Rain Gardens For Windward Mall

Over the course of the last month, HOK and contractors have been busy moving dirt, laying pipe, building water level control structures, grading and planting native plants at Windward Mall to construct three large bio-retention cells, or gigantic rain gardens!  The projects are located in three areas around the mall, near Sports Authority adjacent to the Kea'ahala Stream, behind the movie theater and mauka of the mall across Alaloa Street.  

In total, the new bio-retention cells, totaling more than 11,000 square feet, will reduce runoff into the stream from these areas by as much as 90%.  They are designed to receive polluted runoff from the parking lot areas, pond the water, allow slow infiltration through soil and native plants, and then return clean water to the stream during larger storms.  
 
This project represents HOK's largest and most engineered Low-Impact Retrofit to date.  The bio-retention cells were designed and built with a several feet of different sized gravel, under-drain pipes, soils, overflow pipes and five species of native Hawaiian vegetation which will all aid in pollution reduction. 
 
Mahalo to Roth Ecological Design, Ecosolutions and Green Girl Land Development Solution, LLC for helping HOK with the design.  Thanks also to the 22 volunteers that planted over 1500 plants, and contributed 100 hours of volunteer service.

This project would not have been possible without the support of the land owner, Kamehameha Schools, Windward Mall management and funding from the U.S. Environmental Protection Agency and the State of Hawaii, Clean Water Breach:  Polluted Runoff Control. 
 
In the coming months, HOK will monitor the effectiveness of the project, offer volunteer maintenance days and showcase this work as ways to improve ocean health on both new construction and redevelopment projects. 
 
If you are interested in learning more about the project, need help with your design or have other questions, please contact HOK Executive Director Todd Cullison at [email protected] or call 277-5611.