Once again, it has taken an observant reader's e-mail to prompt a long overdue Water Ways column.

"I have read your comments about pollution in the Ala Wai Canal, and what is being done to correct it," the message read. "But, I haven't seen anything lately about when, if ever, the state intends to dredge it."

The reader had a good point. In looking over past columns, it's been almost three years since I wrote about the dredging issue, and that was in reference to a dredging appropriations bill that was going through the state legislature.

So we can all have the same understanding about the Ala Wai's present condition, let me offer a bit of the canal's history, as I understand it.

The canal was constructed over a period of seven years, after the First World War, during the time they called the "Roaring Twenties."

It's functions were twofold, to channel the runoff from the surrounding watershed, which included the Manoa, Palolo and Makiki streams, into the ocean, and to provide fill material for the developers of Waikiki.

It didn't take long before the new canal became an attractive recreational waterway for boaters, paddlers and fishermen. In fact, there were boat slips lining its banks for many years.

But as the canal continued to funnel the runoff from the Koolaus, its bottom slowly accumulated a portion of the alluvial sediment it was carrying to the sea. So much sediment, in fact, that in 1966 the state finally had to dredge the Ala Wai to restore its water-carrying capacity and its recreational potential.

Sometime later, a University of Hawaii study recommended additional maintenance dredgings every decade, and nearly on time, the canal was dredged again in 1978.

Oddly though, and perhaps, for reasons only our politicians and bureaucrats might explain, subsequent dredgings have not occurred on schedule. So now, the Ala Wai's water is inches deep in many places and nowhere near its original 10- to 25-foot depth.

One of the reasons there has been a dredging delay over the past four years is because of the concern about the nature of the sediment to be dredged and, apparently, the lack of sufficient funding to conduct appropriate analysis of the sediment.

Such testing was needed to satisfy federal Environmental Protection Agency (EPA) disposal guidelines. That is, the state had to be sure the sediment was not so contaminated that it would present a hazard if it was dumped into the ocean, as had been done in the past.

Now, finally, the tests of the physical, chemical and biological composition of the sediment have been completed and, for the majority of the sediment, no significant potential for long term adverse impact to the marine environment was found.

With these test results, it appears that a final application for the Ala Wai canal's dredging will soon be filed (if not already filed) with the Army Corps of Engineers.

The public will then have about a month to comment on the project, followed by appropriate review and response from the Corps and the EPA.

Barring any unseen delays, it would appear that a permit to dredge could be issued by June 1 and the project might begin soon after that - more than two decades later than had been recommended by the UH study.