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Home My WebLink AboutMINUTES - 04251989 - 2.4 4 • O TO: BOARD OF SUPERVISORS, AS THE GOVERNING BODY OF THE CONTRA COSTA COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT FROM: J. MICHAEL WALFORD, CHIEF ENGINEER DATE: APRIL 25, 1989 SUBJECT: Wildcat and San Pablo Creeks Corps of Engineer Project Specific Request(s) or Recommendation(s) & Background & Justification I. RECOMMENDATION ACTION A. ACKNOWLEDGE receipt of a letter from the Corps of Engineers which indicates that the approved plan of a concrete channel lining for San Pablo Creek between the railroad tracks can be completed by the fall of 1990, a year ahead of the gabion walled alternative and that the concrete channel will be less costly and will provide significant flood hazard reductions immediately upstream of the Atchison, Topeka and Santa Fe Rail- road's bridge. B. DIRECT the Chief Engineer to request the Corps of Engineers to consider the feasibility of a gabion walled channel in the above reach when they conduct their proposed- hydraulic model study for Phase II. C. DIRECT the Chief Engineer to present the results of the Corps of Engineers model study and a detailed estimate of costs for the two alternatives when available to permit a decision by the Board as to which alternative should be implemented. Continued on attachment: X yes Signature: Recommendation of County Administrator Recommendation of Board Committee Approve Other: Signature(s) : Action of Board on: Approved as Recommended Other Vote of Supervisors I HEREBY CERTIFY THAT THIS IS A TRUE AND CORRECT COPY OF AN _ Unanimous (Absent ) ACTION TAKEN AND ENTERED ON Ayes: Noes: THE MINUTES OF THE BOARD OF Absent: Abstain: SUPERVISORS ON DATE SHOWN. Attested .f,Z;i.�•-(� z Si /f f�l Orig. Div. : Public Works (DESIGN) PH L BATCHELOR, cc: County Administrator CLERK OF THE BOARD County Counsel OF SUPERVISORS AND Community Development Director COUNTY ADMINISTRATOR Public Works Director PW Design By PW Accounting DE TY CLERK tl GC:rs bo:25.t4 -1 t Wildcat-San Pablo Creeks Page 2 D. DIRECT the Chief Engineer to monitor the Corps of Engineers schedule and to bring this issue back to the Board whenever it is determined that the Phase II work will not be implemented thereby cancelling the planned hydraulic model study or the study does not stay on schedule thereby threatening the implementation of the needed channel improvements on San Pablo Creek between the railroad tracks in calender 1991. II. FINANCIAL IMPACT The Chief Engineer's report indicates that the gabion channel wall will result in higher project costs of approxi- mately $75, 000.00 and higher future maintenance cost of approximately $3,500.00 annually. In addition, the Corps of Engineers has determined that a one year delay in implement- ing these channel improvements will result in a three (3) percent cost increase. The cost of including a gabion channel wall alternative in the hydraulic model study is expected to be negligible. III: REASONS FOR RECOMMENDATION/BACKGROUND On March 21, 1989, the Board of Supervisors considered the final report from the Wildcat and San Pablo Creeks Project Design Team which recommended a gabion walled channel alternative on San Pablo Creek between the railroad tracks, the report from the Chief Engineer recommending implementa- tion of the Corps of Engineers' approved plan alternative of a concrete channel lining, and letters stating preferences regarding channel lining type. The Board directed the Chief Engineer to solicit input from the Corps of Engineers regarding timing, cost and flooding potential impacts due to implementation of each alternative. The Corps of Engineers has responded in the attached letter. The Corps of Engineers has not programmed into their budget for 1990 sufficient funds to construct the channel improve- ments on San Pablo Creek between the railroad tracks. Consequently, the earliest this reach of channel can be improved is 1991. Based on the absence of funding and the believed minor cost to conduct an alternative wall analysis in the hydraulic model study, we recommend that the request of the Design Team be implemented provided the model study does not delay the construction of the needed improvements beyond 1991. IV. CONSEQUENCES OF NEGATIVE ACTION The project cannot proceed without a decision on this issue. - - oa nu 9 25 C G C4 Puits L_ - j DEPARTMENT OF THE ARMY SACRAMCNTO DISTRICT CORPS OF ENGINEERS APR 14 RECT 460 CAPITOL MALL SACRAMENTO,CALIFORNIA 93814.4794 fli►LY To Ap r i 1 If!; 1989 AT'rr.NT►ON OF Civil Design Branch Mr. Milton F. Kubicek, Deputy Director Contra Costa County Flood Control and Water Conservation District 255 Glacier Drive Martinet, California 94553 Dear Mr. Kubiceks This letter is in response to your verbal request for the hydraulic design ramifications, time schedule, and cost indexing for Contract 3A, Reach 1 , Wildcat and San Pablo Creeks, California, project. Contract 3A of Reach i encompasses the area between Southern Pacific Transportation Company's (SPTC) railroad bridge through Atchison, Topeka and Santa Fe Railroad ' s (ATSF) bridge to Giant Highway an San Pablo Creek. Following are our responses to your request: ' a. With a favorable benefit cost conclusion from the Decision Paper, Reach 2, scheduled to be completed this summer , a physical hydraulic model study will be conducted in the fall and winter of 1989/1990. The model study on San Pablo Creek is to evaluate and design the bypass and junction features of this system in Reach 2. b . The result of a sensitivity study (July 8, 1988) on San Pablo Creek showed that a channel could be designed and constructed prior to obtaining the results of the physical hydraulic model study if the channel was rectangular in shape and concrete lined. Construction of Contract 3A will establish design contraints for the upstream features of Reach 2, but will provide adequate conservatism for the design of Reach 2. c. Wildcat and San Pablo Creeks, California, Floodplain Delineation Final Report, January 1989, determined the floodplain boundaries and flooding depths for Reach 2. For pre-project conditions, discharges are lost from San Pablo Creek on a point-to-point basis progressing downstream to Giant Highway. The upstream limit of the study reach has a design flow of 5, 100 efs confined within the channel banks. r"ILJ 9 26 C C CO PVt � a r- -2- At the Giant Highway bridge the flow is 2,820 cfs with a water surface elevation of approximately 30 feet N.V.G.D. if Contract 3A was completed the channel capacity at the entrance to Reach 1 (Giant Highway) would be increased. The Floodplain Report indicates post-project conditions with the full design flows reaching Giant Highway will produce a water surface elevation of approximately 22 ft . N.G.V.D. The "draw-down" effect would be realized a "short" distance upstream as hydraulic control reverts back to channel size, shape, and roughness in Reach 8. Flooding would be eliminated entirely between the two railroad tracks if Contract 3A was completed. d. Estimated construction cost increases for 1989 to 1990 period are approximately 2 to 3 percent. e. Our current schedule for design and construction of Contract 3A reflects the timetable required for the physical model study of San Pablo Bypass, Reach S. We anticipate Construction of Contract 3A in FY 1991 . Construction could commence in late 1990. Construction of Contract 3A can proceed before completion of the physical model study. The construction of a rectangular concrete channel in this short reach between the two railroad tracks will not jeopardize or compromise the future bypass design on the upstream reach of San Pablo Creek. The environmental benefits associated with the bypass design will still be obtained. Sincerely, b.ewis A. Whitney Chief, Engineering Division