Calling for an immediate engineering study, Certaine said "the site has been designated [historic] by the city . . . but that's not necessarily the full protection it could be afforded."
The burial ground, rediscovered in the last few years and designated a historic site by the Philadelphia Historical Commission in 2013, lies beneath a portion of Weccacoe Playground at Queen and Lawrence Streets. The three-quarter-acre playground is about to undergo renovations under the auspices of the city Department of Parks and Recreation.
The remains of more than 5,000 people - religious, civic, and social leaders, laborers, crafts people, children, infants, the poor and the destitute - are buried on a quarter of an acre and less than two feet from the playground surface.
"What we're trying to do first of all is to get Bethel burial ground stabilized," Certaine said. The point, he said, is "to be sure that no renovation impacts the burial ground further down the line."
The Bethel cemetery land was purchased by Richard Allen, founder of Mother Bethel Church and of the African Methodist Episcopal denomination, in 1810. It was in active use until the mid-1860s and then fell into a state of dilapidation.
The church eventually sold the land to the city at the end of the century.
Terry Buckalew, an independent historian, addressed the group Saturday and said that 2,228 individuals have now been identified as buried at the site. Generations of the Laws family are interred there. So are generations of the Ganges family. Sarah Bass Allen, Richard Allen's wife, was laid to rest in the cemetery, as was formerly enslaved Ignatious Beck, who helped build the U.S. Capitol Building while in bondage.
Buckalew displayed a 1975 topographic map of the cemetery by a city engineer that showed a massive sinkhole, 14 cave-ins, a nearly 200-year-old water main close by on Queen Street, and construction for past playground amenities in the midst of the graveyard.
The sinkhole and cave-ins, Buckalew said, "show a drainage pattern" affecting the burial ground.
"There is water running underneath that shouldn't be there," he said.
After meeting with his group last week, Certaine said, the city has agreed "to freeze" all work connected with playground renovations. A meeting is now planned to bring together the city, neighborhood and Mother Bethel Church leaders, Certaine's group, and other interested parties to discuss how to move forward.
Certaine is urging an engineering study, replacement of the old water main, national historic status, and appropriate commemoration of the site.
The city and neighborhood groups seeking playground renovation have said they were deferring to Mother Bethel on matters related to the burial ground, such as commemoration.
Certaine took issue with that approach.
"This property, this burial ground has been treated as though it's not public property owned by the citizens of Philadelphia," he said. "What authority does the city have to defer to anyone like this?"