Top-to-bottom review offered in flume tour

By From page A1 | October 02, 2013


PARTICIPANTS on the tour of the El Dorado Irrigation District's Flume 41 look over the wooden flume that will be replaced by concrete flume sections later this month, while others underneath the flume examine the foundation that was beefed up by injecting shotcrete into the rock foundation and adding in horizontal rebar as much as 60 feet long. Democrat photo by Shelly Thorene

Last month, board members and residents got an up close view of one of El Dorado Irrigation District’s most extensive capital improvement projects on a tour that included visits to Flume 41 and Reservoir A.

Coming in with a total price tag of $17.5 million, the project includes replacing the most severely degraded flume sections along the 23-mile El Dorado Canal; replacing or relining 3.4 miles of corroded pipeline between Reservoir A and Reservoir 1; installing piping in the Main Ditch; and completing a chlorine conversion project at Reservoir A Water Treatment Plant.

The four projects make up the bulk of the $19.8 million EID budgeted for capital improvement projects this year.

The tour included a winding bus trip up Rock Crusher Road. Improving the road and reinforcing the rock wall on the side of the road was part of an earlier capital improvement project that cost $1.5 million. The improvements were needed so the replacement flumes could be trucked in. In the past, at times EID has had to replaced flumes using helicopters because of a lack of access.

EID said the flume replacement was a high priority for replacement due to an adjacent landslide, unstable hand-stacked rock foundation, and degraded flume and spillway structure.

The day of the tour, crews from Carlton Engineering were busy overseeing the flume project. One of its unique challenges was to reinforce the hand-stacked rock wall that the flume rests on. Originally built 140 years ago, the wall was strengthened by drilling rebar into the wall and adjacent hillside with some of the rods driven in as much as 60 feet. This was followed by a spraying of concrete to provide additional strength and stability.

The next step in the process will be to replace almost 700 feet of wooden flumes that were last rebuilt in 1948. Some 72 concrete flume sections, each weighing 15,000 pounds, will replace them. They will be lifted into place with cranes or similar equipment, saving the district about $1.5 million to $2 million.

Those on the tour got a chance to see just how necessary the improvements were as they walked the plank that abuts the flume, the board creaking underneath, 40-degree water rushing on one side and a 10-to-12-foot drop on the other with only a splintery rail to cling to. During fair weather as well as foul, EID workers have to keep the flume open and flowing, including breaking the ice and dredging out the rocks, dead animals and branches that fall into it.

Work on the flume began in July with engineers estimating the work will be completed by mid-December. According to EID, it is the most difficult and complex flume replacement project the district has undertaken due to the scope of the project, access constraints and site conditions. The cost is estimated at $7.7 million.

A second project, but not yet begun, will replace or reline approximately 3.4 miles of 22-inch corroded pipeline that transfers water from Reservoir A in Sly Park to Reservoir 1 in Pollock Pines at a cost of $4.3 million. Originally constructed in 1978, the pipeline allows Reservoir A to be taken offline for maintenance and to optimize water supplies during drought conditions. In favorable water years, the pipeline supplies potable water to Reservoir 1 service area, thus reducing the potable water needs from Forebay Reservoir and optimizing power revenue at the El Dorado powerhouse.

Another project in the planning, but not started, is installing pipe in the three-mile long Main Ditch that conveys water from Forebay Reservoir to the Reservoir 1 Water Treatment Plant. The ditch is currently an unlined earthen canal. Piping will reduce water losses due to seepage and evaporation and will improve the quality of the water. Some initial planning work has begun on the project, which is estimated to cost $3.4 million. It’s expected to be completed sometime in 2019.

The last related project is the chlorine conversion of Reservoir A Water Treatment Plant, which will cost an estimated $2.1 million and will be completed next year. The project includes putting in two new 10,500-gallon tanks for sodium hypochlorite storage plus new liquid feed pumps. With the conversion to liquid sodium hypochlorite, the needs for pH adjustment are reduced and a simpler liquid sodium hydroxide feed system can be installed. In addition, once the new system is online, the old chlorine gas storage and feed equipment will be removed.

Improvements are also being made to the water treatment plant itself replacing parts of the roof, improving containment and process monitoring.

Contact Dawn Hodson at 530-344-5071 or [email protected] Follow @DHodsonMtDemo on Twitter.

Dawn Hodson

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