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Hydrogeology report lends to decision-making process

Posted: Wednesday, Jan 9th, 2013




Courier staff writer

DEL NORTE — With the highly anticipated hydrogeology report in hand, Rio Grande County now has one more tool to make informed decisions regarding oil and gas drilling today and in the future.

Last year, the county requested the report in response to recent oil and gas interest in the Del Norte area. The Rio Grande Roundtable assisted the county with $100,000 to make the report possible because oil and gas drilling can have an effect on water systems.

Allen Davey, Bob Kirkham and Eric Harmon conducted the study, sampling 47 wells within the San Francisco Creek and Old Woman’s Creek to learn more about the western Valley's complex aquifer system.

"This is an exciting report that is going to benefit Rio Grande County," said Rio Grande County Commissioner Karla Shriver on Monday night when the county hosted a public meeting at the Rio Grande County Annex to explain the report's findings.

Rio Grande County Land Use Administrator Rose Vanderpool agreed. "I believe it is going to help all regulatory agencies with oil and gas regulations in the Valley."

Next week will prove the study's effectiveness when the county commissioners openly discuss and possibly make a decision on First Liberty Energy’s pending application during a public hearing on January 16 at 1:30 p.m. in Del Norte.

In December, the Rio Grande County Planning Commission voted to recommend approval of First Liberty’s oil/gas well in Rio Grande County with two conditions: 1) finalize emergency response plans with the local emergency response team; and 2) meet with Rio Grande County Road/Bridge Supervisor Patrick Sullivan to determine how First Liberty will mitigate road impacts.

The county commissioners will also take new Colorado Oil and Gas Conservation Commission (COGCC) under consideration. This week the COGCC is holding a three-day hearing to deliberate new oil and gas drilling rules. According to a press release, the COGCC will now require "sampling of up to four water wells within one-half mile of a new oil and gas well prior to drilling, and two more samples of each well between six and 23 months and again between five and six years, a requirement unprecedented among other states."

On Monday, Kirkham explained the ins and outs of the report, and ultimately concluded more studies are needed to further understand the Conejos Formation and the San Juan Sag, two geological areas in Rio Grande County without any signs of present contamination that oil and gas drilling could potentially alter.

"There are a lot of places we have data gaps and don't know what is going on," Kirkham said. "We sampled deep wells we thought were drawing from very deep. We picked what we thought were the best deep wells in the Conejos Formation."

In summary, the study found the Conejos Formation aquifer highly heterogeneous and anisotropic, which is highly variable in its water-bearing characteristics and directions of ground water movement. The deposits that make up the Conejos Formation vary widely in their water storage and transmitting capacity. In some areas, the Conejos Formation consists of hard, but highly fractured, lava flows and related rocks; and in other areas it is composed of layered but variable sedimentary deposits of sandstone, siltstone, and other rocks originally derived from volcanic deposits.

In addition, faulting, fracturing and igneous intrusions associated with young volcanic activity have created potential pathways for ground water movement between shallow depth zones within the Conejos aquifer, such as the zone generally less than 1,500 feet deep from which most water wells draw their water, and deeper formations.

The report's conclusions also included the fact that 3,000 constructed water wells in the area reply upon ground water pumped from the aquifers; existing water wells are 1,400 feet deep; the Conejos Formation is 5,865 feet thick and very heterogeneous; there is deep circulation of ground water in the aquifer; none of the sampled wells contained detectable concentrations of contaminates; deep sampled well had lower total dissolved solids (TDS) concentration than most shallow wells sampled; naturally occurring oil seeps in the volcanic rocks in the eastern San Juan Mountains and the San Juan Sag is a known prolific producer of oil and gas because of the source oil rocks present in the upper and lower Mancos Shale.

"That is why there is interest," Kirkham said. "There is potential for oil and gas."

One well tested in the Pinos Creek area actually turned up oil when drilled to 1,100 feet.

"It was still live, seeping out and saturating," Kirkham said.

The report's recommendations included:

• taking precautionary measures to protect ground and surface water, such as requiring petroleum exploration and production wells to be cased and grouted from the base of the Conejos Formation to the ground surface and avoid drilling within 1,000 feet of an alluvial floodplain or streambed unless precautionary measures are taken to prevent escape of drilling fluids;

• conducting further and more comprehensive water sampling of both shallow and deep aquifer wells over a longer time period;

• before during and after oil and gas drilling, water samples need to be taken of all available water wells and springs within a mile of the drill site;

• an independent geologist should be allowed access to drilling locations to observe and monitor the drilling;

• requiring geophysical logging of upper ranges of oil/gas boreholes before they are cased and cemented;

• working with state legislators to develop regulations requiring disclosure of mineral rights during real estate transactions so potential buyers are aware of split estate situations involving mineral rights severed from surface rights;

• and encouraging school districts to include water quality education in their curriculum.

After Kirkham concluded the presentation, COGCC Regional Engineer Mark Weems addressed whether a deeper well casing could be enforced. As it stands, the oil and gas wells only have to case between 1,000 and 2,000 feet. It has been suggested casing up to 4,000 feet would effectively discourage resources from seepage into the water system, but is expensive, could deter the potential economic development and could be completely unnecessary.

"The industry is evolving just like society," Weems said. "The regulations are becoming wiser... We are looking for patterns and sometimes it takes a while... These rules are going to get better with time. We are going to go with the best we have right now... We are not going to do anything that is excessive."

Hard copies of hydrogeology report are available at the Rio Grande County offices for $30, C.D. copies are $10 and it is also available online free of cost at www.riograndecounty.org under Land Use.














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