(a) The Design-Builder shall provide all engineering, permitting support, fabrication, delivery, and construction necessary to design and repair the precast concrete arch structure(s) to properly convey San Mateo creek flows beneath Tartan Trail Road. The structure(s) shall be a ConSpan or approved equal precast arch system and shall be designed and constructed accordance with the current AASHTO LRFD Bridge Design Specifications. Where applicable, Caltrans Bridge Design Practice, Seismic Design Criteria, and Standard Details shall be used as guidance for design and detailing. Structural Requirements • Type: Precast concrete arch system with headwalls/wingwalls and foundations. • Geometry: Arch span and rise shall be sized by the Design-Builder to safely convey the design storm (100-year event) with adequate freeboard for debris passage • Loading: Design for AASHTO HL-93 live load plus applicable local design vehicle (including fire/emergency access). • Durability: Reinforcement, cover, and concrete mix shall account for chloride exposure and stream environment. • Foundations: Provide footings or other foundation system appropriate to geotechnical conditions and creek stability. The Design-Builder shall perform all necessary geotechnical investigations and analyses and provide footings or other foundation systems appropriate to the identified geotechnical conditions and creek stability. Hydraulic and Environmental Requirements • Structure shall maintain or improve existing creek conveyance and protect or enhance riparian habitat conditions in compliance with applicable regulatory permit requirements. • Hydraulic analysis shall demonstrate no increase in upstream or downstream flood risk. • Provide scour protection, cutoff walls, and bank stabilization as needed to ensure longterm stability. • Construction methods shall minimize in-creek disturbance and comply with all permit requirements. Roadway Integration • Structure shall be designed to fully integrate with the residential roadway profile, crosssection, and safety barriers. • Roadway tie-ins, approach embankments, guardrail/barrier systems, drainage, and erosion control shall be included in the design and construction scope. Deliverables • Preliminary and final stamped design drawings and calculations. • Hydraulic analysis and supporting documentation. • Shop drawings, erection plan, and QA/QC documentation for precast units. • Construction sequence plan, including environmental protection measures. • As-built drawings and certifications upon project completion.
