· Fisheries Protection Ordinance (Cap. 171) – promotes the conservation of fish and other forms of aquatic life within Hong Kong waters by regulating fishing practices to prevent detrimental activities to the fisheries industry. The authority may also make rules for the management and control of fishing in any fisheries protection area, including but not limited to the specification of any zone within any fisheries protection area and the prohibition of any fishing in the specified zone.

· Marine Fish Culture Ordinance (Cap. 353) – regulates and protects marine fish cultured by designating areas of fish culture zone, granting licenses, prohibiting unauthorised vessels and any deposition of chemicals or other substances which are likely to cause injury to fish in a fish culture zone.

· WPCO (Cap. 358) – aims to control water pollution in waters of Hong Kong. WCZs are designated with individual water quality objectives to promote the conservation and best use of those waters in the public interest. The most updated water quality objectives for the Junk Bay WCZ, Eastern Buffer WCZ and Victoria Harbour WCZ were revised in June 1997.

· Annex 17 of the EIAO-TM – sets out the methodology for assessment of fisheries impacts, in order to provide objective identification, prediction and evaluation of potential fisheries impacts arising from the Project. Annex 9 provides evaluation criteria.

9.3 Assessment Methodology

9.3.1 Assessment Area

9.3.1.1 The assessment area for fisheries impact assessment was the same as the assessment area for water quality impact assessment and included any other areas likely to be impacted by the Project. Special attention was given to the fishing activities and spawning and nursery grounds of commercial fisheries resources within the assessment area and any nearby fish culture zones.

9.3.2 Assessment Approach and Methodology

9.3.2.1 Collation and desktop review of available relevant fisheries baseline data (e.g. AFCD) Port Survey 2006, EIAs and other available relevant studies) within or in vicinity to the assessment area were conducted. Potential direct/indirect, short term/long term, on-site/off-site and cumulative fisheries impacts arising from the Project were identified and evaluated where possible. Special attention was given to loss or disturbance of fishing ground, fisheries habitat and spawning and nursery ground; water quality deterioration at ensitive receivers such as fish culture zones; permanent loss or temporary occupation of fish ponds; deterioration of water quality in fish ponds and any surrounding watercourses; and disruption or disturbance of pond culture related activities, where appropriate. Mitigation measures and monitoring and audit programme were recommended, where necessary.

9.3.2.2 The criteria and guidelines as stated in Annexes 9 and 17 of the EIAO-TM were followed for evaluating and assessing fisheries impact arising from the construction and operation of the Project, and decommissioning of the existing STSTW of the Project.

9.4 Description of Baseline Condition

9.4.1.1 Following the collation and review of existing fisheries baseline information, relevant literatures on capture and culture fisheries within and in vicinity of the assessment area are listed in Table 9.1 below.

Table 9.1 Baseline Information of Fisheries Resources in the Assessment Area

Relevant Literatures
AFCD Port Survey 2006 (AFCD, 2015b)
Aquaculture and Capture Fisheries data available from AFCD website (AFCD, 2015a and 2015b)
AFCD Annual Report 2007 – 2014
Fisheries Resources and Fishing Operations in Hong Kong Waters (ERM, 1998)
Relocation of Sha Tin Sewage Treatment Works to Caverns – Feasibility Study –Preliminary Environmental Review (DSD, 2014)

9.4.1.2 The relevant desktop information reviewed is considered sufficient for evaluating the importance of the potentially impacted fisheries resources and fishing operations within the assessment area. Therefore, no information gap on fisheries baseline conditions within the assessment area was identified and fisheries surveys are not needed for the current EIA study.

9.4.2 Sites of Fisheries Importance

9.4.2.1 There are four mariculture areas identified in the assessment area, Lo Fu Wat Fish Culture Zone (FCZ), Yung Shue Au FCZ, Yim Tin Tsai FCZ and Yim Tin Tsai (East) FCZ, which are located approximately 9 km, 8 km, 4.5 km and 4.5 km away from the existing STSTW respectively. A potential subzone of Yim Tin Tsai FCZ is located approximately 3.2 km away from the existing STSTW. In addition, Three Fathoms Cove was identified as important nursery area for commercial fisheries resources with high fish fry production within the assessment area (located approximately 6.5 km away from the existing STSTW). The locations of the key fisheries resources within the assessment area are shown in Figure No. 60334056/EIA/9.01. Based on the findings of the literature review, no important nursery or spawning area was identified in immediate vicinity of the existing STSTW in Tolo Harbour (ERM, 1998).

9.4.3 Capture Fisheries

9.4.3.1 In 2014, the capture fisheries industry produced an estimated 160,789 tonnes of fisheries valued at about $2,530 million (AFCD, 2015b). This industry is operated by approximately 9,400 local fishermen with 4,500 fishing vessels. Fishing activities are mainly conducted in the waters of the adjacent continental shelf in the South China Sea. Main fishing methods include trawling, long-lining, gill-netting and purse-seining with the majority of the total catch obtained through trawling. Trawling landed the majority of the catch in Hong Kong waters prior to 31 December 2012, after which a ban on trawling was implemented with the intensions of protecting marine resources and ecosystem so that damaged seabed and depleted marine resources can rehabilitate. Some recent data on local capture fisheries industry are summarised in Table 9.2 below.

Table 9.2 Recent Figures of Hong Kong Capture Fisheries Industry

Parameter	2014	2013	2012	2011	2010	2009	2008	2007	2006	2005
Fishing fleet size (No. of vessels)	4,500	4,000	4,000	4,000	3,900	3,700	3,800	4,000	3,940	4,150
Local Fishermen engaged in capture fisheries	9,400	8,800	8,800	8,500	8,200	7,600	8,000	8,500	8500	9,170
Production (tonnes)	160,789	170,729	155,230	170,720	168,000	159,000	158,000	154,000	155,000	162,000
Values of produce (HK$ million)	2,530	2,338	2,317	2,358	2,100	2,000	1,780	1,530	1,600	1,600

9.4.3.2 The latest AFCD Port Survey 2006 (AFCD 2015b) provides the most updated information on capture fisheries in Hong Kong waters, including both fishing operation and fisheries production (adult fish and fry). In general, the highest fish yields in Hong Kong were obtained in the eastern waters (e.g. Tolo Channel, Crooked Haven, Port Shelter, and Po Toi) and the southwestern waters (e.g. Lamma Island, Cheung Chau and Soko Islands).

9.4.3.3 The fishing operation within the assessment area was mainly supported by vessels of less than 15 m in length. Sampans were the dominant fishing vessels but other vessels such as stem trawler, pair trawler, shrimp trawler, gill netters, long liners and purse seiner were also operated within the assessment area. The capture fisheries data within the assessment area are summarised in Table 9.3. The existing STSTW is located next to Sha Tin Hoi.

Table 9.3 Summary of Capture Fisheries Data in the Assessment Area

Parameter	Sha Tin Hoi	Tolo Harbour	Plover Cove	Three Fathoms Cove	Tolo Channel
No. of vessels	10 - 50	10 - 400	10 - 400	10 - 400	100 - 400
Adult fish production in terms of weight (kg/ha)	>0 - ≤50	>0 - 200	>0 - 100	>0 - 400	100 - 400
Fish fry production in terms of density (tails/ha)	None reported	0 - ≤50	0 - ≤50	100 - 500	>0 - 100
Annual fisheries production (adult and fry) in terms of value (HK$/ha)	>0 - ≤500	>0 - 5000	500 - 5000	2000 - 10000	2000 - 10000

9.4.3.4 The number of fishing vessels operating within the assessment area was generally between 10 and 400 vessels, while that near the existing STSTW was low (10 - 50 vessels).

9.4.3.5 In terms of weight, >0 - 400 kg/ha adult fish was produced within the assessment area. The weight of adult fish production near the existing STSTW was low (>0 - ≤50 kg/ha). Fish production increased towards the Tolo Channel. Fish production was the highest in the western portion of Tolo Channel, ranged from 200 to 400 kg/ha (AFCD, 2015b). However, this area is located at distance (approximately 4 km) from the existing STSTW.

9.4.3.6 Fry collection in Hong Kong has reduced in scale in recent years. The latest interview studies reported that fry collection only occurs in a few areas (AFCD, 2015b). The highest fry collection was mainly found in the northeast inshore waters at Three Fathoms Cove, Crooked Harbour, Double Haven, and Long Harbour. Three Fathoms Cove is located within the assessment area, with 100 - 500 tails/ha fry production. It is approximately 6.5 km away from the existing STSTW.

9.4.3.7 Tolo Harbour is not considered as important spawning or nursery areas for commercial fish species. Although reproductive individuals of Ponyfish have been collected in Tolo Harbour, this species does not appear to have a specific spawning ground as reproductive individuals were collected in a wide range area from Tolo Harbour and northeastern waters, to Junk Bay and as far as southwest Lantau (ERM, 1998). A low level of fish fry production (>0 – ≤50 tails/ha) was reported in Tolo Harbour (AFCD, 2015b).

9.4.3.8 Tolo Channel has been identified as a potential fish nursery ground of Seabream species (Chrysophrys major, Rhabdosargus sarba and Sparus spp.), Shrimp (Metapenaeopsis palmensis) and Lutjanus fry (ERM, 1998). Fish fry production ranging from 0 – 500 tails/ha was reported in Tolo Channel (AFCD, 2015b). Three Fathoms Cove was identified as important nursery area for commercial fisheries resources with high fish fry production (100 – 500 tails/ha).

9.4.3.9 Overall, in terms of capture fishery production value, the assessment area showed a range of production value from >HK$0 to 10,000 per hectare annually. Moderate to high production (HK$5,000 - 10,000 per hectare) occurred in Tolo Channel and Three Fathoms Cove, whilst a low production value (>HK$0 - ≤500 per hectare) was recorded near the existing STSTW.

9.4.3.10 Capture fisheries production of the top ten fish families within the assessment area is summarised in Table 9.4.

Table 9.4 Fisheries Production (kg/ha) of the Top Ten Families in the Assessment Area

Top Ten Fish Families	Sha Tin Hoi	Tolo Harbour	Plover Cove	Three Fathoms Cove	Tolo Channel
Scad (Caragidae)	≤5	5 -10	≤5	10 - 20	10 - 40
Shrimp	None reported	≤5	≤5	≤5	≤5
Rabbitfish (Siganidae)	≤5	≤5 - 20	5 - 20	≤5 - 40	10 - 60
Squid	≤5	≤5	≤5	≤5 - 20	≤5 - 20
Croaker (Sciaenidae)	None reported	≤5	≤5	0 -20	5 - 20
Crab	≤5	≤5 - 20	≤5 - 10	10 - 60	5 - 40
Mullet (Mugilidae)	≤5	≤5 - 10	≤5 - 10	0 - 40	≤5 - 40
Sardine (Clupeidae)	None reported	≤5	≤5	0 - 20	5 - 20
Seabream (Sparidae)	≤5	≤5 - 10	≤5 - 10	≤5 - 40	10 - 40
Anchovy (Engraulidae)	None reported	≤5	≤5	≤5	≤5

9.4.3.11 Production of Crab and Rabbitfish was high in Three Fathoms Cove and Tolo Channel respectively. Fish production was generally low near the existing STSTW (i.e. Sha Tin Hoi, Tolo Harbour and Plover Cove). Only low production of Scad, Rabbitfish, Squid, Crab, Mullet and Seabream were reported in vicinity of the existing STSTW.

9.4.4 Culture Fisheries

9.4.4.1 Marine culture fisheries included marine fish culture and oyster culture. Mariculture areas for marine fish included 26 FCZs located in various sheltered coastal areas in Hong Kong marine waters and occupied about 209 ha of marine areas with about 968 licensed operators in 2014 (AFCD, 2015a). Majority of the licensed farms are small, family-based and consisting of one to two rafts with average total area of around 290 m². Oyster culture has been practiced on the Deep Bay mudflats for at least 200 years. Production from oyster culture in 2014 was about 121 tonnes (meat only) valued at $10 million (AFCD, 2015a).

9.4.4.2 There are four FCZs but no oyster culture present in the assessment area. Lo Fu Wat FCZ, Yung Shue Au FCZ, Yim Tin Tsai FCZ and Yim Tin Tsai (East) FCZ are located approximately 9 km, 8 km, 4.5 km and 4.5 km away from the existing STSTW respectively. The locations of the FCZs are shown in Figure No. 60334056/EIA/9.01.

9.4.4.3 Although no figures are available for the individual production of FCZs, it was estimated that culture fisheries of marine fish production in 2014 weighted 1,255 tonnes and was valued at $115 million which catered for approximately 6% of local demand for live marine fish (AFCD, 2015a). Recent figures on marine fish culture are present in Table 9.5.

Table 9.5 Recent Figures of Hong Kong Culture Fisheries Industry

Parameter	2014	2013	2012	2011	2010	2009	2008	2007	2006	2005
Licensed operator	968	987	1,008	1,015	1,035	1,050	1,060	1,070	1,080	1,100
Production (tonnes)	1,255	1,005	1,299	1,185	1,512	1,437	1,370	1,532	1,488	1,539
Value (HK$ million)	115	94	117	94	118	92	82	99	89	76

9.4.4.4 The types of species produced from culture fisheries depend on the availability of imported fry. Common species cultured include green grouper, brown-spotted grouper, giant grouper, Russell's snapper, mangrove snapper, goldlined seabream, and star snapper (AFCD, 2015b).

9.4.4.5 In addition, certain areas in Hong Kong waters are important fish spawning and nursery grounds and are proposed to designate as Fisheries Protection Areas (FPAs) to protect fish fry, juvenile and spawning fish, help restore fisheries resources in Hong Kong waters, and promote the sustainable development of fisheries in the long run. There are two proposed FPAs in the eastern waters including the “Tolo Channel and Long Harbour” and the “Port Shelter”. The closest one at the “Tolo Channel and Long Harbour” is located approximately over 8 km from the existing STSTW.

9.4.4.6 Pond fish culture industry is centred in the north-west New Territories. Fish ponds are either freshwater or brackish. In 2014, the local inland ponds, covering an area of approximately 1,140 ha, produced 2,001 tonnes of freshwater fish amounting to $44 million (AFCD, 2015a). There are no fish ponds within the assessment area. Therefore there would be no impacts on pond culture fisheries.

9.5 Identification, Prediction and Evaluation of Environmental Impacts

9.5.1 Construction Phase

Direct Impacts

Loss of Fishing Grounds

9.5.1.1 The Project will only involve land-based construction works. There will be no disturbance to marine or riverbed sediments. Under the Project design, any Project effluent bypass to the Tolo Harbour will be discharged separately through the existing emergency outfall of the TPSTW and STSTW (refer to Figure No. 60334056/EIA/9.01). Construction of the connection pipes to emergency outfall of STSTW by trenchless method underneath Shing Mun River was proposed. The construction method would not cause disturbance to the marine sediment. In addition, the demolition of the existing STSTW would be land-based only with no disturbance to marine or riverbed sediments. With the adoption of trenchless method, no loss of fishing ground is anticipated.

Indirect Impacts

THEES Connection Works

9.5.1.2 In order to maintain the current arrangement in discharging effluent to KTN (Kai Tak River after the re-construction and upgrading works currently being undertaken by CEDD) through THEES tunnel, provision of a dry construction zone within the THEES tunnel system to allow connection to the CSTW would be essential for the Project as detailed in Section 2.8.4. During the connection works, the THEES needs to be temporarily suspended from its normal operation with effluent bypasses into the Tolo Harbour. Without effluent bypass to Tolo Harbour, effluent will be running inside the THEES tunnel system rendering the construction or connection works not possible.

9.5.1.3 On the other hand, under the existing practice, regular inspection and repair of the THEES would be carried out when necessary to maintain proper functioning and integrity of the THEES. During each THEES maintenance event, secondarily treated and disinfected effluent from TPSTW and STSTW would be temporarily discharged to the Tolo Harbour to provide a dry zone within the THEES tunnel for a maximum duration of 4 weeks in non-algal bloom season with frequency less than once per year. To minimize water quality impact to Tolo Harbour, the necessary THEES connection works required for this Project will be split into a number of steps for sequential and synchronized implementation with THEES maintenance, thereby avoiding the need for additional temporary suspension of the THEES.

Changes in Water Quality by Land-based Construction Works

9.5.1.4 Discharge from land-based construction works (general cleaning and polishing, wheel washing, dust suppression, utility installation, etc.) and construction site runoff (e.g. runoff and erosion of exposed bare soil and earth, drainage channel, earth working area and stockpiles, etc.) during the cavern development and demolition of the existing STSTW may cause a temporary increase in SS level. With the implementation of appropriate measures to control run-off and drainage from the construction site, as well as the adoption of guidelines and good site practices for handling and disposal of construction discharges (refer to Section 5.7.2), unacceptable impacts on water quality and fisheries due to water quality deterioration by land-based construction works are not expected.

9.5.1.5 The overall evaluation of construction phase fisheries impacts are summarised in Table 9.6.

Table 9.6 Summary of Potential Fisheries Impact during Construction Phase

Criteria	Construction Phase Impact
Nature of Impact	Direct Impact The Project will only involve land-based construction works. There will be no disturbance to marine or riverbed sediments. Trenchless method underneath Shing Mun River was proposed for the construction of connection pipes to existing emergency outfall of STSTW. The construction method would not cause disturbance to the marine sediment. The demolition of the existing STSTW would be land-based only with no disturbance to marine or riverbed sediments. No loss of fishing ground is anticipated. Indirect Impact THEES connection works required for this Project will be split into smaller sections and each section will be arranged to be undertaken to synchronized with THEES maintenance for a duration not longer than 4 weeks each outside the algae blooming season and the frequency will be no more than once per year. No additional water quality impact and no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. With the implementation of appropriate measures to control run-off and drainage from the construction site, as well as the adoption of guidelines and good site practices, unacceptable impacts on water quality and fisheries due to water quality deterioration by land-based construction works are not expected.
Size of Affected Area	Direct Impact There will be no disturbance to marine or riverbed sediments. No loss of fishing ground is anticipated. Indirect Impact Inner Tolo Harbour and Tolo Channel No additional water quality impact and no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. With the implementation of mitigation measures and the adoption of guidelines and good site practices, unacceptable impacts on water quality, and hence, fisheries impacts due to water quality deterioration by land-based construction works are not expected.
Loss of Fisheries Resources / Production	There will be no disturbance to marine or riverbed sediments. No loss of fisheries resources / production is anticipated. No additional water quality impact and no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. With the implementation of mitigation measures and the adoption of guidelines and good site practices, unacceptable impacts on water quality, and hence, fisheries impacts due to water quality deterioration by land-based construction works are not expected.
Destruction and Disturbance of Nursery and Spawning Grounds	There will be no direct loss of important nursery and spawning grounds for commercial fisheries species. No additional water quality impact and no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. With the implementation of mitigation measures and the adoption of guidelines and good site practices, unacceptable impacts on water quality, and hence, fisheries impacts due to water quality deterioration by land-based construction works are not expected.
Impact on Fishing Activity	There will be no disturbance to marine or riverbed sediments. No impact on fishing activity is anticipated.
Impact on Aquaculture Activity	Minor. No additional water quality impact and no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. With the implementation of mitigation measures and the adoption of guidelines and good site practices, unacceptable impacts on water quality, and hence, fisheries impacts due to water quality deterioration by land-based construction works are not expected.
Overall Fisheries Impact	Minor

9.5.2 Operation Phase

Indirect Impacts

Changes in Water Quality during Normal Plant Operation

Elevation of Suspended Solids (SS)

9.5.2.1 The increase in SS level may potentially cause lethal or sublethal effects on fish by clogging the delicate structures of gills in fish and therefore prohibiting the exchange of dissolved oxygen. Fish eggs and fish fry are more susceptible to smothering of respiratory surface due to high sediment levels. Adult fish are more likely to move away when they detect increase in SS level and therefore less sensitive to the effects from SS elevation.

9.5.2.2 SS occur naturally in the marine environment due to vertical flux and wave action of water current, particularly in estuaries. Consequently fish have evolved adaptations to tolerate the increased SS, including clearing their gills by flushing water through and simply moving away from turbid waters.

9.5.2.3 If SS levels exceed tolerance thresholds and the fish are unable to move away from the area, they may become stressed or even die. The rate, timing and duration of SS elevations will influence the type and extent of impacts on fish and crustaceans (CPPC, 2006). Lethal response had not been observed in adult fish at SS level less than 125 mg/L, and sublethal effects were only reported at levels exceeded 90 mg/L. However, guideline values were identified for fisheries and selected marine ecological sensitive receivers in Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment based on international marine water quality objective guidelines for the ecosystem protection. The recommended value was 50 mg/L (AFCD, 2001). Besides, the WQO for SS (i.e. elevation of less than 30% of ambient baseline level) is also generally applicable to fisheries sensitive receivers inside the relevant WCZs.

9.5.2.4 According to the water quality impact assessment, operation of this Project (Scenario 5 – “with Project” scenario) would slightly reduce the mean SS level in Sha Tin Hoi waters when compare with the baseline condition (Scenario 4 – “without Project” scenario). The SS level is predicted to be either lower than (at Yim Tin Tsai FCZ, Yim Tin Tsai (East) FCZ and potential subzone of Yim Tin Tsai FCZ) or the same as (at Yung Shue Au FCZ, Lo Fu Wat FCZ and the important nursery area for commercial fisheries resources) the baseline condition (refer to Appendix 5.05).

Decrease of Dissolved Oxygen (DO)

9.5.2.5 Increase in SS in water column combined with a number of other physical or biotic factors would reduce DO in water column. Elevated SS reduces light penetration, lowers the photosynthetic rate of phytoplankton and so lowers the rate of oxygen production in the water column. Also the release of inorganic substances from the temporary bypass events may cause eutrophication and algal bloom. Oxidation of dead algae may use up some of the oxygen in the water. If oxygen levels are depleted to low levels, fish, especially those in early life stages may be unable to tolerate such conditions and suffer hypoxia-induced mortality and / or stress including reduced feeding and growth rate. Normal operation of this Project would significantly improve the mean depth-averaged (DA) DO level and the minimum bottom DO level in the Harbour Subzone of the Tolo Harbour as compared with the baseline condition. Full compliance of DO was predicted at the four FCZs, the potential subzone of Yim Tin Tsai FCZ and the important nursery area for commercial fisheries resources under Scenarios 4 and 5 (refer to Appendix 5.05) and would be within the ranges for FCZs (DO: 4 – 8 mg/L) stated in the Environmental Management of Mariculture (AFCD, 2009).

Release of Nutrients

9.5.2.6 High nutrient levels in marine water may trigger rapid increase in phytoplankton, resulting in algal bloom. When a large number of algae die, degradation of dead algae would cause sudden drop in DO which leads to suffocation of fish and other organisms. The phytoplankton may also produce biotoxins which could be lethal to fish. According to the water quality impact assessment, the TIN levels are similar at all the fisheries resources under the Scenario 4 and Scenario 5.

Chlorophyll-a

9.5.2.7 Chlorophyll-a is a green photosynthetic pigment in plant. The level of chlorophyll-a can provide an indication of algae or phytoplankton concentration in marine water. It should be highlighted that the presence of algae / chlorophyll-a in water is generally not harmful. Only their uncontrolled growth as algal bloom or red tide would adversely affect the environment.

9.5.2.8 Algal bloom or red tide could lead to indirect water quality impacts such as oxygen depletion because the water can become completely deprived of oxygen when a bloom declines rapidly, since the biological degradation of dead algal material consumes large amounts of oxygen. Although the primary concern from algal blooms is oxygen depletion, a minority (about 10%) of blooms consist of toxin-producing species that synthesise phycotoxins.

9.5.2.9 It should however be highlighted that red tides are natural phenomena which occur seasonally in both polluted and unpolluted waters EPD’s publication “Marine Water Quality in Hong Kong 2014” refers) and could be induced by many factors other than the availability of nutrients in marine waters (e.g. availability of sunlight, water circulation, temperature and wind conditions etc.). Red tide occurrence would depend on a combination of different factors including flow condition, light penetration, salinity distribution, nutrient concentrations, nutrient ratios and species competition, etc.

9.5.2.10 Tolo Harbour is a shallow landlocked water body with low water exchange rate and poor flushing capacity, which is susceptible to algal formation and accumulation of algae. Thus, the maximum chlorophyll-a levels at all fisheries resources are considered high under the “without Project” condition (Scenario 4) (refer to Appendix 5.05). Operation of this Project (Scenario 5) would reduce the chlorophyll-a concentration in the Harbour and Buffer Subzones of the Tolo Harbour and Channel WCZ. The chlorophyll-a levels predicted at the four FCZs, the potential subzone of Yim Tin Tsai FCZ and the important nursery area for commercial fisheries resources are already considered high under the “without Project” condition (Scenario 4). Implementation of this Project (Scenario 5) would minimise the chlorophyll-a level at the fisheries resources. In comparison with the baseline levels of 18 – 36 µg/L (under Scenario 4), the maximum 5-day moving mean chlorophyll-a predicted during operation of this Project (Scenario 5) would be reduced to 12 – 25 µg/L at the fisheries resources, and thus potentially minimising the risk of red tide in Tolo Harbour.

9.5.2.11 The Project operation will improve the water quality in Tolo Harbour (including the fisheries resources) as compared to the baseline condition. This Project will not cause any unacceptable water quality impact to the Tolo Harbour. This Project will in fact have a positive water quality effect in Tolo Harbour, minimising the pollution level and also the risk of algal bloom in the Tolo Harbour (due to the predicted decrease in the chlorophyll-a and nutrient level) in the long term. No unacceptable water quality impact would be resulted from this Project during the operation phase. Therefore, unacceptable fisheries impacts due to changes in water quality are not expected.

Changes in Water Quality during THEES Maintenance Discharge

9.5.2.12 A continuous THEES maintenance discharge for a period of 4 weeks was simulated under Scenarios 6a and 6b. During the THEES maintenance period, secondarily treated and disinfected effluent would be discharged from both STSTW and TPSTW. Under the water quality model, Scenario 6a represents a possible worst case following existing practice where the THEES maintenance events could be scheduled in March (within the algal blooming season identified in this EIA). Scenario 6b however represents an optimised case recommended under this Project to avoid THEES maintenance in algal blooming season. The water quality modelling results for Scenarios 6a and 6b (with THEES maintenance discharge) are compared with the model results for Scenario 5 (normal Project operation without THEES maintenance) to identify the water quality changes due to the THEES maintenance.

9.5.2.13 The predicted SS level during the maintenance period of THEE tunnel under Scenarios 6a and 6b at Yim Tin Tsai FCZ (2.9 and 2.8 mg/L), Yim Tin Tsai (East) FCZ (1.9 and 1.8 mg/L), potential subzone of Yim Tin Tsai FCZ (2.2 and 2.1 mg/L), Yung Shue Au FCZ and the important nursery area for commercial fisheries resources at Three Fathoms Cove (1.5 mg/L) and Lo Fu Wat FCZ (0.9 mg/L) would be below 50 mg/L (refer to Appendix 5.05). The THEE maintenance would increase the maximum SS level at Yim Tin Tsai FCZ by around 0.1 mg/L (or about 4%) under Scenario 6a as compared to the normal operation of the Project (Scenario 5). No SS elevation is predicted at other fisheries resources under both Scenarios 6a and 6b. Therefore, adverse fisheries impacts due to SS elevation are not expected.

9.5.2.14 According to the modeling results from water quality impact assessment, no exceedance of DO was predicted at Yim Tin Tsai FCZ, Yim Tin Tsai (East) FCZ, potential subzone of Yim Tin Tsai FCZ, Yung Shue Au FCZ and the important nursery area for commercial fisheries resources at Three Fathoms Cove, and Lo Fu Wat FCZ under Scenarios 5, 6a and 6b and would be within the ranges for FCZs (DO: 4 – 8 mg/L) stated in the Environmental Management of Mariculture (AFCD, 2009) (refer to Appendix 5.05). Meanwhile, the TIN levels are similar at the fisheries resources under the Scenarios 5, 6a and 6b. Therefore, adverse fisheries impacts due to oxygen depletion and release of nutrients are not expected.

9.5.2.15 Tolo Harbour is a shallow landlocked water body with low water exchange rate and poor flushing capacity, which is susceptible to algal formation and accumulation of algae. Hence, the maximum chlorophyll-a levels at all fisheries resources under normal operation of the THEES in Ultimate Design Scenario (UDS) (Scenario 5: “without Project”) is already considered high (refer to Appendix 5.05). The chlorophyll-a predicted at the fisheries resources would range from 22 – 79 µg/L under the existing practice of THEES maintenance (Scenario 6a) as compared to the normal situation (Scenario 5) of 12 – 25 µg/L. This Project would optimise the THEES maintenance operation and minimise the chlorophyll-a impacts at the fisheries resources to a range of 12 – 49 µg/L under Scenario 6b. It should be noted that the chlorophyll-a levels mentioned above represent the maximum 5-day running means over the entire 1-year simulation period. The actual chlorophyll-a levels at these fisheries resources would be varying and these highest chlorophyll-a levels would only occur for a short period of times as indicated in the time series plots in Figures 01 – 09 of Appendices 5.04b and 5.04c. The time series plots in Appendices 5.04b and 5.04c also showed that the chlorophyll-a elevations caused by the THEES maintenance discharge would be reversible. The model predicted that the chlorophyll-a levels can return to the condition similar to the baseline levels within about 1.5 months after termination of the effluent bypass under Scenario 6a, whilst Scenario 6b is predicted to have a shorter recovery time of about 2 weeks after the end of the maintenance discharge.

9.5.2.16 This Project would optimise the THEES maintenance discharge and reduce the chlorophyll-a levels at all important fisheries resources identified in Tolo Harbour as compared to the chlorophyll-a increases induced by the existing THEES maintenance practices. This Project would potentially minimise the risk of red tides during the THEES maintenance.

9.5.2.17 It should however be highlighted that red tides are natural phenomena which occur seasonally in both polluted and unpolluted waters and would depend on a combination of different factors including flow condition, light penetration, salinity distribution, nutrient concentrations, nutrient ratios and species competition, etc. (refer to Section 9.5.2.9). Past research studies on long-term water quality data in Hong Kong suggested that, under favourable environmental conditions (e.g. in stagnant water, under calm wind condition and with sufficient light energy), red tide can be trigged at a very low nutrient level. Thus, the THEES maintenance discharge may not be a critical or major factor for triggering red tide in Tolo Harbour.

9.5.2.18 Any potential impacts from red tide or HABs that may arise in the Tolo Harbour is currently managed and responded under the routine red tide monitoring and management protocol and response plan adopted by the Hong Kong government. AFCD is acting as the coordinator of the Red Tide Reporting Network, to receive reports of red tide, conduct investigation and provide warning of the risk associated and appropriate mitigation measures. The objectives of this red tide monitoring programme are to provide coordination of monitoring and response to red tides/HABs and fish kills and to compile and synthesise data necessary to effectively manage fisheries resources, protect human health and the marine ecosystems. In addition, specific water quality monitoring programme and mitigation measures are also recommended under this Project to minimise the potential water quality impacts during the THEES maintenance discharge as presented in Section 5.10.3. With implementation of the recommended mitigation measures and monitoring programme, the potential impacts from the maintenance discharge events would be minimised.

Changes in Water Quality during Emergency Discharge from STSTW

9.5.2.19 During the operation phase, it is assumed that an emergency discharge of primarily treated sewage from the STSTW would occur for a period of 6 hours in case of power or plant failure. According to the water quality modeling results, the short-term discharge under Scenario 7 would not cause significant impact upon the predicted mean SS, DO, TIN and chlorophyll-a levels at the fisheries resources as compared to the normal plant operation under Scenario 5 (refer to Appendix 5.05). Therefore, unacceptable fisheries impacts are not expected.

Treated Effluent Reuse

9.5.2.20 Reuse of treated effluent from the Project by general public is not proposed for irrigation or flushing since it is not an effective option as assessed under this Assignment. Treated effluent from the Project would be limited to non-potable uses inside the plant for polymer preparation and the effluent would subsequently be treated again for discharge and would not contribute to additional pollution load. Thus, no additional impact on the water environment, and hence, no additional fisheries impact will be induced by the proposed treated effluent reuse.

9.5.2.21 The overall evaluation of operation phase fisheries impacts are summarised in Table 9.7.

Table 9.7 Summary of Potential Fisheries Impact during Operation Phase

Criteria	Operation Phase Impact
Nature of Impact	Indirect Impact Normal operation of this Project will not cause any unacceptable water quality impact upon the Tolo Harbour. This Project will in fact have a positive water quality effect in Tolo Harbour (e.g. SS, DO, chlorophyll-a), minimising the pollution level and also the risk of algal bloom in the Tolo Harbour. Changes in water quality (e.g. SS, DO, TIN, chlorophyll-a) are expected during the THEES maintenance discharge from STSTW and TPSTW to Tolo Harbour. No significant changes in water quality parameters are predicted. Although the impact chlorophyll-a levels is high under the existing practice of THEES maintenance (Scenario 6a), the baseline chlorophyll-a levels is already considered high (Scenario 5: “without Project”) as Tolo Harbour is a shallow landlocked water body with low water exchange rate and poor flushing capacity, which is susceptible to algal formation and accumulation of algae. This Project would optimise the THEES maintenance operation and minimise the chlorophyll-a impacts at the fisheries resources (Scenario 6b). In addition, the chlorophyll-a levels can return to the condition similar to the baseline levels within about 1.5 months after termination of the effluent bypass under Scenario 6a, whilst Scenario 6b is predicted to have a shorter recovery time of about 2 weeks after the end of the maintenance discharge. It should be highlighted that the maintenance discharge may not be a critical factor for triggering red tide in Tolo Harbour. The short-term emergency discharge would not cause significant impact upon the predicted mean SS, DO, TIN and chlorophyll-a levels at the fisheries resources as compared to the normal plant operation. With the implementation of specific water quality monitoring programme and mitigation measures, no unacceptable water quality impacts are expected.
Size of Affected Area	Indirect Impact Inner Tolo Harbour and Tolo Channel
Loss of Fisheries Resources / Production	There will be no disturbance to marine or riverbed sediments. No loss of fisheries resources / production is anticipated.
Destruction and Disturbance of Nursery and Spawning Grounds	There will be no direct loss of important nursery and spawning grounds for commercial fisheries species. With the implementation of specific water quality monitoring programme and mitigation measures, no unacceptable impacts on nursery and spawning grounds in Tolo Harbour and Tolo Channel due to changes in water quality are expected.
Impact on Fishing Activity	There will be no disturbance to marine or riverbed sediments. No impact on fishing activity is anticipated.
Impact on Aquaculture Activity	Minor. Normal operation of this Project will not cause any unacceptable water quality impact upon the Tolo Harbour. This Project will in fact have a positive water quality effect in Tolo Harbour (e.g. SS, DO, chlorophyll-a), minimising the pollution level and also the risk of algal bloom in the Tolo Harbour. Changes in water quality (e.g. SS, DO, TIN, chlorophyll-a) are expected during the THEES maintenance discharge from STSTW and TPSTW to Tolo Harbour. No significant changes in water quality parameters are predicted. Although the impact chlorophyll-a levels is high under the existing practice of THEES maintenance (Scenario 6a), the baseline chlorophyll-a levels is already considered high (Scenario 5) as Tolo Harbour is a shallow landlocked water body with low water exchange rate and poor flushing capacity, which is susceptible to algal formation and accumulation of algae. This Project would optimise the THEES maintenance operation and minimise the chlorophyll-a impacts at the fisheries resources (Scenario 6b). In addition, the chlorophyll-a levels can return to the condition similar to the baseline levels within about 1.5 months after termination of the effluent bypass under Scenario 6a, whilst Scenario 6b is predicted to have a shorter recovery time of about 2 weeks after the end of the maintenance discharge. It should be highlighted that the maintenance discharge may not be a critical factor for triggering red tide in Tolo Harbour. The short-term emergency discharge would not cause significant impact upon the predicted mean SS, DO, TIN and chlorophyll-a levels at the fisheries resources as compared to the normal plant operation. With the implementation of specific water quality monitoring programme and mitigation measures, no unacceptable water quality impacts are expected.
Overall Fisheries Impact	Minor

9.5.2.22 In summary, there will be no loss of fishing ground. Based on the water quality modeling, no unacceptable water quality impacts are expected during the construction and operation phase. Any indirect water quality impacts would be temporary and reversible. The overall fisheries impact is expected to be minor during the construction and operation phase.

9.6 Mitigation of Adverse Environmental Impacts

9.6.1.1 According to the guidelines in Annex 17 of EIAO-TM, the general policy for alleviating fisheries impacts in order of priority are avoidance, minimisation and compensation.

Avoidance

9.6.1.2 Potential impacts on fisheries resources and fishing operations arising from the Project have been avoided and minimised by selecting Option 1B (construction of the connection pipes to existing to emergency outfall of STSTW by trenchless method underneath Shing Mun River) of emergency outfall with the least water quality impact. In addition, the temporary effluent bypass event would be arranged within the regular THEES maintenance windows. Therefore, additional water quality impact and fisheries impact from changes of water quality have been avoided. Furthermore, the THEES maintenance discharge would avoid the blooming season of algae (i.e. January to May) to minimise the potential water quality impacts. It is recommended that any THEES maintenance period should be shortened as far as possible

Minimisation

9.6.1.3 Mitigation measures recommended in the water quality impact assessment for controlling water quality impact will also serve to protect fisheries from indirect impacts and ensure no unacceptable impact on fisheries resources and operations. For more detailed mitigation measures regarding water quality refer to Sections 5.7.2 and 5.13.2 of the EIA Report.

9.6.1.4 Relevant government departments including EPD, WSD and AFCD as well as key stakeholders for mariculture and fisheries in Tolo Harbour should be informed prior to the THEES maintenance / emergency discharge events.

9.7 Evaluation of Residual Impacts

9.7.1.1 There will be no loss of fishing ground arising from the Project. The residual impacts would be the indirect water quality impacts on the nearby fisheries resources. No additional water quality impact, and hence, no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works during construction phase. The Project would not cause any unacceptable water quality impact to Tolo Harbour during normal operation of the Project. The water quality impact associated with the THEES maintenance discharge and emergency discharge would be short-term and reversible. No unacceptable water quality impact is expected from these temporary discharges provided that all the recommended mitigation measures are properly implemented. Therefore, no unacceptable residual impacts on fisheries resources due to water quality deterioration expected.

9.8 Environmental Monitoring and Audit (EM&A)

9.8.1.1 No unacceptable residual fisheries impact is expected from the Project. No monitoring program specific for fisheries is required. However, monitoring of water quality parameters would be required to ensure the effectiveness of the mitigation measures.

9.8.1.2 The potential water quality impact from the land-based construction works can be controlled by the recommended mitigation measures. Regular site inspections should be undertaken during the construction phase to inspect the construction activities and works areas in order to ensure the recommended mitigation measures are properly implemented. Details of the EM&A programme are presented in the standalone EM&A Manual.

9.8.1.3 During normal plant / THEES operation, monitoring of the treated effluent quality from the CSTW should be carried out in accordance with the WPCO license to ensure that the effluent quality would comply with the design standards, which is under the ambit of RO of EPD.

9.8.1.4 Marine water quality monitoring is recommended in Tolo Harbour for THEES maintenance during both construction and operational phases of this Project. Marine water quality parameters such as SS, BOD, E.coli, chlorophyll-a, TIN, UIA and NH₃-N should be monitored. A seven-month baseline monitoring programme covering the period from June to December (outside the algae blooming season) is proposed at a frequency of twice per month to establish the baseline water quality conditions at selected monitoring points. In case of THEES maintenance during the construction and operational phases of this Project, marine water quality in Tolo Harbour should be monitored at a frequency of 3 times per week throughout the maintenance period until the baseline water quality is restored or at least 1 month after termination of the effluent bypass (whichever is longer).

9.8.1.5 The monitoring programme for THEES maintenance during the construction and operational phase of this Project as discussed above shall continue in the first 3 years after commissioning of this Project. After 3 years of post-Project commission period, a review shall be conducted by DSD to determine whether such monitoring shall be continued. The review results shall be submitted to EPD, AFCD, WSD and other relevant parties. Any amendment on the monitoring programme shall be agreed by EPD, AFCD and WSD. Details of the monitoring programme and an event and action plan for the THEES maintenance are provided in the standalone EM&A Manual.

9.8.1.6 Marine water quality monitoring is also recommended in Tolo Harbour for emergency discharge during operational phase of this Project. Marine water quality parameters such as SS, BOD, E.coli, chlorophyll-a, TIN, UIA and NH₃-N should be monitored. A one-year baseline monitoring programme covering both dry and wet seasons is proposed at a frequency of twice per month to establish the baseline water quality conditions at selected monitoring points. In case of emergency discharge during the operational phase of this Project, marine water quality in Tolo Harbour should be monitored daily throughout the emergency discharge period until the baseline water quality is restored or at least 2 weeks after termination of the discharge (whichever is longer).

9.8.1.7 The monitoring programme for emergency discharge during the operational phase of this Project as discussed above shall continue in the first 3 years after commissioning of this Project. After 3 years of post-Project commission period, a review shall be conducted by DSD to determine whether such monitoring shall be continued. The review results shall be submitted to EPD, AFCD, WSD and other relevant parties. Any amendment on the monitoring programme shall be agreed by EPD, AFCD and WSD. Details of the monitoring programme and an event and action plan for the emergency discharge are provided in the standalone EM&A Manual.

9.9 Environmental Benefits

9.9.1.1 The Project operation will improve the water quality in Tolo Harbour as compared to the “without Project” condition. This Project will not cause any unacceptable water quality impact upon the Tolo Harbour. This Project will in fact have a positive water quality effect in Tolo Harbour, minimising the pollution level and thus potentially reduce the risk of algal bloom in the Tolo Harbour (due to the predicted decrease in the chlorophyll-a and nutrient level) in the long term.

9.10 Conclusion

9.10.1.1 A study based on existing information on commercial fisheries resources and fishing operations within the waters of the assessment area has been undertaken, following the criteria and guidelines for evaluating and assessing fisheries impact as stated in Annexes 9 and 17 of the EIAO-TM. Sites of fisheries importance have been identified, where present.

9.10.1.2 No important spawning or nursery grounds were identified in the immediate vicinity of the existing STSTW, while the nearest important nursery area for commercial fisheries resources is located in Three Fathoms Cove in Tolo Channel (approximately 6.5 km from the existing STSTW). The nearest FCZs (Yim Tin Tsai FCZ and Yim Tin Tsai (East) FCZ) are located approximately 4.5 km away from the existing STSTW. The importance of capture fisheries resources in the vicinity of the existing STSTW was identified as low in terms of both production weight and value. Fish fry production was low in the immediate vicinity of the existing STSTW in Tolo Harbour.

9.10.1.3 The Project will only involve land-based construction works. There will be no disturbance to marine or riverbed sediments. Under the Project design, any Project effluent bypass to the Tolo Harbour will be discharged separately through the existing emergency outfall of the TPSTW and STSTW. Construction of the connection pipes to existing emergency outfall of STSTW by trenchless method underneath Shing Mun River is proposed. The construction method would not cause disturbance to the marine sediment. With the adoption of trenchless method, no loss of fishing ground is anticipated.

9.10.1.4 During the construction phase, THEES connection works required for this Project will be synchronized with the THEES maintenance windows. As such, no additional water quality impact, and hence, no additional fisheries impact from changes of water quality will be induced by the proposed THEES connection works. Indirect fisheries impacts due to deterioration of water quality are expected during operation phase. Changes in water quality (e.g. SS, DO, TIN, chlorophyll-a) at Yim Tin Tsai FCZ, Yim Tin Tsai (East) FCZ, potential subzone of Yim Tin Tsai FCZ, Yung Shue Au FCZ, Lo Fu Wat FCZ and the important nursery area for commercial fisheries resources at Three Fathoms Cove are expected during operation phase (i.e. discharge of effluent to Tolo Harbour during the maintenance of THEES tunnel; and emergency discharge of primarily treated sewage from the CSTW). However, no significant changes in water quality parameters are predicted. No unacceptable water quality impacts are expected. With the implementation of mitigation measures for water quality, no unacceptable fisheries impacts are expected.

9.11 References

Agriculture, Fisheries and Conservation Department (2009). Environmental Management of Mariculture. Agriculture, Fisheries and Conservation Department, the Government of the Hong Kong Special Administrative Region.

Agriculture, Fisheries and Conservation Department (2001). Final Report. Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment. Prepared by Centre for Coastal Pollution and Conservation, City U Professional Services Limited for Agriculture, Fisheries and Conservation Department, The Government of the Hong Kong Special Administrative Region.

Agriculture, Fisheries and Conservation Department (2002). Agriculture, Fisheries and Conservation Department Annual Report 2001-2002.

Agriculture, Fisheries and Conservation Department (2003). Agriculture, Fisheries and Conservation Department Annual Report 2002-2003.

Agriculture, Fisheries and Conservation Department (2004). Agriculture, Fisheries and Conservation Department Annual Report 2003-2004.

Agriculture, Fisheries and Conservation Department (2005). Agriculture, Fisheries and Conservation Department Annual Report 2004-2005.

Agriculture, Fisheries and Conservation Department (2006). Agriculture, Fisheries and Conservation Department Annual Report 2005-2006.

Agriculture, Fisheries and Conservation Department (2007). Agriculture, Fisheries and Conservation Department Annual Report 2006-2007.

Agriculture, Fisheries and Conservation Department (2008). Agriculture, Fisheries and Conservation Department Annual Report 2008-2009.

Agriculture, Fisheries and Conservation Department (2009). Agriculture, Fisheries and Conservation Department Annual Report 2008-2009.

Agriculture, Fisheries and Conservation Department. (2010). Agriculture, Fisheries and Conservation Department Annual Report 2009-2010.

Agriculture, Fisheries and Conservation Department (2011). Agriculture, Fisheries and Conservation Department Annual Report 2010-2011.

Agriculture, Fisheries and Conservation Department (2012). Agriculture, Fisheries and Conservation Department Annual Report 2011-2012.

Agriculture, Fisheries and Conservation Department (2013). Agriculture, Fisheries and Conservation Department Annual Report 2012-2013.

Agriculture, Fisheries and Conservation Department (2014). Agriculture, Fisheries and Conservation Department Annual Report 2013-2014.

Agriculture, Fisheries and Conservation Department (2015a). Fisheries: Aquaculture.http://www.afcd.gov.hk/english/fisheries/fish_aqu/fish_aqu_mpo/fish_aqu_mpo.html

Agriculture, Fisheries and Conservation Department. (2015b) Fisheries: Capture Fisheries.http://www.afcd.gov.hk/english/fisheries/fish_cap/fish_cap_latest/fish_cap_latest.html

Civil Engineering and Development Department (2013). Agreement No. CE 43/2008(HY) Cross Bay Link, Tseung Kwan O – Investigation. Environmental Impact Assessment Report.

Drainage Services Department (2014). Relocation of Sha Tin Sewage Treatment Works to Caverns – Feasibility Study – Preliminary Environmental Report. Prepared by AECOM Asia Co. Ltd. for Drainage Services Department, The Government of the Hong Kong Special Administrative Region.

Environmental Resources Management (1998). Fisheries Resources and Fishing Operation in Hong Kong Waters. Prepared by ERM for Agriculture and Fisheries Department, HK SAR Government.

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