Control Ordinance

5.2.2.1        The Water Pollution Control Ordinance (WPCO) provides the major statutory framework for the protection and control of water quality in Hong Kong.  According to the WPCO and its subsidiary legislation, Hong Kong waters are divided into ten water control zones (WCZs).  Corresponding statements of Water Quality Objectives (WQO) are stipulated for different water regimes (marine waters, inland waters, bathing beaches subzones, secondary contact recreation subzones and fish culture subzones) in each of the WCZ based on their beneficial uses.  The study area is located within the Tolo Harbour and Channel WCZ and the corresponding WQOs are listed in Table 5.1.

Table 5.1       Summary of Water Quality Objectives for Tolo Harbour and Channel WCZ

Parameters

Objectives

Sub-Zone

Offensive odour, tints

Not to be present

Whole zone

Visible foam, oil scum, litter

Not to be present

Whole zone

Dissolved oxygen (DO)

Not less than 2 mg/L within two metres of the bottom, or not less than 4 mg/L in the remainder of the water column

Marine Waters in Harbour Subzone

Not less than 3 mg/L within two metres of the bottom, or not less than 4 mg/L in the remainder of the water column

Marine Waters in Buffer Subzone

Not less than 4 mg/L at any point in the water column

Marine Waters in Channel Subzone

Not less than 4 mg/L or 40% saturation (at 15 0C) at any time

Inland Waters

pH

Not to cause the normal pH range to be extended by more than ±0.5 pH units at any time.

Marine Waters in Harbour Subzone

Not to cause the normal pH range to be extended by more than ±0.3 pH units at any time.

Marine Waters in Buffer Subzone

Not to cause the normal pH range to be extended by more than ±0.1 pH units at any time.

Marine Waters in Channel Subzone

Not exceed the normal pH range of 6.5-8.5 at any time

Inland Waters in Shing Mun (A, B, C, F, G, H) subzones

Not exceed the normal pH range of 6.0-9.0 at any time

Inland Waters in Shing Mun (D, E, I) subzones and other watercourses

Light Penetration

Should not reduce light transmission by more than 20% of the normal level at any location or any time.

Marine Waters in Harbour Subzone

Should not reduce light transmission by more than 15% of the normal level at any location or any time.

Marine Waters in Buffer Subzone

Should not reduce light transmission by more than 10% of the normal level at any location or any time.

Marine Waters in Channel Subzone

Salinity

Not to cause the normal salinity range to be extended by more than ±3 parts per thousand at any time.

Marine Waters

Temperature

Not to cause the natural daily temperature range to be extended by greater than ±1.0 °C at any location or time.  The rate of temperature change shall not exceed 0.5 °C per hour at any location, unless due to natural phenomena.

Marine Waters

Not to cause the natural daily temperature range to be extended by greater than ±2.0 °C at any location or time. 

Inland Waters

Chemical oxygen demand (COD)

Not exceed 15 mg/L at any time

Inland Waters in Shing Mun (B, F, G) subzones

Not exceed 30 mg/L at any time

Inland Waters in Shing Mun (A, C, D, E, H, I) subzones and other watercourses

5-day biochemical oxygen demand (BOD5)

Not exceed 3 mg/L at any time

Inland Waters in Shing Mun (B, F, G) subzones

Not exceed 5 mg/L at any time

Inland Waters in Shing Mun (A, C, D, E, H, I) subzones and other watercourses

Suspended solids (SS)

Not to cause the annual median level to exceed 20 mg/L.

Inland Waters in Shing Mun (A, B, C, F, G, H) subzones

Not to cause the annual median level to exceed 25 mg/L.

Inland Waters in Shing Mun (D, E, I) subzones and other watercourses

Settleable Material

Bottom deposits or submerged objects should not adversely influence bottom-living communities, alter the basic Harbour geometry or shipping channels, present any hazard to shipping or diving activities, or affect any other beneficial use of the waters.

Whole zone

Ammonia Nitrogen

Not to exceed 0.5 mg/L at any time

Inland Waters

E. coli Bacteria

Not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in one calendar year

Secondary Contact Recreation Subzone and Fish Culture Zone

Not exceed 1,000 per 100mL, calculated as a running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days (or 14 and 42 days)

Inland Waters in Shing Mun (A, C, D, E, H, I) subzones and other watercourses

Not exceed 0 per 100 mL, calculated as a running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days (or 14 and 42 days)

Inland Waters in Shing Mun (B, F, G) subzones

Chlorophyll-a

Not to cause the level of chlorophyll-a in waters of the subzone to exceed 20 mg/m3, calculated as a running arithmetic mean of 5 daily measurements for any single location and depth.

Marine Waters in Harbour Subzone

Not to cause the level of chlorophyll-a in waters of the subzone to exceed 10 mg/m3, calculated as a running arithmetic mean of 5 daily measurements for any single location and depth.

Marine Waters in Buffer Subzone

Not to cause the level of chlorophyll-a in waters of the subzone to exceed 6 mg/m3, calculated as a running arithmetic mean of 5 daily measurements for any single location and depth.

Marine Waters in Channel Subzone

Toxic substances

Should not attain such a level as to produce significant toxic effects in humans, fish or any other aquatic organisms.

Whole zone

Source: Statement of Water Quality Objectives (Tolo Harbour and Channel Water Control Zone).

 

5.2.3             Hong Kong Planning Standards and Guidelines

5.2.3.1        The Hong Kong Planning Standards and Guidelines (HKPSG), Chapter 9 (Environment), provides additional guidelines against water pollution for sensitive uses such as aquaculture and fisheries zones, bathing waters and other contact recreational waters.

5.2.4             Technical Memorandum on Effluent Discharge Standard

5.2.4.1        Besides setting the WQOs, the WPCO controls effluent discharging into the WCZs through a licensing system.  Guidance on the permissible effluent discharges based on the type of receiving waters (foul sewers, stormwater drains, inland and coastal waters) is provided in the Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS).  The limits given in the TM cover the physical, chemical and microbial quality of effluents.  Any effluent discharge during the construction and operational stages should comply with the relevant standards as stipulated in the TM-DSS.

5.2.5             Practice Note

5.2.5.1        The Practice Note (PN) for Professional Persons on Construction Site Drainage (ProPECC PN 1/94) issued by EPD provides good practice guidelines for dealing with various types of discharge from a construction site.  Practices outlined in the PN should be followed as far as possible during construction to minimise the water quality impact due to construction site drainage.

 

5.3                 Description of Environment

5.3.1             Baseline Condition

5.3.1.1        The Project site is located within Tolo Harbour and Channel WCZ.  Marine water quality monitoring data routinely collected by EPD were used to establish the baseline condition.  The closest EPD monitoring stations to the proposed SPS are TM6 and TM7 as shown in Figure 5.1.  According to the publication “Marine Water Quality in Hong Kong in 2019” issued by EPD, a summary of the EPD monitoring data collected at TM6 and TM7 in 2019 is presented in Table 5.2. 

 

Table 5.2       Summary Statistics of Marine Water Quality in Tolo Harbour and Channel WCZ (TM6 & TM7) in 2019

Parameters

TM6

(Buffer Subzone)

TM7

(Channel Subzone)

Temperature (°C)

24.6

24.6

 

(18.5 – 30.5)

(18.7 – 30.8)

Salinity (ppt)

31.5

31.5

 

(26.0 – 33.4)

(25.9 – 33.3)

Dissolved Oxygen (DO) (mg/L)

Depth-average

5.9

6.0

 

(3.8 – 8.4)

(5.0 – 8.0)

Bottom

4.8

5.3

 

(0.5 – 8.1)

(3.8 – 6.9)

Dissolved Oxygen (DO) (% Saturation)

Depth-average

85

86

 

(59 – 112)

(80 – 106)

Bottom

68

77

 

(8 – 108)

(62 – 91)

pH

8.0

8.1

 

(7.6 – 8.6)

(7.7 – 8.7)

Secchi disc Depth (m)

2.7

2.9

 

(2.0 – 3.7)

(2.0 – 3.6)

Turbidity (NTU)

2.5

2.9

 

(0.2 – 11.3)

(0.3 – 10.9)

Suspended Solids (SS) (mg/L)

4.9

5.5

 

(1.8 – 10.2)

(1.6 – 10.9)

5-day Biochemical Oxygen Demand (BOD5) (mg/L)

1.2

1.1

(0.9 – 1.8)

(0.6 – 1.8)

Ammonia Nitrogen (NH3-N) (mg/L)

0.027

0.027

 

(0.008 – 0.047)

(0.006 – 0.063)

Unionised Ammonia (UIA) (mg/L)

0.002

0.002

 

(<0.001 – 0.005)

(<0.001 – 0.007)

Nitrite Nitrogen (NO2-N) (mg/L)

0.005

0.004

(<0.002 – 0.012)

(<0.002 – 0.013)

Nitrate Nitrogen (NO3-N) (mg/L)

0.016

0.014

 

(<0.002 – 0.086)

(<0.002 – 0.086)

Total Inorganic Nitrogen (TIN) (mg/L)

0.05

0.05

 

(0.02 – 0.12)

(0.01 – 0.11)

Total Kjeldahl Nitrogen (mg/L)

0.37

0.34

 

(0.11 – 0.66)

(0.13 – 0.58)

Total Nitrogen (TN) (mg/L)

0.39

0.36

 

(0.15 – 0.67)

(0.15 – 0.58)

Orthophosphate Phosphorus (PO4-P) (mg/L)

0.006

0.006

(<0.002 – 0.018)

(<0.002 – 0.016)

Total Phosphorus (TP) (mg/L)

0.04

0.03

 

(<0.02 – 0.18)

(<0.02 – 0.13)

Silica (as SiO2) (mg/L)

0.85

0.83

 

(0.52 – 1.44)

(0.36 – 1.42)

Chlorophyll-a (µg/L)

4.3

4.3

 

(1.8 – 14.2)

(1.9 – 11.7)

E. coli (cfu/100 mL)

1

1

 

(<1 – 35)

(<1 – 1)

Faecal Coliforms (cfu/100 mL)

2

1

 

(<1 – 72)

(<1 – 3)

Notes:

cfu – colony forming unit

(1)        Except as specified, data presented are depth-averaged values calculated by taking the means of three depths: surface, mid-depth, bottom.

(2)        Data presented are annual arithmetic means results except for E.coli and faecal coliforms that are annual geometric means.

(3)        Data in brackets indicate the ranges.

 

5.3.2             Trend of Water Quality in Tolo Harbour and Channel

5.3.2.1        With the implementation of the Tolo Harbour Action Plan in the mid-80s, which includes control of livestock waste, the provision and improvement of sewerage, the export of treated sewage effluent from Sha Tin and Tai Po Sewage Treatment Works outside the Tolo Harbour discharging into the Victoria Harbour via the Kai Tak River and the extension of village sewerage in the catchment area, there has been a steady improvement in water quality in the Tolo Harbour in the past decade, including a decrease in the levels of BOD5, E. coli, TIN, NH3-N and PO4-P.  The long term data collected by EPD indicate decreasing trend of organic and nutrient levels in the Tolo Harbour and Channel WCZ.

5.3.2.2        The monitoring results of key water quality parameters, including DO and E. coli, indicated that the overall WQO compliance rate of the Tolo Harbour and Channel WCZ in 2019 was 79%, same as 2018.  The compliance rates for the DO objective was maintained at about 57%, same as 2017 and 2018. Furthermore, the Tolo Harbour and Channel WCZ also complied with the bacteriological WQO of ≤ 610 E. coli counts/100 mL (annual geometric mean) for the Secondary Contact Recreation Subzone.  Since Tolo Harbour is a shallow semi-enclosed water body with low water exchange rate with the Mirs Bay, the harbour’s essentially landlocked situation often leads to the natural stratification of the water column and lower bottom DO levels, particularly during the hot summer months, hence resulting in non-compliance with the DO objective.

5.3.3             Water Quality in Nearby Water Bodies

5.3.3.1        A water quality survey was conducted to collect field data of inland water bodies, namely D1-1 (inland watercourse near Nin Ming Road) and S1-1 (inland watercourse near Hong Kong Baptist Theological Seminary) and coastal marine water, namely T1-1, in the vicinity of the Project site.  Figure 5.2 shows the selected survey stations. 

5.3.3.2        The water quality survey was carried out for both dry season (from November 2016 to January 2017) and wet season (October 2016, April and May 2017) at the selected survey stations, and the results are presented in Table 5.3.  As no major developments that would change the pollution loading discharged into the inland water bodies were identified since the completion of the water quality survey by the time of submission of this EIA, the survey results are considered still valid.

Table 5.3  Summary of Baseline Water Quality Survey Results

Parameters

Dry Season (1)(2)(3)

Wet Season (1)(2)(3)

WQO for Tolo Harbour and Channel WCZ

D1-1

(Inland water)

S1-1

(Inland water)

T1-1

(Marine water)

D1-1

(Inland water)

S1-1

(Inland water)

T1-1

(Marine water)

In inland waters-Other Watercourses

In marine waters-Buffer Subzone

Water Depth (m)

0.12

0.29

0.5

0.13

0.29

0.6

NA

NA

(0.1 – 0.16)

(0.25 – 0.32)

(0.2 – 0.7)

(0.1 – 0.2)

(0.25 – 0.36)

(0.2 – 1)

Measurement Depth (m)

0.06

0.15

0.25

0.07

0.14

0.30

NA

NA

(0.05 – 0.08)

(0.125 – 0.16)

(0.1 – 0.35)

(0.05 – 0.1)

(0.125 – 0.18)

(0.1 – 0.5)

Water Temperature (oC)

23.63

(21.8 – 26.1)

24.83

(23.1 – 27.1)

24

(22 – 27)

24.90

(22.1 – 26.7)

26.07

(22.9 – 28)

26.67

(22 – 29)

Change due to waste discharge ≤±2.0oC at any location and time

Change due to waste discharge ≤±1.0 oC at any location and time; the changing rate ≤ 0.5 oC per hour at any location, unless due to natural phenomena

Salinity (ppt)

0.32

(0.25 – 0.4)

0.26

(0.24 – 0.29)

26.67

(23 – 29)

0.19

(0.12 – 0.28)

1.34

(0.21 – 3.27)

22.33

(10 – 30)

NA

Change due to waste discharge ≤±3 ppt at any time

pH

8.61

(8.47 – 8.79)

7.23

(7.14 – 7.38)

7.60

(7.4 – 7.9)

7.83

(7.5 – 8.1)

7.83

(7.2 – 8.2)

7.40

(7 – 7.8)

Not exceed the normal pH range of 6.0 – 9.0 at any time

Change due to waste discharge ≤±0.3 from natural range at any time

Conductivity (ms/cm)

0.60

0.53

41.00

0.40

2.52

37.67

NA

NA

(0.5 – 0.67)

(0.47 – 0.57)

(35 – 46)

(0.25 – 0.6)

(0.46 – 6)

(20 – 50)

Turbidity (NTU)

9.10

13.30

2.18

47.62

106.40

41.33

NA

NA

(7.9 – 11)

(2.9 – 34)

(0.65 – 3.9)

(0.85 – 130)

(3.2 – 300)

(2 – 110)

DO (%)

51.5

48.1

35

83.7

72.3

73

≥ 40% saturation at 15oC (3)

NA

(9.5 – 78)

(8.3 – 93)

(6 – 60)

(31 – 110)

(35 – 92)

(25 – 110)

DO (mg/L)

4.28

(0.83 – 6.4)

3.08

(0.73 – 4.9)

2.47

(0.5 – 4)

6.67

(2.8 – 8.6)

5.63

(2.6 – 7.3)

5.07

(1.9 – 7.2)

≥4 mg/L at any time

≥3 mg/L (within 2 m of the bottom); ≥4 mg/L (in the remainder of the water column)

Flow velocity (m/s)

0.47

(0.4 – 0.5)

0.20

(0.2 – 0.2)

NA

0.27

(0.2 – 0.4)

0.15

(0.1 – 0.2)

NA

NA

NA

Suspended Solids (SS) (mg/L)

12.67

15.87

10.60

12.33

4.33

14.33

Annual median ≤25 mg/L

NA

(10 – 17)

(4 – 38)

(6.8 – 18)

(4 – 27)

(2 – 8)

(1 – 26)

Biochemical Oxygen Demand (BOD5) (mg/L)

6

(5 – 7)

5

(3 – 6)

<1

(<1 – <1)

3

(<1 – 3)

6

(2 – 9)

4

(<1 – 6)

≤5 mg/L at any time

NA

Chemical Oxygen Demand (mg/L)

32

(27 – 36)

22

(13 – 37)

48

(10 – 82)

9

(3 – 13)

17

(10 – 31)

66

(11 – 150)

≤30 mg/L at any time

NA

Oil and Grease (mg/L)

1

1.5

1

1.5

1

1.5

NA

NA

(<1 – 1)

(<1 – 2)

(1 – 1)

(<1 – 1)

(<1 – 1)

(<1 – 2)

E.Coli (cfu/100mL)

2,867

(1,500 – 3,800)

243,333

(150,000 – 320,000)

1,557

(71 – 3,400)

4,067

(2,400 – 6,300)

8,820

(460 – 21,000)

2,793

(280 – 6,100)

≤1,000 cfu/100mL (running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days (or 14 and 42 days))

Annual geometric mean ≤610 cfu/100mL

Faecal Coliforms (cfu/100mL)

4,300

(2,600 – 5,600)

293,333

(160,000 – 400,000)

2,127

(82 – 4,500)

5,267

(3,000 – 7,200)

16,347

(640 – 42,000)

3,557

(370 – 6,900)

NA

NA

Ammonia Nitrogen (NH3-N) (mg/L)

3.70

(1.1 – 6.4)

4.90

(4.1 – 6.2)

0.80

(0.006 – 1.6)

1.23

(0.4 – 1.8)

4.53

(1.7 – 7.6)

1.00

(0.4 – 2.1)

≤ 0.5 mg/L at any time

NA

Nitrate-Nitrogen (NO3-N) (mg/L)

5.47

4.03

0.30

3.53

5.17

0.50

NA

NA

(3.5 – 7.5)

(2.3 – 7)

(0 – 0.8)

(2 – 4.8)

(0.9 – 7.8)

(0.2 – 0.8)

Total Kjeldahl Nitrogen (TKN) (mg/L)

4.37

(1 – 7.8)

5.37

(4.8 – 6.5)

1.50

(<0.05 – 1.9)

1.53

(0.1 – 2.6)

5.17

(2.3 – 8.4)

1.20

(0.7 – 2.2)

NA

NA

Ortho-phosphorus (PO4) (mg/L)

1.40

1.12

0.17

0.75

0.93

0.28

NA

NA

(1.3 – 1.6)

(0.66 – 1.4)

(<0.01 – 0.31)

(0.33 – 1.2)

(0.68 – 1.2)

(0.14 – 0.55)

Total Phosphorous (TP) (mg/L)

1.77

(1.6 – 2)

1.26

(0.77 – 1.5)

0.21

(<0.02 – 0.37)

0.87

(0.4 – 1.3)

1.40

(0.8 – 2.4)

0.35

(0.16 – 0.68)

NA

NA

Sulphide (S2- ) (mg/L)

<0.02

(<0.02 – <0.02)

<0.02

(<0.02 – <0.02)

<0.02

(<0.02 – <0.02)

<0.02

(<0.02 – <0.02)

<0.02

(<0.02 – <0.02)

<0.02

(<0.02 – <0.02)

NA

NA

Aluminum (Al) (µg/L)

41

28

44

11

<10

<10

NA

NA

(<10 – 42)

(12 – 41)

(<10 – 70)

(<10 – 11)

(<10 – <10)

(<10 – <10)

Cadmium (Cd) (µg/L)

0.10

<0.1

0.20

<0.1

<0.1

<0.1

NA

NA

(<0.1 – 0.1)

(<0.1 – <0.1)

(<0.1 – 0.3)

(<0.1 – <0.1)

(<0.1 – <0.1)

(<0.1 – <0.1)

Chromium (Cr) (µg/L)

<1

<1

<1

<1

<1

<1

NA

NA

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

Copper (Cu) (µg/L)

3.00

(2 – 4)

2.50

(<1 – 3)

<1

(2 – 30)

<1

(<1 – <1)

<1

(<1 – <1)

<1

(<1 – <1)

NA

NA

Zinc (Zn) (µg/L)

25.00

17.00

17.00

<10

<10

<10

NA

NA

(14 – 32)

(<10 – 17)

(<10 – 18)

(<10 – <10)

(<10 – <10)

(<10 – <10)

Lead (Pb) (µg/L)

<1

<1

<1

<1

<1

<1

NA

NA

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

(<1 – <1)

Notes:

NA – Not available

cfu – colony forming unit

(1)        Dry season water quality surveys were conducted on 15 Nov 2016,          14 Dec 2016 and 10 Jan 2017; while the wet season water quality surveys were conducted on 24 Oct 2016, 12 Apr 2017 and 12 May 2017.

(2)        Data presented are averaged values of three surveys’ results.  Data in brackets indicate the ranges.

(3)        The results which exceed WQO are bold and underlined. 

(4)        The WQO of DO saturation of inland waters cannot be compared with the measurement results because the measurements were not conducted at 15 oC. 

 

5.3.3.3        Comparing the survey results against the WQO, occasionally non-compliance of DO level was recorded at all monitoring stations in both dry and wet seasons, and the level was particularly low at Stations S1-1 and T1-1 during dry season.  At the survey stations for inland watercourses (D1-1 and S1-1), the levels of BOD5, COD and NH3-N were relatively high and exceeded the WQO for both seasons.  The levels of E. coli measured were also high, particularly at S1-1 during dry season, which indicated that these waterbodies could be contaminated by sewage discharges. 

 

5.4                 Water Sensitive Receivers

5.4.1.1        Water sensitive receivers (WSRs) within the 500 m assessment area and downstream of the emergency discharge were identified according to Annex 14 of the EIAO-TM.  The identified WSRs are listed below and their indicative locations are shown in Figure 5.2:

l   Inland watercourses

l   Mangroves along the coastlines of Tolo Harbour

l   Coastal Protection Area (CPA) at Nai Chung

Water Recreational Uses

5.4.1.2        The marine waters in Tolo Harbour and Channel WCZ is designated under the WPCO as secondary contact recreation subzone, which can be used for water sports and water recreational activities (e.g. dragon boating, sailing, rowing etc.).  The E. coli bacteria would be the principle parameter for assessing the acceptability of using the inland and marine water for water sports or secondary contact recreation activities with a WQO of not exceeding 610 cfu/100mL (calculated as the geometric mean of all samples collected in one calendar year).

 

5.5                 Assessment Methodology

5.5.1.1        The assessment area covers an area within 500 m of the Project site boundary, and all water sensitive receivers downstream of the emergency sewage overflow via the nearby stormwater drainage system into the Tolo Harbour.  The study area should be extended to include other areas if they are found also being impacted during the course of the EIA Report is being prepared and have a bearing on the environmental acceptability of the Project.

5.5.1.2        The WSRs that may be affected by the Project have been identified.  Water sampling and laboratory testing were conducted to quantify the water quality of the WSRs in the vicinity.  Potential sources of water quality impact that may arise during the construction and operational stages of the Project were described.  This task included identifying pollutants from point discharges and non-point sources that could affect the quality of surface water runoff.  All the identified sources of potential water quality impact were then evaluated and their impact significance determined.  The need for mitigation measures to reduce any identified adverse impacts on water quality to acceptable levels was determined. 

 

5.6                 Identification of Environmental Impacts

5.6.1             Construction Phase

5.6.1.1        Construction of the Project would only involve land-based construction works.  No marine works and alternation of any watercourses would be undertaken under the Project. 

5.6.1.2        Potential sources of water quality impact associated with the construction of the Project would be limited to land-based construction works as follows:

l   General construction activities;

l   Construction site runoff;

l   Accidental spillage of chemicals; and

l   Sewage effluent produced by on-site workforce.

5.6.1.3        The water quality impact generated from the Project would be localised and would be controlled with proper mitigation measures in place.

5.6.1.4        As detailed in Section 2, during the time of this EIA preparation, there is a concurrent project identified within the assessment area that would overlap with the Project construction, i.e. “Sai Sha Road Widening”.  For the proposed school with recreational area to the north of Nin Ming Road under the approved planning application no. A/MOS/125, as well as the Comprehensive Residential and Commercial Development east to Nai Chung under the approved planning application nos. A/NE-SSH/120 and A/NE-SSH/120-1, no confirmed construction programme is available at time of the preparation of this EIA.  Given that the Project is small in scale and localised and that the water quality impacts arising from the Project would be minimised with proper mitigation measures in place, no adverse cumulative water quality impact would be anticipated during construction phase.

5.6.2             Operational Phase

5.6.2.1        The normal operation of the proposed Sai O Trunk Sewer SPS would actually have beneficial effects through the provision of sewerage system for the areas.  However, potential water quality impact may arise from emergency overflow / bypass of sewage from the proposed SPS due to pumps / parts failure, power supply failure and damage to pressure main or flooding.  Under emergency, untreated sewage would be discharged from the SPS into the Tolo Harbour.  Nevertheless, with the incorporation of the precautionary measures (as described in Section 5.7.2) into the design, the chance of sewage bypass to nearby receiving waters would be extremely low.

5.6.2.2        The potential concurrent projects detailed in Section 2 fall within the sewerage catchment boundary of the proposed SPS and the designed capacity the SPS has already taken into account the need of catering the sewage flow generated from these planned developments.  As such, no adverse cumulative water quality impact would be anticipated during operational phase.

 

5.7                 Evaluation of Environmental Impacts

5.7.1             Construction Phase

General Construction Activities

5.7.1.1        Various types of construction activities may generate wastewater.  These include general cleaning and polishing, wheel washing, dust suppression and utility installation.  These types of wastewater would contain high concentrations of suspended solids (SS).  Various construction works may also generate debris and rubbish such as packaging, construction materials and refuse.  Uncontrolled discharge of site effluents, rubbish and refuse generated from the construction works could lead to deterioration in water quality.

5.7.1.2        On-site construction activities may cause water pollution from the following:

l   uncontrolled discharge of debris and rubbish such as packaging, construction materials and refuse; and

l   spillages of liquids stored on-site, such as oil, diesel and solvents etc., are likely to result in water quality impacts if they enter the nearby watercourse.

5.7.1.3        Effluent discharged from temporary site facilities should be controlled to prevent direct discharge to the neighbouring inland waters and storm drains.  Such effluent may include wastewater resulting from wheel washing of site vehicles at site entrances.  Debris and rubbish such as packaging, construction materials and refuse generated from the construction activities should also be properly managed and controlled to avoid accidental release to the local storm system and inland waters.  Adoption of the guidelines and good site practices for handling and disposal of construction discharges as specified in Section 5.8.2 would minimise the potential impacts.

5.7.1.4        Good construction and site management practices as stated in Section 5.8.1 should be observed to ensure that litter, fuels and solvents do not enter the nearby watercourse.

Construction Site Runoff

5.7.1.5        Potential pollution sources of site run-off may include:

l   Run-off and erosion of exposed bare soil and earth, drainage channel, earth working area and stockpiles;

l   Release of any bentonite slurries, concrete washings and other grouting materials with construction run-off or storm water;

l   Wash water from dust suppression sprays and wheel washing facilities; and

l   Fuel, oil and lubricants from maintenance of construction vehicles and equipment.

5.7.1.6        During rainstorms, site run-off would wash away the soil particles on unpaved lands and areas with the topsoil exposed.  The run-off is generally characterised by high concentrations of SS.  Release of uncontrolled site run-off would increase the SS levels and turbidity in the nearby water environment.  Site run-off may also wash away contaminated soil particles and therefore cause water pollution.

5.7.1.7        Wind-blown dust would be generated from exposed soil surfaces in the works areas.  It is possible that wind-blown dust would fall directly onto the nearby water bodies when a strong wind occurs.  Dispersion of dust within the works areas may increase the SS levels in surface run-off causing a potential impact to the nearby sensitive receivers.

5.7.1.8        Site runoff may arise from dewatering for foundation construction of the proposed Sai O Trunk Sewer SPS, regular water spraying of construction site as a dust suppression measure, cleaning and maintenance of vehicles and equipment, and erosion of excavated soil during rainstorms.  The runoff may contain high level of suspended solids, and contaminants such as fuel, oil and lubricants from powered mechanical equipment and vehicles.  Since the works area would be close to Tolo Harbour (approximately 15 m) and an inland watercourse (approximately 40 m), if not properly controlled, the contaminated site runoff may directly enter and thus pollute the nearby waterbodies and the stormwater drainage systems.  However, considering that the works area would be small in scale, the runoff could be well controlled by good site practises as per ProPECC PN1/94 “Construction Site Drainage”. 

5.7.1.9        Groundwater pumped out during dewatering for foundation construction of the proposed Sai O Trunk Sewer SPS should be passed through sand / silt removal facilities before being discharged to the local stormwater drains.

Accidental Spillage of Chemicals

5.7.1.10     The use of engine oil and lubricants, and their storage as waste materials has the potential to create impacts on the water quality if spillage occurs and enters adjacent water environment.  Waste oil may infiltrate into the surface soil layer, or run-off into the nearby water environment, increasing hydrocarbon levels.  The potential impacts could however be mitigated by practical mitigation measures and good site practices (as given in Section 6.5).

Sewage Effluent from Workforce

5.7.1.11     During the construction of the Project, the workforce on site will generate sewage effluents, which are characterised by high levels of BOD, ammonia and E. coli counts.  Potential water quality impacts upon the local drainage and fresh water system may arise from these sewage effluents, if uncontrolled.

5.7.1.12     Portable chemical toilets can be installed within the construction site, as far as practicable.  The Contractor will have the responsibility to ensure that chemical toilets are used and properly maintained, and that licensed contractors are employed to collect and dispose of the waste off-site at approved locations.  Therefore, adverse water quality impacts would not be expected.

Construction Works in Close Proximity of Inland Water

5.7.1.13     Construction activities in close vicinity to the inland watercourses may pollute the inland water bodies due to the potential release of construction wastes.  Construction wastes are generally characterised by high concentration of SS and elevated pH.  The implementation of measures to control runoff and drainage will be important for the construction works adjacent to the inland waters in order to prevent runoff and drainage water with high levels of SS from entering the water environment.  With the implementation of adequate construction site drainage as specified in the ProPECC PN 1/94 “Construction Site Drainage” and the provision of mitigation measures as described in the ETWB TC (Works) No. 5/2005 “Protection of natural streams / rivers from adverse impacts arising from construction works”, it is anticipated that unacceptable water quality impacts would not arise.

5.7.2             Operational Phase

Emergency Sewage Discharge

5.7.2.1        Under normal operation of the proposed Sai O Trunk Sewer SPS, no raw sewage would be discharged.  The potential for water quality impacts in the operational phase would be mainly associated with the possibility of sewage overflow from the SPS due to the events of pumps / parts failure, power supply failure, and damage to pressure main or flooding.  Under emergency, raw sewage from the proposed Sai O Trunk Sewer SPS would be discharged to Tolo Harbour.  The discharge of untreated sewage would cause an increase in the pollutant levels (particularly E. coli and TIN) of the receiving waters.

5.7.2.2        The emergency sewage overflow would be discharged via the nearby stormwater drainage system into the Tolo Harbour.  As shown in Figure 5.2, there is a mangrove site located in the vicinity of the Project site.  Past studies of mangroves concluded that the mangrove habitats are able to grow in areas of rich nutrient, low oxygen and high bacteria level and not adversely affected by high pollution loads (including concentrated sewage effluent)[1].  Therefore, it is considered that the temporary and minor increase of pollutants (especially TIN and E. coli) caused by the emergency discharge would not adversely affect the mangrove site. 

5.7.2.3        An assessment of untreated sewage discharge to Tolo Harbour was previously conducted under the approved EIA for “Tai Po Sewage Treatment Works– Stage V” (TPSTW).  The approved EIA for TPSTW assessed the water quality impact due to an emergency discharge of raw sewage from the TPSTW of 130,000 m3 per day for a duration of 24 hours.  Since the emergency discharge assessed in the EIA would also enter the Tolo Harbour similar to the emergency discharge arrangement of the proposed Sai O Trunk Sewer SPS, the findings of the approved EIA are considered applicable to this Project.  According to the approved EIA for TPSTW, the predicted recovery period for the impact due to emergency bypass of untreated effluent would be within a few days (about 3 days for E. coli and 5 days for TIN).  By assuming the emergency discharge of the Sai O Trunk Sewer SPS lasting for 24 hours as the worst-case scenario, a total of 20,600 m3 untreated sewage would be discharged from the SPS to Tolo Harbour.  Compared to that assessed in the approved EIA for TPSTW, the volume of raw sewage discharge from the proposed Sai O Trunk Sewer SPS under emergency is much smaller and therefore the time required for E. coli and TIN to return to the normal values is expected to be shorter.  In addition, with the precautionary measures as detailed in Section 5.7.2.5 to facilitate immediate actions to recover normal operation of the SPS in case of irregularities and to temporarily store sewage in case of complete plant failure, the emergency discharge from the proposed Sai O Trunk Sewer SPS would be much shorter than the assumed emergency period of 24 hours.

5.7.2.4        In view of the temporary nature of the emergency discharge and the potential water quality impact arising from overflow, if any, would be reversible, no long-term adverse impact on water quality would be expected from the emergency overflow from the proposed Sai O Trunk Sewer SPS.

5.7.2.5        Emergency discharge from the proposed Sai O Trunk Sewer SPS would be the consequence of interruption of the electrical power supply or pumps / parts failure.  In order to avoid emergency sewage discharge to the maximum practicable extent, the following precautionary measures will be incorporated into the design and operation of the proposed Sai O Trunk Sewer SPS to (i) safeguard the normal operation of the SPS, (ii) facilitate immediate actions to recover normal operation of the SPS in case of irregularities, and (iii) temporarily store sewage in case of complete power outage / plant failure.

(i)       Designs to safeguard the normal operation of the SPS

(a)     Secure Electrical Power Supply at SPS

l  Backup power supply in the form of dual-transformer and switchgear, and dual / ring circuit power supply by CLP Power Hong Kong Ltd. (CLP) will be provided to secure electrical power supply.  According to CLP’s performance standard and track records, their supply reliability reaches 99.99% and electricity provision will be restored within 2 hours after any unlikely fault outage.  The backup as mentioned above further enhanced the security and reliability.

(b)     Designs to Avoid / Minimise Equipment Failure

l   Two (2) duty and two (2) standby pumps will be provided to prevent interruption of normal operation of the SPS during breakdown or maintenance of the duty pumps;

l   Mechanically raked bar screen will be provided to remove large object, stones, debris, etc. and thus, protecting the downstream equipment of the SPS against physical damage.  One duty and one standby screen will be designed to secure the reliability and redundancy of the operation;

l   Provision of twin rising mains system to maintain normal operation of the proposed SPS during maintenance works by eliminating single point of failure and to minimise the chance of emergency overflow; and

l   Regular inspection and preventive maintenance of plant equipment to minimise equipment failure. 

(ii)      Design to facilitate immediate actions to recover normal operation of the SPS in case of irregularities

l   Provision of a telemetry system with alarms connecting the proposed Sai O Trunk Sewer SPS to Sha Tin Sewage Treatment Works (Sha Tin STW) to allow close monitoring of the operation of the unmanned SPS.  Alarm signal for any malfunction of SPS (such as power failure, abnormal shut down of pumps, etc.) will be sent to the control centre at Sha Tin STW so that immediate actions can be taken in case of irregularities or operation problems of the unmanned facilities.  Any failure would be promptly repaired by the operator / its contractor as soon as practicable in advance before sewage bypass to the emergency storage tank as detailed in Section 5.7.2.5(iii).

(iii)    Design and measure to temporarily store sewage in case of complete power outage / plant failure

l   Emergency storage tank, which would provide a holding capacity of approximately 1,717 m3 – equivalent to approximately 2 hours’ average dry weather flow (ADWF), will be provided for the proposed Sai O Trunk Sewer SPS to cater for failure of all pumps or complete outage of power supply. According to Section 5.5 of the Sewerage Manual – Pumping Stations and Rising Mains (Part 2) issued by DSD, temporary storage with capacity of at least 2 hours’ dry weather flow shall be provided if the provision of standby power is not feasible at a pumping station.  Although standby power would be provided at Sai O Trunk Sewer SPS as described in Section 5.7.2.5(i)(a), to further minimise the chance of emergency discharge, emergency storage of 2-hour daily sewage flow in total would still be provided and shall be sufficient to cater for sewage accumulated at the SPS in case of complete power outage / plant failure before restoration of normal operation.

o     In case of power outage, the temporary storage is sufficient to cater for the sewage accumulated at the SPS before restoration of power supply, which would take less than 2 hours in average according to CLP’s performance standard. 

o     In case of plant failure, the actual time for DSD staff action is more than the storage hours of the emergency storage tank with the provision of the abovementioned telemetry system as described in Section 5.7.2.5(ii) to alert operators for advance immediate action in case of any irregularities or operation problems of the Sai O Trunk Sewer SPS before complete plant failure and sewage starts accumulating.  Considering the distance between the location of the proposed SPS and both the existing / future relocated Sha Tin STW is less than 15 minutes driving distance, chance of DSD staff not being able to arrive at the proposed SPS site within 1-2 hrs is thin.  Such monitoring and action arrangement is same as the practice of the other existing SPSs in Ma On Shan / Wu Kai Sha areas (e.g. Ma On Shan and Ma On Shan 108 SPSs), and there has been no reported event of sewage bypass due to DSD staff not being able to arrive at the site on time to check the cause of malfunction of equipment and arrange tankering away of sewage (if necessary) so far as advised by DSD; this well proof the practicality of the current operation method.

l   If all the above measures to safeguard and recover normal operations of the SPSs as detailed in Section 5.7.2.5(i) and Section 5.7.2.5(ii) are exhausted, sewage will be tanked away as necessary as a last resort to maximise buffer for emergency storage as far as practicable in case the power outage / plant failure cannot be recovered in time to delay the outflow of raw sewage.  Sewage tankers would be mobilised within one hour since plant failure to tank away the sewage from the Sai O Trunk Sewer SPS as much as possible.

5.7.2.6        With the incorporation of the above precautionary measures, emergency discharge of sewage would be prevented to the maximum practicable extent and the potential impact would be short-term in the unlikely event that an emergency discharge does occur.

5.7.2.7        In order to minimise the potential water quality impact in case of emergency overflow, a contingency plan should be implemented as described in Section 5.8.2 to deal with the remote occurrence of emergency discharge.

Surface Runoff

5.7.2.8        Surface runoff would be anticipated during rain since the Project site would be paved and impervious.  The runoff would enter the stormwater drainage system in the vicinity of the Project site.  During the operation of the SPS, there would be no exposed polluting source at the SPS as the SPS system would be fully enclosed.  Therefore, the surface runoff would not be polluted by the operation of the Project and would be suitable to be discharged directly into the stormwater drainage system.  No adverse impact is anticipated from the surface runoff from the Project site during the operational period.

 

5.8                 Mitigation Measures

5.8.1             Construction Phase

Construction Site Runoff

5.8.1.1        Proper site management measures should be implemented to control site runoff and drainage, and thereby prevent high sediment loadings from entering nearby watercourses.  The Contractor should follow the practices, and be responsible for the design, construction, operation and maintenance of all the mitigation measures as specified in ProPECC PN 1/94 “Construction Site Drainage”.  The design of the mitigation measures should be submitted by the Contractor to the engineer for approval.  These mitigation measures should include the following practices to minimise site surface runoff and the chance of erosion, and to retain and reduce any suspended solids prior to discharge:

l   At the start of site establishment, perimeter cut-off drains to direct off-site water around the site should be constructed with internal drainage works and erosion and sedimentation control facilities implemented.  Channels (both temporary and permanent drainage pipes and culverts), earth bunds or sand bag barriers should be provided on site to direct storm water to silt removal facilities.  The design of the temporary on-site drainage system will be undertaken by the Contractor prior to the commencement of construction.

l   Sand / silt removal facilities such as sand / silt traps and sediment basins should be provided to remove sand / silt particles from runoff to meet the requirements of the Technical Memorandum standard under the Water Pollution Control Ordinance.  The design of efficient silt removal facilities should be based on the guidelines in Appendix A1 of ProPECC PN 1/94, which states that the retention time for silt / sand traps should be 5 minutes under maximum flow conditions.  The detailed design of the sand / silt traps shall be undertaken by the Contractor prior to the commencement of construction.

l   All drainage facilities and erosion and sediment control structures should always be regularly inspected and maintained to ensure proper and efficient operation and particularly during rainstorms.  Deposited silt and grit should be regularly removed, at the onset of and after each rainstorm to ensure that these facilities are functioning properly at all times.

l   Measures should be taken to minimise the ingress of site drainage into excavations.  Water pumped out from foundation excavations should be discharged into storm drains via silt removal facilities.

l   If surface excavation works cannot be avoided during the wet season (April to October), temporarily exposed slope / soil surfaces should be covered by a tarpaulin or other means, as far as practicable, and temporary access roads should be protected by crushed stone or gravel, as excavation proceeds.  Interception channels should be provided (e.g.  along the crest / edge of the excavation) to prevent storm runoff from washing across exposed soil surfaces.  Arrangements should always be in place to ensure that adequate surface protection measures can be safely carried out well before the arrival of a rainstorm.  Other measures that need to be implemented before, during and after rainstorms are summarised in ProPECC PN 1/94.

l   All vehicles and plant should be cleaned before leaving a construction site to ensure no earth, mud, debris and the like is deposited by them on roads.  An adequately designed and sited wheel washing facility should be provided at every construction site exit where practicable.  Wash-water should have sand and silt settled out and removed at least on a weekly basis to ensure the continued efficiency of the process.  The section of access road leading to, and exiting from, the wheel-wash bay to the public road should be paved with sufficient backfall toward the wheel-wash bay to prevent vehicle tracking of soil and silty water to public roads and drains.

l   Open stockpiles of construction materials or construction wastes on-site should be covered with tarpaulin or similar fabric during rainstorms.

General Construction Activities

5.8.1.2        Debris and refuse generated on-site should be collected, handled and disposed of properly to avoid entering any nearby water bodies and public drainage system.  Stockpiles of cement and other construction materials should be kept covered when not being used.

5.8.1.3        Oils and fuels should only be used and stored in designated areas, which have pollution prevention facilities.  To prevent spillage of fuels and solvents to any nearby storm water drain or watercourse, all fuel tanks and storage areas should be provided with locks and be sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank.  Rainwater in the bunds should be cleared after each rain event.  Waste oils, fuels and solvents collected within the bund should be handled and treated as chemical waste as detailed in Section 6.

Sewage Effluent

5.8.1.4        Temporary sanitary facilities, such as portable chemical toilets, should be employed on-site where necessary to handle sewage from the workforce.  A licensed contractor would be responsible for appropriate disposal of waste matter and maintenance of these facilities.

Construction Works in Close Proximity of Inland Waters

5.8.1.5        The practices outlined in ETWB TC (Works) No. 5/2005 “Protection of Natural Streams / Rivers from Adverse Impacts arising from Construction Works” should also be adopted where applicable to minimise the water quality impacts upon any natural streams or surface water systems.  Relevant mitigation measures from the ETWB TC (Works) No. 5/2005 are listed below:

l   Construction works close to the inland waters should be carried out in dry season as far as practicable where the flow in the surface channel or stream is low.

l   The use of less or smaller construction plants may be specified in areas close to the water courses to reduce the disturbance to the surface water.

l   Temporary storage of materials (e.g. equipment, chemicals and fuel) and temporary stockpile of construction materials should be located well away from any watercourses during carrying out of the construction works.

l   Stockpiling of construction materials and dusty materials should be covered and located away from any watercourses.

l   Construction debris and spoil should be covered up and / or disposed of as soon as possible to avoid being washed into the nearby water receivers.

l   Proper shoring may need to be erected in order to prevent soil or mud from slipping into the watercourses.

5.8.2             Operational Phase

Emergency Sewage Discharge

5.8.2.1        Emergency discharges from the Project would be the consequence of pumps / parts failure and interruption of the electrical power supply.  With the incorporation of the preventive measures (as described in Sections 5.7.2.5) into the design and operation of the proposed Sai O Trunk Sewer SPS to safeguard the normal operation of the SPS, facilitate immediate actions to recover normal operation of the SPS in case of irregularities, and temporarily store sewage in case of complete power outage / plant failure, the possibility of emergency sewage discharge would be avoided to the maximum practicable extent. 

5.8.2.2        Any incident of emergency bypass from the SPS would follow EPD’s “A Guide on Reporting Sewage Bypass Incidents in Sewage Pumping Stations and Sewers” and DSD’s “Contingency Plan for Incidents Possibly Encountered in Sewage Treatment Facilities having a Potential of Generating an Environmental Nuisance” (hereinafter referred to as “Contingency Plan”).  The Contingency Plan as enclosed in Appendix 5.1 details the procedures to promptly notify relevant Government Departments (e.g. Environmental Protection Department (EPD)] in the event of emergency overflow that may pollute water sensitive receivers close to the proposed SPS or cause other environmental nuisance as soon as possible within 24 hours of the incident and to conduct joint investigation with EPD to assess the impacts as well as to work out mitigation measures to reduce impact to the environment and public health and to interact with the community if necessary.

Surface Runoff

5.8.2.3        Although no adverse impact is anticipated from the operational phase surface runoff, Best Management Practices (BMPs), e.g.  good housekeeping practices should be implemented in order to ensure that the operation of the SPS would not pollute the runoff.

 

5.9                 Residual Environmental Impacts

5.9.1.1        With the full implementation of the recommended mitigation measures for the construction and operational phases of the Project, no unacceptable residual impacts on water quality would be anticipated. 

 

5.10              Environmental Monitoring and Audit

5.10.1.1     It is recommended that regular audits of the implementation of the recommended mitigation measures at all work areas be carried out during construction phase.  Aside from the regular auditing of the implementation of the recommended mitigation measures, a specific water quality monitoring programme is deemed unnecessary.

 

5.11              Conclusion

5.11.1.1     Key concerns of water quality issues were mainly related to the potential of construction run-off during construction phase and emergency sewage overflow / bypass from the SPS during the operational phase.  With incorporation of the precautionary design of the SPS, proper implementation of the proposed mitigation measures and good site practices, adverse water quality impact would not be expected during the construction and operational phases. 


 

 


[1] Tam, N.F.Y, Li, S.H., Lan, C.Y., Chen, G.Z., Li, M.S.  and Wong, Y.S. 1995. Nutrients and heavy metal contamination of plants and sediments in Futien mangrove forest.  Hydrobiologia, 295: pp149-158.

  Tam, N.F.Y. and Wong, Y.S. 1995. Mangrove soils as sinks for wastewater-borne pollutants. Hydrobiologia, 295: pp231-241.

  Tam, N.F.Y. and Wong, Y.S. 1997. Ecological Study on Mangrove Stands in Hong Kong – Volumes I and V. Agriculture & Fisheries Department.

   Wong, Y.S., Lan, C.Y., Chen, G.Z., Li, S.H., Chen, X.R.  Liu, Z.P.  and Tam, N.F.Y. 1995. Effect of wastewater discharge on nutrient contamination of mangrove soils and plants. Hydrobiologia, 295: pp243-254.

   Wong, Y.S., Chen, G.Z., Ma, H.  and Tam, N.F.Y. Tolerance of Aegiceras corniculatum plants to synthetic sewage of different strength. Asia Pacific Conference on Science and Management of the Coastal Environment, 25-28 June 1996. Programme & Abstracts: pp279.

   Wong, Y.S., Tam, N.F.Y., Lan, C.Y.  and Chen, N.C. Mangrove wetland ecosystems for wastewater treatment: – Fieldwork and tide-tank experiments. Asia Pacific Conference on Science and Management of the Coastal Environment, 25-28 June 1996. Programme & Abstracts: pp76-77.