2016-10-10-minutes-public-works-study-session

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OF United States Department of the Interior o�Pp�NENT N � D $ BUREAU OF RECLAMATION Pacific Northwest Region �4RC, .e COIUImbla-Cascades Area Office 1917 Marsh Road i,Rrrn RerrR n, Yakima, WA 98901-2058 CCA -5700 APR 7 2016 PRJ-3.00 VIA ELECTRONIC MAIL ONLY Mr. Mark Cook, Director Kittitas County Public Works 411 N. Ruby Street, Suite I Ellensburg, WA 98926 Subject: Schaake Levee Repair Dear Mr. Cook: As you are aware, the U.S. Army Corps of Engineers (CORPS) has determined that a portion of the Schaake levee, just downstream of where the Tjossent access channel returns to the Yakima River, is in need of repair. Ms. Cathie Desjardin has communicated the Corps intent to repair approximately 350 feet of the levee in this area (Figure 1). The Corps' proposed repair is presented as Figure 2 and entails setting back the existing levee a distance of approximately 20 feet. Under Public Law 84-99 (PL 84-99), Kittitas County (as the non -Federal owner of the levee) is responsible for 20 percent of the repair cost. As conveyed by Ms. Desjardin in her April 1, 2016 e-mail, the intent of the Corps' repair is to repair the toe, embankment, and armor that were damaged by flooding this past winter and not to improve the levee. However, being familiar with the Schaake levee and dynamics of the Yakima River at this location, we would like to bring a few suggestions to your attention that we feel will benefit Kittitas County and the Bureau of Reclamation in the long term. Given the sizeable effort to setback the levee as proposed by the Corps, we believe these suggestions will have a relatively minor impact on the cost of the repair but will significantly reduce the risk of the levee failing when the next 5- to 10 -year flow event occurs. Reclamation and our consultant (CH2M) have discussed the Corps' intended design and repair for this portion of the Schaake levee as it related to our greater restoration design and levee setback on the property. In the latest design (30 percent), Reclamation proposes to retain the portion of the Schaake levee in the vicinity of where damage occurred this past winter, primarily for protection of the Tjossem irrigation infrastructure in this area (Figure 3). The Yakima River's energy against the left bank at this location is significant, as evidenced by the failure of the levee protection during a moderately frequent flood (less than a 10 -year return interval in this latest case). River conditions at this location are becoming more similar to those at the