Methane gas has been a “hidden” problem in many regions because methane is colorless, odorless, gas lighter than air, and highly flammable. When burned its purest form, methane gas produces carbon dioxide and water vapor. It is typically associated with wetlands, bogs, termites and other insects that break down woody material, landfills, coal-producing formations, natural saline seeps, some glacial deposits, sewage treatment, sludge digestion, and oil and gas development and natural gas storage areas. Therefore, methane has both natural and man-made sources.
Methane gas is highly flammable between a lower explosion limit (LEL) of 5.53 percent by volume in air and an upper explosion limit (UEL) of 15 percent. These percentages are equivalent to a methane concentration of 50,000 and 150,000 parts per million (ppm) in air. Below the LEL level there is not enough gas to cause an explosion. Above the UEL, there is inadequate oxygen to fuel combustion, but if the space is vented and the gas concentration drops below the UEL, the gas can become diluted enough to explode (it would require an ignition source).
There are two main types of methane found in rock formations and groundwater. The types are based on a difference in origin, not composition:
1) Thermogenic Methane, which is formed from buried organic matter at considerable depths where the rocks are compressed and heated; this includes the methane found in coal, gas from some Devonian sandstones/shales, and gas from the Marcellus and Utica formations. Methane is produced by the inorganic breakdown of organic matter (heat and pressure).
2) Microbial Methane (previous term biogenic or bacterial methane) forms closer to the surface by the action of bacteria (methanogens- bacteria that produce methane and cannot live in an environment with oxygen). This would include methane generated in landfills, lake sediments, wetlands/swamps, organic-rich glacial deposits, other recently buried organic deposits, and other carbon rich environments that are without oxygen. Microbial methane gas typically contains 20 to 30 percent less methane than is found in thermogenic natural gas.
Natural gas formed by thermogenic processes contains small amounts of ethane, propane and may contain very small amounts of butane and pentane as well as methane; almost all of natural gas is methane. Some coals, like from the anthracite region contain thermogenic gas, but some coal bed methane could be either biogenic or thermogenic gas. When bacteria generate “microbial” gas, they create mainly methane.
Whether the methane is thermogenic or biogenic (of microbial origin) can be determined by looking at the ratio of two, stable isotopes of carbon: carbon-12 and carbon-13 (this does not include the unstable radioactive isotope of carbon, carbon-14. Methanogenic (methane-producing) bacteria prefer carbon-12 over carbon-13 so any methane that they produce will have a lower relative ratio of C-13/C-12 than methane produced by thermogenesis.
We recommend that you read our pdfs on Methane:
Just like radon gas, methane gas migrates naturally up through the soil, geological materials, and through the groundwater and into your home or well. Some gas naturally enters houses through the foundation, just like radon does. When your water well is pumped, the drop in the level of the water in the wellbore reduces the pressure within the formation and permits more gas to migrate toward the wellbore. If the well is not properly vented and there happens to be substantial amounts of methane, the gas could accumulate under the well cap near the electrical connections for your well or the methane could enter with the well water and outgas (move from the water to the air) in your home.
The US Department of the Interior, Office of Surface Mining, suggests that when the level of methane gas in the water is less than 10 mg/L it is safe, but monitoring is required at 10 to 28 mg/L, and immediate action is needed above 28 mg/L. At a level of 28 mg/L the water is fully saturated with methane and it is likely that any air space in the well is at or approaching the LEL. The air and out-gassing methane, not the water, is now flammable and potentially explosive.
Methane can create a number of aesthetic and safety issues.
1) Methane is flammable and methane can displace "air" in a confined space meaning you could suffocate from lack of oxygen.
2) Methane can create "water hammer" (loud noises, banging; ordinary air can do this too) in piping.
3) Methane can cause a pressure surge. This is another potential sign of a methane or entrapped gas-related problem. Methane gas typically out-gases very quickly from water. If it takes over 2 minutes for the gas and water to separate, it is most likely carbon dioxide, not methane. If you have a lot of gas and the methane content of the water is low, it may be a mixture of carbon dioxide or air trapped within the system.
When you have the water tested, you may want to have the water field-tested for general water quality, i.e., pH, conductivity, Turbidity, temperature, oxidation-reduction potential (mv), and carbon dioxide. If there is a strong odor and the level of methane is low, you may want to test for sulfur (hydrogen sulfide; odor of rotten eggs) or propane gas if propane is used in the area. Testing for propane would be advisable if you or your neighbors use propane gas.
Note -We worked on a case in an area with natural gas development where the problem was related to a propane tank leak and not natural gas. The source of the gas was a leak in the propane delivery line. The warning signs that the propane was the source include: needing to refill the propane tank more often than its use suggests would be necessary, and dead vegetation surrounding parts of the propane delivery line. This occurred during the winter when the ground was frozen and the propane could not readily escape from the ground.
Methane is not considered toxic but it is an asphyxiant at a concentration of over 50 percent in air (it displaces oxygen). Therefore, the primary risks for methane would be asphyxiation in a confined or poorly vented area or a potential explosion hazard. As a safety measure, the natural gas industry adds mercaptans to the produced methane gas that enters the pipeline and your home. The mercaptans produce a very pungent odor so that gas leaks will be noticed; unprocessed methane gas without additives tends to have NO ODOR. It is critical to note that some unprocessed methane gas may contain long-chain hydrocarbon molecules that can create an odor.
There are no drinking water standards for methane in water but elevated levels of methane have been associated with elevated levels of salts, odors from other compounds, and some metals that are regulated as either a primary or secondary drinking water standard. The US Department of the Interior, Office of Surface Mining, suggests that when the level of methane gas in the water is less than 10 mg/L it is safe, but monitoring is required at 10 to 28 mg/L, and immediate action is needed above 28 mg/L, however, we suggest more extensive monitoring and more aggressive correction action starting at 7 mg/L.
Methane does not impart a direct health concern; it is more a safety risk because, depending on the level or concentration of gas that enters the atmosphere, it may be flammable or even explosive. Remember, methane is colorless and odorless. You should consider testing your water for methane if you have a water well or spring that is located in an area with coal or natural gas development, there are a lot of bogs or lakes, you are near a landfill, a gas pipeline, or a subsurface storage system for natural gas. You may suspect an issue with methane gas if your water is fizzy, has a lot of gas that outgasses very quickly, or you experience a water hammer (but remember that other gases trapped in the pipes, including ordinary air but not, usually, CO2,, can produce a water hammer). Elevated levels of methane may also be associated with saline water, water containing elevated levels of Iron, Manganese, Aluminum, and some rare earth metals, and water that may be chemically Corrosive to your plumbing fixtures.
Level 1 Testing is done with simple observations that an individual can make with their own senses such as sight, smell, and taste. These observations can be readily apparent or can be observed as they change over time. In addition, accessible related information about the home can also be used to narrow down the cause of your water issues.
This is not normally a problem in city water, but is a more likely problem in well water. In city water, you may experience a gas problem because of carbon dioxide, but it does not normally create a water hammer (because water pressure in the pipes keep the CO2 in solution similar to the way tightly bottled carbonated sodas do), the water is not fizzy, and it takes a little longer for the gas to escape from the water (consider how long it takes a carbonated soda to ‘go flat’ once opened).
You may have a problem with methane in your water, if:
When to Test for Methane?
This is a common question and to be honest all we can say is that the level of methane in well water is controlled by many factors and conditions and it can be highly variable. If you want to test under the conditions most favorable to the detection of methane gas migration or leakage, it would be advisable to conduct testing when one or more of the following conditions exist:
Note that all of the conditions above have one thing in common – they all prevent the methane gas from escaping from the ground into the air. More methane in the ground means more methane in the groundwater which makes it easier to detect in the well water.
The variability in methane gas concentrations may require you to sample the well three to four times per year to establish a realistic baseline and to provide some insight into background levels of methane gas. You can visually monitor the quality of the water if the amount of dissolved gases increases, i.e., if there are more bubbles and fizz, maybe it is time to check the water. If you see foam you would want to test the water for surfactants.
Level 2 Testing is Do-It-Yourself testing that can be done in your own home using a Testing Kit. After you’ve done Level 1 Testing, Level 2 Testing can confirm if your observations are correct. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment (see below) or continue to Level 3 Testing.
There are meters that can be purchased to check the methane, i.e, natural gas, level of your water and the air surrounding the well. If you suspect a methane gas problem, we suggest and recommend a methane-gas air sensor/monitor. When checking the methane level of the water, you would either measure the methane level in the headspace under the well cap or at the well vent and not directly measure the methane content in the water. If you are in an area with natural gas development, pipelines, landfills, or subsurface storage of "flammable gas", we strongly recommend certified testing of your water source.
Level 3 Testing is done through an accredited Water Testing Laboratory. With Level 3 Testing, you can order a testing kit that is used to prepare your sample and submit it to the lab. By utilizing a lab, you have the assurance that a certified water expert had analyzed your water sample. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment options (see below) or continue to Level 4 Testing - Certified Testing.
A Level 4 Certified Test Test uses chain-of-custody with a water professional coming to your home to prepare the water sample and then works with an accredited laboratory in order to certify your test results. This type of testing not only gives you the highest level of assurance in the accuracy of your test results, but can also be used as a document in legal cases. For Baseline Testing, we recommend that you use Certified Testing.
If you are planning certified testing for methane, it is critical that field screening be conducted for the LEL (Lower Explosion Limit) and methane concentration at the wellhead and the tap. In addition, it would be advisable to test for related contaminants like Aluminum, salts, Iron, other gases, and petrochemicals.