NOTICE OF PROPOSED WATER POLLUTION CONTROL PERMIT
FOR SAND ISLAND WASTEWATER TREATMENT PLANT
NPDES PERMIT NO. HI 0020117
DOCKET NO. HI 0020117
February 8, 2021
The State Department of Health (DOH) tentatively proposes, subject to public comments, to issue a renewal National Pollutant Discharge Elimination System (NPDES) permit to discharge primary-treated wastewater from the Sand Island Wastewater Treatment Plant to receiving State waters, subject to conditions, limitations, and requirements in the NPDES permit and in accordance with State water pollution control law contained in Hawaii Administrative Rules Chapters 11-54 (Water Quality Standards) and 11-55 (Water Pollution Control) to:
CITY AND COUNTY OF HONOLULU
DEPARTMENT OF ENVIRONMENTAL SERVICES
(Permittee)
The proposed permit for the discharge will expire five (5) years from its effective date and will only authorize those discharges explicitly identified in the permit. The Permittee will be responsible for obtaining all other County, State, and/or Federal permits, licenses, and/or approvals as required by law.
The City and County of Honolulu owns and operates the Sand Island Wastewater Treatment Plant (facility), located at 1350 Sand Island Parkway, Honolulu, Island of Oahu, Hawaii, 96819. The facility has an average design flow of 90 million gallons per day (MGD) and provides primary treatment of wastewater for a population of approximately 460,000 people in the Sand Island Basin. Influent wastewater enters the facility and is distributed to a minimum of two (2) of six (6) available aerated screening channels, where screening and flow measurement using Parshall flumes occur. From there, wastewater is directed to the clarifier’s influent channels for primary treatment.
The clarifier’s influent channels distribute wastewater to eight 150-foot diameter clarifiers. At normal flow, three clarifiers are in use. Primary treated wastewater is then piped to effluent screens and then to disinfection. The facility contains five (5) available dual bank medium pressure ultraviolet (UV) disinfection channels. After disinfection, treated effluent is discharged to Mamala Bay, Pacific Ocean, through Outfall Serial No. 001, at Latitude 21°17’01″N and Longitude 157°54’24″W.
Outfall Serial No. 001 is an 84-inch diameter deep ocean outfall that discharges treated effluent through a diffuser that starts approximately 9,100 feet offshore and 230 feet below the surface of the water. The diffuser is approximately 3,400 feet long with 282 side ports that range in size from three (3) inches to 3.53 inches in diameter and two 7-inch diameter ports in the end gate.
Sludge processing at the facility consists of gravity thickeners, wet sludge storage tanks, and two digesters. Biosolids are processed onsite by an independent contractor.
The receiving water, Mamala Bay, Pacific Ocean, is classified as “Class A Wet Open Coastal Waters” under HAR Section11-54-06(b)(2)(B) and 11-54-3(c) at that location. Protected beneficial uses include recreational purposes, aesthetic enjoyment, and any other uses compatible with the protection and propagation of fish, shellfish, and wildlife, and with recreation in and on these waters.
Persons wishing to comment on 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 to
Department of Health, Clean Water Branch
P.O. BOX 3378
Honolulu, HI 96801-3378.
Copies of the proposed public notice permit and other information are available for public inspection at the DOH Clean Water Branch office located at
2827 Waimano Home Road, Room 225
Pearl City, HI 96782
Monday through Friday (excluding holidays) from 7:45 a.m. until 4:15 p.m. The public notice permit and fact sheet are also available on the internet at: https://health.hawaii.gov/cwb/clean-water-branch-home-page/public-notices-and-updates/ For more information, or if you require assistance inspecting and/or commenting on the public notice permit and related information, please contact Mr. Darryl Lum, Supervisor of the Engineering Section, Clean Water Branch, at the above address or (808) 586-4309 (Voice) at least 7 calendar days before the comment deadline. For those who use a TTY/TDD, please call through Verizon Hawaii Telephone Relay Service, at 1-711 or 1-877-447-5990.
All written comments and requests received within the submission deadline will be considered. Any request for a hearing must indicate the interest of the party submitting the request and the reason(s) why a hearing is warranted. 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 DOH will issue the NPDES permit and this action will be final.
Please notify anyone you know who may be interested in this matter.
ELIZABETH A. CHAR, M.D.
Director of Health
(SA1314276 2/8/21)
