11 - Laserfiche WebLink

ROSEWOOD DR OLD SANTA RITA RD SANTA RITA RD OGAC WILLOW RD STONERIDGE DR WEST LAS POSITAS OGAC (*) SAMI: Stress Absorbing Membrane Interlayer OL/F: Overlay With Fabric OGAC: Open Graded Asphalt Concrete Overlay Staff has recommended that the following construction methods be utilized for this project: Overlay with Rubberized Chip Seal: This construction method involves grinding the edges of the existing pavement, placing a 3/8" layer of asphalt-rubber binder and aggregate pre-coated with paving asphalt (called rubberized chip seal) and then placing a new surface course of 1.5" to 2" thick of asphalt concrete. This method is known as Stress Absorbing Membrane Interlayer (SAMI). The rubberized chip seal interlayer provides increased flexibility of the surface and increased resistance to reflective cracking. The SAMI method will be utilized on streets that were originally scheduled to be reconstructed using the "rip-off' method, or "total recycle" method, without base stabilizer. The "rip-off' or "total recycle" method of pavement restoration would require the complete removal or grinding of the existing pavement surface. By using a stress absorbing membrane interlayer, the existing pavement surface is left in place where stable base materials occur. Staff believes that SAMI will not only minimize the construction impact on local residents, but will also minimize the potential of encountering unstable sub-grade materials during construction. Overlay: This construction method involves grinding the edges of the existing pavement, and placing a new surface course of 1.75" or 2" thickness of asphalt concrete on top of the existing pavement. Hacienda Drive, Owens Drive, Willow Street, and Rosewood Drive will receive a layer of Open Graded Asphalt Concrete (OGAC), as it will provide for noise reduction on these major streets. . Based on previous similar projects, staff is requesting a 15% project contingency in the amount of $304,557. Typical pavement change order work relates to isolated soil conditions that require its removal and replacement. Unsuitable soils are not known until such time as the pavement is removed during local base repair and the soil condition is exposed in the field, requiring either remedial treatment or removal. Therefore, it is requested that an additional 5% over the usual 10% contingency amount be authorized for this project. DISCUSSION Bids Sealed bids for this project were opened on June 24, 2008. There were four bids received, ranging from the low bid amount of $2,030,379.70 to $2,547,450, as compared to the engineer's estimate of $2,272,713 for the project. (See attached Bid Summary.) Page 3 of 4