16a - Laserfiche WebLink

Home Browse Search

Louden Irrigating Canal & Reservoir Company Agenda Item 16a July 15, 2008 Page 4 of 6 Four alternatives were considered: No Action Alternative The no action alternative was ruled out because even though the alternative has no immediate capital expenditures, the risk and potential future costs can be very great. A problem with a slope failure in the dam embankment dur ing the height of the irrigation season could result in the loss of the reservoir for the season. If the dam is not repaired, the Reservoir could become permanently restricted to GH 10.0, thus resulting in the pe rmanent loss of the 150 AF of water stored. Selected Alternative No. 1 – Excavation and Re-compaction Alternative 1 is the excavation of a core trench in the center of the dam in the affected area to a depth of 17 feet below the dam crest and the re -compaction of the excavated material. This alternative will cut off the seep age and add stability to the da m by removing and replacing the poorly compacted material. The estimated total project cost for this alternative is $290,000. Alternative No. 2 – Sheet Pile Wall Alternative 2 is the placement of a steel sheet pile wall along the center of the dam embankment in the affected area. The steel sheet pile wall is to extend from the cr est of the dam down into bedrock. The sheet pile wall will cut off the seepage in the zone where the wall is placed. However, it will not add stability to the dam or prevent future se ttlement of the embankment. The estimated total project cost for this alternative is $ 495,000. Alternative No. 3 – Bentonite Slurry Trench Alternative 3 is for the placemen t of a bentonite slurry trench along the center of the dam embankment in the affected area. The bentonite slu rry trench is to extend from the crest of the dam down into bedrock. The seepage in the zone where th e bentonite slurry trench is placed will be cut off due to low hydraulic conductivity of the wall. Th e bentonite slurry trench will not add stability to the dam or prevent future settlement of the em bankment. The estimated tota l project cost for this alternative is $ 375,000. Alternative No. 1 is the selected alternative. Smith Geotechnical has prepared preliminary engineering designs and cost estimat es for this alternative. The cost estimate and proposed schedule are as follows: Project Cost Estimate Engineering $57,500 Construction $193,500 20% Contingency $39,000 Total $290,000