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September 8, 2017

Public Notice for Water Quality Certification and/or Waste Discharge Requirements (Dredge/Fill Projects)

PacifiCorp - Iron Gate Dam Spillway Dewatering Project 41.9335° N, 122.4379° W1 CW-839686, WDID 1A171664WNSI

Siskiyou County On August 30, 2017, the North Coast Regional Water Quality Control Board (Regional Water Board) received an application from PacifiCorp (applicant), requesting federal Clean Water Act, section 401, Water Quality Certification (certification) for activities related to the proposed Iron Gate Dam Spillway Dewatering Project (project) at the Iron Gate Dam located at river mile 190.5 on the Klamath River, in Siskiyou County.

Project Description
The purpose of this project is to conduct a spillway inspection at the Iron Gate Dam on the Klamath River. The inspection would require personnel to assess the spillway via scaffolding, and in order to accomplish this task, the spillway's terminal structure would need to be completely dewatered.

The applicant would dewater the terminal structure, which serves as an energy dissipation basin, of the Iron Gate Dam Spillway using three two-inch pumps. Each dewatering pump would be equipped with a fish screen on the suction side and a dewatering filter sock on the discharge hose. The water would be pumped to the apron of the spillway structure to allow water to enter the Klamath River downstream of the spillway. The volume of water to be removed from the spillway is estimated to be 295,330 gallons. The terminal structure of the spillway has two 12-inch drains situated eight feet from the bottom of the spillway. There is currently eight feet of standing water which will need to be removed. The total time for dewatering is approximately 22 hours. It is expected that there will be very little debris and sediment present due to a recent pulse flow event which would have removed a majority of the sediment from the terminal structure.

Project Timeline
The proposed work would take approximately two days and would occur between September 20th and 26th, 2017.

Receiving Waters The proposed project would discharge approximately 295,330 gallons of water into the Klamath River. The project location is within the Middle Klamath River Hydrologic Area 105.37.

1 WGS84 datum
WDID No. 1A171664WNSI - 2 - September 8, 2017

The proposed project would dewater an approximately 0.27-acre concrete energy dissipation basin at the base of the dam spillway. No impacts to jurisdictional waters are being proposed.

Other Agency Permits and Actions
The applicant has applied for authorization from the United States Army Corps of Engineers for a Clean Water Act, section 404 permit (Nationwide Permit No. 3).

The North Coast Regional Water Quality Control Board, as lead California Environmental Quality Act (CEQA) agency, has determined that the project qualifies for a Categorical Exemption, 15309 Inspections, and will file a Notice of Exemption with the State Clearinghouse concurrent with issuance of the 401 Water Quality Certification, pursuant to CEQA guidelines.

Public Comments
Regional Water Board staff are proposing to regulate this project pursuant to Section 401 of the Clean Water Act (33 USC 1341) and/or Porter-Cologne Water Quality Control Act authority. In addition, staff will consider all phone calls and comments submitted in writing and received within a 21-day comment period that begins on the first date of issuance of this notice and ends at 5:00 p.m. on the last day of the comment period. If you have any questions or comments, please contact staff member Jake Shannon at (707) 5762673 or Jacob.Shannon@waterboards.ca.gov  within 21 days of the posting of this notice.

The information contained in this public notice is only a summary of the applicant’s proposed activities. The Regional Water Board’s project file includes the application for certification and additional details of the proposed project, including maps and design drawings. Project documents and any comments received are on file and may be reviewed or copied at the Regional Water Board office, 5550 Skylane Boulevard, Suite A, Santa Rosa, California. Appointments are recommended for document review. Appointments can be made by calling (707) 576-2220.

170908_JJS_er_Iron Gate Dam Spillway Dewatering Project_PN


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