Measuring Methane in Water Wells - A Tale of Two Methods from Field Screening to Passive Sampling

Mihm, Kathleen A.

Measuring Methane in Water Wells - A Tale of Two Methods from Field Screening to Passive Sampling

Tuesday, March 5, 2019: 10:35 a.m.

Kathleen A. Mihm, PG , S.S. Papadopulos & Associates Inc., Bethesda, MD

During an investigation of methane in confined freshwater aquifers ranging from 200 to 800 feet deep, a field screening method has been developed to provide an immediate assessment of methane concentrations in groundwater pumped from water supply wells using an inverted bottle and a field gas monitor. The method can be used to assess safety concerns at a private water supply well prior to receiving laboratory results from water-quality sampling for methane.

For groundwater monitoring wells, a passive sampling method has been developed for wells with methane concentrations that exceed the solubility limit using a discrete interval sampler and dissolved gas sample container. The passive method enables collection of in situ groundwater samples without loss of methane during sample collection and retrieval to the surface. Results from passive sampling, in combination with down hole dissolved gas measurements, suggest that maintaining a sealed borehole is critical for accurate measurements.

Kathleen A. Mihm, PG, S.S. Papadopulos & Associates Inc., Bethesda, MD

Kathleen Mihm, Senior Scientist, has conducted a variety of hydrogeologic investigations dealing with groundwater contamination, soil contamination, and water-supply issues in diverse settings throughout the U.S. Her expertise includes interpretation of hydrogeologic systems, water resource and water quality issues, development of groundwater models, and methane and radionuclides in groundwater and municipal water supplies.