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New Requirements for Storm Water Management

Building or renovating a home in Honolulu? You’ll need to add a Residential Storm Water Management Plan to your building permit application. As of August 18, 2020, the City and County of Honolulu officially enacted the 2012 International Building & Residential Codes, which require property owners to provide plans detailing how they intend to manage future influxes of storm water. 

The new requirements are intended to protect Honolulu’s water quality and the general health of the public. In the past, poor storm water management has polluted the general water supply and caused extensive damage to homes and other structures on the islands. Officially adopting these best management procedures is Honolulu’s attempt to proactively address water management issues for all future building projects.

Here’s the main things to consider as you and your construction team create your storm water plan:

  • The primary goal of all storm water management is to prevent runoff water from congregating and potentially flooding a home or adjacent properties. Reducing the amount of impervious surface on a property helps prevent this water build-up.
  • According to Section R107.5 and  R107.5.1 of the 2012 International Building Code, the amount of impervious surface found on a given property “shall not exceed 75 percent of the total zoning lot area for construction of a one-family or two-family detached dwelling or duplex.” These requirements apply to both new builds and renovations of existing structures
  • Impervious surfaces include concrete, asphalt, and any other continuous watertight pavement or covering. Rooftops, walkways, patios, driveways, parking lots, and storage structures also constitute an impervious surface. 
  • Additionally, any additions or alterations to an existing property that increases the overall floor area of a structure are no longer considered  “Minor Developments.” An Erosion and Sediment Control Plan (ESCP) and accompanying $250 fee is now required. Multiple or two family detached homes on lots exceeding 10,000 square feet will each require their own ESCP and individual fee.
  • While the checklist provided by the City and County of Honolulu addresses all the individual requirements for storm water management, general best practices include the use of landscaping, irrigation, and draining systems designed to divert water away from the home quickly and efficiently. 
  • Property owners are also expected to address how they will manage the use of pesticides and other chemicals on their property in order to prevent excess contamination of the soil. Plans for reducing the overall percentage of  impervious surfaces and replacing them with porous ground cover are also required.

Building a home that’s both beautiful and environmentally responsible is a big undertaking. Make sure you have the best team possible when it comes to design, permitting, and construction. Contact us today and let us help you find the right  professionals for your new build or remodel. We’ll help you build a home that’s ready for anything— from taking the world of home design by storm to keeping the storm water at bay.