Why It’s Dangerous to Explore an Underground Drainage Sewer

VIDEO: Arlington Heights firefighters search for kids walking underground in a storm drainage sewer from approximately Camelot Park to Riley School (600-800 feet laterally underground).

Three children are lucky to have escaped an underground excursion they planned today. The three children exited a drainage system near Riley School near Dryden Place and Windsor Drive, only to be met by police checking on their safety … and while firefighters wearing protective gear were searching the storm drainage sewer for them.

Confined spaces in storm drainage tunnels have several hazards and dangers that can injure or kill people in worst case scenarios. Most fatalities in confined spaces are related to atmospheric hazards.

Sewer workers are commonly exposed to gases like hydrogen disulfide, methane, ammonia and carbon monoxide. Storm drainage sewers don’t have has many chemical and noxious hazard as sanitary sewers, but some of the same gases can accumulate underground in a storm drainage sewer — gas such as methane, carbon monoxide, and hydrogen sulfide. In a study, about 53 percent of sewer workers exposed to smell that they could detect, also found that they developed sub-acute symptoms including sore throat, cough, chest tightness, breathlessness, thirst, sweating, irritability and loss of libido.

Severity of symptoms seemed to be dose related, and hydrogen sulfide (H2S) gas apparently harms lung function. A study of exposure to hydrogen sulfide in 68 sewer workers and found that the FEV1/FVC values were lower in sewer workers who had a high H2S exposure.

FEV1 is the Forced Expiratory Volume in 1 second or the volume of air that can be forcibly exhaled in one second.

FVC is Forced Vital Capacity or the volume of air that can be forcibly exhaled after full inspiration.

Even at low concentrations, hydrogen sulfide has an irritant action on the eyes and the respiratory tract. Intoxication from H2S may be hyperacute, acute, subacute or chronic. Hydrogen sulfide enters the body through the respiratory system and is rapidly oxidized to form compounds of low toxicity that can cause symptoms such as headaches, and weakness. Heavier concentrations can cause loss of consciousness, respiratory difficulty, respiratory arrest, convulsions, and death.

Besides being overcome by hydrogen sulfide or carbon monoxide or other gas, there are risk from animals. Coyotes, raccoons, rats and other rodents and animals could be hazardous in a confined space. A person could be attacked by a raccoon or coyote or exposed to infectious urine or feces in the confined space. Shoes and hands could come in contact with infectious materials, a person could suffer an animal bite, or could inhale dust or mist with airborne infectious organisms. Infectious material could also be collected on a person’s shoes, or could directly infect a person from an abrasion or laceration that occurs in the sewer. Rusted corrugated steel pipes can snag clothing, cause entrapment or entanglement, cause a laceration, or poke a person in the head.

A person could also become trapped by a hole, grate or branch wedged inside the tunnel. If trapped or incapacitated somehow by an injury, the person could drown by rapid water flowing in the tunnel during the next heavy rain or diverted water. A dangerous water rising hazard in a storm drainage sewer is known as engulfment.

Firefighters enter these spaces with self-contained breathing apparatus and other personal protection. They might not have the air flowing on the breathing apparatus, but they are ready to switch to tank air if the air monitor alarms they are carrying activate. They are in constant communication with people above ground, and their location is tracked by extending a rope that measures how many feet have extended from their entry point.

When they exit the storm drainage sewer, they are decontaminated with a shower and their clothes are immediately washed before they proceed to any other tasks or living spaces at the fire stations.

De Serres G, Levesque B, Higgins R, Major M, Laliberte D, Boulianne N, et al. Need for vaccination of sewer workers against leptospirosis and hepatitis A. Occup Environ Med. 1995;52:505–7. [PMC free article] [PubMed]

Richardson DB. Respiratory effects of chronic hydrogen sulfide exposure. Am J Ind Med. 1995;28:99–108.

Watt MM, Watt SJ, Seaton A. Episode of toxic gas exposure in sewer workers. Occup Environ Med. 1997;54:277–80. [PMC free article] [PubMed]

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