City Tracks Source of PCBs Discovered through Foss Waterway Monitoring

Since 2001, the City has monitored the stormwater system to protect water quality in the Thea Foss Waterway. The City tracks contaminants and eliminates them before they enter the waterway.

 

In 2013, polychlorinated biphenyl (PCB) contamination was found in a residential area bordered by East 60th and East 65th streets between East I and East K streets. You can view the map of the affected areas.  After extensive testing, the City traced the contamination to a crack sealant used in a road construction project in 1975.

 

The sealant believed to be the source of PCBs is contained under the roadway and in the storm drain catch basins. These catch basins are covered by heavy metal grates. The contamination is not accessible to the public. The City does not expect to find PCBs in the water supply or elsewhere in the neighborhood.

 

Regardless, the City implemented a plan to remove the contaminated material.

 

Residents of the affected area attended a public meeting November 20, 2013, to learn more about the issue and ask questions. These materials were shown at the meeting:   
East Tacoma PCB Investigation (PDF)

Sediment Trap Results (PDF)
Shows sampling results for PCB levels in stormwater sediment in the Foss watershed

Sampling Results (PDF)
Shows sampling results for all PCB sampling conducted in the neighborhood

Sediment Trap FD 35 (PDF)
Shows the FD-35 sediment trap location and the upstream drainage area

What are PCBs?

PCBs are man-made chemicals that were widely used in construction materials and electrical products until they were banned in 1979. PCBs don't break down easily in the environment and may remain there for a very long time.

 

PCBs are ingested by fish and small organisms in water and accumulate in the food chain. So people who eat fish may be exposed to PCBs. PCBs can affect the health of people and animals if they build up in the body over a long period of time.

 

PCBs are considered legacy pollutants, meaning chemicals that remain in the environment long after they were first introduced. They typically weren't recognized as harmful when they were being used.

 

Additional Information on PCBs

U.S. Environmental Protection Agency
Washington State Department of Health

How were PCBs discovered?

Stormwater Monitoring

For more than a decade, the City has been monitoring the stormwater system throughout the Foss Waterway. This extensive monitoring is part of the $105 million waterway cleanup.

One monitoring technique involves placing sediment traps in the storm pipes. Sediment traps are essentially bottles with an open top that collect sediments carried in stormwater runoff. They are usually installed for one year before they are collected and analyzed for contamination.

The samples are tested in labs at the Center for Urban Waters. The Center for Urban Waters is a shared facility that brings together environmental scientists, analysts, engineers, and policymakers to develop creative and sustainable solutions to restore and protect urban waters.

Stormwater Pipe Cleaning
Since 2003, the City has intermittently found low levels of PCBs in sediment trap samples from the area around East 62nd Street. That prompted the City to perform a substantial amount of sampling. In 2011, the City cleaned the entire drainage system in this area to remove any legacy contamination in the storm sewer system. 

Continued Presence of PCBs
Despite the thorough cleaning, the 2012 sediment trap results again showed the presence of PCBs. This suggested either an ongoing source or a potential new source. Further investigation in fall 2012 led to the discovery of elevated PCB concentrations in the catch basins in this residential area.

Source Identified
After extensive additional sampling, the City determined that the source of the PCBs is a crack sealant used in a 1975 road construction project (Local Improvement Project #8020). While the PCB-contaminated sealant is mostly worn away now, the soil underneath the sealant is likely contaminated with PCBs as a result of the breakdown and disintegration of the sealant over the past 38 years.

The PCB-contaminated soil is entering the storm sewer system through short, two-inch drain pipes located under the gutter line and the contaminated sealant material. These small drain pipes were intended to drain groundwater under the curb and gutter to protect the roadway. This drain system, similar to a French drain, is unique to the area and likely only drains water during years with a lot of rainfall.

How much contamination did the City find?

The highest PCB reading was 260 parts per million (ppm), which came from a sample of the sealant collected inside a storm drain catch basin. The highest reading from dirt at street level was 24 ppm.

 

What does that mean? The Washington State Department of Ecology (Ecology) calls for cleanup at 1 ppm for residential properties. Cleanup levels for industrial properties are from 10 to 66 ppm. Ecology calculates the risk of 66 ppm on industrial property as one case of cancer per 100,000 workers, based on employees working 70-hour weeks, 50 weeks a year, for 30 years.

 

Project Update

The City worked with the Department of Ecology and the Environmental Protection Agency to develop a plan to address the issue. The solution involved removal of a portion of the street – along the edge of the street – so that the contaminated soils could be removed. Work was completed during two phases in 2015 and 2016.

 

Who can I contact for additional information?

Mary Henley
Senior Engineer, Surface Water
(253) 502-2113