"We're not jumping out of our seats, pulling our hair out, about the Marcellus Shale," said Christopher S. Crockett, director of planning and research. "We want to take a constructive, scientific approach, not polarize people."
The department's quiet strategy will be scrutinized Tuesday when City Council conducts a hearing to examine the perils and promise of Marcellus drilling.
Anti-drilling activists have lobbied council members to oppose gas development, saying that the hydraulic fracturing process used to extract gas represents an imminent threat to the city's water. The process, known as fracking, involves the high-pressure injection of water, sand, and chemicals deep underground to release gas molecules.
"I find it sort of disappointing that the Water Department is not taking a more proactive first-do-no-harm approach," said David Masur, executive director of PennEnvironment, the statewide advocacy group.
He and other activists say Philadelphia should follow the lead of the New York City Department of Environmental Protection, whose opposition to Marcellus development has galvanized political activists in the Empire State, resulting in a moratorium on fracking.
"I think the Philadelphia Water Department needs to be more assertive, like New York City," said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network, an environmental advocacy group.
Philadelphia officials say they have not taken as rigid a stand as New York City because the city's water system is distinctly different from New York's. Shale-gas drilling represents an altogether different challenge for New York, they say.
New York City's water is collected in pristine reservoirs on public land in the Catskills, which sits above the mile-deep Marcellus Shale. Any chemical spills or erosion would flow directly into the city's water system, which is unfiltered. New York City says treatment facilities would cost $8 billion to build - a strong incentive to oppose any industrial development in its watershed.
Philadelphia, by contrast, has three treatment plants that filter water drawn from the Schuylkill and the Delaware River. The river flow is a mixture of rainfall from a 10,000-square-mile watershed, and it includes agricultural runoff, any chemicals and fuel spilled on streets, and the treated wastewater from many of the region's eight million inhabitants.
"New York has no line of defense against some of these things," Crockett said. "Even turbidity or dirt would affect their operations tremendously. But we can have the water look like chocolate milk out there, and we can still treat it and make it pure."
The first Marcellus exploratory wells in the Delaware basin are now being drilled in Northeastern Pennsylvania's Wayne County, about 180 miles upstream from Philadelphia's water intakes. Any acute problems caused by spills would take about three days to work their way downstream, and the city says it would monitor the pollution as it does to the dozens of other spills that happen each year in the watershed.
While drilling operations have contaminated some household water wells immediately surrounding the gas wells, an industry spokesman argues that it's "absurd" to suggest that properly regulated fracturing might represent a long-distance threat to Philadelphia's water.
"The suggestion that Philadelphia's water is threatened by well stimulation activities that may take place in the future more than 100 miles away from the city fails even the most basic tests of science and common sense," said Chris Tucker, editor of Energy in Depth, an industry website.
Industry advocates say that in north Texas, gas operators have hydraulically fractured 14,000 gas wells, including a thousand wells in Fort Worth, without impairing public reservoirs.
Howard M. Neukrug, a deputy water commissioner, did not even mention hydraulic fracturing or potential spills in testimony last year before the Pennsylvania House Environmental Resources and Energy Committee.
"Although half of the source for Philadelphia's drinking water is underlain by Marcellus Shale," Neukrug testified, "we recognize that the extraction of natural gas is an activity that can be performed with low risk to natural resources if there is good enforcement of existing regulations, inspection of drilling sites, and restoration of sites to their pre-drilling state."
Neukrug said that the city's chief concern about Marcellus development was deforestation and soil compaction - conditions associated with any development. The runoff from lawns contains much more nitrogen, dirt, and fecal coliform than runoff from forests, he said.
"Preventing forest loss is fundamental to the long-term quality of Philadelphia's drinking-water supply," Neukrug testified.
In an interview last week, Water Department officials said they had worked quietly with the Pennsylvania Department of Environmental Protection and the Delaware River Basin Commission to strengthen drilling regulations. They said they would not be shy about raising alarms if they saw a threat.
"The Marcellus Shale is just another issue we're dealing with," said Kelly Anderson, the department's source-water protection manager.
The millions of gallons of wastewater that is recovered from gas wells remains a huge concern for water purveyors. The water contains high levels of salinity and some heavy metals. It can also include low levels of radiation.
Pennsylvania this summer strengthened regulations on discharges of wastewater from drilling operations - many gas operators now recycle the material. Officials say it's unlikely any wastewater will be permitted in the upper Delaware River.
Some water-system operators have encouraged the state to approve a severance tax to provide funds to protect water providers from the costs of coping with pollution.
"What I want to ensure as we go forward is that our customers don't have to pay for treatment for something they did not cause," said Kathy Pape, president of Pennsylvania American Water Co., which serves two million people in 370 communities.
"If there's an environmental impact," she said, "it should be built into the cost of that product - gas - as opposed to being built into the cost of the water."
Contact staff writer Andrew Maykuth at 215-854-2947 or email@example.com.