Annex C

Measures to Mitigate Environmental Impacts from Site Run-off During Construction

1. At all parts of all works area and construction sites, and throughout the entire construction period, the following mitigation measures shall be implemented to minimize the site run-off during construction:

(a) construction site run-off and drainage shall be prevented or minimized in accordance with the guidelines stipulated in EPD’s Practice Note for Professional Persons on Construction Site Drainage, Professional Persons Environmental Consultative Committee, 1994 “Construction Site Drainage” (copy attached at Annex D);

(b) run-off from all the construction sites shall not be discharged directly into any watercourse or the marine environment;

(c) wastewater arising from tunneling and excavation works shall be discharged into the storm drainage system via petrol interceptors and silt traps/sediment tanks;

(d) all drainage facilities and erosion and sediment control structures shall be regularly inspected and maintained to ensure proper and efficient operation at all times;

(e) sediment tanks of sufficient capacity, constructed from pre-formed individual cells of approximately 6-8m³ capacity shall be used at all sites for settling wastewater prior to disposal;

(f) all equipment shall be checked to prevent oil or lubricant leakage;

(g) a surface water drainage system shall be provided to collect operational tunnel seepage. Where oils and lubricating fluids could be spilt, the operational tunnel discharge and track runoff shall pass through the oil and grit / silt interceptors / chambers to remove oil, grease and sediment before being disposed to the public stormwater drainage system;

(h) silt traps and oil interceptors shall be regularly cleaned and maintained in good working order;

(i) all water and liquid waste products arising on the site shall be collected and removed from site via a suitable and properly designed temporary drainage system and disposed of at a location and in a manner that will not cause pollution or nuisance;

(j) sewage from site toilets and kitchens shall be collected and disposed at an appropriate sewage treatment works. Grease traps shall be installed to collect wastes from canteen, and shall be capable of providing at least 20 minutes retention during peak flow, prior to discharge; and

(k) all existing stream courses and drains within, and adjacent to, the site(s) shall be kept safe and free from any debris and any excavated materials arising from the construction works.