I'm building a 9' x 6' x 4' deep pond. 1/2 is above ground (solid brick block) 1/2 below ground. Once I bring the liner over the top of the pond brick how do I secure the liner before adding the capstone? I have Firestone EPDM .045 liner. I'm in Colorado, so I'm currently adding insulation to brick prior to doing the underlayment and liner.