How to Seal Ponds With Soda Ash

Drain the pond completely of water. Pump the water out of the lake; make sure to dispose of the water in a safe place where it will not damage or flood structures such as houses or gardens.

Measure the depth of your pond. For best results, dispersants should be applied every six inches into the soil; this should include the soil directly under your pond. You will need to excavate to add soda ash deep enough to affect the whole pond.

Till the soil up to 6 inches below your pond; till to this same level all the way around your pond. If possible, amending all soil in your garden or yard can help to prevent soil shifting and other problems; if you have too much land for this, till and amend the soil up to 100 square feet in all directions from your pond.

Add soda ash at a rate of 10 pounds per 100 square feet of your yard at the lowest depth you dug. Till the soil thoroughly to mix in the soda ash with the soil. After you complete one section, go over it again, tilling in a direction perpendicular to your original till, to ensure that the soda ash is fully incorporated. Repeat application every six inches until you reach the surface, tilling to incorporate the soda ash into the soil.

Compact the soil with a roller with rubber tires or a sheepsfoot roller. These rollers will press the soil in on itself, compressing the soda ash into the soil and crushing away any air pockets or holes left by the tilling, through which water could leak. Compact the entire area that you amended.