TAMPA — Above ground, developers are breathing new life into the once derelict stretch of downtown waterfront property that will be reborn as the long-awaited Water Street Tampa project.

But it's what lies beneath the $3 billion entertainment district that has captured the attention of archaeologists and city officials — an unknown number of what are believed to be human remains.

Strategic Property Partners officials confirmed late Wednesday that a number of graves believed to date back to the 1830s have been discovered in an area north of Channelside Drive.

Their presence is not a surprise. Much of the project lies in the area that was once Fort Brooke, a long perished Army post established in 1824 to protect Tampa's early settlers from nearby Seminole tribes. It has yielded glimpses of its past almost every time dirt is disturbed in the area.

"From what I've been told, they appear to be very, very old probably dating back to the time when it was Fort Brooke," said Mayor Bob Buckhorn, who was briefed about the findings about two weeks ago. "I was not surprised given the history of that particular site and what took place there hundreds of years ago."

Strategic Property Partners is the development company launched by Tampa Bay Lightning owner Jeff Vinik and Cascade Investment, the capital fund owned by Microsoft billionaire Bill Gates, to build Water Street Tampa. Company officials said the discovery is not expected to significantly impact construction timelines. A team of archaeologists are working to ensure all the remains that were found are treated with respect.

A historical survey of the site was conducted prior to the start of construction. The team anticipated finding the long-abandoned Estuary Cemetery north of Channelside Drive, according to a statement from the developer. The contents of the graves are believed to have deteriorated due to prior development from the 1960s and 1970s.

The company plans to reunite any recovered remains with Tampa's earliest residents buried in local historic cemeteries.

Fort Brooke served as a major outpost on Florida's west coast during all three Seminole Indian Wars and the Civil War. The fort also played a part in the development of the village of Tampa.

Its footprint included a southern stretch of the city's downtown lining Garrison Channel, parcels that now hold the Tampa Bay History Center, the Tampa Convention Center and Amalie Arena.

In 1980, archaeologist Ken Hardin uncovered a burial site for soldiers, civilians and American Indians killed during the Second Seminole War, from 1835 to 1842. The remains were unearthed as developers prepared to construct the Fort Brooke Parking Garage on the site, and once they were properly removed the garage was erected on top of the former graves.

Seven years later, Hardin got another call from developers working at a site just three blocks away. Construction workers unearthed brittle, brown bones buried about three feet beneath the foundation of Tampa's downtown convention center. Hardin speculated those bones could be about 1,000 years old and belong to as many as 12 different American Indians from an indigenous tribe predating any known living relatives.

Remains were also unearthed during construction of Amalie Arena in 1994. An unmarked grave was discovered just outside the 20,000-seat arena's footprint in a stretch of land that archaeologists say once held Fort Brooke's officer quarters, as well as an adjacent prisoners' pen.

Unlike those discovered down the street, these remains were likely buried in the 1820s. Water from Tampa Bay seeped into the small grave, helping to preserve a simple wooden coffin and its contents — a small scrap of leather and the corpse of a young man believed to be in his early 20s.

Tampa Bay History Center curator Rodney Kite-Powell said the findings sound similar to those discovered under the parking garage in 1980. The downtown area has been home to people for thousands of years.

"It's really interesting to hear this," he said. "There is a potential for archeological discovery anywhere in downtown."

Contact Christopher O'Donnell at codonnell@tampabay.com or (813) 226-3446. Follow @codonnell_times.