Contents

1                      intROduction                                                                          

1.1                   Background                                                                           

1.2                   Purpose of the Report                                                     

1.3                   Structure of the Report                                                

2                      Baseline Water quality monitoring Methodology 

2.1                   Monitoring Locations                                                       

2.2                   Monitoring Parameters and Frequency                 

2.3                   Monitoring Equipment and Methodology               

3                      Baseline Water Quality Monitoring Results        

3.1                   Introduction                                                                          

3.2                   Water Quality Monitoring Results                            

4                      Conclusion                                                                             

 

LIST OF ANNEXES

 

Annex A

Baseline Monitoring Schedule

 

Annex B

Calibration Reports of Multi-parameter Sensor

 

Annex C

QA/QC Results

 

Annex D

Baseline Water Quality Monitoring Results

 

 

EXECUTIVE SUMMARY

The Hong Kong Civil Engineering and Development Department (CEDD) have undertaken baseline water quality monitoring prior to the commencement of dredging works for Contaminated Mud Pits (CMP 1 and CMP 2) at the South of The Brothers.

This Baseline Monitoring Report has been prepared in compliance with the Environmental Permit (EP-427/2011/A) and the Environmental Monitoring and Audit Manual for the Disposal of Contaminated Sediment – Dredging, Management and Capping of Contaminated Sediment Disposal Facility at the South of The Brothers.

Baseline water quality monitoring was conducted between 26 July and 23 August 2012 at eighteen designated monitoring stations established for the Project.  The monitoring was carried out 3 days per week, at mid-flood and mid-ebb tides, at three depths (surface, middle and bottom), for 5 weeks prior to the commencement of dredging works.  No major activities were noted during baseline monitoring.  Water quality monitoring results are, therefore, representative of the baseline conditions for the Project.

Results have been used to determine Action and Limit Levels for the dissolved oxygen, suspended solids and turbidity for impact monitoring to be conducted during dredging, backfilling and capping activities for the Project and listed in Table I. These Action and Limit Levels will be used for impact monitoring during dredging, backfilling and capping activities to check if there are exceedances of water quality due to the Project.

 

Table I            Proposed Action and Limit Levels of Water Quality for Dredging, Backfilling and Capping Activities

Parameter

Action Level

Limit Level

Dissolved Oxygen (DO) (1)

Surface and Mid-depth (2)

Surface and Mid-depth (2)

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for surface and middle layer = 4.32 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact, WSR 45C and WSR 46 station readings are < 4 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

 

Bottom

Bottom

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for bottom layers = 3.12 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact station, WSR 45C and WSR 46 readings are < 2 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

Depth-averaged Suspended Solids (SS) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data for depth average = 21.60 mg L-1

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data for depth average = 40.10 mg L-1

 

and

 

120% of control station's SS at the same tide of the same day

130% of control station's SS at the same tide of the same day

 

 

 

Depth-averaged Turbidity (Tby) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data = 25.04 NTU

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data = 56.30 NTU

 

and

 

120% of control station's Tby at the same tide of the same day

130% of control station's Tby at the same tide of the same day

 

 

 

Notes:

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

(2)    The Action and Limit Levels for DO for Surface & Middle layers were calculated from the combined pool of baseline surface layer data and baseline middle layer data.

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

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

 

 


1                                            intROduction

The Hong Kong Civil Engineering and Development Department (CEDD) have commissioned ERM-Hong Kong, Ltd (ERM) supported by Mr Peter Whiteside (Independent Consultant), Halcrow China Ltd (HCL) and Professor Wen-Xiong Wang (Independent Auditor) of the Hong Kong University of Science and Technology (HKUST), to undertake the Environmental Monitoring and Audit for Contaminated Mud Pits to the South of The Brothers and at East Sha Chau (2012-2017) – Investigation (hereafter referred as “the Study”).  This Study, awarded under Agreement No. CE 23/2012 (EP), commenced on 5th September 2012.

1.1                                      Background

Since December 1992, the East of Sha Chau area has been the site of a series of dredged contaminated mud pits (CMPs) designed to provide confined marine disposal capacity for contaminated mud arising from the HKSAR’s dredging and reclamation projects.  The latest group of pits, CMP Va, b, c & d began receiving contaminated mud from construction projects on 10 February 2012.  CMP Va is presently in operation for backfilling of contaminated sediments.

Capacity to dispose of contaminated mud is currently predicted to be exhausted in 2015 with the completion of backfilling of CMP Vd at East of Sha Chau (ESC).  When CMP Vd is full, a new environmentally acceptable disposal capacity for essential arisings will be required.  The environmental acceptability of the construction and operation of the CMPs at the South of the Brothers (the Project) had been confirmed by the findings of the associated EIA study completed in 2005 under Agreement No. CE 12/2002(EP) ([1]).  The Director of Environmental Protection (DEP) approved the respective EIA report of this Agreement under the EIAO in September 2005 (EIA Register No.: AEIAR-089/2005).  A detailed EIA Review (the Review) was carried out under Agreement No. FM 2/2009 ([2]) to re-confirm the relevance of the findings of the approved EIA report with respect to the up-to-date information of other concurrent projects in the vicinity or any updated requirements/guidelines and to recommend on the environmental viability of the proposed the South of The Brothers (SB) CMPs.

The Review concluded that relevant findings and recommendations of the approved EIA report in relation to the SB CMPs are still valid.  An information note advising members of the Advisory Council on the Environment (ACE) about the Review outcome was circulated in August 2010 with no further comments received.

An Environmental Permit (EP-427/2011) for Dredging, Management and Capping of Contaminated Sediment Disposal Facility to the South of The Brothers (hereafter referred as “the Project”) was issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 3 November 2011 and varied on 23 December 2011 (EP-427/2011/A).

Under the requirements of Condition 4 of the EP (EP-427/2011/A), an EM&A programme as set out in the Environmental Monitoring and Audit Manual (EM&A Manual) is required to be implemented during construction and operational phases of the SB CMPs.  In accordance with the EM&A Manual, baseline monitoring of water quality is required to be undertaken prior to dredging activities to form the SB CMPs.

1.2                                      Purpose of the Report

The purpose of this Baseline Monitoring Report is to present baseline marine water quality at the designated monitoring locations in the Project and reference areas prior to the commencement of marine dredging works.  These levels will be used as the basis for compliance monitoring during dredging, backfilling and capping activities at the SB CMPs.  This report presents the monitoring requirements, methodologies and results of the baseline marine water quality measurements in accordance with the EM&A Manual.

1.3                                      Structure of the Report

After this introductory section, the remainder of the report is structured as follows:

Section 2 :  Baseline Water Quality Monitoring Methodology

Summarises the water quality monitoring parameters, monitoring programme, monitoring methodology, monitoring frequency and monitoring locations.

 

Section 3 :  Baseline Water Quality Monitoring Results

Presents the monitoring results and establishes the Action and Limit Levels in accordance with the EM&A Manual.

 

Section 4 :  Conclusions

Concludes the representativeness of the baseline monitoring results and observations for the Project.

2                                            Baseline Water quality monitoring Methodology

The following Section provides details of methodology used in the baseline monitoring of water quality prior to the commencement of marine dredging works for the Project.

2.1                                      Monitoring Locations

In accordance with the EM&A Manual, water quality sampling was undertaken at monitoring stations in the vicinity of the new facility at the South of The Brothers and in reference areas (EPD Water Quality Monitoring Stations NM1, 2, 3, 5 and 6) prior to the commencement of marine dredging works.  Locations of the baseline monitoring stations are shown in Figure 2.1.  Co-ordinates of these monitoring stations are listed in Table 2.1.

Table 2.1        Coordinates of Water Quality Monitoring Stations for Baseline Water Quality Monitoring

Monitoring Stations

Easting

Northing

Far Field Stations

 

 

SB-WFA

805787

827951

SB-WFB

806066

816537

Mid Field Stations

 

 

SB-WMA

813001

821559

SB-WMB

818386

822120

Near Field Stations

 

 

SB-WNAA

814847

820043

SB-WNAB

816197

819911

SB-WNBA

813999

819207

SB-WNBB

815505

819019

Reference Stations

 

 

NM1

820256

823214

NM2

816015

823686

NM3

812527

824049

NM5

807707

827244

NM6

807584

820286

Sensitive Receiver Stations

 

 

MW1

823604

823654

THB1

814514

817932

THB2

815873

818035

WSR45C

817431

820211

WSR46

813880

820973

Note: Coordinates are based on Hong Kong 1980 GRID Coordinate System

2.2                                      Monitoring Parameters and Frequency

Baseline water quality monitoring was conducted in accordance with the requirements stated in the EM&A Manual, which are presented below.

2.2.1                                Monitoring Parameters

Parameters measured in situ were:

·           Dissolved Oxygen (mg L-1);

·           Salinity (ppt);

·           pH;

·           Turbidity (NTU);

·           Temperature (°C); and

·           Current Velocity and Direction (ms-1).

Parameters measured in the laboratory were:

·           Suspended Solids (SS) (mg L-1);

·           Ammonia (mg L-1);

·           Total Inorganic Nitrogen (TIN mg L-1);

·           5-Day Biochemical Oxygen Demand (BOD5);

·           Cadmium (mg L-1);

·           Chromium (mg L-1);

·           Copper (mg L-1);

·           Lead (mg L-1);

·           Mercury (mg L-1);

·           Nickel (mg L-1);

·           Silver (mg L-1);

·           Zinc (mg L-1); and

·           Arsenic (mg L-1).

In addition to the water quality parameters, other relevant data were measured and recorded in Water Quality Monitoring Logs, including the location of the sampling stations, water depth, time, weather conditions, sea conditions, tidal stage, special phenomena and work activities undertaken around the monitoring and works area that may influence the monitoring results.

2.2.2                                Monitoring Frequency

Baseline water quality monitoring should be carried out for four weeks, with the frequency of three days per week.  The interval between two sets of monitoring was not less than 36 hours.  In situ measurements and water samples were taken during mid-flood and mid-ebb tidal stages on each sampling occasion.

2.3                                      Monitoring Equipment and Methodology

2.3.1                                Monitoring Equipment

Positioning Device

A Global Positioning System (GPS) was used (C-Nav globally corrected DGPS, GPS 84 datum) during monitoring to ensure the accurate recording of the position of the monitoring vessel before taking measurements.  The instrument calibration was checked by recording a measured position at a previously coordinated location on shore.

Electronic data logging device  

A data logging device capable of storing in situ measurement data was used.  The device was able to read and store the output from all electronic meters used for this project and recorded time and location as measured by the GPS.

In situ Measurement Equipment

The instrument was a portable, weatherproof multi-parameter measuring instrument (YSI 6820) complete with cables, multi-probe sensor, comprehensive operation manuals, and was operable from a DC power source.  It was capable of measuring:

·      turbidity levels between 0-1000 NTU (response of the sensor was checked with certified standard turbidity solutions before the start of measurement);

·      pH of 0 to 14 units with a resolution of 0.01 unit;

·      dissolved oxygen levels in the range of 0 – 50 mg L-1; and 0-500% saturation;

·      temperature of -5 to 45 °C; and,

·      salinity in the range of 0-40 ppt (checked with 30 ppt Salinity solutions before the start of the measurement).

Water Depth Gauge

An echo sounder mounted to the hull of the survey vessel was used to measure water depth. 

Current Velocity

Sea water current velocity was measured using a Workhorse Acoustic Doppler Current Profiler (ADCP) manufactured by Teledyne RD Instruments.  This instrument measured current speed and direction in 1 m vertical increments below the survey vessel, from just below the sea surface to just above the seabed.

Water Sampling Equipment

Water samples for suspended solids measurement were collected by the use of a multi-bottle water sampling system (General Oceanics Inc., Rosette Sampler ROS02), consisting of PVC bottles of more than two litres, which could be effectively sealed with cups at both ends.  The water sampler had a positive latching system to keep it open and prevent premature closure until released by a messenger when the sampler was at the selected water depth.

2.3.2                                Monitoring Methodology

Timing & Frequency

Water quality sampling was undertaken within a 4-hour window of 2 hours before or after mid-flood and mid-ebb tides.  Tidal range for flood and ebb tides was not less than 0.5 m for capturing representative tides.

Reference was made to the predicted tides at Chek Lap Kok, which is the tidal station nearest to the Project site, published on the website of Hong Kong Observatory ([3]).  Based on the predicted water levels at Chek Lap Kok, the baseline water quality monitoring was conducted between 26 July and 23 August 2012, following the schedule presented in Annex A.  It should be noted that on 16 August 2012, monitoring was cancelled due to adverse weather conditions caused by the typhoon Kai Tak which led to the issue of Typhoon Signal No. 8 by the Hong Kong Observatory during the survey time.  As a result, baseline monitoring was undertaken over a period of five (5) weeks during which twelve (12) sampling events were conducted.

Triplicate samples were collected from each of the monitoring events for in situ measurements and laboratory analysis.

Depths

Each station was sampled and measurements were taken at three depths, 1 m below the sea surface, mid depth and 1 m above the sea bed.  Where the water depth was less than 6 m, the mid-depth station was omitted.  For stations that were less than 3 m in depth, only the mid depth sample was taken.

Protocols

The multi-parameter measuring instruments (YSI 6820) were checked and calibrated by an HOKLAS accredited laboratory before use (see calibration reports in Annex B).  Onsite calibration was also carried out to check the responses of sensors and electrodes using certified standard solutions before each use.  Sufficient stocks of spare parts were maintained for replacements when necessary, and backup monitoring equipment was made available.

Water samples were collected in high density polythene bottles, packed in ice (cooled to 4° C without being frozen), and delivered to HOKLAS accredited laboratory as soon as possible after collection for immediate analysis.

Laboratory Analysis

All laboratory work was carried out by HOKLAS accredited laboratory.  Water samples were collected at the monitoring and reference stations for carrying out the laboratory determinations.  The determination work started within the next working day after collection of the water samples. 

For laboratory analysis, the Quality Assurance / Quality Control (QA/QC) details were in accordance with requirements of HOKLAS or another internationally accredited scheme (details refer to Annex C).

3                                            Baseline Water Quality Monitoring Results

3.1                                      Introduction

This Section presents the results of the baseline monitoring of water quality for the Project.

3.2                                      Water Quality Monitoring Results

Monitoring data and graphical presentations are summarised in Annex D. 

No major activities influencing the water quality were identified during the monitoring period.

The Action and Limit Levels for DO, turbidity and SS were set in the EM&A Manual and the proposed Action and Limit Levels were determined as shown in Table 3.1.

The Action and Limit Levels of DO, turbidity and SS are derived from the baseline monitoring data for all stations, and the results are presented in Table 3.2.

 

Table 3.1        Determination of Action and Limit Level of Water Quality for Dredging, Backfilling and Capping Activities

Parameter

Action Level

Limit Level

Dissolved Oxygen

 

 

Surface and Middle Depth Averaged

The average of the impact, WSR 45C and WSR 46 station readings are < 5%ile of baseline data

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

The average of the impact, WSR 45C and WSR 46 station readings are < 4 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

Bottom

The average of the impact, WSR 45C and WSR 46 station readings are < 5%ile of baseline data

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

The average of the impact, WSR 45C and WSR 46 station readings are < 2 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

Suspended Solids

 

 

Depth Averaged

The average of the impact, WSR 45C and WSR 46 station readings are > 95%ile of baseline data

 

and

 

120% or more of the reference stations SS (at the same tide of the same day)

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%ile of baseline data

 

and

 

130% or more of the reference stations SS (at the same tide of the same day)

Turbidity

 

 

Depth Averaged

The average of the impact, WSR 45C and WSR 46 station readings are > 95%ile of baseline data

 

and

 

120% or more of the reference stations turbidity (at the same tide of the same day)

The average of the impact, WSR 45C and WSR 46 station readings are > 99% of baseline data

 

and

 

130% or more of the reference stations turbidity (at the same tide of the same day)

 

Table 3.2        Proposed Action and Limit Levels of Water Quality for Dredging, Backfilling and Capping Activities

Parameter

Action Level

Limit Level

Dissolved Oxygen (DO) (1)

Surface and Mid-depth (2)

Surface and Mid-depth (2)

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for surface and middle layer = 4.32 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact, WSR 45C and WSR 46 station readings are < 4 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

 

Bottom

Bottom

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for bottom layers = 3.12 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact station, WSR 45C and WSR 46 readings are < 2 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

Depth-averaged Suspended Solids (SS) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data for depth average = 21.60 mg L-1

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data for depth average = 40.10 mg L-1

 

and

 

120% of control station's SS at the same tide of the same day

130% of control station's SS at the same tide of the same day

 

 

 

Depth-averaged Turbidity (Tby) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data = 25.04 NTU

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data = 56.30 NTU

 

and

 

120% of control station's Tby at the same tide of the same day

130% of control station's Tby at the same tide of the same day

 

 

 

Notes:

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

(2)    The Action and Limit Levels for DO for Surface & Middle layers were calculated from the combined pool of baseline surface layer data and baseline middle layer data.

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

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

4                                            Conclusion

Baseline water quality monitoring was conducted between 26 July and 23 August 2012 at eighteen designated monitoring stations established for the Project.  The monitoring was carried out 3 days per week, at mid-flood and mid-ebb tides, at three depths (surface, middle and bottom), for 5 weeks prior to the commencement of dredging works in accordance with the Environmental Monitoring and Audit Manual for the Project.  No major activities were noted during baseline monitoring.  Water quality monitoring results are, therefore, representative of the baseline conditions for the Project.

Results have been used to determine Action and Limit Levels for the dissolved oxygen, suspended solids and turbidity for impact monitoring to be conducted during dredging, backfilling and capping activities of the two seabed pits for the new facility at the South of The Brothers. The proposed Action and Limit Levels for DO, SS and Turbidity listed in Table 4.1 below will be adopted for impact monitoring during dredging, backfilling and capping activities of the Project.

Table 4.1        Proposed Action and Limit Levels of Water Quality for Dredging, Backfilling and Capping Activities

Parameter

Action Level

Limit Level

Dissolved Oxygen (DO) (1)

Surface and Mid-depth (2)

Surface and Mid-depth (2)

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for surface and middle layer = 4.32 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact, WSR 45C and WSR 46 station readings are < 4 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

 

Bottom

Bottom

 

The average of the impact, WSR 45C and WSR 46 station readings are < 5%-ile of baseline data for bottom layers = 3.12 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

The average of the impact station, WSR 45C and WSR 46 readings are < 2 mg L-1

 

and

 

Significantly less than the reference stations mean DO (at the same tide of the same day)

 

 

 

Depth-averaged Suspended Solids (SS) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data for depth average = 21.60 mg L-1

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data for depth average = 40.10 mg L-1

 

and

 

120% of control station's SS at the same tide of the same day

130% of control station's SS at the same tide of the same day

 

 

 

Depth-averaged Turbidity (Tby) (3) (4)

The average of the impact, WSR 45C and WSR 46 station readings are > 95%-ile of baseline data = 25.04 NTU

 

and

 

The average of the impact, WSR 45C and WSR 46 station readings are > 99%-ile of baseline data = 56.30 NTU

 

and

 

120% of control station's Tby at the same tide of the same day

130% of control station's Tby at the same tide of the same day

 

 

 

Notes:

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

(2)    The Action and Limit Levels for DO for Surface & Middle layers were calculated from the combined pool of baseline surface layer data and baseline middle layer data.

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

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

 



([1]) Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/ East of Sha Chau Area (Agreement No. CE 12/2002(EP))

[2]        Contaminated Sediment Disposal Facility at South of Brothers (Agreement No. FM 2/2009)

([3])       Hong Kong Observatory (2009) http://www.hko.gov.hk/tide/eCLKtide.htm