Engineering Report
This is an analysis of the potential methods and locations for water transfer from Kawainui Marsh to Kawainui Stream in the Kaelepulu system. Because the marsh water surface is a few feet higher than Kawainui Stream no pumps are required to obtain flow. The final draft design is for a 12-18″ pipe buried beneath the ground shunting water around the south end of the levee adjacent to Kailua Road and emptying into the ITT wetland before flowing to Kawainui Stream and the Kaelepulu system.
Flow Restoration Experiment Report
The entire flow from Kawainui Marsh (~9 cfs) used to flow through the Kawainui Stream. In this experiment, about 2 cfs flow was restored for a period of three months using siphons to pass water over the flood levee from Kawainui Marsh to Kawainui Stream and the Kaelepulu system. Water levels and physical water quality parameters were monitored to determine the impact of this partial flow restoration. Results indicated that the added flow was sufficient to keep the water level in the Kaelepulu system from falling due to evaporation and resulted in a rise of about 1/8th inch per day. Overall impacts to the Kaelepulu system were positive and no decrease in water surface elevation in Kawainui Marsh was detectable.
Preliminary Environmental Assessment Report
A partial environmental assessment was conducted to clarify both the potential impacts to the environment and to the broader community. Environmental impacts of partial flow restoration to the Kaelepulu system are seen to be positive. A primary concern of the community, and to USACE regulators, was that the project could increase the threat of flooding. The EA shows that the maximum quantity of water possible to flow through the pipeline is far far less than the volume that would be necessary to have any significant impact upon flooding. Concerns of the USACE as to the potential impact upon the structure of the existing flood control levee were addressed by designing the pipe to be laid around the south side of the marsh avoiding the levee structure altogether. For the project to move forward a complete EA would need to be written covering archaeological and social impacts not covered in this report.