The home of Becky and Brett Snyder in Cheverly, Md.The Snyder's are in their basement where they have had to remove walls, floors, ceilings and a complete bathroom due to sewer and water problems. (Tracy A. Woodward/THE WASHINGTON POST)

To reach the only bathroom in their Cheverly house, Rebecca and Brett Snyder must pull down a clear plastic tarp’s enormous zipper and step through it.

The covering is supposed to seal off the upstairs bedrooms — and the bathroom — from the mold that took hold last year after greenish-brown sewage soaked their basement.

A new sewer line, installed as part of a court-ordered pipe replacement program in Maryland, was supposed to be the end of a messy problem. Instead, the mold was the beginning of the Snyders’ troubles, and their home life remains in limbo, they say.

Ever since the Washington Suburban Sanitary Commission replaced the Depression-era sewer pipe that caused the basement backup, rainwater has gushed underground toward their home, the Snyders say. Twice since the new sewer pipe was installed in April, the basement sump has been nearly overwhelmed, they say.

“It’s very frustrating,” Brett Snyder, 54, an economist at the Environmental Protection Agency, said as his wife teared up next to him.

WSSC officials say new sewer mains can indeed lead to more groundwater because rainwater that once percolated into the ground and into decaying pipes via cracks and holes suddenly needs a new place to go. Keeping stormwater out of new sewer pipes reduces sewage treatment costs and incidents of sewage overflowing into streams, WSSC officials say.

But WSSC spokesman I.J. Hudson said that since 1992, the utility has routinely used the same technique to replace sewer pipes and has not received any other groundwater complaints. WSSC officials say the fact that the Snyders’ home, in the 6100 block of Lombard Street, has had a sump pump for years shows that any drainage issues predated the April replacement of the 420-foot sewer pipe.

“We can’t control the migration of rain and groundwater into wet basements,” Hudson said.

Even so, some local officials are taking note of the Snyders’ complaints as the WSSC, like many utilities across the country, seeks to replace and rehabilitate its aging underground mains. The WSSC plans to replace 55 miles of sewer pipe this fiscal year.

The WSSC, which provides water and sewage-treatment services to almost 2 million residents in Montgomery and Prince George’s counties, is halfway through a 12-year legal agreement that requires it to reduce sewage backups and overflows. The agreement stemmed from a 2004 lawsuit filed by the EPA and environmental groups over sewage spills.

“There’s such a huge need to deal with our aging infrastructure,” said Del. Jolene Ivey (D-Prince George’s), who has met with the Snyders. “On the one hand, we really need these pipes replaced. On the other hand, we don’t want to create new problems at the same time.”

Cheverly Mayor Michael Callahan said he has asked to meet with WSSC officials about the Snyders’ case.

“We want to ensure that when WSSC does more work in our town that they’re very vigilant to ensure this doesn’t recur,” Calla­han said.

Rebecca Snyder said the previous owners installed the sump pump, which has worked fine for their 21 years in the house. “We’ve never had a wet basement,” she said.

But she said they noticed a significant difference after a 45-minute thunderstorm on June 1. The sump pump pumped out water three times a minute for four hours, Brett Snyder said. It continued about once every minute for eight more hours, he said. Before the sewer pipe was replaced, he said, the most often they had heard their pump activate was once a minute.

“We’d never seen that volume and force of water coming into our [sump pump] pit,” Rebecca Snyder said. “We knew we had a whole new issue.”

The Snyders said they think the problem lies with the “trenchless technology” that the WSSC used. Traditionally, utilities dig a trench, remove the old main and install a new one on a bed of gravel that supports the pipe. WSSC officials say groundwater follows the path of least resistance, which includes gravel because it’s more porous than soil.

But the WSSC and other utilities are increasingly replacing pipes without digging them up because it’s faster, less expensive and less disruptive to communities. In this case, the WSSC used a “pipe burst” method. A tool similar to a drill bit lowered through a manhole breaks up the old pipe, pushing the pieces aside in the soil. At the same time, the equipment pulls in a new pipe behind it. Unlike when a trench is dug, workers don’t install a new gravel bed.

The Snyders said they think that a lack of gravel beneath the new pipe created the problem because they are the last house down the hill before the new pipe heads into dense clay soil. Without a new bed of gravel beneath the main, they said, groundwater from uphill finds the path of least resistance at the gravel bed where the connection to their house begins. The water then follows the gravel bed beneath their own sewer pipe directly into their foundation, they say.

WSSC officials have asked the Snyders for more details about their sump pump system and the pipe connecting their house to the main sewer line that the Snyders had replaced by a private plumber in 2009.

“We’re trying to cooperate with these folks and get information,” said another WSSC spokesman, Jim Neustadt.

WSSC officials also said storm water is a county responsibility. The Snyders said Prince George’s officials have advised them to try to resolve the issue with the WSSC.

Larry Silverman, a District lawyer whom the Snyders have hired as a consultant, said the WSSC is liable for the Snyders’ drainage problem in the same way that Maryland law holds property owners responsible for any changes that cause flooding to a neighbor.

“They’re radically altering the water drainage system and not offering another system,” said Silverman, who represented the Anacostia Watershed Society in the environmental groups’ lawsuit over the WSSC’s decaying sewer pipes. “You can’t displace that much water without some consequence. It has to go somewhere.”

David Wilkins, the WSSC customer advocate assigned to the Snyders’ case, noted that no actual flooding has occurred since the pipe was replaced, even in the heavy downpours of this summer’s derecho storm. The WSSC spent about $320,000 on the pipe replacement, utility officials said. “There’s no evidence there’s a problem,” Wilkins said.

Meanwhile, the Snyders’ house, which they once referred to as “the family B&B,” remains in turmoil. The dining room where they once held family holiday dinners is filled with lamps, buckets and stacks of books from the basement. Nine rugs and basement furniture remain in storage. Rebecca Snyder said her twin sister no longer visits for fear that the mold will trigger her asthma.

The basement family room and bathroom are gone — the built-in bookshelves and pine paneling ripped out in an attempt to eradicate the mold. They haven’t restored their basement, the Snyders said, because it still has a mold problem and they think it is prone to flooding.

The Snyders said they plan to file a “notice of claim” to preserve their right to sue the WSSC about the groundwater problem. They said they’ve spent about $27,000 to try to eradicate the mold. They said they’ve spent $10,000 more on a generator that backs up their sump pump and an additional $4,500 on consulting fees to investigate the groundwater problem.

“We want to get back the ability to just live our lives where we’re not worried about a flood or a health hazard,” Rebecca Snyder said. “We want to be the family B&B again.”