0.0 Introduction
The purpose of this document is to provide a brief work scope to be carried out by International Shipcare partially awarded to Teranga S/B for removal of water and residue from 2 nos ballasting tanks for the purpose of preparing the tanks for full inspection and thickness gauging. The following are the data available:
i) 2 nos (P&S) Ballast tanks with capacity of 5000m3 each
ii) Both are assumed to be more than 90% full
iii) Tank dimensions are 50m X 6.3m X 22.9m
iv) Both tanks have corrugated bulkheads and double bottoms
v) It is assumed that the level of residue in the tanks shall not exceed 0.5m
vi) Tank 3 stbd contains a layer of oil but the amount is not known. This will be pumped into slop tank for disposal at a later stage.
vii) It is assumed that the water containment is only sea water and that the residue is considered a non toxic waste.
1.0 Task Pre-requisites
Before work can begin on the pumping out of water, the following must be carried out 24 hours before commencement of actual work.
i) Both tank manholes (all manholes) must be open and ventilated to atmosphere. Although the possibility of toxic gases buildup over the years is slim due to the tanks being full, the ventilation and subsequent gas test is mandatory
ii) The vessels balasting calculations should be in Order. It is assumed that the vessel is even keel before pumping out begins. It is the responsibility of the owner to provide the balasting calculations.
iii) A dipstick can be used as a basic measurement to gauge the level of oil in no 3 stbd tank.
iv) It must be confirmed by the owner that all the sea chests are in excellent condition and that that there will be no leakage into the double bottom once the water has been pumped out.
v) Proper Safety measures shall be mandatory and shall consist of minimum the following:
a) Coveralls
b) Workvests
c) Safety helmets, boots and gloves
d) Harnesses on standby
e) Authorised gas testers
f) Confined space entry JHA
vi) Transportation of all equipment from loadout point to vessel. Vessels crane must be utilized to offload equipment from supply boat. Maximum equipment weight is not expected to exceed 2MT
2.0 Job execution sequence
The job will be executed in the following sequence
1. Transportation of all equipment and loading onto vessel
2. Connection of pumps to power supply and connection/laying of hoses
3. Skimming of oil from no 3 stbd into slop tank. A dispstick wil be used to gauge the level of oil and when skimmed into the slop tank, 20% more water will be pumped to ensure that all oil water mixture has been removed.
4. Testing of water samples to be carried out by client before commencement of pumping water overboard
5. Commencement of pumping water overboard. Both tanks will be done simultaneously. The construction of the tanks means this has to be done in stages. Once one stage has been completed, a man has to be sent into the tank to reposition the hose to the next level.
6. Since the tank drawings are not available, it is assumed that the Ballasting tanks have double bottoms and corrugated bulkheads. As such, the water can only be pumped out to a certain level.
7. It is important to note that the actual level of residue/sludge at the bottom of the tanks cannot be ascertained at this time.
8. Once the water has been pumped out to the maximum level, residue removal will take place. Since the residue is only likely to contain mixture of sand, mud water and minimum debris, it is not considered a hazardous substance or toxic material. Unless the client objects, the majority of this residue can be safely pumped overboard.
9. The remainder of the residue will have to be cleared manually. Please note that this is a long painstaking and labor intensive process due to the bulkheads and double bottom providing restricted access. This will be done using buckets, shovels and pulley winches. Men will have to crawl through bulkheads and into the double bottom. They will then have to transfer the residue from section to section until it is convenient to be removed using a pulley and winch.
10. Residue will be disposed overboard unless client insists on treating residue as toxic wastes. Then, they will be loaded into open top containers and disposed onshore in accordance to DOE requirements. We feel however that this is not required.
11. Demobilisation of equipment and personnel
3.0 Project Schedule
The project duration is expected to be 15 days. This is based on daily transfer to and from vessel and working hours from 8am to 5pm daily.
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