issues & concerns
The USACE solutions are built around the concept of detaining. They treat the Ala Wai Canal as a reservoir. The problem is that the Ala Wai Canal has no slope and with no slope, there is velocity of flow and with no velocity of flow there is very little water exiting out to the ocean. If there is a rising tide or storm surge, the water from the ocean could actually be entering the Ala Wai Canal instead of exiting even as storm waters rush down to the Ala Wai Canal. Sea level rise due to climate change will further reduce the storage capacity of the Ala Wai Canal.
Did Not Follow NEPA & HEPA
We believe that the United State Army Corps of Engineers (USACE) did not adequately engage the public and residents most affected by the Ala Wai Canal Project as required under National Environmental Policy Act (NEPA) and the Hawaii Environmental Policy Act (HEPA).
We believe that communities and neighborhoods were left out of the process and were not given a chance to provide their comments, express their concerns, and provide alternative solutions. We believe that the process was not transparent and did not follow proper protocols which required these steps to be addressed during the Draft EIS stage and not after Finalization of the EIS and after Congressional Funding.
We believe that the 100-year flood modeling and associated property damage figures are unrealistic and flawed. These flood models are based on historical events and represent the probability of occurrence. The same methodology, data sets, and computer programs generated the 5-year, 10-year, and 50-year flood models. The 5-year flood model (shown on the EIS) has a probability of occurring once every 5 years, yet, the damage predicted every 5 years has never happened in Hawaii’s history.
We believe a large part of the inaccuracy of the flood modeling is due to the data collection procedures. There are 13 rainfall gauges that are owned and operated by 4 different entities, no mention of uniform operating procedures, no mention of certification of equipment, quality control, or maintenance to ensure accurate and reliable data. Six rainfall gauges are read daily. One rainfall gauge is outside the watershed. Locations selected are out of convenience (like a fire station or water pumping station) rather than optimal data locations.
One station had data missing for a 12 year period. One station the data seemed incorrect for 4 years time and was tossed out. The Thiessen polygon method does not account for orthographic rainfall effect in the mountain.
Where did these money figures come from?
We question how the Draft EIS in 2015 with a project cost of about $187 million and a property damage figure of $318 million can change so dramatically without public oversight to a project cost of about $345 million and a property damage figure of $1.14 billion in one or two years time.
We question how the environmental impact disclosures for many of the upstream detention basins as shown in the Draft EIS were significantly expanded without public oversight by 200-400% in length of stream destroyed and number of properties required as shown in the Final EIS. (draft vs final)
We question the use of the 2004 Storm which caused approximately $85 million damage to the University of Hawaii as a reason for this project. The Hydrology and Hydraulics Study Flood of October 30, 2004 shows that the cause was due to a lack of proper maintenance, that the Woodlawn Bridge was half filled with sediment from the original construction design and the other half of the opening got clogged with debris causing the topping. A separate project to correct the sedimentation build-up is nearly completed.
What would happen if a basin overtopped?
We are against the USACE flood mitigation measures which include several detention basins and building an average 4-foot solid reinforced concrete wall to mitigate the 100-year flood.
We are generally against the use of high earth filled detention basins with concrete conduits that stretch over 150 feet in length and are covered with earth and rock. These conduits are just another form of concrete channels except buried. The height of the dam results in water pressures that require hundreds of feet of addition ripraps to dissipate velocity of the exiting storm waters. Many of these detention basins require the dredging or ripping out of hundreds of feet of natural stream behind them to create volume capacity.
While these detention basins are designed to hold the 100-year storm with safety factors in place and have designed spillways in the event they are topped. They can be breached if a storm larger than what it was designed for hits and even a smaller storm can breach the dam if debris plugs the drainage inlet. This means that vegetation possibly for miles upstream would have to be maintained to prevent plugging. There is always the possibility of these dams to catastrophically fail and jeopardizing the safety of the residents downstream.