As the extent of the problems with the drainage pumps at various stations was coming into focus last week, New Orleans residents were hit with even more panic-inducing news: A control panel at the sole turbine left spinning at the power plant that fuels most of the pumps had caught fire.

The news, a literal wake-up call blasted out by city officials at 3 a.m. Thursday, laid bare the vulnerabilities of the complex drainage system managed by the Sewerage & Water Board and its potential to imminently fail the city.

The fire last Wednesday night came amid a growing crisis for the S&WB following flooding in some neighborhoods on July 22 and especially Aug. 5 amid heavy rains. That was exacerbated when it was revealed that officials at the utility had made false statements about how well the system was operating during those storms.

The list of revelations now includes pumps that were down for repairs, stations that were unstaffed and idle for hours after the rains began, and power limitations that kept some operable pumps from being turned on.

The turbine fire added a new element of concern, as the city spent days relying on a limited amount of backup power that officials said would not be enough to pump out the rain from a significant storm.

More than 50 percent of the city’s pumps rely on an archaic 25-cycle power standard generated by in-house turbines at the Carrollton power plant, a remnant from the original drainage system put in place a century ago to pump rainwater out of the city.

While the city has brought in generators to provide backup power to pump stations and is working to repair two more damaged turbines, Mayor Mitch Landrieu has warned the situation remains precarious, and restoring the power plant to full operation is going to cost millions of dollars.

The in-house power plant is something of a relic, but one that officials have defended over the years as more reliable than commercial power from Entergy — in part because it feeds electricity to the pumps through underground transmission lines. Over the years, various consultants have called for upgrading the system to a modern 60-cycle power plant, but the proposals have always been seen as cost-prohibitive. 

The power plant has long been considered the Achilles heel of the drainage system. Its major weakness is born of its age: When the pumping system was first conceived, the pumps and the steam-powered turbines that feed them were built to generate power at a frequency of 25 cycles. While there’s nothing inherently wrong with that standard, it was surpassed in the mid-20th century by 60-cycle power.

As the drainage system has grown and old pumps have been replaced, the S&WB has been left with a mix of pumps on both power standards.

The need to maintain power to the older pumps — which are some of the largest and most powerful in the system — has caused officials to leave 25-cycle power as the backbone of much of the system, even though its obsolescence means that replacement parts must be built from scratch.

About 51 percent of the total pumping capacity, including the full capacity at three major stations, relies on four 25-cycle turbines. The power plant also has a newer, 60-cycle turbine to provide backup power for the city’s water and sewer systems and the newer pumps, which are typically powered by Entergy.

City Hall officials, who have stepped in to take over communications from the S&WB since last week, when the agency's top officials were forced to resign, said they could not immediately answer questions about the total amount of power needed to run all the pumps in the system or details of how the system is supposed to operate.

“We’ve gotten, at times, conflicting information, and we want to make sure we do all due diligence to verify every technical piece of information that goes out to make sure it’s accurate,” Landrieu spokesman Tyronne Walker said.

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While the reliability of the system has long been seen as a problem, things reached a crisis stage this year, culminating in the major problems seen last week.

One turbine has been out for FEMA-funded repairs since 2012, a project that was originally expected to be completed within a year. Others developed problems in rapid succession, leaving the city briefly with no working turbines and relying solely on backup generators in March. 

The Landrieu administration told WWL-TV that the mayor had not been made aware of those failures.

The three turbines were brought back online, though it's not clear to what extent. Two of those failed again in the ensuing months, one with such severe damage to a rotor that, even after repairs, officials warned that a new, $10 million replacement will be needed in two years. Building and installing that new rotor is expected to take nearly that long.

That left only the one 25-cycle turbine working last week, until the electrical fire knocked it out for days.

The outage of all four 25-cycle turbines left the city's east bank west of the Industrial Canal — where most of the older pumps are located — particularly at risk.

While the S&WB has the ability to convert power from the current standard to the old one, there are limits on how much power supplied by Entergy can be changed over at once. The city also has begun installing generators to provide backup power, including some 25-cycle generators that would be able to provide direct power to the pumps.

Problems at the power station have been increasingly apparent since Hurricane Katrina, when it was damaged by floodwaters. FEMA pledged $272 million to repair damage to the plant. That was far less than the city had hoped for because the federal agency determined that the poor condition of the turbines in part predated the storm.

It soon became apparent that what had been seen as a reliable source of power was just barely limping along, as periodic power outages at the plant caused the water system to lose power and pressure in the pipes to drop, resulting in a series of boil-water advisories for much of the city. The water system was eventually converted to 60-cycle power, though not the drainage system.

The S&WB’s in-house 60-cycle turbine now acts as a backup to Entergy, and agency officials blamed more recent outages and boil-water advisories on issues with Entergy's power supply. Two new water towers being built at the Carrollton water plant are intended to ensure pressure will remain high in the pipes long enough to get the turbine online.

Problems with the turbines have also been directly tied to failures of the drainage pumps during storms in 2006 and 2007.

There have been calls over the years to upgrade the whole system to allow the city to provide backups through portable generators, though those have not gone anywhere.

A 2012 report by a task force looking at the S&WB recommended replacing the turbines with a 60-cycle system and installing power converters to allow the pumps to use the 60-cycle energy. The report also suggested phasing out the in-house power generation altogether, relying instead on Entergy for cheaper power.

S&WB officials have said it would cost $1 billion to replace everything that would be needed to get such an upgraded system running. They also have argued that the 25-cycle power puts less strain on the turbines and pumps, potentially extending their lifespan.

A fuller sense of the condition of the power plant will likely have to wait until outside experts can be brought in to fully analyze the system, Walker said.

"We are working to stand back up the system, get all the pumps and turbines back online, and then work quickly to get a management and capacity team in place to give us some level of confidence that this thing is operating at the level it should,” Walker said.

Follow Jeff Adelson on Twitter, @jadelson.​