Local geotechnical consultant Carlton Engineering now has 2013 work sewn up with the El Dorado Irrigation District, following unanimous approval of its engineering contract Monday by the EID board.
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Last year during the fall Carlton had a $77,000 contract for design services for the $1.5 million Rock Crusher Road construction project. The 6,230-foot long road will provide access to Flume 41, a 700-foot wooden flume section that will be replaced by concrete flume sections this coming October. The road will save the district $1.5 million in helicopter charges and provide access to Flumes 42-43 and 41 in the future.
The contract Carlton was awarded Jan. 28 was for design of Flume 39-40, slated for reconstruction in October 2013. EID’s Engineering department contacted five engineering consultants with a request for proposal and only Carlton responded with a written proposal.
The supporting timbers on Flume 39-40 are rotting out. The 440-foot-long wooden flume section was last replaced in 1941, then PG&E relined it with plywood in 1979. In 2000 EID crews added a second layer of plywood, then replaced 310 feet of the non-elevated sections in 2010 and 2011. Remaining to be replaced in 2013 are 130 feet of elevated flume, portions of which are 18 feet above the ground. This will require helicopter service to deliver equipment, take out what is torn down and deliver replacement materials.
The Carlton contract for Flume 39-40 is not to exceed $98,600.
This coming fall’s reconstruction of Flume 41 has been planned since Carlton was awarded a little under $400,000 in 2008 to design Flume 41. The geotechnical firm drilled through the stacked rock wall and determined that the 19th century stack rocks could be essentially glued into place, saving about $2 million in construction costs. Flume 41 is estimated to be a $5.3 million project. That includes removing threatening boulders uphill of the flume and stripping and anchoring the hillside to prevent slides that could wipe out a section of the canal.
Carlton has surveyed all sections of the 22-mile canal, flume and tunnel system and emergency spillways and prioritized the most seriously endangered sections for replacement first.
At a September 2012 workshop of Capital Improvement Project spending over the next five years District Manager Jim Abercrombie said there are four high priority flume sections. “It levels off after that,” he said Sept. 26.
The canal and flume system provides one-third of EID’s water and generates about $8 million in electric revenue annually from a powerhouse.