Remnants of a late-18th-century vessel were discovered during excavations for a new hotel on the Old Town Alexandria waterfront. (Kate Patterson/for The Washington Post)

A large, heavy ship, scuttled between 1775 and 1798, is being dug out of its damp grave at the site of a new hotel construction project in Old Town Alexandria.

Archaeologists found the partial hull of a ship at 220 S. Union Street, part of the city’s major redevelopment of the Potomac River waterfront. It’s on the same one-block site where workers two months ago discovered a 1755 foundation from a warehouse that is believed to have been the city’s first public building.

“It’s very rare. This almost never happens,” said Dan Baicy, the hard-hatted field director for Thunderbird Archeology, the firm watching for historic evidence during construction. “In 15 years that I’ve done this work, I’ve never run into this kind of preservation in an urban environment where there’s so much disturbance.”

[History uncovered where new hotel will soon stand]

On Monday, naval archaeologists joined the crew at the site to help dismantle the vessel, timber by timber, looking for artifacts and markings that could identify it and show where it sailed and what it carried. The public is invited to view the findings Tuesday from 10 a.m. until noon, after which the wood will be removed from the site.

Archaeologists are rushing to remove a 300-year-old ship from the construction site of a new hotel in Old Town Alexandria. (WUSA9)

The ship’s blackened bow was discovered as construction crews excavated the site where the 120-room Hotel Indigo will soon rise. Digging by hand, archeology crews uncovered a nearly 50-foot-long remnant of the keel, frame, stern and flooring, estimated to be about one-third of the original hull. The wood did not decay, Baicy said, because once it was buried, oxygen could not reach it .

Luck also played a factor in the preservation. A huge brick footing for a later warehouse “barely missed the boat,” Baicy said.

The find has archaeologists surprised and ecstatic. Unlike the warehouse, which was noted in old city records, there was no known documentation of the buried ship’s existence.

“This is like the jewel in the crown for us right now,” said John Mullen, Thunderbird’s principal archaeologist.

It appears the ship was built to carry heavy cargo or was used as a military ship, Mullen said. Archaeologists believe it may have been placed at the site to provide the framework to fill in the cove and sand flats at Port Lumley, one of two spots where the deep-water channels of the Potomac approaches the shoreline.

The wood will be stored in tanks or in a natural body of water and monitored until a preservation lab has room for it, said Fran Bromberg, Alexandria’s archaeologist. The Maryland Archaeological Conservation Lab in St. Leonard took the old warehouse but has run out of room and cannot accommodate the ship, Bromberg said.

Carr Hospitality, which is developing the hotel, was required by the city to employ an archeology firm while excavating the site. Carr has paid for 3-D scanning imagery of the ship and is paying the cost of its removal; the Alexandria government will bear the cost of preservation.

Archeologist Daniel Baicy shows a recently discovered privy at a site in Alexandria where a new hotel is planned. (Kate Patterson/for The Washington Post)

Bromberg said that “it’s certainly a possibility” that the city will be able to put at least part of the ship back together for display and preservation but added that such an effort could require special fundraising.

The excavation site is just a block from one of several remaining cobblestone streets in Old Town, near many pre-Revolutionary War buildings.

Workers also recently uncovered a large privy, six feet long and possibly three seats wide, the third such outhouse found as part of the hotel project. Such discoveries are just as exciting to archaeologists as the ship and the warehouse, because they contain ceramics, glass, bones and all sorts of other debris that people threw into them centuries ago.

“For some reason, we’ve found a lot of shoes,” said Baicy, who has already begun excavating there.