Ryan, 7-years-old and her brother James McConnon, of Old Town Alexandria, enjoy the standing water at the corner of King and Union Streets on Tuesday, October 30th, 2012. The morning high tide was not as deep as expected but still drew quite a crowd. (Tracy A. Woodward/The Washington Post)

The Washington region has begun to regain its balance after being shut down for two days by the huge storm system that devastated New York and New Jersey, although officials said flooding from Rock Creek and the Potomac and Anacostia rivers could pose a heightened health and safety hazard in the coming days.

If floodwaters spill into communities adjacent to the rivers, they will carry an estimated 240 million gallons of raw sewage discharged this week from the District’s system, which was designed to allow sewage to flow directly into the waterways when there is a heavy rainfall.

Already heavily polluted, the waterways can become unsafe to even touch for several days after a sewage overflow.

But given the fears before the storm arrived, elected officials said they were relieved that the local impact was relatively light.

“We were spared the worst,” said Maryland Gov. Martin O’Malley (D). “It’s clear we were fortunate to be on the weaker side of the storm.”

Federal, state and local governments summoned people back to work Wednesday. Metro and regional transit systems planned to return to full service. School systems around the region reopened, although the District’s Jefferson Academy; Arlington’s Barcroft Elementary; Prince George’s County’s EXCEL Academy Public Charter School and Chapel Forge Early Childhood Center; and Fairfax County’s Langley High, Holmes Middle, Sleepy Hollow Elementary and Spring Hill Elementary were all closed because they had no power.

(See what’s closed and what’s open here.)

Airlines expected to resume service from the region’s three major airports, and Amtrak said it hoped to restore limited rail service Wednesday on its busy Northeast corridor.

More than 110,000 people were without power Tuesday in the District and adjoining suburbs. By 11:20 a.m. Wednesday, the number of outages was down to about 23,000: just under 19,000 in Northern Virginia, 3,500 in Montgomery and Prince George’s counties and 372 in the District.

“Employees, retirees, contractors and crews from other companies are fully engaged in this effort, and work will continue around the clock until power is restored to every customer affected by this storm,” said Rodney Blevins, vice president at Dominion Virginia Power, which serves Northern Virginia.

Thomas H. Graham, Pepco’s regional president, said damage from the storm “is relatively localized.” All Pepco customers — who are spread through the District and parts of Maryland — should have power restored sometime Wednesday, he said.

Tracking Tropical Storm Sandy

Baltimore Gas and Electric, which serves Maryland suburbs to the east and northeast of the District, said it expected new outages over the next few days as trees and limbs weakened by the storm continued to fall on power lines.

“BGE is working as safely and quickly as possible to conduct its damage assessment and restore power to our customers,” Vice President Jeannette M. Mills said.

The collision of three weather elements produced what may be remembered as a tropical blizzard in Maryland and Virginia. A hurricane marched up from the warm waters of the Caribbean, to be caught in a vise between the cold jet stream descending from Canada and a chilly nor’easter from the North Atlantic.

The result: about half a foot of rain in the eastern parts of both states and more than two feet of snow in their western counties.

Snowfall in West Virginia that melts in the coming days could exacerbate flooding in Washington area rivers.

“We need to be mindful of what could happen over the next 48 hours,” D.C. Mayor Vincent C. Gray (D) said. “Our main threats are continued flooding.”

About 3 billion gallons of sewage overflows from the city’s system each year. It is considered such a serious pollutant that the D.C. Water and Sewer Authority is making a $2.6 billion investment to correct it.

About 12 million gallons of sewage escaped from a troubled Howard County wastewater treatment plant into the Little Patuxent River on Monday and Tuesday after a power outage shut the facility down.

That refuse from toilets, garbage disposals, dishwashers and washing machines will be driven downstream into the Chesapeake Bay as the rivers are flooded with runoff from four to 10 inches of rain. Officials warned people to avoid contact with the contaminated river water.

Floodwaters in the Potomac were expected to peak at six feet above flood stage by Wednesday evening.

By 9 p.m. Tuesday, near high tide, runoff in Old Town Alexandria had advanced about halfway into the first block of King Street, a common occurrence there in major storms. Storefronts were fortified with sandbags.

But for the most part, the Washington region has so far been spared widespread flood damage and danger, although some roads remained closed by high water. Dozens of roads were closed in Fairfax, Prince George’s and Montgomery counties. In Prince William County, road blockages were caused by fallen trees and power lines, not flooding.

In downtown Annapolis, the harbor inundated an adjacent parking lot and flooded some nearby merchants, necessitating the closure of several surrounding streets. In some places, the water appeared to be about a foot deep. But many residents said that they had expected worse and that the flooding was nothing compared with that of Hurricane Isabel, which submerged much of lower downtown Annapolis in 2003.

“This is pretty much typical,” said Pat Horn, 64, an Annapolis resident since 1987. “This can happen here after any big rainstorm.”

Fairfax County authorities lifted a mandatory evacuation order for the flood-prone Huntington area Tuesday morning once high tide had passed and it became clear there would be no flooding. On Monday night, they had ordered about 100 residents off of two streets, Arlington Terrace and Fenwick Drive, to leave their homes.

Some residents thought they could have stayed.

“If the county is so concerned about our safety, they should have done something a long time ago,” said Martha Aramayo, a retired government worker who refused to abandon her home Monday night. “I told them, ‘No, I’m staying,’ and I did. If they want to do something to help me, they can build the levee.”

In Howard, the major spill in the Little Patuxent was one of at least 19 hurricane-related sewer overflows in Maryland, state officials said. They estimated that 1 million to 2 million gallons per hour gushed from the Little Patuxent Water Reclamation Plant in Savage, near the Anne Arundel County line, during the blackout late Monday and early Tuesday.

In the District, where a quarter inch of rain can overwhelm an ancient sewer system that dates to Abraham Lincoln’s presidency, there were several overflows.

On top of that, the Washington Suburban Sanitary Commission, which serves Montgomery and Prince George’s counties, reported two overflows related to heavy rains and cracked pipes in Fort Washington.

Officials at the commission said that it will take time to determine the size of the events but that compared with disruptions in past storms, the size of the overflows was small.

During Hurricane Irene last year, 4.3 million gallons of diluted sewage overflowed in Upper Marl­boro, and 13.7 million overflowed at a treatment plant in Accokeek, according to the WSSC. The District reported that 200 million gallons overflowed.

As news of Howard’s spill spread Tuesday, County Executive Ken Ulman (D) sought to reassure residents, saying that drinking water was safe to consume and that the spill was 90 percent storm water and 10 percent raw human sewage.

But Anne Arundel health officials declared an emergency and closed their county’s portion of the river, which is downstream from Howard, warning residents to keep away until further notice. Sewage overflows carry high levels of bacteria that can lead to serious illness.

“People coming in contact with affected water should wash well with soap and warm, clean water immediately,” Anne Arundel health officials said in a statement. “Clothing should also be washed.”

The Little Patuxent treatment plant serves Columbia, but it has struggled to keep up with capacity as the community and county have grown. Until this year, residents had complained about its smell and environmentalists had criticized leaks that allowed pollution to slip into the river.

“We’ve had a history of problems with this particular plant, leaks and transparency problems,” said Fred Tutman, the Patuxent Riverkeeper.

Tutman said pipes that run between the plant and Columbia had infiltration problems — cracks that allowed water to seep in. Tutman said county officials are hard to reach when problems occur and fail to fully explain the problems when they engage with residents.

County spokesman David Nitkin disagreed, saying that Howard has responded. “While there have been problems, there have been steps to address those problems,” he said. The county spent $135 million on upgrades at the plant over the past five years, Nitkin said.

The smell of excrement that lingered every summer disappeared last year, said Myra Phelps, who lives near the plant. But Monday and Tuesday’s spill is cause for concern after the millions spent on an upgrade, she said.

“It kind of disturbs me that they’re having this kind of problem after spending all that money to upgrade,” said Phelps, a member of the Savage Community Association.