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HomeMy WebLinkAboutStorm Drain Master Plan 2026Grand Terrace Storm Drain Master Plan June 23, 2026 All Things Stormwater Storm Drain Master PlanGrand Terrace Goals of Study Discussion of Existing Conditions Current Projects Formulation of Design Criteria Proposed Improvements Project Prioritization Focused Drainage StudyGrand Terrace 2 Agenda Expand on the Current Gateway Project Drainage Study (Phase 1 Drainage Improvements). Data Collection: Known Flooded Areas, City- owned Facilities Identify Constraints Formulation of Design Criteria Proposed Improvements Prioritize Projects for Future Implementation Focused Drainage StudyGrand Terrace 3 Goals of Study Better suited for complex situations More realistic analyses/Construction Cost Savings Focused Drainage StudyGrand Terrace 4 Advanced Modeling: Hydrology/Hydraulics Focused Drainage StudyGrand Terrace 5 Why Use Advanced Modeling Focused Drainage StudyGrand Terrace 6 Why Use Advanced Modeling County Storm Drain Facilities Gage & Riverside Canal Easements Utilities Focused Drainage StudyGrand Terrace 7 Conflicts 100-year peak flow rates Improve tributary regional storm drain systems Regional Detention Basin Focused Drainage StudyGrand Terrace 8 Gateway Project (Phase 1) Focused Drainage StudyGrand Terrace 9 Gateway Project (Phase 1) Focused Drainage StudyGrand Terrace 10 SDMP Improvements (Phase 2) Focused Drainage StudyGrand Terrace 11 SDMP Improvements (Additional) Mt. Vernon (North of Barton)Grand Terrace Rd. Crossing Gage Cana/Pico Street Vivienda Avenue Focused Drainage StudyGrand Terrace 12 SDMP Improvements (GT Road Crossing) Focused Drainage StudyGrand Terrace 13 Existing Flooded Depth Results Focused Drainage StudyGrand Terrace 14 MPD (Phase 2) Flooded Depth Results Focused Drainage StudyGrand Terrace 15 Recommended Project Costs Estimates Unit Prices Contingencies Total Project Cost Estimates Focused Drainage StudyGrand Terrace 16 Project Phasing and Prioritization (Includes Phase 1 & 2) Questions / Comments? Focused Drainage StudyGrand Terrace 17 Cities Redlands La Quinta Rancho Palos Verdes Santa Ana Anaheim Coachella San Diego Oxnard Palm Desert Focused Drainage StudyGrand Terrace 18 Agency Acceptance Counties Los Angeles San Bernardino Riverside Orange San Diego National FEMA US EPA USACE 1D Hydrodynamic modeling •Generate inflow hydrographs (internal or external) •Dynamic wave routing (St. Venant flow equations) •Simulates networks of open and closed conduits Focused Drainage StudyGrand Terrace 19 Computer Modeling Options Coupled 1 & 2D Hydrodynamic modeling •2D surface flow + 1D subsurface/open channels •Rain-on-grid or inflow hydrographs •Models bifurcation within sub-watershed Focused Drainage StudyGrand Terrace 20 Computer Modeling Options Hydrology using SB County manual •Steady-state Qpeak based on storm event •Rational Method, short Tc’s dominate model •Larger areas Unit Hydrographs Hydraulic analysis using peak flow rates •Normal depth pipe sizes (WSPG) •Assume constant flow rate •No consideration of storm runoff volume Focused Drainage StudyGrand Terrace 21 Traditional Approach and Methodology Storm hydrograph Peak flow method 1 3 6 9 12 15 18 21 24 Focused Drainage StudyGrand Terrace 22 Focused Drainage StudyGrand Terrace 23 XPStorm Q100 Ultimate Conditions Focused Drainage StudyGrand Terrace 24 XPStorm Q100 Existing Conditions Advance Software to Integrate Hydrology and Hydraulics •New computer models •GIS databases Account for Flood Volumes •Pipes and Open Channels (and streets) •Detention Basins •Water Quality facilities Understand Impacts of Phased Construction Numerous Options and Approaches Available Advanced Stormwater Master PlanningThe Preserve 25 Hydrodynamic Approach Two Main Options: 1.1-dimensional (storm drain system only) 2.Coupled 1- & 2-dimensional (SD & Surface) Both use volume & timing in hydraulic analysis Numerous software systems available Local and Federal acceptance Focused Drainage StudyGrand Terrace 26 Hydrodynamic Computer Modeling Options