Flushing with Fire Hydrant Water: Natural Gas Smell Reported Is Likely Hydrogen Sulfide Odor from Dry Deep Tunnel

Arlington Heights Public Works Department flushing water into deep tunnel on Miner Street.

Arlington Heights police, firefighters and public works officials responded just before 1:00 PM Friday to multiple odor investigations in the area surrounding Euclid Avenue and Arlington Heights Road and southeast toward Kensington Road and Gibbons. The odor was determined to be hydrogen sulfide gas that was escaping from the deep tunnel project tunnels caused by dry condition and lack of rain this season.

The odor was reported inside homes and was also detected outside in the area.

Fire department officials were checking home gas levels. Some residents reported the smell as natural gas, but the smell of hydrogen sulfide is more of a rotten egg smell. Occasionally strong waves of the odor were detected near Miner Street and Beverly and Dryden.

Public works officials were flushing water from fire hydrants directly into the deep tunnel receptacles along Miner Street from Douglas to about Gibbons, and a few other areas. The water was effective at putting a damper on the gas emanating from tunnels about 60 feet below ground.

Residents that reported an odor inside their homes included he following locations: 400 block of North Dryden, 900 block of North Chestnut … more on list from Friday developing …

No injuries, illnesses, or hazards have been reported. Firefighters were testing gas levels when residents reported smelling the odor inside their homes The odor of hydrogen sulfide is detected as low as 0.00047 ppm, which is considered the recognition threshold. This concentration is a level when 50% of people can detect the characteristic odor of hydrogen sulfide, normally described as resembling “a rotten egg”.

Hydrogen sulfide is a flammable and poisonous gas at high levels. At 10 ppm prolonged exposure can cause eye irritation. At 100 to 150 ppm, the gas paralyzes the olfactory nerve, which is the nerve that senses odor. At concentrations over 1,000 ppm, a single inhalation can cause death. No dangerous levels were detected on Friday.

Hydrogen sulfide has an auto-ignition point of 500°F. Candle flames, ventilated cigarette flames, stove elements and pilot light flames can exceed that temperature, so conditions with high concentrations of Hydrogen Sulfide can cause an explosion and fire.

Sewer gas explosions are very rare, but sewer gas recently ignited in Old City section of Philadelphia causing 100-pound manhole covers to launch into the air after an explosion. The explosion happened just before 2:00 a.m. Monday along Second and Market streets lined with bars and restaurants. After the explosions, witnesses saw thick black smoke pouring from the manholes. The source of ignition was traced to faulty underground electric power service connection. Overheated power lines caused insulation to smolder and ignite the sewer gas.

In every day situations, can also cause sewer gas to back up into a home cause by dried-out piping and plumbing fixtures. In most cases, emanating sewer gases are caused by a loss of the water barrier where traps have gone dry. Especially in drought conditions, infrequent use of a toilet, shower or floor drain can allow for rapid evaporation and entry of sewer gases into the living space. Homeowners can maintain the water barriers by using the fixtures more often or by pouring water down the drains.

Deep Tunnel
The Village of Arlington Heights participated in the Weller Creek Flood Control project which tied into the Chicago Tunnel and Reservoir Plan. This project, known as the “Deep Tunnel,” includes 109 miles of huge underground tunnels that intercept combined sewer overflow from communities and conveys it to large storage reservoirs. The closest large reservoir is the Chicago Underflow Plan (CUP) O’Hare Reservoir located just southwest of Interstate 90 and Route 83. After a storm subsides, the overflow is conveyed to treatment plants for cleaning before going to a waterway. The nearest treatment plant to the O’Hare Reservoir is the James D. Kirie Water Reclamation Plant, just northeast of Interstate 90 and Route 83.

The Deep Tunnel project, combined with flood control upgrades done by participating municipalities, controls untreated sewage combined with storm rainwater runoff so that the excess water doesn’t pollute area lakes, rivers, and streams, and flood street and basements. The CUP O’Hare Reservoir holds water and provides relief from sewer backup flooding for more than 21,000 homes and businesses in from the sewer areas of Arlington Heights, Des Plaines, and Mount Prospect. The CUP O’Hare Reservoir holds 343 million gallons of flood water storage capacity, and consists of system of aerators that activate when the reservoir starts filling with water. Aerating the reservoir keeps away organisms that release hyrdrogen sulfide gas, mehane and mercaptin. The aeration controls noxious gases and keeps odor near the reservoir at a minimum.

Commissioned in the mid-1970s, the Deep Tunnel Project is managed by the Metropolitan Water Reclamation District of Greater Chicago.

Developing …

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