Public Comment Form

Commenting open: May 25, 2021 08:00AM AKT - June 25, 2021 11:59PM AKT.

Public Notice Comment Period for Draft Individual Permit AK0055913 Hilcorp Alaska LLC, Tyonek Platform Supplemental Development Drilling

A Draft Permit, is available for review. For inquiries or to request copies of documents, contact:

DEC Contact: Gerry Brown, PE

Alaska Department of Environmental Conservation
Division of Water - Wastewater Discharge Authorization Program
555 Cordova Street
Anchorage, AK 99501
(907) 269-4874

Draft Permit Public Notice Period:
Public Notice Start Date: May 25, 2021
Public Notice Expiration Date: June 25, 2021, 11:59 pm Alaska Daylight Time

Permit Number: AK0055913

Permit Name: Hilcorp Alaska LLC, Tyonek Platform Supplemental Development Drilling

Proposed Permit Coverage:
The Permit is a new individual permit for oil and gas drilling activity related wastewater discharges at the Tyonek Platform in the Cook Inlet. The drilling operations covered by this proposed permit are intended to increase gas production at the facility and is expected to be a one-time authorization for discharges associated with development drilling planned for the summer of 2021. The proposed permit would have a maximum of a 5-year term. 

Supplemental drilling operations would utilize the Spartan 151 Mobile Offshore Drilling Unit (MODU) or other similar MODU, which would be positioned over the existing Tyonek Platform. Drilling operations with the MODU necessitates authorization of the following five distinct wastewater discharges: Graywater; Blowout Preventer Fluid; Noncontact Cooling Water; Uncontaminated Ballast Water; and Excess Cement Slurry discharges. During supplemental development drilling industrial discharges will be permitted to occur from:

The discharge of Graywater includes the authorization of a 35-meter radii chronic mixing zone and an 18-meter radii acute mixing zones for total residual chlorine. Authorization of miscellaneous discharges of blowout preventer fluid, noncontact cooling water, uncontaminated ballast water, and excess cement slurry includes a 100-meter radii chronic mixing zone. Lastly, the discharge of excess cement slurry includes authorization of a short-term zone of deposit.

Tentative Determination:
DEC has tentatively determined to issue the wastewater discharge permit.

Public Comments:
Written comments on the draft permit must be submitted within 30-days of the issuance of this public notice. Comments can be submitted electronically via our public notice site at:

Alternatively, please direct written comments and requests to the attention of the permit writer at the address or email shown on page 1. All comments should include the name, address, and telephone number of the commenter and a concise statement of comment on the permit condition(s) and the relevant facts upon which the comment is based. Comments of either support or concern that are directed at specific, cited permit requirements are appreciated. Mailed comments and requests must be postmarked on or before the expiration date of the public notice.

DEC will consider all substantive comments when making the final decision. Those who provided timely comments during the public review will be notified of the final decision and be provided with a summary for the basis of the final decision. 

  June 25, 2021 at 11:59 p.m. Alaska Daylight Time

Administrative Record:
The APDES Draft Permit, Fact Sheet, permit application, and associated documents are available for public review at the DEC offices located in Anchorage, Fairbanks, Juneau, Wasilla, and Soldotna. Please contact the office of your choice to arrange for hard copies of the documents to be available for your review. 

555 Cordova Street 610 University Avenue  410 Willoughby Ave #303
Anchorage, AK 99501 Fairbanks, AK 99709  Juneau, AK 99811
907-269-6285  907-451-2100  907-465-5300

43335 Kalifornsky Beach Road 1700 E Bogard Road 
Suite #11 Building B, Suite #103
Soldotna, AK 99669 Wasilla, AK 99654
907-262-5210 907-376-1850

If you would like further information or to see any additional supporting technical documents, contact the permit writer at the address shown on page 1.

The permit documents can be accessed from the DEC Wastewater Discharge Authorization Program website at 

To receive email notifications about the APDES Program, including when permits are available to review, follow the link below to join the APDES email list.

Disability Reasonable Accommodation Notice
The State of Alaska, DEC complies with Title II of the Americans with Disabilities Act of 1990. If you are a person with a disability who may need a special accommodation in order to participate in this public process, please contact Garrett Odom at (907) 269-0291 or TDD Relay Service 1-800-770-8973/TTY or dial 711 within 30-days of publication of this notice to ensure that any necessary accommodations can be provided.


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