C150314 Feasibility Study - Laserfiche WebLink

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Feasibilitc Shide Farmers' High Line Canal and Reservoir Company October 2010 sidewalls that terininate at a headwall of a twin cell concrete box culvert (8-foot wide by 4-foot tall). This box culvert portion of the inverted siphon is �80 feet long. At the end of the culvert there is another headwall that begins a divided rectangular exit structure with side walls and an upward sloping apron leading to the invert of the Canal. The stn�cture ends with abrupt diverging transition walls that terminate into the FHL Canal banlc. There are 35 turnouts and auginentation locations on the FHL downstrealn of this structure. The majority of the siphon's concrete surface has erosion showing exposed aggregate. There are additional areas with erosion cut 3 to 4 inches into the concrete walls exposing steel reinforcement in some areas. The dainage is most lilcely caused from a combination of contributing factors, including the age of the concrete, round aggregate used in the concrete mix, erosion from flowing water, freeze and thaw impacts, floating debris trapped in the inlet and outlet structures, and damage from maintenance equipment. Furthernlore, several trees and willows are growing adjacent to the structure in several locations. As these trees get larger over time they can put a significai7t amount of pressure oi7 the side and transition walls of this stn�cture. To repair this structure several alternatives were considered. They are as follows: l. No Action 2. Perform repairs to the structure and tree/shrub ren�oval ($93,000) 3. Remove and replace the entire stnicture ($237,000) Alternative 1, No Action Tlus alternative was one that was not selected because inaction would eventually result in the stn�cture losing serviceability. Alternative 2, Construction of Modifications Tlus is the preferred alternative. Tlus alternative would involve select repairs to the inverted siphon inlet and more significant repairs to the outlet. The repairs to the inlet would include: ■ Removal of woody vegetation around the structure ■ Clea�7ing of areas with surface damage ■ I�IStallation of steel dowels to supplement existing corroded steel ■ Installation of cementitious patch primer ■ liistallation of lugh strength shotcrete or hand trowelled patch material Recommended repair actions for the outlet stn�cture include: ■ Removal of woody vegetation around the structure ■ Constn�ction of a new outlet structure including: - Headwall - Sloping apron to canal invert :