I assume that you want the pond to be deeper than 1 foot. Can you move the pipe over? What is it made of and what is it draining?

I was planning to dig a foot and then build up the bricks a foot, making a 2-foot deep pond.

The heavy water (300 gallons) wouldn't be good sitting on the pipe though, correct?

The pipe provides drainage from sprinklers and rain water. I can now see how this pipe connects a nearby drain to another drain on the side of the house.

So it is corrugated black pipe and would smash under the weight of water. I would lay some heavy plastic, mix some sakrete and pour a slab of concrete over that area to about 1/2 that end of the pond to give the wt. of the water a larger area to press down on. Round off along the edge in the center of the pond to keep from puncturing the liner.

I hope this helps. Maybe someone else will give a solution.

I would just cover it with a 2X8" piece of treated lumber. Even that is probably overkill.

That sounds a lot better than digging a new hole somewhere else. Thank you for the replies!