Part 2 – Sampling from ballast water tanks

  2.1 Sampling of ballast water via manholes allows direct access to ballast tanks and ballast holds.

  2.2 The disadvantages of this type of sampling access include the need for opening and closing manholes and hatches. Further, overlaying cargo may prevent access for sampling. Also, hatches and horizontal openings inside tanks are not aligned one below the other, which means that although the tank may have three or more decks, only the top deck may be accessible for sampling. Further, in some ships, access hatches and vertical openings are on the side of the tank and thus are not accessible unless the tank is empty. Another disadvantage is ladders and platforms may inhibit access to the full depth of the tank. Sampling from some certain parts of the ballast water tank may result in a lack of representation of the whole ballast water discharge.

  2.3 Samples should be collected using scientific sampling equipment including plankton nets and pumps, as appropriate, for the sampling and analytical method intended for use.

  2.4 Whenever possible samples should be taken from multiple water depths inside the ballast tank.

  2.5 When employing plankton nets:

• .1 the sample should be taken in a vertical net haul from the deepest sampling point accessible in the tank;

• .2 all plankton nets should be lowered to the maximum accessible depth inside the ballast tank and retrieved at a speed of approximately 0.5 m/s; and

• .3 multiple vertical net hauls may be needed to meet the required sample volume. The water volume sampled may be measured by flow meters in the opening of the net or by noting the sampling depth and net opening diameter.

  2.6 When employing pumps:

• .1 pump intake pipes should be lowered to multiple depths (if possible) for different samples to obtain a vertical sample; and

• .2 the water volume sampled may be measured by flow meters in the hose or by using larger containers to measure the pumped water volume.

  3.1 Sampling by sounding pipes, when available, could be appropriate due to accessibility. However, there are some limitations when using this point to test for compliance. The use of sounding pipes will be more effective when the ship’s sounding pipes are perforated along their length, ensuring better mixing of ballast water and that within the sounding tube. However, care must be taken if initial water samples from a sounding pipe indicate no or insufficient exchange even though the ship’s records document otherwise. Experience has shown that in some cases water within unperforated sounding pipes is not affected during an exchange. This may occur during flow-through because the water in pipes is not exposed to the mixing within the tank. This may also occur during empty refill when water in the sounding pipes is held within the pipe by vacuum pressure while the tanks are drained and then filled.

  3.2 Samples should be collected using scientific sampling equipment as appropriate.

  4.1 Pumps of various types may be used to sample via sounding or air pipes.

• 4.1.1 The use of pumps may be limited by inability to overcome the pumping head, i.e. when the vertical distance from the pump to the water level in tank exceeds 10 metres, suction pumps cannot be used.

• 4.1.2 Pump intake pipes should be lowered to multiple depths (if possible) for different samples to obtain a vertical sample. The water volume sampled may be measured by flow meters in the hose or by using larger containers to measure the pumped water volume.

  4.2 In principle, intrinsically safe pumps should be used in all circumstances.

  4.3 Pumps that do not contribute to the mortality of organisms should be preferred.