CIVL 395 Environmental Impact Assessment 3 Housing Development in Tuen Mun Area 1 Proposed Bridge at

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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
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• Water Quality Impact Assessment
• Sewerage Impact Assessment

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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

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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

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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

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Baselining the Environment
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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

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Water Quality Numerical Modelling the Waterbody
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Water Quality Numerical Modelling the Waterbody
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Water Quality Numerical Modelling Output
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Other Water Quality Assessment Criteria

• Water quality for flushing water intake at sea
• Colour lt 20 Hazen units
• Turbidity lt 10 NTU
• Suspended solids lt 10 mg/l
• Dissolved oxygen gt 2 mg/l
• Ammonium-N lt 1 mg/l
• BOD5 lt 10 mg/l
• Synthetic detergents lt 5 mg/l
• E. coli lt 20,000/100 ml

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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

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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

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Existing Sewers Drains
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Unit Flow Factors
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Note Peaking factor is applied globally.
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Note Peaking factor is applied globally.
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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

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300
300
300
Existing Sewers
300
LEGEND CL Cover level (ground level) A Incoming
sewer invert level X Outgoing sewer invert level
375
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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.

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• Solid Waste

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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 (CD) Materials
• Accounts for some 40 of waste disposed of to
  landfills in 2003
• Insufficient landfill space
• Over 80 of CD materials is inert
• Distinguishes between
• Public fill the inert portion
• CD 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 CD
  materials, the preparation of a CD Material
  Management Plan

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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

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Solid Waste

• Control and mitigation
• Contaminated soil/sediments
• EPDs 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
• CD Materials
• Waste Management Plan
• Designated disposal sites
• 3 strategic landfills WENT, NENT, SENT
• Trip-ticket system
• Sorting of CD 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