NOTICE OF PROPOSED MODIFICATION TO
WATER POLLUTION CONTROL PERMIT FOR
THE CITY AND COUNTY OF HONOLULU
HONOLULU BOARD OF WATER SUPPLY
HALEIWA WELLS GAC WATER TREATMENT FACILITY
NPDES PERMIT NO. HI 0021950

The Hawaii Department of Health (DOH), Clean Water Branch (CWB) proposes to modify the National Pollutant Discharge Elimination System (NPDES) permit to:

CITY AND COUNTY OF HONOLULU
BOARD OF WATER SUPPLY (HBWS)

to discharge standby contactor refreshing water associated with the maintenance
of the Granular Activated Carbon (GAC) beds; dewatering and disinfection
water associated with the removal of spent GAC; defining backwashing, backwashing/stratification, and forward flushing water associated with the preparation of new GAC beds; water from routine backwashing of the GAC beds; and well certification discharges to receiving State waters, subject to special conditions.
The proposed modified permit for the existing discharge will still expire at midnight, April 30, 2031. This permit is being modified pursuant to Hawaii Administrative Rules (HAR), Sections 11-55-16 and Title 40 Code of Federal Regulations (40 CFR), Sections 122.62(a)(15) and 122.63(a). 40 CFR 122.62(a)(15) allows modification of NPDES permits to correct technical mistakes, such as errors in calculation, or mistaken interpretations of law made in determining permit conditions. 40 CFR 122.63(a) allows modification to correct typographical errors. Pursuant to 40 CFR 124.5(c)(2), only the conditions subject to modification are reopened for public comment. The proposed modifications include:
1. Correcting the Annual Average and Single Sample Maximum limitations in Table A. 2 for the Wet and Dry Seasons to 240.2 lbs/day (Wet Season) and 120.1 lbs/day (Dry Season);
2. Updating the pollutant parameter in Table A.3. from “Dichloropropanes” to the specific pollutant “1,2 – Dichloropropane”;
3. Section B.1.b – Correction “gametes for testing” with “test organisms”;
4. Section B.2.b and B.2.c – Updating Whole Effluent Toxicity (WET) testing methods to 96-hour static renewal; and
5. Correcting a typographical error by removing the empty automated list item “d.” under Part B.7.
Persons wishing to comment upon or object to the proposed modifications to the 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 Clean Water Branch 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 a disability and require aid in inspecting and/or commenting on the Public Notice Permit and related information, please contact Mr. Reef Migita, Supervisor of the Engineering Section, Clean Water Branch, 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 a 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 CWB believes, after considering all timely written comments at any Public Hearing that may be held, that no substantive changes to the conditions of the Public Notice Permit are necessary or warranted, then 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
(SA1531221 6/24/26)