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

11th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU - May 2010

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 May 2010.

1.3                                      Details of Sampling and Laboratory Testing Activities

No sampling activity was conducted for CMP IVc during the reporting period.  For CMP V, sampling for Impact Water Quality Monitoring during Dredging Operations was conducted on 24 May 2010.  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 in 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 V

 

 

Water Sampling and Chemical Analysis

Impact Monitoring during Dredging Operations

May’s sampling:

24 May 2010

1.4                                      Details of Outstanding Sampling and / or Analysis

No outstanding sampling and laboratory analysis remained from May 2010. 

1.5                                      Brief Discussion of the Monitoring Results

Results of Pit Specific Sediment Chemistry for April 2010 are presented for CMP IV.  Results of Impact Water Quality Monitoring during Dredging Operations for May 2010 are presented for CMP V.  Detailed results will be discussed in the relevant Quarterly Reports.

1.5.1                                CMP IV

Pit Specific Sediment Chemistry for CMP IV during April 2010

Concentrations of metals at all stations were below the Lower Chemical Exceedance Level (LCEL), with the exception of Arsenic (Figures 1 and 2 of Annex B).  Concentrations of Arsenic slightly exceeded the LCEL at all Near Pit and Pit Edge stations.  No metal concentrations exceeded the UCEL (Figures 1 and 2 of Annex B). 

Concentrations of Total DDT and 4,4” DDE were higher than the detection limits at the Pit-Edge station CPA (Figure 3 of Annex B).  Total Organic Carbon (TOC) concentration in the sediment was the highest at the Pit-Edge station CPB when compared to other stations (Figure 4).  Sediments were mainly composed of silt and clay (65.0 – 95.5 %) materials with the exception of Pit-Edge station CPA, in which sediments were mainly composed of sand (63 %; Figure 5).

Concentrations of Low Molecular Weight (LMW) Polyaromatic Hydrocarbons (PAHs), High Molecular Weight (HMW) PAHs, Total PAHs, Polychlorinated Biphenyls (PCBs) and TBT were below detection limits in sediment samples collected from all stations.  

1.5.2                                CMP V

Impact Water Quality Monitoring during Dredging Operations of CMP V – May 2010

Impact Water Quality Monitoring during Dredging Operations of CMP V was conducted on 24 May 2010.  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 as well as water samples were taken from three depths in the water column (ie surface: 1 m below sea surface, mid-depth and bottom: 1 m above the seabed).

Monitoring results are presented in Figures 6 to 9 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

The following monitoring activities will be conducted in the next monthly period of June 2010:

·         Water Column Profiling for CMP IV;

·         Water Quality Monitoring during Capping for CMP IV; and,

·         Impact Water Quality Monitoring during Dredging Operations for CMP V.

The sampling schedule is presented in Annex A. 

1.7                                      Study Programme

A summary of the 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 EPD in September 2009.