Department of Public Works West Maui Storm Drainage August 20, 2019 - - PowerPoint PPT Presentation
Department of Public Works West Maui Storm Drainage August 20, 2019 West Maui Community Plan Meeting Ready & Resilient Systems County of Maui West Maui Drainage Systems Underground drainlines within County right of way Sediment and
August 20, 2019 West Maui Community Plan Meeting Ready & Resilient Systems
Underground drainlines within County right of way Sediment and debris basins Flood control systems
Underground Drainage System in Lahaina Town 5 - DLNR Regulated Sediment Basins
Honokowai Kahana Nui Kaopala Napili 4-5 Napili 2-3
3 - Unregulated Sediment Basins
Honokeana S-Turn Mahinahina
Kahoma Stream Flood Control Lahaina Watershed Flood Control (Lahainaluna to Launiupoko)
Existing corrugated metal pipes are failing What’s next?
Drainage system inventory of West Maui recently completed Drainline condition assessment recently contracted to consultant Prioritize drainage systems needing repair Secure funding
Reduces sediment entering near shore waters Highways Division’s maintenance:
Remove sediment build up and debris Inspect during and after a large storm event and submit reports to DLNR for regulated basins
Drone surveys used to determine the extent of sediment removal needed
No access prevents Highways Division from clearing culverts/channels
Property owners need to keep drainage easements clear; no trees, structures, fences, etc.
No dumping of green waste in drainageways please! Ponding problems due to lack of drainage systems
Need evaluation of problem areas Seek funding
Flooding
Completion of Lahaina Watershed Phases 3B, 4, & 5 is necessary Sea level rise causing more sand plug build up at drain outlets Sand plugs lowered by Highways in anticipation of large storm events
Continuous maintenance required to keep debris basins clear and functional
Next phase to construct – Phase 3B at Kauaula Stream 3B plans need revisions to address continuous stream flow Environmental studies to be updated NRCS to seek construction funds
Comply with County’s Rules:
Title MC-15, Chapter 4 - Storm Drainage Facilities Title MC-15, Chapter 111 - Storm Water Treatment BMPs
Additional runoff generated must be retained onsite LID (Low Impact Development) design is encouraged Use Best Management Practices for sediment & erosion control
Objectives and Policies: Ensure that drainage systems comply with the County’s drainage rules. Incorporate post-development BMPs into project planning. Pursue funding sources to fund drainage infrastructure. Encourage the use of low impact development (LID) techniques for all new developments, roadway projects, and Capital Improvement Projects. Ensure that new developments will not result in adverse flooding conditions for downstream properties by requiring onsite retention facilities for stormwater run-off generated by the development.
Implementing Actions: Update the Lahaina Town Drainage Master Plan. Complete the Lahaina Watershed Flood Control project. Establish a comprehensive stormwater management plan that emphasizes the use of natural drainage systems where possible. Complete an inventory of drainage facilities in West Maui for use in developing long-term plans for addressing stormwater issues. Encourage the use of underground utilities and coordinate utility placement with road improvements.
Rowena Dagdag-Andaya Director Department of Public Works