In Case of Emergency
Silver Lake Low Level Outlet & Tower Remediation
After the El Dorado Irrigation District completed an underwater inspection and analysis in June 2008, they concluded that the structural steel outlet tower on Silver Lake was failing. The tower, which supports the gate stem and provides a platform from which an operator can operate the gate, underwent a structural evaluation and was found to be susceptible to failure due to corrosion in the bracing as well as other critical steel support member. Accordingly, the supporting structure was deemed unsafe and unreliable for continued gate operation. The recommended remediation measures consisted of replacing the steel tower, gate, gate frame, gate stem, trash rack, and mechanical operator in-like with new materials, and complete miscellaneous concrete repairs, if necessary, in order to restore safe and reliable operation to the outlet control system.
After an emergency declaration by El Dorado Irrigation District, Syblon Reid was awarded an emergency design/build contract for modifications and repairs which included developing plans to lower and store reservoir water, assist in obtaining resource agency permits with 7 government agencies, and replace the existing low level outlet gate and a the severely deteriorated operating tower and platform.
The major challenge was to make all the repairs necessary without prematurely draining down the reservoir that sits at elevation 7300 in the High Sierra. The normal period when the reservoir is at its lowest is in the winter time (February-March) prior to spring runoff. Syblon Reid accepted this challenge to perform this work in the dead of winter.
Understanding the challenge of extreme cold weather and short windows for construction, Syblon Reid prefabricated everything possible before transporting to the site. Winter snow accumulations on site made snow removal necessary to set up construction equipment and provide access throughout the project site. Water filled bladder dams, a stream flow bypass system piping, pumps with electrical units and a filter/settling tank was subsequently delivered and set up on site. Spill containment best management practices (BMPs) were utilized as necessary to prevent fluid spills or leakage. Other BMPs were employed as necessary to prevent erosion. To the extent possible, a small amount of snow was left on the ground to minimize soil erosion.
After dewatering and demolition of the existing facilities, is was discovered that no concrete foundation existed below the tower structure other than an un-reinforced 3 to 6-inch thick concrete leveling slab which was not adequate for the new tower design. However, contingency plans were already in place, including prefabricated metal components to deal the discovery.
Despite an onslaught of winter storms and temperatures as low as -5 degrees, construction was completed in 18 days.
All work was performed without a single first aid injury, OSHA recordable incident, or time loss injury.
Project Photos
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