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<br />001536 <br /> <br />Chapter 3 - Affected Environment and Environmental Consequences <br /> <br />In the preliminary study, assumptions were made concerning the composition of the riverbed, A <br />more formal study was subsequently conducted, and riverbed samples were taken and analyzed. <br />In addition, scuba divers conducted a survey of the deeper portion of the riverbed upstream from <br />the dam (Collins, 1999). The results of these studies fundamentally agreed with the initial study, <br />except they anticipate the removal of about 2 to 3 feet of fine materials that have been deposited <br />behind the darn. It is believed that under existing conditions, these materials are flushed annually <br />during spring runoff, and are redeposited after the higher flows subside. <br /> <br />Another study done by Reclamation's Technical Service Center specifically analyzed the effects <br />of dam removal on the stability of Tunnel No.3 Landslide (Pabst, 1999). Since detailed geologic <br />information is not available for this slide, several assumptions were made as to slide geometry, <br />depth of slide plane, strength of materials, etc. The main conclusion from this study was that <br />dam removal should not have a negative impact on slide stability assuming no river scour occurs. <br />Lowering the river water surface would cause a lowering of the water table within the landslide <br />mass, which would slightly increase slide stability, A rapid drawdown of water surface or an <br />overall increase in water surface would contribute to instability of the slide. Since dam removal <br />would occur during low flow conditions, a rapid drawdown of the river surface would not occur. <br /> <br />If the darn removal alternative is selected, landslide monitoring equipment must be installed and <br />monitored for one runoff season before removal work begins. Therefore, Reclamation plans to <br />install the monitoring equipment this year to avoid waiting for another runoff season before a <br />dam removal alternative could be implemented. <br /> <br />Ownership of Dam and Lands <br /> <br />Issue: Before any modifications to the darn and site could be made, permission would <br />be needed from the dam owners and land owners to access the site and/or use their land and <br />facilities, <br /> <br />Existing Conditions: For the purposes of this project Reclamation considers two <br />separate ownership issues: 1) ownership ofthe land that could potentially be affected, and 2) <br />ownership of the Price-Stubb Diversion Darn. Land owners that may be affected by the project <br />include: <br /> <br />. Colorado Department of Transportation (CDOT) -land for access to the site for construction <br />and long-term operations and maintenance, and for use during construction <br />· Palisade Irrigation District - land under the 1-70 side of the diversion darn <br />· Mr. Eric Jacobson (FERC licensee) -land owned along the railroad side of the river at the <br />diversion darn and downstream <br />· Grand Valley Water Users Association -land along the railroad side of the dam <br />. Union Pacific Railroad - right-of-way next to the darn site; access to the site is within this <br />right-of-way <br /> <br />34 <br />