PERMFILE58702

• Permit No: M1997054
• IBM Index Class Name: Permit File
• Section_Exhibit Name: EXHIBIT G WATER INFORMATION
• Media Type: D
• Archive: No

E:hibil G CMLRB 112 Permit Application
Agile Slone Systems. Inc.
• Arkansas River water. Increased TDS concentrations result from the dissolution of
minerals in soils and the outwash aquifer as water moves from rechazge to discharge
areas. Increased sodium may occur as the result of cation exchange or from mixing with
more sodium rich water.
Tallahassee Creek recharges the outwash aquifer directly along the upper part of its
course and indirectly through deep percolation of irrigation water applied in excess of
demand on about 60 acres of native hay fields. The outwash ground water flows
southerly and south-southeasterly beneath the project area, driven by a hydraulic gradient
of about 40' per 1,000'. Ground water flow velocities in the outwash aquifer beneath the
project computed from the hydraulic gradient (Figure enclosed), hydraulic conductivity
estimates given above and an assumed effective porosity of 20%, range from 80 to 400'
per day.
Hydrologically, direct impacts of the project to the outwash aquifer will be minimal. No
~~~4JJJ "cone of depression" associated with a water supply well or wells will occw or develop,
as the water sowce for the project will be pumped from the Arkansas River. Instead,
increased recharge neaz the plant area will cause the water table to rise 2 to 5'
immediately beneath that area, with lesser rises (0.5 to 1') away from the recharge area,
based on the results of an analytical model of ground water mounding built for this
evaluation.
• The limits of the outwash aquifer itself and the Arkansas River act as barriers to the
passage of hydraulic effects in the outwash aquifer further to the south. The Arkansas
River also acts as a constant head boundary where bedrock aquifers are cut by it and
where outwash/alluvium are cut by the Arkansas River. Bedrock (Dakota Group) is cut
by the Arkansas River opposite the boat take-out at the State Park; several springs
emanate from the outcrop. Further to the west, just west of the present site access bridge,
Niobraza Formation outcrops in the valley walls cut by the Arkansas River.
A possible impact to the outwash aquifer would result from more strineent administration
by the Division of Water Resources of the Tallahassee Creek and Currant Creek junior
water rights used to irrigate the hay/alfalfa fields in the west part of the project area. This
administration change would likely reduce or eliminate irrigation of the hay/alfalfa fields,
which then would reduce or eliminate a recharge source to the outwash aquifer.
Assuming 60 acres irrigated, 1.5"of irrigation water requirement and 50% irrigation
efficiency, about 90 acre-feet of recharge might be eliminated. Such reduction of
irrigation can be expected to reduce water table elevations beneath the irrigated fields and
immediately adjacent areas to the south and east. Such an action by DWR could
neeatively impact the Steer's water/sorine
5.2 Bedrock Aquifers
Bedrock aquifers in the project area include fractured Precambrain crystalline rocks, the
Dakota Group (Dakota Sandstone and Purgatoire Formation) and fractured portions of
. the Greenhorn, Carlisle and Niobrara Formations. The Graneros Shale and Piere Shale
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