3 WATER QUALITY IMPACT Introduction 3.1 Lung Kwu Chau Is
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Agreement No. CE 55/2000 EIA Study For Construction of Lung Kwu Chau Jetty Civil Engineering Department Final EIA Report 3 WATER QUALITY IMPACT Introduction 3.1 Lung Kwu Chau is located within the Sha Chau and Lung Kwu Chau Marine Park. Water quality is one of the key environmental issues. This chapter presents an assessment of the potential impacts on water quality associated with the construction and operation of the proposed jetty at Lung Kwu Chau. The environmental acceptability of these potential water quality impacts is assessed, with a view to identifying appropriate mitigation measures to reduce any identified adverse impacts to acceptable levels. A morphological impact assessment has also been undertaken for the Project to address any potential impacts on the beach located to the immediate north of the proposed jetty. Environmental Legislation and Standards 3.2 The criteria for evaluating water quality impacts in this EIA Study include: · Technical Memorandum on Environmental Impact Assessment Process (Environmental Impact Assessment Ordinance) (EIAO TM); · Water Pollution Control Ordinance (WPCO); · Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS); · Hong Kong Planning Standards and Guidelines (HKPSG); and · Practice Note for Professional Persons (ProPECC), Construction Site Drainage (PN 1/94). Environmental Impact Assessment Ordinance (EIAO), Cap. 499, S.16 3.3 This Project is a Designated Project under Schedule 2 of the EIAO. The EIAO TM was issued by the EPD under Section 16 of the EIAO. It specified the assessment method and criteria that was followed in this Study. Reference sections in the EIAO TM provide the details of assessment criteria and guidelines that are relevant to the water quality assessment, including: · Annex 6 – Criteria for Evaluating Water Pollution; and · Annex 14 – Guidelines for Assessment of Water Pollution. Water Quality Objectives 3.4 The Water Pollution Control Ordinance (Cap. 358) provides the major statutory framework for the protection and control of water quality in Hong Kong. According to the Ordinance and its subsidiary legislation, Hong Kong waters are divided into ten Water Control Zones (WCZs). Corresponding statements of Water Quality Objectives (WQOs) are stipulated for different water regimes (marine waters, inland waters, bathing beaches subzones, secondary conta ct recreation subzones and fish culture subzones) in the WCZs based on their F:\PROJECTS\A15500\reports\Final EIA\Sect_3.doc 3-1 MAUNSELL Agreement No. CE 55/2000 EIA Study For Construction of Lung Kwu Chau Jetty Final EIA Report Civil Engineering Department beneficial uses. The proposed jetty is located within the North Western Water Control Zone and the corresponding WQOs are listed in Table 3.1. Table 3.1 Summary of Water Quality Objectives for the North Western WCZ Parameter Objective Part(s) of Zone Aesthetic Discharge shall not cause objectionable Whole Zone Appearance odour or discolouration No tarry residue, floating wood, articles Whole Zone made of grass, plastic, rubber or any other substance Mineral oil not visible on the surface. Whole Zone Surfactants shall not give rise to a lasting foam No recognizable sewage-derived debris Whole Zone No floating, submerged or semi- Whole Zone submerged subjects likely to interfere with the free movement or damage of material Not to contain substances which settle to Whole Zone form objectionable deposits E. coli Annual geometric mean not to exceed Secondary contact recreation 610/100 mL subzones Geometric mean not to exceed 180/100 Bathing beach subzones mL during March to October inclusive in 1 year; sample should be taken at least 3 times in 1 calendar month at intervals of between 3 to 14 days Geometric mean of the most recent 5 Tuen Mun (A) and Tuen Mun (B) consecutive samples taken at intervals of Subzones and Water gathering between 7 and 21 days not to be less than ground subzones 1/100 mL Geometric mean of the most recent 5 Tuen Mun (C) Subzone and other consecutive samples taken at intervals of inland waters between 7 and 21 days not to exceed 1000/100 mL Colour Not to exceed 30 Hazen units Tuen Mun (A) and Tuen Mun (B) Subzones and Water gathering ground subzones Not to exceed 50 Hazen units Tuen Mun (C) Subzone and other inland waters Dissolved Not less than 2 mg/L for 90% samples Marine waters Oxygen within 2 m of seabed MAUNSELL 3-2 F:\PROJECTS\A15500\reports\Final EIA\Sect_3.doc Agreement No. CE 55/2000 EIA Study For Construction of Lung Kwu Chau Jetty Civil Engineering Department Final EIA Report Parameter Objective Part(s) of Zone Depth averaged Not less than 4 mg/L for 90% samples Marine waters Dissolved Oxygen Not less than 4 mg/L Tuen Mun (A), Tuen Mun (B) and Tuen Mun (c) Subzones, Water gathering ground subzones and other inland waters pH value Within the range 6.5 to 8.5 units; change Marine waters excepting Bathing due to human activity not to exceed 0.2 Beach Subzones unit Within the range 6.5 – 8.5 units Tuen Mun (A), Tuen Mun (B) and Tuen Mun (c) Subzones, Water gathering ground subzones Within the range 6.0 - 9.0 units Other inland waters Within the range 6.0 to 9.0 units for 95% Bathing Beach Subzones of samples collected during the year; change due to waste discharge not to exceed 0.5 unit Temperature Change due to waste discharge not to Whole zone exceed 2oC Salinity Change due to waste discharge not to Whole zone exceed 10% of natural ambient level Suspended Waste discharge not to raise the natural Marine waters solids ambient level by more than 30%, nor cause the accumulation of suspended solids which may adversely affect aquatic communities Tuen Mun (A), Tuen Mun (B) and Annual median not to exceed 20 mg/L Tuen Mun (C) Subzones, Water gathering ground subzones Annual median not to exceed 25 mg/L Other Inland waters Un -ionized Annual mean not to exceed 0.021 mg/L Whole zone ammonia Nutrients Not to be present in quantities that cause Marine waters excessive growth of algae or other aquatic plants Annual mean depth-average inorganic Castle Peak Bay Subzone nitrogen not to exceed 0.3 mg/L Annual mean depth-average inorganic Marine waters excepting Castle nitrogen not to exceed 0.5 mg/L Peak Bay Subzone 5-Day Not to exceed 3 mg/L Tuen Mun (A), Tuen Mun (B) and Biochemical Tuen Mun (C) Subzones, Water Oxygen gathering ground subzones Demand Not to exceed 5 mg/L Other Inland waters F:\PROJECTS\A15500\reports\Final EIA\Sect_3.doc 3-3 MAUNSELL Agreement No. CE 55/2000 EIA Study For Construction of Lung Kwu Chau Jetty Final EIA Report Civil Engineering Department Parameter Objective Part(s) of Zone Chemical Not to exceed 15 mg/L Tuen Mun (A), Tuen Mun (B) and Oxygen Tuen Mun (C) Subzones, Water Demand gathering ground subzones Not to exceed 30 mg/L Other Inland waters Toxic Not to be present at levels producing Whole zone Substances significant toxic effect, carcinogenic, mutagenic or teratogenic effects in humans, fish or any other aquatic organisms, with due regard to biologically cumulative effects in food chains and to interactions of toxic substances with each other Not to cause a risk to any beneficial use of Whole zone the aquatic environment Phenol Not to be present in such quantities as to Bathing beach subzones produce a specific odour, nor to exceed 0.05 mg/L as C6H5OH Turbidity Not reduce light transmission substantially Bathing Beach Subzones from the normal level Hong Kong Planning Standards and Guidelines (HKPSG) 3.5 The Hong Kong Planning Standards and Guidelines (HKPSG), Chapter 9 (Environment), provides additional information on regulatory guidelines against water pollution for sensitive uses such as aquaculture and fisheries zones, bathing waters and other contact recreational waters. Technical Memorandum 3.6 Besides setting the WQOs, the WPCO controls effluent discharging into the WCZ through a licensing system. A Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS) was issued under Section 21 of the WPCO that gives guidance on the permissible effluent discharges based on the type of receiving waters (foul sewers, storm water drains, inland and coastal waters). The limits control the physical, chemical and microbial quality of effluents. Any effluent discharges from the proposed construction activities should comply with the standards for effluents discharged into the inshore waters or marine waters of the North Western WCZ, as shown in Table 10a and Table 10b, respectively, of the TM-DSS. Practice Note 3.7 A practice note for professional persons was issued by the EPD to provide guidelines for handling and disposal of construction site discharges. The ProPECC PN 1/94 “Construction Site Drainage” provides good practice guidelines for dealing with ten types of discharge from a construction site. These include surface runoff, groundwater, boring and drilling water, bentonite slurry, water for testing and sterilisation of water retaining structures and MAUNSELL 3-4 F:\PROJECTS\A15500\reports\Final EIA\Sect_3.doc Agreement No. CE 55/2000 EIA Study For Construction of Lung Kwu Chau Jetty Civil Engineering Department Final EIA Report water pipes, wastewater from building constructions, acid cleaning, etching and pickling wastewater, and wastewater from site facilities. Practices given in the ProPECC PN 1/94 should be followed as far as possible during construction to minimise the water quality impact due to construction site drainage. Sediment Quality 3.8 Dredged sediments destined for marine disposal are classified according to a set of regulatory guidelines for designation of sediments (Management of Dredged/Excavated Sediment, WBTC No. 3/2000) issued by the Works Bureau and Planning, Environment and Lands Bureau in April 2000.