8                BUILT HERITAGE MONITORING

Monitoring Requirement

8.1          In accordance with the updated EM&A Manual, baseline condition survey and baseline vibration impact assessment shall be conducted for identified built heritage prior to the commencement of construction works. Baseline condition survey and baseline vibration impact assessment shall be conducted by a qualified building surveyor or qualified structural engineer to define the vibration limit (a vibration limit at 7.5mm/s and 15mm/s could be adopted for graded historical buildings and historical buildings respectively) and to evaluate if construction vibration monitoring and structural strengthening measures are required during construction phase to ensure the construction performance meets the vibration standard stated in the EIA report.

8.2          According to the condition survey report from cultural heritage condition survey for Fanling Bypass Eastern Section under EP-473/2013/A, a vibration monitoring plan was proposed for the surveyed cultural heritage based on the Buildings Department’s Practice Note (PNAP) APP-137. This section presents the results of built heritage monitoring performed by the Contractor according to the proposed monitoring plan in baseline condition survey report. Appendix B shows the Limit Levels for the monitoring works.

Monitoring Location

8.3          In the reporting month, construction vibration monitoring was conducted for built heritage features at FL02 and FL27 when pile driving operation was conducted within assessment area of the construction works. The location of the construction vibration monitoring stations was summarised in Table 8.1 and shown in Appendix K.

Table 8.1    Location of Construction Vibration Monitoring

EP. No

Contract No.

Monitoring Station (s)

Nature of Cultural Heritage

Location (s)

EP-473/2013/A

ND/2019/05

FL02

Grave

Northwest side of Shung Him Tong Tsuen, at the hillside behind On Lok Garden

FL27

Monument

Opposite to Shung Him Tong Public Toilet, at the bottom of slope feature

Monitoring Parameters and Frequency

8.4          Table 8.2 summarises the vibration monitoring plan for surveyed cultural heritage under the Works Contracts. Vibration monitoring was conducted for surveyed built heritage when pile driving operation was conducted within the assessment area of construction works.

Table 8.2    Vibration Monitoring Plan

EP. No

Contract No.

Monitoring Stations

Distance with Construction Works

Monitoring Plan

EP-473/2013/A

ND/2019/05

FL02 and FL27

Within 50m

Daily assessment is required

Within 75m

Bi-daily assessment is required

Within 100m

Weekly assessment is required

Remark:

[1] Baseline condition survey was conducted for built heritage features at HFL05, FL02, FL04, FL24, FL27 and FL36 under ND/2019/05 for EP-473/2013/A. As HFL05, FL04, FL24, FL27 and FL36 were not within the assessment area of the related construction work, no construction vibration monitoring was conducted for the built heritage in the reporting month.


8.5          The construction vibration monitoring was conducted throughout each event of the pile driving operation on a daily basis. The effect of ground-borne vibration from piling works on the surveyed built heritage was assessed by the maximum peak particle velocity (ppv), which was obtained from the maximum value of measurement of all pile driving operation events.

Monitoring Equipment

8.6          Copies of calibration certificates of the monitoring equipment employed by the Contractor of the construction vibration monitoring are attached in Appendix C.

Results and Observations

8.7          In the reporting month, construction vibration monitoring was carried out by the Contractor for the built heritage features at FL02 and FL27 on a daily basis when pile driving operation was conducted within 50m of the construction work. No Limit Level exceedance for construction vibration monitoring was recorded in the reporting month. The monitoring results are provided in Appendix K.

Event and Action Plan

8.8          Table 8.3 summarises the vibration limits for construction vibration monitoring for surveyed cultural heritage.

Table 8.3     Vibration Limits for Construction Vibration Monitoring

Type of Building

Guide Values of Maximum ppv* (mm/Sec)

Transient Vibration

Continuous Vibration

Vibration-sensitive / dilapidated buildings#

7.5

3.0

Declared monuments/ Historical structures

3.0

Remarks:

* peak particle velocity

# as cultural heritages are sensitive receivers, vibration monitoring should be classified as vibration-sensitive

8.9          If any exceedance of limits is found or damage to either structural or non-structural elements of the historic buildings is identified, the construction works should be stopped immediately and structural engineer’s advices should be sought for any remedial work.