Viable Alternatives. One viable alternative, deemed the preferred alternative, is proposed for the project. The preferred alternative is the 20-Year Flexible Rehabilitation Alternative, which proposes to implement a 20-year flexible rehabilitation pavement design. Two other alternatives that were described in the PSSR have been rejected: the 40- year flexible rehabilitation alternative and the No-Build Alternative. This section focuses on the preferred alternative. The preferred alternative consists of a 20-year flexible rehabilitation pavement design, as recommended by the District 4 Office of Engineering Services on February 7, 2019. The Materials Recommendation for the preferred alternative is provided as Attachment F. The evaluation of the existing pavement condition for this project was based on review of as-built plans, Caltrans Maintenance Program 2016 Pavement Condition Report (PaveM) and photos of the roadway facility. Based on the evaluation, District 4 Materials recommends the following: For the mainline, it proposes a complete removal of 0.35' asphalt concrete (AC) and 0.25' of asphalt treated permeable base (ATPB) and replace it with 0.20' rubberized hot mix asphalt - gap graded (RHMA-G) and 0.40' hot mix asphalt type A (HMA-A) with geosynthetic pavement interlayer (GPI) embedded in between the new asphalt. See Attachment C for typical sections and attachment D for Layout plans. The recommended rehabilitation will maintain the existing profile grade. For all asphalt paved mainline shoulders, ramps and at-grade portion of connectors, it proposes removal of existing 0.35' AC and replace with 0.20' RHMA-G and 0.15' HMA-A. See Attachment C for typical sections and attachment D for Layout plans. For at grade-portion of freeway connectors and travel lanes that consists of PCC pavement, it proposes to remove the damaged PCC pavement and replace with 1.25' rapid strength concrete (RSC) with a bond breaker embedded at the replaced base level. The recommended rehabilitation mentioned above will maintain the existing profile grade. In addition to the above District 4 Materials recommendation, the preferred alternative will include the following major items of work: Upgrade 28 existing curb ramps to the current ADA standard. Repair the existing localized uneven roadway profile by injecting expanded polyurethane materials to strengthen the foundation soils beneath the pavement structural sections and the Portland Cement Concrete (PCC) approach and departure slabs (see attachment I). Replace the existing nonstandard 9 miles of median concrete barrier (Type 50) with standard concrete barrier (Type 60M). Replace about 11 miles of existing asphalt concrete dikes. Enhance safety by upgrading metal beam guardrails, installing enhanced wet/night visibility striping and shoulder rumble strips. Upgrade drainage facilities (see attachment J). Upgrade traffic signals, replace traffic loop detectors that are affected by paving work, and modify push buttons and pedestrian crossing signals per the current guidelines. Cold plane and resurface 2.9 miles of Class I bikeway parallel to SR 87 with 0.20' hot mix asphalt (type A). Maintain the existing traffic management system elements during construction. The pavement strategy for this 2R project will not degrade the geometric features or the safety of the existing facility. The project does not propose new deviations from design standards, and it is beyond the scope of the project to upgrade the existing nonstandard features to standard. The project proposes to retain the following existing nonstandard features:
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Sources: Project Baseline Agreement, Project Baseline Agreement