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HomeMy WebLinkAboutPA2021-130_20210908_Coastal Hazards ReportGeoSoils Inc. 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 May 30, 2021 Mr. & Mrs. Beard 3208 Ocean Blvd Corona del Mar, CA 92625 Subject: Discussion of Coastal Hazards and Wave Runup, 3625 Ocean Blvd, Corona del Mar, Newport Beach, Orange County, California Dear Mr. & Mrs. Beard: At your request and authorization, we are pleased to present the following report describing the coastal hazards and wave runup at 3625 Ocean Blvd, Corona del Mar. The analysis is based upon our site inspection, existing published reports concerning the local coastal processes, site elevations, the proposed development, and our knowledge of local coastal conditions. This report constitutes an investigation of the wave and water level conditions expected at the site in consequence of extreme storm, wave action, and future sea level rise (SLR). The purpose of this report is to provide the necessary coastal engineering information to the City of Newport Beach City (Newport Beach Municipal Code (NBMC) 21.30.15.E.2) and the California Coastal Commission (CCC) in support of the proposed project. It provides conclusions and recommendations for the susceptibility to and protection of the site from wave attack, shoreline erosion, and flooding. SCOPE OF SERVICES 1.Review of available site oceanographic reports, including the recent Coast of California Storm and Tidal Wave Study (CCSTWS) US Army Corps of Engineers (USACOE) report(s), review of California Coastal Commission (CCC) Sea-Level Rise Policy Guidance (November 2018), and discussions with project designer. 2.Research of historical aerial photographs of the site, and use of historical aerial photographs to determine historical shoreline changes. 3.Perform a site reconnaissance to inspect the condition of the site and assess the general condition of the shoreline. 4.Engineering analysis and preparation of this report that includes a review of the available oceanographic information, a discussion of past and future erosion rates, and calculation of wave runup. GeoSoils Inc.2 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 SITE VISIT The shoreline fronting the site was inspected on May 26, 2021 by GSI personnel. Photograph 1 is a “Birds Eye” aerial photograph downloaded from the internet. The site visit/inspection focused on the bluff, the present shoreline conditions, and site geology. The seaward portion of the site is located at and above a bedrock wave cut shore platform. There is typically only a rock beach below the site. The shoreline along this stretch of beach has bedrock outcroppings in the surf zone and rocky headlands, which is typical of the Corona del Mar nearshore area. The site elevations vary from about +12 feet NAVD88 near the base of the bluff to about elevation +100 feet NAVD88 at Ocean Blvd. The proposed development is removal of the existing residence and construction of a new residence. The lowest proposed finished floor (FF) elevation is at about +66 feet NAVD88. The back beach bluff consists of a very erosion resistant bedrock material bluff (Monterey Formation), with the visible bluff toe at about elevation +13 feet NAVD88, as seen in Photograph 1. Photograph 1. Subject site in 2020 and adjacent properties. Note the exposed bedrock (Monterey Formation) at the back of the beach and in the surf zone. The white arrow points to a bedrock block topple that will be discussed further in this report. GeoSoils Inc.3 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 COASTAL PROCESSES The shoreline to the west of the site, locally called Big Corona Beach, and the site lie within the Laguna Beach Mini Littoral Cells, one of the eight coastal segments defined and studied in the US Army Corps of Engineers Coast of California Storm and Tidal Wave Study South Coast Region Orange County (USACOE, 2002). A littoral cell is a coastal compartment that contains a complete cycle of littoral sedimentation including sources, transport pathways, and sediment sinks. The term mini littoral cell is used by the Corps to describe the small but discrete coastal compartments along this section of southern California shoreline. The Laguna Beach Mini Littoral Cells extend from the west jetty of Newport Harbor to the Dana Headlands, a distance of about 14.1 miles. This shoreline is characterized by a series of small, and probably conservative, pocket beaches. The pocket beaches are characteristically narrow and backed by sea cliffs composed of erosion resistant bedrock below more erosive formations. The pocket beach size varies with wave conditions and shoreline orientation but the mean beach widths have been relatively stable (USACOE, 2002). The pocket beaches are bounded by either rock noses extending into the surf zone or natural headland reefs. The pocket beaches are subject to seasonal erosion and accretion but are, in general, quasi stable. The Corps report provides a comprehensive investigation of the shoreline conditions, past and present (2002), for southern Orange County and some site specific information about the Big Corona Beach shoreline area. The shoreline fronting the properties is located to the east of the east jetty at the entrance to Newport Bay. The Big Corona Beach to the west of the site is about 0.6 miles long and maintains an average width of about 200 feet. The shoreline in this area of Corona del Mar has been nourished and stabilized by man. The beach to the west of the site was primarily made by man as a result of the construction of Newport Bay jetties and associated beach nourishment. The south jetty at the entrance of the bay acts to hold the beach in place, while the pair of jetties shelter the area from wave energy from the north and the west. The rocky headland just to the west of the site forms the eastern boundary of the pocket beach. In front of the site is a rocky beach composed of the erosion resistant Monterey Formation bedrock. There is little, if any, up-coast and down-coast movement of this material along the shoreline. The project geotechnical consultant, Coast Geotechnical, Inc. (CGI), determined that there has been little if any historic bluff retreat at the site based upon a review of historical aerial photographs. The US Army Corps of Engineers Los Angeles District completed the Orange County element of the Coast of California Storm and Tidal Wave Study in 2002. The report specifically identifies the shoreline fronting the site and nearby beach (Big Corona Beach) as stable. Everts Coastal performed a study for the City of Newport Beach (USACOE,2002) which also determined that the nearby beach and shoreline fronting the site are stable. Photographs 2a and 2b, downloaded from the Coastal Records Project website show the site in 1972 and 2013, respectively. There is no observable difference in the bluff face and back beach between the photos. GeoSoils Inc.4 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Photograph 2a. The subject site, adjacent properties in 1972. Note the presence of the Monterey Formation and that the beach and bluff are about same as in Photograph 2b. Photograph 2b. The subject site, adjacent properties in 2013. Note the presence of the Monterey Formation and that the beach and bluff are about same as in Photograph 2a. GeoSoils Inc.5 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 WAVES & WATER LEVELS Waves of all periods approach the site shoreline. Almost all of the energy is contained in the medium and long period waves (approximately 5 to 20 seconds), however. These waves approach the Southern California Bight and encounter the offshore islands. The offshore islands such as Santa Cruz, Santa Rosa, Santa Catalina and San Clemente partially shelter this section of coast from ocean swells. Between these islands are the windows that waves can pass through and approach the site shoreline. Waves can approach the study area through wave windows from the west and northwest and from the south. However, due to the sheltering effect of the shoreline geometry, the predominant wave energy arrives to the site from the south. Wave conditions in the site area have been thoroughly investigated by the USACOE and others. As waves travel into shallower and shallower water, the wave crest is bent and becomes nearly parallel to shore, and the wave heights are modified depending on whether waves are being focused or de-focused at a particular location along the shoreline. This process is called refraction and it is dependent upon the bathymetry, the wave height, period, and direction. Extreme wave conditions in shallow water have been calculated using historical wave data. The California Department of Boating and Waterways in partnership with the USACOE maintain wave recording buoys throughout Southern California. The record of historical waves for this region, both from direct observation or recording and from hindcast analysis, is very extensive. The National Oceanographic and Atmospheric (NOAA) National Ocean Survey tidal data station closest to the site with a long tidal record is located at Los Angeles Harbor (Station 94106600). The tidal datum elevations are as follows: Mean High Water 4.55 feet Mean Tide Level (MSL) 2.62 feet Mean Low Water 0.74 feet NAVD88 0.0 feet Mean Lower Low Water -0.2 feet During storm conditions, the sea surface rises along the shoreline (super-elevation) and allows waves to break closer to the shoreline and runup on the beach. Super-elevation of the sea surface can be accounted for by: wave set-up, wind set-up and inverse barometer, wave group effects and El Niño sea level effects. The historical highest ocean water elevation at the Los Angeles Harbor Tide station is +7.72 feet NAVD88 on January 10, 2005. In addition, EICI reported that the elevation of 7.71 feet NAVD88 is the 1% water elevation. For this analysis the historical highest water elevation will be +7.7 feet NAVD88.). GeoSoils Inc.6 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 OCEANOGRAPHIC DESIGN PARAMETERS There are several factors that are important to the analysis of the vulnerability of a development along the shoreline. Some of the factors are based upon the existing topography/bathymetry and elevation of the existing and proposed structures at the site. The offshore slope is relatively steep at 1/50 (V/H). The visible base of the bedrock bluff is at about elevation +12 feet NAVD88. Other factors are based upon extreme oceanographic conditions, or the coincidence of several extreme conditions. In order to determine design wave characteristics for the runup and force analysis, it is necessary to determine the design water level. The design water level will need to account for the expected future rise in sea level over the life of the structure in accordance with the CCC Sea-Level Rise Policy Guidance document. Sea Level Rise The California Coastal Commission (CCC) SLR Guidance document recommends that a project designer determine the range of SLR using the “best available science.”The California Ocean Protection Council (COPC) adopted an update to the State’s Sea-Level Rise Guidance in March 2018. These new estimates are based upon a 2014 report entitled “Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites” (Kopp et al., 2014). This update included SLR estimates and probabilities for Los Angeles Harbor the closest SLR estimates to Newport Beach. These SLR likelihood estimates are provided below in Figure 1 taken from the Kopp et al., 2014 report. The report provides SLR estimates based upon various carbon emission scenarios known as a “representative concentration pathway” or RCP. Figure 1 provides the March 2018 COPC data (from the Kopp et al., 2014 report) with the latest SLR adopted estimates (in feet) and the probabilities of those estimate to meet or exceed the 1991-2009 mean, based upon the best available science. GeoSoils Inc.7 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Figure 1. Table from Kopp et al., (2014) and COPC 2018, providing current SLR estimates and probabilities for the Los Angeles Harbor tide station. This table illustrates that SLR in the year 2100 for the likely range, and considering the most onerous RCP (8.5), is 1.3 feet to 3.2 feet above the 1991-2009 mean. The CCC requires the consideration of the low probability (0.5%) high emissions SLR over the next 75 years. The 0.5% SLR in the year 2096 is about 6 feet of SLR. The Kopp et al. paper used 2009 to 2012 SLR modeling for the probability analysis, which means the “best available science” as determined by the CCC is almost 10 years old. The CCC SLR Guidance requires the use of the “best available science.” Dr. Reinhard Flick from the Scripps Institution of Oceanography has provided information that global sea level from 1992 to 2018 has resulted in 8.32 centimeters of relatively uniform SLR in the past 26 years. This information is shown on Figure 2 taken from the CCC SLR Guidance (2015). This current measurement shows that SLR is tracking more on the intermediate SLR prediction curves, which is more like a 50% (median) probability SLR in the year 2100, as shown in Figure 2. GeoSoils Inc.8 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Figure 2. Recent global SLR plotted on SLR prediction curves (graphic taken from TerraCosta Consulting). The recent global SLR measurement provided in Figure 2 shows that the current SLR trend, is not following the higher SLR estimate curves. It is GSI’s professional opinion that the methodology and SLR estimates suggested by the CCC SLR Guidance, based upon current SLR trends, are an overestimate of SLR over the project design life of 75 years. The “design life” of the project is 75 years. Figure 1 illustrates that SLR in the year 2100 for the likely range, and using the most onerous RCP (8.5), is 1.8 feet to 3.6 feet above the 1991-2009 mean. This can be interpolated to be a maximum of about 3.4 feet over the next 75 years. Based upon this 2017 COPC SLR report, the maximum “likely” SLR for the project is estimated to be 3.4 feet. There is also a 0.5% chance the sea level rise will be about 6.0 feet in 75 years. The maximum historical water elevation in the site area is elevation ~+7.7 feet NAVD88. This actual high water record period includes the 1982-83 severe El Niño, and the 1997 El Niño events, and is therefore consistent with the methodology outlined in the CCC Sea-Level Rise Policy Guidance document. If 3.4 feet and 6.0 feet are added to this 7.7 feet NAVD88 elevation, then future design maximum water levels of 11.1 feet NAVD88 and 13.7 feet NAVD88 will result. GeoSoils Inc.9 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Determination of the maximum scour depth at the toe of the bluff enables the engineer to determine the actual water depth at the toe of the bluff and wave break point under the design water level conditions. The design scour elevation is estimated based upon the erodability of the materials at the toe of the beach. Based upon the elevation of the bedrock at the base of the slope, a conservative estimate of the scour elevation at the toe of the beach in 75 years is about +4.7 feet to +5 feet NAVD88. This is reasonable based upon the presence of visible bedrock at the shoreline. It also assumes that all other littoral material is entirely gone. Using the maximum still water elevation and the maximum scour yields a total water depth of 6.5 feet and 9 feet at the slope toe for the two SLR cases. These values represent the range of extreme possible wave runup conditions reaching the site over the next 75 years and will be used in the design analysis. As discussed above, waves from distant storms and nearby hurricanes (chubascos) have pounded the coastline of Corona del Mar several times within the last few centuries. However, these extreme waves break further offshore and lose a significant portion of their energy before they reach the shoreline. The relatively steep offshore area allows for energy from large waves to come relatively close to the shoreline. Once a wave reaches a water depth that is about 1.28 times the wave height, the wave breaks and runs up onto the shore. The design wave height at the toe of the beach is the maximum unbroken wave at the slope toe when the beach/bedrock is at the maximum scour condition(the beach is gone). The total water depth is 6.5 feet and 9 feet which would yield design wave heights of 5 feet and 7 feet. WAVE RUNUP AND OVERTOPPING ANALYSIS As waves approach the shoreline and the site, they break and water rushes up the back beach area to the bluff. Wave runup is defined as the vertical height above the still water level to which a wave will rise on a structure (the bluff) of infinite height. Overtopping is the flow rate of water over the top of the bluff (about elevation +55 feet NAVD88) as a result of wave runup. Wave runup and overtopping at the proposed structure is calculated using the USACOE Automated Coastal Engineering System (ACES). The methods to calculate runup and overtopping implemented within this ACES application are discussed in greater detail in the Coastal Engineering Manual (2004). The overtopping estimates calculated herein are corrected for the effect of onshore winds. Figure 3 from the ACES manual shows some of the variables involved in the runup and overtopping analysis. Table I and Table II below are the output for of the two SLR cases. GeoSoils Inc.10 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Figure 3. Wave runup terms from ACES analysis. TABLE I TABLE II GeoSoils Inc.11 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 The runup analysis shows that, with the beach gone and 3.4 feet of SLR in the next 75 years, the maximum wave runup is to elevation ~+21 feet NAVD88 (11.1 feet NAVD88 + 9.8 feet). For 6.0 feet of SLR in the next 75 years the maximum wave runup elevation is ~+27 feet NAVD88 (13.7 feet NAVD88 + 13.4 feet). Under both cases the wave runup will not reach top of the bluff at about +55 feet NAVD88. HAZARD ANALYSIS There are three different potential oceanographic hazards identified at this site; shoreline erosion, coastal flooding, and waves. For ease of review each of these hazards will be analyzed and discussed separately followed by a summary of the analysis including conclusions and recommendations, if necessary. Erosion Hazard In an effort to determine typical changes in the bluff position aerial photographs from the early 1940s to 2020 were reviewed. Due to the differences in tide levels and oblique angles of the photos, it is difficult to determine the exact location of the bluff toe. However, a visual comparison of the photographs shows little or no change in the shoreline position and the bluff over the last five decades. The bedrock beach is visible in the 1972 Coastal Records photograph (Photograph 2a) and is visible with about the same width in all subsequent photographs. The future shoreline changes over the next 75 years can be assumed to be the same as in the previous seven decades. This conclusion is also verified in the 2002 USACOE report and in the CGI report. Sea level rise alone will not change the erosion rate of the shoreline. The erosion rate of the shoreline is dependent upon waves and currents which are independent of SLR. The current erosion rate of the bluff based upon historical aerial photographs is about 0.0 ft/yr. To predict how future sea level rise, of any magnitude, will change the erosion rate of the bedrock at the back of the beach is not as difficult as one may think. Let us assume that sea level rises 6 feet over the next 75 years (0.5% sea level rise), most of this rise will occur from the year 2045 to the year 2096. Under this future sea level elevation, it is easy to predict the that wave action will continuously act higher on the sea cliff. Photograph 3 was taken on May 4, 1949 and downloaded from the UCSB Aerial Photograph Collection. Photograph 4 was taken in 2020 and was downloaded from Google Earth. Although the elevation, sun, and angle of the photographs is slightly different, visual comparison of these photos taken over seven decades apart verifies that there is little, if any, historical bluff erosion occurring at the site. The photographs have been annotated for reader comparison. GeoSoils Inc.12 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Area A.This is a bedrock point to the west of the site with 2 large outcroppings that are essentially unchanged over the 71-year period between the photographs. Area B.This is a bedrock block topple that has changed very little over the 71-year time period. It is also denoted in Photograph 1. Area C.These are bedrock surge channels that are in the surf zone that have not changed over the 71 year period between the photographs Photograph 3. The picture was taken in 1949 fronting the site in Corona del Mar. Photograph 4. The picture was taken in 2020 at the site in Corona del Mar. GeoSoils Inc.13 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Flooding Hazard The flooding hazard discussed in this section is due to water level changes in the ocean. The primary threat of flooding from ocean waters would be due to a super-elevation of the ocean. The NOAA Ocean Survey tidal data station closest to the site is located at the Los Angeles Harbor station (NOAA, 2021). The elevations relative to NAVD88 are provided on page 5 of this report. Allowing for a 6 feet rise in sea level over the next 75 years, the mean higher high water level will be at +11.25 feet NAVD88. The highest observed water level was on January 28, 1983 during the severe El Niño winter. This elevation was +7.5 feet NAVD88. If a sea level rise of 6 feet is added to this elevation, it is about +13.5 feet NAVD88. This would be considered in excess of a 75-year recurrence interval water level. The proposed site improvements are above +55 feet NAVD88, which are well above any potential ocean flood elevation. The site improvements are safe from flooding from the ocean over the next 75 years. Potential flooding associated with wave runup is considered in the next section. Wave Runup Wave runup will reach the bluff over the next 75 years. However, due to the elevation of the improvements (above +55 feet NAVD88), the wave runup will not impact the improvements. Essentially, the erosion resistant bedrock at the site offers natural shore protection, and will prevent further movement of the shoreline landward even under the highest SLR estimate over the next 75 years. Tsunami Tsunami are waves generated by submarine earthquakes, landslides, or volcanic action. It should be noted that the site development is mapped beyond the landward limit of the California Office of Emergency Services (CalOES) tsunami innundation map, Laguna Beach Quadrangle (State of California, 2009). The tsunami inundation maps are very specific as to their use. Their use is for evacuation planning only. The limitation on the use of the maps is clearly stated in the PURPOSE OF THIS MAP on every quadrangle of California coastline. In addition, the following two paragraphs were taken from the CalOES Local Planning Guidance on Tsunami Response concerning the use of the tsunami inundation maps. In order to avoid the conflict over tsunami origin, inundation projections are based on worst-case scenarios. Since the inundation projections are intended for emergency and evacuation planning, flooding is based on the highest projection GeoSoils Inc.14 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 of inundation regardless of the tsunami origin. As such, projections are not an assessment of the probability of reaching the projected height (probabilistic hazard assessment) but only a planning tool. Inundation projections and resulting planning maps are to be used for emergency planning purposes only. They are not based on a specific earthquake and tsunami. Areas actually inundated by a specific tsunami can vary from those predicted. The inundation maps are not a prediction of the performance, in an earthquake or tsunami, of any structure within or outside of the projected inundation area. Due to the infrequent nature and the relatively low 500-year recurrence interval tsunami wave height, and the elevation of the improvements, the development is safe from tsunami hazards. SLR & 100 YEAR STORM The USGS has also developed a model called the Coastal Storm Modeling System (CoSMoS) for assessment of the vulnerability of coastal areas to SLR and the 100 year storm, http://walrus.wr.usgs.gov/coastal_processes/cosmos/. Using the modeling program the vulnerability of the site to different SLR scenarios and the100 year storm, including shoreline erosion, can be assessed. However, the following are the limitations as to the use of the CoSMoS model. Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. The U.S. Geological Survey provides these data “as is” for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information. Figure 4 is the output of the CoSMoS program. The modeling shows that the wave runup does not reach the proposed site improvement during the 100 year event with 175 cm (~5.7 feet) of SLR. GeoSoils Inc.15 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Figure 4. CoSMoS wave runup output for the site with 5.7 (175 CM) feet SLR. CITY OF NEWPORT BEACH INFORMATION Coastal Hazards Report (NBMC 21.30.15.E.2): i. A statement of the preparer’s qualifications; Mr. Skelly is Vice President and Principal Engineer for GeoSoils, Inc. (GSI). He has worked with GSI for several decades on numerous land development projects throughout California. Mr. Skelly has over 40 years experience in coastal engineering. Prior to joining the GSI team, he worked as a research engineer at the Center for Coastal Studies at Scripps Institution of Oceanography for 17 years. During his tenure at Scripps, Mr. Skelly worked on coastal erosion problems throughout the world. He has written numerous technical reports and published papers on these projects. He was a co-author of a major Coast of California Storm and Tidal Wave Study report. He has extensive experience with coastal processes in southern California. Mr. Skelly also performs wave shoring and uprush analysis for coastal development, and analyzes coastal processes, wave forces, water elevation, longshore transport of sand, and coastal erosion. ii. Identification of costal hazards affecting the site; As stated in this hazard analysis, the typical coastal hazards to consider GeoSoils Inc.16 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 are shoreline erosion, flooding, and wave impacts. The site is fronted by a bedrock shoreline and bluff, which is very erosion resistant. Extreme ocean waves at high tide, including SLR, can runup on the bluff but cannot reach the elevation of the development. There is no potential coastal hazard of flooding of the development due to the elevation of the improvements. iii. An analysis of the following conditions: 1. A seasonally eroded beach combined with long-term (75 year) erosion factoring in sea level rise; There is a stable rock shoreline at the site. The bedrock, even when in the surf zone doesn’t eroded easily. There are no seasonal changes in the beach and even in consideration of SLR there will be no seasonal changes. . 2. High tide conditions, combined with long-term (75 year) projections for sea level rise; Using the likely CCC SLR estimate over the project 75-year design life, the SLR in the year ~2096 is 3.4 feet. There is a 0.5% probability that SLR could be 6 feet in the next 75 years. This is the design sea level rise range (3.2 feet to 6 feet) for the proposed project. This SLR would account for future extreme bay water level of 11.1 feet NAVD88 to 13.7 feet NAVD88. 3. Storm waves from a one hundred year event or storm that compares to the 1982/83 El Nino event; Wave runup will not reach the site improvements over the project design life. 4. An analysis of bluff stability; a quantitative slope stability analysis that shows either that the bluff currently possesses a factor of safety against sliding of all least 1.5 under static conditions, and 1.1 under seismic (pseudostatic conditions); or the distance from the bluff edge needed to achieve these factors of safety; and This information is provided by the project geotechnical consultant, Coast Geotechnical, Inc. GeoSoils Inc.17 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 5. Demonstration that development will be sited such that it maintains a factor of safety against sliding of at least 1.5 under static conditions and 1.1 under seismic (pseudostatic) conditions for its economic life (generally 75 years). This generally means that the setback necessary to achieve a factor of safety of 1.5 (static) and 1.1 (pseudostatic) today must be added to the expected amount of bluff erosion over the economic life of the development (generally 75 years); This information is provided by the project geotechnical consultant, Coast Geotechnical, Inc. iv. On sites with an existing bulkhead, a determination as to whether the existing bulkhead can be removed and/or the existing or a replacement bulkhead is required to protect existing principal structures and adjacent development or public facilities on the site or in the surrounding areas; and There is no bulkhead on the site. v. Identification of necessary mitigation measures to address current hazardous conditions such as siting development away from hazardous areas and elevating the finished floor of structures to be at or above the base floor elevation including measures that may be required in the future to address increased erosion and flooding due to sea level rise such as waterproofing, flood shields, watertight doors, moveable floodwalls, partitions, water-resistive sealant devices, sandbagging and other similar flood-proofing techniques. There are no mitigation measures necessary to address coastal hazards CALIFORNIA COASTAL COMMISSION SLR POLICY GUIDANCE INFORMATION Step 1. Establish the projected sea level rise range for the proposed project’s planning horizon using the best available science, which is COPC 2018 report. Using the CCC SLR estimate, over the project design life, the range in the year ~2096 is between 3.4 feet and 6.0 feet. This is the projected sea level rise range for the proposed project. GeoSoils Inc.18 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 Step 2. Determine how physical impacts from sea level rise may constrain the project site, including erosion, structural and geologic stability, flooding, and inundation. The analysis herein shows that it is very unlikely that wave runup will reach the development, even with over 6.0 feet of SLR. The bedrock fronting the site is very stable. The project is reasonably safe from shoreline erosion due to the erosion resistant bedrock material. Step 3. Determine how the project may impact coastal resources, considering the influence of future sea level rise upon the landscape as well as potential impacts of sea level rise adaptation strategies that may be used over the lifetime of the project. The project will not impact coastal resources in consideration of sea level rise. Step 4. Identify alternatives to avoid resource impacts and minimize risks throughout the expected life of the development. The project does not impact resources, and minimizes flood risk through the project design. Step 5. Finalize project design and submit CDP application. The project architect will incorporate this report in the project design. CONCLUSIONS The potential coastal hazards associated with the development at 3625 Ocean Blvd, Corona del Mar, Newport Beach, include shoreline erosion, wave runup, and future SLR. As demonstrated in USACOE 2002 the shoreline fronting the site is stable over the long term. During the coincidence of high tides and high waves, the bluff fronting the bluff will be subject to wave runup. However, based upon our analysis, and because the proposed development is located well above the base of the bluff, the development is safe from coastal hazards. It should also be noted that there is a bedrock at the back of the beach that acts like natural shore protection. The bedrock protects the site from waves and erosion. Therefore, there are no recommendations necessary to mitigate potential coastal hazards. New shore protection will not be required to protect the development over the next 75 years. The development neither creates nor contributes significantly to erosion, geologic instability, or destruction of the site or adjacent area. GeoSoils Inc. 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 LIMITATIONS Coastal engineering is characterized by uncertainty. Professional judgements presented herein are based partly on our evaluation of the technical information gathered, partly on our understanding of the proposed construction, and partly on our general experience. Our engineering work and judgements have been prepared in accordance with current accepted standards of engineering practice. We do not guarantee the performance of the project in any respect. This warranty is in lieu of all other warranties express or implied. Respectfully submitted, GeoSoils, Inc. David W. Skelly MS RCE#47857 GeoSoils Inc.20 5741 Palmer Way, Suite D, Carlsbad CA 92010 Phone 760-438-3155 REFERENCES Coastal Engineering Manual 2004, US Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, US Government Printing Office, Washington, DC. Coast Geotechnical, Inc., 2021, “ Geotechnical and Geologic Investigation of Proposed New Residence at 3625 Ocean Boulevard Newport Beach, California, dated May 27. Dean, Robert, 1991,“Equilibrium Beach Profiles: Characteristics and Applications,” date Winter 1991, Journal of Coastal Research, 7-1 pages 53-94 James R. Houston, 1980, “Type 19 Flood Insurance Study: Tsunami Predictions For Southern California,” USACOE Technical Report HL-80-18. Kopp, Robert E., Radley M. Horton Christopher M. Little Jerry X. Mitrovica Michael Oppenheimer D. J. Rasmussen Benjamin H. Strauss Claudia Tebaldi Radley M. Horton Christopher M. Little Jerry X. Mitrovica Michael Oppenheimer D. J. Rasmussen Benjamin H. Strauss Claudia Tebaldi “Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites” First published: 13 June 2014 Legg, Mark R., Borrero, Jose C., and Synolakis, Costas E., Evaluation of tsunami risk to southern California coastal cities, in The 2002 NEHRP Professional Fellowship Report. Moffatt & Nichol, Engineers, 1985, County of Orange, E.M.A., “Coastal Flood Plain Development Study,” January 1985 NOAA, 2021, Web Sites, Maps http://anchor.ncd.noaa.gov/states/ca.htm Tidal Datums http://www.opsd.nos.noaa.gov/cgi-bin/websql/ftp/query_new.pl USACOE (US Army Corps Of Engineers), 1986, "Southern California Coastal Processes Data Summary" Ref # CCSTW 86-1. USACOE (US Army Corps Of Engineers), 2002, Coast of California Storm and Tidal Waves Study South Coast Region, Orange County.