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

13th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU - July 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-b.  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 July 2010.

1.3                                      Details of Sampling and Laboratory Testing Activities

Demersal Trawling was conducted on 28-29 July 2010 for CMP IVc.  Water Column Profiling was not conducted for CMP IVc since there was no disposal activity during the scheduled monitoring events on 27 and 31 July 2010.  For CMP V, sampling for Impact Water Quality Monitoring during Dredging Operations was conducted on 2, 5, 7, 9, 12, 14, 16, 19, 23, 26, 28 and 30 July 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

June’s sampling:

16 July 2010

1.4                                      Details of Outstanding Sampling and / or Analysis

No outstanding sampling and laboratory analysis remained from July 2010. 

1.5                                      Brief Discussion of the Monitoring Results

Results of Impact Water Quality Monitoring during Dredging Operations for July 2010 are presented for CMP V.  Detailed results will be discussed in the relevant Quarterly Reports.

1.5.1                                CMP V

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

Impact Water Quality Monitoring during Dredging Operations of CMP V was conducted for three times per week in this reporting month.  On each survey day, 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 1 to 48 of Annex B.  Generally, levels of DO, depth-average Turbidity and TSS complied with the Action and Limit Levels set in the Baseline Monitoring Report ([1]) (Table B1 of Annex B).  However, occasional exceedances of Action and Limit Levels were recorded.  For bottom DO level, isolated exceedances of Action Level were recorded during the mid-ebb tide at station DS4 and DS5 on 7 July and at station DS4 only on 9 July 2010.  Exceedances were not recorded for stations DS1-3 which are closer to the dredging works area, therefore, the exceedances recorded at DS4 and DS5 are unlikely to be caused by the dredging works of CMP V.  For Turbidity, exceedances of Action Level were recorded at station DS1 during the mid-flood tide on 9 and 12 July 2010.  For TSS, exceedances of Limit Level were recorded during the mid-flood tide at station DS1 on 9 and 12 July while exceedance of Action Level was recorded at DS3 on 12 July 2010 during the same tidal period.  It should be noted that the dredging works were undertaken at CMP Va on 9 July and at CMP Vb on 12 July 2010.  On the previous and following sampling days of these dredging operations (7 and 14 July, respectively), although similar works were being conducted, there were no exceedances at any of the above stations.  Therefore, these exceedances were unlikely to be caused by the dredging works of CMP V. 

In accordance with the requirements of the EM&A Manual, CEDD is in discussion with the Environmental Protection Department (EPD) as to what appropriate actions are to be taken due to the record of exceedances of water quality Action and Limit Levels.  Measures taken will be reported in due course.


1.6                                      Activities Scheduled for the Next Month

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

CMP IVc

·         Water Column Profiling;

·         Routine Water Quality Monitoring;

·         Water Quality Monitoring for Capping Activity;

·         Pit Specific Sediment Chemistry Monitoring;

·         Cumulative Impact Sediment Chemistry Monitoring;

·         Sediment Toxicity Testing;

·         Demersal Trawling; and,

·         Benthic Recolonisation Monitoring.

CMP V

·         Impact Water Quality Monitoring during Dredging.

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.