I've just had two excavators out to get estimates on repairing my 1-acre pond. Their suggestions differed on several key points.

1) One suggested a single L-shaped pipe of 18-in diameter, with a valve. This is the traditional "down-and-through-the dam" shape, and what I have in there now.

The other suggested multiple culverts running straight through. For instance, a pair of 15-inchers. His opinion was that multi-15s would handle more flow than a single 18, that a valve is never used, and that the L-shape provides no advantages.

2) Both galvanized and PVC materials are available in either configuration. Both seemed to prefer galvanized for its strength (harder to crush), although PVC would last longer (resist metal eroding/rusting). One mentioned that the deeper "grooving" which adds strength to the PVC creates more places for dirt, etc to get caught.

3) The job will involve draining the pond / cutting through the dam, letting the bed dry, dredging out the silt (I am hoping to restore it to its original depth of 30 years ago), the reconstructing the earthen dam with new drainage pipes in place.

One contractor indicated he can do this during the winter (Northern Virginia here), and that the bed will dry / freeze enough in a few weeks for work to proceed. The other indicated that it will be a spring / summer project?

4) I don't have the estimates yet, but one guy seemed to think that removing 4 ft of silt covering an acre would be a month's work, which would be prohibutive. Does this sound within the realm of reason?