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Poway Landfill

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Is it safe to live in the vicinity of the landfill? Is it safe to grow fruits and vegetables in our garden? How concern should we be about letting our children and pets play in the soil?
Are there any landfill gas (methane) problems at the site? Who oversees the flare system?
When was the contamination first discovered? Why weren't residents notified sooner?
Why have the sources not been identied and removed?
Is the ambient air clean?
Do you plan to do a study of who has/had cancer in the neighborhood? Is there a cancer registry/have you called the CDC to do a study? How can I tell my story?
Are you going to test near the Garden Road Elementary School?
Should the County or someone else have disclosed anything about the landfill when I bought my house?
What are the safe levels/maximum allowable levels for benzene?
How deep did you sample? What is the basis for the sampling locations/depths?
How far can benzene travel in ground water?
How thick is the landfill cover?
Would the fire that burned over the landfill have any impact on the landfill itself or the trash within it?
How long do landfills emit gas/toxins? Has the Poway landfill reached its maximum potential? When will it become dormant?
Why were the results higher offsite than they were onsite? Did you use the same consultant and lab? Are the results reproducible?
Where will you look next if the source is not the landfill?

Is it safe to live in the vicinity of the landfill? Is it safe to grow fruits and vegetables in our garden? How concern should we be about letting our children and pets play in the soil?

We don't have any data that indicate that it is not safe to live in the vicinity of the landfill. The risk assessment show that the risk associated with the concentrations of benzene found below the ground surface are very low. The data do not show any soil contamination, they show elevated concentrations of vapors within the soil pores below the ground surface. Do what you can to prevent your and your family?s exposure to benzene, such as proper storage and use of gasoline (for lawn mowers, ATVs, etc), ensure ventilation in your house (such as leave a window or two open a crack).

Are there any landfill gas (methane) problems at the site? Who oversees the flare system?

Methane gas has not been detected off the landfill. There is no fire or explosion hazard associated with landfill gas / methane at this time. The landfill is monitored regularly for methane gas emissions, by the County Department of Public Works (DPW), the County Department of Environmental Health, Solid Waste Local Enforcement Agency (LEA) and the Air Pollution Control District. The Air Pollution Control District regulates the emissions from the flare system. The flare and the flare emissions are in compliance with all regulatory requirements.

When was the contamination first discovered? Why weren't residents notified sooner?

Testing has been ongoing at the landfill for years. The first indication of a problem offsite was when benzene was detected in soil vapor at the southern edge of the landfill property in 2004, and reported to the regulatory agencies in October 2004. This data was collected from within the landfill property but very near the property boundary, which was cause for concern. However, there were some problems with the data, and DPW wanted to collect data from offsite, so more sampling was conducted to verify and support the data. A report was submitted to the regulatory agencies in December 2005 that showed the offsite benzene detection. Additional investigation/ confirmation sampling has been ongoing since late 2004. 

Why have the sources not been identied and removed?

The source of the soil vapor contamination has not been found. The area of contamination is believed to be wide spread but at a low level throughout the landfill?it is likely not limited to a very small area. Removal of a large amount of waste from within the landfill is not currently a feasible option.

Is the ambient air clean?

Yes. All sampling conducted on the ambient (background or breathing zone air) has been clean. Nothing has been detected in the ambient air.

Do you plan to do a study of who has/had cancer in the neighborhood? Is there a cancer registry/have you called the CDC to do a study? How can I tell my story?

The information that we have received from the residents / nearby public has been very limited. We need additional information to warrant a health investigation If you would like to submit your story or submit an oral history, please send an e-mail narrative to the LEA or call the LEA for them to take down your story. Click on the contact the LEA link to send an e-mail to the LEA.

Are you going to test near the Garden Road Elementary School?

The school is located over a half mile from the toe of the landfill, and contamination is not expected to extend to the school. However, we will let the results of the ongoing sampling guide where the next rounds of sampling are needed. If the results indicate that there could be contamination trending towards the school, then sampling will be conducted in that area.

Should the County or someone else have disclosed anything about the landfill when I bought my house?

The landfill was still open when the houses were originally constructed. The County did not own the land where the houses were built, so the County was not required to do any disclosure. You need to contact an attorney to discuss any potential disclosure issues you may have for recent purchases/sales.

What are the safe levels/maximum allowable levels for benzene?

The maximum contaminant limit (MCL) for benzene in drinking water (at the tap) is 5 parts per billion. Benzene has not been detected near this level in ground water. Note that ground water in the area is NOT used for drinking. Drinking water is supplied by the City of Poway via an imported water system.

The Occupational Safety and Health Administration (OSHA) permissible exposure limit is 1000 parts per billion in air for an 8-hour day, 40-hour work week. The OSHA standard is for work place exposure and not designed for residential living conditions.

How deep did you sample? What is the basis for the sampling locations/depths?

The soil vapor sampling protocol followed the Department of Toxic Substance Control (DTSC) and Environmental Protection Agency (EPA) guidelines. Samples were generally collected from 1 ? feet below the ground surface, 5-feet below ground surface and where possible, at 10 feet below the ground surface (close to the top of ground water).

How far can benzene travel in ground water?

It has been shown in numerous studies that benzene can travel about a maximum of 250 feet down gradient in ground water before it degrades to below levels of concern (is attenuated). There are many variables to contaminant transport, such as speed of ground water movement (ground water gradient), soil/rock type, precipitation, topography, etc.

How thick is the landfill cover?

The landfill cover consists of 2-10 feet of soil cover. The cover averages 3-5 feet thick.

Would the fire that burned over the landfill have any impact on the landfill itself or the trash within it?

The fire caused some damage to the gas extraction system (it melted some of the above ground piping). Based on the data collected, the fire does not appear to have caused a change in the gas production or any other noticeable changes to the waste in the landfill.

How long do landfills emit gas/toxins? Has the Poway landfill reached its maximum potential? When will it become dormant?

There are many variables that contribute to the gas production of a landfill, including the nature of the waste, the moisture content of the waste, the climate of the area, etc. In dry areas such as southern California, the waste within landfills decays more slowly than in wetter areas, and therefore landfills here generate lower volumes of gas over longer periods of time than landfills in wet climates. It appears that the Poway landfill, which stopped taking trash over 30 years ago is beginning its decline in gas production, however it may continue to produce gasses for decades.

Why were the results higher offsite than they were onsite? Did you use the same consultant and lab? Are the results reproducible?

We do not have an explanation yet for the higher concentrations of benzene seen in soil gas offsite than onsite. The same consultant, same methodology, and same laboratory were used for all rounds of sampling. The purpose of installing the permanent probes is to be able to collect reproducible data. The results of the permanent probe installations completed so far are consistent with the results of the temporary probe results.

Where will you look next if the source is not the landfill?

DPW is actively investigating the sedimentation basin, the sewer system, storm drains and other utility conduits as potential sources/conduits of the contamination. In addition, there have been discussion regarding a large fuel spill on Poway Road that could have washed down the storm water conveyance system. This is still being researched.