Cap. 358O 《牛尾海水質管制區水質指標》Port Shelter Water Control Zone Statement of Water Quality Objectives

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版本日期: 2024-08-18

Port Shelter Water Control Zone Statement of Water Quality Objectives

[28 July 1989]

(Format changes—E.R. 6 of 2019)

The water quality objectives set out in the first column of Schedule 1 have been established for those parts of the Port Shelter Water Control Zone defined in Schedule 2 set opposite those water quality objectives in the second column of Schedule 1.

Schedule 1


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 substance 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 discharges shall not cause the water to contain substances which settle to form objectionable deposits.		Whole Zone

B.	BACTERIA
	(a)The level of Escherichia coli should not exceed 610 per 100 mL, calculated as the geometric mean of all samples collected in one calendar year.		Secondary Contact Recreation Subzones and Fish Culture Subzones
	(b)The level of Escherichia coli should not exceed 180 per 100 mL, calculated as the geometric mean of all samples collected from March to October inclusive in one calendar year. Samples should be taken at least 3 times in a calendar month at intervals of between 3 and 14 days.		Bathing Beach Subzones
		(L.N. 452 of 1991)

C.	COLOUR
	Waste discharges shall not cause the colour of water to exceed 50 Hazen units.		Inland waters


D.	DISSOLVED OXYGEN
	(a)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 year.		Marine waters excepting Fish Culture Subzones
	(b)The dissolved oxygen level should not be less than 5 mg per litre for 90% of the sampling occasions during the 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 year.		Fish Culture Subzones
	(c)Waste discharges shall not cause the level of dissolved oxygen to be less than 4 mg per litre.		Inland waters

E.	pH
	(a)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 units.		Marine waters excepting Bathing Beach Subzones
	(b)The pH of the water should be within the range of 6.0–9.0 units for 95% of samples. In addition, waste discharges shall not cause the natural pH range to be extended by more than 0.5 units.		Bathing Beach Subzones
	(c)Waste discharges shall not cause the pH of the water to exceed the range of 6.5–8.5 units.		Ho Chung (A) Subzone
	(d)The pH of the water should be within the range of 6.0–9.0 units.		Other inland waters

F.	TEMPERATURE
	Waste discharges shall not cause the natural daily temperature range to change by more than 2.0℃.		Whole Zone

G.	SALINITY
	Waste discharges shall not cause the natural ambient salinity level to change by more than 10%.		Whole Zone

H.	SUSPENDED SOLIDS
	(a)Waste discharges shall neither cause the natural ambient level to be raised by 30% nor give rise to accumulation of suspended solids which may adversely affect aquatic communities.		Marine waters
	(b)Waste discharges shall not cause the annual median of suspended solids to exceed 25 mg per litre.		Inland waters

I.	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

J.	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

K.	5-DAY BIOCHEMICAL OXYGEN DEMAND
	Waste discharges shall not cause the 5-day biochemical oxygen demand to exceed 5 mg per litre.		Inland waters

L.	CHEMICAL OXYGEN DEMAND
	Waste discharges shall not cause the chemical oxygen demand to exceed 30 mg per litre.		Inland waters

M.	DANGEROUS SUBSTANCES
	(a)Waste discharges shall not cause the concentration of dangerous substances in the water 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 designated beneficial uses of the aquatic environment.		Whole Zone

N.	PHENOL
	Phenols shall not be present in such quantities as to produce a specific odour, or in concentrations greater than 0.05 mg per litre as C₆H₅OH.		Bathing Beach Subzones

O.	TURBIDITY
	No changes in turbidity or other factors arising from waste discharges shall reduce light transmission substantially from the normal level.		Bathing Beach Subzones

Schedule 2

In this Statement— (E.R. 6 of 2019)

bathing beach subzone (泳灘分區) means a bathing beach that is specified in the Fourth Schedule to the Public Health and Municipal Services Ordinance (Cap. 132) and situated in the Port Shelter Water Control Zone; fish culture subzone (魚類養殖分區) means a fish culture zone that is designated in the Fish Culture Zone (Designation) Order (Cap. 353 sub. leg. B) and situated in the Port Shelter Water Control Zone; (E.R. 6 of 2019) Ho Chung (A) subzone (蠔涌(A)分區) means that part of the catchment of the Ho Chung River delineated on the Map and which delineated part is marked HC(A); Map (地圖) means a 1:25 000 map marked PSWCZ signed by the Secretary for Lands and Works, Lands and Works Branch, on 6 July 1989 and deposited in the Land Registry; (8 of 1993 s. 30; 21 of 2024 s. 78) marine waters (海洋水域) means the waters within the Port Shelter Water Control Zone boundary below the high water mark; Secondary Contact Recreation Subzone (次級接觸康樂分區) means an area delineated as such on the Map, except where the area is designated as a bathing beach subzone or a fish culture subzone.