ugust 14, 2003, started out as an ordinary day," VanZandt says in a soothing voice as she switches on the projector. A map showing the transmission lines around Cleveland flashes onto the screen. "It was hot in the Midwest -- middle to upper 80s -- but nothing really out of the ordinary for August." Operators in the control room of FirstEnergy, a large utility company based in Akron, 40 miles south of Cleveland, saw nothing unusual on their computer screens.

But appearances would be deceiving in the FirstEnergy control room that day. A computer malfunction had disabled the alarm system that would have signaled problems on the grid. And sure enough, problems began to develop. At about 3:05 p.m., a 345-kilovolt line southeast of Cleveland sagged into an untrimmed tree and tripped out of service. "When you lose transmission through one line," VanZandt says, "the current it had been carrying instantly seeks another path. It takes a detour over other lines, putting a heavier burden on them." The more juice a line carries, the hotter the line gets; the hotter it gets, the more it expands and sags. A combination of high temperatures, no wind to cool off the lines, and lax tree-trimming swiftly took its toll. Two more lines serving the Cleveland area heated up, touched trees, and tripped out.

The loss of three high-voltage lines sent a surge of current through the network of lower-voltage distribution lines in the Cleveland-Akron area. These smaller lines started to overload and trip out, one by one, until 16 of them were gone. At 4:05, one hour after FirstEnergy lost its first line, a key high-voltage pathway called the Star-Sammis line overloaded and tripped out. "Then the dominoes started tipping over," says VanZandt. "Until then, it was a local problem in northern Ohio. But after the Star-Sammis line went, the whole Cleveland area was shut off from its usual supply source. There was plenty of generation, but no transmission to get it there. The resulting overloads started an unstoppable cascade. At that point, it was game over." By 4:12 p.m., the cascade had played itself out. More than 500 generating units at 265 power plants had gone down; it would take several days to get them all started again. "I've never seen a power system get that far out of control," says VanZandt. "It was one for the textbooks. They'll be reading about this in 100 years."

"Could it happen here?" I ask.

"No, I don't believe it could. And here's why." VanZandt strides purposefully to the front of the auditorium and pushes a small button. With a motorized hum, a line of tan burlap drapes covering the front wall slowly opens, revealing a giant picture window with a second-story view down onto a room the size of a large gymnasium. Arrayed across the brightly lit floor are seven doughnut-shaped desks. A person sits in the hole in the middle of each massive wooden doughnut, surrounded by a dozen computer monitors. At one end of the room, a two-story map blinks and pulsates like a billboard in Times Square. Ten casually dressed transmission operators (including two women) look up from their high-tech workstations; they all smile and wave. VanZandt waves back. "I'm so proud of these guys," she says, beaming down at her crew. "They're the best in the business. This is the O'Hare Airport of transmission control centers. We process more energy transactions here than anyone else -- up to 2,500 per day."

I ask her what kind of energy transactions. "Contracts for power transmission on our system," she explains. "Let's say there's a power plant in the northern Cascades that has 100 megawatts of surplus power. Under deregulation, they're free to sell it on the open market. A utility in Southern California might agree to buy it. So the generator in the Cascades would contract with us to use 100 megawatts of transmission capacity to carry power from its plant to the Pacific intertie, which connects our system with Los Angeles.

"Before deregulation," she adds, "every utility company built its own generating plants and the transmission lines it needed to serve its own load centers. Now it's wide open. Deregulation has changed the flow of power across the system. It's made their jobs" -- she gestures toward the people in the control room -- "much more complex. We've got to keep track of all those transactions and make sure we don't overbook the system."

FirstEnergy tried to duck responsibility for the August 14 blackout by blaming it, in effect, on deregulation. The utility claimed that high-power flow patterns across northern Ohio -- circumstances beyond its control -- made conditions on the grid precarious. That excuse simply won't wash, VanZandt says. "It was a normal summer day," she stresses -- until power lines started frying the treetops.

I ask her what could have prevented it. Trimming the trees, she replies, without missing a beat. Better tools to monitor the system would have helped as well. "At FirstEnergy they didn't have a map board," she says, motioning toward the enormous blinking billboard in the control room. "When a relay trips out a line on our system, operators hear an alarm and see lights flashing on the map. Probably the biggest thing I added to the control room after 1996, though, was that desk." She points to one of the computer atolls below the viewing window. The Remedial Action Scheme, or RAS, desk is a high-speed electronic monitoring and control tool that detects imbalances on the grid and reacts much faster than a human operator could. "That keeps small problems from cascading into big ones."

VanZandt is too modest to say so, but other people familiar with the power business see her response to the 1996 outage as a model for the kind of leadership that's needed to bring the entire electrical infrastructure of the country into the twenty-first century. "She's got remarkable vision," says Nancy Hirsh, policy director of the nonprofit Northwest Energy Coalition, a BPA watchdog. "She has an extraordinarily comprehensive view of the role of transmission in the overall picture of energy policy, conservation, and environmental stewardship. That's an unusual trait in a transmission engineer."

The "vision thing" has, in some ways, been forced upon VanZandt. Her tenure as the BPA's chief grid engineer has coincided with one of the most tumultuous periods in the organization's history. Founded in 1937 as one of Franklin D. Roosevelt's New Deal work programs, the Bonneville Power Administration is an agency of the federal government under the Department of Energy. It is not tax-supported; rather, it funds itself by marketing power from the federal hydro dams on the Columbia River, the Columbia Generating Station nuclear plant at Hanford, and several smaller power plants. It sells this power at cost to wholesale customers, most of which are public utilities in the Northwest. These wholesale customers, in turn, market the power at retail rates to homes and businesses. The BPA also operates three-fourths of the region's high-voltage transmission grid and collects fees from utilities that use the grid to transmit power of their own. When the BPA's expenses exceed its revenue, it borrows money from the U.S. Treasury, which it must repay with interest.

Since VanZandt's promotion to her present position in 1996, the BPA's financial condition has been uncertain at best. Droughts from the late 1990s through 2001 led to low water levels on the Columbia. The hydro dams in the BPA's system couldn't generate enough power to meet all its commitments. A scarcity of power to sell, combined with some poorly timed contracts to buy power at exorbitant prices, put a giant dent in the utility's finances. It went deeply into debt and retrenched, slashing costs and curtailing long-planned capital investments in its transmission system.

VanZandt and her colleagues had to be both frugal and selective in making improvements after the 1996 debacle. Their first move was to get tough on overgrown trees in their transmission corridors. The day after the blackout, she says, "not only did we have chain saws out, we had bulldozers pushing filbert trees over. We took out 6,000 trees within a couple weeks." The number of tree-related power outages dropped from 42 in 1996 to 2 in 2003. To illustrate the point, VanZandt shows me before-and-after photographs of a double row of high-voltage towers in the Midwest. The first shows silver cables suspended within zapping distance of leafy treetops; the second shows a 300-foot-wide strip of brown, denuded ground. "I know the scorched earth isn't pretty to most people," she says, "but that's what I call a beautiful power line right-of-way."