A $5 million construction bid was let for Flume 41 by the El Dorado Irrigation District. The board voted unanimously April 22 to approve the nearly $5.8 million project.
Flume 41 is a 697-foot-long deteriorated wooden flume resting 452 feet of stacked rock installed in 1876. The rest of the flume is on less secure individual footings. Also included in the project is relining 603 feet of canal downstream from the flume.
The flume itself was last rebuilt in 1948 and relined in 1978 and 2000. The wooden flume will be replaced with precast concrete flume sections.
The project is one of the flumes identified by Carlton Engineering as a high priority replacement to insure uninterrupted water delivery. Carlton had analyzed all the flume and canal sections for EID and prioritized them.
Carlton will provide geotechnical services on this project at a cost of nearly $616,000.
Five contractors submitted bids after prequalifying with the district engineering division. ProVen Management won with a bid of $4,565,920.
Other costs include capitalized labor by EID of $140,500, contracted environmental services of $7,500 and contingency reserve of about $456,600.
The scope of the construction project is extensive. The stacked rock wall will be reinforced with rock dowels and anchors and then have grout injected. Previous coring by Carlton determined the rock wall could be essentially glued in place, saving millions. It will then be encased in a steel reinforced shotcrete wall on the face of the rock wall.
The uphill side of the flume will be scaled, meaning unstable boulders and trees will be removed as well as brush. It will be scraped down essentially to bedrock and then covered with wire mesh secured with rock anchors.
The remaining portion of the flume support will be replaced with compacted earth called Mechanically Stabilized Earthen retaining wall. Spillway 23 is used to empty this section of flume to prevent an overflow in case of a blockage. That spillway will get a new concrete foundation and a new premanufactured building to house the hydraulic operation system, water control gates, electrical and communication equipment. Electrical service for this will come from a new generator building run by a propane tank.
The propane tank will be near the end of the newly constructed canal access road, Rock Crusher Road, thus saving on helicopter replacement expenses.
Construction will begin Oct. 1 through Dec. 31 when the canal is de-watered for maintenance.
Flume 41 is part of 22 miles of flumes, canals and tunnels that bring water collected from a diversion dam on the South Fork of the American River near Kyburz. The dam collects water sent down via tributary streams from four alpine reservoirs in three counties. It supplies one-third of the district’s water and runs a 21-megawatt powerhouse. The whole system is known as Project 184, a number designated by the Federal Energy Regulatory Commission.