If anyone is interested, I did find out this about the Thruway and Montezuma marsh:

[Quote]

"We had to carry the road across Montezuma Marsh, a Federal wildlife refuge north of Cayuga Lake," Mr. Tallamy said. "Beneath the deep surface muck lies a bed of marl--not unlike stiff tooth paste. We built dikes on either side of the route, pumped the channel dry, and dug the muck from the marl. A roadbed of gravel, stones, and clay was planted one to three feet higher than the desired road level to allow for settling."

[End quote]

Source: Matt C. McDade, "New York's New Main Street," National Geographic Magazine, vol. 110, no. 5 (November 1956), p. 591.

Mr. Tallamy was Bertram D. Tallamy, the chairman of the NYS Thruway Commission, who was later hired by Eisenhower to build the Interstate. The National Audubon Society and the Federation of New York State Bird Clubs protested the fact that the state was building a major expressway through the middle of a national wildlife refuge, fearing that the ducks and geese would be chased away from the only federal refuge for migrating waterfowl in New York State. The U.S. Department of the Interior responded that moving traffic had little effect on brooding birds and that the roadbed would provide a "far more adequate" dike against flood waters than those maintained by the Fish and Wildlife Service. There was also talk of relocating the Clyde River, which repeatedly flows in and out of the canal in that area, to the north of the Thruway as a way to prevent flooding of the preserve lands.

See: New York Times, November 1, 1951, p. 28; December 4, 1951, p. 28; December 19, 1951, p. 15. (These articles are listed in the New York Times Index under "Wildlife Sanctuaries" rather than under "Roads and Highways" with the rest of the Thruway stories.)