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Ken Nelson <br />December 20, 2011 <br />Page 4 <br />failures, There has fortunately, been no reported failure within Highway right-of-way, which could <br />impact the safety of tile traveling public and require emergency repairs, <br />Because of the age and condition of its construction nlilterWS, it is uncertain flow long tile inverted <br />siphon can Continue to provide service with nominal repairs and maintenance. Since the siphon is as <br />key component in conveying irrigation water to the nii�jori(y of NDIC users, serious consideration <br />should be given to replacing the siphon beforca major failure OCCUT'S that could shut down this <br />segment of the canal system without advance warning. <br />Tunnel. Hand dug as a part of the original canal system through shale, the tunnel is about 1,430 to <br />1,450 foot long and is approximately 95-foot from ground surface to the tunnel floor at the only <br />known point. The tunnel is shored with timber lintels and beams, and is at least 5'-Y high and 6'-1 <br />wide at the most limited points. It is 12- to 14-foot at its widest span, A Small diameter vertical <br />shaft with casing pipe(s), located approximately mid-length, can be accessed at the ground surface <br />from inside a shallow manhole. The vertical shaft was drilled in 1.991 in COTIJILIFICtion with a shot- <br />crete tunnel repair project, to provide as conduit for delivering cementitious material into the tunnel. <br />The vertical shaft has also reportedly been used to deploy electrical power cords during maintenance <br />and> inspection activities, and may provide some ventilation to workers. This shaft also provided <br />access for recent field surveys. <br />The west outlet portal is located approximately 500-feet east of Highway 65 along a dead-end <br />.maintenance road, about 450 -feet from the Gunnison River channel. The west portal tunnel opening <br />is secured with timber framing and cross members intended to prevent human access, that is clearly <br />marked with warning signs stating "Keep Out" and "Posted - No Trespassing ". Although posting <br />and security efforts have been made, there may be some liabilit y issues during the interim of tunnel <br />repairs. <br />The east inlet portal is not as apparent and accessible to the public, however vehicle access can be <br />made off Marshall Road, across a narrow bridge constructed of concrete and steel that spans the <br />open ditch canal upstream from tunnel entrance portal. The cast portal includes a single concrete <br />wingwall along the exposed side of tile canal above the Gunnison River. The east portal tunnel <br />entrance is not timber framed or posted to preclude unauthorized access. <br />When not in service, the tunnel has a light, steady flow of water discharging out of each portal, and <br />some ground water seepage along the soil side slopes and roof span, An excavated charmel in the <br />ditch embankment at the west portal drains seep flows across the access road. Seep water is drained <br />from the east portal through a 12-inch CMP penetration through the concrete wingwall. Ground <br />water reportedly seeps relatively unconfined in and out of tunnel walls, roof and/or floor, however, <br />water reportedly ponds in short segments, that indicates either low point(s) or less pervious soil <br />material(s) along the length of the tunnel. <br />According to the MVS survey, the tunnel floor (flowthie) may be slightly higher in elevation than <br />the inlet. Since there are only the three points of access along the tunnel, the consistency of slope is <br />unknown along the entire length of the tunnel, <br />