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Advisory Council on the Environment

Declaration of the North Western Supplementary Water Control Zone and the Second Southern Supplementary Water Control Zone

(ACE Paper 23/99)
for advice

Introduction

This paper seeks Members' advice on the proposal for declaring the North Western Supplementary Water Control Zone (NWSWCZ) and the Second Southern Supplementary Water Control Zone (SSSWCZ), and to establish Water Quality Objectives (WQOs) for these two Water Control Zones (WCZs).

Background

2.After the return of sovereignty in July 1997, the legal boundary of the Hong Kong Special Administration Region (HKSAR) has changed1. As a result of the changes in HKSAR's boundary, three new areas of waters, shown as Areas A, B and C in Annex A for the purpose of this paper, have become part of HKSAR'. These extended areas of waters are currently not covered by any existing WCZs.

3.To extend the WPCO to the aforementioned extended areas, it is proposed that new WCZs be declared to cover them.

4.In order to safeguard public health and prevent the deterioration of water quality, the Water Pollution Control Ordinance (WPCO), Cap. 358, was enacted in 1980 and brought into effect in April 1981 to implement controls on wastewater discharges. An important means of control under the WPCO is the provision for the declaration of WCZs and the establishment of WQOs for each WCZ. Discharges of effluents within WCZs are subjected to Environmental Protection Department's (EPD) licensing control.

5.Under section 4 of the WPCO, the Chief Executive (CE) in Council may, by order published in the gazette, declare any part of Hong Kong to be a WCZ, after consultation with the Advisory Council on the Environment (ACE). Under section 5 of the WPCO, the Secretary for Planning, Environment and Lands (SPEL) may, after consultation with ACE, establish WQOs for each WCZ. To bring a WCZ into effect, CE in Council has to make an order under section 7(2) and 7(3) of the WPCO, to be published in the gazette, to declare the effective dates for the control of discharge to commence. Two effective dates will be made for each WCZ, namely the First Appointed Day (FAD) and the Second Appointed Day (SAD). Any new discharge which commences after the FAD will have to obtain a licence from EPD before discharge is permitted. Discharges which have already existed before the FAD can continue after the FAD but have to obtain a licence from EPD before the SAD.

6.The following WCZs have been declared before 1 July 1997 to cover the then whole of Hong Kong, after consultation with the then Environmental Pollution Advisory Committee and this Council:

WCZs Dates of gazetting
Tolo Harbour and Channel 26-Feb-82
Southern 29-Jul-88
Port Shelter 28-Jul-89
Junk Bay 28-Jul-89
Mirs Bay 30-Nov-90
Deep Bay 30-Nov-90
North Western 28-Feb-92
Western Buffer 28-May-93
Eastern Buffer 28-May-93
Tolo Harbour Supplementary 28-May-93
Southern Supplementary 28-May-93
Victoria Harbour (Phase One) 7-Oct-94
Victoria Harbour (Phase Two) 28-Jul-95
Victoria Harbour (Phase Three) 16-Feb-96

Proposed NWSWCZ

7.As Area A is geographically adjacent to the existing North Western Water Control Zone (NWWCZ), the general environmental characteristics and beneficial uses of their water bodies are similar. It is therefore proposed that Area A be declared as the "North Western Supplementary Water Control Zone" (NWSWCZ), with a set of WQOs identical to that of the NWWCZ.

8.The boundaries and WQOs of the proposed NWSWCZ are at Annexes B and C respectively.

Proposed SSSWCZ

9.Likewise, it is proposed that Areas B and C, which are geographically adjacent to the existing Southern Water Control Zone (SWCZ), be declared as the "Second Southern Supplementary Water Control Zone" (SSSWCZ), with a set of WQOs identical to that of the SWCZ.

10.The boundaries and WQOs of the proposed SSSWCZ are at Annexes D and E respectively.

Scope of Control

11.As with existing WCZs, all types of discharges from residential, industrial, commercial and institutional establishments within the proposed NWSWCZ and SSSWCZ will be controlled, except the following :

(a)
domestic sewage which are connected to the communal foul sewers; or
(b)
unpolluted water which is discharged into stormwater drains, river courses and water bodies.

Implementation

12.To enable water pollution control measures for the two new WCZs to be implemented over a reasonable time scale, it is proposed that, for both NWSWCZ and SSSWCZ, the FAD be on 1 October 1999 and the SAD be on 1 December 1999.

Environmental Implications

13.The proposed declaration of NWSWCZ and SSSWCZ will enable the extended areas of the HKSAR be subjected to water pollution control already implemented for the remaining parts of HKSAR.

Public Consultation

14.The Islands Provisional District Board was consulted on the proposals on 3 May 1999. No objection was raised.

Advice Sought

15.Members are requested to endorse the proposals for:

(a)
declaring the NWSWCZ and SSSWCZ by order of the CE in Council under section 4 of the WPCO, with FAD on 1 October 1999 and SAD on 1 December 1999; and
(b)
establishing the WQOs for NWSWCZ and SSSWCZ by SPEL under section 5 of the WPCO.

 

Planning, Environment and Lands Bureau
Environmental Protection Bureau
June 1999

Annex C
(page 1)

North Western Supplementary Water Control Zone

Water Quality Objectives

 

  Water Quality Objectives  Part or parts of Zone
A. AESTHETIC APPEARANCE  
       
  (a) Waste discharges shall cause no objectionable odours or discolouration of the water. Whole zone
       
  (b) Tarry residues, floating wood, articles made of glass, plastic, rubber or of any other substances should be absent. Whole zone
       
  (c) Mineral oil should not be visible on the surface. Surfactants should not give rise to a lasting foam. Whole zone
       
  (d) There should be no recognisable sewage-derived debris. Whole zone
       
  (e) Floating, submerged and semi-submerged objects of a size likely to interfere with the free movement of vessels, or cause damage to vessels, should be absent. Whole zone
       
  (f) Waste dischargers shall not cause the water to contain substances which settle to form objectionable deposits. Whole zone
       
B. BACTERIA  
       
  The level of Escherichia coli should not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year. Secondary Contact Recreation Subzones
       
C. DISSOLVED OXYGEN  
       
  Waste discharges shall not cause the level of dissolved oxygen to fall below 4 mg per litre for 90% of the sampling occasions during the whole year; values should be calculated as water column average (arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed). In addition, the concentration of dissolved oxygen should not be less than 2 mg per litre within 2 m of the seabed for 90% of the sampling occasions during the whole year. Marine waters
       
D. pH  
       
  The pH of the water should be within the range of 6.5-8.5 units. In addition, waste discharges shall not cause the natural pH range to be extended by more than 0.2 unit. Marine waters
       
E. TEMPERATURE  
       
  Waste discharges shall not cause the natural daily temperature range to change by more than 2.0oC. Whole zone
       
F. SALINITY  
       
  Waste discharges shall not cause the natural ambient salinity level to change by more than 10%. Whole zone
       
G. SUSPENDED SOLIDS  
       
  Waste discharges shall neither cause the natural ambient level to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities. Marine waters
       
H. AMMONIA  
       
  The un-ionized ammoniacal nitrogen level should not be more than 0.021 mg per litre, calculated as the annual average (arithmetic mean). Whole zone
       
I. NUTRIENTS  
       
  (a) Nutrients shall not be present in quantities sufficient to cause excessive or nuisance growth of algae or other aquatic plants. Marine waters
       
  (b) Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.5 mg per litre, expressed as annual water column average (arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed). Marine waters
       
J. TOXINS  
       
  (a) Waste discharges shall not cause the toxins in water to attain such levels as to produce significant toxic, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to toxicant interactions with each other. Whole zone
       
  (b) Waste discharges shall not cause a risk to any beneficial use of the aquatic environment. Whole zone

 

Annex E
(page 1)

Second Southern Supplementary Water Control Zone

Water Quality Objectives

 

  Water Quality Objectives   Part or parts of Zone
A. AESTHETIC APPEARANCE   
       
  (a) Waste discharges shall cause no objectionable odours or discolouration of the water. Whole zone
       
  (b) Tarry residues, floating wood, articles made of glass, plastic, rubber or of any other substances should be absent. Whole zone
       
  (c) Mineral oil should not be visible on the surface. Surfactants should not give rise to a lasting foam. Whole zone
       
  (d) There should be no recognisable sewage-derived debris. Whole zone
       
  (e) Floating, submerged and semi-submerged objects of a size likely to interfere with the free movement of vessels, or cause damage to vessels, should be absent. Whole zone
       
  (f) Waste dischargers shall not cause the water to contain substances which settle to form objectionable deposits. Whole zone
       
B. BACTERIA   
       
  The level of Escherichia coli should not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in a calendar year.  Secondary Contact Recreation Subzones
       
C. DISSOLVED OXYGEN   
       
  Waste discharges shall not cause the level of dissolved oxygen to fall below 4 mg per litre for 90% of the sampling occasions during the year; values should be calculated as the water column average (arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed). In addition, the concentration of dissolved oxygen should not be less than 2 mg per litre within 2 m of the seabed for 90% of the sampling occasions during the whole year.  Marine waters
       
D. pH  
  The pH of the water should be within the range of 6.5-8.5 units. In addition, waste discharges shall not cause the natural pH range to be extended by more than 0.2 unit.  Marine waters
       
E. TEMPERATURE  
       
  Waste discharges shall not cause the natural daily temperature range to change by more than 2.0oC.  Whole zone
       
F. SALINITY  
       
  Waste discharges shall not cause the natural ambient salinity level to change by more than 10%.  Whole zone
       
G. SUSPENDED SOLIDS   
       
  Waste discharges shall neither cause the natural ambient level to be raised by more than 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.  Marine waters
       
H. AMMONIA   
       
  The ammonia nitrogen level should not be more than 0.021 mg per litre, calculated as the annual average (arithmetic mean), as unionised form.  Whole zone
       
I. NUTRIENTS   
       
  (a) Nutrients shall not be present in quantities sufficient to cause excessive or nuisance growth of algae or other aquatic plants. Marine waters
       
  (b) Without limiting the generality of objective (a) above, the level of inorganic nitrogen should not exceed 0.1 mg per litre, expressed as annual water column average (arithmetic mean of at least 3 measurements at 1 m below surface, mid-depth and 1 m above seabed). Marine waters
       
J. DANGEROUS SUBSTANCES  
       
  (a) Waste discharges shall not cause the concentrations of dangerous substances in marine waters to attain such levels as to produce significant toxic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to toxicant interactions with each other. Whole zone
       
  (b) Waste discharges of dangerous substances shall not put a risk to any beneficial uses of the aquatic environment. Whole zone


1 The legal boundary of the HKSAR has changed, following the description in the Order of the State Council of the People's Republic of China No. 221 of 1 July 1997. The revised legal boundary, as stipulated in the various Schedules to the Interpretation and General Clauses Ordinance, Cap. 1, took effect on 1 July 1997, through the enactment of the Adaptation of Laws (Interpretative Provisions) Ordinance.

 

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