Duquesne Light Company Continuing Search for Cable Leak

PITTSBURGH — Duquesne Light Company (DLC) crews are making progress toward identifying the leak in an underground transmission cable that spans from Brunot Island to the Strip District. On Thursday, May 2, DLC and its contractor, Underground Systems, Inc (USI), deployed plans to continue isolating the leak area along the five-mile cable.

1. Fluid Freezing

Using a liquid nitrogen “collar,” crews can freeze the liquid contents of the cable at certain points along the line. The frozen section serves as a block for the flow of fluid and isolates the leak to one side of the freeze point. This narrows the area needed to search for the leak and can be repeated until the leak location is pinpointed. The process from start to finish per section is approximately 24 hours because it requires excavation at each site and the time it takes for the fluid to freeze under the liquid nitrogen. Work began this evening on Columbus Ave. near Sedgwick St.

2. Tracer Gas Method

This involves injecting a tracer liquid into the line that mixed with the dielectric fluid. As the dielectric fluid continues to leak out of the system, so does the tracer liquid. Once the tracer escapes the high-pressure system it evaporates into a gas that diffuses in the air. The gas can be detected by a portable analyzer and its presence indicates that the leak is nearby. The technology helps crews get relatively close to the vicinity of the leak (sometimes within 10 feet) without having to excavate.

3. Additional Precaution: Boom Containment

While no fluid has been found in the rivers so far, boom containments have been placed strategically along the Ohio River as a precautionary measure and to help identify areas where a spill may have occurred because the clear fluid is difficult to identify.

Background

On Monday afternoon, April 29, Duquesne Light Company (DLC) system operators learned that an underground transmission cable on the North Side of Pittsburgh was leaking a non-toxic, clear liquid used to cool down and insulate underground cables as they safely deliver reliable power. DLC crews have been working around the clock to identify the source of the leak and have taken measures to limit potential environmental impact, including significantly slowing the rate of the leak. Currently, DLC estimates approximately 15,500 gallons of fluid, about 17% of the cable contents, have escaped.

Industry and environmental experts, as well as various local resources, have been brought in to assist in the ongoing effort. Crews are digging in the areas of Seymour Street and River Ave. today to continue pinpointing the source of the leak. No power outages or injuries have occurred as a result of this incident.

About the Substance

• Commonly referred to as dielectric fluid, the leaking substance is a clear, mineral-like liquid that presents a glossy-like sheen and is non-toxic to the public.

• It is non-flammable and non-combustible.

• In large, concentrated quantities, it may impact aquatic life.

• It has a faint mineral oil smell.

Current Response

• DLC is working with local partners, including Pittsburgh Water and Sewer Authority and Allegheny County Sanitary Authority, to identify and investigate areas where the liquid may be if it has entered any rivers.

• The company is isolating areas along the cable line (which stretches from Brunot Island to the Strip District) to determine potential leak sources using multiple methods.

DLC proactively notified local and state agencies, including the Public Utility Commission, Pittsburgh Emergency Management, Allegheny County Emergency Services, Army Corp of Engineers, U.S. Coast Guard, Environmental Protection Agency and Department of Environmental Protection.

If area residents notice a clear, yet frothy-like substance on the rivers or entering nearby waterways, they should notify the National Response Center at 1-800-424-8802.