How does Pittsburgh Water line existing sewer mains?

Sewers are lined with a fabric liner saturated with resin (a petroleum derived material known as styrene) that is inserted, inflated, and cured (hardened) using hot water, steam, or UV light in the existing main. This process, also referred to as Cured-In-Place Pipe or CIPP is a common process for reinforcing aging sewer mains across the country. It has been used since 1971 to reduce construction time and costs while minimizing impact to homes and businesses. Styrene is the material that allows the fabric liner to harden inside the pipe when hot water, steam, or UV light is applied.

What is styrene?

Styrene is a clear, colorless liquid that is synthesized for commercial use from petroleum and natural gas by-products. Styrene also occurs naturally in the environment and is an inherent component in small concentrations of many commonly consumed foods and beverages, such as coffee, strawberries, and cinnamon. One of the most noticeable traits of styrene is its distinct and intense odor. When applied, you may notice a sweet-smelling, glue-like odor that is detectable by the human nose at very low concentrations (0.1 parts per million). The presence of a styrene odor does not necessarily indicate a dangerous level.

View the CIPP Safety Data Sheet 

EPA Guidance and Exposure Levels for the General Public

Styrene is a material with known health considerations at certain exposure levels. The U.S. Environmental Protection Agency (EPA) has established the following guidelines or standards to inform the general public of risk at certain exposure levels.  Please see “Mitigating the odor from the application process” below for project-specific monitoring.

*ppm refers to parts per million. One part per million corresponds to one minute in two years or one drop of water in a 50-liter container. 

The AEGL or Acute Exposure Guideline Limits, are science based, short term exposure limits developed under the authority of the EPA to help emergency response agencies, industrial facilities, and public health officials understand the health risks associated with chemical exposure. 

The three AEGL levels are defined as: 

• AEGL 1: Notable discomfort or irritation, but effects are temporary and reversible. Symptoms may include headaches, nausea, sore throat or coughing, eye irritation, and fatigue.
• AEGL 2: Potential for irreversible or serious, long-lasting effects, or impaired ability to escape.
• AEGL 3: Life threatening effects or death.

These guidelines were designed for the general public and sensitive populations including infants, children, pregnant women, and the elderly. They apply to short-term exposure from 10 minutes to 8-hours.  However, it is recognized that individuals, subject to unique or idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL. 

What Will I Notice When the Sewer Liner is Applied?

When applied, you may notice a sweet-smelling odor. The odor will be most noticeable in the homes that are located on the sewer main that is being lined. Nearby residents, whose homes are not on the sewer main, may also notice the odor. The contractor will have a photoionization detector (PID) monitor on site and will document the styrene levels 15-feet from the exhaust. They will also be available to measure levels within homes when odor complaints are received. A PID monitor can measure low concentrations - parts per million (ppm) or parts per billion (ppb) of volatile organic compounds (VOCs) in the air.

Mitigating the odor during the application process 

The odor can be managed by pouring approximately one gallon of water into plumbing fixtures (e.g. sinks, toilets, etc.) and floor drains located in your basement, sealing drains with wet towels or plastic, closing windows, and ensuring proper ventilation, such as running bathroom fans. This will help to prevent odors from entering your home. 

The odor can enter your home from floor drains, cracks in foundation or other areas where air may flow. If you smell the odor in your home, ventilate the area by opening windows and doors to increase air circulation and dissipate the odor. You may also choose to leave your home and return when work is complete. If you leave your home, please be sure to take the necessary precautions to prevent the odor from entering your home while you’re gone using the guidance above. 

Learn more about odors associated with sewer lining by reading the What's That Odor Fact Sheet.

Reporting Issues 

If you have taken the listed precautions and are still experiencing an odor from within your home, please contact our emergency dispatch by calling (412) 255-2423, press 1. They will forward your name, address, and a description of what you are experiencing to our engineering team.

Addressing Concerns

Pittsburgh Water’s project engineers will receive your concern and will work with the contractor to mitigate the issue by monitoring the air quality in the area of concern for 10-minutes. The results will be compared to the levels shown in the EPA table above. If the thresholds are above EPA guidelines, additional mitigation measures will be taken, and the area will be retested. 

Residents whose homes are located on the sewer mains being lined will receive notice 7 days before the project begins and again 24 hours prior to the start of construction. These materials provide the name of the contractor, date construction will take place, and active work hours. The notice also outlines tips to prepare for construction and manage the odor. The notice also outlines tips to prepare for construction and manage the odor. 

Typically, customers are asked to

• Limit water use when the sewer is being lined, as your sewer lateral will be blocked while the liner is being installed.
• Block their sewer trap with one gallon of water to prevent sewer-liner odors from entering their basements. Sewer traps are typically found in the floor of your basement and look like a small drain. 

These materials will provide tips to manage odors that may enter their home from the exhaust point. It will also direct them to report odor or other concerns to our 24/7 emergency dispatch. 

Pittsburgh Water continues to evaluate its notification process for this and other construction projects. Customers may receive a letter, robocall, doorhanger, or a combination of notices alerting them to construction activity in their neighborhood. Representatives from our Public Affairs department are also in communication with your council office and will work with your neighborhood community organization to schedule presentations about upcoming work. 

On average, Pittsburgh Water will line approximately 12-15 miles of sewer each year. Our annual program targets the sewer system in designated neighborhoods and includes projects to rehabilitate individual sewer mains in critical need.

Work typically lasts one day, with work hours between 7:00 A.M. - 7:00 P.M.

Location Details: Throughout Pittsburgh 

Start Date: Ongoing

Completion Date: Ongoing

Work Schedule: Monday – Friday from 7:00 A.M. – 7:00 P.M. Though rare, work may extend later than regular work hours. 

Traffic Patterns: Contractors may need to close intersections to access manholes. When needed, detour signs will be posted accordingly. Generally, neighborhood disturbance is low for these kinds of projects.