Ka'elepulu Stream Storm Water Retrofit

The Kailua Watershed and Ka'elepulu Stream are a high priority stream on the EPA 2004 303 (d) list of impaired water bodies.  They are listed as having high levels of Total Phosphorus and nutrients and turbidity.    

The Kailua watershed and Ka`elepulu sub-watershed are heavily developed with residential homes and other urban development.  In Ka'elepulu sub-basin, 50% of the watershed is in high or low intensity development with 88% of the landscape within 100 m of the stream in high/low intensity development.

The storm water retrofit project will improve 24,000 sq. ft. of an existing parking lot owned by City and County of Honolulu Parks Department adjacent to Ka'elepulu Stream in Kailua. The project includes the improvement of 361 feet of riparian habitat currently used as a parking lot. The project will re-grade the parking area to allow storm water to flow to a bio-swale, vegetated with native plant species and integrate of a vehicle setback from the stream of approximately 12-15 ft. Additionally, interpretive signage designed by local elementary school students with be installed to further convey the messages of watershed protection.

The expected outcomes of this project include:
• Decreased urban run-off entering Ka'elepulu Stream
• Increased community education and awareness of watershed issues

Partners for this project include the City and County of Honolulu Parks Department, local residents, businesses and schools.

Water Quality Monitoring

Currently, the City and County of Honolulu mechanically breach the sandbar on a monthly schedule.  This is done to help reduce the risk of flooding in the event of heavy rains.  Based on past monitoring, it is suspected the near shore environment of Kailua Bay is exceeding state and federal standards for bacteria.  When the stream mouth of Ka'elepulu Stream is open, recreational standards [water quality standards] are exceeded in Kailua Bay and therefore Ka'elepulu Stream impacts the water quality of Kailua Bay (Roll and Fujioka 1993). 

Additionally, when the mouth of Ka'elepulu Stream is closed, samples taken in Kailua Bay were always below the State and Federal Water Quality limits.  When Ka'elepulu Stream was open it exceeded the State standard 80 percent of the time and the Federal standard 60 percent of the time (Babcock 2005)

This monitoring activity is designed to obtain reference levels for water quality parameters in the Ka'elepulu Stream and near shore environment adjacent to the stream mouth and determine if bacteria levels are exceeding state and federal limits.  Additionally, HOK is trying to determine the best time to breach the sandbar.