When you mortar targets a pool smaller than 36 squares, not everything has to be lost. If other pools are nearby you will see an effect called 'through the wall damage', see below:

Not only the pool hit by the shell gets cleared, but also parts of neighboring pools. If you count well, you'll notice that again 36 squares are affected. This effect is a result of an optimization used to speed up the calculations, causing all cells on the same or a lower elevation level to get damaged when there is still fire power left. So it doesn't matter whether there is a wall between these areas or not!

The shape or amount of pools doesn't matter:

In this case you see 6 adjacent pools of each 9 squares (all 3 by 3). Again the 36 nearest squares get cleared, doing maximum damage of 144 ccc.

There is a limit to the distance of 'through the wall damage' however:

This effect will not reach further than 7 blocks from the point of impact, resulting in 72 ccc damage. This doesn't differ from 'normal' damage:

Only 15 x 4 = 60 ccc damage is done here.

Blasters can also benefit from this kind of damage:

On the left you see a blaster capping a weak emitter. The pool to the left of it would normally overflow and is out of reach of the blasters range, but the 'through the wall' damage also affects the creeper in there (one elevation level lower than the blaster and the capped emitter).

On the right you see a blaster capping an emitter in a rather similar situation. Only this time there is a crazonium wall in between as well! It doesn't matter however, the damage is done anyway.

Comment on this effect by the games creator Virgilw: Mythology wise, I could imagine that the Creeper is connected to itself through subspace… so when part of it is damaged nearby creeper is also damaged regardless of physical barriers. Most of the time it is difficult to see or take advantage of this effect, but in this map you can use it to your advantage.

This is originally information and screenshots made by UpperKEES. Link to the forum posts about this:
http://knucklecracker.com/forums/index.php?topic=5062.0