This section presents the EM&A recommendations for
auditing the water quality mitigation measure during the construction phase of
the Project.
6.2
Environmental
Monitoring and Audit
As stated in the EIA
Report, no water quality monitoring will be required for the construction
phase. However, as the part of the
monthly site audit procedures, it is recommended that the ET Leader confirms
that the Contractor has implemented the drainage management plan and the good
construction site practices, as described in Sections 7.5 and 7.6 of
the EIA Report.
The Contractor will implement the following good construction site
practices to avoid or minimise potential water quality impacts associated with
land based construction.
6.3.1
Construction Runoff and Drainage
Construction site runoff and drainage will be prevented or reduced in
accordance with the guidelines stipulated in the EPD Practice Note for
Professional Persons, Construction Site Drainage (ProPECC PN 1/94). The good
practices include:
·
Provision
of perimeter channels to intercept stormwater run-off
from outside the site. These will be
constructed prior to the site formation works and other earthworks at the
Project Site.
·
Exposed
soil surfaces will be covered by a tarpaulin as soon as possible to reduce the
potential for soil erosion.
·
Open
stockpiles of construction materials on site will be covered with tarpaulin or
similar fabric during rainstorms.
·
Surface
run-off from the construction site will be directed into an existing stream
channel via adequately designed sand/silt removal facilities such as sand
traps, silt traps and sediment basins.
Channels, earth bunds or sand bag barriers will be provided on site to
properly direct stormwater to such silt removal
facilities.
·
Silt
removal facilities, channels and manholes will be maintained and the deposited
silt and grit will be removed regularly, at the onset of and after each
rainstorm to ensure that these facilities are functioning properly at all times.
·
During
excavation in the wet season, temporarily exposed soil surfaces will be
covered, eg by tarpaulin, and temporary access roads
will be protected by crushed stone or gravel, as excavation proceeds. Intercepting channels will be provided (eg along the crest/edge of the excavation) to prevent storm
runoff from washing across exposed soil surfaces. Arrangements will always be in place to
ensure that adequate surface protection measures can be safely carried out well
before the arrival of a rainstorm.
·
Earthworks
final surfaces will be well compacted and the subsequent permanent work or
surface protection will be carried out as soon as practical after the final
surface are formed to prevent erosion caused by rainstorms. Appropriate intercepting channels will be
provided, where necessary. Rainwater
pumped out from trenches or foundation excavations will be discharged into
storm drains via silt removal facilities.
·
The
contractor(s) concerned should apply for and obtain all the necessary discharge
licences.
6.3.2
General Construction Activities
Debris and rubbish generated on-site will be collected, handled and
disposed of properly to avoid entering the nearby stormwater
drains and open drainage channels. All
fuel tanks and storage areas will be provided with locks and be sited on sealed
areas, within bunds of a capacity equal to 110% of the storage capacity of the
largest tank. Open stormwater
drains and culverts near the works area will be covered to block the entrance
of large items of debris and refuse.
6.3.3
Sewage from Workforce
Temporary sanitary facilities, such as portable chemical toilets, will
be employed. A licensed contractor would
be responsible for appropriate disposal and maintenance of these facilities.