This is how I went about making foam molds for a water feature. At Oregon Institute of technology the Civil engineering department wanted to make a teaching sculpture. The sculpture was built first then when they got more money they expanded the project to include concrete walkways and the water feature. To read more about the project see HERE
. To build the concrete sections they hired contractors but to outsource the molds they received quotes of around $4000. We built the molds for much less. We could choose any method we wanted to build the molds and had two terms to build it.