What to do if the ‘100-year flood’ comes every year?

Just as Tropical Storm Irene exposed vulnerabilities in Connecticut’s electric system last year, Hurricane Sandy is renewing questions about flood standards that have guided construction for decades on a wide range of coastal infrastructure.

Sandbags, silicone seals, concrete barriers and plastic sheeting were hurriedly pressed into service Monday to safeguard electrical substations built to the longstanding industry standard: the 100-year flood.

Utility executives Tony Marone (l), William Quinlan.

With coastal flooding endangering the substations for the second time in two years, state and utility officials acknowledge a greater urgency in coping with what scientists say could be an era of more frequent and more intense coastal storms.

“The 100-year standard of the past needs to be re-examined in light of changing circumstances,” said Dan Esty, the commissioner of the state Department of Energy and Environmental Protection.

A sense of those changing circumstances was especially acute Monday in Stamford, where crews hired by Connecticut Light & Power were building a protective dike around a substation threatened by coastal flooding for the first time in recent history.

In Bridgeport, United Illuminating struggled for the second time in as many years with a decision to de-energize the Congress Street substation complex to avert catastrophic damage in the face of the rising waters of Long Island Sound.

“In all likelihood, that station will flood tonight,” Gov. Dannel P. Malloy said.

UI announced at the governor’s 6 p.m. briefing that the rising tide would force it to de-energize Congress Street, which has two waterfront substations on the same parcel, and a third station near the Pequonnock River, also in Bridgeport. About 52,000 customers would be affected, mostly in Bridgeport.

Flood damage to a de-energized substation can be repaired within hours after the tide ebbs and water is pumped out, officials said. If energized when flooded, the damage is so extensive that repairs could take weeks.

Will crises become routine?

But a broader question faces the state: Do rising sea levels mean these crises will become routine until control rooms and other sensitive equipment on power stations and sewage-treatment plants are redesigned?

William Quinlan, the vice president of emergency preparedness for CL&P, said the utility is looking beyond the 100-year standard, given its experience in Stamford and with a substation in Branford that now seems vulnerable to storm surges.

“We are absolutely doing that at CL&P for these two substations, in particular,” Quinlan said. “But these are not changes one makes overnight.”

Tony Marone, a senior vice president at United Illuminating, said if the company was building a substation today, it would likely would prepare for a flood greater than UI’s current official standard — the 100-year flood, plus 1 foot.

Irene was only a tropical storm. Sandy is likely to reach Connecticut with less than hurricane-strength winds, albeit as part of a huge storm that merged with a winter system from the west.

But the bigger danger to coastal communities are sustained winds capable of driving ocean waters into Long Island Sound, which narrows like a funnel as it reaches west from the open Atlantic toward New Haven, Bridgeport and Stamford.

Water piles up as it passed through the funnel, with a surge of 11 feet capable of widespread damage above and beyond what the combination of high tides and wind-driven waves can do to coastal homes.

‘Long-term harm’

“At 11 feet or anywhere near 11 feet, we are going to lose power stations. We are going to lose sewage treatment plants,” Malloy said. “We are going to do some long-term harm to the state of Connecticut.”

The issue is seen more urgently now after a string of major storms, but it has been a matter of concern in Connecticut for years. The General Assembly directed a planning process in 2008, and a preliminary climate change plan was finished in 2011.

With the governor’s full support, Esty said, his department already was studying the issue of “adaptation” of infrastructure.

“I think one has to be very careful in saying you’ve got evidence of climate change in front of you, but I think prudence argues that what the climate scientists believe is potentially happening is an increased intensity and frequency of wind storms, including hurricanes in Connecticut,” Esty said.

A “thoughtful state government” will reflect those attitudes in its planning, he said.

Others began to focus on infrastructure design standards for shoreline communities last winter.

When Malloy formed a panel last fall to study the response to Tropical Storm Irene and an October nor’easter, many news reports focused on recommendations to increase tree-trimming near power lines, or on the need for utilities to secure line crews more expeditiously.

But the so-called Two-Storm Panel chaired by former state Economic Development Commissioner Joseph McGee also began a conversation on rising sea levels, corresponding high winds and their impact — not only on power substations and sewage treatment plants, but also on homes, roads and bridges.

1960s data

Connecticut engineering drainage standards are based on National Weather Service rainfall data based on from the 1960s, the panel reported.

Modifying and implementing tougher design standards is a process that will take years, or maybe decades, McGee said Monday, adding that these lessons from 2011 couldn’t have prevented the challenges posed now by Hurricane Sandy.

But the panel chairman added that it is important that state and municipal governments continue the focus on key environmental trends.

“The consultants who testified really pointed to a vulnerability in this state,” he said.

The Northeast Regional Climate Center at Cornell University testified last year that Connecticut is in the midst of a major increase in precipitation likely to continue over the next 40 years. It reported that sea levels are anticipated to rise by 1.5 feet by mid-century, and by three to five feet by century’s end.

The panel also noted that the water surge during Irene, which hit Connecticut on Aug. 27, 2011, came dangerously close to flooding sewage treatment facilities. And reports from the state Department of Energy and Environmental Protection found that some raw sewage may have been discharged in instances when flood waters breached sewer overflow systems.

Neither storm was considered the “big one,” at least not by the standards of wind damage, which has the potential reach across the entire state.

Irene downed about 2 percent of the state’s trees, but the storm and the nor’easter that struck Connecticut on Oct. 29, 2011 “pale in comparison to the damage that will be inflicted on Connecticut by a Category 3 hurricane with sustained winds between 100 to 120 mph,” the panel wrote.

A storm of that force, it added, could bring down 70 to 80 percent of the state’s trees.