US Army Corps of Engineers
Walla Walla District

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15-045 Corps seeks public comments for Mill Creek levee maintenance draft FONSI and Environmental Assessment

Published July 24, 2015

WALLA WALLA, Wash. – The U.S. Army Corps of Engineers’ Walla Walla District (Corps) invites public comments on a draft Finding of No Significant Impact (FONSI) and Environmental Assessment (EA) and for maintenance to occur along the landward-side of the Corps-managed portion of the Mill Creek Levee System in Walla Walla. Comments are due no later than August 24.

For safety, the Corps proposes to remove woody vegetation from the landward side of the levees, beginning in October 2015. The maintenance is being proposed in order to meet National Levee Safety Program maintenance requirements in accordance with U.S. Army Corps of Engineers Headquarters regulations and policies.

The EA and draft FONSI are available on the project webpage -- Also see additional links to a fact sheet and video about the levee maintenance to be conducted, a levee cross-section graphic, work-area map and other related information.

Public comments will be accepted July 24 through Aug. 24, 2015. You may submit comments electronically via email to, or by U.S. Postal Service to:

U.S. Army Corps of Engineers, Walla Walla District
CENWW-PM-PD-EC, ATTN: Mill Creek Levee Maintenance
201 North 3rd Avenue
Walla Walla, WA 99362

A public meeting is planned for Wednesday, Aug. 12, 2015 at 5 p.m. at the Airport Terminal Building Conference Room, 45 Terminal Loop Road, Walla Walla, Washington. At this meeting, the Corps will give a presentation on the need for levee maintenance, answer questions from attendees and accept written comments. Following the meeting, District Levee Safety Program experts will offer a tour of the proposed action area. Although the route is mostly paved, it is recommended that tour participants wear sturdy walking shoes.

Questions about the EA or draft FONSI should be emailed to the Corps’ environmental coordinator at

BACKGROUND (for public release)

“It is important for people not to forget why these levees were constructed. They were not built for the gentle flows that are seen in the channel on a regular basis, they were constructed to perform during flood-stage events.” – Frank Wachob, USACE Civil Engineer

The Mill Creek Flood Control Project was completed in 1942 and included levees along the improved Mill Creek channel to provide flood protection for the City of Walla Walla. Currently, the Mill Creek Project levees fail to comply with U.S. Army Corps of Engineers vegetation standards used to ensure reliability, resiliency and operability of levee, floodwall, and dam projects nationwide.

Non-compliant vegetation on levees blocks visibility for inspections, access for maintenance, hinders flood fighting, and adds uncertainty to structural performance and reliability, which increases risk. The inability to inspect, maintain or flood fight could contribute to a breach or delay emergency response.

Over many years, the Corps has been trying to formulate a viable solution to address levee-maintenance issues at Mill Creek that has minimal impact on the aesthetic quality of the popular trails. Because of funding priorities and lack of staffing, we were unable to make much progress in this area. During the time that passed, the vegetation grew out of control and encroached into the levee maintenance zone.

Not knowing if our levees are in good condition and ready to perform during a flood is an unacceptable risk to public safety. It is not an option to continue to allow non-compliant vegetation to potentially put lives at risk.

Our levees must be properly maintained to ensure they perform as designed – Ensuring our levees meet required safety standards will be a multiple-year effort. The following tasks need to occur as funding becomes available: clear the maintenance zone, remove stumps, repair the levee structure, and plant grasses.

This is about public safety – Life safety is paramount for the Corps’ operations. Not being able to access the levee for inspections and maintenance adds uncertainty about the levee’s structural performance and reliability in the event of a flood, which increases risk to the public.

Right now, if we had to engage in a flood fight, we wouldn’t be able to see if problems were developing, much less take swift action to place sandbags or operate heavy equipment to construct reinforcements.

We are considering the environment – The Corps has gone to great effort to minimize the amount of woody vegetation that needs to be removed. We recently surveyed the levees and are measuring the maintenance zone from the base of the original design slope (called the toe) instead of the actual physical slope, which extends far beyond the design toe in many locations.

Work will be conducted outside bird-nesting season, and a qualified biologist will inspect the trees prior to removal.

The Corps maintains about two-thirds of Mill Creek Project lands for habitat purposes (412 of 612 total acres). We estimate less than 6 acres of woody vegetation will need to be removed from the levee maintenance zone. Once the zone is cleared and levee repairs completed, grasses will be planted to improve the aesthetics and benefit insects. Vegetation outside the zone will be allowed to develop naturally.



Release no. 15-045