Storm Water Management Program

Storm water runoff occurs when precipitation flows over the land and impervious areas such as paved streets and parking lots. Storm drainage systems are designed to decrease flooding by carrying storm water runoff through drains and underground pipes to nearby streams and eventually the ocean. Storm drainage systems generally do not provide treatment of storm water runoff so it is important to keep pollutants out of our storm water before reaching surface waters.

The County of Maui works in many ways to protect storm water and receiving waters from pollutants that could negatively impact receiving water quality. The County’s goal is to work with community individuals, businesses, large landowners, and State and Federal agencies to foster joint responsibility and positive action to protect our precious surface water resources. 

The County’s MS4 NPDES Permit

The 2010 US Census identified Kahului-Pā‘ia as an urbanized area (UA) based on residential population. The boundary of the UA generally includes all of Kahului and Wailuku extending south to Waikapū and from Wai‘ehu to Pā‘ia along the windward coast. The UA designation triggers a requirement for a municipality to obtain a National Pollutant Discharge Elimination System (NPDES) permit for discharge of storm water from their Small Municipal Separate Storm Sewer System (MS4). The County received their Notice of General Permit Coverage (NGPC), File No. HI 14KE360, for discharges from the MS4 in the UA from the State Department of Health (DOH) in April 2014. This NGPC expired at midnight, December 5, 2016 because of the expiration of DOH’s NPDES General Permit for Small MS4s (Appendix K). The County submitted a Notice of Intent (NOI) to DOH for the Renewal of the NGPC. DOH granted an Administrative Extension to the County’s current NGPC until DOH issues a new General Permit.

National Pollutant Discharge Elimination System (NPDES) Permit

Storm Water Management Program (SWMP) Plan for the Kahului-Pā‘ia Urbanized Area

The County submitted their Storm Water Management Program (SWMP) Plan in August 2014 to the DOH. The SWMP Plan was revised in December 2015 to reflect information gained during initial implementation of the program. The purpose of the SWMP is to implement programs and practices to control polluted storm water runoff from the County’s regulated MS4.
SWMP Components
  1. Introduction
  2. Public Education and Outreach
  3. Public Involvement / Participation
  4. Illicit Discharge Detection and Elimination
  5. Construction Site Runoff Control
  6. Post-Construction Runoff Control
  7. Pollution Prevention/Good Housekeeping
  8. Tables
  9. Figures
  10. Attachments A-F

What You Can Do

We can all do our part to protect storm water and our valuable surface water resources by evaluating our own everyday activities and taking precautions to prevent pollution from entering storm drains. Click through the following documents for information and tips to keep our island beautiful.
Storm Water


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Resources for Teachers and Parents

We all depend on water every day and yet many of us don’t know where it comes from or the possible routes storm water can take from our homes to the ocean. Knowledge of storm water can increase our appreciation of the watershed we live in and the impact we have on it. Teachers and parents can use these fun lesson guides for their students and children to help them broaden their knowledge of storm water and the simple acts we can take to prevent pollution.

SWMP Complaint Reporting Form

Storm Water Concern Reporting

Illicit discharge is any disposal, either intentional or unintentional, of material(s) or waste(s) that can pollute storm water. You can report illicit discharges or spills to storm water or surface waters in any of the following ways:
  1. Contact the Department of Public Works Highways Division (808) 270-7869; 
  2. Via Email  or;
  3. If you see illegal dumping or large spills that could contaminate surface waters or threaten public health, dial 911.
** Please provide as much information as possible, including location, cross streets, type of discharge, water body threatened, nature of the release, and a photo if available.