Junk Bay Water Control Zone Statement of Water Quality Objectives
[28 July 1989]
(Format changes—E.R. 5 of 2024)
The water quality objectives set out in the first column of Schedule 1 have been established for those parts of the Junk Bay Water Control Zone defined in Schedule 2 set opposite those water quality objectives in the second column of Schedule 1.
| 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 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 recognizable 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 Subzone and Fish Culture Subzones (L.N. 451 of 1991) | ||
| (b) | (Repealed L.N. 451 of 1991) | |||
| (c) | The level of Escherichia coli should not exceed 1 000 per 100 mL, calculated as the running median of the most recent 5 consecutive samples taken at intervals of between 7 and 21 days. (E.R. 5 of 2024) | Inland waters | ||
| 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 (L.N. 451 of 1991) | ||
| (b) | (Repealed L.N. 451 of 1991) | |||
| (c) | The pH of the water should be within the range of 6.0-9.0 units. | Inland waters | ||
| F. | TEMPERATURE | |||
| Waste discharges shall not cause the natural daily temperature range to change by more than 2.0°C. | 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 unionized 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 0.3 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 concentrations 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 beneficial uses of the aquatic environment. | Whole Zone | ||
| N-O. | (Repealed L.N. 451 of 1991) | |||
In this Statement— (E.R. 5 of 2024)
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 Junk Bay Water Control Zone; (E.R. 5 of 2024) Map (地圖) means a 1:20 000 map marked JBWCZ 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 Junk Bay Water Control Zone boundary below the high water mark; Secondary Contact Recreation Subzone (次級接觸康樂活動分區) 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.