Correction: Due to an error in a report by the Washington Suburban Sanitary Commission, an earlier version of this article incorrectly stated that such pipes can explode with the force of up to 200 tons of dynamite. The correct measure is up to 200 pounds of dynamite, according to the WSSC.

More than 1,700 buildings in Montgomery and Prince George’s counties are within 80 feet of the suburbs’ largest underground water mains, leaving their occupants vulnerable to potentially explosive forces­ if one of the aging pipes bursts, according to utility data.

In June, the Washington Suburban Sanitary Commission proposed requiring that most new construction within 80 feet of the largest mains be restricted to buildings that could withstand a break’s explosive ­force.

WSSC officials said they want to protect people in future buildings, citing the fact that five of the large, highly pressurized pipes have succumbed to “catastrophic failure” since 1996. The concrete mains, some dating to 1945, can explode with the force of 20 to 200 pounds of dynamite and send water rocketing at up to 90 mph, according to a WSSC analysis.

The WSSC provided the number of buildings within the proposed 80-foot buffer — 1,241 in Montgomery and 527 in Prince George’s — in response to a Washington Post inquiry. Citing security concerns, the utility denied a public records request for maps and other documents that would identify the buildings or show the largest pipes’ location.

The Luxmanor neighborhood of North Bethesda has several dozen homes and two schools on Tilden Lane, where WSSC officials have previously said that a 66-inch water pipe runs beneath the road. The pipe is the same size as a main that burst along River Road in Bethesda in 2008, requiring the rescue of motorists stranded in a torrent of water.

“It raises the question, if it’s not safe enough for new construction, how could it be safe for existing construction?” said Della Stolsworth, president of the Luxmanor Citizens Association.

WSSC officials said it would be cost-prohibitive and take more than 100 years to fully replace or move all 145 miles of the largest pipes near existing buildings.

The utility has installed acoustic equipment in about half of the pipes covered by the setback proposal, including the one under Tilden Lane, officials said. The equipment constantly monitors the pipes and signals when reinforcing steel wires are beginning to snap. In 2010, warning signs provided by the equipment enabled the WSSC to replace part of a 96-inch main in Potomac before it broke.

“We’ve taken every technical precaution we know of to ensure we have an early-warning system in place and we know what’s happening with the pipes,” said WSSC General Manager Jerry N. Johnson. “However, we don’t want to continue to create those circumstances.”

Asked why the WSSC needs a bigger setback if the acoustic equipment would warn of a weakening pipe, Johnson said, “Like anything else that’s man-made, I don’t think anyone can give you a 100 percent guarantee.”

The utility’s six commissioners, three from each county who are appointed by the county executives, postponed a vote on the issue in June and instead established a bi-county work group to devise another proposal.

“We’re in fact-finding mode,” said the commission’s chairman, Christopher Lawson of Prince George’s.

The WSSC had a 25-foot setback for years. In 2008, the utility said any development proposed within 200 feet of large pipes might have “special considerations and modifications” imposed. WSSC officials now say that language is too vague and doesn’t reflect more recent studies showing the danger zone at 80 feet.

Building industry representatives say such a setback would be unfair.

“If they want to expand their easements around these pipelines, then property owners need to be compensated for that,” said Jude Burke, a liaison to the WSSC for the Maryland-National Capital Building Industry Association.

The proposal is also drawing skepticism from some public officials. Two Montgomery County Council members who oversee infrastructure issues said the WSSC hasn’t proved the need for a more restrictive setback.

Montgomery County Council President Roger Berliner (D-Potomac-Bethesda) said he is concerned that the WSSC has assured communities such as Luxmanor that the acoustic technology provides sufficient protection from unexpected breaks.

“I don’t think they can have it both ways,” Berliner said. “If people are safe, they’re safe. If they’re not, what do you tell people in existing buildings?”

Montgomery council member Nancy Floreen (D-At Large) said an 80-foot setback would inhibit the county’s “smart growth” efforts to focus new development around existing infrastructure.

“There are always certain situations where we need extra caution,” Floreen said. “But I also think they need a dose of reality about the implications for . . . building new neighborhoods in pretty tight spots.”

Prince George’s County Executive Rushern L. Baker III (D) wrote to Johnson on Aug. 14, saying, in part, “We believe that there can be a happy medium between economic development progress and safety.”