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CIVL 395 Environmental Impact Assessment [3]
Housing Development in Tuen Mun Area 1 Proposed Bridge at Tuen Mun Area 18
HS Kan
March 2007
Water Pollution Control Ordinance Cap 358 (WPCO)
All kinds of wastewater, whether discharged into communal sewers, storm drains, river courses or waterbodies are subject to control, except
Domestic sewage discharge into sewers Discharge of unpolluted water
All discharges subject to control shall be covered by an effluent discharge licence
Physical, chemical and microbial quality Flow Dependent upon
• Location of discharge• Beneficial use of the receiving water
Pre-treatment as necessary
Technical Memorandum on EIA Process, EIAO Cap499 Annex 6
4 aquatic components to be considered Water quality Hydrology Bottom sediments ecology
To achieve Water Quality Objectives under the WPCO Aesthetic enjoyment
• Sight, smell, taste, touch Human health
• Potable use, irrigation, bathing & recreational, contamination of seafood Pathogenic indicators E. coli Bioaccumulation, paralytic shellfish poisoning, etc
Aquatic life• Integrity and balance of the aquatic ecosystem
Natural properties of the waterbody – temp, salinity, DO, pH, turbidity, etc. Nutrient input, accumulation of harmful substances Physical environment of the waterbody – sedimentation, etc.
Industrial use• Prevention of deleterious chemicals, flotables, biological growths, etc.
Cooling water systems, shipping
Water Quality Impact Assessment Description of the environment
Marine water, coastal water, river, etc Identification of pollutant sources
Existing or planned From the project itself and elsewhere, e.g. concurrent projects
Identification of water sensitive receivers Beaches, water recreation areas, flushing water intakes, cooling water
intakes, fish culture zones, marine parks, corals, mangroves, SSSI, etc. Existing or planned
Baselining the environment Existing water quality monitoring measurements, etc Dedicated baseline surveys Common parameters measured:
DO, turbidity, SS, BOD, Inorganic N, Ammonia N, chlorophyll-a, E. coli
Impact evaluation Prediction of the transport of pollutants from the sources to the
receivers Oceanographic data Flow tracking Numerical modelling
Mitigation measures and monitoring
Water Quality Modelling Physical, chemical and biological processes Hydrodynamic modelling
Coastline and bathymetry Oceanographic and meteorological information Non-steady flow and transport phenomena
Water quality modelling Pollutant inventory Advection-diffusion-reaction mechanisms Physical process, e.g.
oxygen exchange with the atmosphere sedimentation of suspended substances
Biochemical process, e.g. nitrification algal growth decay
Boundary conditions, extent of model Calibration and validation important
Other Water Quality Assessment Criteria
Water quality for flushing water intake at sea Colour < 20 Hazen units Turbidity < 10 NTU Suspended solids < 10 mg/l Dissolved oxygen > 2 mg/l Ammonium-N < 1 mg/l BOD5 < 10 mg/l Synthetic detergents < 5 mg/l E. coli < 20,000/100 ml
Water Quality Impacts – Construction phase
Construction site runoff Exposed soil surfaces Oil from machineries, etc
Bentonite slurry, grout, etc from piling works Sewage from workforce
Presence of sewers, chemical toilets Accidental spillage of chemicals Mitigation measures
Good housekeeping with regular tidying Shielding of stockpiled materials Intercepting channels Silt traps Oil separators Reuse and proper disposal of bentonite Protection of drainage facilities
Sewerage Impact Assessment To safeguard public health Additional flows & loads arising Impacts on existing sewerage facilities
Sewers Pumping stations Sewage treatment works Disposal facilities Others e.g. dry weather flow interceptors
Proper pre-treatment, treatment and/or disposal of flows arising, at all stages of the project
DSD Sewerage Manual
Additional information in relation to SIA
Public housing estate at Site B Housing type: Low-cost rental No. of employees: 20
Private housing Housing type: R1 No. of employees: 20
Private housing club house Restaurant with an average daily flow of 1000 m³/day No. of employees: 35
Primary school No. of students: 700 No. of employees: 80
MH-B2
CL 16.40
A1 12.45
X1 12.40
MH-B1
CL 16.50
X1 14.70
MH-A1
CL 21.80
X1 20.70
MH-A2
CL 18.70
A1 17.15
X1 17.10
MH-A3
CL 15.20
A1 13.10
X1 13.00
MH-B3
CL 7.50
A1 5.20
X1 5.15
Existing Sewers
LEGEND
CL Cover level (ground level)
A Incoming sewer invert level
X Outgoing sewer invert level
300
300
375
300
300
Some particular points to consider Depth and alignment of new sewers Connection to existing sewerage system
Need new pumping stations? Any constraints due to the Light Rail Transit?
Trenchless methods Minimum clearance requirements?
Impacts on the existing residents and other people during construction stage Impacts on all residents and other people during the operation stage
ASSUME: Capacity of existing sewerage is adequate.
Solid Waste Numerous ordinances and regulations
Waste Disposal Ordinance Waste Disposal (Chemical Waste) (General) Regulations Public Cleansing and Prevention of Nuisance Regulation under
the Public Health and Municipal Services Ordinance Provides control on illegal tipping of wastes on unauthorized sites
Website for ordinances and regulations: http://www.justice.gov.hk/Home.htm
Construction & Demolition (C&D) Materials Accounts for some 40% of waste disposed of to landfills in 2003
Insufficient landfill space Over 80% of C&D materials is inert
Distinguishes between Public fill – the inert portion C&D waste – the non-inert portion
Material with more than 30% inert content need sorting before disposal to landfill
For projects generating 50,000 m³ or more C&D materials, the preparation of a C&D Material Management Plan
Solid Waste Other wastes in construction stage
Used bentonite General refuse Contaminated soil/sediments
Assessment EIAO-TM Annexes 7 and 15
Estimate the types and quantities of wastes Identify opportunities for waste reduction and beneficial use
of the waste Alternative design and alternative materials Assess impacts associated with the handling and disposal of
wastes
Solid Waste Control and mitigation
Contaminated soil/sediments EPD’s Guidance Notes for Investigation and Remediation of Contaminated
Sites of Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshops
Works Bureau Technical Circular No. 3/2000 on dredged sediment C&D Materials
Waste Management Plan Designated disposal sites
• 3 strategic landfills: WENT, NENT, SENT Trip-ticket system Sorting of C&D materials Use of recycled aggregates Use of non-timber formwork and recyclable materials for temporary works Charging scheme
Good housekeeping Proper chemical waste handling procedures Reduction, Recycle, Reuse