Cottage Creek Dam Spillway Modification, Dobbins, CA

The Project consists of clearing and grubbing the site, removing the existing CMP spillway and downstream culvert, excavating a portion of the dam down to a lower, safer elevation, and installing a large concrete box culvert that will be sized to pass all Cottage Creek flows downstream past the CCD and into New Bullards Bar Reservoir. The scope of work includes, but is not limited to, the following items: Prepare the site, an area of approximately 15,000 ft2 will be cleared of all growth, such as trees logs, upturned stumps, roots of downed trees, brush, grass, weeds and all other objectionable materials within the limits of construction will be removed. Excavate approximately 16,000 cubic yards (CY) of soil and 1,500 CY of rock. Prior to culvert installation the trench will be sub-graded with controlled low strength materials (CLSM) or another approved base Geotextile fabric will be added to the trench prior to culvert installation. The length of open trench will be limited to 600 ft in advance of pipe laying. Install and construct precast 580 ft long, 8-ft by 8-ft concrete box culvert pipe with a headwall extending 5 ft above the structure will be installed in the sub-graded trench. Box culvert corners will then be cast in place. The concrete culvert will extend from the upstream toe of the dam, which is located below the ordinary high-water mark (OHWM), to County Road 169. Construct and complete project with provisions for maintaining the existing water treatment facilities in service and conveying runoff from Cottage Creek downstream of the water treatment plant and recreation facilities. Bonds required. Prevailing wages apply.