Wastewater overflows from sewer systems into Maryland's rivers and streams have fallen to their lowest point since 2001, thanks in large part to this year's drought.
A total 24.2 million gallons of untreated sewage had spewed from sanitary sewer systems through September, according to a Capital News Service analysis of Maryland Department of the Environment data. That is 79 percent below the January-to-September average going back to 2001, the year the MDE began providing data on overflows.
The worst year in terms of sewage spills was 2003, when 352.4 million gallons of effluent had burst from sewers by September, largely because of Tropical Storm Isabel. The smallest amount was in another drought year, 2001, which saw 16.1 million gallons.
The CNS analysis focused on sanitary sewer systems, which carry storm water and sewage in separate pipes. It does not include spills from combined sewer systems, an older design that carries sewage and rainwater in the same pipe and easily overflows during heavy rainfall and snowmelt.
The analysis compares each year's January-to-September total because 2007 data is available only through September.
Overflows - sometimes involving millions of gallons of sewage in an incident - pose environmental and health risks, including the release of pollutants and pathogens into waterways. They are also a violation of the federal Clean Water Act.
"There should be no overflows," said Ed Merrifield, director of the Potomac Riverkeeper organization. "The sewage should be going from the toilet or the sink to the sewage treatment plant. It's supposed to be that simple."
Overflows from a sanitary sewer system generally occur when rainwater leaks into sewage pipes that cannot handle the increased flow because of roots, grease and other debris blocking the pipe.
"We get overflow when there's rain. We get too much rainwater in the sewer," said Mark Yoder, the utilities division chief for the Allegany County Department of Public Works.
Spills caused by rain are "relatively clear," Yoder said. "It's mainly rainwater that flows out," not raw sewage.
State and local officials said the drought that hit much of Maryland this year has put less stress on aging sewer pipes, resulting in fewer spilled gallons.
In the meantime, Allegany County and Baltimore City, which together accounted for 60 percent of all sanitary overflow from 2001 to 2006, are under consent decrees to fix their systems.
Rainfall through September was 8.7 inches below average in Baltimore, which also reported sewage spills of only 377,460 gallons, compared to average spills of 47.7 million gallons through September.
The drought was worse elsewhere in the state, according to the National Oceanic and Atmospheric Administration. Rainfall measured in St. Mary's County was 14.7 inches below the average; and in Montgomery County it was 15.2 inches below the average. Only Western Maryland approached normal rainfall, getting 1 to 4 inches below normal.
Gary Wyatt, chief of utility engineering for Baltimore City's Department of Public Works, acknowledged that the lack of rainfall helps, but he pointed to city efforts in recent years to repair its 100-year-old sewer system.
"There's a combination of things" that will reduce overflows, Wyatt said.
He said the city has repaired 55 of the 62 major problem spots identified in its 2002 consent decree with the MDE and the federal government. After fixing the problem spots, workers will inspect much of the city's 1,360 miles of pipes to repair cracks and clear blockages.
Under the consent decree, the city will have to make an estimated $900 million worth of repairs to update its sewer system and curb overflows by 2016.
Allegany County is also evaluating problems with its sewer system and beginning to fix some of them, including upgrades to its manholes, Yoder said.
The county leads the state this year with 16.3 million gallons of overflow - 67 percent of the total so far. It has also had some of the highest rainfall, at 30.9 inches through September, down from an average of 34.5 inches.
"Like anything else, we need more funding to make the repairs," said Yoder, who noted that Allegany does not have as many resources to draw on as Baltimore.
Overflows are down from the six-year average in the city and 19 counties this year, in many cases by more than 90 percent. Caroline County's 250 gallons this year, the lowest in the state, is 99 percent below its nine-month average of 25,640 gallons.
Wicomico County, with about 1.16 gallons in spills so far this year, and Somerset County, with 90,700 gallons, have more than tripled their average, the result of a single incident in each case.
Mechanical failure caused a three-hour sewage overflow March 20 in the parking lot of the Centre at Salisbury mall, which contributed more than 1 million gallons to Wicomico County's 2007 total, according to the MDE data.
"Pipe failure" was the cause of an 80,000-gallon spill Sept. 10 into the Jones Creek near U.S. 13 in Somerset County.
Merrifield said that jurisdictions can only solve their overflow problems with better maintenance and by spending more money on upgrades.
"Rain is an issue, but I wouldn't say it's getting any better," Merrifield said. "None of these systems are getting any newer."