Ka’anapali Golf Course Denitrifying Curtain, Maui, Hawai’i

Project Summary

In Ka’anapali, West Maui, there’s a nature-based solution to a perennial problem. The Ka’anapali Golf Course is a famous recreational site, situated near a popular swimming area; the golf course and the swimming waters are closely connected in ecological space. To meet golfers’ expectations, fertilizers and pesticides are used on the course. Though the golf course management is very careful to ensure proper and sustainable use of production inputs, in some situations, these production inputs have the potential to runoff into nearby waters. A solution to catch, filter, and clean the runoff water was needed! The Ka’anapali Golf Course, under the direction and generous support of superintendent Craig Trenholme, partnered with Ridge to Reefs and West Maui R2R to build an effective nature-based solution to proactively protect coastal and groundwater resources in the area.

Problem
Growing the lush, green, pest-free grass that golfers expect relies on the use of fertilizers and pesticides. Though the golf course management are experts in the sustainable use and application of these production inputs, there was a strong desire to take proactive steps to mitigate any potential impacts to the nearby environment. This project seeks to address and treat excess nutrients that may be present in surface and shallow groundwater originating from the golf course.
Solution
To clean up pollutants and filters out excess nutrients, we built a denitrifying curtain. This is a filtering structure made out of natural materials that catches runoff water and cleans out pollutants before allowing it to continue flowing downstream to join the adjacent waterway.

Implementation
To build the denitrifying curtain, the golf course loaned us the use of their machinery and operators to dig installation sites. The structure was engineered to be built with local coconut coir diverted from landfill and locally produced woodchips. By using locally sourced materials, we further reduced the ecological footprint of construction.
Outcomes
These natural, locally produced biochar and woodchip components upcycled into the denitrifying curtain boost the efficiency and efficacy of the filtration engineering. This structure works efficiently and with longevity to clean runoff water. This lasting impact protects the environment and human health.

Funders and Partners Ka’anapali Golf Course, superintendent Craig Trenholme; West Maui R2R Watershed Coordinator, Tova Callender