B1                                       EM&A Requirements

B1.1                                 Introduction

This Annex provides a summary of the specific EM&A requirements for the designated and potentially designated elements incorporated within the DSD works Package 1B-1T Kam Tin Trunk Sewerage Phase 2.  The same methodology and equipment will be employed for the noise, air and water quality monitoring as outlined in Sections 5 to 7 of the main body of the EM&A Manual.

 

B1.2                                 Air Quality Monitoring

As outlined in Section 5 of the EIA (DE) Report, the appointed Contractor will be responsible for conducting air quality monitoring at the following representative monitoring stations, as defined in Table B1.2b and shown in Annex C, Figure C1-C5.

 

Table B1.2a presents the recommended types and quantities of TSP monitoring equipment required, although the exact requirements will depend on the manpower employed by the contractor.

 

Table B1.2a    TSP Recommended Monitoring Equipment

Description

Quantity

High Volume sampler

6 units

Hand-held direct reading dust meter

1 unit

 

Table B1.2b    EM&A Representative Monitoring Locations

ASR No.

Identity/Description

AM 3

Worksite Boundary facing Kam Kong Villa

AM 4

Worksite Boundary facing Scattered House opposite to Proposed P6

AM 8

Worksite Boundary facing Shui Tsan Tin Tsuen

AM 9

Worksite Boundary facing Scattered House beside Kam Sheung Live Church

AM 10

Worksite boundary facing Hip Tin Kung

AM 11

Worksite Boundary facing Leung Uk Tsuen

 

Prior to the commencement of the EM&A programme, the proposed air quality monitoring stations shall be discussed and agreed with the Engineer, IC(E) and EPD. When positioning the samplers, the following points shall be noted:

 

·         a horizontal platform with appropriate support to secure the samples against gusty wind shall be provided;

·         no two sampler shall be placed less than 2 metres apart;

·         the distance between the sampler and an obstacle, such as buildings, must be at least twice the height that the obstacle protrudes above the sampler;

·         a minimum of 2 metres separation from walls, parapets and penthouses is required for rooftops samplers;

·         a minimum of 2 metres separation from any supporting structure, measures horizontally is required;

·         no furnace or incinerator flue is nearby;

·         airflow around the sampler is unrestricted;

·         the sampler is more than 20 metres from the dripline;

·         any wire fence and gate to protect the sampler, shall not cause any obstruction during monitoring;

·         permission must be obtained to set up the samplers and to obtain access to the monitoring stations; and

·         a secured supply of electricity is needed to operate the samplers.

 

 

B1.3                                 Noise Monitoring

As outlined in Section 6 of the EIA Report, the appointed Contractor for this works package will be responsible for conducting noise monitoring at the following representative monitoring stations, as defined in Table B1.3b and shown in Annex C, Figure C6-C11.

 

Table B1.3a lists the suggested quantities of noise monitoring equipment required for the Project, although the exact requirements will be dependent upon the manpower employed by the Contractor to perform the monitoring.

 

Table B1.3a    Noise Monitoring Equipment

Description

Quantity

Noise meter

1 unit

Calibrator

1 unit

Hand-held anemometer

1 unit

 

Table B1.3b    EM&A Representative Monitoring Locations

NSR No.

Identity/Description

NM9

Scattered House opposite to proposed P6 D26

NM10

Scattered House beside Kam Sheung Live Church D30

NM11

Kam Kong Villa D39

NM12

Shui Tsan Tin Tsuen D41

NM13

Scattered House opposite to Leung Uk Tseun D28

NM14

Ng Ka Tsuen D32

 

Prior to the commencement of the EM&A Programme, the proposed noise monitoring locations will be discussed and agreed with the Engineer, IC(E) and the EPD. If, for example, there are difficulties obtaining access to the proposed noise monitoring locations, alternative monitoring locations may be proposed.  The selection of these alternative monitoring locations shall be chosen on the following criteria:

 

·         at locations close to the major site activities which are likely to have noise impacts;

·         close to the NSRs (any domestic premises, hotel, hostel, temporary housing accommodation, hospital, medical clinic, educational institution, place of public worship, library, court of law, performing arts centre shall be considered as a NSR); and

·         for monitoring locations located in the vicinity of the NSRs, care shall be taken to cause minimal disturbance to the occupants during monitoring.

 

The monitoring station shall normally be at a point 1 m from the exterior of the sensitive receiver building façade and at a height approximately 1.2 m above the ground or at the height that has the least obstructed view of the construction activity in relation to the receiver.  If there is a problem with access to the normal monitoring position, an alternative position may be chosen, and a correction to the measurements shall be made.  For reference, a correction of +3 dB(A) shall be made to the free field measurements.  The ET Leader shall agree with the IC(E) and EPD on the monitoring positions and the corrections adopted.  Once the positions for the monitoring stations are chosen, the baseline monitoring and impact monitoring shall be carried out at the same positions.

 

 

B1.4                                 Cultural Heritage

The EIA(DE) Report had identified a range of measures to mitigate against the potential impacts on cultural heritage resources within the Study Area, as a result of construction and operational activities. The assessment has identified eight historical buildings or features and one known archaeological site (Shui Lau Tin) within the Study Area.

 

Mitigation measures required to ameliorate the potential impacts to acceptable levels have been recommended, as shown below:

 

B1.4.1                           Archaeological investigation

After land resumption but before the construction work takes place for the proposed Shui Tsan Tin pumping station (P4) and Ng Ka Tsuen pumping station (P5) commences, a period of 6 months for each of the sites should be allowed for an archaeological investigation, method agreed with the AMO, to be undertaken.  It is recommended to divide the survey into two phases.  The first phase is to undertake 4 test pits with dimensions 1 m x 1.5 m (2 test pits for each site) to assess if archaeological deposits exist and their possible extent.  If no archaeological interest is identified, no further action is required.  If the result is found positive, rescue excavation should be undertaken if the

deposits are found to be common and not significant, so that preservation by record is achieved.  However, if a highly significant archaeological deposit is identified, the design of the P4 and P5 should be reviewed to integrate the preservation in situ of the archaeological materials or an alternative feasible site for P4 and P5 may be sought and rescue excavation on highly significant archaeological deposit should be regarded as the last resort.  The AMO should be prior consulted for the result of the investigation and the proposed mitigation measures.  The investigation would be laid down as a condition in the Environment Permit.

 

It is recommended that any archaeological work (i.e. watching brief and site investigations) undertaken by the Contractor should be conducted by a qualified archaeologist, who is licensed by the Antiquities Authority under the Antiquities and Monuments Ordinance (Cap. 53). The Contractor should inform AMO at least four weeks prior to the commencement of the archaeological evaluation, of the expected start date and programming of the works. This is to allow AMO the opportunity of arranging the on-site monitoring of the works.

 

No direct impact on the identified historical buildings and features is expected, therefore, no mitigation measures is necessary.

 

The licensing procedure is a statutory requirement stated in Sections 12 and 13 in the Antiquities and Monuments Ordinance (Cap.53).

 

B1.4.2                           Vibration Monitoring

Based on the proposed construction works, potential vibration impacts are envisaged at Site E, Ng Ka Tsuen.  Site activities comprising of bored piling and vibration compaction within 7.5 m and vibropiling within 25m of the Site E will likely exceed the 4mm/s ppv limit. It is therefore recommended to set back the pumping station to avoid encroachment of safe margins from the historic building of Ng Ka Tsuen.

 

For construction phase, the Contractor shall be required to avoid encroachment of the safe margins of 7.5 m from the historic building of Ng Ka Tsuen and pay particular attention to remove underlying obstructions such as buried foundations, floors etc before continuing with bored piling and sheet piling operations.  All sheet piling operation shall be set back by 25 m from the historic building of Ng Ka Tsuen.  If demolition within 7.5 m of the historic buildings at Ng Ka Tsuen is required, preference should be given to use of hand method and use of mini excavator (Bobcat type plant) to remove materials from the area at ground level.  

 

In addition, careful selection of pile driving equipment by the Contractor to meet the criteria is recommended.  For sheet piling, an international construction equipment Model 14RF is an example of a resonant free vibrator. It is a type of pile driver designed so that the rotating system of weights within the driver can be accelerated to operating speed with the rotating masses in balance and, once at operating frequency and above resonant mode, the weights are rearranged to be out of phase and hence generated the vibration required to drive the pile. It is also recommended that a trial of sheet piling using the proposed plant be undertaken by the Contractor and the vibration monitored by the Contractor and Engineer prior to proceeding with works. The monitoring should be taken at the closest accessible point to the historic building to enable the Engineer to assess the potential risk from the expected levels of vibration at Ng Ka Tseun.

 

Structural Survey

In addition, and prior to the commencement of site operations it is recommended that a structural survey of Ng Ka Tsuen historical buildings (Site E) be undertaken by specialist surveyor approved by AMO to record the condition of the historic buildings.  The survey should be conducted four weeks prior to the commencement of the construction works.  This survey shall focus on the quality of construction and finishes and the general condition of the structure and its finishes. A schedule of defects (including cracks) is to be prepared for submission to the Engineer and AMO and shall be supported by photographic record. Upon approval to proceed with the works, vibration monitoring is recommended during the site preparation, earthworks and foundation and reinstatement stages.

 

Upon completion of the structural survey, it is recommended that vibration monitoring be carried out, firstly on a trial basis to ascertain locations of highest impact within the building relative to an appropriate ground level location on the worksite boundary; the setting of these levels shall be subject to AMO approval and accessibility.  Thereafter monitoring shall be undertaken for the duration of the works and, where exceedance of the limit is noted, the works shall be stopped and the Contractor shall be required to prepare a plan for the approval of the Engineer and AMO to ensure that the works will continue without exceedance of the vibration criteria.  If at any time the Engineer should note any damage to the decoration and structure of Ng Ka Tsuen historical buildings, the Contractor shall stop works and prepare a method statement outlining provisions to ensure no further deterioration of the building.  Such measures may comprise alternative selection of plant, method of construction, use of cut off trench located close to the source of the vibration.

 

 

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