If the county commissioners are faced in future with a specific development application for coal mining on Oak Mesa, a recently completed study will give them specific hydrologic information on which to base their assessment of a project proposal.
A just completed HESA study (hydrologic and environmental systems analysis) of the Oak Mesa area is providing the county with subsurface geologic and hydrologic information about the area.
The $15,000 Oak Mesa study, which officials said will be made available online through the county's website, was completed by Integral Consulting, a company that has completed a similar study for all of Pitkin County.
Engineers Ken Kolm and Paul K.M. van der Heijde said at a presentation of the completed study on Sept. 24 that it was "a conceptual model of the hydrologic subsystems of the Oak Mesa area." Kolm further explained the study's purpose was to assess source waters and their protection in view of various land uses and land development patterns.
The study area extends north from the Gunnison River between the Leroux and Roatcap creek drainages. "The whole system is basically a sponge," Kolm said. The study looks at groundwater flow paths, velocities, discharge and recharge cycles, where the water comes from, and where it goes to.
An unexpected feature of the area is the system of groundwater flow at bedrock level. The area is on the southern edge of the Piceance Basin. When groundwater percolating through permeable strata hits the bedrock, it begins flowing north under the Grand Mesa and towards the Colorado River, Kolm explained, because the bedrock system tilts to the north.
Like Rogers Mesa's geology which was studied by the USGS several years ago, Oak Mesa's gravel overlay aquifers are recharged by irrigation ditches, which are called "vital to recharging the shallow ground water aquifers."
Kolm called coal seams in the area "prolific aquifers." He said that underground coal mining in the area "will require a lot of de-watering." He added that the county needs to pay attention for any possible affects of that de-watering process on Roatcap and Leroux creeks.
Susan Hansen, who ended her 20 years as county administrator just as the study was completed, told the commissioners, "This study is basic hydrology that serves as a basis for asking deeper questions of (coal mining and other specific development) applicants."blog comments powered by Disqus