As the proposed site for the concrete batching plant is located near the seawall, the coastal waters could potentially be impacted by sediment laden and construction runoff. With the implementation of proposed mitigation measures stipulated in EIA Report, it is expected that no unacceptable water quality impacts are anticipated from the construction of the concrete batching plant. During operational phase, no wastewater will be discharge outside the boundary of the plant, there will not be any potential water quality impacts associated with the operation of the facility. Therefore, no water quality monitoring will be required for both construction and operation of concrete batching plant. Auditing works such as checking of surface run-off and pre-treatment facilities, etc. should be carried out.
Regular site inspections should be carried out in order to ensure that the mitigation measures are implemented and are working effectively. The Contractor shall be responsible for the design and implementation of these measures illustrated below:
Construction Runoff and Drainage
The site practices outlined in the Practice Note for Professional Persons on Construction Site Drainage, EPD, 1994 (ProPECC PN 1/94) include :
·
Provision
of perimeter channels to intercept storm-runoff from outside the site. These
should be constructed in advance of site formation works and earthworks.
·
Programming
of the works to minimise earthworks during the rainy season whenever possible.
·
Sand/silt
removal facilities such as sand traps, silt traps and sediment basins should be
provided to remove sand/silt particles from runoff to meet the requirements of
the Technical Memorandum on Effluent Standards under the Water Pollution
Control Ordinance. The silt traps
should be designed as per the guidelines given in Appendix A1 of ProPECC PN
1/94. Sedimentation basins should be configured so as to provide sufficient
time for the suspended solids to settle out. Baffles should be provided in the
basins to reduce water velocity, promote settling and prolong the residence
time of the runoff. These facilities
should be regularly desilted to maintain their effectiveness.
·
Channels
or earth bunds should be constructed to direct the surface runoff to sand/silt
removal facilities.
·
Exposed
soil surfaces should be protected by paving as soon as possible to reduce the
potential for soil erosion.
·
Open
stockpiles of construction materials on site should be covered with tarpaulin
or similar fabric to prevent surface erosion during rainstorms.
General Construction Activities
· Debris and rubbish generated on-site should be collected, handled and disposed of properly to avoid entering the nearby coastal waters.
· All fuel tanks and storage areas should 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 drainage channels and culverts near the works areas should be covered to block the entrance of large debris and refuse.
Sewage Effluent
· Temporary sanitary facilities, such as portable chemical toilets, should be employed on-site. A licensed contractor must be responsible for appropriate disposal and maintenance of these facilities.
In addition the Contractor should ensure the mitigation measures for the proposed on-site concrete batching plant in Appendix C3 are properly implemented throughout the whole construction and operation period.
If the above measures are not sufficient to restore the water quality to an acceptable level, the Contractor shall liaise with the ET on some other mitigation measures, propose to ER for approve, and carry out the mitigation measures.