Frequently Asked Questions

1. I’m a land owner in Nevada County, how do I know if there is an abandoned mine on my property?

A: Contact the Nevada County Planning Department and ask for a map from the TOMS/PAMP database to see if any historic mines or mine features exist on your property.  These maps show you mine features from the Topographically Occurring Mine Symbols (TOMS) and Principle Areas of Mine Pollution (PAMP) datasets. Give the County your parcel number and ask them to overlay it with this map with their GIS capabilities.

This map can help to determine if there was a mine or mine feature on your property, but these maps are not 100% accurate. If you are concerned about contaminants on your property, you may want to have your soil tested for contaminants such as lead and other heavy metals.

More information is available at the CA Department of Conservation, Division of Mine Reclamation, Abandon Mine Lands Program.

2. How can I test my soil for heavy metals contamination?

A: The first step is getting a geologic consulting firm to help you test your property’s soils. The firm will help you decide where to take soil samples from, if they are deemed necessary. A professional geologist can recognize areas of mine tailings or waste rock piles and will test these or other areas suspected to have elevated levels of contamination. It can cost anywhere from $30 to $100 per sample, depending on what metals you are testing for.

Holdrege and Kull, located in Nevada City, has qualified staff who are able to provide this type of service. Search our Services Directory for more firms near you. Note: The Sierra Fund does not specifically recommend or endorse Holdrege and Kull.

3. How can I test my well water for heavy metal contamination?

A: It is important to periodically test your well water, especially if you live in an area that was historically mined. You can test your water by sending it in to a qualified lab, and they will send you the results. Cranmer Engineering, located in Grass Valley has a panel called “the whole kitchen sink” and they provide results in an easy to read format. Search our Services Directory for more water quality analysis labs near you. Note: The Sierra Fund does not specifically recommend or endorse Cranmer Engineering.

4. Am I exposing myself to mercury when I swim in the river?

A: It is unlikely that you will be exposed to unsafe levels of mercury while swimming in Sierra rivers and creeks. People are more likely to be exposed to unsafe levels of mercury by eating locally caught fish, which bio-accumulate mercury when they eat smaller fish. This is why larger, predatory fish tend to have higher mercury levels than other smaller fish that eat lower on the food chain. Mercury is a heavy metal, which sinks in its liquid elemental form to the bottom of water bodies. There, bacteria can convert elemental mercury into a more toxic form called methylmercury, which can enter the food chain.  Click for more information about mercury and human health.

5. Where can I find information about what fish are safe to eat in the Sierra?

A: In California, the state Office of Environmental Health Hazard Assessment (OEHHA) publishes fish consumption advisories for different fresh water bodies. Go to and click on the places you go fishing for advice about how much fish of each species you can safely eat from that location. If the location or kind of fish you are interested in does not have an advisory listed, it does NOT mean that it is safe to eat. It just means that not enough information has been collected for that species in that location. Follow OEHHA’s General Guidelines for locations that lack a site-specific fish advisory.

*Important Update: On August 1st, 2013 the California Office of Environmental Health Hazard Assessment released a statewide fish consumption advisory for all lakes and reservoirs that don’t have site-specific advice. View the California Lakes and Reservoirs Advisory.

6. Does selenium negate the effects of ingesting mercury from fish?

A: There is an interaction between mercury and selenium, however there has not been an epidemiological study that proves that the interaction between mercury and selenium in the human body reduces the health impacts of mercury. There are many studies that demonstrate the effects of mercury on human health but no study has yet demonstrated that selenium prevents or reduces mercury toxicity in humans. For example it may be that selenium could be protective at low levels but not at high levels, and the reason we don’t know is that we do not have any human studies on the effect of selenium on mercury poisoning. Note: Please be advised that taking selenium in higher quantities can be poisonous to humans .

7. How can I test myself for heavy metals poisoning?

A: There are several methods of analysis for mercury and other heavy metals such as urine and blood samples. Which method is used depends on the type of exposure that is suspected. Ask your health care provider what method is appropriate for you. When seeking answers about a concern related to heavy metals poisoning, look for a doctor who specializes in the field. In Sacramento, Dr. Mike Powell specializes in heavy metal exposure and removing metals from the body. Note: The Sierra Fund does not specifically recommend or endorse Dr. Mike Powell.

8. Has anyone ever died from exposure to mercury through fish ingestion?

A: Mercury exposure is more likely to result in neurological impairments rather than death. The mercury levels found in the Sierra would require someone to regularly eat high mercury fish species, for noticeable symptoms to appear.  This type of constant low level mercury exposure can result in temporary neurological deficiencies in an adult, which vary person to person. If you are a child or a woman of child bearing age, you should limit eating fish high in mercury. Exposure during pregnancy can cause long term or permanent neurological impairments in the developing fetus.

According the The Sierra Fund’s 2011 Anger Survey Report, about 9% of the people surveyed were exposed to more mercury than the State safe eating guidelines recommends. Read more about Mercury in the Sierra or check out some external resources on mercury.

9. I have a container with mercury in it at home.  What should I do with it?

A: Mercury is a hazardous substance. Therefore, it must be handled and disposed of with both personal and environmental safety in mind. Make sure your mercury is in a container with a tight fitting lid, and put that container in another container with a tight fitting lid. Clearly label “Mercury – DO NOT OPEN.”

Contact your County to find out how to dispose of hazardous materials. If you must wait for a hazardous waste collection day, store safely away from the sun, and keep them out of reach of children and pets.  To read more about how to handle mercury, visit the following Environmental Protection Agency (EPA) site:

Information for Nevada County hazardous waste collection site in Grass Valley is:

McCourtney Road Transfer Station
14741 Wolf Mountain Road
Grass Valley, Ca
(530) 274-2215

The EPA advises the public to contact public health officials as soon as possible for mercury spills greater than the amount from a broken thermometer but less than 2 tablespoons. Spills of 1 pound or more require a call to the National Response Center, the federal government’s hazardous spill center, which is staffed around the clock by the U.S. Coast Guard.

See Also:

Health Outreach Program Report – The Sierra Fund’s 1-year pilot outreach program about environmental health threats associated with abandoned mines

Fish Consumption Advisories – State-issued fish consumption advisories for lakes, reservoirs and rivers in California, many based on high mercury levels in fish

Gold Country Angler Survey – A study The Sierra Fund has been conducting since 2010 to look at exposure potential to mercury through eating locally caught fish

Peer-reviewed journal articles about mercury in the human body – Compiled by partner organization CIEA, and provided as part of their Mercury Health Toolkit