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HomeMy WebLinkAboutPA2022-0254_20221101_Coastal Hazards Analysis Report dated 10-24-22 WILLIAM SIMPSON & ASSOCIATES, INC. CONSULTING STRUCTURAL ENGINEERS 23 ORCHARD, SUITE 250 PH. (949) 206-9929 LAKE FOREST, CA 92630 FAX (949) 206-9955 www.wsase.com e-mail: Tmail@wsase.comT Page | 1 October 24, 2022 76 Linda Isle Newport Beach, CA 92660 RE: COASTAL HAZARDS ANALYSIS REPORT Applicant: Marcus Hernandez WSA Job #7738 Mr. Hernandez, Pursuant to your request, William Simpson & Associates, Inc., (WSA) is pleased to provide this report regarding Coastal Hazards Analysis for the proposed development at the subject site. The site is adjacent to Newport Bay; thus, it may be subject to Coastal Hazards such as, flooding, wave runup, and erosion. This study investigates the potential for the aforementioned hazards to impact the proposed development on the site over the next 75 years and addresses compliance with Coastal Hazards Analysis Report requirements and standard of NBMC Section 21.30.15.E.2. STATEMENT OF THE PREPARER’S QUALIFICATIONS Masoud Jafari, S.E., the preparer of this report, holding a Bachelor of Science Degree in Structural Engineering from Tehran, Iran, is a Licensed Civil Engineer - Certificate No. C43673 - and Structural Engineer - Certificate No. S3812 - by the State of California. He joined the company in 1987 and is now partly the owner, serving as the principal in charge of the company. He has been actively involved in the design and entitlement of waterfront developments such as custom homes, seawalls, piers, platforms, floating docks and marinas for over 30 years. All the above being said, Masoud Jafari, S.E. shall be considered a qualified preparer for the Coastal Hazard Analysis Report on this project. Requirements in Appendix A for Step 1: Establish the project sea level rise range for the proposed project’s planning horizon (life of project) using the current best available science. The State of California Sea-Level Rise Guidance 2018 update developed by the Ocean Protection Council in close coordination with Policy Advisory Committee with representation from California Natural Resources Agency, the Governor’s Office of Planning and Research, and the WILLIAM SIMPSON & ASSOCIATES, INC. CONSULTING STRUCTURAL ENGINEERS 23 ORCHARD, SUITE 250 PH. (949) 206-9929 LAKE FOREST, CA 92630 FAX (949) 206-9955 www.wsase.com e-mail: Tmail@wsase.comT Page | 2 California Energy Commission provides a bold, science-based methodology for state and local governments to analyze and assess the risks associated with sea-level rise, and to incorporate Sea- Level Rise into their planning, permitting, and investment decisions, and it is considered the current best available science. As reflected in the clouded area of the enclosed Table 28, based upon direct interpolation of the data for Medium-High Risk Aversion and Low emissions 2090 & 2100 and, over the project’s planning horizon of 75 years, the estimated Sea-Level Rise for year 2097 shall be 5.13’. Using direct interpolation of the data for Medium-High Risk Aversion and High emissions 2090 & 2100 and, over the project’s planning horizon of 75 years, the estimated Sea-Level Rise for year 2097 shall be 6.28’. Based on the highest high tide of +7.7’ NAVD88, the above established Sea-Level Rise will account for bay water level of +13.98’ NAVD88 for Medium-High Risk Aversion and High emissions. For Medium-High Risk Aversion and Low emissions the bay water level would be +12.83’ NAVD88. Per City of Newport Beach Municipal Code standards, we have enclosed Table 28 with interpolated data for High emissions 2090 & 2100 and Low Risk Aversion. Based on that interpolation, the estimated Sea-Level Rise for year 2097 shall be approximately 3.05’, which is much smaller than the governing estimated SLR for Medium-High Risk Aversion. Based on the highest high tide of +7.88’MLLW (7.70’NAVD88) recorded in the project area, the above established Sea-Level Rise will account for bay water level of +10.90’NAVD88. Requirements in Appendix A for Step 2: Determine how physical impacts from sea level rise may constrain the project site, including erosion, structural and geologic stability, flooding, and inundation. According to the enclosed Grading Plan C-1 the lowest finished elevation of the proposed development shall be at +10.90’ NAVD88=+11.08’MLLW which follow the Base Flood Elevation established for the area. Based on the SLR established in Step 1 above, 1st floor of the proposed structure will remain above High Tide sea level approximately until 2060 upon Medium-High Risk Aversion probabilistic projections and until 2100 upon Low Risk Aversion probabilistic projections. As we well know, majority of the public streets in Newport Bay area are currently at much lower elevations than the subject site and they will flood due to SLR way before the development on this site becomes subject to flooding. FLOODING HAZARD The primary hazard due to flooding from the ocean waters for this site, like majority of the sites located adjacent to Newport Bay, would be due to long term Sea-Level Rise. The current water levels in Newport Bay are reflected on the enclosed Datums for Newport Bay Entrance. WILLIAM SIMPSON & ASSOCIATES, INC. CONSULTING STRUCTURAL ENGINEERS 23 ORCHARD, SUITE 250 PH. (949) 206-9929 LAKE FOREST, CA 92630 FAX (949) 206-9955 www.wsase.com e-mail: Tmail@wsase.comT Page | 3 While Sea-Levels have been rising for decades, higher rates of raise are forecast for the coming century because of climate change – see enclosed table 28. Increases can be attributed to warmer temperatures, which cause water to expand, as well more liquid mass caused by melting of ice caps. Current estimates of future SLR generally fall in the range of 5.4-6.7 ft for the year 2100. Global warming may impact flooding in other ways as well. Warmer water could intensify North Pacific storms, bringing greater wind and wave energy to shoreline in winter and higher intensity precipitation. The Newport Beach Peninsula portion of the Pacific Institute California Flood Risk Map is shown herein as OE S Quadrangle. The dark blue colored areas show the areas where a 100-year Sea-Level Rise of 55 inches is added to the existing FEMA coastal flood elevation shown in light blue. Obviously, the entire Newport Bay area will be affected if sea level rises 55 inches by the year 2100. If the sea level rises in the next several decades as currently estimated, regional measures to mitigate the potential flooding hazard shall be taken. Since top of the new stem wall is at +10.9’ NAVD88, it will remain above the high tide approximately until year 2070. In the event that SLR prediction of 6.00’ for year of 2095 holds true, the concrete deck shall accommodate raise to top of wall elevation of +13.7’NAVD88, as reflected on the enclosed S-2. WAVE RUNUP Wave runup is the uprush of water from wave action on a shore barrier intercepting Stillwater level. On steeply sloped shorelines, the rush of water up the surface of the natural beach, including dunes and bluffs, or the surface of a manmade structure, such as revetment or vertical wall can result in flood elevations higher than those of the crest of wind-driven waves. See wave Runup Sketch below. Due to its location, this site is not a subject to typical ocean waves and the associated wave runup. For sake of narrow width of the channel and wake restrictions, significant wave or boat wake is not expected. Small wave or small boat wake waves are generally dampened by the moored vessels and dock systems located in front of the site and have no significant energy and runup effect. WILLIAM SIMPSON & ASSOCIATES, INC. CONSULTING STRUCTURAL ENGINEERS 23 ORCHARD, SUITE 250 PH. (949) 206-9929 LAKE FOREST, CA 92630 FAX (949) 206-9955 www.wsase.com e-mail: Tmail@wsase.comT Page | 4 Tsunami type waves that approach from the ocean shoreline will likely not reach the site for several reasons. There is no significant near field source of a tsunami like the geologic conditions of some other places on Earth such as Japan, for example. A far field tsunami reaching the ocean shoreline will likely not reach the site because of the distance and developments between the shoreline and this site. Due to its very infrequent occurrence – 500-year recurrence interval – tsunami should not be considered a significant impact over the life of the proposed structure - 75 years. EROSION HAZARD Erosion refers to the wearing or washing away of coastal lands. Beach erosion is a chronic problem along many open ocean shores of the United States. To meet the needs for comprehensive analysis of shoreline movement, the United States Geological Survey has conducted analysis of historical shoreline changes along open ocean sandy shores of the conterminous United States and has produced an Open-File Report 2006-1219 entitled “National Assessment of Shoreline Change Part 3: Historical Shoreline Change and Associated Coastal land Loss Along Sandy Shorelines of the California Coast”. The report looks at survey data of the following periods: 1800s, 1920s-1930s, and 1950s-1970s, whereas the lidar shoreline is from 1998-2002. The report looks at both long-term and short-term changes. According to the report, the average rate of long-term shoreline change for the State of California was 0.2±0.1 m/yr., and accretional trend. The average rate of short-term shoreline change for the state was erosional; with an average rate of -0.2±0.4 m/yr. The seawall location of this site is stabilized and not subject to significant long-term erosion. Review and analysis of historical aerial photographs and field measurements for seawall repairs in the area show no change in the position of the shoreline over the last several decades. The future shoreline changes over the next 75 years are assumed to be the same as in the previous several decades. However, there is a rapid rate of sea level rise predicted in the next 75 years. If that prediction holds true, the rapid sea level rise may accelerate shoreline erosion, but it shall not impact the structure on the subject lot over its economic life due site location. CONCLUSION In conclusion, flooding, wave runup and erosion will not significantly impact this property over the proposed life of the development. The existing seawall/bulkhead is required to protect the proposed structures on the lot, the adjacent properties, public facilities and infrastructure; thus, it can’t be removed. Removal of the seawall/bulkhead will result in erosion and undermining the foundations of the structures and site walls at the subject site and both adjacent sites. Once the existing seawall/bulkhead is repaired/reinforced in compliance with the enclosed drawings S-2, need for a new shoreline protective devise shall not anticipated over the economic life of the proposed development to protect it from flooding, wave runup or erosion. Waterproofing flashing or waterproofing curbs around the perimeter of habitable rooms shall not be required. If found not adequate for the actual sea level rise over the next 75 years, the existing seawall/bulkhead assembly, including the concrete wall at the entire bayward edge of the new concrete deck, allows to be increased in height to+13.7’NAVD88 without further seaward encroachment. If during this period the seawall/bulkhead displays any sign of distress that requires immediate attention, due to some unforeseen catastrophic or disastrous events, it WILLIAM SIMPSON & ASSOCIATES, INC. CONSULTING STRUCTURAL ENGINEERS 23 ORCHARD, SUITE 250 PH. (949) 206-9929 LAKE FOREST, CA 92630 FAX (949) 206-9955 www.wsase.com e-mail: Tmail@wsase.comT Page | 5 should be repaired or replaced at that time accordingly, without seaward encroachment from its current location. The above conclusion was prepared based on the existing conditions, proposed drawings, current projection of future sea level rise, and within the inherent limitations of this study, in accordance with generally acceptable engineering principles and practices. We make no further warranty, either expressed or implied. William Simpson & Associates, Inc. appreciates the opportunity to work with you towards the successful completion of your project. Should you have any questions regarding this report, please give us a call. Respectfully submitted, Masoud Jafari, S.E. Principal Enclosures: Location Map Aerial View Topographic Survey Structural Drawings Table 28: Projected Sea-Level Rise (in feet) Datum for Newport Bay Entrance Figure 3.1 Figure 3.2 California Flood Risk: Newport Beach OE S Quadrangle FEMA Flood Risk F.F.=10.90 T/SLAB=10.78 PAD=__.__ POOL WF CONSTRUCTION NOTES DISPOSITION NOTES DISPOSITION NOTES 1 3 9 A v e n i d a N a v a r r o San Cle m en te , CA 92672 9 4 9 .4 9 2 .8 5 8 6 www.toalengineering.com C I V I L EN G I NE ER I NG L A N D S U R V E Y I N G STORMWATER QUALITY ADAM L. TOAL R.C.E. 59275 DATE: LEGEND SCOPE OF WORK ADDITIONAL NOTES EASEMENT NOTESCITY OF NEWPORT BEACH NOTES BENCHMARK NOTE: OCSBM 3K-24A-82 ELEV=19.353 NAVD88 DATUM, 2015 ADJ. EASEMENT NOTE: ALL EASEMENTS SHOWN ON THIS TOPOGRAPHIC AND BOUNDARY SURVEY ARE PER A PRELIMINARY TITLE REPORT PREPARED BY LAWYERS TITLE COMPANY, ORDER NO. FLNP-0062200998GH DATED AUGUST 18, 2022 UNLESS NOTED OTHERWISE. 7 ITEM 7 OF THE PRELIMINARY TITLE REPORT, AN EASEMENT FOR AVIGATION RIGHTS RECORDED IN BOOK 6965, PAGE 721 O.R. IS BLANKET IN NATURE AND NOT PLOTTED HEREON. 8 ITEM 8 OF THE PRELIMINARY TITLE REPORT, EASEMENTS FOR WALKWAY, PARKING AND PLANTER PURPOSES RECORDED IN BOOK 8938, PAGE 91 AND RE-RECORDED IN BOOK 9224, PAGE 1, BOTH O.R. PROPERTY IS NOW OWNED IN FEE TITLE AND THE EASEMENTS ARE NO LONGER IN EFFECT. AN EASEMENT FOR PRIVATE PIER CONSTRUCTION AND MAINTENANCE, AND FLOAT IN, UNDER AND ACROSS A PORTION OF LOT A, TRACT 4003 PLOTTED HEREON. 9 ITEM 9 OF THE PRELIMINARY TITLE REPORT, EASEMENTS FOR UTILITY PURPOSES LISTED WITHIN THE CC&R'S RECORDED IN BOOK 9771, PAGE 488 O.R. HAVE NO SPECIFIC LOCATION AND ARE NOT PLOTTED HEREON. EASEMENTS FOR WALKWAY, PARKING AND PLANTER PURPOSES LISTED IN THE SAME DOCUMENT ARE PLOTTED HEREON. 10 ITEM 10 OF THE PRELIMINARY TITLE REPORT, EASEMENTS FOR UTILITY, DRAINAGE, MAINTENANCE AND OTHER PURPOSES RECORDED IN BOOK 12956, PAGE 910 O.R. ARE NOT PLOTTED HEREON, THE COPY OF THE RECORDED DOCUMENT IS ILLEGIBLE. THE EASEMENTS MAY BE COLLINEAR WITH OTHER EASEMENTS LIST IN THE PRELIMINARY TITLE REPORT. A PARCEL B OF THE LEGAL DESCRIPTION IN THE PRELIMINARY TITLE REPORT, AN EASEMENT FOR PRIVATE PIER CONSTRUCTION AND MAINTENANCE, AND FLOAT IN, UNDER AND ACROSS A PORTION OF LOT A, TRACT 4003 JOB NO.SHEET 1 3 9 A v e n i d a N a v a r r o S a n C le me n t e , C A 9 2 6 7 2 9 4 9 .4 9 2 .8 5 8 6 w w w.to ale n g i n ee rin g .co m C I V I L E N G I N E E R I N G L A N D S U R V E Y I N G ST ORMWATE R Q UA LI TY OF PREPARED FOR: AP V D . DA T E R E V I S I O N S BY DA T E APPD.: DATE: DWG. NO. H. SCALE: V. SCALE:SURVEY DATE: CHD.: DRN.: STEVE HORTON S T A TE OF CA L I F OR NIA LICE N S E D LAND SU R V E Y ORVIKTOR P. MEUM No. 8682 VIKTOR P. MEUM P.L.S. 8682 DATE: 1/8"=1' -2-16-22 3-1-22 MSF - VM 22021 1 1 TP-01 LO T 7 6 , T R A C T 4 0 0 3 , A P N 0 5 0 - 4 5 1 - 3 5 76 L I N D A I S L E , N E W P O R T B E A C H , C A L I F O R N I A TO P O G R A P H I C A N D B O U N D A R Y S U R V E Y SCALE: 1/8"=1' SECTION PLAN * * TABLE 28: Projected Sea-Level Rise (in feet) for Los Angeles Probabilistic projections for the height of sea-level rise shown below, along with the H++ scenario (depicted in blue in the far right column), as seen in the Rising Seas Report. The H++ projection is a single scenario and does not have an associated likelihood of occurrence as do the probabilistic projections. Probabilistic projections are with respect to a baseline of the year 2000, or more specifically the average relative sea level over 1991 - 2009. High emissions represents RCP 8.5; low emissions represents RCP 2.6. Recommended projections for use in low, medium-high and extreme risk aversion decisions are outlined in blue boxes below. Probabilistic Projections (in feet) (based on Kopp et al. 2014) MEDIAN LIKELY RANGE 1-IN-20 CHANCE 1-IN-200 CHANCE 50% probability sea-level rise meets or exceeds… 66% probability sea-level rise is between… 5% probability sea-level rise meets or exceeds… 0.5% probability sea-level rise meets or exceeds… H++ scenario (Sweet et al. 2017) *Single scenario Low Risk Aversion Medium - High Risk Aversion Extreme Risk Aversion High emissions 2030 0.3 0.2 -0.5 0.6 0.7 1.0 2040 0.5 0.4 -0.7 0.9 1.2 1.7 2050 0.7 0.5 -1.0 1.2 1.8 2.6 Low emissions 2060 0.8 0.5 -1.1 1.4 2.2 High emissions 2060 1.0 0.7 -1.3 1.7 2.5 3.7 Low emissions 2070 0.9 0.6 -1.3 1.8 2.9 High emissions 2070 1.2 0.8 -1.7 2.2 3.3 5.0 Low emissions 2080 1.0 0.6 -1.6 2.1 3.6 High emissions 2080 1.5 1.0 -2.2 2.8 4.3 6.4 Low emissions 2090 1.2 0.7 -1.8 2.5 4.5 High emissions 2090 1.8 1.2 -2.7 3.4 5.3 8.0 Low emissions 2100 1.3 0.7 -2.1 3.0 5.4 High emissions 2100 2.2 1.3 -3.2 4.1 6.7 9.9 Low emissions 2110* 1.4 0.9 -2.2 3.1 6.0 High emissions 2110* 2.3 1.6 -3.3 4.3 7.1 11.5 Low emissions 2120 1.5 0.9 -2.5 3.6 7.1 High emissions 2120 2.7 1.8 -3.8 5.0 8.3 13.8 Low emissions 2130 1.7 0.9 -2.8 4.0 8.1 High emissions 2130 3.0 2.0 -4.3 5.7 9.7 16.1 Low emissions 2140 1.8 0.9 -3.0 4.5 9.2 High emissions 2140 3.3 2.2 -4.9 6.5 11.1 18.7 Low emissions 2150 1.9 0.9 -3.3 5.1 10.6 High emissions 2150 3.7 2.4 -5.4 7.3 12.7 21.5 S T A T E O F C A L I F O R N I A S E A - L E V E L R I S E G U I D A N C E *Most of the available climate model experiments do not extend beyond 2100. The resulting reduction in model availability causes a small dip in projections between 2100 and 2110, as well as a shift in uncertainty estimates (see Kopp et al. 2014). Use of 2110 projections should be done with caution and with acknowledgement of increased uncertainty around these projections. A P P E N D I X 3 : S E A - L E V E L R I S E P R O J E C T I O N S F O R A L L 1 2 T I D E G A U G E S | 7 2 Newport BeachNewport Beach Costa MesaCosta MesaCosta MesaCosta MesaHuntington BeachHuntington Beach ¬«1 ¬«55 ¬«1 ¬«55 117°52’30"W 117°52’30"W 117°55’0"W 117°55’0"W 117°57’30"W 117°57’30"W 118°0’0"W 118°0’0"W 33°37’30"N 33°37’30"N 33°35’0"N 33°35’0"N 33°32’30"N 33°32’30"N 33°30’0"N 33°30’0"N 407000mE 407000mE 08 08 09 09 410 410 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 419000mE 419000mE 37 07 00 0 m N 37 07 00 0 m N 08 08 09 09 3710 3710 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 3720 3720 37 21 00 0 m N 37 21 00 0 m N This information is being made available for informational purposes only. Users of this information agree by their use to hold blameless the State of California, and its respective officers, employees, agents, contractors, and subcontractors for any liability associated with its use in any form. This work shall not be used to assess actual coastal hazards, insurance requirements, or property values and specifically shall not be used in lieu of Flood Insurance Studies and Flood Insurance Rate Maps issued by the Federal Emergency Management Agency (FEMA). Data Sources: US Geological Survey, Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal ServicesCenter (CSC), Scripps Institution of Oceanography, Phillip WIlliams and Associates, Inc. (PWA), US Department of Agriculture (USDA), California Coastal Commission, and National Aeronautics and Space Administration (NASA). Imagery from ESRI and i-cubed. Created by the Pacific Institute, Oakland, California, 2009. California Flood Risk: Sea Level Rise 00.511.520.25 Miles 01230.5 Kilometers 1: 2: 3: 4: 5: 6: 7: 8: Seal Beach Newport Beach Tustin not printed Laguna Beach not printed not printed not printed867 1 2 3 54 §¨¦ £¤ ") ¬« Interstate US Highway State Highway County Highway Grid coordinates: UTM Zone 11N meters Adjoining Quadrangles: Map extents match USGS 7.5 minute topographic maps Project funded by the California Energy Commission’s Public Interest Energy Research Program, CalTrans, and the California Ocean Protection Council Newport Beach OE S Quadrangle NAD83 GCS degrees Coastal Zone Boundary Current Coastal Base Flood (approximate 100-year flood extent) Sea Level Rise Scenario Coastal Base Flood + 1.4 meters (55 inches) Landward Limit of Erosion High Hazard Zone in 2100 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREENArea of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 3/15/2022 at 4:48 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location. 1:6,000 117°54'27"W 33°37'7"N 117°53'50"W 33°36'37"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020