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Redwood City Stormwater Roadmap Recommended Assessments September 2025 6-3 Schaaf & Wheeler condition, control and monitoring quality, ventilation, vibration during operation, etc. Data collection may include, but is not limited to, make, model, size, RPM, etc. Estimated Cost: $60,000 to $80,000  Green Infrastructure Green infrastructure, focusing on hydromodification infrastructure such as bioretention cells, is recommended to be documented to inform the hydraulic modeling analysis. Data collected may include the type of green infrastructure, depth, horizontal layout, etc. Condition assessed may include sediment or debris build up, infrastructure damage, etc. Estimated Cost: $30,000 to $50,000 6.1.4 Hydrologic and Hydraulic Modeling After data collection has been completed, a hydrologic and hydraulic model of the City’s conveyance system should be developed. Hydrologic modeling may be performed using HEC- HMS or similar tools, while hydraulic modeling should use HEC-RAS or equivalent software for open channels. For the pipe network, the model may build upon previous work, including the Eastern Low-Lying Area Drainage Master Plan, which used InfoWorks ICM (Wood Rodgers, 2017). The capacity assessment should evaluate system performance using hydrologic and hydraulic methods consistent with Redwood City’s Storm Drain Design Criteria and the San Mateo County Drainage Manual (San Mateo County, 2023). The analysis should simulate the 10-year and 100- year design storms. Capacity calculations should include the dynamic pipe and channel equations and supply hydraulic grade line (HGL) and energy grade line (EGL), as specified in City standards. The study should also incorporate NOAA Atlas 14 rainfall data, tidal backwater influences, and areas of frequent flooding identified through field observations and community reporting (Appendix A). In addition to assessing static capacity, the analysis should identify conveyance bottlenecks and undersized pipe segments. This effort should also assess the cumulative effect of green infrastructure, including bioretention systems and detention-based systems, and their impact on flow attenuation. Estimated Cost: $200,000 to $400,000 6.1.5 Climate Change Projections Hydrologic and hydraulic modeling should incorporate climate-adapted design criteria, including projected rainfall intensities from sources such as Cal-Adapt, projected sea-level rise based on the California Sea-Level Rise Guidance (Ocean Protection Council, 2024), and emergent groundwater conditions as described in the Regional Shoreline Adaptation Plan (OneShoreline, 2024). It must also simulate compound flooding scenarios, including the combined impact of coastal surge and rainfall, especially in tidally influenced areas. Estimated Cost: $40,000 to $60,000 11.A. - Page 26 of 53 457