Laserfiche WebLink
Away from the floodplain meadow, which has been historically irrigated by the landowner, the sur- <br />rounding hills in the Mancos Shale aze relatively barren with poor soil and vegetation. The 100 year <br />24 hour rainfall event for this azea is only 2.6 inches. <br />4. Groundwater Hydrology <br />Alluvial groundwater levels are approximately 4-10 feet from the surface in the permit azea, depend- <br />ingupon the time of year when irrigation is being used and also, depending upon the river level. <br />During irrigation season, water moves through the irrigated fields to the gravels below and then <br />along the shale contact to the river. When irrigation is off, the water still moves in the same direction <br />but to a much lesser degree. Water levels are easily seen by the existing pond in the southeast por- <br />tion of the permit azea, which verify the depths stated above. Immediately below the alluvial gravel <br />aze the thick impermeable layers of the Mancos Shale which cannot provide any usable water. The <br />gravel is approximately 17-25 feet thick below a topsoil zone of 0-1 feet thickness. The shales im- <br />mediately below the gravel deposit prevent any rechazge from the gravel into deep aquifers that <br />might be located below the shales. No water wells are located on the Farnsworth property or within <br />any reasonable distance to the permit azea. No wells downstream or upstream can be affected by the <br />proposed gravel mining. The quality of the ground water found from pit pumping is expected to be <br />similar to that of the River, which is described in the Surface Water hydrology section. When pit <br />pumping is taking place, water will likely be drawn from the river itself and also from irrigation wa- <br />ter movement along the shale contact. <br />For the 3-4 yeaz period that mining will occur in this permit area, water will be pumped from the pit <br />to the Farnsworth Collection Ditch, which will dischazge to the River. The pit water is pumped into <br />this ditch to preserve the minor wetland located at the bottom. Without this pumping, it could tem- <br />porazily dry up until the lake is filled. In the mining plan, gravel filter controls are described which <br />will ensure that the water pumped is in compliance with the discharge permit. No chemicals will be <br />used for the operation. With this pumping into the ditch, no drawdown due to pumping will affect <br />any other water body within a reasonable vicinity of the pit. <br />North Fork Pit Mazch 04 <br />