(Updated at 3:20 p.m.) While Alexandria heads out on ghosts tours for Halloween, local archaeologists are busy scouting for secret burials under two historic cemeteries.

Archeologists with the city’s Office of Historic Alexandria are working to pinpoint where coffins and headstones may have been swallowed by the changing landscaping in the Penny Hill and Douglass cemeteries as they plan drainage maintenance for the sites.

“In a couple places you see the very tippy tops of headstones just barely peeking above the dirt and you realize that there’s an entire headstone sunken in 2-3 feet. So you look around and go ‘Oh my god this entire cemetery is slowly sinking into the ground,'” Benjamin Skolnik, an archeologist with the city, told ALXnow of the issues facing the two cemeteries.

“A lot of the markers were probably made of wood and have since decayed and evaporated into the mists of time,” he said, adding that others buried in the Penny Hill potter’s field often couldn’t afford a marker.

Fixing the drainage issues at both sites causing could mean digging ditches — and right now that would be impossible without disrupting lost burial sites.

Penny Hill was founded in 1796 but start records only date back to 1912. Those records indicate 906 people were buried in the last century, but today cemetery is an empty, grassy field.

And at Douglass, where records indicate the first person was buried in 1895, there are about 650 standing headstones, but over 1900 names recorded in burial records.

“There’s three times the number of people written in the cemeteries as there are standing headstones, so the question is where is everybody?” said Skolnik.

This summer, the state awarded Alexandria a $10,500 grant to study what graves could be underneath the grass at both cemeteries. Now the survey work is underway as teams of archeologists rove the grounds with ground-penetrating radar (the same kind used to find dinosaurs) and electrical conductivity meters to identify burials by the metal hinges on caskets, the shafts dug to bury caskets, as well as skeletal remains or headstones.

Initial data from Douglass confirms some areas with no standing stones do have graves underneath, and in some cases, more than one grave.

“We know that they were selling what they referred to as “half-graves” which is basically that you stack them,” explained Skolnik. “The first one goes down 8 feet. The next one goes down 4 feet.”

The surveys haven’t gone without a hitch, however. Yesterday (Tuesday’s) rain storm cancelled one day of work, and nearby utilities can interfere with the equipment.

“We ran into a small problem on Saturday when we started our survey at Penny Hill,” said Skolnik. “The southeast corner of Penny Hill is right next to a power substation [which] was playing havoc with the sensitive instruments.”

The surveys are in addition to the Alexandria archaeologists’ other responsibilities, including examining possible remains and objects buried under development sites — work that led to the excavation and reconstruction of several long-buried ships.

“It’s probably not a surprise that there are lot of archeology resources in Alexandria,” said Skolnik. “There’s a lot going on under the ground.”