NOTICE OF CLEAN WATER BRANCH RECOMMENDATIONS FOR
WATER POLLUTION CONTROL PERMIT FOR
HONOULIULI WASTEWATER TREATMENT PLANT
NPDES PERMIT NO. HI 0020877
DOCKET NO. HI 0020877
PUBLIC COMMENT PERIOD
January 20, 2026 – February 19, 2026
The Hawaii Department of Health (DOH), Clean Water Branch (CWB) tentatively recommends to the Director of Health (Director) to renew a National Pollutant Discharge Elimination System (NPDES) permit to regulate and impose water pollution control requirements on the discharge of secondary treated wastewater, to receiving State waters, subject to special conditions, to:
CITY AND COUNTY OF HONOLULU
DEPARTMENT OF ENVIRONMENTAL SERVICES
A permit for such discharge would expire five (5) years from the effective date of the permit. The facility is located at 91-1000 Geiger Road, Ewa Beach, HI 96706. The facility has a dry weather design flow capacity of 38 million gallons per day (MGD). From July 2023 through June 2024, the annual average influent flow was 27.5 MGD, and the highest daily maximum influent flow was 40.7 MGD. The facility provides secondary treatment of wastewater from domestic and industrial sources for a population of approximately 325,000 people in the western portion of the Mamala Bay Service District. The facility also receives septage at the facility headworks for treatment.
As of June 1, 2024, the upgraded facility provides full secondary treatment to 100 percent of the effluent. Primary treatment consists of three (3) mechanical bar screens, grit removal, four (4) pre-aeration tanks, and four (4) primary clarifiers. Under the secondary upgrade, the previous secondary treatment train biotowers, biotower pump station, and secondary clarifiers were decommissioned. The upgraded system uses an activated sludge process consisting of four (4) aeration basins, one (1) mixed liquor distribution box, and six (6) secondary clarifiers. After the secondary clarifiers, a portion of the effluent (return activated sludge) is recycled through a secondary process pump station to the aeration basins for additional treatment, while up to 13 MGD of secondary effluent is directed to an off-site tertiary treatment facility to produce R-1 reuse and reverse osmosis (RO) water. The off-site R-1 and RO treatment facility is managed by the Honolulu Board of Water Supply, and operations at the tertiary treatment facility are covered under a separate permit.
At the effluent junction box, the secondary-treated effluent mixes with R-1 excess water and RO brine prior to effluent screening through three (3) bar screens. The commingled effluent is discharged through the Barbers Point Ocean Outfall (Outfall Serial No. 001) to Mamala Bay in the Pacific Ocean at Latitude 21°16’47” N and Longitude 158°01’40” W. The Barbers Point Ocean Outfall extends approximately 10,525 feet from the shoreline to a water depth of approximately 200 feet below mean lower low water. The diffuser section of the outfall is 1,750 feet long and consists of three (3) sections that range from 48 inches to 78 inches in diameter. The diffuser has 146 ports that range in size from 3.41 inches to 3.74 inches in diameter and two (2) end ports with a 6-inch diameter.
Sludge processing at the facility consists of two (2) course screens, two (2) rotary drum thickeners, four (4) blend tanks, three (3) anaerobic digesters, and three (3) centrifuges for dewatering. Wastewater streams are routed back to the primary clarifiers through the return flow pump station. Solids are hauled to H-Power for waste to energy conversion and are only disposed of in a landfill when H-Power is not available. The facility also has a wet sludge receiving facility where it intakes sludge for processing trucked from Wahiawa and Paalakai.
The receiving water, Mamala Bay, is classified by the DOH as a Class A Wet Open Coastal Water under HAR Section 11-54-6(b)(2)(8). It is the objective of class A waters that their use for recreational purposes and aesthetic enjoyment be protected. Any other use shall be permitted as long as it is compatible with the protection and propagation of fish, shellfish, and wildlife, and with recreation in and on these waters.
Persons wishing to comment upon or object to the CWB recommendations with respect to an NPDES permit or to request a public hearing, should submit their comments or requests in writing no later than 30 calendar days after the date of this notice, either through E-mail at cleanwaterbranch@doh.hawaii.gov or by mail at P.O. Box 3378, Honolulu, Hawaii 96801-3378.
Copies of the public notice permit recommended by CWB and other information are available for public inspection, Monday through Friday (excluding holidays) from 7:45 a.m. until 4:15 p.m., at the DOH-CWB office located at 2827 Waimano Home Road, Room 225, Pearl City, Hawaii 96782. Copies may be bought. Electronic copies of the proposed public notice permit and other information are also available online at https://health.hawaii.gov/cwb/clean-water-branch-home-page/public-notices-and-updates/.
For more information or if you have special needs due to disability that will aid you in inspecting and/or commenting on the public notice permit and related information, please contact Mr. Reef Migita, Supervisor of the Engineering Section, CWB, at the above address or (808) 586-4309 (Voice) as soon as possible before the end of the comment period. For those who use a TTY/TDD, please call through Sprint Relay Hawaii, at 1 711 or 1-877-447-5991. If a request for assistance is made after the end of the comment period, the CWB will try to fulfill the request. However, fulfillment prior to final determination cannot be guaranteed. Requests submitted as early as possible are more likely to be fulfilled.
All written comments and requests received on time will be considered. If the Director determines that there is significant public interest, a public hearing may be held after at least 30 calendar days of public notice.
If the CWB believes, after considering all timely written comments and all written testimony from any public hearing that may be held, that no substantive changes to the conditions of the public notice permit are necessary or warranted, then the CWB may recommend to the Director that the NPDES permit be issued.
Please notify anyone you know who would be interested in this matter.
DARRYL LUM, P.E.
Clean Water Branch Chief
(SA1508714 1/20/26)
