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HomeMy WebLinkAboutButte Basin Flood Relief Structure 3Bs o �`T F� Department of PublicWorks ° °0 County of Butte 0 0 0 0 0 7 County Center Drive 0 0 J.Michael Crump,Director OroviRe,CA 95965-3397 COZ j N' � Shawn H.O'Brien,Assistant Director (530)538_7691 rc �g (FAX)538-7171 BOARD OFSEIPmVison January 8, 2010 JAN 0 8 2010 oRovlu.E,CALIFORNIA Merritt Rice, P.E. Department of Water Resources Statewide Flood Planning Office 902 P Street,Room 313 A Sacramento, CA 95814 Re: Butte Basin Flood Relief Structure 3Bs Dear Mr. Rice: The documents being developed for the State Plan of Flood Control (SPFC), highlight the critical importance of Butte Basin for flood attenuation and then state that it is not a part of the SPFC. The Butte Basin Overflow is an integral project related to the Sacramento River Flood Control Project (SRFCP),the Sacramento River Bank Protection Project and the State Plan of Flood Control. The objective of the Butte Basin Overflow was to ensure a division of flows between the Sacramento River and Butte Basin. Butte Basin provides relief from high river flows, such that flood flows in the Sacramento River channel would not exceed the specified channel capacity between project levees downstream. The Butte Basin has a significant attenuation effect on flows before discharging them into the Sutter Bypass downstream from Colusa. The Butte Basin analysis indicates it would hold more than 1 million acre-feet when it is flowing full and has a travel time of about 2 days from its upper end to the Sutter Bypass, however this storage capacity may no longer be valid. The Butte Basin Overflow includes two basic elements: a bank protection element (river channel stabilization), consisting of about 31,500 linear feet of bank protection on the Phelan Levee and Murphy Slough Plug, and an overbank flow element. The overbank flow element consists of three designated overflow areas the M&T Flood Relief Structure (FRS) and Goose Lake FRS (formerly known as Parrott FRS), which have been designed and constructed to Corps Standards and are maintained by the Department of Water Resources (DWR), and 3Bs FRS consisting of a silt weir not constructed to Corps or DWR Standards. Problems with Butte Basin are three fold, first and most important is the 3Bs FRS, which was unfortunately not constructed to Corps standards in the late 1980's like M&T FRS and Goose Lake FRS. In an initial flooding there are head cuts to 3Bs FRS that allow Butte Basin to be flooded or surcharged (reducing the attenuation capacity) when the Sacramento River is below warning stage. In 1998, there were 28 consecutive days of flooding causing' needless and extensive damage to agriculture and infrastructure as well as interrupting interstate commerce. These head cuts have repaired through the good graces of the individual farming the land; however we cannot depend upon this type of support forever. While this nuisance flooding is damaging Butte and Glenn Counties, it is also reducing the flood storage capacity of Butte Basin. Water levels in Butte Basin will peak at a different time than the Wuu.%.ivaaut-a"a EGr'G G VL L January 8, 2010 Sacramento River and may not allow enough flow to escape at the Moulton and Colusa Weirs to protect the Sacramento River levees from overtopping. The December 1986 Environmental Impact Report for the Butte Basin Overflow Area indicates that the 3Bs should not overtop until the Ord Ferry Gage reaches 114.0, however overtopping has been experienced at a gage reading of 111.0. This nuisance flooding can be stopped by a project to construct the 3Bs to Corps and DWR standards, such that it will not overtop until the Ord Ferry Gage reaches 114.0. The second problem is the Phelan Levee, according to the geologic map for the area between Chico Landing and Ord Ferry Road, this levee is resting on natural channel deposits and can easily be undermined in a major event allowing uncontrolled flows from the Sacramento River into Butte Basin causing unnecessary damages to agriculture and infrastructure, in addition to surcharging Butte Basin. The third problem is the flooding of rice fields for decomposition and migratory waterfowl habitat. While this cannot be changed, Butte Basin should be reevaluated for an accurate estimate of flood storage and attenuation capacity. If you should have any questions concerning this matter, please contact this office Monday through Friday, 7:30 a.m. to 4:30 p.m. at(530) 538-7681. Si ncer y, Mike rump, P.E. Director of Public Works cc: The Honorable Board of Supervisors Dan McManus, Special Investigations Branch, DWR,Northern Region Office 2440 Main Street, Red BIuff, CA 96080 Roger Putty, MWH,Upper Sacramento Work Group Tech Lead, MWH, 3321 Power Inn Road, Suite 300, Sacramento, CA 95826 Scott Rice, 2870 Gateway Oaks Drive, Suite 300, Sacramento, CA 95833 Michele Ng,P.E., Department of Water Resources, 3310 El Camino Avenue, Room 113, Sacramento, CA 95821-9000 Les Heringer, M&T Ranch, 3964 River Road, Chico, CA 95928 Jason Larabee, P.O. Box 172, Butte City, CA 95920