The cemetery land was initially acquired by Richard Allen, founder of Mother Bethel and the African Methodist Episcopal Church, in 1810 and was in active use until about 1868. The land eventually was acquired by the city and has served largely as a playground for more than a century.
During its period of active use, many of Mother Bethel's leaders were buried there, including Sarah Bass Allen, abolitionist and Richard Allen's widow, who was interred in 1849, according to city records. The church maintains that her remains are now within Mother Bethel's crypt.
In June, the burial ground was designated a historic site by the Philadelphia Historical Commission, meaning that any construction must pass muster with it.
On Wednesday, a group of school children from the Khepera Charter School in Mount Airy visited the site and watched archaeologists working on the third of four test excavations cut into the playground surface.
The work had uncovered part of the cemetery's stone eastern wall and encountered intact graves only about three feet below ground.
An earlier survey of the site with ground-penetrating radar had suggested burials could lie well outside the boundaries of the cemetery. So far that has not proved to be the case.
One test excavation struck considerable soil "disturbance" - probably from previous construction - but grave sites were located below that at about five feet. Mooney said the remains in urban grounds are normally buried vertically and could be stacked as many as six or seven deep.
No remains are being removed, he said. The excavation seeks to determine the depth of the historical burials so planned renovations do not disturb them.
The renovation is a joint project of the city's Parks and Recreation Department and Water Department, and the Pennsylvania Horticultural Society. The Queen Village Neighbors Association and the Friends of Weccacoe began the drive for renovation.
The city and community groups are deferring to Mother Bethel Church on how to proceed with commemoration of the cemetery.
The Rev. Mark Tyler, Mother Bethel's pastor, said Wednesday he believed there are "thousands of people in Philadelphia related to people buried here."
"In the absence of any organized group of descendants, people have deferred to us" on the matter of commemoration, he said. "Descendants have to have a say."
Michael Coard of the Avenging the Ancestors Coalition an activist group that visited the site Wednesday, said: "We're here to watch what's going on because it's our parents, it's our grandparents," buried there.
"We're not here for a little yellow and blue sign on the corner that says black people are buried here," he said. "This is hallowed ground, sacred ground, consecrated ground. That's what we're here for."
Contact Stephan Salisbury at 215-854-5594, email@example.com, or @SPSalisbury on Twitter