NOTICE OF PROPOSED WATER POLLUTION CONTROL PERMIT
FOR THE HONOULIULI WASTEWATER TREATMENT PLANT
EWA BEACH, ISLAND OF OAHU
NPDES PERMIT NO. HI 0020877
DOCKET NO. HI 0020877
July 9, 2020
The State Department of Health (DOH) tentatively proposes to issue a renewal National Pollutant Discharge Elimination System (NPDES) permit to discharge secondary-treated wastewater from the Honouliuli Wastewater Treatment Plant, to receiving State waters, subject to special conditions to:
CITY AND COUNTY OF HONOLULU
DEPARTMENT OF ENVIRONMENTAL SERVICES
(Permittee)
The proposed NPDES permit for the existing discharge will expire five (5) years after the effective date of the permit.
The Permittee owns and operates the facility, located in Ewa Beach, Hawaii, on the Island of Oahu. The facility has a design dry weather flow capacity of 38 million gallons per day (MGD) and provides primary and some secondary treatment of wastewater for a population of approximately 335,000 in the western portion of the Mamala Bay Service District. All incoming influent receives primary treatment consisting of preliminary influent screening, grit removal, pre-aeration, and primary clarification. After primary treatment, flow is separated into two streams. One stream is sent straight to effluent screens and does not receive additional treatment; the second stream of up to 13 MGD of primary treated wastewater is routed through two adjustable V-notch weir gates to secondary treatment. Secondary treatment includes biotowers, solids contact, and secondary clarification. Some of the secondary-treated effluent from the biotowers is recycled to the biotower pumping station while the remaining effluent flows to the solids contactor. After secondary clarification, the secondary-treated effluent flows through two Parshall flumes. Up to 10 MGD of secondary-treated effluent may then be directed to the tertiary treatment facility to produce R1 reuse water and reverse osmosis reuse water, while the remaining 3 MGD of secondary-treated wastewater is routed to the effluent screens. The secondary-treated effluent mixes with the primary effluent, tertiary R1 effluent, and brine prior to effluent screening. The combined effluent then flows through fine screens and finally to the Barbers Point Ocean Outfall (Outfall Serial No. 001) in Mamala Bay, Pacific Ocean, at Latitude 21°16’47” N and Longitude 158°01’40” W. The tertiary level treatment facility is managed by the Honolulu Board of Water Supply. Operations at the tertiary facility are covered by a separate permit.
Outfall Serial No. 001 is located at a water depth of about 200 feet below mean lower low water and about 10,525 feet from the shoreline. The diffuser section of the outfall is 1,750 feet long and consists of three sections that range from 48 inches to 78 inches in diameter. The diffuser section of the outfall has 146 diffuser ports that range in size from 3.41 inches to 3.74 inches in diameter and two end ports with a 6 inch diameter.
Sludge processing at the facility consists of digestion and thickening by gravity thickeners, and dewatering by centrifuge. Solids are hauled to H-Power for waste-to-energy conversion and is only disposed of in a landfill when H-Power is not available.
Persons wishing to comment upon or object to the proposed 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 2827 Waimano Home Road, Room 225, Pearl City, Hawaii 96782.
Copies of the proposed public notice permit 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 Clean Water Branch (CWB) office located at the 2827 Waimano Home Road, Room 225, Pearl City, Hawaii 96782. Copies may be bought. The public notice permit and fact sheet are also available on the internet at: http://health.hawaii.gov/cwb/site-map/home/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. Darryl Lum, Supervisor of the Engineering Section, CWB, at the above address or (808) 586 4309 (Voice) at least seven (7) calendar days before the comment deadline. For those who use a TTY/TDD, please call through Sprint Relay Hawaii, at 1-711 or 1-877-447-5991.
All written comments and requests received on time will be considered. If DOH determines that there is significant public interest, a public hearing may be held after at least 30 calendar days of public notice.
If DOH’s position is substantially unchanged after considering all timely written comments and all oral comments at any public hearing that may be held, then the DOH will issue the NPDES permit and this action will be final.
Please notify anyone you know who would be interested in this matter.
BRUCE S. ANDERSON, Ph.D.
Director of Health
(SA1285391 7/9/20)
