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HomeMy WebLinkAbout09/17/2002, LIAISEN - ZONE 9 MEETING OF SEPTEMBER 11TH �a� ITEM#� LIAISON REPORT To: Mayor& City Council CUNCIL ❑ CDD OR From: Jan Howell Marx, Vice Mayor A0 ❑ FIN DIR /CAO ❑,FIRE'CHIEF Re: Zone 9 Meetingof September 11th cy, TTORNEY O FW DIR -. Date: September 17, 2002 6 CLERV40RI© O=POLICE CHF O D T- DS ..d REC01A 1 61 UTIL DIA _ MR 01A THE BAD NEWS: PUBLIC WORKS: There has been a lot of County staff turnover in regards to Zone 9, which has resulted in some confusion and disorganization. After Susan Litteral retired, John Waddell took her position as county coordinator of.Zone 9. He then received a promotion and Tim Tomlinson took over the job. This will be a temporary position. It is not clear whether Susan Litteral's replacement, once hired, will have Zone 9 responsibility. John French, the City resident representative has not received any notice of the Zone 9 meetings from county staff, although he was officially appointed by the Board of Supervisors. Additionally, the County Public Works Department is not providing the minimal staff support necessary to accomplish Zone 9 projects. Steve Gregory reported that Zone 9 and Brian Stark of the Land Conservancy have a crucial north of SLO stream restoration/flood control project funded by a grant, have the CCC workers scheduled to do the work, have a willing land owner, but because no one representing the County can be available, the project cannot go forward. The County Deputy Director of Public works attended this meeting, and promised to find someone to take 2 or 3 hours out of his day to supervise the work on behalf of the County. PLANNING: The County also has no staff from its Planning Department assigned to Zone 9 matters. Matt Jensen was the long time Planner, but he left. Mark of Planning replaced him, but was then reassigned. Now, no one has Zone 9 responsibility. This means there is no one to shepherd the Zone 9 master documents [Drainage Design Manual (DDM), Stream Management and Maintenance Program (SMMP) and Waterway Management Plan (WMP)] through the County EIR process. These documents must be jointly certified by the City and the County. But, it is not clear that the County will assign staff to complete this task. The environmental standards proposed for the SLO Creek Watershed are higher than the standards in the County as a whole, and therefore may be controversial in the County. I have proposed that the SLO Watershed be handled through a separate overlay, so that the Supervisors would be looking at only one watershed, not all the watersheds in the County when they consider Zone 9 issues. ACTION: I would like the Council to direct staff_ to work with County Staff on quicklyED resolving these problems. RECEIVED SEP 17 ?P11 SLO CITY CLERK GOOD NEWS DATA: few months ago the validity of the data utilized by Questa Engineering (The City and Zone 9's consultant) was questioned by Russ Kiessig. In an abundance of caution, Zone 9 submitted the data to the U.S. Army Corps of Engineers. They have issued a written opinion (attached) that the data utilized by Questa Engineering is "well organized and technically sound". PERMITS: Since the data on which the studies and the EIR are based has already been accepted by the Army Corps, any number of unforeseen obstacles to the permit process has been eliminated. Bruce Henderson from the Army Corps, who attends the Zone 9 meetings, is advising Questa on the application process, which is going forward concurrently with the EIR.. EIR: The Morro Group (Mary Reents) is working on the EIR for the Zone 9 Master Documents. The EIR will be formally circulated in December and January. ATTENDANCE: Cal Poly, Cal Trans, the Regional Water Quality Board and Army Corp have been sending people to the Zone 9 meetings. Their interest, expertise and input have been a real help as we deal with these technical issues. CESPL-ED-HH 22 July 2002 MEMORANDUM FOR CESPL-CO-RN(Bruce Henderson) CESPL-CO-R(David Castanon) SUBJECT: H&H Technical Assistance to Regulatory—San Luis Obispo Creek Project 1. References a) Appendix B—Hydrology and Hydraulic Studies" of San Luis Obispo Creek by Questa Engineering b) The January and March 1995 Sycamore Mineral Springs Resort Floods, San Luis Obispo County, California by Hugo Loaiciga- Sept. 2001 2. Overview—The Hydrology and Hydraulic Section(H&H) of the U.S. Army Corps of Engineer(COE), Los Angeles District was requested by the COE Regulatory Branch(Regulatory) to provide technical assistance in their review of the two H&H reports referenced above on the Flood of January and March 1995 on San Luis Obispo Creek. Reference l a was conducted by Questa Engineering(private firm) for the County of San Luis Obispo. Reference lb was conducted by Dr. Hugo Loaiciga of UC Santa Barbara for the Sycamore Mineral Spring Resort (SMSR). According to Regulatory, there appears to be a significant dispute regarding the results of the hydraulic studies. It is not clear whether Regulatory is referring to discharge-frequency or the subsequent floodplain analysis. Discussions of the two reports are as follow: 3. Appendix B—Hydrology and Hydraulic Studies" of San Luis Obispo Creek by Questa Engineering General: Regulatory submitted only"Appendix B —Hydrology and Hydraulic Studies" to H&H for review. Ideally, the main report should have been submitted to provide an overall purpose of the study and aid in the review of the H&H Appendix. The report was somewhat comprehensive, covering the hydrologic analysis (discharge frequency and the development of the watershed rainfall runoff models) and hydraulic analysis (floodplain analysis). In addition to San Luis Obispo Creek, six other creeks within the watershed were analyzed(Prefixmo, Stenner, Brizzioiari, Orcutt, Acacia, and East Branch SLO). Presented below are some of the noted issues in this report. a. CALIBRATION TECHNIQUE AND RESULTS—As a part of the calibration discussion, the report stated that the"HEC-RAS model does not account for debris blockage", Page B-24. This statement is incorrect. HEC-RAS does have a function to account for debris blockage. If Questa had accounted for debris loading, the bridge discharge curve would have been relatively higher in elevation for the same discharge. b. "Reality Check, Page B-22" - Since there are no stream gage available on San Luis Obispo Creek for the March 1995 stone, Questa used high watermarks to back calculate the discharges. They also used the high water marks to adjust the channel roughness coefficients. This points to the obvious conclusion that they used one known(high water mark or water surface elevation) to determine two unknowns(channel roughness and flowrate). The report simply stated that, "The reality check for the hydraulic model came from trying to make high water marks for any given region consistent with one another." While this procedure is a method to develop discharge information, we believe that what they meant to say is that the results of this procedure produced"n"values and discharge results that are consistent for the region based on engineering expertise. 4. The January and March 1995 Sycamore Mineral Springs Resort Floods, San Luis Obispo County, California General: This report focused on a short reach of the San Luis Obispo Creek just upstream of the SMSR. The intent of this report was to analyze the storm events of January and March of 1995 on this particular reach of San Luis Obispo Creek and address the impact on SMSR. Although some of the conclusions made in this report may be valid, the data presented does not fully support its arguments. Also, we were not provided with the accompanying figures, which made the review process more difficult. Presented below are the discussions of some of the major issues presented in the report. a. RAINFALL EVENTS—The report claims to show that the rainfall events that occurred within the City of San Luis Obispo on January and March 1995 were less than a 10-year rainfall event(between 5- and 10-year). The conclusion was based on a comparison of the measured rainfalls in the City of San Luis Obispo with statistical data from a gage that is 13.5 miles east of the San Luis Obispo Creek Watershed. (Herein after referred to as the Lopez gage). The approach would indicate that the measured rainfalls in the City were less than 10-year rainfall events. There is no statistical analysis for the rainfalls that occurred in the City. The report fails to mention that the measured rainfalls in the City were closed to the rainfalls of record (1 hour and 2 hour duration)or even higher than the rainfalls of record(3 hour duration) at the Lopez gage. The conclusion that the January and March 1995 rainfalls was less than a 10-year event is based on an over-simplified methodology subject to interpretation. It is our opinion that an analysis of a rainfall event can not be accomplished by using just one rainfall gage, especially with a gage that is 13.5 miles from the watershed that may be influenced by hydrologic factors such as orographic patterns and elevations. Data from other gages would be needed to make the determination of the rainfall event. Also, the statistical data of the gage seems to be suspicious. The translated measured city rainfall data fell towards the high end of the recorded rainfall at the Lopez gage. How could the city rainfall be closed to the highest recorded rainfall at the Lopez gage and still be less than a 10-year event. This would suggest that there were not many years of record in the frequency analysis of the rainfalls. Yet, all of the rainfalls of record occurred in either 1969 or 1972. Was the gage discontinued at some point? b. FLOOD PLAIN CHANGES -The report cited six changes in the flood plain that reduced the hydraulic capacity on the channel to convey flow. It is clear that some changes (such as the Ontario Road Bridge and vegetation growth) would have an impact on the creek. However,the report did not convincingly establish the impacts of each change to the creek. Yet, it assigned a percentage of contribution for certain factors. c. HYDRAULIC ANALYSIS OF FLOODS—The author used HEC-2 to develop a river hydraulic model of the creek. It was not stated in the report where the survey that was used for the HEC-2 modeling came from or when it was.taken. Models were developed for the pre-development condition(1969) and the 1995condition: Estimations of the channel roughness coefficients were made for the pre-development condition without any data such as aerial photos or photographs of the creek. d. Finally, the report argues that the rainfall for the 1995 event was less that a 10-year rainfall event, yet it uses the 50-year flowrate in the hydraulic models to reproduce the measured high water marks. Is this report trying to prove that a 10-year rainfall is causing 50-year flooding because of changes in the creek and the floodplain? The translation of a 10-year rainfall to produce a.50-year flood is unreasonable. Generally, floodplain analysis should be based on stream discharge data or regression analysis of the region to produce discharge-frequency. Hydrologic models are then calibrated to the discharge-frequency. 5. Conclusion—It is our opinion that the H&H information presented in the Questa's report would better represent the conditions of the region. The Questa study is well organized and is technically sound. It used the data from an actual event(1995)to calibrate the hydrologic and hydraulic models for San Luis Obispo Creek Watershed. The scope of the report was much broader than the analysis of the 1995 events. Dr. Loaiciga's report mainly focused on a single flooding event that occurred during this period on a short reach of the San Luis Obispo Creek. Some of his conclusions tend to be unsubstantiated. Cuong T. Ly, PE Senior Hydraulic Engineer CF: CESPL-ED-HH