5.                  WATER QUALITY IMPACT

 

In accordance with the recommendations of the EIA, mitigation measures have been proposed during the construction phase of the Project.  Details of the mitigation measures are presented in Appendix E - Implementation Schedule.

 

In accordance with the recommendations of the EIA, water quality EM&A is required during dredging and sandfilling activities.  In addition, baseline water quality monitoring will be required prior to the commencement of construction activities.  The following Section provides details of the water quality monitoring to be undertaken by the ET to verify the distance of sediment plume dispersion and to identify whether the potential exists for any indirect impacts to occur to ecological sensitive receivers.  The water quality monitoring programme will be carried out to ensure that any deteriorating water quality is readily detected and timely action taken to rectify the situation.  The status and locations of water quality sensitive receivers and the marine works location may change after issuing this Manual.  If required, the ET in consultation with the Contractor(s) will propose updated monitoring locations and seek approval from the ER, the IEC and EPD.

 

5.1      Construction Phase

 

Water Quality Parameters Measurements of Dissolved Oxygen (DO) concentration (mg L-1), DO saturation (%), Salinity (mg L-1), Temperature (ºC) and Turbidity (NTU) will be taken in situ by the ET at monitoring stations identified below.  Water samples for the measurements of SS (mg L-1) and chlorophyll-a (µg L-1) will also be collected for laboratory analysis.  In addition to the water quality parameters, other relevant data will also be measured and recorded in Water Quality Monitoring Logs (Appendix C), including the location of the sampling stations, water depth, time, weather conditions, sea conditions, tidal stage, current direction and speed, special phenomena and work activities undertaken around the monitoring and works area that may influence the monitoring results.  Observations on any special phenomena and work underway at the construction site at the time of sampling will also be recorded.

 

For water quality monitoring, the following equipment will be supplied and used by the ET.  The use of similar equipment is subject to prior approval from the IEC.

 

5.1.1       Monitoring Equipment and Methodology

 

For water quality monitoring, the following equipment should be supplied and used by the environmental contractor.

·       Dissolved Oxygen and Temperature Measuring Equipment - The instrument should be a portable, weatherproof dissolved oxygen measuring instrument complete with cable, sensor, comprehensive operation manuals, and should be operable from a DC power source.  It should be capable of measuring: dissolved oxygen levels in the range of 0–20 mg L-1 and 0-200% saturation; and a temperature of 0-45 degrees Celsius.

　

It should have a membrane electrode with automatic temperature compensation complete with a cable of not less than 35 m in length.  Sufficient stocks of spare electrodes and cable should be available for replacement where necessary (for example, YSI model 59 meter, YSI 5739 probe, YSI 5795A submersible stirrer with reel and cable or an approved similar instrument).

 

·         Turbidity Measurement Equipment – The instrument shall be a portable, weatherproof turbidity-measuring instrument complete with comprehensive operation manual.  The equipment shall use a DC power source.  It shall have a photoelectric sensor capable of measuring turbidity between 0-1000 NTU (e.g. Hach model 2100P or an approved similar instrument).

 

·         Salinity Measurement Instrument - A portable salinometer capable of measuring salinity in the range of 0-40 ppm should be provided for measuring salinity of the water at each monitoring location.

 

·         Water Depth Detector - A portable, battery-operated echo sounder should be used for the determination of water depth at each designated monitoring station.  A detector affixed to the bottom of the work boat, if the same vessel is to be used throughout the monitoring programme, is preferred.

 

·         Current Velocity and Direction – No specific equipment is recommended for measuring the current velocity and direction.  However, the contractor should seek approval of their proposed equipment with the client prior to deployment.

 

·         Positioning Device - A hand-held or boat-fixed type digital Global Positioning System (GPS) with way point bearing indication or other equipment instrument of similar accuracy, should be provided and used during water quality monitoring to ensure the monitoring vessel is at the correct location before taking measurements.  GPS or the equivalent instrument, calibrated at appropriate checkpoint (e.g. Quarry Bay Survey Nail at Easting 840683.49, Northing 816709.55) should be provided and used to ensure the monitoring station is at the correct position before taking measurement and water samples.

 

·         Water Sampling Equipment - A water sampler, consisting of a transparent PVC or glass cylinder of not less than two litres, which can be effectively sealed with cups at both ends, should be used (Kahlsico Water Sampler 13SWB203 or an approved similar instrument).  The water sampler should have a positive latching system to keep it open and prevent premature closure until released by a messenger when the sampler is at the selected water depth.

 

All in situ monitoring instruments should be checked, calibrated and certified by a laboratory accredited under HOKLAS or any other international accreditation scheme before use, and subsequently re-calibrated at monthly intervals throughout all stages of the water quality monitoring.  Responses of sensors and electrodes should be checked with certified standard solutions before each use. 

 

For the on-site calibration of field equipment, the BS 1427: 1993, Guide to Field and On-Site Test Methods for the Analysis of Waters should be observed.  Sufficient stocks of spare parts should be maintained for replacements when necessary.  Backup monitoring equipment should also be made available so that monitoring can proceed uninterrupted even when equipment is under maintenance, calibration etc.

 

Water samples for SS and chlorophyll-a measurements should be collected in high density polythene bottles, packed in ice (cooled to 4° C without being frozen), and delivered to a HOKLAS laboratory as soon as possible after collection.

 

All laboratory work should be carried out in a HOKLAS accredited laboratory.  Water samples of about 1,000 mL should be collected at the monitoring and control stations for carrying out the laboratory determinations.  The determination work should start within the next working day after collection of the water samples.  The analyses shall commence within 24 hours after collection of the water samples. The analyses should follow the standard methods as described in APHA Standard Methods for the Examination of Water and Wastewater, 19th Edition or later, unless otherwise specified (APHA 2540D for SS).

 

The submitted information should include pre-treatment procedures, instrument use, Quality Assurance/Quality Control (QA/QC) details (such as blank, spike recovery, number of duplicate samples per-batch etc), detection limits and accuracy.  The QA/QC details should be in accordance with requirements of HOKLAS or another internationally accredited scheme.                  

 

5.1.2     Monitoring Stations

 

The monitoring station locations have been established to identify potential impacts to water quality sensitive receivers which are shown in Figure 5.1.

 

Prior to, during and after the dredging and sandfilling works, water quality sampling will be undertaken at stations situated around the dredging area and at the sensitive receivers.  The monitoring at those stations is to ensure the dredging and sandfilling works of the Project will not cause deterioration in water quality outside the impact (mixing) zone, in particularly at the nearby sensitive areas (shown in Figure 5.1).

 

·         R1 is a Reference Station located to the south of the dredging/sandfilling area, which is not supposed to be impacted by the dredging/sandfilling works.  R1 is a representative station for the background water quality for Tolo Harbour as it is at the channel where the water exchange between the enclosed Plover Cove and Tolo Harbour take place;

 

·         R2 is a Reference Station located to the southwest of the dredging/sandfilling area, which is not supposed to be impacted by the dredging/sandfilling works. R2 is a representative station for the background water quality in the Plover Cove region;

 

·         I1, I2 and I3 are the Impact Stations just outside the mixing zone, which is unlikely to be impacted by the dredging/sandfilling works;

·         FCZ1 represents the Sensitive Receiver located at the Yim Tin Tsai East Fish Culture Zone, which is about 1.5 km to the southwest of the dredging/sandfilling area.  Deterioration of water quality at this station is not anticipated;

 

·         M1 represents the Sensitive Receiver located at the Ting Kok SSSI, which is about 800 m to the west of the dredging/sandfilling area.  Deterioration of water quality at this station is not anticipated;

 

·         W1 represents the Sensitive Receiver located at the Water Sport Centre, which is about 250 m to the southeast of the dredging/sandfilling area, which is unlikely to be impacted by the dredging/sandfilling works.

 

·         G1 is the Gradient Station to assist in the identification of the source of any impact.

 

The suggested co-ordinates of these monitoring stations are listed in Figure 5.1.

 

The monitoring stations will be sampled during Baseline Monitoring (prior to the dredging works), Impact Monitoring (during dredging and sandfilling works) and Post Construction Monitoring (after completion of sandfilling work).

 

5.1.3   Monitoring Frequency

 

For baseline, impact and post-project monitoring, monitoring should be undertaken 3 days per week, at mid-flood and mid-ebb tides, with sampling/ measurement at the designated stations.  The intervals between 2 consecutive sets of monitoring should not be less than 36 hours except where there are exceedances of Action and/or Limit Level, in which case monitoring frequency should be increased.  The tidal range for each of the flood and ebb tide should not be less than 0.5m.

 

The water quality sampling will be undertaken within a 3-hour window of 1.5 hour before and 1.5 hour after mid flood and mid-ebb tides.  The Environmental Team will be responsible for liaison with the engineering contractor to confirm whether dredging/sandfilling works are being undertaken during the water quality sampling.

 

Measurements shall be taken at 3 water depths: 1m below water surface, mid-depth and 1m above sea bed, except where the water depth less than 6m, the mid-depth station may be omitted.  Should the water depth be less than 3m, only the mid-depth station will be monitored.  The ET Leader shall seek approval from the IEC and DEP on all the monitoring stations.

 

Replicates in-situ measurements and samples collected from each independent sampling event are required for all parameters to ensure a robust statistically interpretable dataset.

 

5.1.4   Baseline Monitoring

 

Baseline Monitoring will comprise sampling 3 days a week, at mid-flood and mid-ebb tides, for at least 4 weeks prior to the commencement of the dredging works.  There shall not be any marine construction activities in the vicinity of the monitoring stations during the baseline monitoring. The monitoring will be undertaken at the specified eight stations in total, as shown in Figure 5.1.  The intervals between 2 consecutive sets of monitoring should not be less than 36 hours.  The baseline monitoring schedule should be provided to EPD for agreement at least 2 weeks prior to commencement of the baseline monitoring work.

 

5.1.5   Impact Monitoring

　

Impact Monitoring will comprise sampling 3 days a week, at mid-flood and mid-ebb tides, during the dredging and sandfilling works.  The monitoring will be undertaken at the specified eight stations as the Baseline Monitoring stations, as shown in Figure 5.1.  The intervals between 2 consecutive sets of monitoring should not be less than 36 hours except where there are exceedances of Action and/or Limit Levels, in which case the monitoring frequency may be increased.  The monitoring results should be included in the EM&A reports.

 

5.1.6   Post-Project Monitoring

 

Upon the completion of the sandfilling works, Post-project Monitoring shall be conducted for 4 weeks in the same manner as the Baseline Monitoring.

5.1.7   Compliance / Action Event Plan

 

Water quality monitoring results will be evaluated against Action and Limit levels shown in Table 5.1.

 

Table 5.1         Action and Limit Levels for Water Quality (based on the Results of the Baseline Report)

Parameter

Action Level

Limit Level

SS in mg L-1

(depth-averageda)c

　

 95%-ile of baseline data, or 20% exceedance of value at any impact station and sensitive receiver compared with corresponding data from reference stations at the same tide of the same day 99%-ile of baseline data, or 30% exceedance of value at any impact station and sensitive receiver compared with corresponding data from reference stations at the same tide of the same day and specific sensitive receiver water quality requirements

Chlorophyll-a in µg

L-1c

Surface, Middle and Bottom

95%-ile of baseline data

Surface, Middle and Bottom

10µg L-1 or 99%-ile of baseline data

DO in mg L-1 bd

Surface and Middle

5%-ile of baseline data for surface and middle layer

Bottom

5%-ile of baseline data for bottom  layers

Surface, Middle

4mg L-1or 1%-ile of baseline for surface and middle layer

Bottom

2mg L-1or 1%-ile of baseline data for bottom layer

Turbidity in NTU      (depth-averageda)c

 95%-ile of baseline data, or 20% exceedance of value at any impact station and sensitive receiver compared with corresponding data from reference stations at the same tide of the same day 99%-ile of baseline data, or 30% exceedance of value at any impact station and sensitive receiver compared with corresponding data from reference stations at the same tide of the same day

Notes:

(a)                “Depth-averaged” is calculated by taking the arithmetic means of reading of all three depths.

(b)                For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.

(c)                For SS, chlorophyll-a and turbidity, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.

(d)                Both Action and Limit Levels for DO (surface and middle) in the FCZ1(Figure 5.1) are less than 5 mg L-1.

 

 It should be noted that all Action/Limit levels presented in Table 5.1 may be revised based on the baseline data to be collected in advance of construction works.  If deemed necessary, the ET in consultation with the Contractor(s) will propose revised Action Limit levels and seek approval from ER, the IEC and EPD.

 

Actions to be taken in the event that the Action or Limit Levels are exceeded are shown in Table 5.2.

Table 5.2   Event and Action Plan for Water Quality

EVENT

ACTION

ET

IEC

ER

Contractor

Action Level being exceeded by one sampling day

1.        Repeat in-situ measurement to confirm findings;

2.        Identify source(s) of impact;

3.        Inform the IEC and the Contractor;

4.        Check monitoring data, all plant, equipment and the Contractor’s working methods;

5.        Discuss mitigation measures with the IEC and the Contractor;

 

1.     Discuss with the ET and the Contractor on the mitigation measures;

2.     Review proposals on mitigation measures submitted by the Contractor;

3.     Assess the effectiveness of the implemented mitigation measures.

1.     Discuss with the IEC on the proposed mitigation measures;

2.     Make agreement on the mitigation measures to be implemented.

1.         Inform the ER and confirm notification of the non-compliance in writing;

2.         Rectify unacceptable practice;

3.         Check all plant and equipment;

4.         Consider changes of working methods;

5.         Discuss with the ET the IEC and propose mitigation measures to the IEC and ER;

6.         Implement the agreed mitigation measures.

　

Action Level being exceeded by more than one consecutive sampling days

1.      Repeat in-situ measurement to confirm findings;

2.      Identify source(s) of impact;

3.      Inform the IEC and the Contractor;

4.      Check monitoring data, all plant, equipment and Contractor’s working methods;

5.      Discuss mitigation measures with the IEC and the Contractor;

6.      Ensure mitigation measures are implemented;

 

1.   Discuss with the ET and the Contractor on the mitigation measures;

2.   Review proposals on mitigation measures submitted by the Contractor accordingly;

3.   Assess the effectiveness of the implemented mitigation measures.

1.      Discuss with the IEC on the proposed mitigation measures;

2.      Make agreement on the mitigation measures to be implemented;

3.      Assess effectiveness of the implemented mitigation measures.

1.         Inform the ER and confirm notification of the non-compliance in writing;

2.         Rectify unacceptable practice;

3.         Check all plant and equipment;

4.         Consider changes of working methods;

5.         Discuss with the ET and the IEC and propose mitigation measures to the IEC and ER within 3 working days;

6.         Implement the agreed mitigation measures.

　

Limit Level being exceeded by one consecutive sampling day

1.      Repeat in-situ measurement to confirm findings;

2.      Identify source(s) of impact;

3.      Inform the IEC, the Contractor and the DEP;

4.      Check monitoring data, all plant, equipment and the Contractor’s working methods;

5.      Discuss mitigation measures with the IEC, the ER and the Contractor;

6.      Ensure mitigation measures are implemented.

 

1.     Discuss with the ET / Contractor on the mitigation measures;

2.     Review proposals on mitigation measures submitted by the Contractor and advise the ER accordingly;

3.     Assess the effectiveness of the implemented mitigation measures.

1.     Discuss with the IEC, the ET and the Contractor on the proposed mitigation measures;

2.     Request the Contractor to critically review the working methods;

3.     Make agreement on the mitigation measures to be implemented;

4.     Assess the effectiveness of the implemented mitigation measures.

1.         Inform the ER and confirm notification of the non-compliance in writing;

2.         Rectify unacceptable practice;

3.         Check all plant and equipment;

4.         Consider changes of working methods;

5.         Discuss with the ET, the IEC and the ER and propose mitigation measures to the IEC and the ER within 3 working days;

6.         Implement the agreed mitigation measures.

　

Limit Level being exceeded by more than one consecutive sampling days

1.       Repeat in-situ measurement to confirm findings;

2.       Identify source(s) of impact;

3.       Inform the IEC, the Contractor and DEP;

4.       Check monitoring data, all plant, equipment and Contractor’s working methods;

5.       Discuss mitigation measures with the IEC, the ER and the Contractor;

6.       Ensure mitigation measures are implemented;

　

　

 

1.        Discuss with ET and Contractor on the mitigation measures;

2.        Review proposals on mitigation measures submitted by the Contractor and advise the ER accordingly;

3.        Assess the effectiveness of the implemented mitigation measures.

1.     Discuss with the IEC, the ET and the Contractor on the proposed mitigation measures;

2.     Request Contractor to critically review working methods;

3.     Make agreement on the mitigation measures to be implemented;

4.     Assess effectiveness of the implemented mitigation measures;

5.     Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the marine work until no exceedance of Limit Level.

1.         Inform the ER and confirm notification of the non-compliance in writing;

2.         Rectify unacceptable practice;

3.         Check all plant and equipment;

4.        Consider changes of working methods;

5.       Discuss with the ET, the IEC and the ER and propose mitigation measures to the IEC and the ER within 3 working days;

6.        Implement the agreed mitigation measures;

7.        As directed by the ER, slow down or stop all or part of the construction activities.

　

 

5.2      Post-Construction Phase

 

The Post-Construction Phase is defined as after completion of construction works but before the operation of the beach. No sewage and wastewater generated from the beach building facilities will be discharged into the beach or marine environment, water quality impact due to sewage and wastewater discharge from the beach building facilities is not anticipated (refer to EIA Report Section 6).

 

5.2.1        E. coli Monitoring

 

Monitoring for E. coli is recommended at the outfall of the eastern culvert and western channel within six weeks after the completion of construction works.  The purpose of the monitoring is to investigate the characteristics of E. coli  loading in the box culvert/channel and to establish relationship with E. coli levels at the beach.  Samples will be collected at the locations specified in Figure 5.2 at/near the outlet of the outfall when no influx of seawater occur (e.g. during low tide).  During the same tide, E. coli samples should be collected at EPD’s routine beach monitoring stations.  The sampling team should confirm the locations of EPD’s routine monitoring stations prior to the commencement of any sampling events.  In some occasions, it is not practicable to take the samples at EPD’s routine monitoring stations, for example, the water is too shallow.  Then the sampling team should determine the nearest sampling locations which should be as close to EPD’s stations as possible.  The coordinates of all the sampling locations should be recorded. 

 

E. coli samples should be stored in cool box (4°C) during the sampling and transportation and should be delivered to the HOKLAS accredited laboratory, or equivalent, to determine the E. coli  content in the sample. 


Other water quality parameters, i.e., pH, Dissolved Oxygen (DO) concentration (mg L-1), DO saturation (%), Salinity (mg L-1), Temperature (ºC) and Turbidity (NTU) should be taken in situ by the sampling team at same monitoring stations as for E.Coli measurements.  Observations such as and weather and beach conditions, should also be recorded.

 

Sampling should be conducted twice per week within six weeks after the completion of construction works. 

　

5.2.2        Progress of DSD's Village Sewerage Projects

　

Implementation programme of the village sewerage projects should be monitored to achieve the target sewerage connection rate to communal sewers before the beach is put into operation.

　

5.3      Operational Phase 

 

5.3.1        Routine Monitoring of Beach Water Quality

 

EPD has well established a comprehensive water quality monitoring programme for all gazetted beaches to detect any deterioration of beach water quality, which will also be implemented in this Lung Mei bathing beach. 

　

EPD's current monitoring programme requires all gazetted beaches are monitored at least three times per month during bathing seasons. During non-bathing seasons, gazetted beaches are monitored once per month. The monitoring data assists to detect any deterioration of beach water quality. In case the beach water quality tends to be deteriorated, EPD will continue monitoring of the beach water quality and provide Leisure and Cultural Services Department (LCSD) the monitoring data.  In case the beach water quality tends to be deteriorated, LCSD will decide the most appropriate method of improving the beach water quality.

　

In case the beach water quality at Lung Mei tends to be deterioriated and becomes not desirable for swimming, LCSD will close the beach temporarily until the beach water quality becomes suitable for swimming. EPD will continue monitoring the beach water quality and provide LCSD the monitoring results.  

　

5.3.2        Red Tides

 

In the event of red tide that may occur naturally, similar to the practice adopted for other gazetted beaches by LCSD, Lung Mei beach may be closed to swimmers in accordance with the relevant procedures.