Cleaning Up The Ala Wai Canal In Waikiki Is Complicated

Cleaning Up The Ala Wai Canal In Waikiki Is Complicated

 

 

http://www.civilbeat.com/articles/2013/05/21/19074-ala-wai-canal-oversight-is-as-murky-as-the-water/

 

Prior to the canal’s construction in the 1920s, extensive wetlands naturally cleansed the fresh water descending from streams in the Manoa, Palolo and Makiki valleys before it washed into the ocean off of Waikiki.

The canal destroyed this natural filtration system. And as urban growth exploded in the mid-20th century, the canal became a catch basin for all the pollution and trash from the the ridges and valleys that form the Ala Wai Watershed area.

[VIDEO] Part Two: Building The Ala Wai Included Design Flaw
 

Even before the canal was finished in 1928 engineers realized the design was seriously flawed. The eastern outlet was never built because they didn't want pollution being swept west past Waikiki Beach. The semi-closed system means the canal doesn’t regularly flush, so contaminants build up in the sediment and the water.

In 1929, Oahu had a population of about 200,000. Today, it’s nearly 1 million. Tens of thousands of cars and trucks travel through the Ala Wai watershed area daily, leaving behind heavy metals and chemicals that are washed into storm drains and into the canal when it rains.

Rain also flushes pesticides, pathogens, dead animals, debris and sewage into storm drains and streams leading into the canal. While the city is primarily responsible for keeping the streams clean, the situation is complicated by hundreds of property owners who own parts of the streams.

In 1998, the task force estimated that 1,500 truckloads of sediment a year were being washed into the canal — a rate that would turn the canal into a mass of muck in about 50 years if not dredged, the panel predicted.

Cleaning that contaminated sediment out the canal is an expensive proposition. So far, cleanup has been largely through dredging, with tons of contaminated sediments dumped offshore.

Still, the canal has only been partially dredged three times in its history — in 1967, 1978 and 2002.

The 1998 task force said it needed to be dredged every 10 years — a cost the group estimated to be $10 million each time.

But there are no current plans to dredge the canal again, according to Carty Chang, chief engineer at Hawaii’s Department of Land and Natural Resources, which owns the canal and manages it.

Chang said that the department is waiting to see if dredging is part of a U.S. Army Corps of Engineers proposal that is expected to recommend ways to redesign the canal to prevent flooding.