USGS Survey: Methane in water near Silt found most detections near where EnCana received record fine from the regulator for contaminating creek with benzene and methane

Survey: Methane in water near Silt by Dennis Webb, April 17, 2013, The Daily Sentinel
A review of more than a half-century worth of water-quality data in western Colorado’s Piceance Basin found that most groundwater detections of methane were in an area south of Silt, where a possible link between such detections and natural gas drilling has long been debated. … The information comes in two new USGS reports intended to provide a baseline look at groundwater and surface-water quality in the Piceance Basin to address concerns about possible changes as large-scale energy development and population growth occurs. The project was the result of a voluntary effort between energy companies and local, state and federal agencies.

The USGS compiled and evaluated data from 1,545 wells and compared them to U.S. Environmental Protection Agency drinking water standards. It also compared 347 surface-water sites to EPA and state standards in a separate report. The samples were taken between 1946 and 2009. The study area covers about 9,500 square miles from north of Rangely to south of Delta, and from Glenwood Springs to the Utah border.

There are no drinking-water standards for methane, but it can reach explosive levels in confined spaces. Methane concentrations were available for 874 wells, primarily in Garfield County, and it was detected in 24 percent of those wells, the USGS found. It said methane detections greater than 1 milligram per liter were found in 75 samples. Most methane detections and high-methane concentrations were near the Mamm Creek-Divide Creek area south of Silt, it said. The USGS noted that methane can be biogenic, resulting from microbial degradation of organic matter, or thermogenic, a process that involves heat and pressure and generally occurs far below freshwater aquifers. It said thermogenic methane’s presence in water wells can result naturally, such as through migration of gas along naturally occurring fracture zones from deeper formations, or from oil and gas operations. An ongoing study paid for by Garfield County has been looking at the methane issue south of Silt. Geoffrey Thyne, a geologist who has consulted for the county, previously has suggested a link between methane presence and drilling, but industry representatives have challenged some of his findings. The USGS noted that some studies have used methane isotopic compositions to determine its origin. It said 37 samples involving high-methane levels had isotopic methane data, which indicated the methane in the Garfield wells was from both biogenic and thermogenic sources.

An encouraging finding by the agency involved benzene, toluene, ethylbenzene and xylene, volatile organic compounds that occur in some natural gas reservoirs. It found benzene in just 11 wells out of 808 for which benzene concentrations were available. Five of those exceeded the drinking standard and were in Garfield and Rio Blanco counties. Toluene was found in 38 wells out of 808 for which data were available, but in no cases was it above the allowable standard. There were few detections of ethylbenzene or xylene, and in no case did they exceed the standard. [Emphasis added]

Overview of Groundwater Quality in the Piceance Basin, Western Colorado, 1946–2009 by J.C. Thomas and P.B. McMahon, posted March 18, 2013, USGS
Groundwater-quality data from public and private sources for the period 1946 to 2009 were compiled and put into a common data repository for the Piceance Basin. … The resulting dataset consists of the most recently collected sample from 1,545 wells, 1,007 (65 percent) of which were domestic wells. … Drinking-water standards have not been established for methane, which was detected in 24 percent of samples. Methane concentrations were greater than or equal to 1 milligram per liter in 8.5 percent of samples. Methane isotopic data for samples collected primarily from domestic wells in Garfield County indicate that methane in samples with relative high methane concentrations were derived from both biogenic and thermogenic sources. …

Overview of groundwater quality in the Piceance Basin, western Colorado, 1946–2009: U.S. Geological Survey Scientific Investigations by J. C. Thomas and P.  B. McMahon, posted March 18, 2013. Report 2012–5198, 204 p.

“Methane concentrations greater than or equal to 1 mg/L were considered high….”

799 water wells (91%) had less than 1 mg/l
65 had 1-10 mg/l
10 had more than 10 mg/l

Methane concentrations measured between 1997 and 2009 were available for 874 wells in the Piceance Basin, western Colorado, in which Methane was detected in 207 wells (24 percent)… Most samples that contained detectable methane concentrations were from Garfield County (fig. 23). Methane concentrations in the study area ranged from less than the detection limit (commonly 0.0008 mg/L) to 36.7 mg/L, and 75 values (8.5 percent) were greater than 1 mg/L (high methane). Most methane detections and methane concentrations greater than 1 mg/L were found in Garfield County in the Mamm Creek–Divide Creek area (fig. 23). A sample from a domestic well in Garfield County had the highest methane concentration (geologic unit in which well was screened was not reported) (appendix 1). The Wasatch Formation in Garfield County was the only one to have at least 10 assigned samples (table 8), and the median methane concentration for those samples was less than 0.0005 mg/L. [Emphasis added] 

[Refer also to:

Divide Creek Seep 2004 that resulted in the Colorado Oil and Gas Conservation Commission issuing a record fine against EnCana video by DivideWatch, April 2, 2004

Alleged Violations of the rules and regulations of the Colorado Oil and Gas Conservation Commission (COGCC) by EnCana Oil & Gas (USA) Inc. Cause No. 1V, Order No. 1V-276 before the Oil and Gas Conservation Commission of the State of Colorado, September 16, 2004. 29
The COGCC staff hand-delivered a Notice of Alleged Violation (“NOAV”) to EnCana on April 23, 2004. …The NOAV cited Rule 209., failure to prevent the contamination of fresh water by gas, Rule 301., failure to notify the Director when public health or safety is in jeopardy, Rule 317.i., failure to pump cement 200’ above the top of the shallowest producing horizon, Rule 324A., impacts to water quality and Rule 906.b.(3), failure to report a release to the Director.

EnCana racks up the fines by Dennis Webb, The Aspen Times, December 10, 2004
EnCana Oil & Gas was hit with another fine last week in connection with its operations in Garfield County. It has violated state regulations and laws in connection with 17 wells this year and been fined a total of $454,200. “Seventeen for this one company is quite a few,” said Morris Bell, operations manager for the Colorado Oil and Gas Conservation Commission. But the company promises next year will be different. EnCana spokesman Walt Lowry said this week EnCana’s goal is to be issued no notices of alleged violation by the COGCC in 2005. “It’s a dangerous business. Things do happen, but it’s our commitment and our goal to ensure that they don’t,”

Alleged Violations of the rules and regulations of the Colorado Oil and Gas Conservation Commission (COGCC) by EnCana Oil & Gas (USA) Inc. Cause No. 1V, DOCKET NO. 0507-OV-07 before the Oil and Gas Conservation Commission of the State of Colorado, June 10, 2005
Water samples were collected from the Amos/Walker water well on May 4, 2001, May 21, 2001, August 28, 2001, January 20, 2004 and December 20, 2004. Methane concentrations of 12, 7, 0.1, 13 and 7.9 milligrams per liter (mg/l), respectively, were detected in these samples. … On June 7, 2004, COGCC staff issued a Notice of Alleged Violation (“NOAV”) to EnCana for impacts to the Amos/Walker water well. The NOAV cited alleged violations of Rule 209., failure to protect water-bearing formations from contamination by gas, Rule 324.A.a., failure to take precautions to prevent significant adverse environmental impact to water resources and to prevent the unauthorized discharge of gas, Rule 906.a., failure to contain releases immediately upon discovery.

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