DEL NORTE — Drafters of a hydrogeology study for Rio Grande County are recommending further study and precaution in relation to potential oil/gas drilling activity in the county.
The study is now publicly available, and its authors will hold a public meeting regarding their findings at 6 p.m. on Monday, January 7 at the Rio Grande County Annex in Del Norte.
“The study team believes that the most prudent course of action is to make sure that the hydrogeology of the study area is well understood with greater accuracy than the present study allows, particularly in areas that will be of interest for petroleum development, and that certain reasonable protective measures are in place to make sure any risks of ground water contamination due to oil and gas drilling and production activities are minimized,” the authors stated in their executive summary.
The study, concluded at the end of 2012, was performed at the county’s request in response to recent applications to drill in the Del Norte area. One application relates to property in the San Francisco Creek area, the other in the Old Woman Creek area.
The hydrogeological study discussed areas with potential for oil or gas resources, described the geology of the Conejos Formation, an important bedrock aquifer, and provided baseline sampling and analysis of shallow and deep water wells near the proposed drilling sites.
“There is evidence that there are no highly impermeable formations that would serve to hydrologically separate the underlying petroleum-bearing reservoir rocks and source rocks from the shallower fresh-water aquifers used by water wells in the mountainous areas of the county,” the study summary stated.
That is why it is imperative to take protective measures against potential groundwater contamination, the authors added.
Recommendations to the county include:
• Take 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.
• Conduct further and more comprehensive water sampling of both shallow and deep aquifer wells over a longer time period. Monitoring wells should be drilled and monitored to better understand the groundwater in the deeper part of the Conejos aquifer.
• Also conduct further field investigations of rock types and their hydrologic properties within the Conejos Formation.
• 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. Chemical analyses should also be tested. State oil/gas rules call for testing of two sites within a half-mile of drill sites, but the hydrogeology study authors said that was not enough.
• An independent geologist should be allowed access to drilling locations to observe and monitor the drilling.
• Require geophysical logging of upper ranges of oil/gas boreholes before they are cased and cemented.
• Work 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.
• Encourage school districts to include water quality education in their curriculum.