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MS 2021-0002; JUNIPER BEACH HOMES; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION; 2021-01-07
REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Juniper Avenue Residential Project 295 Juniper Avenue Carlsbad, California JOB NO. 20-13022 7 January 2021 Prepared for: Mr. Kevin Dunn Rincon Homes D ~-G e ote chnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 7 January 2021 RINCON HOMES 5315 Avenida Encinas, Suite 200 Carlsbad, CA 92008 Attn: Mr. Kevin Dunn Job No. 20-13022 Subject: Report of Preliminary Geotechnical Investigation Juniper Avenue Residential Project 295 Juniper Avenue Carlsbad, California Dear Mr. Dunn: In accordance with your request, and our proposal of November 18, 2020, Geotechnical Exploration, Inc. has performed a preliminary geotechnical investigation for the subject project in Carlsbad, California. The field work was performed on December 14, 2020. If the conclusions and recommendations presented in this report are incorporated into the design and construction of the proposed four three-story, single family residences with attached garages, and associated improvements, it is our opinion that the site is suitable for the proposed 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. 20-13022 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. neer R.C.E. 34422/G.E. 2007 ~.6.:£ C.E.G. 999/P.G. 3391 7420 TRADE STREIT• SAN DIEGO, CA. 92121 • (858} 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gel-sd.com TABLE OF CONTENTS I. PROJECT SUMMARY ............................................................................ 1 II. SCOPE OF WORK ................................................................................ 2 III. SITE DESCRIPTION ............................................................................. 2 IV. FIELD INVESTIGATION, OBSERVATIONS & SAMPLING .............................. 3 V. LABORATORY TESTING & SOIL INFORMATION ........................................ 4 VI. REGIONAL GEOLOGIC DESCRIPTION ..................................................... 8 VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION ................................... 13 VIII. GEOLOGIC HAZARDS ........................................................................ 14 A. Local and Regional Faults ........................................................... 15 B. Other Geologic Hazards ............................................................. 21 IX. GROUNDWATER ............................................................................... 24 X. CONCLUSIONS & RECOMMENDATIONS ................................................ 26 A. Preparation of Soils for Site Development ..................................... 27 B. Seismic Design Criteria .............................................................. 36 C. Foundation Recommendations .................................................... 37 D. Concrete Slab On-Grade Criteria ................................................. 39 E. Retaining Wall Design Criteria ..................................................... 44 G. Pavements .............................................................................. 45 H. Site Drainage Considerations ...................................................... 46 I. General Recommendations ......................................................... 48 XI. GRADING NOTES .............................................................................. 49 XII. LIMITATIONS ................................................................................... 50 REFERENCES FIGURES I. II. IIIa-e. IVa-d. V. Vicinity Map Plot Plan and Site-Specific Geologic Map Exploratory Excavation Logs and Laboratory Results Laboratory Test Results Geologic Map Excerpt and Legend APPENDICES A. Unified Soil Classification System B. ASCE Seismic Summary Report Bi REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Juniper Avenue Residential Project 295 Juniper Avenue Carlsbad, California JOB NO. 20-13022 The following report presents the findings and recommendations of Geotechnical Exploration, Inc. for the subject project. I. PROJECT SUMMARY It is our understanding, based on our review of the available conceptual plans prepared by Stephen Dalton Architects, Inc., and the topographic survey by Pasco Laret Suiter and Associates, that the existing residential structures and associated improvements are to be entirely demolished and replaced with four (4), three-story, residential structures with attached garages and associated improvements. The new structures are to be constructed of standard-type building materials utilizing conventional foundations with concrete slab on-grade. Foundation loads are expected to be typical for this type of relatively light construction. A preliminary site plan by Stephen Dalton Architects, Inc., dated November 3, 2020, has been reviewed by us and used to understand the scope of the project. When final plans are completed, they should be made available for our review. Additional or modified recommendations will be provided at that time if warranted. Based on the available information at this stage, it is our opinion that the proposed site development would not destabilize neighboring properties or induce the settlement of adjacent structures or improvements if designed and constructed in accordance with our recommendations. Juniper Avenue Residential Project Carlsbad, California II. SCOPE OF WORK Job No. 20-13022 Page 2 The scope of work performed for this investigation included a site reconnaissance and subsurface exploration program under the direction of our geologist with placement, logging and sampling of five exploratory excavations, review of available published information pertaining to the site geology, 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 design and construction criteria for the project earthwork, building foundations, slab on-grade floors and associated improvements. III. SITE DESCRIPTION The lot is known as Assessor's Parcel No. 204-240-32-00, a portion of Lot 2 of Block R of Palisades No. 2, according to Recorded Map No. 1803, with a current address of 295 Juniper Avenue, in the City of Carlsbad, County of San Diego, State of California. Refer to Figure No. I, Vicinity Map, for the site location. For purposes of this report the front of the lot faces northwest on to Juniper Avenue. The rectangular-shaped lot is approximately 11,000 square feet and is bordered on the northeast and southeast by similar residential properties, to the southwest by a two-story residential development, and on the northwest by Juniper Avenue. Refer to the Plot Plan, Figure No. II. The existing property is currently developed with three single-story, residential structures, an asphalt and dirt parking area, landscape areas and associated improvements. Vegetation on the site primarily consists of lawn grass, shrubbery, and mature trees. Ii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 3 The property is relatively level ranging from approximately 56 feet above Mean Sea Level (MSL) along the southeastern (rear) property line to approximately 58 feet above MSL at the northwestern (front) property line. Survey information concerning elevations across the site was obtained from a topographic survey map of the site prepared by Pasco Laret Suiter, dated November 3, 2020. IV. FIELD INVESTIGATION, OBSERVATIONS & SAMPLING The field investigation was conducted on December 14, 2020, and consisted of surface reconnaissance and a subsurface exploration program utilizing hand- excavated exploratory test pits to investigate and sample the subsurface soils. Five (5) exploratory trenches (HP-1 to HP-5) were excavated to a maximum depth of 3 feet in the areas of the proposed development and associated improvements. The excavations revealed that the building site is underlain by up to approximately 1 foot of loose to medium dense, silty sand fill soil/topsoil over medium dense to dense, silty sand formational materials. The upper 1 foot of the formational materials are weathered. The soils encountered in the exploratory trenches are considered to have a low expansion potential with an Expansion Index of less than 50. The exploratory excavations were continuously logged in the field by our geologist and described in accordance with the Unified Soil Classification System (refer to Appendix A). The approximate locations of the exploratory trenches are shown on the Plot Plan, Figure No. II. Representative samples were obtained from the exploratory handpits at selected depths appropriate to the investigation. Relatively undisturbed chunk and drive samples and disturbed bulk samples were collected from the exploratory pits to aid in classification and for appropriate laboratory testing. The samples were returned to our laboratory for evaluation and testing. Exploratory handpit logs have been Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 4 prepared on the basis of our observations and laboratory test results, and are attached as Figure Nos. Illa-e. The exploratory handpit logs and related information depict subsurface conditions only at the specific locations shown on the plot plan and on the particular date designated on the logs. Subsurface conditions at other locations may differ from conditions occurring at the locations. Also, the passage of time may result in changes in subsurface conditions due to environmental changes. V. LABORATORY TESTING & SOIL INFORMATION Laboratory tests were performed on retrieved soil samples in order to evaluate their physical and mechanical properties. The test results are presented on Figure Nos. Illa-e and IVa-c. The following tests were conducted on representative soil samples: 1. Moisture Content (ASTM D2216-19) 2. Density Measurements (ASTM D2937-17e2) 3. Standard Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures using Coated Samples (ASTM D1188-07) 4. Laboratory Compaction Characteristics (ASTM D1557-12e1) 5. Determination of Percentage of Particles Smaller than #200 Sieve (ASTM D1140-17) 6. Resistivity and pH Analysis (Department of Transportation California Test 643) 7. Water Soluble Sulfate (Department of Transportation California Test 417) 8. Water Soluble Chloride (Department of Transportation California Test 422) Moisture content and density measurements were performed by ASTM methods D2216-19 and D2937-17e2 respectively, in conjunction with D1188-07 to establish Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 5 the in-situ moisture and density of samples retrieved from the exploratory handpits. Measurements were also performed by ASTM method D1188-07, the bulk specific gravity utilizing paraffin-coated specimens. This method helps to establish the in- situ density of chunk samples retrieved from the exploratory excavations. The test results are presented on the handpit logs at the appropriate sample depths and laboratory test results. Laboratory compaction values (ASTM D1557-12el) 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 site soils and the soil compaction conditions to be anticipated during any future grading operation. The test results are presented on the handpit logs at the appropriate sample depths and laboratory test results. The particle size smaller than a No. 200 sieve analysis (ASTM D1140-17) aids in classifying the tested soils in accordance with the Unified Soil Classification System and provides qualitative information related to engineering characteristics such as expansion potential, permeability, and shear strength. The test results are presented on the handpit logs at the appropriate sample depths and laboratory test results. The expansion potential of soils is determined, when necessary, utilizing the Standard Test Method for Expansion Index of Soils (ASTM D4829-19). In accordance with the Standard (Table 5.3), potentially expansive soils are classified as follows: EXPANSION INDEX POTENTIAL EXPANSION Oto 20 Very low 21 to 50 Low 51 to 90 Medium 91 to 130 High Above 130 Very hiqh Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 6 Based on our visual classification, our laboratory sieve analysis of representative samples and our past experience with similar soils, it is our opinion that the existing fill and formational materials of the Old Paralic Deposits, Units 6-7, encountered in the handpits possess a very low to low potential for expansion. Therefore, we have assigned a maximum expansion index of less than 50 to these soils. To assess soil corrosivity of the on-site soils, resistivity, pH, chloride and soluble sulfate tests were performed by an outside consultant (Clarkson Laboratory and Supply Inc.), on samples of the near surface soils most likely to be in contact with concrete and ferrous metals. The most common factor in determining soils corrosivity to ferrous metals is electrical resistivity. As soil's resistivity decreases, its corrosivity to ferrous metals increases. The tested soils yielded resistivities of 11,000 and 6,800 Ohm-cm indicating that the soils are mildly to moderately corrosive to ferrous metals. Soils and fluids are considered neutral when pH is measured at 7, acidic when pH is measured at <7 and alkaline when measured at > 7. Soils are considered corrosive when the pH gets down to around 5.5 or less. Results of the laboratory testing yielded pH values of 7 .5 and 7 .6, indicating that the tested soils range from slightly acid to slightly alkaline, indicating that pH is not a significant factor in soil corrosivity to metals. Large concentrations of chlorides will adversely affect any ferrous metals such as iron and steel. Soil with a chloride concentration greater than or equal to 500 ppm (0.05 percent) or more is considered corrosive to ferrous metals. The chloride content of the tested soils measured at approximately 30 and 10 ppm or 0.003 and 0.0010 percent respectively, indicating that chloride is not a major factor in corrosion to ferrous metals. :;i Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 7 The primary cause of deterioration of concrete in foundations and other below ground structures is the corrosive attack by soluble sulfates present in the soil and groundwater. The results of water-soluble sulfate testing performed on a representative sample of the near surface soils in the general area of the proposed structures, yielded soluble sulfate contents of less than 30 ppm or 0.003 percent, indicating that the proposed cement-concrete structures that are in contact with the underlying soils are anticipated to be affected with a negligible sulfate exposure. As such, there is no restriction on selection of cement type. The table below summarizes the laboratory results for chemical testing of the sampled soils: Sample Soluble Soluble Soil Location/ pH Sulfate Chloride Resistivity Depth, (ft) (PPM) (PPM) (Ohm-cm) HP-1 @ 1'-2' 7.5 <30 10 11,000 HP-2@ 3' 7.6 <30 10 6,800 For laboratory testing results refer to Figure Nos. IVc-d It should be noted that Geotechnical Exploration Inc., does not practice corrosion engineering and our assessment here should be construed as an aid to the owner or owner's representative. A corrosion specialist should be consulted for any specific design requirement. 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 IA Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 8 the project. The assumed soil strength values have been utilized in determining the recommended bearing value as well as active and passive earth pressure design criteria for foundations and retaining walls. The assumed strength values for properly compacted fill and for dense formational soils are 33 degrees and cohesion equal to 50 psf, as well as total unit weight of 120 pcf, based on the visual inspection of the soils and our experience. With these values we calculated the ultimate bearing capacity of the soil to be 9,285 psf by Terzaghi's equation. This value was reduced with a factor of safety of 3 to calculate the allowable bearing capacity of 3,095 psf, which has been reduced to the nominal recommended value of 2,500 psf. The active and passive pressure of the soils were calculated with Terzaghi's equations for those pressures and neglecting the cohesion contribution to values of 35.4 pcf and 407 pcf. We have increased the active soil pressure to 38 pcf, and the passive soil pressure was reduced to 275 pcf. The calculated friction coefficient of 0.649 has been reduced to an allowable value of 0.35. VI. 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. 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 81 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 9 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 Range 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 formed 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). 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 ~ Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 10 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 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 Ii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 11 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 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, although 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 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 12 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. 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. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 13 VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION Our field investigation, reconnaissance and review of the geologic map by Kennedy and Tan, 2007, "Geologic Map of the Oceanside 30'x60' Quadrangle, California" indicate that the site is underlain by late to middle Pleistocene-Aged Old Paralic Deposits, Units 6-7 (QOP6-7) formational materials. An excerpt of the geological map is included as Figure No. V. Our exploratory excavations indicate the formational materials are overlain across the site by shallow-depth fill soils (Qaf) and topsoil. Site-specific geology is shown on the Plot Plan, Figure No. II. Fill Soil/Topsoil (Oaf): Our site investigation indicates that the areas in the general vicinity of our exploratory trenches at the site are overlain by up to 12-inches of fill soil and topsoil. The encountered fill soil/topsoil consists of fine-to medium-grained, dry to damp, gray-brown to red-brown, silty sand (SM) with variable amounts of roots. The fill soils/ topsoils are generally loose. In our opinion, due to the variable density and poor condition of the fill soil/topsoil, it is not considered suitable in its current condition to support loads from structures or additional fill. Refer to Figure Nos. IIIa-e for details. Residual Soil/Subsoil: Residual/Subsoil was encountered underlying the fill soils in all the exploratory trenches. The approximate thickness of these soils was observed to vary from approximately 0.5 to 3 feet in thickness. These soils were noted to consist mainly of damp, light-brown, silty sands (SM). This material was observed to be generally loose to medium dense, porous and with some deeper roots. In our opinion, due to the low density and potential compressibility of these porous soils, these residual soils are not considered suitable to support loads from structures or additional fill in their current condition. Refer to Figure Nos. IIIa-e for details. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 14 Old Paralic Deposits, Unit 6-7 (Oop6-7)_;_ The encountered formational materials are described in the literature as Quaternary (late to middle Pleistocene) Old Paralic Deposits, Units 6-7. These formational materials were encountered in all trenches underlying the fill soil/ topsoil at variable depths from 1 to 2 feet. The formational materials consist of medium dense to dense, fine-to medium-grained, damp to moist, orange-and red-brown silty sand (SM) with areas of moderate cementation and some deeper roots. The upper 1 to 1.5 feet is weathered. In our opinion, the medium dense to dense nature of the Old Paralic Deposits, Units 6-7, makes it suitable in its current condition to support loads from structures or additional fill. Refer to Figure Nos. Illa-e for details. Based on our review of the geologic map by Kennedy and Tan, 2007, "Geologic Map of the Oceanside 30'x60' Quadrangle, California" the Old Paralic Deposits, Units 6-7, formational materials underlie the entire site at depth. The aforementioned Old Paralic Deposit Units are described as "Poorly sorted, moderately permeable, reddish- brown, interfingered strandline, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate." According to the map, there are no faults known to pass through the site (refer to Figure No. V, Geologic Map Excerpt and Legend). VIII. GEOLOGIC HAZARDS The following is a discussion of the geologic conditions and hazards common to this area of Carlsbad, as well as project-specific geologic information relating to development of the subject site. r, Juniper Avenue Residential Project Carlsbad, California A. Local and Regional Faults Job No. 20-13022 Page 15 Reference to the Geologic Map and Legend, Figure No. V (Kennedy and Tan, 2007), indicates that no faults are shown to cross the site. Furthermore, our site reconnaissance presented no indications of faulting crossing the site. In our professional opinion, neither an active fault nor a potentially active fault underlies the site. A brief description of the nearby active faults including distances from the mapped fault to the subject site at the closest point (based on the USGS Earthquake Hazards- Interactive Fault Map), is presented below: Newport-Inglewood-Rose Canyon Fault Zone System: The Oceanside section of the Newport-Inglewood-Rose Canyon Fault Zone is mapped approximately 4.3 miles west-southwest of the site. The offshore portion of the Newport-Inglewood Fault Zone is described as a right-lateral; local reverse slip associated with fault steps (SCEDC, 2020); the reported length is 46.2 miles extending in a northwest-southeast direction. Surface trace is discontinuous in the Los Angeles Basin, but the fault zone can easily be noted there by the existence of a chain of low hills extending from Culver City to Signal Hill. South of Signal Hill, it roughly parallels the coastline until just south of Newport Bay, where it heads offshore, and becomes the Newport- Inglewood -Rose Canyon Fault Zone. 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/yr 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). Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 16 Rose Canyon Fault Zone: The Rose Canyon Fault Zone is the southern section of the Newport-Inglewood-Rose Canyon Fault Zone system mapped in the San Diego County area as trending north-northwest to south-southeast from Oceanside to La Jolla and generally north-south into San Diego Bay, through Coronado and offshore downtown San Diego, from where it appears to head southward. The Rose Canyon Fault Zone system is considered to be a complex zone of onshore and offshore, en echelon right lateral, strike slip, oblique reverse, and oblique normal faults. This fault is considered to be capable of generating an M7.2 earthquake and is considered microseismically 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 and Bryant, 1997). Rockwell (2010) has suggested that the Rose CFZ 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 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 to 2 mm/year. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 17 Coronado Bank Fault: The Coronado Bank Fault is located approximately 22.6 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 et al., 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. San Diego Trough Fault Zone: The San Diego Through Fault Zone is mapped at approximately 29.6 miles to the west-southwest of the site at its closest point. This fault is described as a right-lateral type fault with a length of at least 93.2 miles and a slip rate of roughly 1.5 mm/yr. The most recent surface rupture is of Holocene age (SCEDC, 2020). San Clemente Fault Zone: The San Clemente Fault Zone is mapped at approximately 56 miles to the southwest of the site at its closest point. This fault is described as a right-lateral and vertical offsets type fault with a length of at least 130.5 miles described as essentially continuous with the San Isidro fault zone, off the coast of Mexico and a slip rate of roughly 1.5 mm/yr. The most recent surface rupture is of Holocene age (SCEDC, 2020). Elsinore Fault: The Temecula and Julian sections of the Elsinore Fault Zone are located approximately 23.5 and 33 miles northeast and east of the site respectively. The Elsinore Fault Zone extends approximately 125 miles from the Mexican border to the northern end of the Santa Ana Mountains. The Elsinore Fault zone is a 1-to at Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 18 4-mile-wide, northwest-southeast-trending zone of 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 with a magnitude as large as M7.5. Study and logging of exposures 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 earthquake magnitudes of M6.0 to M7.0 (Rockwell et al., 1985). The Working Group on California Earthquake Probabilities (2008) has estimated that there Iii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 19 is a 11 percent 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 approximately 46 to 66 miles 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 (Rockwell et al., 2014). 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 (Ross et al., 2017). 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/yr for the northern segments of the fault, and slip rates of 4 ±2 mm/yr 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 (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 expected r, Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 20 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. 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 4th of April 2010, Easter Sunday, 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 12th 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 Caltech/USGS Southern California Seismic Network and a GPS network of more than 100 stations. at Juniper Avenue Residential Project Carlsbad, California B. Other Geologic Hazards Job No. 20-13022 Page 21 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 were 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, Coronado Bank or Newport-Inglewood Faults. Although the chance of such an event is remote, it could occur within the useful life of the structure. Landslides: Our investigation indicates that the subject site is not directly on a known recent or ancient landslide. Review of the "Geologic Map of the Oceanside 30'x60' Quadrangle, California" by Kennedy and Tan (2007) and the USGS Landslide Hazard Program Site (US Landslide Inventory), indicate that there are no known or suspected ancient landslides located on the site. 111 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 22 Slope Stability: Our site reconnaissance indicates that the site is relatively level and underlain by relatively stable and dense Old Paralic Deposits, Unit 6-7 formational materials at depths of approximately 1 to 3 feet. In our opinion, there is not a slope stability issue with the site. 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, cohesionless saturated silt, sand, and fine-grained gravel deposits of Holocene to late Pleistocene age and in areas where the groundwater is shallower than about 50 feet (DMG Special Publication 117) when they are sufficiently shaken by an earthquake. On this site, the risk of liquefaction of formational materials due to seismic shaking is considered to be very low due to the dense to very dense nature of the underlying formational materials and the lack of shallow static groundwater. The site does not have a potential for soil strength loss to occur due to a seismic event. Tsunamis and Seiches: 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, meteor 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. at Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 23 The site is located approximately 0.17-mile from the exposed coastline and at an elevation of approximately 55 to 56 feet above MSL. Review of the Tsunami Inundation Map for Emergency Planning, Encinitas Quadrangle, the site is located outside the inundation area. There is no risk of tsunami inundation at the site. A seiche is a run-up of water within a lake or embayment triggered by fault-or landslide-induced ground displacement. The site is located near a coastal lagoon, that is not considered capable of producing a seiche and inundating the subject site. Flood Hazard: Review of the FEMA flood maps number 06073C0764H, effective on 12/20/2019, the project site is located within the Special Flood Hazard Area (SFHA) X. Zone X is described as minimal flood hazard. The civil engineer should verify this statement with the City of Carlsbad and County of San Diego (FEMA, 2019). Geologic Hazards Summary: It is our opinion, based upon a review of the available maps, our research and our site investigation, that the site is underlain at shallow depth by stable Old Paralic Deposits formational materials and is suited for the proposed residential structures and associated improvements provided the recommendations herein are implemented. Furthermore, based on the available information at this stage, it appears the proposed site development will not destabilize or result in settlement of adjacent property or improvements if the recommendations presented in this report are implemented. No significant geologic hazards are known to exist on the site that would prohibit the construction of the proposed residential structures, retaining walls and associated improvements. Ground shaking from earthquakes on active southern California faults and active faults in northwestern Mexico is the greatest geologic hazard at the Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 24 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. IX. GROUNDWATER Free groundwater was not encountered in our exploratory excavations to the maximum depths explored. For a more detailed description of the subsurface materials encountered in our exploratory excavations refer to Figure Nos. IIIa-e. It should be recognized that minor groundwater seepage problems might occur after development of a site even where none were present before development. These are usually minor phenomena and are often the result of an alteration in drainage patterns and/or an increase in irrigation water. Based on the permeability characteristics of the soil and the anticipated usage and development, it is our opinion that any seepage problems, which may occur, will be minor in extent. It is further our opinion that these problems can be most effectively corrected on an individual basis if and when they occur. We do not anticipate significant groundwater problems to develop in the future, if the property is developed as proposed and proper drainage is implemented and maintained. BJ Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 25 It should be kept in mind that any required construction operations will change surface drainage patterns and/or reduce 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 damage from 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. On properties such as the subject site where dense, low permeability soils exist at shallow depths, even normal landscape irrigation practices on the property or neighboring properties, or periods of extended rainfall, can result in shallow "perched" water conditions. The perching (shallow depth) accumulation of water on a low permeability surface can result in areas of persistent wetting and drowning of lawns, plants and trees. Resolution of such conditions, should they occur, may require site-specific design and construction of subdrain and shallow "wick" drain dewatering systems. It must be understood that unless discovered during site exploration or encountered during site construction operations, it is extremely difficult to predict if or where perched or true groundwater conditions may appear in the future. When site fill or 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, 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. D Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 26 Proper functional surface drainage should be implemented and maintained at the property. X. CONCLUSIONS & RECOMMENDATIONS The following recommendations are based upon the practical field investigations conducted by our firm, and resulting laboratory tests, in conjunction with our knowledge and experience with similar soils in the Carlsbad area. 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. We recommend that the planned residential structures be supported by conventional, individual-spread and/or continuous footing foundations founded on medium dense to dense formational soils and minimum 90 percent compacted structural fill soils. Individual structures may bear on dense formational or fill soils depending on their locations, final grading elevations and exposure of formational materials. Existing fill soils/topsoils across the entire site will be disturbed during the demolition of the existing structures, and are not suitable in their current condition to support Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 27 new structures or associated improvements. A full removal and recompaction of existing fill and topsoils across the site will be required to support the proposed structures and associated improvements. New fill soils across the site will be required to be compacted to at least 90 percent relative compaction. Existing fill soil and formational materials are suitable for use as recompacted fill soils. Any buried trash and roots encountered during site demolition and fill soil recompaction should be removed and exported off site. It is our opinion that the site is suitable for the planned residential project provided the recommendations herein are incorporated during design and construction. A. Preparation of Soils for Site Development 1. General: Grading should conform to the guidelines presented in the 2019 California Building Code (CBC, 2019), as well as the requirements of the City of Carlsbad. During earthwork construction, removals and reprocessing of fill materials, as well as general grading procedures of the contractor should be observed and the fill placed selectively tested by representatives of the geotechnical engineer, Geotechnical Exploration Inc. If any unusual or unexpected conditions are exposed in the field, they should be reviewed by the geotechnical engineer and if warranted, modified and/or additional remedial recommendations will be offered. Specific guidelines and comments pertinent to the planned development are provided herein. The recommendations presented herein have been completed using the information provided to us regarding site development. If information ~ Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 28 2. concerning the proposed development is revised, or any changes are made in the design and location of the proposed property, they must be modified or approved in writing by this office. Clearing and Stripping: Complete demolition of the existing residential structures and associated improvements should be undertaken. This is to include the complete removal of all subsurface footings, utility lines and miscellaneous debris. After clearing the entire ground surface of the site should be stripped of existing vegetation within the areas of proposed new construction. This includes any roots from existing trees and shrubbery. Holes resulting from the removal of root systems or other buried obstructions that extend below the planned grades should be cleared and backfilled with suitable compacted material compacted to the requirements provided under Recommendation Nos. 3, 4 and 5 below. Prior to any filling operations, the cleared and stripped vegetation and debris should be disposed of off-site. 3. Excavation: After the entire site has been cleared and stripped, all of the existing fill soils and topsoil should be removed and recompacted. The depth of removals across the site will vary depending on the thickness of unsuitable soils overlying the formational materials. It is anticipated that the depth of removals will be approximately 3 feet below existing grade. Based on the results of our exploratory handpits, as well as our experience with similar materials in the project area, it is our opinion that the existing fill soils and topsoil materials can be excavated utilizing ordinary light to heavy weight earthmoving equipment. Contractors should not, however, be relieved of making their own independent evaluation of excavating the on-site materials prior to submitting their bids. Contractors should also review this report along with the handpit logs to understand the scope and quantity of grading required Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 29 for this project. Variability in excavating the subsurface materials should be expected across the project area. The areal extent required to remove the surficial soils should be confirmed by our representatives during the excavation work based on their examination of the soils being exposed. The lateral extent of the excavation and recompaction should be at least 5 feet beyond the edge of the perimeter ground level foundations of the new residential structures and any areas to receive exterior improvements, where feasible, or to the depth of excavation or fill at that location, whichever is greater. 4. Subgrade Preparation: After the site has been cleared, stripped, and the required excavations made, the exposed subgrade soils in areas to receive new fill and/or slab-on-grade building improvements should be scarified to a depth of 6 inches, moisture conditioned, and compacted to the requirements for structural fill. While not anticipated, in the event that planned cuts expose any medium to highly expansive formational materials in the building areas, they should be scarified and moisture conditioned to at least 3 percent over optimum moisture for low expansive soils and 5 percent for medium and highly expansive soils (if encountered). 5. Material for Fill: Existing on-site low-expansion potential (Expansion Index of 50 or less per ASTM D4829-19) soils with an organic content of less than 3 percent by volume are, in general, suitable for use as fill. Imported fill material, where required, should have a low-expansion potential. 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 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 30 dimension if compacted with lightweight equipment). All materials for use as fill should be approved by our representative prior to importing to the site. If encountered at the site, medium to highly expansive soils should not be used as structural fill at a depth of less than 5 feet from footing bearing surface elevation or behind retaining walls. Backfill material to be placed behind retaining walls should be low expansive (E.I. less than 50), with rocks no larger than 3 inches in diameter. 6. Structural Fill Compaction: All structural fill, and areas to receive any associated improvements, should be compacted to a minimum degree of compaction of 90 percent based upon ASTM D1557-12e1. 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. For low expansive soils, the moisture content should be within 2 percent of optimum. Though we do not anticipate any medium to high expansive soils to be exposed during grading operations, if encountered, the compaction moisture content should be at least 5 percent over optimum. Any rigid improvements founded on the existing undocumented fill soils 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. at Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 31 7. 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. Based on the results of our laboratory testing (see Section V above), the water-soluble sulfate content of the tested soils at the site yielded a negligible sulfate exposure, as such based on table 1904.3 of the building code, there is no restrictions for cement type. Trench and Retaining Wall Backfill: All utility trenches and retaining walls 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 based upon ASTM D1557-12el by mechanical means. Any portion of the trench backfill in public street areas within pavement sections should conform to the material and compaction requirements of the adjacent pavement section. Backfill soils placed behind retaining walls should be installed as early as the retaining walls are capable of supporting lateral loads. Backfill soils behind retaining walls should be low expansive (Expansion Index less than 50 per ASTM D4829-19). 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. ;, Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 32 8. Observations and Testing: As stated in CBC 2019, Section 1705.6 Soils: "Special inspections and tests of existing site soil conditions, fill placement and load-bearing requirements shall be performed in accordance with this section and Table 1705.6 (see below). The approved geotechnical report and the construction documents prepared by the registered design professionals shall be used to determine compliance. During fill placement, the special inspector shall verify that proper materials and procedures are used in accordance with the provisions of the approved geotechnical report". A summary of Table 1705.6 "REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS" is presented below: a) Verify materials below shallow foundations are adequate to achieve the design bearing capacity; b) Verify excavations are extended to proper depth and have reached proper material; c) Perform classification and testing of compacted fill materials; d) Verify use of proper materials, densities and thicknesses during placement and compaction of compacted fill prior to placement of compacted fill, inspect subgrade and verify that site has been prepared properly Section 1705.6 "Soils" statement and Table 1705.6 indicate that it is mandatory that a representative of this firm (responsible engineering firm), perform observations and fill compaction testing during excavation operations to verify that the remedial operations are consistent with the recommendations presented in this report. All grading excavations resulting from the removal of soils should be observed and evaluated by a representative of our firm before they are backfilled. Ii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 33 Quality control grading observation and field density testing for the purpose of documenting that adequate compaction has been achieved and acceptable soils have been utilized to properly support a project applies not only to fill soils supporting primary structures; unless supported by deep foundations or caissons, but all site improvements such as stairways, patios, pools and pool decking, sidewalks, driveways and retaining walls etc. Observation and testing of utility line trench backfill also reduces the potential for localized settlement of all of the above including all improvements outside of the footprint of primary structures. Often after primary building pad grading, it is not uncommon for the geotechnical engineer of record to not be notified of grading performed outside the footprint of the project primary structures. As a result, settlement damage of site improvements such as patios, pool and pool decks, exterior landscape walls and walks, and structure access stairways can occur. It is therefore strongly recommended that the project general contractor, grading contractor, and others tasked with completing a project with workmanship that reduces the potential for damage to the project from soil settlement, or expansive soil uplift, to be advised and acknowledge the importance of adequate and comprehensive observation and testing of soils intended to support the project they are working on. The project geotechnical engineers of record must be contacted and requested to provide these services. Failure to comply with this recommendation can result in several costly and time-consuming requirements from the governing municipality or county engineering and planning departments. For example, the geotechnical and/or civil engineer of record may be required to: Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 34 • Clarify if observation and testing services were performed for all grading shown on the Grading Plans. If not, indicate the areas NOT observed or tested on the As-Graded Geological Map. • A construction change must be processed to indicate the revised grading recommendations by the geotechnical engineer of work on the plans. • The geotechnical engineer must submit on addendum letter addressing the change to the grading plan specifications for the earthwork presented on the grading plans. • The geotechnical consultant must evaluate the existing unobserved/undocumented fill as an uncontrolled embankment and provide a statement indicating the uncontrolled embankment will not endanger the public health, safety and welfare. In order to make this statement the geotechnical engineer would have to clearly define the potential problems such as damage to project improvements that could result from construction on undocumented fill soils. • The geotechnical consultant must indicate if the unobserved fill placed during earthwork within the limits of work is suitable for the intended use. To render such an opinion the geotechnical consultant would have to place a sufficient number of test excavations and conduct enough testing to warrant such an opinion. 11& Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 35 • If the geotechnical consultant cannot render an opinion that the unobserved fill is suitable for the purpose intended, "They must indicate if additional fill remedial grading is recommended." • The limits of the "Unobserved fill/uncontrolled embankment must be shown on revised grading plans along with the "Uncontrolled Embankment Maintenance Agreement Approval Number." • The owner must execute an "Uncontrolled Embankment Agreement: for the portion of the undocumented fill to remain. This must be coordinated with the LDR Drainage and Grading reviewer. • The title and date of the requested addendum letter or geotechnical investigation report must be added under note no. 1 of the "Grading and Geotechnical Specification" Certification as construction change "A". • These changes must be made on a redline copy, and submitted as a "Construction Change A" for review and approval by the geology section and Drainage and Grades Section. • All approved changes will then be transferred to the mylars for approval and signatures by the Deputy City Engineer. The Geotechnical Engineer of Record, in this case Geotechnical Exploration, Inc., cannot be held responsible for the costs and time delays associated with the lack of contact and requests for testing services by the client, general contractor, grading contractor or any of the project design team responsible for requesting the required D Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 36 geotechnical services. Requests for services are to be made through our office telephone number (858) 549-7222 and the telephone number of the G.E.I. personnel assigned to the project. B. Seismic Design Criteria 9. Seismic Data Bases: The estimation of the peak ground acceleration and the repeatable high ground acceleration (RHGA) likely to occur at the site is based on the known significant local and regional faults within 100 miles of the site. 10. Seismic Design Criteria: The proposed structure should be designed in accordance with the 2019 CBC, which incorporates by reference the ASCE 7- 16 for seismic design. We have determined the mapped spectral acceleration values for the site based on a latitude of 33.1508 degrees and a longitude of -117.3442 degrees, utilizing a program titled "Seismic Design Map Tool" and provided by the USGS through SEAOC, which provides a solution for ASCE 7- 16 utilizing digitized files for the Spectral Acceleration maps. See Appendix B. 11. Structure and Foundation Design: The design of the new structures and foundations should be based on Seismic Design Category D, Risk Category II for a Site Class Stiff Soils D. 12. Spectral Acceleration and Design Values: The structural seismic design, when applicable, should be based on the following values, which are based on the site location, soil characteristics, and seismic maps by USGS, as required by the 2019 CBC. The summarized ATC seismic soil parameters are presented in table I below, have been calculated with the SEAOC Seismic Design Map Tool. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 37 C. The complete values are included in Appendix B. The Site Class Stiff Soil D values for this property are: TABLE I Mapped Spectral Acceleration Values and Design Parameters Ss S1 SMs SM1 Sos Soi Fa Fv PGA PGAM SDC 1.091 0.394 1.16 0.751 0.774 0.501 1.064 1.91 0.482 0.539 D Foundation Recommendations 13. Footings: We recommend that the proposed structures be supported on conventional, individual-spread and/or continuous footing foundations bearing on undisturbed formational materials or on properly compacted fill soils over formational soils. No footings should be underlain by undocumented fill soils. A,11 building footings should be built on formational soils or properly compacted fill prepared as recommended above in Recommendation Nos. 3, 4 and 5. The footings should be founded at least 18 inches below the lowest adjacent finished grade when founded into properly compacted fill or formational soils. 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. Otherwise, the utility trenches should be excavated farther from the footing locations. Footings located adjacent to the tops of slopes should be extended sufficiently deep so as to provide at least 8 feet of horizontal cover between the slope face and outside edge of the footing at the footing bearing level. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 38 14. Bearing Values: At the recommended depths, footings on formational or properly compacted fill soils may be designed for allowable bearing pressures of 2,500 psf for combined dead and live loads and 3,325 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: 800 psf for each additional foot over 1.5 feet in depth and 400 psf for each additional foot in width to a total not exceeding 4,000 psf. The static soil bearing value may be increased one-third for seismic and wind load analysis. As previously indicated, all of the foundations for the building should be built on dense formational soils or properly compacted fill soils. 15. Footing Reinforcement: All continuous footings should contain top and bottom reinforcement to provide structural continuity and to permit spanning of local irregularities. We recommend that a minimum of two No. 5 top and two No. 5 bottom reinforcing bars be provided in the footings. All footings should be reinforced as specified by the structural engineer. 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. 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 inspect the footing excavations prior to the placement of reinforcing steel or forms. 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. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 39 16. 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 0.35 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 value assume a level surface in front of the footing for a minimum distance of three times the embedment depth of the footing and any shear keys, but not less than 8 feet from a slope face, measured from effective top of foundation. Retaining walls supporting surcharge loads or affected by upper foundations should consider the effect of those upper loads. 17. Settlement: Settlements under structural design loads are expected to be within tolerable limits for the proposed structures. For footings designed in accordance with the recommendations presented in the preceding paragraphs, we anticipate that the total and differential static settlement for the proposed improvements will be on the order of 1-inch and approximately, post- construction differential settlement angular rotation should be less than 1/240. D. Concrete Slab On-Grade Criteria Slabs on-grade may only be used on new, properly compacted fill or when bearing on dense formational soils. 18. Minimum Floor Slab Thickness and 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 IP Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 40 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. 4 bars on 18-inch centers, both ways, placed at mid- height in the slab. Soil moisture content should be kept above the optimum prior to waterproofing placement under the new concrete slab. Shrinkage joints shall be specified by the structural engineer. 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. 19. 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 suggested minimum protection criteria. Actual recommendations should be provided by the project architect and waterproofing consultants or product manufacturer. It is recommended to contact the vapor barrier manufacturer to schedule a pre-construction meeting and to coordinate a review, in-person or digital, of the vapor barrier installation. Soil moisture vapor can result in damage to moisture-sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor, in addition ;, Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 41 to mold and staining on slabs, 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-mil. Polyethylene retarders, called visqueen, range from 5-to 10-mil 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 more specifically designed for and intended to retard moisture transmission into and through concrete slabs. The use of such products is highly recommended for 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 El 745-17 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. 20.1 Based on the above, we recommend that the vapor barrier consist of a minimum 15-mil extruded polyolefin plastic (no recycled content or woven materials permitted). Permeance as tested before and after mandatory conditioning (ASTM El 745 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 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 42 Class A requirements. 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 prepared properly compacted smooth subgrade soil surface. 20.2 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 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. 91 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 43 20.3 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. 20.4 Following placement of any concrete floor slabs, sufficient drying time must be allowed prior to placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. 21. Exterior Slab Thickness and Reinforcement: As a minimum for protection of on-site improvements, we recommend that all exterior pedestrian concrete slabs be 4 inches thick and be founded on properly compacted and tested fill, 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 improvements are properly designed and constructed for the existing soil conditions. The improvements should not be built on loose soils or fills placed without our observation and testing. 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 91 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 44 exterior slabs should be sealed with elastomeric joint sealant. The sealant should be inspected every 6 months and be properly maintained 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. 22. 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 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 iii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 45 required by the City of Carlsbad. Any retaining wall backfill should be placed under our observation and testing . 23. 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, SOR 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 Carlsbad. G. Pavements 24. Concrete Pavement: We recommend that driveways subject only to automobile and light truck traffic be 5.5 inches thick and be supported directly on properly prepared/compacted on-site subgrade soils. The upper 6 inches of the subgrade below the slab should be compacted to a minimum degree of compaction of 95 percent just prior to paving. The concrete should conform to Section 201 of The Standard Specifications for Public Works Construction, 2015 Edition, for Class 560-C-3250. In order to control shrinkage cracking, we recommend that saw-cut, weakened-plane joints be provided at about 12-foot centers both ways and at reentrant corners. The pavement slabs should be saw-cut as soon as practical Ii Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 46 but no more than 24 hours after the placement of the concrete. The depth of the joint should be one-quarter of the slab thickness and its width should not exceed 0.02-foot. Reinforcing steel is not necessary unless it is desired to increase the joint spacing recommended above. 25. Interlocking Permeable Pavers: If desired, we recommend that permeable pavement pavers for the driveway, subject only to automobile and light truck traffic, be supported on a 1.5 inches of bedding sand No. 8 Sand, on 6-inch thickness of Crushed Miscellaneous Base conforming to Section 200-2 of the Standard Specifications for Public Works Construction, 2018 Edition; or 6 inches of No.57 crushed rock gravel per ASTM D448 gradation. The upper 6 inches of the pavement subgrade soil as well as the aggregate base layer should be compacted to a minimum degree of compaction of 95 percent. Preparation of the subgrade and placement of the base materials should be performed under the observation of our representative. H. Site Drainage Considerations 26. 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. 27. Surface Drainage: Adequate measures should be taken to properly finish- grade the lot after the structures and other improvements are in place. Drainage waters from this site and adjacent properties should be directed away from the footings, floor slabs, and slopes, onto the natural drainage direction for this area or into properly designed and approved drainage facilities provided by the project civil engineer. Roof gutters and downspouts should be ;, Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 47 installed on the residence, with the runoff directed away from the foundations via closed drainage lines. Proper subsurface and surface drainage will help minimize the potential for waters to seek the level of the bearing soils under the footings and floor slabs. Failure to observe this recommendation could result in undermining and possible differential settlement of the structure or other improvements on the site or cause other moisture-related problems. Currently, the CBC requires a minimum 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. 28. Planter Drainage: Planter areas, flower beds and planter boxes should be sloped to drain away from the footings and floor slabs at a gradient of at least 5 percent within 5 feet from the perimeter walls. Any planter areas adjacent to the residence or surrounded by concrete improvements should be provided with sufficient area drains to help with rapid runoff disposal. No water should be allowed to pond adjacent to the residence or other improvements or anywhere on the site. 29. 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 sealing, geofabric installation, protection board (if needed), drain depth below interior floor or yard surface, pipe percent slope to the outlet, etc. r, Juniper Avenue Residential Project Carlsbad, California I. General Recommendations Job No. 20-13022 Page 48 30. Proiect Start Up Notification: In order to reduce work delays during site development, this firm should be contacted 48 hours prior to any need for observation of footing excavations or field density testing of compacted fill soils. If possible, placement of formwork and steel reinforcement in footing excavations should not occur prior to observing the excavations; in the event that 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 prior to correction of the observed problem (i.e., deepening the footing excavation, recompacting soil in the bottom of the excavation, etc.). 31. Cal-OSHA: Where not superseded by specific recommendations presented in this report, trenches, excavations, and temporary slopes at the subject site should be constructed in accordance with Title 8, Construction Safety Orders, issued by Cal-OSHA. 32. Construction Best Management Practices (BMPs): Construction BMPs must be implemented in accordance with the requirements of the controlling jurisdiction. Sufficient BMPs must be installed to prevent silt, mud or other construction debris from being tracked into the adjacent street(s) or storm water 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 work day or after a storm event that causes breach in the installed construction BMPs. 111 Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 49 All stockpiles of uncompacted soil and/or building materials that are intended to be 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 greater. 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 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. XI. GRADING NOTES Geotechnical Exploration, Inc. recommends that we be retained to verify the actual soil conditions revealed during site grading work and footing excavation to be as anticipated in this "Report of Preliminary Geotechnical Investigation" for the project. In addition, the placement and compaction of any fill or backfill soils during site grading work must be observed and tested by the soil engineer. It is the responsibility of the grading contractor and general contractor to comply with the requirements on the grading plans as well as the local grading ordinance. All retaining wall and trench backfill should be properly compacted. Geotechnical Exploration, Inc. will assume no liability for damage occurring due to improperly or uncompacted backfill placed without our observations and testing. al Juniper Avenue Residential Project Carlsbad, California XII. LIMITATIONS Job No. 20-13022 Page 50 Our conclusions and recommendations have been based on available data obtained from our field investigation and laboratory analysis, as well as our experience with similar soils and formational materials located in this area 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 grading operations begin or when footing excavations are placed. In the event discrepancies are noted, additional recommendations may be issued, if required. 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. 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. 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 building plans, especially with respect to the height and location of any proposed structures, this report must be presented to us for immediate review and possible revision. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 51 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 project plans once they are available, to verify that our recommendations are adequately incorporated in the plans. Additional or modified recommendations may be issued if warranted after plan 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 on the site; the safety of others is the responsibility of the 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. Juniper Avenue Residential Project Carlsbad, California Job No. 20-13022 Page 52 Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 20-13022 will expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. . . Senior Geotechnical Engineer Cathy G nze, Project Coordinator Senior Project Geologist ~.~ C.E.G. 999/P.G. 3391 al REFERENCES JOB NO. 20-13022 January 2021 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. 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. Kennedy, M.P. and Tan, S.S., 2007, Geologic Map of the 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. Si REFERENCES/Page 2 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., McElwain, 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. U.S. Dept. of Agriculture, 1953, Aerial Photographs AXN-14M-19 and 20. iii VICINITY MAP SI Thomas Guide San Diego County Edition pg 1106-ES Juniper Residential Development 295 Juniper Avenue Carlsbad, CA. Figure No. I POINT 2 SCENI 3 LOREl 4 SAND Job No. 20-13022 -~~ z ~;, TOPOGRAPHIC SURVEY MAP --295 JUN IPER AVE. REFERENCE: This PLOT PLAN was prepared from an existing TOPOGRAPHIC SURVEY MAP by PASCO LARET SUITER & ASSOCIATES dated 11-3-2020 and from a SITE PLAN by STEPHEN DALTON ARCHITECTS dated Nov. 3, 2020 and from on-site field reconnaissance performed by GEi. 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CAR!.SBAD, CA . 92006 APN 204-240.32 LEGEND ~ HP-5 D D Approximate Location of Exploratory Handpit Approximate Location of Proposed Structure Approximate Location of Existing Structure GEOLOGIC LEGEND Qaf Artificial Fill Qop Old Paralic Deposits (Units 6-7) 6-7 _,,,,. -Approximate Geologic , Contact ,J~,:'i Oi \ Bl OCK ~ Pt,, iS/11')::..S #7 ivtA•' '80.3 -I 30 PLOT PLAN AND SITE SPECIFIC GEOLOGIC MAP Juniper Residential Development 295 Juniper Avenue Carlsbad, CA. Figure No. II Job No. 20-13022 Geotechnical Exploration, Inc. January 2021 ti C) ...J Q. (ii Sl C) ~ C) ll'.'. w Q. z ;i N ~ "' C) g z 0 ~ 0 ...J Q. (ii ,.-EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 3' Handpit 12-14-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 55' Mean Sea Level Not Encountered CKG FIELD DESCRIPTION AND 5::= ~ 5:: = C = CLASSIFICATION ~ Cl g_ Cl g_ l w w w a:: ~~ ::lea:: ::le-...J w ::,~ :c 0 ...J DESCRIPTION AND REflMRKS en <.) ::, ::, ::, ::it; ::i u5 ::le I-::le-I-ID a.. (.) -en -en a.. ::le ::le (Grain size, Density, Moisture, Color) en a..-a..z I--~m w >-<( ,o • w a.. 0 Cl en en :::i ~::le ~Cl O::le ::le Cl ~ SIL TY SAND , fine-to medium-grained. Loose SM -to medium dense. Damp. Dark red-brown. FILU -TOPSOIL (Qaf) - 1 ~:, • SIL TY SAND , fine-to medium-grained, porous. SM • Medium dense. Damp. Red-brown . -~ • WEATHERED OLD PARALIC DEPOSITS -(Qopd 5.0 - 2 - --SIL TY SAND , fine-to medium-grained. Medium ,_s"Kf 5.5 115.1 -dense to dense. Damp. Orange-to red-brown. • • -OLD PARALIC DEPOSITS (Qop d • ~ 3 - - -Bottom@3' - 4- - - - .Y JOB NAME PERCHED WATER TABLE Juniper Avenue Residential Project ~ BULK BAG SAMPLE SITE LOCATION [TI IN-PLACE SAMPLE 295 Juniper Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE 0 NUCLEAR FIELD DENSITY TEST 20-13022 4w4,-.... , FIGURE NUMBER · . Exploratlon, Inc. ~ STANDARD PENETRATION TEST Illa ~ \. 'I ~ 0 c:i i-: c:i d~ ~q + _j ~ en wen zg I-..JW -::le en_ <( z sZ a..:c zo ~o 0::, ::le<.> ~~ ...JO <75e. w <.) ID <.) LOG No. HP-1 ~ 6 (!) .J 0.. X w @ (!) ~ (!) Q:'. w 0.. z ~ "' ti M (!) g z 0 ~ g 0.. ~ rEQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 3' Handpit 12-14-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 56' Mean Sea Level Not Encountered CKG FIELD DESCRIPTION AND ~ >-= l f;:'§' CLASSIFICATION O:::o l w 0~ w 0 Q. WO::: ~~ ::!:a::: :;;;;-_, w :::,~ :r: 0 _, DESCRIPTION AND REMARKS (/) (.) :::, :::, :::, ::s t; ::Sen ::!: I-:a;-I-CD a.. c_j -<f) -<f) a.. :a; :a; (Grain size, Density, Moisture, Color) (/) a.. -a..Z I--~z w >-<i:: ,o 'w a..O :a;~ 0 <f) <f) ::i ~ :a; ~o O::!: -H SIL TY SAND , fine-to medium-grained. Loose SM to medium dense. Dry. Gray-brown. FILU -X TOPSOIL (Qaf) X -y X --many roots in the upper 12". X 1 X SIL TY SAND , fine-to medium-grained, porous. SM -Medium dense. Dry. Gray-to red-brown. WEATHERED OLD PARALIC DEPOSITS -9.5 125.2 (Qop 6-1> --20% passing #200 sieve. - 2 - -3.9 105.4 -~---------------------------~--SIL TY SAND , fine-to medium-grained. Medium SM ► dense to dense. Dry to slightly damp. Red-brown. -1 4.5 3 OLD PARALIC DEPOSITS (Qop d - -Bottom@3' - 4 - - -. - - y_ JOB NAME PERCHED WATER TABLE Juniper Avenue Residential Project [g] BULK BAG SAMPLE SITE LOCATION [TI IN-PLACE SAMPLE 295 Juniper Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE III NUCLEAR FIELD DENSITY TEST 20-13022 4&,4,.-n1u1 FIGURE NUMBER Exploration, Inc. ~ STANDARD PENETRATION TEST lllb ~ '- "I ~ ~ ....: ci ci 0-~q + _j \!:: <f) w <f) z g I--lW -::!: w_ <i:: z ~z a.. :r: zo ~ 0 o:::i ::!:<.:> ~c _,o ~e. w (.) (D(.) LOG No. HP-2 ~ t:i C!J ....I a.. >< w 0 w C!J -, a.. C!J 0:: w a.. z ~ N N 0 (') 8 ...J z 0 ~ 0 ...J a.. /j I' EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 3' Handpit 12-14-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 55' Mean Sea Level Not Encountered CKG FIELD DESCRIPTION AND ~'E' ~ ~c ~ ~ CLASSIFICATION UJ 0~ UJ D o. ,!g_ UJ 0:: ~~ ::;;o:: ::;;--' UJ :::,~ 0 -' Cl) Cl:::, :::, :::, :c DESCRIPTION AND REMARKS ::5 ti ::Sen ::;; I-::;;-I-CD c.. <.5 -en -en c.. ::;; ::;; (Grain size, Density, Moisture, Color) Cl) c.. -c..z I--~ r5 UJ >-<( ,o ' UJ c.. 0 D <f) <f) :::j ~::;; ~D o::;; ::;;o _xg SIL TY SAND , fine-to medium-grained. Loose SM -X to medium dense. Dry. Orange-to red-brown. ? X -X FILL (Qaf) -X \. -X -X X --large chunk of concrete at 7"-9", many roots in -X the upper 18". X X 1 -I• SIL TY SAND , fine-to medium-grained, friable. SM -I• Medium dense. Damp. Orange-brown. - I• -I• OLD PARALIC DEPOSITS (Qop d -I• ---weathered in upper 6". I• -I• -I• 2-,-- - -• -• -1 i---. --23% passing #200 sieve. ~,-----2.9 ---becomes dense@ 30". - - 3 -~ - -Bottom@3' - 4 - - - - _y_ JOB NAME PERCHED WATER TABLE Juniper Avenue Residential Project ~ BULK BAG SAMPLE SITE LOCATION III IN-PLACE SAMPLE 295 Juniper Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE 0 20-13022 •r.-ca& _ ... , NUCLEAR FIELD DENSITY TEST FIGURE NUMBER Exploratlon, Inc. ~ STANDARD PENETRATION TEST Ille ffe-\... " ~ ::R 0 ci ci ,...: d ~q + _j ~ UJ(f.) en :z 0 I--' UJ -::;; en_ <( en :s:z c..:i:: zo c.. z o::::> ::;;c..:, ~~ X 0 _,o <(Z UJ Cl CD Cl en= LOG No. HP-3 ~ 6 (!) ...J 0.. >< w 0 w (!) ~ (!) er: w 0.. z ~ N N g (!) g z 0 ~ g 0.. >< w 'EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 3' Handpit 12-14-20 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 56' Mean Sea Level Not Encountered CKG FIELD DESCRIPTION AND ~ >-c-~ ii:= 'a;' CLASSIFICATION O::o Cl g_ w Cl a. w ,!g_ WO:: ~~ :a: 0:: :a:~ _J w :::, i>: :r: 0 _J DESCRIPTION AND REMARKS (/) 0:::> :::, :::, :'S I-:'S u5 :a: I-:a: -I-ID a... (.) -en a... SQ -en a... :a: :a: ( Grain size, Density, Moisture, Color) (/) CLZ I--~z w >-(75 ,o 'w a...O Cl en :::;; ~:a; ~Cl o::a; :a;~ I• SIL TY SAND , fine-to medium-grained, porous. SM -I• -Loose to medium dense. Damp. Red-brown. I• -I• WEATHERED OLD PARALIC DEPOSITS -I• (Qopd -I• -I• --minor roots. -I• 1 -I• --becomes medium dense. -I• -I• -I• --SIL TY SAND , fine-to medium-grained. Medium --sif I• -I• dense to dense. Damp. Red-brown. - -OLD PARALIC DEPOSITS (Qop d I• 2 -I• -I• ---20% passing #200 sieve. 3.3 102.0 -I• -I• --becomes orange-to red-brown at 30". -::x -7.7 130.4 -I• 3 - - - -Bottom@3' - - - 4 - - - - - - - - Y. JOB NAME PERCHED WATER TABLE Juniper Avenue Residential Project cgj BULK BAG SAMPLE SITE LOCATION [I] IN-PLACE SAMPLE 295 Juniper Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY LDR/JAC MODIFIED CALIFORNIA SAMPLE ~ NUCLEAR FIELD DENSITY TEST 20-13022 4&-4" -~ FIGURE NUMBER Exploration, Inc. !?'ti STANDARD PENETRATION TEST llld ~ -... " -~ ~ c:i f---'. c:i d i>:C! + _j I!: en wen z 0 I-JW -:a: en_ <( en :s;z a... :r: zo CL z o:::> :a:0 ~~ X 0 _,o <CZ w 0 ID 0 en= LOG No. HP-4 ~ 0 ~ (') ~ ~ f-0 (!) ...J 0.. X w 0 w (!) (!) g z 0 ~ g 0.. X w ;-EQUIPMENT DIMENSION & 1YPE OF EXCAVATION DATE LOGGED '" Hand Tools 2' X 2' X 3' Handpit SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH ± 57' Mean Sea Level Not Encountered ~ ,!g_ :i::: l:i: w 0 - - 1 - - - 3 - - - - - - 4 - - - - - - - FIELD DESCRIPTION AND c CLASSIFICATION w -' w f---------------------~--j w a: g a: DESCRIPTION AND REMARKS j :5 ~ ~ ~ (Grain size, Density, Moisture, Color) u5 o,. 5 V, V, ::i ~:,; SIL TY SAND , fine-to medium-grained. Loose to medium dense. Damp. Gray-and red-brown. FILU TOPSOIL (Qaf) --n-s irrigation pipe at 6". --many small roots to 24". --e-w sewer pipe at 24" on south side of pit. SIL TY SAND , fine-to medium-grained. Medium dense. Damp. Orange-to red-brown. OLD PARALIC DEPOSITS (Qop d Bottom@3' JOB NAME SM SM 4.0 99.4 y PERCHED WATER TABLE Juniper Avenue Residential Project ~ BULK BAG SAMPLE SITE LOCATION m IN-PLACE SAMPLE 295 Juniper Avenue, Carlsbad, CA ■ JOB NUMBER REVIEWED BY MODIFIED CALIFORNIA SAMPLE 12-14-20 LOGGED BY CKG w :::;; a: ::;) ::;) :,; I--Cf) I--a...O 0:,; LDR/JAC 0 NUCLEAR FIELD DENSITY TEST 20-13022 -~~--k~ FIGURE NUMBER Exploration, Inc. l?ia STANDARD PENETRATION TEST Ille ~ + _j ·o z Cf) <( z ~o w CJ LOG No. ,-: ~ 1-:;: z o::> -'o al CJ "I ci d wen -'W a...:i::: :a CJ ~e. HP-5 ~ b <'.) g "' w u.. iii <'.) 0 a. ~- ui 135 130 125 120 115 110 m 105 Cl >-c::: Cl 100 95 90 85 80 , , I/ L I\ 1 \ ' \ \ 1 \ \ I\ \ \ ,_ \ / ' -I, \ \ \ \ \ ~ \ \ \ \ l\ I\ ' \I\ \ " \ I\ \ I\ \ \ I\ I\ \ \ I\ \ Source of Material HP-2 @ 1.0' Description of Material SIL TY SAND {SM}1 Gra~-and red-brown Test Method ASTM D1557 Method A \ I\ \ \ -i \ TEST RESULTS I\ \ 1 \ ~ Maximum Dry Density 125.2 PCF \ \ ' \ I\ Optimum Water Content 9.5 % I\ \ "' \ I\ Expansion Index (El) I\ \ \ I\ I\ I\ \ I\ I\ ' \ I\ I\ I\ ' \ I\ I\ I\ \ I\ Curves of 100% Saturation \ ' for Specific Gravity Equal to: \ I\ I\ I\ \ I\ 2.80 I\ \ \ I\ I\ 2.70 \ \ I\ I\ I'\ ' 2.60 \ I\ '\ I'\ I\ I\ \ " I'\ I'\ ' ' I\ I'\ \ I'\ I, '\ " I\. I"::: ' I\.. ~ '\ 1'. I\ '\ ' .... I, '\ ....... r---_ I" 'r.... " I" "r.... " " 'r.... 75 0 5 10 15 20 25 30 35 I"-.. ' l I'---. " I"\ 40 45 Cl a: ~:r------::=-----::=-------------W_A_T..=E ___ R,...::C...:O..:..:N..:..:TE=N---T~, .:..:%~-------------------1 !+ 4~~.• Geotechnical MOISTURE-DENSITY RELATIONSHIP z .,.,liirl Exploration, Inc. Figure Number: IVa g Job Name: Juniper Avenue Residential Project ~ Site Location: 295 Juniper Avenue, Carlsbad, CA :. s, _____________________ .J:.;O;,::b;..:N,;,:U;;,:,m~be::,:r.;.:.,:2~0;,;.-1,:.:3;:,:;0::;2~2-----------.J 135 \ 1 \ \ \ \ \ 130 Al \ \ I ' \ \ \ If I\ \ ' \ \ \ 7 ' \ I\ \ 125 I\ \ ~ \ \ \ l I\ \ Source of Material HP-4@2.5' iJ I\ \ \ i/ ' I\ ' Description of Material SIL TY SAND (SM}, Orange-and i:i (.') ~ UJ u. w (.') ~ (.') Q'. UJ a. z ~ ~ "' 120 115 110 0 Cl. ~ u3 m 105 0 >-a:: 0 100 95 90 85 80 75 0 • 5 I\ \ \ \ \ [\ \ \ ~ I\ \ \ ~ \ 10 15 Test Method \ \ \ ' \ \ ' \ ~ \ ' \ I\ r,_ \ \ I\ I\ I\ \ \ I\ I\ I\ \ I\ ' \ \ " I\ \ ' \ I\ I\ \ \ 20 25 red-brown ASTM D1557 Method A TEST RESULTS Maximum Dry Density 130.4 PCF Optimum Water Content 7.7 % Expansion Index (El) I\. I\ Curves of 100% Saturation I\ I\' I\. for Specific Gravity Equal to: I\ \ I\ 2.80 I\ ' \ I\ I\. 2.70 \ \ " I\ I'\ ' 2.60 \ ' \ I'\ I\ I\. I'\ '\ I\ I\ I'\ ~ I\ \ \ I'\ I\. 1'\ l\. ~ '\ I\. ~ '\ 1'. I\ '\ '"' I"\ '\ ""'- [\_ 1"'-""' I'-. "\ ~ ~ "\ ... ~ I"--.. '\ 1 "\ '\ I"\ 30 35 40 45 0 ii: ~J-----==------==--:----------__:_W:..:....A:..:....TE=R.,.c::.:o:..:N..:..:T-=E.:...:.NT.:..:.,..:..:%::..._ ______________ _. !+ 4~ ~ 1• Geotechnical MOISTURE-DENSITY RELATIONSHIP 2 • ,...., liirl Exploration, Inc. Figure Number: IVb 2 Job Name: Juniper Avenue Residential Project ~ Site Location: 295 Juniper Avenue, Carlsbad, CA ::;; s ___________________ ....1,,;,;JO;,;;b;..:N;.;,u;;,:m.:.::;be;;,:r.;.: .:2;.;;:0_-1:.;;3;,,:;:0~22:;.... __________ _. LABORATORY REPORT Telephone (619) 425-1993 Fax 425-7917 Established 1928 CLARKSON LABORATORY AND SUPPLY INC. 350 Trousdale Dr. Chula Vista, Ca. 91910 www.clarksonlab.com ANALYTICAL AND CONSULTING CHEMISTS Date: December 18, 2020 Purchase Order Number: JUNIPER Sales Order Number: 50203 Account Number: GEOE.R6 To: *-------------------------------------------------* Geotechnical Exploration, INC. 7420 Trade Street San Diego, Ca 92121 Attention: Cathy Ganze Laboratory Number: SO8055-1 Customers Phone: 858-549-7222 Fax: 858-549-1604 Sample Designation: *-------------------------------------------------* One soil sample received on 12/16/20 at 10:10am, taken from Job# Juniper marked as HP-1@1-2' Analysis By California Test 643, 1999, Department of Transportation Division of Construction, Method for Estimating the Service Life of Steel Culverts. pH 7.5 Water Added (ml) 10 5 5 5 5 5 5 Resistivity (ohm-cm) 20000 15000 12000 11000 11000 12000 13000 82 years to perforation for a 16 gauge metal culvert. 106 years to perforation for a 14 gauge metal culvert. 147 years to perforation for a 12 gauge metal culvert. 188 years to perforation for a 10 gauge metal culvert. 229 years to perforation for a 8 gauge metal culvert. Water Soluble Sulfate Calif. Test 417 Water Soluble Chloride Calif. Test 422 Rosa Bernal RMB/js <0.003% 0.001% LABORATORY REPORT Telephone (619) 425-1993 Fax 425-7917 Established 1928 CLARKSON LABORATORY AND SUPPLY INC. 350 Trousdale Dr. Chula Vista, Ca. 91910 www.clarksonlab.com ANALYTICAL AND CONSULTING CHEMISTS Date: December 18, 2020 Purchase Order Number: JUNIPER Sales Order Number: 50203 Account Number: GEOE.R6 To: *-------------------------------------------------* Geotechnical Exploration, INC. 7420 Trade Street San Diego, Ca 92121 Attention: Cathy Ganze Laboratory Number: SO8055-2 Customers Phone: 858-549-7222 Fax: 858-549-1604 Sample Designation: *-------------------------------------------------* One soil sample received on 12/16/20 at 10:10am, taken from Job# Juniper marked as HP-2@3' Analysis By California Test 643, 1999, Department of Transportation Division of Construction, Method for Estimating the Service Life of Steel Culverts. pH 7.6 Water Added (ml) 10 5 5 5 5 5 Resistivity (ohm-cm) 14000 9000 8400 6800 7000 7300 67 years to perforation for a 16 gauge metal culvert. 87 years to perforation for a 14 gauge metal culvert. 121 years to perforation for a 12 gauge metal culvert. 154 years to perforation for a 10 gauge metal culvert. 188 years to perforation for a 8 gauge metal culvert. Water Soluble Sulfate Calif. Test 417 Water Soluble Chloride Calif. Test 422 Rosa Bernal RMB/js <0.003% 0.001% ........ Or,1hOJ• blM' (t'IYPI09"•Phf flyOf'Ogl'al'h)' •na 1~,onJ h-011"1 V $ G & Gl9f\&I lilne O,WI tOlGI o.i..s.tt[)cgo)O'•OO'~~t~ Shao.d k:l,pOglllphoC.b,twtr'cmUSGS 4tilal..,_bOtloft'IOClelt IDEM 11 Oft~ twltnynwtnc. conklu"-#Id lhaded bllh'fl'l'WWVfromNOAA ~-~clu ~11UllJ r0Nf1t No,1h~o.tur'l19:?7 musGs -.... , __ _. TM fNP •n funoe,;I m ~ ~ ~ V $ GoolooU Su,-.eyN.ilotia!Coope,M~~M,,ep,nv Plop""' SlA.TEMAP A.wfflJ N:> WfOAG2(M.t PretM1*at1~at,o,,W1C11NU$ GtologQIS,un,e-y Soulhtt1"~~°'1'HI~~ r -;:;-~C200fl~,ieeo,,fonw~td~ 7 Ai ngnu ttllH'..-d. * pjK1.of l1ll5 IM)MUlllon,'""" bs n,pioel,KA!d l .. ___ ,.,, ... .,., _ __,."""' l 1t.~oC~;,1,o,1~now.rn.,,.blt•u-,.,,_ ~tyo41Mpc'Oduc:titxllfll'~~Pl,ll"PCW Juniper-2008-geo.ai Juniper Residential Development 295 Juniper Avenue Carlsbad, CA. EXCERPT FROM GEOLOGIC MAP OF THE OCEANSIDE 30' x 60' QUADRANGLE, CALIFORNIA Compiled by -t-· t ---.. ~ "' -tr E9 ., .A. ~ .. ...... -fr .1.! ... Michael P. Kennedy1 and Siang S. Tan 1 2007 Digital preparation by Kelly R. Bovard2, Rachel M. Alvarez2, Michael J. Watson2, and Carlos I. Gutierrez' r ... ' ~T(wt.ll,t DECl....,TKlf'f.200" 1.~ .... -~.Clll,-,.~S..,,...., 2 U.S o.dC91C11St,.4,y~otf.-tP~.~dClfl.Po'M ~ ONSHORE MAP SYMBOLS Contut-Cmtact between geologic wit.I; dotted whet• CC11Caled. •·ault-Sclid whe« a«Ulltcly located; dulled wl,m, llf'l'l'OUIIUl<ly l0<:11<d; dotted-• «n«lkd. U • ujllhrowD bl""k. D • dolmlhrown blo<l Am1w and nmnbcr indi~t• ciroctioo and ao!!l<of dipof&ull pl111<. Antlcllllt'--Solid wbett 8'<1U11tl)' locai.d; cloll<d whet, ffllcnltcl Lan-Am••~ iDcica1e prinripll dircdioo of ...,...,.nt. Q11aied ~nm cxi•eac< i• 4""1icmli<. Strtkeand dip of beds fndtllfd o .... 1urn,c1 \~r11,al florlzonul Slrlk• and dip of f&n<0us t>llaUon fndlned \~rtkal Strike and dip or io,.ous J<,ln11 lndlnfd \fftkal Strike and dip or mflamorpt,I< t>llatlon lndlnod Strlk, and dip or .. dlmentary joint, V<rlkal DESCRIPTION OF MAP UNITS Units6-7 Old paralic deposits, undivided Figure No. V Job No. 20-13022 G4jl=~ .... :::9 -:,, ~ December 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 GP GC SW SP SM SC Well-graded gravels, gravel and sand mixtures, little or no fines. Poorly graded gravels, gravel and sand mixtures, little or no fines. Clay gravels, poorly graded gravel-sand-silt mixtures Well-graded sand, gravelly sands, little or no fines Poorly graded sands, gravelly sands, little or no fines. Silty sands, poorly graded sand and silty mixtures. Clayey sands, poorly graded sand and clay mixtures. Fine-grained (More than half of material is smaller than a No. 200 sieve) SILTS 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 A SCE SEISM IC SUMMARY REPORT L\TC Hazards by Location APPENDIX B Search Information Coordinates: Elevation: Timestamp: Hazard Type: Reference Document: Risk Category: 33.1508, -117.3442 64 ft 2021-01-07T16: 12:51.015Z Seismic ASCE7-16 II Go gle Site Class: D Basic Parameters Name Value Description Ss 1.091 MCER ground motion (period=0.2s) S1 0.394 MCER ground motion (period=1.0s) SMs 1.16 Site-modified spectral acceleration value SM1 • null IO. 7 51 ! Site-modified spectral acceleration value Sos 0.774 Numeric seismic design value at 0.2s SA So1 • null !O.501 I Numeric seismic design value at 1.0s SA * See Section 11.4.8 •Additional Information Name Value Description SDC • null ~ Seismic design category Fa 1.064 Site amplification factor at 0.2s Fv • null IL 906ISite amplification factor at 1.0s CRs 0.893 Coefficient of risk (0.2s) CR1 0.904 Coefficient of risk ( 1. Os) PGA 0.482 MCEG peak ground acceleration FPGA 1.118 Site amplification factor at PGA PGAM 0.539 Site modified peak ground acceleration TL 8 Long-period transition period (s) 64ft RMap data ©2021