Waters off Hilo Bay may turn red today

By Christie Wilson
Advertiser Neighbor Island Editor

Boaters and people in aircraft may notice a slight reddish coloration of the ocean off Hilo Bay today as county consultants use a nontoxic dye to study the wastewater outfall from the Hilo Wastewater Treatment Plant.

The study is required as part of the state Department of Health's National Pollutant Discharge Elimination System permit renewal process.

Five gallons of red tracer dye will be mixed with 2 million to 3 million gallons of effluent and released over a 15-hour period, said Nelson Ho, deputy director of the county Department of Environmental Management. The treated wastewater will be released into the ocean through an outfall pipe that ends about 3,000 feet offshore at a depth of 50 feet, outside the breakwater.

The dye is approved by the U.S. Environmental Protection Agency for use in the study of drinking-water systems and is not harmful to aquatic life, Ho said. It will be most visible at the point of discharge. As the effluent is diluted by the ocean, the discoloration will dissipate.

Brown and Caldwell, a Honolulu environmental engineering firm, is conducting the study for the Department of Environmental Management. A team of scientists will be on a boat over the release site to measure the dye concentration.

Ho said today was picked for the field study because there will be a relatively large variance between high tide and low tide. Tide and current activity might bring the dye closer to shore, which is one of the issues the study wants to investigate.

For information, contact the Department of Environmental Management at (808) 961-8083.

Reach Christie Wilson at cwilson@honoluluadvertiser.com or (808) 244-4880.