SOUTHERN WATER CONTROL ZONE STATEMENT OF WATER QUALITY OBJECTIVES

SOUTHERN WATER CONTROL ZONE STATEMENT OF WATER QUALITY OBJECTIVES

SOUTHERN WATER CONTROL ZONE STATEMENT
WATER QUALITY OBJECTIVES

(Cap. 358, section 5)

[29 July 198]1

L.N. 211/88

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

SCHEDULE 1

Water Quality Objective Part or parts of Zone

A. AESTHETIC APPEARANCE

(a) Waste discharges shall cause no objectionable Whole Zone
odours or discolouration of the water.
(b) Tarry residues, floating wood, articles made of Whole Zone
glass, plastic, rubber or of any other substance
should be absent.
(c) Mineral oil should not be visible on the surface. Whole Zone
Surfactants should not give rise to a lasting
foam.
(d) There should he no recognisable sewage-derived Whole Zone
debris.
(e) Floating, submerged and semi-submerged Whole Zone
objects of a size likely to interfere with the free
movement of vessels, or cause damage to vessels,
should be absent.
(f) Waste discharges shall not cause the water to Whole Zone
contain substances which settle to form
objectionable deposits.
B. BACTERIA
(a) Waste discharges shall not cause the level of Secondary Contact Recreation
Escherichia coli to exceed 1000 per 100 mI, in Subzones
more than 60% of the samples collected during
the whole year.
(b) The level of Escherichia coli should not exceed Bathing Beach Subzones
1000 per 100 mI, calculated as the running
median of the most recent 5 consecutive samples.
Samples should be taken 3 times in one calendar
month at intervals of between 3 and 14 days.
The sampling programme extends from March
to October inclusive in any year.
C. DISSOLVED OXYGEN
(a) Waste discharges shall not cause the level of Marine waters excepting
dissolved oxygen to fall below 4 milligrams per Fish Culture Subzones
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





Water Quality Objective Part or parts of Zone

measurements at 1 metre below surface,
middepth, and 1 metre above seabed). In
addition, the concentration of dissolved oxygen
should not be less than 2 milligrams per litre
within 2 metres of the seabed for 90% of the
sampling occasions during the year.

(b) The dissolved oxygen level should not be less Fish Culture Subzones
than 5 milligrams 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
metre below surface, mid-depth and 1 metre
above seabed). In addition, the concentration of
dissolved oxygen should not be less than 2 milli-
grams per litre within 2 metres of the seabed for
90% of the sampling occasions during the year.
(c) Waste discharges shall not cause the level of Inland waters of the Zone
dissolved oxygen to be less than 4 milligrams per
litre.
D. pH
(a) The pH of the water should be within the range Marine waters excepting Bathing
of 63-8.5 units. In addition, waste discharges Beach Subzones; Mui Wo (A),
shall not cause the natural pH range to be Mui Wo (B), Mui Wo (C), Mui
extended by more than 0.2 units. Wo (E) and Mui Wo (F)
Subzones.
(b) The pH of the water should be within the range Mui Wo (D) Subzone and other
of 6.0-9.0 units. inland waters.
(c) The pH of the water should be within the range Bathing Beach Subzones
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.
E. TEMPERATURE
Waste discharges shall not cause the natural daily Whole Zone
temperature range to change by more than 2.0
degrees Celsius.
F. SALINITY
Waste discharges shall not cause the natural ambient Whole Zone
salinity level to change by more than 10%.
G. SUSPENDED SOLIDS
(a) Waste discharges shall neither cause the natural Marine waters
ambient level to be raised by 30% nor give rise
to accumulation of suspended solids which may
adversely affect aquatic communities.
(b) Waste discharges shall not cause the annual Mui Wo (A), Mui Wo (B), Mui
median of suspended solids to exceed 20 Wo (C), Mui Wo (E) and Mui Wo
milligrams per litre. (F) Subzones.
(c) Waste discharges shall not cause the annual Mui Wo (D) Subzone and other
median of suspended solids to exceed 25 inland waters.
milligrams per litre.
H. AMMONIA
The ammonia nitrogen level should not be more than Whole Zone
0.021 milligram per litre, calculated as the annual
average (arithmetic mean), as unionised form.





Water Quality Objective Part or parts of Zone

1. NUTRIENTS

(a) Nutrients shall not be present in quantities Marine waters
sufficient to cause excessive or nuisance growth
of algae or other aquatic plants.
(b) Without limiting the generality of objective (a)
above, the level of inorganic nitrogen should not
exceed 0. 1 milligram per litre, expressed as
annual water column average (arithmetic mean
of at least 3 measurements at 1 metre below
surface, mid-depth and 1 metre above seabed).
J. 5-DAY BIOCHEMICAL OXYGEN
DEMAND
Waste discharges shall not cause the 5-day Inland waters of the Zone
biochemical oxygen demand to exceed 5 milligrams
per litre.
K. CHEMICAL OXYGEN DEMAND
Waste discharges shall not cause the chemical oxygen Inland waters of the Zone
demand to exceed 30 milligrams per litre.
L. DANGEROUS SUBSTANCES
(a) Waste discharges shall not cause the Whole Zone
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.
(b) Waste discharges of dangerous substances shall Whole Zone
not put a risk to any beneficial uses of the
aquatic environment.

SCHEDULE 2

In this statement

'bathing beach subzone' means

(a)a bathing beach that is specified in the Fourth Schedule to the Public Health and
Municipal Services Ordinance (Cap. 132) and situated in the Southern Water Control
Zone,. and

(b)the bathing beach at Discovery Bay, which is delineated and coloured in blue on a plan
marked SWCZ/DB, signed by the Secretary for Health and Welfare and deposited in the
Land Office, Victoria;

'fish culture subzone' means a fish culture zone that is designated in the Fish Culture Zone
(Designation) Order (Cap. 353, sub. leg.);

'Map' means the map comprising seven sheets and marked from SWCZ/Sheet 1 of 7 to SWCZ/
Sheet 7 of 7, signed by the Secretary for Health and Welfare on 18 July 1988 and deposited
in the Land Office, Victoria;

'marine waters' means waters within the Southern Water Control Zone boundary below the high
water mark;

'Mui Wo (A) Subzone' means all that area bounded by the river catchment boundary in the
west, and by a line between a point north of Tseng Tau San Tsuen (22'16'26'N, 113'59'02-
E) and a point cast of Lung Mei Hang (22'16'16'N, 113'59'05'E) in the east, which is
delineated and marked MW(A) on the Map, and which includes the areas of Lin Fa Shan,
Lung Mei Tsuen and Lung Mei Hang;





'Mui Wo (B) Subzone' means all that area bounded by the river catchment boundary in the
south west, and by a line between a point south of Tseng Tau San Tsuen (22'16'19'N,
113'59'04'E) and Tsoi Yuen Tsuen (22'16'12'N, 113'59'13'E) in the east, which is
delineated and marked MW(B) on the Map, and which includes the areas of Mui Wo Kau
Tsuen, part of Tseng Tau San Tsuen and part of Tsoi Yuen Tsuen;

'Mui Wo (C) Subzone' means all that area bounded by the river catchment boundary in the
south, and by a line between Tsoi Yuen Tsuen (22'161 2'N, 11 3'59' 3'E) and a point east
of Tai Tei Tong (22'16'02'N, 113159'32'E), which is delineated and marked MW(C) on
the Map, and which includes the areas of Luk Tei Tong and Lai Chi Yuen Tsuen;

'Mui Wo (D) Subzone' means all that area bounded by a line between a point west of Chung Hau
(22'16'14'N, 113159'31'E) and a point north of Lai Chi Yuen Tsuen (22115'34'N, 11
Y5T54-IE) in the west, and by the river catchment boundary in the cast, which is
delineated and marked MW(D) on the Map, and which includes the areas of Chung Hau and
the Water Treatment Works;

'Mui Wo (E) Subzone' means all that area bounded by a line between a point north of Tseng
Tau San Tsuen (22' 6'26'N, 11 3'59'02'E) and a point south of Tseng Tau San Tsuen (229
61T'N, 11 3'59'04'E) in the west, and by a line between a point east of Pak Ngan Heung
(22'1 6,19'N, 11 315T3 1---E)and a point east of Tai Tei Tong (22116'02'N, 11
Y5T32'E) in the east, which is delineated and marked MW(E) on the Map, and which
includes the areas of Tai Tei Tong, part of Tseng Tau San Tsuen and part of Tsoi Yuen
Tsuen;

'Mui Wo (F) Subzone' means all that area bounded by the river catchment boundary in the
north west and east, and by a line between a point east of Pak Ngan Heung (22'16'19'N,
113'59'31'E) and a point north of Lin Fa Shan (22'16'32'N, 113'58'00'E), which is
delineated and marked MW(F) on the Map, and which includes the areas of Mong To Au, A
Po Long, Wo Sheung Au, Wong Kung Tin, Wo Tin and Pak Ngan Heung;

'other inland waters' means inland waters other than those in the Mui Wo (A), Mui Wo (B),
Mui Wo (C), Mui Wo (D), Mui Wo (E) and Mui Wo (F) Subzones;

'Secondary Contact Recreation Subzone' means an area delineated as such on, the Map.

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