PUBLIC NOTICE NO: PPL-C 2019-0004
Corps of Engineers Civil Works Action
Section 408 Permission for:
MILL CREEK CHANNEL DIRECTIONAL DRILLING
Mill Creek Project
Walla Walla, Washington
PUBLIC NOTICE DATE: March 22, 2019
COMMENTS DUE DATE: April 22, 2019
Interested parties are hereby notified that the Walla Walla District of the U.S. Army Corps of Engineers (Corps) is soliciting comments from the public regarding the Corps’ proposal to grant permission pursuant to 33 United States Code Section 408 (Section 408) for alteration, occupation, or use of a Corps-constructed harbor or river improvement (public work). Section 408 authorizes the Secretary of the Army to grant permission for the alteration, occupation, or use of a public work if the Secretary determines the activity will not be injurious to the public interest and will not impair the usefulness of the project.
LOCATION: The subject alteration is a proposed directional drilling under the flood risk management channel and levees of the Mill Creek Flood Control Project in Walla Walla, Washington. The Corps constructed the channel and the associated levees along both banks of the creek in the 1940’s to pass high flows and reduce the risk of flooding to the City of Walla Walla and surrounding communities. The proposed directional drilling would be located on the west side of Ninth Avenue/State Highway 125 within the city/state right-of-way and adjacent to the bridge over the Mill Creek channel (Figure 1).
Figure 1 – Aerial photo showing location of proposed directional drilling under Mill Creek channel and levees
PROJECT DESCRIPTION: The Corps proposes to grant Section 408 permission to the Cascade Natural Gas Corporation (CNG Corp) to directionally drill perpendicular to and under the Mill Creek flood risk management channel and levees to install a new 8-inch diameter natural gas pipeline segment. This new pipeline segment would be made of polyethylene and would replace the steel pipeline segment currently mounted on the underside of the Ninth Avenue Bridge. The existing pipeline segment has corrosion on it and cannot be repaired because of the way it was installed.
CNG Corp proposes to drill a small “tunnel” starting about 250 feet north of the channel, angling downward so the tunnel is at least ten feet below the channel, then angling upward and daylighting about 250 feet south of the channel (Figure 2). CNG Corp would excavate holes, or bore pits, up to 7 feet wide and 27 feet long at either end of the “tunnel” to facilitate the drilling. Once the drilling is complete, the new pipe would be pulled through. CNG Corps would cap and cut the existing pipeline and connect the new segment to the existing gas line. CNG Corp would then excavate a 4-four by 4-four bell hole in each of the Ninth Avenue Bridge abutments to facilitate cutting and removing the old pipeline from the bridge. Finally, CNG Corp would backfill the excavated areas and restore the work site to its original condition.
Figure 2 – Cross-section sketch showing path of tunnel under Mill Creek channel
CNG Corp plans to perform the work in the summer of 2019, starting in early August. CNG Corp estimates it would take about three weeks to complete the project.
COMMENTS: Interested parties are invited to provide their comments on the proposed Corps action of granting Section 408 permission to CNG Corp for their proposed directional drilling under the Mill Creek channel and levees. The Corps is particularly interested in your opinion on issues and environmental effects the Corps should consider when evaluating the CNG Corp request.
COMMENT PERIOD: Comments must be submitted or postmarked no later than April 22, 2019. You may submit comments electronically online at https://www.nww.usace.army.mil/EnvironmentalComplianceComment/ or via e-mail to NEPANWW@usace.army.mil and inserting “Mill Creek Directional Bore 408” in the subject line.
You may also mail comments to:
U.S. Army Corps of Engineers, Walla Walla District
Mill Creek Directional Bore 408
201 N. 3rd Avenue
Walla Walla, WA 99362-1876
FOR ADDITIONAL INFORMATION: Should you need additional information or have any questions, please contact the Corps environmental coordinator for the project at (509) 527-7265.