Recommended Pollution Control Clauses for Construction Contracts

2. Water Pollution Control

2.3 Avoidance of pollution during dredging, transporting and dumping of marine mud
2.3.1 Pollution avoidance measures shall include but not be limited to the following :
  1. all equipment shall be designed and maintained to minimise the risk of silt and other contaminants being released into the water column or deposited in locations other than designated location;
  2. mechanical grabs shall be designed and maintained to avoid spillage and shall seal tightly while being lifted;
  3. where trailing suction hopper dredgers for dredging of marine mud are in use, overflow from the dredger and the operation of lean mixture overboard systems shall not be permitted unless expressly approved by the Engineer in consultation with the Director of Environmental Protection;
  4. cutterheads of suction dredgers shall be suitable for the material being excavated and shall be designed to minimise overbreak and sedimentation around the cutter;
  5. all vessels shall be sized such that adequate clearance is maintained between vessels and the sea bed at all states of the tide to ensure that undue turbidity is not generated by turbulence from vessel movement or propeller wash;
  6. all pipe leakages shall be repaired promptly and plant shall not be operated with leaking pipes and all pipe leakages shall be repaired promptly;
  7. before moving the vessels which are used for transporting dredged materials excess material shall be cleaned from the decks and exposed fittings of vessels and the excess materials shall never be dumped into the sea except at the approved locations;
  8. adequate freeboard shall be maintained on barges to ensure that decks are not washed by wave action;
  9. the Contractor shall monitor all vessels transporting material to ensure that no dumping outside the approved location takes place. The Contractor shall keep and produce logs and other records to demonstrate compliance and that journey times are consistent with designated locations and copies of such records shall be submitted to the Engineer;
  10. all bottom dumping vessels shall be fitted with tight fitting seals to their bottom openings to prevent leakage of material;
  11. loading of barges and hoppers shall be controlled to prevent splashing of dredged material to the surrounding water, and vessels shall not be filled to a level which will cause overflowing of material or polluted water during loading or transportation; and
  12. the Engineer may monitor any or all vessels transporting material to check that no dumping outside the approved location nor loss of material during transportation takes place. The Contractor shall provide all reasonable assistance to the Engineer for this purpose.
   
2.3.2 The Contractor shall be responsible for obtaining all necessary dumping permits as stipulated in the ETWB Technical Circular (Works) No. 34/2022 - Management of dredged / excavated sediment. The dredged marine mud shall be deposed of at a disposal site as designated in the dumping permit.
   
2.3.3 When dredging, transporting and disposing of contaminated marine mud, the Contractor shall implement adequate measures for the avoidance of pollution which shall include but not be limited to the following :
  1. dredging of contaminated marine mud shall be undertaken by a suitable grab dredger using closed watertight grab;
  2. transport of contaminated marine mud shall be by split barge of not less than 750 m3 capacity, well maintained and capable of rapid opening and discharge at the disposal site;
  3. the material shall be placed into the disposal pit by bottom dumping;
  4. discharge from split barges shall take place within a radius of 100 metres of centre of the area allocated for the disposal of contaminated marine mud;
  5. discharge shall be undertaken rapidly and the hoppers shall then immediately be closed, material adhering to the sides of the hopper shall not be washed out of the hopper and the hopper shall remain closed until the barge next returns to the disposal site; and
  6. the dumping vessel shall be anchored throughout the dumping operation.
   
2.3.4 The Contractor shall ensure that all marine mud is disposed of at the approved locations. He shall be required to ensure accurate positioning of vessels before discharge and shall be required to submit proposals for accurate position control at disposal sites to the Engineer for approval before commencing dredging and dumping.
   
2.3.5 The Contractor shall ensure that all unsuitable material is disposed of at the approved landfill or other designated location.
   
2.3.6 The Contractor shall only employ vessels equipped with automatic self-monitoring devices as specified by the Director of Environmental Protection for disposal operation, and shall co-operate with and facilitate the Director of Environmental Protection to inspect the device and retrieve the record stored in the device on a regular basis.
   
2.3.7 The Contractor shall provide experienced full time personnel on board all dumping vessels to ensure that appropriate methods to minimise pollution are implemented.

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