In most places the Co-op will bring out lime on a spreader truck. They back up to the pond in several places and turn on the spreader. Call the Co-op for prices.

Those alkalinities are better than the pond's. I would think that lime would work well and not be offset by the springs. If you can get the pond to match the springs you will be in good shape. This link will explain the situation.

http://srac.tamu.edu/tmppdfs/381285-4100...08454fb2925264a