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HomeMy WebLinkAboutMS 2020-0003; HEMLOCK COAST HOMES; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION, HEMLOCK COASTAL HOMES RESIDENTIAL PROJECT, 320 HEMLOCK AVENUE, CARLSBAD, CALIFORNIA; 2020-08-24REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Hemlock Coastal Homes Residential Project . 320 Hemlock Avenue Carlsbad, California JOB NO. 20-12842 24 August 2020 Prepared for: Mr . .John Norum KM.J Real Estate Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 24 August 2020 Mr. John Norum KMJ REAL ESTATE 1446 Front Street, Suite 300 San Diego, CA 92101 Job No. 20-12842 Subject: Report of Preliminary Geotechnical Investigation Hemlock Coastal Homes Residential Project 320 Hemlock Avenue Carlsbad, California Dear Mr. Norum: In accordance with your request and our proposal dated January 29, 2020, Geotechnical Exploration, Inc. has performed an investigation of the geotechnical and general geologic conditions at the subject site. The field work was performed on August 5, 2020. If the conclusions and recommendations presented in this report are incorporated into the design and construction of the proposed development, it is our opinion that the site is suitable for the residential project. This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please do not hesitate to contact us. Reference to our Job No. 20-12842 will expedite a response to your inquiries. Respectfully submitted, Jaime ... 34422/G.E. 2007 Senior Geotechnical Engineer ~6£ C.E.G. 999/P.G. 3391 7420 lRADE STREET• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gei-sd.com TABLE OF CONTENTS I. PROJECT SUMMARY AND SCOPE OF SERVICES .................................. ! II. SITE DESCRIPTION ....................................................................... 2 III. FIELD INVESTIGATION .................................................................. 3 IV. LABORATORY TESTS AND SOIL INFORMATION .................................. 3 V. REGIONAL GEOLOGIC DESCRIPTION ............................................... 5 VI. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION ............................. 10 A. Stratigraphy .............................................................................................................. 10 B. Structure ................................................................................................................... 11 VII. GEOLOGIC HAZARDS .................................................................. 11 VIII. GROUNDWATER ......................................................................... 19 IX. CONCLUSIONS AND RECOMMENDATIONS ...................................... 21 A. Site Soil Preparation and Earthwork ......................................................................... 21 B. Seismic Design Criteria .............................................................................................. 25 C. Design Parameters for Proposed Foundations ......................................................... 25 D. Concrete Slab On-grade Criteria ............................................................................... 28 E. Retaining Wall Design Criteria .................................................................................. 33 F. Site Drainage Considerations .................................................................................... 34 G. General Recommendations ...................................................................................... 35 X. GRADING NOTES ........................................................................ 37 XI. LIMITATIONS ............................................................................. 37 FIGURES I. II. IIIa-d. IV. v. Vicinity Map Plot Plan with Site-Specific Geology Exploratory Excavation Logs with Laboratory Data Laboratory Test Results Geologic Map and Legend REFERENCES APPENDICES A. Unified Soil Classification System B. USGS Site Specific Seismic Design Parameters REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Hemlock Coastal Homes Residential Project 320 Hemlock Avenue Carlsbad, California JOB NO. 20-12842 The following report presents the findings and recommendations of Geotechnica/ Exploration, Inc. for the subject project. I. PROJECT SUMMARY AND SCOPE OF SERVICES It is our understanding, based on a review of preliminary plans for the site prepared by Kirk Moeller Architects, Inc., dated July 27, 2020, that the existing residence and improvements are to be removed, and the property is being developed to receive two 3-story, two-unit residential structures with ground-level garages, driveways, and associated improvements. The new structures are to be constructed of standard- type building materials utilizing conventional foundations with concrete slab on-grade floors. Final construction plans for development have not been provided to us during the preparation of this report, however, when completed they should be made available for our review. The scope of work performed for this investigation included a site reconnaissance and subsurface exploration program, soil laboratory testing, geotechnical engineering analysis of the field and laboratory data, and the preparation of this report. The data obtained and the analyses performed were for the purpose of providing geotechnical design and construction criteria for the project earthwork, building and improvement foundations, and slab on-grade floors. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 2 In our professional opinion the proposed site development will not destabilize or cause settlement to adjacent properties or right of way. II. SITE DESCRIPTION The subject site is known as Assessor's Parcel No. 204-240-40-00, Lot 2 of Block R, Palisades #2, per Recorded Map No. 1803, in the City of Carlsbad, County of San Diego, State of California. Refer to the Vicinity Map, Figure No. I, for site location. The approximately 8,243 square-foot site is located at 320 Hemlock Avenue, in the City of Carlsbad. The property is bordered on the north and east by similar residential properties; on the west by a two-story multi-family residential development; and on the south by Hemlock Avenue. The property currently consists of an existing single-story, single-family residence with a rear yard patio and walkways adjacent to the residence. The existing building pad is at an approximate elevation of 57 feet above mean sea level (MSL). Elevations across the property range from approximately 57 feet MSL in the rear yard to approximately 54 feet MSL at the southwest corner adjacent to Hemlock Avenue. Information concerning approximate elevations across the site was obtained from a Topographic Survey Map prepared by Pasco Laret Suiter, dated August 5, 2020. Refer to the Plot Plan and Topographic Survey with Site-Specific Geology, Figure No. II. Existing vegetation on the site consists primarily of lawn grass, mature trees and ornamental shrubbery. Hemlock Coastal Homes Residential Project Carlsbad, California III. FIELD INVESTIGATION Job No. 20-12842 Page 3 The field investigation consisted of a surface reconnaissance and a subsurface exploration program utilizing hand tools and a hand-auger to investigate and sample the subsurface soils. Four exploratory hand pit excavations (HP-1 through HP-4) were advanced on August 5, 2020 to depths ranging from 4.25 to 5.5 feet where the proposed residential structures and improvements are to be located and access was available. The location of the proposed structures and approximate locations of the exploratory excavations are shown on the Plot Plan, Figure No. II. The soils encountered in the exploratory excavations were continuously logged in the field by our geologist and classified in accordance with the Unified Soil Classification System (refer to Appendix A). Representative samples were obtained from the exploratory excavations at selected depths appropriate to the investigation. All samples were returned to our laboratory for evaluation and testing. Exploratory excavation logs have been prepared on the basis of our observations and laboratory test results. Logs of the excavations are attached as Figure Nos. IIIa-d. IV. LABORATORY TESTS AND SOIL INFORMATION Laboratory tests were performed on disturbed and relatively undisturbed soil samples in order to evaluate their physical and mechanical properties and their ability to support the proposed residential structures and improvements. Test results are summarized on Figure Nos. IIIa-d and IV. The following tests were conducted on the sampled soils: Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 4 1. Standard Test Method for Density of Soil In-place by the Drive-Cylinder Method (ASTM D2937-17e12) 2. Standard Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures using Coated Samples (ASTM D1188-07Moisture Content (ASTM D2216-19) 3. Moisture Content (ASTM D2216-10) 4. Laboratory Compaction Characteristics (ASTM D1557-12) 5. Determination of Percentage of Particles Smaller than #200 Sieve (ASTM D1140-06) Moisture content and density measurements (ASTM D2937) were performed on soils collected by the Drive Cylinder Method performed with a sampler driven with a manual hammer. Density measurements were also performed by ASTM method 1188, the bulk specific gravity utilizing paraffin-coated specimens. The Moisture Content of a soil sample is a measure of the water content, expressed as a percentage of the dry weight of the sample (ASTM D2216). These tests help to establish the in situ moisture and density of retrieved samples. Laboratory compaction values (ASTM D1557) establish the optimum moisture content and the laboratory maximum dry density of the tested soils. The relationship between the moisture and density of remolded soil samples helps to establish the relative compaction of the existing fill soils and soil compaction conditions to be anticipated during any future grading operation. The passing -200 sieve size analysis (ASTM D1140) aids in classification of the tested soils based on their fine material content and provide qualitative information related to engineering characteristics such as expansion potential, permeability, and shear strength. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 5 The expansion potent ial of soils is determined, when necessary, utilizing the Standard Test Method for Expansion Index of Soils (ASTM 04829). In accordance with the Standard (Table 5.3), potentially expansive soils are classified as follows : EXPANSION INDEX POTENTIAL EXPANSION Oto 20 Verv low 21 to 50 Low 51 to 90 Medium 91 to 130 Hiqh Above 130 Ve ry hiqh Based on visual observations, the particle size smaller than No. 200 sieve analysis, and our experience with similar soils in this area of Carlsbad, it is our opinion that the sampled existing, silty sand fill soils and formational materials possess a "Low" expansion potential Based on the field and laboratory test data, our observations of the primary soil types, and our previous experience with laboratory testing of similar soils, our Geotechnical Engineer has assigned values for friction angle, coefficient of friction, and cohesion for those soils that will have significant lateral support or load bearing functions on the project. These values have been utilized in determining the recommended bearing value as well as active and passive earth pressure design criteria. V. REGIONAL GEOLOGIC DESCRIPTION San Diego County has been divided into three major geomorphic provinces: the Coastal Plain, the Peninsular Ranges and the Salton Trough. The Coastal Plain exists west of the Peninsular Ranges. The Salton Trough is east of the Peninsular Ranges. These divisions are the result of the basic geologic distinctions between the areas. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 6 Mesozoic metavolcanic, metasedimentary and plutonic rocks predominate in the Peninsular Ranges with primarily Cenozoic sedimentary rocks to the west and east of this central mountain range (Demere, 1997). In the Coastal Plain region, where the subject property is located, the "basement" consists of Mesozoic crystalline rocks. Basement rocks are also exposed as high relief areas (e.g., Black Mountain northeast of the subject property and Cowles Mountain near the San Carlos area of San Diego). Younger Cretaceous and Tertiary sediments lap up against these older features. These sediments form a "layer cake" sequence of marine and non-marine sedimentary rock units, with some formations up to 140 million years old. Faulting related to the La Nacion and Rose Canyon Fault zones has broken up this sequence into a number of distinct fault blocks in the southwestern part of the county. Northwestern portions of the county are relatively undeformed by faulting (Demere, 1997). The Peninsular Ranges form the granitic spine of San Diego County. These rocks are primarily plutonic, forming at depth beneath the earth's crust 140 to 90 million years ago as the result of the subduction of an oceanic crustal plate beneath the North American continent. These rocks form the much larger Southern California batholith. Metamorphism associated with the intrusion of these great granitic masses affected the much older sediments that existed near the surface over that period of time. These metasedimentary rocks remain as roof pendants of marble, schist, slate, quartzite and gneiss throughout the Peninsular Ranges. Locally, Miocene-age volcanic rocks and flows have also accumulated within these mountains (e.g., Jacumba Valley). Regional tectonic forces and erosion over time have uplifted and unroofed these granitic rocks to expose them at the surface (Demere, 1997). Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 7 The Salton Trough is the northerly extension of the Gulf of California. This zone is undergoing active deformation related to faulting along the Elsinore and San Jacinto Fault Zones, which are part of the major regional tectonic feature in the southwestern portion of California, the San Andreas Fault Zone. Translational movement along these fault zones has resulted in crustal rifting and subsidence. The Salton Trough, also referred to as the Colorado Desert, has been filled with sediments to depth of approximately 5 miles since the movement began in the early Miocene, 24 million years ago. The source of these sediments has been the local mountains as well as the ancestral and modern Colorado River (Demere, 1997). As indicated previously, the San Diego area is part of a seismically active region of California. It is on the eastern boundary of the Southern California Continental Borderland, part of the Peninsular Ranges Geomorphic Province. This region is part of a broad tectonic boundary between the North American and Pacific Plates. The actual plate boundary is characterized by a complex system of active, major, right- lateral strike-slip faults, trending northwest/southeast. This fault system extends eastward to the San Andreas Fault (approximately 70 miles from San Diego) and westward to the San Clemente Fault (approximately 50 miles off-shore from San Diego) (Berger and Schug, 1991). In California, major earthquakes can generally be correlated with movement on active faults. As defined by the California Division of Mines and Geology, now the California Geological Survey, an "active" fault is one that has had ground surface displacement within Holocene time, about the last 11,000 years (Hart and Bryant, 1997). Additionally, faults along which major historical earthquakes have occurred (about the last 210 years in California) are also considered to be active (Association of Engineering Geologist, 1973). The California Division of Mines and Geology defines a "potentially active" fault as one that has had ground surface displacement during Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 8 Quaternary time, that is, between 11,000 and 1.6 million years (Hart and Bryant, 1997). During recent history, prior to April 2010, the San Diego County area has been relatively quiet seismically. No fault ruptures or major earthquakes had been experienced in historic time within the greater San Diego area. Since earthquakes have been recorded by instruments (since the 1930s), the San Diego area has experienced scattered seismic events with Richter magnitudes generally less than M4.0. During June 1985, a series of small earthquakes occurred beneath San Diego Bay, three of which were recorded at M4.0 to M4.2. In addition, the Oceanside earthquake of July 13, 1986, located approximately 26 miles offshore of the City of Oceanside, had a magnitude of M5.3 (Hauksson and Jones, 1988). On June 15, 2004, a M5.3 earthquake occurred approximately 45 miles southwest of downtown San Diego (26 miles west of Rosarito, Mexico). Although this earthquake was widely felt, no significant damage was reported. Another widely felt earthquake on a distant southern California fault was a M5.4 event that took place on July 29, 2008, west-southwest of the Chino Hills area of Riverside County. Several earthquakes ranging from M5.0 to M6.0 occurred in northern Baja California, centered in the Gulf of California on August 3, 2009. These were felt in San Diego but no injuries or damage was reported. A M5.8 earthquake followed by a M4.9 aftershock occurred on December 30, 2009, centered about 20 miles south of the Mexican border city of Mexicali. These were also felt in San Diego, swaying high-rise buildings, but again no significant damage or injuries were reported. On April 4, 2010, a large earthquake occurred in Baja California, Mexico. It was widely felt throughout the southwest including Phoenix, Arizona and San Diego in Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 9 California. This M7.2 event, the Sierra El Mayor earthquake, occurred in northern Baja California, approximately 40 miles south of the Mexico-USA border at shallow depth along the principal plate boundary between the North American and Pacific plates. According to the U. S. Geological Survey this is an area with a high level of historical seismicity, and it has recently also been seismically active, though this is the largest event to strike in this area since 1892. The April 4, 2010, earthquake appears to have been larger than the M6.9 earthquake in 1940 or any of the early 20th century events (e.g., 1915 and 1934) in this region of northern Baja California. The event caused widespread damage to structures, closure of businesses, government offices and schools, power outages, displacement of people from their homes and injuries in the nearby major metropolitan areas of Mexicali in Mexico and Calexico in Southern California. This event's aftershock zone extends significantly to the northwest, overlapping with the portion of the fault system that is thought to have ruptured in 1892. Some structures in the San Diego area experienced minor damage and there were some injuries. Ground motions for the April 4, 2010, main event, recorded at stations in San Diego and reported by the California Strong Motion Instrumentation Program (CSMIP), ranged up to 0.058g. On July 7, 2010, a M5.4 earthquake occurred in Southern California at 4:53 pm (Pacific Time) about 30 miles south of Palm Springs, 25 miles southwest of Indio, and 13 miles north-northwest of Borrego Springs. The earthquake occurred near the Coyote Creek segment of the San Jacinto Fault. The earthquake exhibited right lateral slip to the northwest, consistent with the direction of movement on the San Jacinto Fault. The earthquake was felt throughout Southern California, with strong shaking near the epicenter. It was followed by more than 60 aftershocks of Ml.3 and greater during the first hour. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 10 In the last 50 years, there have been four other earthquakes in the magnitude M5.0 range within 20 kilometers of the Coyote Creek segment: M5.8 in 1968, M5.3 on 2/25/1980, M5.0 on 10/31/2001, and M5.2 on 6/12/2005. The biggest earthquake near this location was the M6.0 Buck Ridge earthquake on 3/25/1937. VI. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION A. Stratigraphy Our field work, reconnaissance and review of the geologic map by Kennedy and Tan, 2007, "Geologic Map of the Oceanside 30'x60' Quadrangle, CA," indicate that the site is underlain by formational materials identified as the Quaternary-age Old Paralic Deposits (QOP6-7 ). The formational materials are generally overlain by approximately 1 feet of topsoils across most of the lot, with up to 4 feet of fill and topsoils encountered in the southwestern portion of the lot (HP-3). A localized area of loose topsoil with trash debris extending to 5 feet in depth was encountered at the location of excavation HP-4 in the southeastern portion of the site. Figure No. V presents a geologic map (Kennedy and Tan, 2007) of the general area of the site. Topsoils: Topsoils/ agricultural topsoils were encountered at all excavation locations and ranged in thickness from approximately 1 foot in the northern (rear yard) area to 4 feet at the southwest corner. As noted above, a localized area of loose topsoil with trash debris extending to 5 feet in depth was encountered at the location of excavation HP-4 in the southeastern portion of the site. The encountered topsoils consist of loose, light brown to dark brown, fine-to-medium grained silty sand with some roots. The topsoils are considered not suitable in their current condition to support additional fill or loads from the proposed residential structures or Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 11 improvements. The encountered topsoils are considered to have a low expansion potential. Refer to Figure Nos. Illa-d and Figure No. IV for details. Very Old Paralic Deposits (Qvop): Old Paralic Deposits were encountered underlying the topsoils and consist of red-to orange-brown, medium dense, damp, fine-to medium-grained silty sand. The upper 1 to 2 feet is weathered. These soils below a depth of 4 feet are considered to have adequate bearing strength to support new fill and/or proposed structures and improvements. Refer to Figure Nos. IIIa-d and Figure No. IV for details. B. Structure Quaternary-age Old Paralic Deposits underlie the entire site at shallow depth and are underlain at depth by the Eocene-age Santiago Formation (Tsa). The Old Paralic Deposits are relatively flat-lying as depicted on the geologic map (Kennedy and Tan, 2007; Figure No. V). Although not encountered in our shallow excavations, the Santiago Formation strikes approximately east-west and dips 8 to 10 degrees to the north-northeast as depicted on the geologic map. No faults are indicated on or nearby the site on the geologic map. The geologic structure and relatively flat topography presents no adverse soil stability conditions for the property. VII. GEOLOGIC HAZARDS The following is a discussion of geologic conditions and hazards common to this area of the City of Carlsbad, as well as site-specific geologic information relating to the subject property. Hemlock Coastal Homes Residential Project Carlsbad, California A. Local and Regional Faults Job No. 20-12842 Page 12 Reference to the geologic map of the area (Kennedy and Tan, 2007), Figure No. V, indicates that no faults are shown to cross the site. In our explicit professional opinion, neither an active fault nor a potentially active fault underlies the site. Rose Can yon Fault: The Rose Canyon Fault Zone (Mount Soledad and Rose Canyon Faults) is located approximately 5 miles west of the subject site. The Rose Canyon Fault is mapped trending north-south from Oceanside to downtown San Diego, from where it appears to head southward into San Diego Bay, through Coronado and offshore. The Rose Canyon Fault Zone is considered to be a complex zone of onshore and offshore, en echelon strike slip, oblique reverse, and oblique normal faults. The Rose Canyon Fault is considered to be capable of generating an M7 .2 earthquake and is considered micro-seismically active, although no significant recent earthquakes since 1769 are known to have occurred on the fault. Investigative work on faults that are part of the Rose Canyon Fault Zone at the Police Administration and Technical Center in downtown San Diego, at the SDG&E facility in Rose Canyon, and within San Diego Bay and elsewhere within downtown San Diego, has encountered offsets in Holocene (geologically recent) sediments. These findings confirm Holocene displacement on the Rose Canyon Fault, which was designated an "active" fault in November 1991 (Hart, E.W. and W.A. Bryant, 2007, Fault-Rupture Hazard Zones in California, California Geological Survey Special Publication 42). Rockwell (2010) has suggested that the RCFZ underwent a cluster of activity including 5 major earthquakes in the early Holocene, with a long period of inactivity following, suggesting major earthquakes on the RCFZ behaves in a cluster-mode, where earthquake recurrence is clustered in time rather than in a consistent Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 13 recurrence interval. With the most recent earthquake (MRE) nearly 500 years ago, it is suggested that a period of earthquake activity on the RCFZ may have begun. Rockwell (2010) and a compilation of the latest research implies a long-term slip rate of approximately 1-2 mm/year. Newport-Inglewood Fault: The offshore portion of the Newport-Inglewood Fault Zone is located approximately 5 miles west and northwest of the site. A significant earthquake (M6.4) occurred along this fault on March 10, 1933. Since then no additional significant events have occurred. The fault is believed to have a slip rate of approximately 0.6 mm/year with an unknown recurrence interval. This fault is believed capable of producing an earthquake of M6.0 to M7.4 (Grant Ludwig and Shearer, 2004). Coronado Bank Fault: The Coronado Bank Fault is located approximately 20 miles southwest of the site. Evidence for this fault is based upon geophysical data (acoustic profiles) and the general alignment of epicenters of recorded seismic activity (Greene, et al., 1979). The Oceanside earthquake of M5.3 recorded July 13, 1986, is known to have been centered on the fault or within the Coronado Bank Fault Zone. Although this fault is considered active, due to the seismicity within the fault zone, it is significantly less active seismically than the Elsinore Fault (Hileman, 1973). It is postulated that the Coronado Bank Fault is capable of generating a M7.6 earthquake and is of great interest due to its close proximity to the greater San Diego metropolitan area. Elsinore Fault: The Elsinore Fault is located approximately 25 to 59 miles east and northeast of the site. The fault extends approximately 200 kilometers (125 miles) from the Mexican border to the northern end of the Santa Ana Mountains. The Elsinore Fault zone is a 1-to 4-mile-wide, northwest-southeast-trending zone of Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 14 discontinuous and en echelon faults extending through portions of Orange, Riverside, San Diego, and Imperial Counties. Individual faults within the Elsinore Fault Zone range from less than 1 mile to 16 miles in length. The trend, length and geomorphic expression of the Elsinore Fault Zone identify it as being a part of the highly active San Andreas Fault system. Like the other faults in the San Andreas system, the Elsinore Fault is a transverse fault showing predominantly right-lateral movement. According to Hart, et al. (1979), this movement averages less than 1 centimeter per year. Along most of its length, the Elsinore Fault Zone is marked by a bold topographic expression consisting of linearly aligned ridges, swales and hallows. Faulted Holocene alluvial deposits (believed to be less than 11,000 years old) found along several segments of the fault zone suggest that at least part of the zone is currently active. Although the Elsinore Fault Zone belongs to the San Andreas set of active, northwest- trending, right-slip faults in the southern California area (Crowell, 1962), it has not been the site of a major earthquake in historic time, other than a M6.0 earthquake near the town of Elsinore in 1910 (Richter, 1958; Toppozada and Parke, 1982). However, based on length and evidence of late-Pleistocene or Holocene displacement, Greensfelder (1974) has estimated that the Elsinore Fault Zone is reasonably capable of generating an earthquake ranging from M6.8 to M7 .1. Faulting evidence exposed in trenches placed in Glen Ivy Marsh across the Glen Ivy North Fault (a strand of the Elsinore Fault Zone between Corona and Lake Elsinore), suggest a maximum earthquake recurrence interval of 300 years, and when combined with previous estimates of the long-term horizontal slip rate of 0.8 to 7 .0 mm/year, suggest typical earthquakes of M6.0 to M7.0 (Rockwell et al., 1985). The Working Group on California Earthquake Probabilities (2008) has estimated that there is a 11 percent Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 15 probability that an earthquake of M6. 7 or greater will occur within 30 years on this fault. San Jacinto Fault: The San Jacinto Fault is located 47 to 60 miles to the northeast of the site. The San Jacinto Fault Zone consists of a series of closely spaced faults, including the Coyote Creek Fault, that form the western margin of the San Jacinto Mountains. The fault zone extends from its junction with the San Andreas Fault in San Bernardino, southeasterly toward the Brawley area, where it continues south of the international border as the Imperial Transform Fault (Earth Consultants International [ECI], 2009). The San Jacinto Fault zone has a high level of historical seismic activity, with at least 10 damaging earthquakes (M6.0 to M7.0) having occurred on this fault zone between 1890 and 1986. Earthquakes on the San Jacinto Fault in 1899 and 1918 caused fatalities in the Riverside County area. Offset across this fault is predominantly right- lateral, similar to the San Andreas Fault, although some investigators have suggested that dip-slip motion contributes up to 10% of the net slip (ECI, 2009). The segments of the San Jacinto Fault that are of most concern to major metropolitan areas are the San Bernardino, San Jacinto Valley and Anza segments. Fault slip rates on the various segments of the San Jacinto are less well constrained than for the San Andreas Fault, but the available data suggest slip rates of 12 ±6 mm/year for the northern segments of the fault, and slip rates of 4 ±2 mm/year for the southern segments. For large ground-rupturing earthquakes on the San Jacinto fault, various investigators have suggested a recurrence interval of 150 to 300 years. The Working Group on California Earthquake Probabilities (WGCEP, 2008) has estimated that there is a 31 percent probability that an earthquake of M6. 7 or greater will occur within 30 years on this fault. Maximum credible earthquakes of M6. 7, M6.9, and M7.2 are Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 16 expected on the San Bernardino, San Jacinto Valley and Anza segments, respectively, capable of generating peak horizontal ground accelerations of 0.48g to 0.53g in the County of Riverside (ECI, 2009). A M5.4 earthquake occurred on the San Jacinto Fault on July 7, 2010. The United States Geological Survey has issued the following statements with respect to the recent seismic activity on southern California faults: The San Jacinto fault, along with the Elsinore, San Andreas, and other faults, is part of the plate boundary that accommodates about 2 inches/year of motion as the Pacific plate moves northwest relative to the North American plate. The largest recent earthquake on the San Jacinto fault, near this location, the M6.5 1968 Borrego Mountain earthquake April 8, 1968, occurred about 25 miles southeast of the July 7, 2010, M5.4 earthquake. This M5.4 earthquake follows the April 4, 2010, M7 .2 earthquake, located about 125 miles to the south, well south of the US Mexico international border. A M4.9 earthquake occurred in the same area on June 12, 2010, at 8 :08 pm (Pacific Time). Thus, this section of the San Jacinto fault remains active. Seismologists are watching two major earthquake faults in southern California. The San Jacinto fault, the most active earthquake fault in southern California, extends for more than 100 miles from the international border into San Bernardino and Riverside, a major metropolitan area often called the Inland Empire. The Elsinore fault is more than 110 miles long, and extends into the Orange County and Los Angeles area as the Whittier fault. The Elsinore fault is capable of a major earthquake that would significantly affect the large metropolitan areas of southern California. The Elsinore fault has not hosted a major earthquake in more than 100 years. The occurrence of these earthquakes along the San Jacinto fault and continued aftershocks demonstrates that the earthquake activity in the region remains at an elevated level. The San Jacinto fault is known as the most active earthquake fault in southern California. Caltech and USGS seismologist continue to monitor the ongoing earthquake activity using the Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 17 Caltech/USGS Southern California Seismic Network and a GPS network of more than 100 stations. B. Other Geologic Hazards Ground Rupture: Ground rupture is characterized by bedrock slippage along an established fault and may result in displacement of the ground surface. For ground rupture to occur along a fault, an earthquake usually exceeds MS.0. If a MS.0 earthquake was to take place on a local fault, an estimated surface-rupture length 1 mile long could be expected (Greensfelder, 1974 ). Our investigation indicates that the subject site is not directly on a known active fault trace and, therefore, the risk of ground rupture is remote. Ground Shaking : Structural damage caused by seismically induced ground shaking is a detrimental effect directly related to faulting and earthquake activity. Ground shaking is considered to be the greatest seismic hazard in San Diego County. The intensity of ground shaking is dependent on the magnitude of the earthquake, the distance from the earthquake, and the seismic response characteristics of underlying soils and geologic units. Earthquakes of MS.0 or greater are generally associated with significant damage. It is our opinion that the most serious damage to the site would be caused by a large earthquake originating on a nearby strand of the Rose Canyon or Newport-Inglewood Faults. Although the chance of such an event is remote, it could occur within the useful life of the structure. Liquefaction: The liquefaction of saturated sands during earthquakes can be a major cause of damage to buildings. Liquefaction is the process by which soils are transformed into a viscous fluid that will flow as a liquid when unconfined. It occurs primarily in loose, saturated sands and silts when they are sufficiently shaken by an earthquake. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 18 On this site, the risk of liquefaction of foundation materials due to seismic shaking is also considered to be remote due to the medium dense nature of the natural-ground material, the anticipated high density of the proposed recompacted fill, and the lack of a shallow static groundwater surface under the site. No soil liquefaction or soil strength loss is anticipated to occur due to a seismic event. Tsunami: A tsunami is a series of long waves generated in the ocean by a sudden displacement of a large volume of water. Underwater earthquakes, landslides, volcanic eruptions, meteoric impacts, or onshore slope failures can cause this displacement. Tsunami waves can travel at speeds averaging 450 to 600 miles per hour. As a tsunami nears the coastline, its speed diminishes, its wave length decreases, and its height increases greatly. After a major earthquake or other tsunami-inducing activity occurs, a tsunami could reach the shore within a few minutes. One coastal community may experience no damaging waves while another may experience very destructive waves. Some low-lying areas could experience severe inland inundation of water and deposition of debris more than 3,000 feet inland. The site is located approximately 0.2-mile from the Pacific Ocean strand line at an elevation of 56 feet above MSL. It is unlikely that a tsunami would affect the lot. Landslides: Based upon our geotechnical investigation and review of the geologic map (Kennedy and Tan, 2007) there are no known or suspected ancient landslides located on the site. Slope Stability: The proposed areas of construction are not affected by any significant slopes subject to slope stability problems, and no slope stability calculations were required during this soil investigation. Review of site conditions, aerial photographs, Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 19 and pertinent documents and geologic maps, as well as our experience with similar formational units in this area of Carlsbad indicate that the site is not impacted by landslides. c. Geologic Hazards Summary It is our opinion, based upon a review of the available maps, our research and our site investigation, that the shallow surficial soils are underlain by stable formational materials and the site is suited for the proposed residential structures and associated improvements provided the recommendations presented herein are implemented. In addition, no significant geologic hazards are known to exist on the subject site that would prohibit the proposed construction. Ground shaking from earthquakes on active southern California faults and active faults in northwestern Mexico is the greatest geologic hazard at the property. Design of building structures in accordance with the current building codes would reduce the potential for injury or loss of human life. Buildings constructed in accordance with current building codes may suffer significant damage but should not undergo total collapse. In our explicit professional opinion, no "active" or "potentially active" faults underlie the project site. VIII. GROUNDWATER Groundwater and/or perched water conditions were not encountered at the explored excavation locations and we do not expect significant groundwater and/or perched water problems to develop in the future if proper drainage is maintained on the property. It must be noted, however, that fluctuations in the level of groundwater Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 20 may occur due to variations in ground surface topography, subsurface stratification, rainfall, and other possible factors that may not have been evident at the time of our field investigation. It should be kept in mind that construction operations may change surface drainage patterns and/or reduce surface permeabilities due to the densification of compacted soils. Such changes of surface and subsurface hydrologic conditions, plus irrigation of landscaping or significant increases in rainfall, may result in the appearance of surface or near-surface water at locations where none existed previously. The appearance of such water is expected to be localized and cosmetic in nature, if good positive drainage is implemented, as recommended in this report, during and at the completion of construction. It must be understood that unless discovered during initial site exploration or encountered during site construction, it is extremely difficult to predict if or where perched or true groundwater conditions may appear in the future. When site formational soils are fine-grained and of low permeability, water problems may not become apparent for extended periods of time. Water conditions, where suspected or encountered during construction operations, should be evaluated and remedied by the project civil and geotechnical consultants. The project developer and property owner, however, must realize that post- construction appearances of groundwater may have to be dealt with on a site-specific basis. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 21 IX. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based on the field investigation conducted by our firm, our laboratory test results, our analysis of the field and laboratory data, and our experience with similar soils and formational materials. From a geotechnical engineering standpoint, it is our opinion that the site is suitable for construction of the proposed residential structures and associated improvements provided the conclusions and recommendations presented in this report are incorporated into its design and construction . Earthwork and foundation recommendations are presented in the following paragraphs. The opinions, conclusions, and recommendations presented in this report are contingent upon Geotechnical Exploration, Inc. being retained to review the final plans and specifications as they are developed and to observe the site earthwork and installation of foundations. Accordingly, we recommend that the following paragraph be included on the grading and foundation plans for the project. If the geotechnical consultant of record is changed for the project, the work shall be stopped until the replacement has agreed in writing to accept responsibility within their area of technical competence for approval upon completion of the work. It shall be the responsibility of the permittee to notify the governing agency in writing of such change prior to the recommencement of grading and/or foundation installation work and comply with the governing agency's requirements for a change to the Geotechnical Consultant of Record for the project. A. Site Soil Preparation and Earthwork 1. Clearing and Stripping: The existing structure, improvements, and vegetation should be removed prior to the preparation of the building pads and areas of Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 22 2. associated improvements. This includes root systems from existing trees and shrubbery. All loose or soft soils in areas to receive structures should be removed and recompacted to depths estimated to range to 2 to 3 feet on the northern portion of the property to 4 feet on the southern portion, until dense formational soils are exposed. Removal to 5 feet should be anticipated in the area of excavation HP-4 near the southwestern edge of the existing structure, where buried trash debris was encountered. Existing topsoils with an organic content of greater than 3 percent by volume are, in general, not suitable for use as new fill. All concrete and construction debris should be removed off- site. Treatment of Existing Topsoils and Weathered Formational Soils: In order to provide suitable support for the proposed structures and associated improvements, we recommend that all topsoils and weathered formational materials be removed and replaced as structural fill compacted to a minimum degree of compaction of 90 percent. The limits of soil removal and recompaction should extend at least 5 feet beyond the perimeter limits of all structures and new improvements or the depth of excavation, whichever is larger, where feasible. The recompaction work should consist of removing all existing topsoils and weathered formational materials down to the underlying adequate-bearing undisturbed formational materials within the areas to receive site improvements or additional fill soils. Actual required removal depths will be determined by the field soils technician or geologist during the grading operation. The bottom of the excavation should be scarified at least 8 inches, moisture conditioned and compacted, including the exposed dense natural subgrade soils, and all soils should be replaced as compacted structural fill. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 23 3. 4. The areal extent and depths required to remove the existing topsoils and weathered formational materials should be determined by our representative during the excavation work based on their examination of the soils being exposed and physical constraints. Subgrade Preparation: After the site has been cleared, stripped, and the required excavations made, the exposed formational materials in areas to receive fill and/or slab on grade, and/or building improvements, should be scarified to a depth of 8 inches, moisture conditioned to at least 3 percent above the appropriate laboratory optimum, and compacted to the requirements for structural fill. Although not anticipated, in the event that planned cuts expose any medium to highly expansive formational materials in the building area, they should be scarified and moisture conditioned to at least 5 percent over optimum moisture. Material for Fill: Existing on-site soils with an organic content of less than 3 percent by volume are, in general, suitable for use as fill. Fill and topsoils with an organic content of greater than 3 percent by volume are, in general, not suitable for use as fill. Imported fill material, where required, should have a low-expansion potential (Expansion Index of 50 or less per ASTM D4829-11). In addition, both imported and existing on-site materials for use as fill should not contain rocks or lumps more than 6 inches in greatest dimension if the fill soils are compacted with heavy compaction equipment (or 3 inches in greatest dimension if compacted with lightweight equipment). All materials for use as fill should be approved by our representative prior to importing to the site. 5. Fill Compaction: All structural fill, and areas to receive any associated improvements, should be compacted to a minimum degree of compaction of Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 24 6. 90 percent based upon ASTM D1557-12. Fill material should be spread and compacted in uniform horizontal lifts not exceeding 8 inches in uncompacted thickness. Before compaction begins, the fill should be brought to a water content that will permit proper compaction by either: (1) aerating and drying the fill if it is too wet, or (2) watering the fill if it is too dry. Each lift should be thoroughly mixed before compaction to ensure a uniform distribution of moisture. Any rigid improvements founded on existing undocumented fill soils and/or topsoils can be expected to undergo movement and possible damage. Geotechnical Exploration, Inc. takes no responsibility for the performance of any improvements built on loose natural soils or inadequately compacted fills. Subgrade soils in any exterior area receiving concrete improvements should be verified for compaction and moisture by a representative of our firm within 48 hours prior to concrete placement. No uncontrolled fill soils should remain after completion of the site work. In the event that temporary ramps or pads are constructed of uncontrolled fill soils, the loose fill soils should be removed and/or recompacted prior to completion of the grading operation. Trench Backfill: All utility trenches should be backfilled with properly compacted fill. Backfill material should be placed in lift thicknesses appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent by mechanical means. Any portion of the trench backfill within public street pavement sections should conform to the material and compaction requirements of the adjacent pavement section. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 25 Our experience has shown that even shallow, narrow trenches, such as for irrigation and electrical lines, that are not properly compacted can result in problems, particularly with respect to shallow groundwater accumulation and migration. B. Seismic Design Criteria 7. Seismic Design Criteria: Site-specific seismic design criteria for the proposed structures are presented in the following table in accordance with Section 1613 of the 2019 CBC, which incorporates by reference ASCE 7-16 for seismic design. We have determined the mapped spectral acceleration values for the site, based on a latitude of 33.1505 degrees and longitude of 117.3440 degrees, utilizing a third-party tool provided by the USGS, which provides a solution for ASCE 7-16 (Section 1613 of the 2019 CBC) utilizing SEAOC Seismic Design Map Tool, which provides a solution for ASCE 7-16 (Section 1613 of the 2019 CBC) utilizing digitized files for the Spectral Acceleration maps. Based on our past experience with similar conditions, we have assigned a Site Soil Classification of Stiff Soil D, Seismic Risk II and Seismic Design Category D. c. 8. TABLE I Mapped Spectral Acceleration Values and Design Parameters Fa Fv Sms 1.091 1.063 1.90 1.161 Design Parameters for Proposed Foundations Footings: Shallow footings should bear on properly compacted fill soils or formational material. All new footings to support new structures should be embedded at least 18 inches into properly compacted soils. The footings Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 26 9. should be founded at least 24 inches below the lowest adjacent finished grade when founded into properly compacted fill or into medium dense formational material. Footings located adjacent to utility trenches should have their bearing surfaces situated below an imaginary 1.0: 1.0 plane projected upward from the bottom edge of the adjacent utility trench. The utility trench shall be backfilled with properly compacted soils. Bearing Values: At the recommended depths, footings on native, medium dense formational soils or properly compacted soils may be designed for allowable bearing pressures of 2,500 pounds per square foot (psf) for combined dead and live loads and 3,300 psf for all loads, including wind or seismic. The footings should, however, have a minimum width of 15 inches. An increase in soil allowable static bearing can be used as follows: 700 psf for each additional foot over 2.0 feet in depth and 350 psf for each additional foot in width to a total not exceeding 4,500 psf for static loading. 10. General Criteria for All Footings: Footings located adjacent to utility trenches should have their bearing surfaces situated below an imaginary 1.0 horizontal to 1.0 vertical plane projected upward from the bottom edge of the adjacent utility trench. All continuous footings should contain top and bottom reinforcement to provide structural continuity and to permit spanning of local irregularities. We recommend that for 18-inch-deep and 15-inch wide footings, a minimum of four No. 5 reinforcing bars be provided in the footings (two at the top and two at the bottom). A minimum clearance of 3 inches should be maintained between steel reinforcement and the bottom or sides of the footing. Isolated square footings should contain, as a minimum, a grid of three No. 4 steel bars on 12-inch centers, both ways. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 27 In order for us to offer an opinion as to whether the footings are founded on soils of sufficient load bearing capacity, it is essential that our representative observe footing excavations prior to the placement of reinforcing steel or concrete. NOTE: The project Civil/Structural Engineer should review all reinforcing schedules. The reinforcing minimums recommended herein are not to be construed as structural designs, but merely as minimum reinforcement to reduce the potential for cracking and separations. 11. Lateral Loads: Lateral load resistance for the structure supported on footing foundations may be developed in friction between the foundation bottoms and the supporting subgrade. An allowable friction coefficient of 0.4 is considered applicable. An additional allowable passive resistance equal to an equivalent fluid weight of 275 pounds per cubic foot (pcf) acting against the foundations may be used in design provided the footings are poured neat against the dense formational or properly compacted fill materials. These lateral resistance values assume a level surface in front of the footing for a minimum distance of three times the embedment depth of the footing . 12. Settlement: Settlements under building loads are expected to be within tolerable limits for the proposed residence. For footings designed in accordance with the recommendations presented in the preceding paragraphs, we anticipate that total settlements should not exceed 1 inch and that post- construction differential angular rotation should be less than 1/240. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 28 D. Concrete Slab On-grade Criteria Slabs on-grade may only be founded on properly compacted fill or medium dense formational soils. 13. Minimum Floor Slab Reinforcement: Based on our experience, we have found that, for various reasons, floor slabs occasionally crack. Therefore, we recommend that all slabs on-grade contain at least a minimum amount of reinforcing steel to reduce the separation of cracks, should they occur. Slab subgrade soil should be verified by a Geotechnical Exploration, Inc. representative to have the proper moisture content within 48 hours prior to placement of the vapor barrier and pouring of concrete. New interior floor slabs should be a minimum of 4 inches actual thickness and be reinforced with No. 3 bars on 18-inch centers, both ways, placed at mid- height in the slab on properly compacted subgrade. We note that shrinkage cracking can result in reflective cracking in brittle flooring surfaces such as stone and tiles. It is imperative that if movement intolerant flooring materials are to be utilized, the flooring contractor and/or architect should provide specifications for the use of high-quality isolation membrane products installed between slab and floor materials. 14. Slab Moisture Emission: Although it is not the responsibility of geotechnical engineering firms to provide moisture protection recommendations, as a service to our clients, we provide the following discussion and suggest the consideration of moisture protection criteria. Actual recommendations should be provided by the project architect and/or waterproofing consultants or Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 29 product manufacturer. It is recommended to schedule a pre-construction meeting with the vapor barrier product representative. Soil moisture transmitted as vapor through concrete can result in damage to moisture-sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor surface. In addition, excessive moisture vapor can facilitate mold and stains on slab surfaces, walls, and carpets. The common practice in Southern California is to place vapor retarders made of PVC, or of polyethylene. PVC retarders are made in thickness ranging from 10 to 60 millimeters. Polyethylene retarders, called Visqueen, range from 5 to 10 millimeters in thickness. These products are no longer considered adequate for moisture protection and can actually deteriorate over time. Specialty vapor retarding and barrier products possess higher tensile strength and are specifically designed for and intended to retard moisture transmission into concrete slabs. The use of such products is highly recommended for the reduction of floor slab moisture emission. The following American Society for Testing and Materials (ASTM) and American Concrete Institute (ACI) sections address the issue of moisture transmission into and through concrete slabs: ASTM E1745-17 Standard Specification for Plastic Water Vapor Retarders Used in Contact Concrete Slabs; ASTM E1643- 18a Standard Practice for Selection, Design, Installation, and Inspection of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs; ACI 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials; and ACI 302.lR-15 Guide to Concrete Floor and Slab Construction. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 30 14.1 Based on the above, we recommend that the vapor barrier consists of a minimum 15-mil extruded polyolefin plastic (no recycled content or woven materials permitted). Permeance as tested before and after mandatory conditioning (ASTM E1745 Section 7.1 and subparagraphs 7.1.1-7.1.5) should be less than 0.01 perms (grains/square foot/hour/per inch of Mercury) and comply with the ASTM E1745-17 Class A requirements. The installation of vapor barriers should be in accordance with ASTM E1643-18a. The basis of design is 15-mil Stego Wrap vapor barrier placed per the manufacturer's guidelines. Reef Industries Vapor Guard membrane has also been shown to achieve a permeance of less than 0.01 perms. We recommend that the slab be poured directly on the vapor barrier, which is placed directly on the properly compacted prepared subgrade soil. 14.2 Common to all acceptable products, vapor retarder/barrier joints must be lapped at least 6 inches. Seam joints and permanent utility penetrations should be sealed with the manufacturer's recommended tape or mastic. Edges of the vapor retarder should be extended to terminate at a location in accordance with ASTM E1643-18a or to an alternate location that is acceptable to the project's structural engineer. All terminated edges of the vapor retarder should be sealed to the building foundation (grade beam, wall, or slab) using the manufacturer's recommended accessory for sealing the vapor retarder to pre-existing or freshly placed concrete. Additionally, in actual practice, stakes are often driven through the retarder material, equipment is dragged or rolled across the retarder, overlapping or jointing is not properly implemented, etc. All these construction deficiencies reduce the Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 31 retarder's effectiveness. In no case should retarder/barrier products be punctured or gaps be allowed to form prior to or during concrete placement. Vapor barrier-safe screeding and forming systems should be used that will not leave puncture holes in the vapor barrier, such as Beast Foot (by Stego Industries) or equivalent. 14.3 Vapor retarders/barriers do not provide full waterproofing for structures constructed below free water surfaces. They are intended to help reduce or prevent vapor transmission and/or capillary migration through the soil and through the concrete slabs. Waterproofing systems must be designed and properly constructed if full waterproofing is desired. The owner and project designers should be consulted to determine the specific level of protection required. 14.4 Following placement of any concrete floor slabs, sufficient drying time must be allowed before the placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. 15. Exterior Slab Reinforcement: As a minimum for protection of on-site improvements, we recommend that all nonstructural concrete slabs (such as patios, sidewalks, etc.), be at least 4 inches thick, be founded on properly compacted, tested fill soils and underlain by no more than 3 inches of clean leveling sand if needed; with No . 3 bars at 15-inch centers, both ways, at the center of the slab, and contain adequate isolation and control joints. The performance of on-site improvements can be greatly affected by soil base preparation and the quality of construction. It is, therefore, important that all Hemlock Coastal Homes Residential Project Carlsbad, California Job No . 20-12842 Page 32 improvements be properly designed and constructed for the existing soil conditions. The improvements should not be built on loose or inadequate bearing materials. For exterior slabs with the minimum shrinkage reinforcement, control joints should be placed at spaces no farther than 15 feet apart or the width of the slab, whichever is less, and also at re-entrant corners. Control joints in exterior slabs should be sealed with elastomeric joint sealant. The sealant should be inspected by the owner every six months and be properly maintained. 16. Driveway and Parking Garage Concrete Pavement: New driveway and parking garage pavements, consisting of Portland cement concrete at least 5.5 inches in thickness, may be placed on properly compacted, relatively smooth subgrade soils. The concrete should be at least 3,500 psi compressive strength, with control joints no farther than 12 feet apart and at re-entrant corners. Pavement joints should be properly sealed with a permanent joint sealant, as required in sections 201.3.6 through 201.3.8 of the Standard Specifications for Public Work Construction, 2018 Edition . The upper 12 inches of the subgrade below the driveway pavement should be compacted to a minimum degree of compaction of 95 percent just prior to paving. If control joints are to be spaced farther than 12 feet apart, the driveway slab should be reinforced with a grid of No. 4 steel bars on 15-inch centers, although spacing should be limited to no greater than 20 feet apart. All topsoils in proposed driveway areas should be removed down to medium dense formational materials and properly compacted prior to subgrade soil preparation. A representative from our firm should be present to verify areal Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 33 extents and depths of removal prior to replacement and compaction of new fill soils. If permeable pavement pavers are used, they should be placed on 1 inch of No. 8 bedding sand, on 6 inches of No. 57 gravel base, on properly compacted subgrade soils. The base and subgrade material should be compacted to at least 95 percent relative compaction . The subgrade and surface of pavers should drain toward the street or to perforated collection subdrain pipes discharging in an approved drainage facility. E. Retaining Wall Design Criteria Although no plans have been provided showing proposed exterior retaining walls at this time, we are providing retaining wall design criteria for any changes prior to the time of construction. 17. Retaining Walls: Restrained retaining walls backfilled with low expansive on- site or imported soils and level backfill should be designed for soil equivalent fluid weight of 56 pcf (76 pcf if supporting a 2: 1 sloping backfill). Unrestrained retaining walls using the same soil type indicated above may be designed for a soil equivalent fluid weight of 38 pcf for level backfill conditions and 52 pcf for 2 : 1 sloping backfill. A seismic soil pressure increment of 12 pcf is applicable to unrestrained retaining walls of 6 feet or higher soil retention. Uniform surcharge loads applied behind retaining walls may be converted to uniform horizontal soil pressures by using a conversion factor of 0.31 for unrestrained retaining walls with level backfill and 0.47 for retraining walls with Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 34 level backfill. For 2 : 1 sloping backfill, the previous factors should be increased by 1.37. All retaining walls should be waterproofed and provided with geodrain boards (such as MiraDrain 6000) and collector subdrain similar to the Total Drain product. The subdrain should discharge at an approved drainage facility as required by the City of Carlsbad. Any retaining wall backfill should be placed under our observation and testing. 18. Drainage Quality Control: It must be understood that it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall drain depth below the interior floor or yard surface, pipe percent slope to the outlet, etc. The drainage pipe should be perforated, SDR 35 or PVC Schedule 40, placed in the heel of the gravel layer foundation of the retaining walls and protected with geofabric such as Mirafi 140N or equivalent. The subdrains should discharge into an approved drainage pipe or approved facility, or an area acceptable to the City of San Diego. F. Site Drainage Considerations 19. Surface Drainage: Adequate measures should be taken to properly finish- grade the site after the new structures and improvements are in place. Drainage waters from this site and adjacent properties should be directed away from the footings and slabs, onto the natural drainage direction for this area Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 35 or into properly designed and approved drainage facilities provided by the project civil engineer. Proper subsurface and surface drainage will help reduce the potential for waters to seek the level of the bearing soils under the wall footings or other extensive improvements. Roof downspouts should be connected to underground storm drain lines. Failure to observe this recommendation could result in undermining, soil expansion, and possible differential settlement of the structure or other improvements or cause other moisture-related problems. Currently, the 2019 CBC requires a minimum of 1 percent surface gradient for proper drainage of building pads unless waived by the building official. Concrete pavement may have a minimum gradient of 0.5-percent. The Surface gradient adjacent to structures must drain away as indicated in the 2019 CBC. 20. Erosion Control: Appropriate erosion control measures should be taken at all times during and after construction to prevent surface runoff waters from entering footing excavations or ponding on finished building pad areas. 21. Planter Drainage: Any planter areas adjacent to the wall structure should be provided with sufficient area drains to help with rapid runoff disposal. No water should be allowed to pond adjacent to the wall or other improvements G. General Recommendations 22. Proiect Start-Up Notification: In order to reduce any work delays during site excavation and development, our firm should be contacted at least 48 hours before any required observation of footing excavations or field density testing of compacted fill soils. If possible, placement of formwork and steel Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 36 reinforcement in footing excavations should not occur prior to our observations of the excavations. If our observations reveal the need for deepening or re- designing foundation structures at any locations, any formwork or steel reinforcement in the affected footing excavation areas would have to be removed before the correction of the observed problem (i.e., deepening the footing excavation, compacting or removal of loose soil in the bottom of the excavation, etc.). 23. Construction Best Management Practices (BMPs): Sufficient BMPs must be installed to prevent silt, mud, or other construction debris from being tracked into the adjacent street(s) or stormwater conveyance systems due to construction vehicles or any other construction activity. The contractor is responsible for cleaning any such debris that may be in the street at the end of each workday or after a storm event that causes a breach in the installed construction BMPs. All stockpiles of uncompacted soil and/or building materials that are left unprotected for a period greater than 7 days are to be provided with erosion and sediment controls. Such soil must be protected each day when the probability of rain is 40% or higher. A concrete washout should be provided on all projects that propose the construction of any concrete improvements that are to be poured in place. All erosion/sediment control devices should be maintained and in working order at all times. All slopes that are created or disturbed by construction activity must be protected against erosion and sediment transport at all times. The storage of all construction materials and equipment must be protected against any potential release of pollutants into the environment. Hemlock Coastal Homes Residential Project Carlsbad, California X. GRADING NOTES Job No. 20-12842 Page 37 It is recommended that Geotechnical Exploration, Inc. be retained to verify that soil conditions revealed during grading for the project are as anticipated in this "Report of Preliminary Geotechnical Investigation." In addition, the compaction of any fill soils placed during grading must be observed and tested by our soil engineer. It is the responsibility of the general contractor to comply with the requirements on the approved plans and the local building ordinances. All/any retaining wall and trench backfill should be properly compacted. Geotechnical Exploration, Inc. will assume no liability for damage occurring due to improperly compacted or uncompacted backfill placed without our observations and testing. XI. LIMITATIONS Our conclusions and recommendations have been based on available data obtained from our field investigation, background review and laboratory analysis, as well as our experience with similar soils and natural ground materials located in the City of Carlsbad. Of necessity, we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is, therefore, necessary that all observations, conclusions, and recommendations be verified at the time excavation begins. In the event discrepancies are noted, additional recommendations may be issued, if required. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 38 The work performed and recommendations presented herein are the result of an investigation and analysis that meet the contemporary standard of care in our profession within the County of San Diego. No warranty is provided. This report should be considered valid for a period of two (2) years, and is subject to review by our firm following that time. If significant modifications are made to the wall plans, especially with respect to the height and location of the proposed wall structure, this report must be presented to us for immediate review and possible revision. As stated previously, it is not within the scope of our services to provide quality control oversight for surface or subsurface drainage construction or retaining wall sealing and base of wall drain construction. It is the responsibility of the contractor to verify proper wall sealing, geofabric installation, protection board installation (if needed), drain depth below interior floor or yard surfaces; pipe percent slope to the outlet, etc. It is the responsibility of the owner and/or developer to ensure that the recommendations summarized in this report are carried out in the field operations and that our recommendations for design of this project are incorporated in the project plans. We should be retained to review the final project plans once they are available, to verify that our recommendations are adequately incorporated in the plans. Additional or revised recommendations may be necessary after our review. This firm does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own. The safety of others is the responsibility of the Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 39 contractor. The contractor should notify the owner if any of the recommended actions presented herein are considered to be unsafe. The firm of Geotechnical Exploration, Inc. shall not be held responsible for changes to the physical condition of the property, such as addition of fill soils or changing drainage patterns, which occur subsequent to issuance of this report and the changes are made without our observations, testing, and approval. Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 20-12842 will expedite a reply to your inquiries. Respectfully submitted, .. S · eotechnical Engineer Cathy K. a e, Project Coordinator Senior ProJect Geologist e e D. Reed, President C.E.G. 999/P.G. 3391 REFERENCES JOB NO. 20-12842 August 2020 2007 Working Group on California Earthquake Probabilities, 2008, The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2), U.S Geological Survey Open-file Report 2007-1437 and California Geological Survey Special Report 203. Association of Engineering Geologists, 1973, Geology and Earthquake Hazards, Planners Guide to the Seismic Safety Element, Association of Engineering Geologists, Southern California Section. Berger, V. and Schug, D.L., 1991, Probabilistic Evaluation of Seismic Hazard in the San Diego-Tijuana Metropolitan Region, Environmental Perils, San Diego Region, Geological Society of America by the San Diego Association of Geologists, October 20, 1991, p. 89-99. County of San Diego, 2007, Guidelines for Determining Significance of Paleontological Resources, Land Use and Environment Group, Department of Planning and Land Use and Department of Public Works. p. 3-10. Crowell, J.C., 1962, Displacement Along the San Andreas, Fault, California, Geological Society of America, Special Papers, no. 71. Demere, T.A., 1997, Geology of San Diego County, California, San Diego Natural History Museum, http://archive.sdnhm.org/research/paleontology/sdgeol.html, accessed July 30, 2020. Grant Ludwig, L.B. and Shearer, P.M., 2004, Activity of the Offshore Newport-Inglewood Rose Canyon Fault Zone, Coastal Southern California, from Relocated Microseismicity. Bulletin of the Seismological Society of America, 94(2), 747-752. Greene, H.G., Bailey, K.A., Clarke, S.H., Ziony, J.I. and Kennedy, M.P., 1979, Implications of fault patterns of the inner California continental borderland between San Pedro and San Diego, in Abbott, P.L., and Elliot, W.J., eds., Earthquakes and other perils, San Diego region: San Diego Association of Geologists, Geological Society of America field trip, November, 1979, p. 21-28. Greensfelder, R.W., 1974, Maximum Credible Rock Accelerations from Earthquakes in California, California Division of Mines and Geology. Hart, E.W. and Bryant, W.A., 1997, Fault-Rupture Hazard Zones in California, California Division of Mines and Geology, Special Publication 42. Hart, E.W., Smith, D.P. and Saul, R.B., 1979, Summary Report: Fault Evaluation Program, 1978 Area (Peninsular Ranges-Salton Trough Region), California Division of Mines and Geology, Open-file Report 79-10 SF, 10. Hauksson, E. and Jones, L.M., 1988, The July 1986 Oceanside (ML=5.3) Earthquake Sequence in the Continental Borderland, Southern California Bulletin of the Seismological Society of America, v. 78, p. 1885-1906. Hileman, J.A., Allen, C.R. and Nordquist, J.M., 1973, Seismicity of the Southern California Region, January 1, 1932 to December 31, 1972; Seismological Laboratory, Cal-Tech, Pasadena, California. Hemlock Coastal Homes Residential Project Carlsbad, California Job No. 20-12842 Page 2 Kennedy, M.P. and Tan, S.S., 2007, Geologic Map of Oceanside 30'x60' Quadrangle, California, California Geological Survey, Department of Conservation. Richter, C.F., 1958, Elementary Seismology, W.H . Freeman and Company, San Francisco, California. Rockwell, T.K., 2010, The Rose Canyon Fault Zone in San Diego, Proceedings of the Fifth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. Paper No. 7.06C. Rockwell, T.K., Dawson, T.E., Young Ben-Horin, J. and Seitz, G., 2014, A 21-Event, 4,000-Year History of Surface Ruptures in the Anza Seismic Gap, San Jacinto Fault, and Implications for Long-term Earthquake Production on a Major Plate Boundary Fault. Pure and Applied Geophysics, v. 172, 1143- 1165 (2015). Rockwell, T.K., Millman, D.E., MCEiwain, R.S. and Lamar, D.L., 1985, Study of Seismic Activity by Trenching Along the Glen Ivy North Fault, Elsinore Fault Zone, Southern California: Lamar-Merifield Technical Report 85-1, U.S.G.S. Contract 14-08-0001-21376, 19 p. Ross, Z.E., Hauksson E. and Ben-Zion Y., 2017, Abundant Off-fault Seismicity and Orthogonal Structures in the San Jacinto Fault Zone, Science Advances, 2017; 3(3): e1601946. Published 2017 Mar 15. Toppozada, T.R. and Parke, D.L., 1982, Areas Damaged by California Earthquakes, 1900-1949, California Division of Mines and Geology, Open-file Report. 82-17. VICINITY MAP Thomas Guide San Diego County Edition pg 1106-E7 Hemlock Coastal Homes 320 Hemlock Avenue Carlsbad, CA. AQUA HEDIONDA LAGOON Figure No. I Job No. 20-12842 ~ ~ w ::, z ~ 0:: w n. z ::, -, 20 Scale: 1" = 20 ' (approximate) / _ ~'02_!)"~2499' _ \ FD. 3l4"IP WIDISC 'LS 5940• PER PM 12335. PM 16596 SURVEYOR'S STATEMENT z TH-5 WM' CORRECTl "( R.E~l::SEl(t S A SV-.:VE "f t.l.ADE BY ..-E. OR '-" ICfR MY DIREC'I lON u,i COIi ORMN'4·::E 'MTH TM!-REOJIRt Mlf fi ~ CF n--£ PRCFeSStOt,-'l VH.)S-.:qVEl'ORS .,CT Qr/ IOHC1 G.t.RY O UEUOIJ Pi.S 853i DATE PASCO LARET SUITER It ffe.SSOmA'11 ires Sari Diego I Solana Beach I Oranee County Phone 858.259.82121 www.plsaenglneert~com 20-12842-p.ai 30 TOPOGRAPHIC SURVEY MAP --320 HEMLOCK STREET PORLOl3 BLOCKR PALISADES #2 MAP 1803 N34'01'00"W 22999 ~r•33'JrE 23002'-PM 165961 PORL0l2 BLOCKR PI\LISADES#2 MAP 1803 -------1 l I I I I dA.C • .'l-.~,\,MOPn Plo\Y S1'{UC1U"'1---"'~ r L~GEND PORLOT3 BLOCKR PAI.ISAOES #2 MAP 1803 REFERENCE: This PLOT Pl.AN was prepared from an existing TOPOGRAPHIC SURVEY MAP by PASCO I.ARET SUITOR & ASSOCIATES date 08/05/2020 and from a CONCEPTUAL SITE Pl.AN by KIRK MOELLER ARCHITECTS, INC. dated 7/27/20 and from on-site field reconnaissance performed by GEi. E}(lSTING l S 10A'r aun.OCNG FD 314"IP Wlt:lSC "LS 5940" O 04' Sl. Y OF ,:;QRNER PER PM 16596, 0 5' ON N34•01•00-w 105.00' HP-2 ,,. ' I I I I I ~ I -I ~s! ~ I -.1~-~,-;,/.-5-------J / ~----,ii:: I CONC .;~-. . N34'01·00-w 105 00' ~•: iN34'33'3rE 10500'-PM 165l!6l \ PARCH 1 PM 16596 fAISllNG1 STORY BUrt.01,..G CONCEPTUAL SITE PLAN I I 1...---- ~HP-3 FD 3/4"IP, NO DISC, / 0 13'N'LY.0 31W'I FROM C,R SEE PN 16596 ~o~--. ~ 1z-rr: r 0~ ~~ ::i,•' l"~ I,, ;i GEOLOGIC LEG ND - •nn -25' ·-·-- ~ 1,,31, ~ c~rl ~ ~ftlTC s,nr OE ~ (.) ~ $1,f(" 0 r~ !ll'l _j :a Los.re w A915J't I 25' ~ HP-4 Approximate Location of Exploratory Handpit Qop 6-7 Quarternary Old Paralic Deposits (units 6 and 7) Approximate Location of Proposed Structure ~ r i ~ w 0 ~ 25' • T I ~ I NOTE: This Plot Plan is not to be used for legal purposes. Locations and dimensions are approximate. Actual property dimensions and locations of utilities may be obtained from the Approved Building Plans or the "As-Built" Grading Plans. • FOUND MONUMENT AS INDICATEO ( I RECORD BOUNDARY DATA AS INDICATED PROPERTY LINE RIGHT-Of-WAY LINE -----CENTER LINE -----ADJOINING PROPERTY LINE TIE UNE I REFERENCE LINE ---------EASEMENTUNE --OE ·--POWER· OVERHEAD --S --SANITARY. UTILITY MARKOUT -X--X -FSNCE "'•w.....-w·••• WALL BUILOING OUTLINE BUILDING OVERHANG INDEX CONTOJR UNE INTERMEDIATECQIIITOURLINE •M• SPOT ELEVATION 00( METER -WATER [El METER • ELECTRIC fo' METER·GAS fJ UTILITY POLE 0 CI.EANOUT @ MH • SIINIT ARY 6 MAILBOX TREE. DECIOUOUS TREE ·PALM TREE • CONIFEROUS VEGETATION F'F FINISHFLOOR RF ROOF PLOT PLAN Hemlock Coastal Homes 320 Hemlock Avenue Carlsbad, CA. Figure No. II Job No. 20-12842 ~ ~ Geotechnical Exploration, Inc. ( August 2020) ti C!l ...J a. ~ 0 LiJ C!l ~ C!l Cf) LiJ ::;; 0 I ...J r EQUIPMENT DIMENSION & TYPE OF EXCAVATION Hand Tools 2' X 2' X 4.5' Handpit SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH ± 56' Mean Sea Level Not Encountered = ., ~ ---' ::c 0 I-co a.. :a: w >-Cl en U.'•W• .. 1~·.:b_::,l -~·.:~--1 -··.··•.· ~-'i1J.. ~-·,.:,;-··, 1 -=~ - w ---' a.. :a: <( en 2 -II - - - -• FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size, Density, Moisture, Color) SILTY SAND. Loose. Dry. Light brown . TOPSOIL SIL TY SAND , fine-to medium-grained. Loose to medium dense. Dry to damp. Red-brown. WEATHERED OLD PARALIC DEPOSITS (Qop 6-7) --random roots to 3/16-inch in diameter to 4'. u:i cj u:i :::i SM SM DATE LOGGED 8-5-20 LOGGED BY CKG &'\3' C &= ~ w Cl~ :a:~ Cl c. WC!: ~~ ::a;- ::> ~ u ::> ::> ::> ~ ti; ~en :a: I-:a:--en -en a.. -a..Z I--~z ,o 'w a.. 0 ;?; :a: ~Cl o::a: :a:~ 3.1 101.1 -• X --21 % passing #200 sieve. 8.6 131.5 -• 3 I• -• -• I• 1 SIL TY SAND , fine-to medium-grained. Medium ,..Sritf dense. Damp. Orange-to red-brown. 6. 7 118.1 -I• • -1,~ -::x - - OLD PARALIC DEPOSITS (Qop d --18% passing #200 sieve. 8.6 129.8 4 -I• ~ -I• -I• 2 6.5 122.5 -I• - - - 5- -Bottom @ 4.5' - - - "I ~ :::!:! 0 ci ci i--: d~ ~cj + _j I.!: en wen z. 0 I----'W -:a: en s:z a.. ::c en_ <( zo a.. z 0 ::> ::a:u ~~ X 0 _.o c%s w u cou i.__ _ _,___...._____.__ ___________________ __.__.,__ _ _.__ _ __. __ 1-._ ......... _ ........ __ _.___...._______. ~ () "' () 0 ...J ::;; LiJ I ~ "' C!l g z 0 ~ g a. X LiJ '- y_ ~ IT] ■ ~ ~ PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE NUCLEAR FIELD DENSITY TEST STANDARD PENETRATION TEST JOB NAME Hemlock Coastal Homes SITE LOCATION 320 Hemlock Avenue, Carlsbad, CA JOB NUMBER REVIEWED BY LDR/JAC LOG No. 20-12842 cr,t;i-•-HP-1 FIGURE NUMBER Exploration, Inc. Illa ~ ~ 0 ~ ~ ti G ...J a. ril 0 w G iL G (/) w ::;; 0 I ...J i 0 "" 0 0 ...J ::;; w I ~ ~ G g z 0 ~ g a. X w r EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 4.25' Handpit 8-5-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 56' Mean Sea Level Not Encountered CKG FIELD DESCRIPTION AND £i: = ~ >-c-~ = CLASSIFICATION 0:: c.., ~ 0 g_ Q) w 0.9, w ~ w 0:: ~~ ::li: 0:: ::li:~ -' w ::::,~ ::c 0 -' DESCRIPTION AND REMARKS u:i <..)::::, ::::, ::::, :::5~ ::Sm ::li: I-::li:-I-CD a.. cj -en -en a.. ::li: ::li: (Grain size, Density, Moisture, Color) u:i a.. -a..z I--~z w >-<C ,o 'w a.. 0 ::li:~ 0 en (/) :::i ~::;; ~o o::;; o·•~· SILTY SAND. Loose. Very moist to wet. Dark SM ~-.~-::~ -:~·.:t2:· brown. -~:.:~:-:~ TOPSOIL -Wi --wet surface soils due to lawn irrigation; contact 1 _f i!;.~, ~ beween wet soils and drier soils ranges between f sfvf 12" to 24". -SIL TY SAND , fine-to medium-grained. Medium -dense. Damp to wet. Dark red-brown. -WEATHERED OLD PARAUC DEPOSITS (Qop -6-7) • 2-~SILTY SAND , fine-to medium-grained. Medium -s"Kf -dense. Damp. Orange-to red-brown. 4.9 104.3 -OLD PARALIC DEPOSITS (Qop d - 3 --1 3.8 115.2 -- - - 4--2 4.5 121.9 - - 5-Bottom @ 4.25' - - - _y JOB NAME PERCHED WATER TABLE Hemlock Coastal Homes ~ BULK BAG SAMPLE SITE LOCATION [I] IN-PLACE SAMPLE 320 Hemlock Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE 0 20-12842 1r.='•--NUCLEAR FIELD DENSITY TEST FIGURE NUMBER Exploration, Inc. ~ STANDARD PENETRATION TEST lllb ~ " 'I ~ 0 ci i-: ci ' d ~q + ~ _j en WW zg I--'W -::li: en_ c::z s:z a.. ::c zo o::::> ::li:<.:> ~c xo _,o c7i §, w <..) CD<..) LOG No. HP-2 .) ti (!) ...J a. ~ 0 w (!) ~ (!) en w ::;; 0 I ...J I >< 0 0 ...J ::;; w I N ;g ~ (!) g z 0 ~ g a. ~ rEQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED '- Hand Tools 2' X 2' X 4.5' Handpit SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH ± 56' Mean Sea Level Not Encountered ~ ,lg_ :::i:: I-a... UJ 0 -' 0 CD :::;; >-en E .. :?:.'~--;/6_·\~ -:~·.:~-, ~~:-:~-~~ ~-~-{~:-~ -~:~:- 1 _f4") ~:il·· t~J. -tf-J -~:~_::~ UJ -' a... :::;; <( en -.,;,,,..~ 2 :=.tf •ci.'~. -;~·-"i,d-\i :~:.-:4: -~-:~-> -.~ .. ~ 3 -{i!/~ -~:~. -~,:_;f.f/ -;~- ·~--~ FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size, Density, Moisture, Color) SIL TY SAND , with minor roots. Loose to medium dense (variable). Damp to moist. Dark brown to gray-brown. TOPSOIU AGRICULTURE TOPSOIL --23% passing #200 sieve. en cj en ::i SM -=tfJ 4 ----rri"n"rt"----t--=:-:-=::-7":;:-c-:-;-=-----,=-------,c-----:--:--------:----,--::-c-""""7.""----+-=-=-,-i SIL TY SAND , fine-to medium-grained. Medium SM dense. Damp. Orange-to red-brown. -2 -~ - -~ - - - - ~ • OLD PARALIC DEPOSITS (Qop d r- --variable density with some areas that more easily probe. ~~~----------------~ 5- -Bottom @4.5' - - - - - - JOB NAME 8-5-20 LOGGED BY CKG >-c ~-=-C 0:: <..> C 0 g_ UJ o.e, UJ UJ 0:: ~~ :::;; 0:: :::;;- ::::,~ (.) ::::, ::::, ::::, :s~ :s U) :::;; I-:::;;--en -en a...-a...z I--~m ,o ' UJ a...0 ~:::;; ~o o:::;; :::;;o 7.0 106.7 7.1 103.9 .Y PERCHED WATER TABLE Hemlock Coastal Homes ~ BULK BAG SAMPLE SITE LOCATION [I] IN-PLACE SAMPLE 320 Hemlock Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE 0 NUCLEAR FIELD DENSITY TEST 20-12842 ◄r.:,i--•lw FIGURE NUMBER Exploration, Inc. ~ STANDARD PENETRATION TEST Ille ~ "I ~ ,-.:: c:i c:i 0 ~cj + I.!,, ....i en LI.JU, z 0 I--' UJ -:::;; en s:z en_ <( a...:::i:: zo a... z o::::> :::;;u ~~ X 0 _,o <CZ UJ (.) CD U en= LOG No. HP-3 ~ (') g z 0 ~ g a. X w rEQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED '- Hand Tools 2' X 2' X 5.5' Handpit 8-5-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY I l-a.. w Cl 2 3 4 5 ± 56' Mean Sea Level Not Encountered FIELD DESCRIPTION AND CLASSIFICATION J wf--------------------~-4 g c[ DESCRIPTION AND REMARKS u:i ~ ! (Grain size, Density, Moisture, Color) SIL TY SAND , with organics and trash debris. Loose. Moist to wet. Dark brown. FILU TRASH PIT (Qaf) --pieces of broken glass and plates; bottles; some metal. --trash pit extends to 5 feet on north side of pit, terrace deposits encountered at 3 feet in south wall of excavation. --bottle just above 5'; large piece of metal, ~2.5 feet long, 6" wide, 1/2" thick, angled between 3 and 4 feet. SILTY SAND, fine-to medium-grained. Medium dense. Damp. Orange-to red-brown. JOB NAME (.) u:i ::i SM SM CKG g fi:::c.=-~ fi::: 'u w a~ w Cl c. we:: ~~ :::;; c:: :::;;- 0::, ::, ::, ::, ~ :'.5 I-:'.5 en :::;; I-:::;;--en -en a.. SQ a..z I--~z ,o 'w a.. 0 :::;;~ ~:::;; ~Cl 0~ 10.7 90.9 14.3 111.2 8.0 121.8 _y PERCHED WATER TABLE Hemlock Coastal Homes [8J BULK BAG SAMPLE SITE LOCATION [I] IN-PLACE SAMPLE 320 Hemlock Avenue, Carlsbad, CA ■ JOB NUMBER MODIFIED CALIFORNIA SAMPLE REVIEWED BY LDR/JAC ~ NUCLEAR FIELD DENSITY TEST 20-12842 C&-41' -•IW FIGURE NUMBER Exploration, Inc. ~ STANDARD PENETRATION TEST llld ~ "I ~ ~ ,...: ci ci 0-~q + _j b!:: en wen z 0 I-JW -~ en s;z a.. I en_ -=: zo a.. z o=> ::l:0 ~c X 0 JO u13e. w 0 mu LOG No. HP-4 ~ 13 5 13 0 12 5 120 115 110 13 Q. i ci5 m 105 0 >-0:: 0 100 95 90 85 80 75 0 \ \ • ~ I ,. 5 \ ' \ I \ \ ' Ii \ ' \ \ \ ' \ \ \ \\ ~ \ 411 \ ,\ \ \ \ \ \ \ I\ ' \ \ I I\ \ \ \ 10 15 Source of Material HP-1 @ 2.5' Description of Material SIL TY SAND {SM}1 Brown to Red-brown Test Method ASTM D1557 Method A \ \ \-., \ TEST RESULTS \ ' \ \ Maximum Dry Density 131.5 PCF \ Optimum Water Content _M % \ I\ \ \ ' \ I\ I\ Expansion Index (El) \ \ -- \ I\ \ \ \ "' \ \ \ \ " \ \ ' \ \ I\ \ II. Curves of 100% Saturation '\ ' for Specific Gravity Equal to: \ ' I\. \ \ ' 2.80 "' I\ ' \... \ \. 2.70 '\ \ I\. \... ' 2.60 \ \. '\. \.. I\. I\. \ II. \ \...' i\. " \ " ' \... i\. \... " \. \. \ ... \. \. " '\. \... ...... '\. "' -..,... I'-. "' ... r--... " "'i-.. " " \... " \... 20 25 30 35 40 45 13 5 13 0 12 5 12 0 115 110 '13 Q. ~ ci5 ct} 105 0 ~ 0 100 95 90 85 80 75 0 a if I/ 1• 5 \ ' i\ \ ~ \ \ 1 i\ ' \ 11,.' I \ ' \ . ,\ \ " \ \ \ \ l \ I,\: \ \ \ I\ \ I\ I I \ I\ \ \ \ \ \ \ \ ~ \ 10 15 Source of Material HP-1 @ 3.5' Description of Material SIL TY SAND (SM}1 Red-brown Test Method ASTM 01557 Method A \ \ TEST RESULTS \ 1 \ Maximum Dry Density 129.8 PCF r-\ ' \ \. Optimum Water Content 8.6 % r,. \ ~ \ \ I\ \ Expansion Index (El) I\ \ -- \ I\ ' I'\ \ t\. I\ \ \ \ "- I\ \ ' \ "' I\ \ "' Curves of 100% Saturation \ ' for Specific Gravity Equal to: \ I\ I\ I\ \ "' 2.80 I\ ' \ I\ I\ 2.70 '\ \ \. \ ' ' 2.60 \ \ '\. ' I\. I, '\ I\. I'\ 1\ ' ' I'\ " '\ I'\ " " "' ' I'\. ' ~ '\ \. " " '11o.. I"-" ""- I'\ I"-""- I'\ ' "~ I'-' ""' t"s. ' " '\ " 20 25 30 35 40 45 ........ ()M~ tAw< ~rt\"fl$"¥•~>flJ ~•i,tl1 _,,, 11~1 1r~ vse,s dogll;t1 _... oract1 101.<:i1 ,,_,. $.M 0"'71 jlJ • iO' ttlMK Q!Mdr~ ~ ~r--,cb.wftOfl t..'SGS t,,;,!M•.-1,ur 'h:J\J~'\ ~l;JJ1. l)tl&nr,,T b.,1',J"I0'1U ~• 11.'ld .. ...,,.d taftll'l~tr, !i~Jl,IOA• .. oi,.w'td~C.U 1-'rG«'_p')O'jlfUf~• IMf,•• !'1t>111'1AIMf'Ul"10a~1911 Tl 1, •••W 'J0.1i. lur4 .. J,,, i_. ti; t"I• 1;$ ~ .t St,c.-.,,,..,:.,-.....itoc,r -.. ~~ 1., .. -,]P-t..,;r,,.., S,fAltJ;f.,lp 1'•..,.t"' ,-.: .... :'-'G~~-'i;, F"ttjM>t:-: II' W00tf»IO'I lr1f', lllif ~I:;, (_>41;.,t .,;,r.,, &:11'"""°1 s,....,.,....,~,._,,.,~~P,.,.,- c.p,,,,q-, Xl08t,,NCa~Ut1»1'nftltdeo----,,.10 A,l~'j,fMlol'..0 ..,:;,e,tfi'.-...Pl,A!)k.,il'°"INl"{Nr.~ -',!Ty,_.• •Ml.., ,~•(tf,_CMlon-...~.al C.,., •• 11111 0.0.""-"tl t/'°"""",i,v,n ... •~--MJ,...,,_..,,..,., u1ur-. _..,..,. •• ~lh,tploo.otllc,. l'I')-,,_.'11tl.f1t• pv;io,t,,, Hemlock-2008-geo.ai Hemlock Coastal Homes 320 Hemlock A venue Carlsbad, CA. EXCERPT FROM GEOLOGIC MAP OF THE OCEANSIDE 30' x 60' QUADRANGLE, CALIFORNIA Compiled by 1 l --.. ,. 111 . Ell l' ~ "" ~ ., •" • Michael P. Kennedy1 and Siang S. Tan 1 2007 Digital preparation by Kelly R. Bovard', Rachel M. Alvarez1, Michael J. watson', and Carlos I. Gutierrez' 1 ~~ol~~ C.fflrNOHfQIIC815',r,.., , US'-cioo,c.!Sur,,,tr~.,.,teflE~~-~JcfC'alr,.,hitR,,,,tt•d• ONSHORE MAP SYMBOLS 1-·aull ~lid Wh:N ~~,-u.r:ntly locateJ; dulltd \\.hm IPf{\'.IXU'lutd)· localed. dotttd whac ,'l.'llcnkd.. tJ u~n bl-xl O d.-iwRtltrl~n blod~. Am-.· and Nnbn indic-.ilt dir,..1;,.., and '"'fie of dir ofliwll pl,ri,_ l,■ndslldr-AJ ru1ri,i: inJkak f'l'lJ•dral daro.1il1l 01· ll'k"-<Meld.. ()lkrit-J -. hm t~ctll.c ls (llk'i>tfrti.ablt. Slrlkt and dip ofbffls l1'<11•od Onrlurnt'd \frlkal llorl1J1Jnlal S.rlkt and dip orltMOMJ fotlat:lon hac11n,d \"trHtat Strlk• and dip or q:neou, Joints lndlntd \C'rUut Slrlb and lll1• (If Dldamorphlt r..,nuhm lndlntd Slrlkf. al'tl dip ~r udlmtrtlary joint.. \frtlul DESCRIPTION OF MAP UNITS Units 6-7 Old paralic deposits, undivided Figure No. V Job No. 20-12842 -~••~c-§: ~ August 2020 APPENDIX A UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION Coarse-grained (More than half of material is larger than a No. 200 sieve) GRAVELS, CLEAN GRAVELS (More than half of coarse fraction is larger than No. 4 sieve size, but smaller than 3") GRAVELS WITH FINES (Appreciable amount) SANDS, CLEAN SANDS (More than half of coarse fraction is smaller than a No. 4 sieve) SANDS WITH FINES (Appreciable amount) GW Well-graded gravels, gravel and sand mixtures, little or no fines. GP Poorly graded gravels, gravel and sand mixtures, little or no fines. GC Clay gravels, poorly graded gravel-sand-silt mixtures SW Well-graded sand, gravelly sands, little or no fines SP Poorly graded sands, gravelly sands, little or no fines. SM Silty sands, poorly graded sand and silty mixtures. SC Clayey sands, poorly graded sand and clay mixtures. Fine-grained (More than half of material is smaller than a No. 200 sieve) SIL TS AND CLAYS Liquid Limit Less than 50 liquid Limit Greater than 50 HIGHLY ORGANIC SOILS ML Inorganic silts and very fine sands, rock flour, sandy silt and clayey-silt sand mixtures with a slight plasticity CL Inorganic clays of low to medium plasticity, gravelly clays, silty clays, clean clays. OL Organic silts and organic silty clays of low plasticity. MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. CH Inorganic clays of high plasticity, fat clays. OH Organic clays of medium to high plasticity. PT Peat and other highly organic soils APPENDIX B U SGS SITE S P ECIFIC SEISM IC DESIGN PARAMETERS APPENDIX B OS HPD 320 Hemlock Avenue Latitude, Longitude: 33.1505, -117.3440 .:i,e '"'~ <,\~ ~c,'3' ' Tamarack D \)-,.:i.e Surf Beach T\ e,~e~~ ' ' ' ' Pure Beach Living 9 ' ' ' ' ' ' ~acific Carlsbad Gondominiums ' ,,. ., ' , ' ., \ \ Go gle Date Design Code Reference Document Risk Category Site Class Type Ss Value 1.091 0.394 1.161 9 \ \ Elan Tamarackft Shores Apartments T Description 8/24/2020, 12:34:56 PM ASCE7-16 II D -Stiff Soil MCER ground motion. (for 0.2 second period) S1 SMs SM1 Sos So1 null-See Section 11.4.8 !0. 749 I 0.774 MCER ground motion. (for 1.0s period) Site-modified spectral acceleration value Site-modified spectral acceleration value Numeric seismic design value at 0.2 second SA Numeric seismic design value at 1.0 second SA null-See Section 11.4.8 !0.499! Type Value Description SDC null -See Section 11.4.8 ~ Seismic design category Fa 1.064 Site amplification factor at 0.2 second Fv null -See Section 11.4.8! l. 90 !Site amplification factor at 1.0 second PGA 0.482 FPGA 1.118 PG~ 0.539 TL 8 SsRT 1.091 SsUH 1.222 SsD 1.5 S1RT 0.394 S1UH 0.435 S1D 0.6 PGAd 0.594 CRs 0.893 CR1 0.904 MCEG peak ground acceleration Site amplification factor at PGA Site modified peak ground acceleration Long-period transition period in seconds Probabilistic risk-targeted ground motion. (0.2 second) Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration Factored deterministic acceleration value. (0.2 second) Probabilistic risk-targeted ground motion. (1 .0 second) Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration. Factored deterministic acceleration value. (1.0 second) Factored deterministic acceleration value. (Peak Ground Acceleration) Mapped value of the risk coefficient at short periods Mapped value of the risk coefficient at a period of 1 s \ Map data ©2020