9.1 This section presents an assessment of the potential water quality impacts associated with the construction and operation phases of the proposed expansion and reconstruction of the Park. Recommendations for mitigation measures have been made, where necessary, to reduce the identified water quality impacts to an acceptable level.
Environmental Legislation and Standards
Water Pollution Control Ordinance (WPCO)
9.2
The Water Pollution Control
Ordinance (Cap. 358), in existence since 1980, is the major legislation
relating to the protection and control of water quality in
Table 9.1 Summary of Water Quality Objectives for Marine Waters of
Southern Water Control Zone
|
Parameter |
Objective |
Part(s)
of Zone |
|
E. coli |
annual geometric mean not to exceed 610/100 ml |
secondary contact recreation
subzones; fish culture subzones |
|
Dissolved Oxygen within |
not less than 2 mg/L for 90% samples |
marine waters |
|
Depth averaged Dissolved Oxygen |
not less than 4 mg/L for 90% samples |
marine waters |
|
PH value |
within the
range 6.5 to 8.5; change due to waste discharge not to exceed 0.2 |
marine waters |
|
Salinity |
change due to waste discharge not to exceed 10% of natural ambient
level |
whole zone |
|
Temperature |
change due to waste discharge not to exceed 2oC |
whole zone |
|
Suspended solids |
waste discharge not to raise the natural ambient level by 30%, nor
cause the accumulation of suspended solids which may adversely affect aquatic
communities |
marine waters |
|
Nutrients |
not to be present in quantities that cause excessive growth of algae or other aquatic plants annual mean depth-averaged inorganic nitrogen not to exceed 0.1 mg/L |
marine waters marine waters |
|
Unionized Ammonia |
annual level should not exceed 0.021 mg/L |
whole zone |
Table 9.2 Summary of Water Quality Objectives for Marine Waters of
Western Buffer Water Control Zone
|
Parameter |
Objective |
Part(s)
of Zone |
|
E. coli |
annual geometric mean not to exceed 610/100 ml |
secondary contact recreation
subzones; fish culture subzones |
|
Dissolved Oxygen within |
not less than 2 mg/L for 90% samples |
marine waters |
|
Depth averaged Dissolved Oxygen |
not less than 4 mg/L for 90% samples |
marine waters |
|
pH value |
within the
range 6.5 to 8.5; change due to waste discharge not to exceed 0.2 |
marine waters |
|
Salinity |
change due to waste discharge not to exceed 10% of natural ambient
level |
whole zone |
|
Temperature |
change due to waste discharge not to exceed 2oC |
whole zone |
|
Suspended solids |
waste discharge not to raise the natural ambient level by 30%, nor
cause the accumulation of suspended solids which may adversely affect aquatic
communities |
marine waters |
|
Nutrients |
not to be present in quantities that cause excessive growth of algae or other aquatic plants annual mean depth-averaged inorganic nitrogen not to exceed 0.4 mg/L |
marine waters marine waters |
|
Unionized Ammonia |
annual level should not exceed 0.021 mg/L |
whole zone |
Technical Memorandum
9.3
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, storm
water drains, inland and coastal waters) is provided in the Technical Memorandum (TM) on Standards for
Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal
Waters. 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 standards for effluents discharged into the inshore waters or marine
waters of the Western Buffer and
Practice Notes
9.4 A practice note (PN) for professional persons was issued by the EPD to provide environmental guidelines for handling and disposal of construction site discharges. The ProPECC PN 1/94 “Construction Site Drainage” 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 minimize the water quality impact due to construction site drainage.
9.5
The EPD water quality
monitoring station SM
Table 9.3 Summary Statistics of Marine Water Quality in the
|
Parameter |
|
EPD
Monitoring Station (SM2) |
Water Quality Objectives
(in marine waters) |
|
Temperature (oC) |
|
23.4 (16.8-27.9) |
Natural daily level ± 2 oC |
|
Salinity (ppt) |
|
32.8 (31.4-34.0) |
natural ambient level ± 10 % |
|
Dissolved Oxygen (DO) (mg L-1) |
|
5.8 (4.1-7.6) |
³ 4 mg L-1 |
|
|
Bottom |
5.6 (3.6-7.6) |
³ 2 mg L-1 |
|
DO (% saturation) |
|
81 (62-95) |
- |
|
|
Bottom |
79 (53-95) |
- |
|
pH value |
|
8.2 (8.0-8.4) |
6.5 - 8.5 (± 0.2 from natural range) |
|
Secchi disc depth (m) |
|
2.4 (1.8-4.5) |
- |
|
Turbidity (NTU) |
|
9.0 (5.2-15.7) |
- |
|
SS (mg L-1) |
|
5.5 (1.7-13.5) |
£ natural ambient level + 30% |
|
Silica (as SiO2) (mg L-1) |
|
0.6 (0.2-1.3) |
- |
|
BOD5 (mg L-1) |
|
0.8 (0.4-1.4) |
- |
|
Nitrite Nitrogen (mg L-1) |
|
0.01 (<0.01-0.07) |
- |
|
Nitrate Nitrogen (mg L-1) |
|
0.04 (<0.01-0.13) |
- |
|
Ammonia Nitrogen (mg L-1) |
|
0.02 (0.01-0.04) |
- |
|
Unionised Ammonia (mg L-1) |
|
0.002 (<0.001-0.005) |
£ 0.021 mg L-1 |
|
Total Inorganic Nitrogen (mg L-1) |
|
0.08 (0.01-0.21) |
£
0.1 mg L-1 |
|
Total Nitrogen (mg L-1) |
|
0.19 (0.10-0.32) |
- |
|
Orthophosphate Phosphorus(mg L-1) |
|
<0.01 (<0.01-0.01) |
- |
|
Total Phosphorus (mg L-1) |
|
0.02 (0.02-0.02) |
- |
|
Chlorophyll-a (µg L-1) |
|
2.1 (0.9-9.4) |
- |
|
E. coli (cfu per 100 mL) |
|
35 (2-350) |
< 610 cfu per 100 mL |
|
Faecal Coliform (cfu per 100 mL) |
|
72 (6-590) |
- |
Notes:
1.
Data source: EPD (2004). Marine Water Quality In
2.
Except as specified, data presented are depth-averaged data.
3.
Data presented are arithmetic means except for E. coli and faecal coliforms that are
geometric means.
4.
Data
enclosed in brackets indicate ranges.
9.6
According to the “Marine Water
Quality in Hong Kong
9.7
A widespread decrease of
nitrogen was reported in the
9.8
There are no sizeable natural
streams or rivers within or in close proximity to the proposed works
areas. Existing small watercourses at
the
9.9 Water sensitive receivers identified outside the proposed works area include:
•
Existing
seawater intake for pumping station at
•
•
Secondary
contact recreational waters to the south of
•
Corals
at some sites around the headland (refer to Section 5).
9.10 The location of these identified water sensitive receivers is shown on Figure 9.2.
9.11
The Assessment Area for the
water quality impact assessment covers the Western Buffer WCZ and the
9.12 The water sensitive receivers that may be affected by the construction activities for the redevelopment of the Park have been identified. Potential sources of water quality impact that may arise during the construction and operation phases of the Project are described in the following sections. This task included identifying pollutants from point discharges and non-point sources that could affect the quality of surface water run-off. 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.
9.13 The assessment of operational stage water quality impacts addressed the following potential areas of concern: any proposal for sewage treatment and disposal within the Park; any possible sewage overflow and/or emergency bypass as a result of capacity constraint of sewerage system or emergencies arising from the Project; any additional discharges containing disinfectants/residual chemicals produced from marine life keeping system, aquariums and visitor attraction facilities; any additional discharge from artificial ponds and lakes containing residues of chemicals; any additional discharge from surface runoff due to management of landscaped areas containing residues of chemicals such as fertilizer; and any thermal and chemical discharge from cooling systems.
Identification and Evaluation of Environmental Impacts
Construction Phase
9.14 Potential sources of water quality impact associated with the construction phase of the proposed redevelopment of the Park have been identified and include:
•
construction
site runoff and drainage
•
general
construction activities
•
sewage
effluent produced by on-site workforce.
9.15 No modification work to the existing boat jetty is proposed under the redevelopment of the Park and thus there would not be any marine-based construction works for the Project. This would also avoid incurring direct environmental impact on marine water quality impact and/or coral areas.
Construction
Site Runoff and Drainage
9.16 Runoff from the construction works areas may contain increased loads of sediments, other suspended solids and contaminants. Potential sources of pollution from site drainage include:
•
runoff
from and erosion of exposed soil surfaces, earth working areas and stockpiles
•
release
of grouting, cement, and other materials with rain wash
•
wash
water from dust suppression sprays
•
fuel
and lubricants from maintenance of construction vehicles and mechanical equipment.
9.17 Sediment laden runoff particularly from works areas subjected to excavation or earth works, if uncontrolled, may carry pollutants (adsorbed onto the particle surfaces) into the artificial ponds at Tai Shue Wan and the Lowland Area. Sediment in site run-off discharge ultimately to sea without prior treatment may adversely affect the known coral sites (refer to Section 5 for details).
9.18 As a good site practice, mitigation measures should be implemented to control construction site runoff and drainage from the works areas, and to prevent runoff and drainage water with high levels of suspended solids from entering the artificial ponds and any nearby temporary streams, or drainage channels discharging to sea. With the implementation of adequate construction site drainage and provision of sediment removal facilities as described in Section 9.36, it is anticipated that unacceptable water quality impacts would not arise; impacts on corals have been addressed in Section 5, which concluded that there would be no impacts on the coral sites provided that suitable controls and mitigation measures, as specified in this section, are implemented, because the mitigation measures would be effective in reducing suspended solids concentrations in site run-off (suspended solids are the major concern on the health/ vitaility of corals; further details can be found in section 5). The construction phase discharge would be collected by the temporary drainage system installed by the Contractor and then treated or desilted on-site before discharging to the public drain. The contractor would be required to obtain a license from EPD for discharge to the public drainage system.
9.19
Modification to the existing
boat jetty involving marine work is not anticipated. The nearest bathing beach at
General Construction Activities
9.20 On-site construction activities may cause water pollution from the following:
•
uncontrolled
discharge of debris and rubbish such as packaging, construction materials and
refuse
•
spillages
of liquids stored on-site, such as oil, diesel and solvents etc.
9.21 Good construction and site management practices should be observed, as detailed in Section 9.37-9.38, to ensure that litter, fuels and solvents do not enter the artificial ponds, temporary streams and the public drainage system
Sewage Effluent from Construction Workforce
9.22 Domestic sewage would be generated from the workforce during the construction phase. However, portable chemical toilets can be installed within the construction site. 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 water quality impacts would not be expected.
Operation Phase
9.23 The assessment of operational stage water quality impacts of the redeveloped Park has addressed the following potential areas of concern:
•
additional
discharges, if any, containing disinfectants/ residual chemicals produced from
marine life keeping system, aquariums and visitor attraction facilities
•
additional
discharge, if any, from artificial ponds/ lakes containing residues of
chemicals
•
surface
runoff from turfed/ landscaped areas containing pesticides or fertilizer
residues
•
thermal
and chemical discharge, if any, from cooling systems
•
possible
sewage overflow and/ or emergency bypass as a result of capacity constraint of
sewerage system or emergencies arising from the Project
•
proposal,
if any, for sewage treatment and disposal within the Park
Marine
Life Keeping System, Aquariums and Visitor Attraction Facilities
9.24 In current practice chlorine is added to the seawater pumped from the sea; there are no other chemicals (such as disinfectants) added. Ultraviolet light or ozone is also utilized for sterilizing the seawater in the marine life keeping systems and aquariums for protecting the health of the marine animals. Future operations would be similar in many respects, but there are some operational improvements that would be implemented. In future, ozone rather than chlorine would be the primary method of disinfecting recirculated seawater. Chlorine would only be used as a back-up to the use of ozone. There would not be any new discharges or additional types of discharge containing disinfectants/ residual chemicals produced from the marine life keeping system, aquariums and visitor attraction facilities at the redeveloped Park. Since ozone is rapidly destroyed under natural conditions, there are no concerns regarding its discharge to the environment.
9.25
The redeveloped park would
contain additional marine life-keeping facility/ pools. Circulation/ recovery systems will be used to
re-circulate about 90% of the water volume in the pools; the limited amount of
discharge would comply with discharge licence conditions, and since the
discharge water is filtered/ disinfected seawater, there should be no concern
over discharge back to the sea in limited volume. As the volume of seawater discharged would
not exceed
9.26 As now, the pools and the filters need to be cleaned regularly. Current practice is to completely drain the pools, such as the Ocean Theatre (dolphin show pool) and Pacific Pier (sea lion exhibition pool) approximately two to three times per year. However, re-filling and cooling the seawater in the pools has a financial and energy cost, so in future it is intended that the pools would not be drained at each cleaning cycle, because mechanical cleaning would be employed (rather than hand cleaning as in current practice, that requires complete pool draining) and so there would not be any need to discharge seawater from each pool during the cleaning cycle. Also, since the pools in future would mostly be covered, algal growth would be much less and as a result there would be less need for pool cleaning and the pool draining/ cleaning cycle could be reduced. Hence, as a result of the above, the expected volume of drain water would not be more than the current volume discharged. The filter backwash from the pools and aquariums would be discharged only to the foul sewer via an effluent discharge holding tank.
9.27 Fresh water would be used for certain visitor attraction facilities such as the raging river ride. This water would be filtered and disinfected using chlorine and would mostly be re-circulated. Filter backwash water would be discharged to the foul sewer via an effluent discharge holding tank. There would be no discharge to the sea of water from visitor attraction facilities.
Artificial Ponds
9.28 Currently, there are no discharges from the artificial ponds at the Park during normal operation (there is occasional discharge of excess storm water entering the ponds from the hinterland streams, which overflows to the storm water drain after heavy rainfall). The artificial ponds are subject to natural evaporation and in fact fresh water is regularly added to top up the water level. At the redeveloped park, ponds would be under the same operational regime.
9.29 In the case of backwash of filters, the wash water is currently collected and stored in an effluent holding tank where it undergoes settlement, and is then discharged in a controlled manner to the foul sewer. The same arrangement would be implemented in the future, but in addition it is proposed to reuse as much of the treated backwash water as possible. Any sludge contained inside the effluent tank would be routinely pumped out by a licensed cleaning contractor.
9.30 The artificial ponds at the redeveloped Park would provide an aesthetic pleasing environment and would not be used as a water recreation area. The main source of water within the ponds would be rainwater and run-off from the surrounding hillside streams. Fresh water from the public fresh water mains would be added to the ponds to top-up the water level (to make up the evaporation loss). The water quality within the ponds would be of an acceptable standard for the intended (non-contact) use.
Management of Surface Run-off from Landscaped Areas
9.31 Rainwater falling on landscaped areas would infiltrate into the soil. Rainfall in excess of this capacity creates surface water run-off. Most of the surface water run-off at the lowland (from the ‘Dinosaur Now and Then’ and Giant Panda Habitat attractions) is collected to a stream course just behind the existing Birds Theatre and is diverted to the waterfall pond at the Goldfish Pagoda. The pond water is then used to irrigate the landscaped areas. At other areas, rainwater and surface run-off passes into surface drainage channels and eventually passes to either the storm water drains or (at parts of the headland area) directly to the sea.
9.32 At the redeveloped Park, most of the water running off from the landscaped areas would drain into nearby surface channels along the road side. This type of surface channel would be connected to the storm water drain and diverted to the public drainage system.
9.33 Environmental friendly fertiliser and pesticide (i.e. readily degradable (with low residual half-life of less than 3 days) and low toxicity) would be used at landscaped areas. The management of surface run-off from landscaped areas at the redeveloped Park would follow the existing practice and there would not be any new/ additional types of discharge. However, the landscaped areas at the future park would comprise a slightly larger area than present.
9.34 It is expected that most of the applied fertiliser and pesticide would be retained within the soil/ plant matrix (e.g. absorbed onto the surface of soil particles). Any residual chemicals present in run-off water would likely be of very low concentration since most of the chemicals applied have a relatively high molecular weight (they have limited solubility in water and are readily adsorbed onto particle surfaces). In addition, release of pesticides and fertilisers could be readily controlled by adoption of appropriate mitigation measures (refer below).
9.35 Pesticides and fertilisers would not be applied during or prior to forecast heavy rainfall, and readily degradable chemicals would be used and where possible “natural” rather than “artificial” compounds would be selected (for instance, certain pesticides are not chemicals but are actually microbes that can specifically attack pests). In addition, run-off will not be discharged directly to sea but will be collected in trenches (containing loose soil or other porous media) around or downstream of the landscaped areas. The trenches would act as temporary holding areas to collect the “first-flush” run-off (likely to contain the majority of any washed-out chemicals) and to allow particles that may have chemical content to settle out and to enhance infiltration and absorption of residual chemicals into the soil of the trenches. It is therefore expected that water discharged into the sea would comply with the requirements of the discharge license that pesticides should “not be detectable” in storm water run-off.
Effluent Discharges
9.36 Effluent discharges from the Park are currently required to comply with the standards stipulated in the discharge licences issued by EPD for discharge to the public foul sewers within the Western Buffer Water Control Zone (Licence No. EP820/W9/CW014) and the Southern Water Control Zone (Licence No. EP820/W2/CW002). The Ocean Park Corporation is required to carry out sampling on a monthly basis at the sampling points specified in these two discharge licences for analysis of biochemical oxygen demand and oil and grease. Review of the analytical results for August 2005 show compliance of the discharge samples with the limits stipulated in the two discharge licences. Future discharges would be expected to comply with relevant discharge licence requirements.
Cooling Towers
9.37 There are fresh water cooling towers currently in use at the Park for the Ocean Theatre, Pacific Pier, Atoll Reef, and the Training Yard. Drainage from the cooling towers is currently evaporated and there is no discharge to the storm drain or foul sewer. In winter time when the cooling towers are not in use, the cooling towers are drained empty and the drainage discharged to the foul sewer. Future operation of the cooling towers would follow the existing practice.
9.38 At present, there is no routine cooling water discharge at the Park and a cooling water intake (e.g. for providing circulating seawater cooling) is not proposed to be provided under the redevelopment of the Park. Therefore, additional operational cooling water discharge from the future operations at the redeveloped Park is not expected.
Sewerage
System
9.39
The existing foul sewerage
system within the Park (for the collection and transport of sewage to the
Possible Human Contact with Water
9.40 Water is likely to be present at the following three categories of facilities at the redeveloped Park:
•
Attraction
Exhibit / Show
•
Rides
•
Play Areas.
9.41
Where sea water is utilized for
animal exhibits/ shows or where the guests can have close encounters with the
marine animals (e.g. swim with dolphins) the sea water will be disinfected to
ensure suitability for both the marine animals and guests. Where water is required for rides, play areas
or even water mists, the water will typically be supplied via the fresh water
main. In the case of the water rides
(e.g. flume or rapid rides) any associated water ponds will be treated to meet applicable
standards to ensure the quality of water is
acceptable.
9.42
To prevent outbreak of
Legionnaire’ Disease in
9.43 Proposed mitigation measures for containing and minimizing water quality impacts are summarised below.
Construction Phase
Construction Site Run-off and Drainage
9.44 The site practices outlined in ProPECC PN 1/94 “Construction Site Drainage” should be followed as far as practicable in order to minimise surface runoff and the chance of erosion. The following measures are recommended to protect water quality and sensitive uses of the coastal area (including coral sites identified in Section 5 of this report), and when properly implemented should be sufficient to adequately control site discharges so as to avoid water quality impacts:
•
Before
commencing any site formation work, all sewer and drainage connections should
be sealed to prevent debris, soil, sand etc. from entering public
sewers/drains.
•
Temporary
ditches should be provided to facilitate run-off discharge into appropriate
watercourses, via appropriately sized/ designed silt retention pond or similar
structure. No site run-off should enter
artificial ponds. Cut-off ditches should
be provided for all major site clearance/ excavation works where soils would be
exposed so that instances of uncontrolled run-off from exposed areas would be
minimized. As well as channels, earth/
concrete bunds and/ or sand bags, as appropriate, should be deployed to direct
surface run-off towards channels.
Catchpits and perimeter channels should be constructed in advance of
relevant site formation works.
•
Boundaries
of earthworks should be marked and surrounded by dykes or embankments for flood
protection, as necessary.
•
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 silt removal
facilities should be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and
sediment control structures should be inspected monthly and maintained to
ensure proper and efficient operation at all times and particularly during
rainstorms.
•
Silt
removal facilities, channels and manholes should be maintained and the
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.
•
exposed
soil surfaces should be
covered.
•
Water
pumped out from foundation excavations should be discharged into silt removal
facilities.
•
If
excavation cannot be avoided during rainy seasons, 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. Interceptiong 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 summarized in ProPECC PN 1/94.
•
Exposed
soil areas should be minimized to reduce potential for increased siltation and
contamination of runoff.
•
Earthwork
final surfaces should be well compacted and subsequent permanent work or
surface protection should be immediately performed. Appropriate intercepting channels should be
provided where necessary. Rainwater
pumped out from trenches or excavations should be directed to silt removal
facilities before discharge.
•
Open
stockpiles of construction materials or construction wastes on-site of more
than
9.45
With standard water pollution
control measures set out in ProPECC PN1/
•
Locate the construction phase
discharge point at the outlet of the
existing
•
Sand/ silt
removal facilities with enhanced performance should be employed for treatment
of runoff from the major excavation at the
•
To minimize
the water quality impact during rainy seasons, a silt curtain system should be
used to enclose the construction phase discharge point at Tai Shue Wan.
•
The contractor
should set out and agree with EPD the specific measures, and any additional
measures, in a site run-off management plan, before commencement of
construction activities during the wet season.
9.46
Locating the main construction
phase discharge point at Tai Shue Wan would avoid the areas of coral found to be of most
value (such as areas near the south coast of
General Construction Activities
9.47 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.
9.48 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 nearby water bodies and public drains, 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. The bund should be drained of rainwater after a rain event.
Sewage from Construction Workforce
9.49 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.
9.50 The following measures will be adopted to reduce potential water quality impacts:
•
Ozone would be
the primary disinfectant used in the marine life pools and aquariums. Chlorine would only be used as a
back-up. When chlorine is used in pool
water subject to discharge direct to sea, the discharge shall be less than
•
Mechanical
cleaning of pools will be used to reduce the need to drain the pools for manual
cleaning
•
Filter
backwash water will be discharged only to foul sewer after passing through an
effluent holding tank.
•
Sludge
accumulating in effluent holding tanks will be pumped out and removed from site
by a licensed contractor
•
Discharges to
public sewer or to the sea would need to comply with the requirements of the
relevant effluent discharge license
•
There will be
no discharge of sewage or cooling water to sea
9.51 For the control of non-point source discharges, including run-off from landscaped areas that could contain residual pesticides, fertiliser or other such chemicals, the following measures will be adopted:
•
Where
possible, surface run-off will be collected into artificial ponds at the Park,
to be re-used for irrigation water on landscaped areas
•
Potentially
toxic chemicals including pesticides would not be applied during heavy
rainfall, or if heavy rainfall were to be forecast imminently
•
Surface
run-off will not be discharged direct to sea but will pass through trenches or
catch pits containing loose soil or other porous media to act as a delay to the
“first-flush” run-off and to provide a certain amount of additional adsorption
capacity
•
Environmental
friendly fertilisers and pesticides would be selected where available in the
market, either consisting of natural products and/ or having a rapid
degradation half life of three days or less; chemicals would be selected that
have a low toxicity to non-target animals
Residual Environmental Impacts
9.52 With the full implementation of the recommended mitigation measures for the construction and operation phases of the proposed Project, no unacceptable residual impacts on water quality are expected. It is recommended that regular audit of the implementation of the recommended mitigation measures at the work areas be carried out during the construction phase.
9.53 The key issue in terms of water quality would be the potential for release of sediment-laden water during excavation and slope works for the construction phase of the proposed redevelopment of the Park. Minimisation of water quality deterioration could be achieved through implementing adequate mitigation measures such as control measures on site runoff and drainage from the works areas to minimise construction run-off. Proper site management and good housekeeping practices would also be required to ensure that construction wastes and other construction-related materials would not enter water bodies and the public drainage system. Sewage effluent arising from the construction workforce would also be handled through provision of portable toilets.
9.54 With the implementation of these recommended mitigation measures, the construction works for the Project would not result in unacceptable impacts on water quality. Site inspections should be undertaken routinely to inspect the construction activities and works areas in order to ensure the recommended mitigation measures are properly implemented.
9.55 Additional type of operation discharge from the future operations at the redeveloped Park is not expected, and there would not be any additional types of discharge containing disinfectants/residual chemicals produced from the marine life keeping system aquariums and visitor attraction facilities at the redeveloped Park. Operational procedures to be adopted would avoid or minimise the risk of unacceptable water quality impact. As such, the operation of the redeveloped Park is not expected to result in unacceptable impacts on water quality. Upgrading of the existing foul sewerage system within the Park will be required to prevent sewage overflow and/or emergency bypass as a result of capacity constraint of the sewerage system. There is no proposal for sewage treatment and disposal within the redeveloped Park.