I am installing a short stone wall, made from these bricks.
The wall is not tall, about 2.5' (0.8 m), but it is about 140' (45 m) in length. The wall needs to be strong to withstand flash floods, which can dump 1' (30 cm) of water in the back yard in as little as 15 minutes.
I carved out a trench in which to place the first row of bricks. I've filled the trench with water to get a level.
---- ------ \ / ------- <-- 6 inches (15 cm) wide
The trench is 2 inches (5 cm) deep at the low spot of land, but the wall goes up a slight incline, and there the trench is 14 inches (35 cm) deep.
---- ------ | | <--- It can be much deeper up higher on the hill |~~~~~~~| <-- I can pour in water to get a level, but no idea how to use that to place the bricks level \ / ------- <-- Still 6 inches (15 cm) wide here
How can I get this wall to be perfectly level, within 1/4" (5 mm) of accuracy from the one end of the wall to the other?
I can fill the trench with water, to get a level line. Is there some kind of concrete mix I can pour into the water that will easily give a level the whole length of the trench?
I considered just adding gravel to the trench, and eyeing if it is up to the water level, but the act of adding gravel will change the height of the water itself, so I don't know if that is a viable plan.