Elevated arsenic readings close popular hiking trails

Posted at 6:07 PM, Jun 28, 2017
and last updated 2017-06-28 21:07:12-04

San Diego (KGTV) - On the northwest side of the one of the City of San Diego’s more popular open space parks is a trail called Miners Ridge Loop.

It’s appropriately named because the city says the abandoned Black Mountain Arsenic Mine is located on the north slope of Black Mountain.

But, if you had any thoughts of escaping the city life for a hike on a portion of that specific trail you’d be turned away.

A sign that blocks the entrance says the trail is closed temporarily. 

If you take a closer look at the note fastened to the sign it reveals “The City of San Diego, in collaboration with its research consultants, has detected higher than normal arsenic readings at the abandoned arsenic mine in Black Mountain Open Space Park. There is no conclusive evidence that there has been or is an imminent threat to the health of the public, plants, or wildlife in and around the mine or along nearby trails as a result of this discovery.”

The press release says trails in close proximity to the mine are closed to allow researchers to conduct further testing, sampling, and monitoring. It also says research and thorough testing is expected to take months.

According to the date of the release, it was posted in early January. Six months later the sign is still up.

"Is that dangerous” one nearby resident asked Team 10.

That resident asked 10News not to use her name but says she found out about the abandoned mine when a neighbor posted about the trail closure on the social media site Nextdoor.

"My husband and my older one they went hiking and they saw everything was closed,” she said. “I’m not a hiker so, that's when they came back and said it's all closed now."

According to the city's notice, the mine was active in the 1920's and mined for naturally occurring white arsenic.

It says “many of the remnants of the mine operation still exist on the site, but the mine has not been in use for more than eight decades.”


What is Arsenic?

According to the California Environmental Health Tracking Program   “Arsenic is a toxic element that occurs naturally in the environment.  It can be found in soil, rocks, and minerals.  Arsenic cannot be destroyed; it can only change its form. In the natural environment, arsenic combines with oxygen, chlorine, and sulfur to form inorganic arsenic compounds. Inorganic arsenic naturally occurs in the earth's crust and soil in a wide range of concentrations.”

Team 10 spoke with experts who say white arsenic was typically used for pesticides.


What have local tests revealed?

A spokesperson for the City of San Diego tells 10News they expect to have results completed and released to the public in early fall.

Responding by email to questions asked by 10News he wrote, “We are working with a consultant and professionals in the field of abandoned mines and naturally occurring arsenic. Soils, plant material, water, and dust are being tested.”

Team 10 Investigator Adam Racusin asked what is the city concerned about? The city spokesperson responded, “We are currently unaware of impacts to the public and have closed the trail and initiated testing out an abundance of caution.”

When asked about the impact to the surrounding houses he wrote, “Our research to-date shows that elevated arsenic levels are likely limited to the area surrounding the arsenic mine and possibly some very limited trail surfaces on the trail that is currently closed.”


General Research into Arsenic

While researching arsenic 10News discovered superfund research programs dedicated to toxic metals and hazardous waste risk and remediation.

The head of the Superfund Research Program at the University of Arizona tells 10News their research program focuses on old mines and the public doesn’t’ realize how many of them are still around and haven’t been cleaned up in the west.

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