Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation

5th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU - November 2009

1.1                                      Background

Since 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.  CMP IVc is presently in operation for backfilling by contaminated mud and is anticipated to reach its capacity in 2010.  A series of four newly constructed seabed pits at the East of Sha Chau area, CMP Va-d, will be provided for the disposal of contaminated mud after CMP IVc is full.  Dredging operations are now taking place to construct CMP Va.  The environmental monitoring and audit (EM&A) programme for the CMPs at the East of Sha Chau area presently covers disposal operations at CMP IVc and dredging operations at CMP V.

1.2                                      Reporting Period

This Monthly Progress Report covers the monitoring period of November 2009.

1.3                                      Details of Sampling and Laboratory Testing Activities

No sampling was scheduled for CMP IV during November 2009.  For CMP V, samplings for Water Column Profiling and Impact Monitoring during Dredging Operations were conducted on 25th and 26th November 2009, respectively.  A summary of field activities are presented in Annex A.

A summary of laboratory analysis results submitted by the Contractor in this reporting month is presented on Table 1.1. 


Table 1.1        Summary of laboratory analysis results submitted by the Contractor during the reporting month

Key Task

Monitoring Component

Results Received from the Contractor

CMP IV

 

 

Water Sampling and Chemical Analysis

a) Water column profiling

August’s sampling: 18 November 2009

 

b) Routine water quality monitoring

August’s sampling: 18 November 2009

Demersal Trawling and Tissue Analysis

a) Demersal trawling

July’s sampling: 18 November 2009

 

 

August’s sampling: 18 November 2009 

Sediment Sampling and Chemical Analysis

a) Pit Specific Sediment Chemistry

August’s sampling: 18 and 26 November 2009 

 

b) Cumulative Impact Sediment Chemistry

August’s sampling: 18 and 26 November 2009 

 

c) Sediment Chemistry after a Major Storm Event

July’s sampling: 30 November 2009 (PSD data)

 

 

August’s sampling: 18 and 26 November 2009 

Benthic Recolonisation Study

 

August’s sampling: 16 November 2009 

CMP V

 

 

Water Sampling and Chemical Analysis

a) Baseline Water Quality Monitoring

August’s sampling: 30 November 2009 (Chromium data)

 

 

 

1.4                                      Details of Outstanding Sampling and / or Analysis

No outstanding sampling remained from November 2009.  Laboratory analysis of chemical contents in tissue and whole body samples of biota collected in July and August 2009 are still in progress. 

1.5                                      Brief Discussion of the Monitoring Results

For CMP IV, monitoring results for Sediment Chemistry after a Major Storm Event for September 2009 are presented below.  Further for CMP V, monitoring results are presented for Water Column Profiling for September and November 2009 and Impact Monitoring during Dredging Operations for November 2009.  Detailed results will be discussed in the relevant Quarterly Reports.

1.5.1                                Sediment Chemistry after a Major Storm Event for CMP IV (Koppu)

Sampling for Sediment Chemistry after a Major Storm Event was conducted on 19th September 2009 after the visit of Tropical Cyclone Koppu, which led to the issue of No. 8 Gale or Storm Signal on 15th September 2009.  The track of Koppu is shown in Figure 1.1. 

 

Figure 1.1       Track of Tropical Cyclone Koppu from 12-16 September 2009 (Source: Hong Kong Observatory)

Concentrations of all metals, except Arsenic, were below the Lower Chemical Exceedance Limit (LCEL) and Upper Chemical Exceedance Limit (UCEL) (Figures 1 and 2 of Annex B).  Concentrations of Arsenic in sediments from all stations exceeded LCEL (12 mg/kg), but remained below UCEL (42 mg/kg). 

Moisture content in the sediments from all stations ranged between 39.97 – 57.98 % (Figure 3 of Annex B).  Sediments were mostly composed of silt and clay materials (73 - 97 %; Figure 4 of Annex B).

1.5.2                                Water Column Profiling for CMP V during September 2009

Results of Water Column Profiling for September 2009 show that salinity, pH and Dissolved Oxygen (DO) all complied with the Water Quality Objectives (WQOs) at both Upstream and Downstream stations (Figures 6 to 8 of Annex B).  However, levels of Total Suspended Solids (TSS) exceeded the WQO at both Upstream and Downstream stations (Figure 5 of Annex B). 

1.5.3                                Water Column Profiling for CMP V during November 2009

Results of Water Column Profiling for November 2009 show that salinity, pH and DO all compiled with the WQOs at both Upstream and Downstream stations (Figures 10 to 12 of Annex B).  However, levels of TSS exceeded the WQO at both Upstream and Downstream stations (Figure 9 of Annex B). 

1.5.4                                Impact Monitoring during Dredging Operations of CMP V – November 2009

Impact Monitoring during Dredging Operations of CMP V was conducted on 26th November 2009.  Sampling was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations upstream and five Impact (Downstream) stations downstream of the dredging operations at CMP V.  Monitoring was also conducted at the Ma Wan station.  At each station, in-situ measurements of water quality parameters and water samples were taken from three water depth levels of the water column which were surface (1m below sea surface), mid-depth and bottom (1m above the seabed).

Monitoring results are presented in Figures 13 to 16 of Annex B.  Levels of DO, depth-average Turbidity and TSS complied with the Action and Limit Levels set in the Baseline Monitoring Report ([1]) (Tables B1 and B2 of Annex B).  

1.6                                      Activities Scheduled for the Next Month

Pit Specific Sediment Chemistry, Sediment Toxicity Monitoring, Benthic Macro In-fauna Sampling, Cumulative Impact Sediment Chemistry Monitoring and Water Column Profiling will be conducted for CMP IV in the next monthly period.  Water Column Profiling and Impact Monitoring during Dredging Operations will be conducted for CMP V during the next monthly period.  The sampling schedule is presented in Annex A. 

1.7                                      Study Programme

A summary of Study programme is presented in Annex C.

 



([1])         ERM (2009)  Baseline Monitoring Report.  Environmental Monitoring and Audit for Contaminated Mud Pit at Sha Chau (2009-2013) – Investigation. Agreement No. CE 4/2009(EP).  Submitted to CEDD.