The area of central Toledo where the ground suddenly opened and gobbled a car in a gaping sinkhole was on the verge of another sewer-related street cave-in 34 years ago.
A patch of fresh pavement provides the only clue to what lies beneath the busy Detroit Avenue and Bancroft Street area. Crews last week finished fixing a 19-foot-deep hole that appeared July 3, caused by the collapse of combined antique storm and sanitary sewers.
The damage from a broken 36-inch brick line built in 1891 and a 30-inch concrete line built in 1923 illustrates what can happen to aging infrastructure buried below street level as time takes its toll.
Another problem occurred near the same intersection in 1979, when a 24-inch sanitary sewer built between 1900 and 1910 collapsed, creating a hole beneath the road — not visible from street level — that measured up to 15 feet deep.
Back then, a telltale dip in the road warned city workers that trouble lurked below.
After drilling through the street, they discovered a hole that officials at the time said could have led to the collapse of part of the intersection had it not been detected.
A second, slightly smaller hole — measuring about 10 feet deep — was discovered nearby as crews repaired the first pit. It too was caused by a sanitary sewer collapse and wasn’t visible from street level.
City officials said the two incidents in the same area are the result of an aging system.
“A lot of the system is the old brick sewers, and the brick sewers are reaching to the end of their useful life. There’s lots of parts in the city that need tender loving care,” said Don Moline, commissioner of field operations in the Department of Public Utilities.
The city is inspecting that stretch since the recent collapse to discover other faulty areas. A lack of funding has meant that work focuses on emergency responses, not long-term replacement projects, said David Welch, director of public utilities.
Neglected, old infrastructure combined with rainy weather — last month was the fourth-wettest June in Toledo since 1955 — caused a spate of recent sewer-related sinkholes. Mr. Welch estimated six incidents have occurred this year in which a car — in most cases just a tire — went through pavement.
Just last week, a woman hurt her foot by falling into a small sinkhole between the sidewalk and Nevada Street. The hole was caused by a collapsed sanitary sewer tap.
There’s a big difference between Toledo’s sinkholes and those that form naturally in karst, or areas where underlying rock can be dissolved by groundwater. When it rains, water enters the soil and erodes the rock, carving underground spaces that grow over time and may cause the ground surface to collapse.
“Since 20 percent of the country is underlain by karst, it’s impossible to avoid it,” said Randall Orndorff, a geologist at the U.S. Geological Survey.
Much of the nation’s sinkhole activity is concentrated in Florida, which lies almost entirely on layers of limestone.
Sinkholes are also common in Missouri, Kentucky, Alabama, Tennessee, Texas, and Pennsylvania. Even Ohio has karst areas scattered throughout western counties such as Ottawa, Erie, and Sandusky.
But a geological sinkhole is unlikely to form in Lucas County, said Richard Pavey, a geologist for the Ohio Department of Natural Resources.
“A lot of downtown Toledo is on 150 to 200 feet of glacial deposits on bedrock,” Mr. Pavey said. “The chances of a natural sinkhole is pretty small — the glacial stuff is just too thick.”
Instead of being caused by disintegrating rock, the sinkhole that swallowed the sedan of Pamela Knox, 60, this month was the result of infrastructural damage. Ms. Knox escaped the Detroit Avenue hole without serious injury.
Such sinkholes have happened elsewhere. A similar cavity popped up in Grand Rapids, Mich., where a water main break flooded homes and uprooted a tree in January.
In March, 2011, the collapse of a storm manhole created a 33-foot-deep sinkhole that closed down River Road at Key Street in Maumee. The street took about 25 days to repair and cost the city nearly $150,000, said Joseph Camp, Maumee’s director of public service.
In 1981, pits pockmarked Toledo.
A cave-in at Miami and Nevada streets in East Toledo occurred after a semitrailer drove over the intersection.
The culprit apparently was a break in a 1905 sanitary sewer that caused the earth under the street to wash away, likely during heavy rains, leaving a 22-foot-deep hole.
Earlier in 1981, another washout caused by a sewer line problem happened on Detroit Avenue near Arlington Avenue. It caused a hole that measured 20 feet deep. That same year, a 7-foot-deep hole developed on Boston Place.
Jared Steele, 23, of Toledo remembers the day his Ford Super Duty truck slipped into Toledo’s Scottwood Avenue. He was backing into a driveway in January, 2012, when the ground gave way beneath the front of his truck.
“I was surprised,” Mr. Steele said. “My one concern was whether the hole was going to get any bigger. I got out of the truck before more of the road got loose.”
The 8 by 10-foot hole formed after a 24-inch brick sewer collapsed.
Recent heavy rains have placed added stress on the system. “The more rain you put into the [sewer] system, the more erosive power you have,” Mr. Orndorff said. “Once there’s a crack [in a pipe], water starts eroding the soil around the pipe.”
A roughly 1,100-mile sewer system, including an estimated 200 miles of brick lines, sprawls under Toledo. The city aims to inspect up to 100 miles each year, but the actual mileage examined has fallen short of that because of equipment problems, Mr. Welch said.
Although much of the sewer system needs upgrades, the city lacks funding to replace old sewer lines, city spokesman Jen Sorgenfrei said.
In 2010, Mayor Mike Bell proposed a 13.4 percent annual increase in sanitary sewer rates. Instead, city council approved a 3 percent annual bump for sanitary sewer in 2011 plus a fixed fee for the Toledo Waterways Initiative, which funds payment on bonds and loans for infrastructure construction associated with the combined storm and sanitary sewer system, she said.
The mayor doesn’t plan to seek a rate increase after the dramatic Detroit Avenue cave-in.
“Unfortunately, it takes a major event to get people to really focus on the need and the realistic severity of the need, but I also think at this point as an administration ... we’ve taken the issue as far as we can to get action on the issue,” she said.
It cost the city about $100,000 to repair the Detroit Avenue sinkhole. Traffic rumbled through the intersection on a recent day as crews finished painting bright lines across newly poured pavement.
Customers who drive to the nearby Deli Spot have expressed concern about the road’s condition to the eatery’s owner, Ashrif Asad.
“More than anything, they’re just frightened,” he said. “The streets, they’re horrible.”
Sylvester Jackson has lived in a house on nearby Horace Street since 1964 and passed through the intersection moments after this month’s sinkhole opened. He spotted the car that had crashed into the hole.
He doesn’t remember the 1979 cave-in and said he feels safe driving the streets.
“If it doesn’t happen for another 34 years, we won’t know anything about it,” he said.
Contact Vanessa McCray at: firstname.lastname@example.org, 419-724-6065, or on Twitter @vanmccray.