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HomeMy WebLinkAboutCT 2019-0002; MADISON FIVE; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION; 2018-10-10REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Lanshire Townhomes Project Southeast Corner Madison Street and Oak Avenue Carlsbad; California 30B NO. 18-11968 10 October 2018 RECOpj Ejj Prepared for: Mr. Michael Kootchick R CE I V E D JUN 03 2019 LAND DEVELOPMENT ENGI NEERI NG 04111 Geotechnical Exploration, Inc. ______ SOIL AND FOUNDATION ENGINEERING . GROUNDWATER. ENGINEERING GEOLOGY 10 October 2018 Mr. Michael Kootchick Job No. 18-11968 SOS Property Management 11855 Sorrento Valley Road, Suite 523 San Diego, CA 92121 Subject: Report of Preliminary Geotechnical Investigation Proposed Lansh ire Town homes Project Southeast Corner of Madison Street and Oak Avenue Carlsbad, California Dear Mr. Kootchick: In accordance with your request, and our proposal of August 3, 2018, Geotechnical Exploration, Inc. has performed a preliminary geotechnical investigation and infiltration testing for the subject property. The field work was performed on October 4, 2018. In our opinion, if the conclusions and recommendations presented in this report are implemented during site preparation and construction, the site will be suited for the proposed townhomes project and associated improvements. 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. 18-11968 will expedite a response to your inquiries. Respectfully submitted, GEO NICA EXPL TION, INC. JaiflCerros, P.E. Jona an Browning R.C.E. 34422/G.E. 2007 P.G. 012/ .E.G. 2615 Senior Geotechnical Engineer Senio Proj ct Geologist 7420 TRADE STREEO SAN DIEGO, CA. 92121 0 (858) 549-7222e FAX: (858) 549-1604 0 EMAIL: geotech@geiid.com TABLE OF CONTENTS PAGE I. PROJECT SUMMARY 1 II. SCOPE OF WORK 1 III. SITE DESCRIPTION 2 IV. FIELD INVESTIGATION 3 V. LABORATORY TESTS & SOIL INFORMATION 6 VI. REGIONAL GEOLOGIC DESCRIPTION 7 VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION 11 VIII. GEOLOGIC HAZARDS 12 IX. GROUNDWATER 19 X. CONCLUSIONS AND RECOMMENDATIONS 21 XI. GRADING NOTES 37 XII. LIMITATIONS 37 REFERENCES FIGURES Vicinity Map Plot Plan IIIa-e. Exploratory Excavation Logs IV. Laboratory Test Results APPENDICES Unified Soil Classification System Infiltration Test Data and Infiltration Rate Calculations USDA Web Soil Survey Map USGS Design Maps Summary Report REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Lanshire Townhomes Project Southeast Corner of Madison Street and Oak Avenue Carlsbad, California JOB NO. 18-11668 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 communications with you, that the site will be developed to receive three-story residential townhome structures and associated improvements. The proposed townhome structures are to be constructed of standard-type building materials utilizing a conventional foundation system. Preliminary construction plans were not made available for our review during the preparation of this report, however, 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. II. SCOPE OF WORK The scope of work performed for this investigation included a site reconnaissance and subsurface exploration program, laboratory testing, geotechnical engineering analysis of the field and laboratory data, infiltration testing, 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, and stab on-grade floors. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 2 III. SITE DESCRIPTION The property is known as Assessor's Parcel No. 204-031-01-00 and 204-031-02-00, Lots 15 and 16, Block 47, per Recorded Map 775, in the City of Carlsbad, County of San Diego, State of California. Refer to Figure No. I, the Vicinity Map, for the site location. The site, located on the southeast corner of Madison Street and Oak Avenue in the City of Carlsbad, consists of approximately 0.18-acre. The property is bordered on the north at approximately the same elevation by Oak Avenue; on the east and slightly higher in elevation by an alley; on the west and slightly lower in elevation by Madison Street; and on the south at approximately the same elevation by a single- family residential property. In general, the lot slopes very gently to the west. For Plot Plan, refer to Figure No. II. The relatively undeveloped property consists of a small shed at the northwest corner, and fencing around the perimeter. Vegetation on the site primarily consists of mature trees and palm trees on the eastern portion of the property, and decorative shrubbery and weeds across the property. The building pad is relatively level at an approximate elevation of 54.5 feet above mean sea level (MSL). Elevations across the property range from approximately 53 feet above MSL along the west property line to approximately 56 feet above MSL in the southeastern corner of the property. Information concerning approximate elevations across the site was obtained from a "Topographic Survey Madison Street" map by Alta Consultants, dated August 2, 2018. 4 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 3 IV. FIELD INVESTIGATION Subsurface Investigation The field investigation consisted of a surface reconnaissance and a subsurface exploration program utilizing hand tools to investigate and sample the subsurface soils. Five exploratory excavations were advanced across the lot (HP-1 to HP-5). Additionally, two infiltration tests were conducted utilizing our exploratory excavations (HP-1/INF-1 and HP-2/INF-2). The exploratory excavations were advanced to a maximum depth of 3 feet, in order to obtain representative soil samples and to define the soil profile across the project area. The soils encountered in 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 excavations are shown on the Plot Plan, Figure No. H. Representative samples were obtained from the exploratory excavations at selected depths appropriate to the investigation. All samples were returned to our laboratory for evaluation and testing. Exploratory excavation logs have been prepared on the basis of our observations and laboratory test results. Logs of the exploratory excavations are attached as Figure Nos. Ma-e. In filtration Testing We performed simple open pit falling head testing at two locations in the northwestern and northeastern portions of the property, at a depth of 34 inches in INF-1, and 36 inches in INF-2 per the requirements of the City of Carlsbad Storm Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 4 Water Standards, BMP Design Manual, in accordance with Appendix D. Testing at the two locations (INF-1 and INF-2) revealed falling head rates of 34.286 and 60 minutes/inch, respectively. The simple open pit falling head test rate results for INF- 1 and INF-2 have been converted to infiltration rates using the Porchet Method, and indicate infiltration rates of 0.944- and 0.462-inch/hour, respectively. A minimum factor of safety of 2 must be applied to the recorded infiltration rates. With the minimum factor of safety applied, the infiltration rates on site range from 0.472- to 0.231-inch/hour. Refer to Appendix B for infiltration test rates and infiltration rate calculations. Formational materials referred to as Quaternary-age Old Paralic deposits (Qop6.7) were encountered underlying approximately 1 foot of fill soils in both exploratory infiltration excavations. Laboratory test results at infiltration test location INF-1 and INF-2, indicate 22% and 23% of the soils passed the #200 sieve, respectively. Based on our review of USDA Web Soil Survey map, the site has been assigned to hydrologic soil group (HSG) B. Refer to Appendix C for USDA Web Soil Survey Map. As part of our geologic/geotechnical site evaluation, we considered the following issues: The locations where infiltration testing was conducted on the site are not subject to high groundwater conditions (within 10 feet of the base of a proposed infiltration BMP). The site is not in relatively close proximity to a known contaminated soil site. Portions of the site are underlain by artificial fill soils over medium dense silty sand formational soils, but not subject to hydroconsolidation. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 5 The site has infiltration rates between of 0.472- and 0.231-inch/hour with a minimum factor of safety of 2 applied. The locations where infiltration testing was conducted on the site do not have a silt plus clay percentage of greater than 50. The locations where infiltration testing was conducted on the site are not underlain at relatively shallow depths by practically impermeable formational soils. The locations where infiltration -testing was conducted on the site are not located within 100 feet from a known drinking water well. The locations where infiltration testing was conducted on the site are not located within 100 feet from a known on-site septic system or designated expansion area. The locations where infiltration testing was conducted on the site are not located adjacent to a slope steeper than 25 percent. Based on the results of our simple open pit falling head testing and evaluation of the infiltration rates, it is our professional opinion that the areas of the site where infiltration testing was conducted has favorable soil conditions and appreciable infiltration rates for the design of partial infiltration BMPs. However, we recommend the side walls of the proposed basin be lined with impermeable liner and the basins be located at least 10 feet away from any proposed structures, retaining walls and utility trenches. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 6 V. LABORATORY TESTS & SOIL INFORMATION Laboratory tests were performed on the retrieved soil samples in order to evaluate their index, strength, expansion, and compressibility properties. The test results are presented on Figures Nos. IIIa-e and IV. The following tests were conducted on representative soil samples: Moisture Content (ASTM D2216-10) Determination of Percentage of Particles Smaller than #200 Sieve (ASTM D1140-17) Laboratory Compaction Characteristics (ASTM D1557-12) Moisture content measurements were performed to establish the in situ moisture of samples retrieved from the exploratory excavations.. Moisture content measurements were performed by ASTM methods D2216. These moisture tests help to establish the in situ moisture of samples retrieved from the exploratory excavations. The particle size smaller than a No. 200 sieve analysis (ASTM D1140) tests aid in classifying the tested soils in accordance with the Unified Soil Classification System and provide qualitative information related to engineering characteristics such as expansion potential, permeability, and shear strength. Laboratory compaction tests (ASTM D1557) establish the laboratory maximum dry density and optimum moisture content of the tested soils and are also used to aid in evaluating the strength characteristics of the soils. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 7 The expansion potential of soils is determined, when necessary, utilizing the Standard Test Method for Expansion Index of Soils (ASTM D4829). In accordance with the same Standard (Table 5.3), potentially expansive soils are classified as follows: EXPANSION INDEX POTENTIAL EXPANSION 0 to 20 Very low 21 to 50 Low 51 to 90 Medium 91 to 130 High Above 130 Very high Based on the particle size test results and our experience with the encountered soils, it is our opinion that the .on-site fill and formational soils, in general, possess a low expansion potential. 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 metavocanic, metasedimentary and plutonic rocks predominate in the Peninsular Ranges with primarily Cenozoic sedimentary rocks to the west and east of this central mountain range (Demere, 1997). In the Coastal Plain region, where the subject property is located, the "basement" consists of Mesozoic crystalline rocks. Basement rocks are also exposed as high relief areas (e.g., Black Mountain northeast of the subject property and Cowles Mountain near the San Carlos area of San Diego). Younger Cretaceous and Tertiary sediments lap up against these older features. These sediments form a "layer cake" sequence Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 8 of marine and non-marine sedimentary rock units, with some formations up to 140 million years old. Faulting related to the La Nacion and Rose Canyon Fault zones has broken up this sequence into a number of distinct fault blocks in the southwestern part of the county. Northwestern portions of the county are relatively undeformed by faulting (Demere, 1997). The Peninsular Ranges form the granitic spine of San Diego County. These rocks are primarily plutonic, forming at depth beneath the earth's crust 140 to 90 million years ago as the result of the subduction of an oceanic crustal plate beneath the North American continent. These rocks 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 years ago. The source of these sediments has been the local mountains as well as the ancestral and modern Colorado River (Demere, 1997). Proposed Lanshire Town home Project Job No. 18-11968 Carlsbad, California Page 9 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 (Hart, E.W., 1980), an "active" fault is one that has had ground surface displacement within Holocene time (about the last 11,000 years). 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 (now the California Geological Survey) 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, E.W., 1980). During recent history, prior to April 2010, the San Diego County area has been relatively quiet seismically. No fault ruptures or major earthquakes had been experienced in historic time within the greater San Diego area. Since earthquakes have been recorded by instruments (since the 1930s), the San Diego area has experienced scattered seismic events with Richter magnitudes generally less than M4.0. During June 1985, a series of small earthquakes occurred beneath San Diego Bay, three of which were recorded at M4.0 to M4.2. In addition, the Oceanside earthquake of July 13, 1986, located approximately 26 miles offshore of the City of Oceanside, had a magnitude of M5.3 (Hauksson and Jones, 1988). Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 10 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, though this is the largest event to strike in this area since 1892. The April 4, 2010, earthquake appears to have been larger than the M6.9 earthquake in 1940 or any of the early 20th century events (e.g., 1915 and 1934) in this region of northern Baja California. The event caused widespread damage to structures, closure of businesses, government offices and schools, power outages, displacement of people from their homes and injuries in the nearby major metropolitan areas of Mexicali in Mexico and Calexico in Southern California. 49 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 11 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. Aftershocks from this event continue to the date of this report along the trend northwest and south of the original event, including within San Diego County, closer to the San Diego metropolitan area. There have been hundreds of these earthquakes including events up to M5.7. 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 M1.3 and greater during the first hour. Seismologists expect continued aftershock activity. 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. VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION Our field work, reconnaissance and review of the geologic map by Kennedy and Tan, 2007, "Geologic Map of Oceanside, 30'x60' Quadrangle, CA," indicate that the site is underlain by Quaternary-age Old Paralic deposits Units 6-7 (Qop6-7) formational Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 12 materials. The formational soils are overlain by approximately 1 foot of fill soils across the lot (refer to the Excavation Logs, Figure Nos. IIIa-e). Fill Soils (Qaf): The lot is overlain by approximately 1 foot of fill soils as encountered in all of the exploratory excavations. The encountered fill soils generally consist of loose to medium dense, dry, gray-brown silty sand with some gravel and are considered to have a low expansion potential. Old Paralic Deposits (00p6-7): The encountered formational materials generally consist of poorly to moderately cemented, medium dense to dense, dry to damp, red- brown, silty sand. The formational soils were encountered at a depth of approximately 1 foot in all of the exploratory excavations. The formational soils are considered to have a low expansion potential. VIII. GEOLOGIC HAZARDS The following is a discussion of the geologic conditions and hazards common to this area of the City of Carlsbad, as well as project-specific geologic information relating to development of the subject property. A. Local and Regional Faults Reference to the geologic map of the area. (Kennedy and Tan, 2007), indicates that no faults are shown to cross the site. In our explicit professional opinion, neither an active fault nor a potentially active fault underlies the site. Rose Canyon Fault: The Rose Canyon Fault Zone (Mount Soledad and Rose Canyon Faults) is located approximately 5 miles southwest of the subject site. The Rose Canyon Fault is mapped trending north-south from Oceanside to downtown San Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 13 Diego, from where it appears to head southward into San Diego Bay, through Coronado and offshore. The Rose Canyon Fault Zone is considered to be a complex zone of onshore and offshore, en echelon strike slip, oblique reverse, and oblique normal faults. The Rose Canyon Fault is considered to be capable of generating an M7.2 earthquake and is considered microseismically active, although no significant recent earthquakes are known to have occurred on the fault. Investigative work on faults that are part of the Rose Canyon Fault Zone at the Police Administration and Technical Center in downtown San Diego, at the SDG&E facility in Rose Canyon, and within San Diego Bay and elsewhere within downtown San Diego, has encountered offsets in Holocene (geologically recent) sediments. These findings confirm Holocene displacement on the Rose Canyon Fault, which was designated an "active"fault in November 1991 (Hart E.W. and W. A. Bryant, 2007, Fault-Rupture Hazard Zones in California, California Geological Survey Special Publication 42). Coronado Bank Fault: The Coronado Bank Fault is located approximately 21 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, 1979). The Oceanside earthquake of M5.3 recorded July 13, 1986, is known to have been centered on the fault or within the Coronado Bank Fault Zone. Although this fault is considered active, due to the seismicity within the fault zone, it is significantly less active seismically than the Elsinore Fault (Hileman, 1973). It is postulated that the Coronado Bank Fault is capable of generating a M7.6 earthquake and is of great interest due to its close proximity to the greater San Diego metropolitan area. Newport-Inglewood Fault: The Newport-Inglewood Fault Zone is located approximately 5 miles northwest of the site. A significant earthquake (M6.4) occurred along this fault on March 10, 1933. Since then no additional significant events have occurred. The fault is believed to have a slip rate of approximately 0.6 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 14 mm/year with an unknown recurrence interval. This fault is believed capable of producing an earthquake of M6.0 to M7.4 (SCEC, 2004). Elsinore Fault: The Elsinore Fault is located approximately 24 miles northeast of the site. The fault extends approximately 200 kilometers (125 miles) from the Mexican border to the northern end of the Santa Ana Mountains. The Elsinore Fault zone is a 1- to 4-mile-wide, northwest-southeast-trending zone of 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 mite to 16 miles in length. The trend, length and geomorphic expression of the Elsinore Fault Zone identify it as being a part of the highly active San Andreas Fault system. Like the other faults in the San Andreas system, the Elsinore Fault is a transverse fault showing predominantly right-lateral movement. According to Hart, et al. (1979), this movement averages less than 1 centimeter per year. Along most of its length, the Elsinore Fault Zone is marked by a bold topographic expression consisting of linearly aligned ridges, swales and hallows. Faulted Holocene alluvial deposits (believed to be less than 11,000 years old) found along several segments of the fault zone suggest that at least part of the zone is currently active. Although the Elsinore Fault Zone belongs to the San Andreas set of active, northwest- trending, right-slip faults in the southern California area (Crowell, 1962), it has not been the site of a major earthquake in historic time, other than a M6.0 earthquake near the town of Elsinore in 1910 (Richter, 1958; Toppozada and Parke, 1982). However, based on length and evidence of late-Pleistocene or Holocene displacement, Greensfelder (1974) has estimated that the Elsinore Fault Zone is reasonably capable of generating an earthquake ranging from M6.8 to M7.1. Faulting evidence exposed in trenches placed in Glen Ivy Marsh across the Glen Ivy North Fault (a strand of the Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 15 Elsinore Fault Zone between Corona and Lake Elsinore), suggest a maximum earthquake recurrence interval of 300 years, and when combined with previous estimates of the long-term horizontal slip rate of 0.8 to 7.0 mm/year, suggest typical earthquakes of M6.0 to M7.0 (Rockwell, 1985). San Jacinto Fault: The San Jacinto Fault is located 47 miles to the northeast of the site. The San Jacinto Fault Zone consists of a series of closely spaced faults, including the Coyote Creek Fault, that form the western margin of the San Jacinto Mountains. The fault zone extends from its junction with the San Andreas Fault in San Bernardino, southeasterly toward the Brawley area, where it continues south of the international border as the Imperial Transform Fault (Earth Consultants International [ECI] 2009). The San Jacinto Fault zone has a high level of historical seismic activity, with at least 10 damaging earthquakes (M6.0 to M7.0) having occurred on this fault zone between 1890 and 1986. Earthquakes on the San Jacinto Fault in 1899 and 1918 caused fatalities in the Riverside County area. Offset across this fault is predominantly right- lateral, similar to the San Andreas Fault, although some investigators have suggested that dip-slip motion contributes up to 10% of the net slip (Ed, 2009). The segments of the San Jacinto Fault that are of most concern to major metropolitan areas are the San Bernardino, San Jacinto Valley and Anza segments. Fault slip rates on the various segments of the San Jacinto are less well constrained than for the San Andreas Fault, but the available data suggest slip rates of 12 ±6 mm/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 (WGCEP, 2008) has estimated that there is a 31 percent probability that an earthquake of M6.7 or greater will occur within 30 s4m Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 16 years on this fault. Maximum credible earthquakes of M6.7, M6.9, and M7.2 are expected on the San Bernardino, San Jacinto Valley and Anza segments, respectively, capable of generating peak horizontal ground accelerations of 0.48g to 0.53g in the County of Riverside, (Ed, 2009). A M5.4 earthquake occurred on the San Jacinto Fault on July 7, 2010. The United States Geological Survey has issued the following statements with respect to the recent seismic activity on southern California faults: The San Jacinto fault, along with the Elsinore, San Andreas, and other faults, is part of the plate boundary that accommodates about 2 inches/year of motion as the Pacific plate moves northwest relative to the North American plate. The largest recent earthquake on the San Jacinto fault, near this location, the M6.5 1968 Borrego Mountain earthquake April 8, 1968, occurred about 25 miles southeast of the July 7, 2010, M5.4 earthquake. This M5.4 earthquake follows the 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 17 Caltech/USGS Southern California Seismic Network and a GPS network of more than 100 stations. B. Other Geologic Hazards Ground Rupture: Ground rupture is characterized by bedrock slippage along an established fault and may result in displacement of the ground surface. For ground rupture to occur along a fault, an earthquake usually exceeds M5.0. If a M5.0 earthquake was to take place on a local fault, an estimated surface-rupture length 1 mile long could be expected (Greensfelder, 1974). Our investigation indicates that the subject site is not directly on a known active fault trace and, therefore, the risk of ground rupture is remote. Liquefaction: The liquefaction of saturated sands during earthquakes can be a major cause of damage to buildings. Liquefaction is the process by which soils are transformed into a viscous fluid that will flow as a liquid when unconfined. It occurs primarily in loose, saturated sands and silts when they are sufficiently shaken by an earthquake. On this site, the risk of liquefaction of foundation materials due to seismic shaking is considered to be low due to the medium dense to dense nature of the natural-ground material and the lack of a shallow static groundwater surface under the site. In our opinion, the site does not have a potential for soil strength loss to occur due to a seismic event. Tsunami: A tsunami is a series of long waves generated in the ocean by a sudden displacement of a large volume of water. Underwater earthquakes, landslides, volcanic eruptions, meteoric impacts, or onshore slope failures can cause this displacement. Tsunami waves can travel at speeds averaging 450 to 600 miles per hour. As a tsunami nears the coastline, its speed diminishes, its wave length decreases, and its height increases greatly. After a major earthquake or other near- Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 18 shore 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. Wave heights and run-up elevations from tsunami along the San Diego Coast have historically fallen within the normal range of the tides (Joy 1968). The largest tsunami effect recorded in San Diego since 1950 was May 22, 1960, which had a maximum wave height of 2.1 feet (NOAA, 1993). In this event, 80 meters of dock were destroyed and a barge sunk in Quivera Basin. Other tsunamis felt in San Diego County occurred on November 5, 1952, with a wave height of 2.3 feet caused by an earthquake in Kamchatka; March 9, 1957, with a wave height of 1.5 feet; May 22, 1960, at 2.1 feet; March 27, 1964, with a wave height of 3.7 feet and September 29, 2009, with a wave height of 0.5 feet. It should be noted that damage does not necessarily occur in direct relationship to wave height, illustrated by the fact that the damage caused by the 2.1-foot wave height in 1960 was worse than damage caused by several other tsunamis with higher wave heights. Historical wave heights and run-up elevations from tsunamis that have impacted the San Diego Coast have historically fallen within the normal range of the tides (Joy, 1968). The risk of a tsunami affecting the site is considered moderate as the site is situated at an elevation of approximately 53 feet above mean sea level and approximately 500 feet to an exposed beach. In addition, the site is not mapped within a possible inundation zone on the California Geological Survey's 2009 "Tsunami Inundation Map for Emergency Planning, Oceanside Quadrangle, San Diego County." Geologic Hazards Summaiy: 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 19 depth by relatively stable formational materials and is suited for the proposed townhome project and associated improvements provided the recommendations herein are implemented. No significant geologic hazards are known to exist on the site that would prevent the proposed construction. Ground shaking from earthquakes on active southern California faults and active faults in northwestern Mexico is the greatest geologic hazard at the property. In our explicit professional opinion, no active" or "potentially active" faults underlie the project site. IX. GROUNDWATER No groundwater was encountered during the course of our field investigation and 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. The true groundwater surface is assumed to be more than 50 feet below the existing and planned building pads. Based on exploratory drilling throughout San Diego County, we would expect minor seeps between the ground surface and true water table due to transient "perching" of vadose water on exceptionally dense, low permeability beds within the formational materials. 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 20 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. Subsurface drainage with a properly designed and constructed subdrain system will be required along with continuous back drainage behind any proposed lower-level basement walls, property line retaining walls, or any perimeter stem walls for raised- wood floors where the outside grades are higher than the crawl space grades. Furthermore, crawl spaces, if used, should be provided with the proper cross- ventilation to help reduce the potential for moisture-related problems. Additional recommendations may be required at the time of construction. 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 21 appearances of groundwater may have to be dealt .with on a site-specific basis. Proper functional surface drainage should be implemented and maintained at the property. X. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based upon the practical field investigation 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 the 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 City Engineer in writing of such change prior to the recommencement of grading and/or foundation installation work. A. Seismic Design Criteria 1. Seismic Design Criteria: Site-specific seismic design criteria for the proposed residence are presented in the following table in accordance with Section 1613 of the 2016 CBC, which incorporates by reference ASCE 7-10 for seismic design. We have determined the mapped spectral acceleration values for the site, based on a latitude of 33.1597 degrees and longitude of -117.3454 degrees, utilizing a tool provided by the USGS, which provides a solution for' ] Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 22 ASCE 7-10 (Section 1613 of the 2016 CBC) utilizing digitized files for the Spectral Acceleration maps. Based on our experience with similar soil conditions, we have assigned a Site Soil Classification of D. Refer to the "USGS Design Maps Summary Report" presented as Appendix D. TABLE I Mapped Spectral Acceleration Values and Design Parameters I s, Is, I Fa I Fy I Sms I Smi I Sds I Sd1 1.1509 10.4419 11.040 11.559 1 1.196g I 0.687g I 0.797g 1 0.458g B. Preparation of Soils for Site Development Clearing and Stripping: The existing vegetation on the lot should be removed prior to the preparation of the building pad and areas to receive associated improvements. This includes any roots from existing trees and shrubbery if encountered. Holes resulting from the removal of root systems or other buried obstructions that extend below the planned grades should be cleared and backfilled with properly compacted fill. Building Pad Surface and Subgrade Preparation: After the building pad has been cleared, stripped, and the required excavations made to remove the existing loose or disturbed surface fill, at least the upper 2 feet of pad existing soils should be removed and recompacted. The bottom of the excavation should be extended to expose medium dense to dense formational soils. The bottom of the excavation should be scarified to a depth of 6 inches, moisture conditioned, and compacted to the requirements for structural fill. Material for Fill: Existing on-site soils with an organic content of less than 3 percent by volume are, in general, suitable for use as fill. Imported fill Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 23 material, where required, should have a low-expansion potential (Expansion Index of 50 or less per ASTM D4829-11). In addition, both imported and existing on-site materials for use as fill should not contain rocks or lumps more than 6 inches in greatest dimension if the fill soils are compacted with heavy compaction equipment (or 3 inches in greatest dimension if compacted with lightweight equipment). All materials for use as fill should be approved by our representative prior to importing to the site. Expansive Soil Conditions: We do not anticipate that expansive soils will be encountered during grading. Should such on-site soils be used as fill, they should be moisture conditioned to at least 5 percent above optimum moisture content, compacted to 88 to 92 percent. Soils of medium or greater expansion potential should not be used as retaining wall backfill soils. If basement slabs were to be built and placed directly on medium expansive formational materials, the moisture content of the soil should be verified to be at least 3 percent above optimum, or scarification and moisture conditioning will be required. Fill Compaction: All structural fill should be compacted to a minimum degree of compaction of 90 percent based upon ASTM 01557-12. Fill material should be spread and compacted in uniform horizontal lifts not exceeding 8 inches in uncompacted thickness. Before compaction begins, the fill should be brought to a water content that will permit proper compaction by either: (1) aerating and drying the fill if it is too wet, or (2) moistening the fill with water 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. We do not anticipate that medium to highly expansive soils will be encountered on the site. However, if they are encountered, the moisture content should be at least 5 percent over optimum. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 24 Once placed, soil moisture content of the fill soils should be maintained by sprinkling daily. Medium to highly expansive soils should be compacted to between 88 and 92 percent of Maximum Dry Density. 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 additions and any areas to receive exterior improvements where feasible. If heavy compaction equipment is utilized, oversize material more than 6 inches in diameter should be removed from the fill. If lightweight compaction equipment is used, oversize material more than 3 inches in diameter should be removed. Any rigid improvements founded on the existing surface 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 within 48 hours prior to concrete placement. No uncontrolled fill soils should remain after completion of the site work. In the event that temporary ramps or pads are constructed of uncontrolled fill soils, the loose fill soils should be removed and/or recompacted prior to completion of the grading operation. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 25 Trench and Retaining Wall Backfill: New utility trenches and retaining walls should be backfilled with imported or on-site low-expansive compacted fill; gravel is also a suitable backfill material but should be used only if space constraints will not allow the use of compaction equipment. Gravel can also be used as backfill around perforated subdrains. All backfill material should be placed in lift thicknesses appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent by mechanical means. In pavement areas, that portion of the trench backfill within the pavement section should conform to the material and compaction requirements of the adjacent pavement section. In addition, the low- expansion potential fill layer should be maintained in utility trench backfill within the building and adjoining exterior slab areas. 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. Tempora,y Slopes: We do not anticipate that significant cut slopes will be required during grading operations. Based on our subsurface investigation work, laboratory test results, and engineering analysis, temporary slopes if required should be stable for a maximum slope height of up to 12 feet and may be cut at a slope ratio of 0.75:1.0 in properly compacted fill soils or formational materials. Some localized sloughing or raveling of the soils exposed on the slopes, however, may occur. Since the stability of temporary construction slopes will depend largely on the contractor's activities and safety precautions (storage and equipment loadings near the tops of cut slopes, surface drainage provisions, etc.), it should be the Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 26 contractor's responsibility to establish and maintain all temporary construction slopes at a safe inclination appropriate to his methods of operation. No soil stockpiles or surcharge may be placed within a horizontal distance of 10 feet from the top edge of the excavation. If these recommendations are not feasible due to space constraints, temporary shoring may be required for safety and to protect adjacent property improvements. Similarly, footings near temporary cuts should be underpinned or protected with shoring. C. Design Parameters for Proposed Foundations Continuous Footings: Footings for new structures or improvements should bear on undisturbed formational materials or properly compacted fill soils. The footings for two-story structures should be founded at least 18 inches below the lowest adjacent finished grade when founded into properly compacted fill or into formational material. If new structures are up to three stories high, the footings should be embedded at least 24 inches below lowest adjacent grade. Footings located adjacent to utility trenches should have their bearing surfaces situated below an imaginary 1.5:1.0 plane projected upward from the bottom edge of the adjacent utility trench. Bearing Values: At the recommended depths, footings on native, medium dense formational soil or properly compacted fill soil may be designed for allowable bearing pressures of 2,500 pounds per square foot (psf) for combined dead and live loads and increased one-third for all loads, including wind or seismic. The footings should have a minimum width of 12 inches. Footings deeper than the values recommended above may be increased by 800 psf for each additional foot in depth and 600 psf for each additional foot iwu Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 27 in width with a total maximum static bearing capacity not exceeding 4,000 psf. Bearing capacity may still be increased by one-third when considering seismic or wind loading. 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. Footings over 18" in depth 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 concrete. NOTE: The project Civil/Structural Engineer should review all reinforcing schedules. The reinforcing minimums recommended herein are not to be construed as structural designs, but merely as minimum reinforcement to reduce the potential for cracking and separations. Lateral Loads: Lateral load resistance for structure foundations may be developed in friction between the foundation bottoms and the supporting subgrade. An allowable friction coefficient of 0.40 is considered applicable. An additional allowable passive resistance equal to an equivalent fluid weight of 300 pounds per cubic foot acting against the new foundations may be used in design provided the footings are poured neat against the adjacent undisturbed formational materials and/or properly compacted fill materials. In areas where existing loose fill soils are present in front of existing or new foundations (a Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 28 horizontal distance equal to 3 times the depth of embedment), the allowable passive resistance should be reduced to 150 pcf and friction coefficient to 0.35. These lateral resistance values assume a level surface in front of the footing for a minimum distance of three times the embedment depth of the footing, or at least 7 feet to daylight to a slope face measured from top of the footing. Settlement: Settlements under foundations with building loads that comply with our recommendations are expected to be within tolerable limits for the proposed additions. For footings designed in accordance with the recommendations presented in the preceding paragraphs, we anticipate that total settlements should not exceed 1 inch and that post-construction differential angular rotation should be less than 1/240. Retaining Walls: Retaining walls must be designed to resist lateral earth pressures and any additional lateral pressures caused by surcharge loads on the adjoining retained surface. We recommend that unrestrained (cantilever) walls with level backfill be designed for an equivalent fluid pressure of 38 pcf. We recommend that restrained walls (i.e., basement walls or any walls with angle points that restrain them from rotation) with level backfill be designed for an equivalent fluid pressure of 56 pcf. Unrestrained walls with up to 2.0:1.0 sloping backfill should be designed for an equivalent fluid pressure. of 52 pcf. Restrained walls with up to 2.0:1.0 sloping backfill should be designed for an equivalent fluid pressure of 76 pcf. Wherever walls will be subjected to surcharge loads, they should also be designed for an additional uniform lateral pressure equal to one-third the anticipated vertical surcharge pressure in the case of unrestrained walls and an additional one-half the anticipated vertical surcharge pressure in the case of restrained walls. I I I Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 29 If shoring is required due to limited space constraints, the soil pressure recommended above remain applicable. For soil lateral resistance of soldier piles, the passive resistance values indicated in recommendation No. 12 may be applied in the effective width equal to 2.5 the diameter of the pile times the depth of embedment below the lowest cut surface in front of the pile. For seismic design of unrestrained walls over 6 feet in exposed face, we recommend that the seismic pressure increment be taken as a fluid pressure distribution utilizing an equivalent fluid weight of 14 pcf. For restrained walls, we recommend the seismic pressure increment be waived. A value of KH=0.16 may be used in the design of retaining walls with computer programs such as Retain Pro. The preceding design pressures assume that the walls are backfilled with low expansion potential materials (Expansion Index less than 50) and that there is sufficient drainage behind the walls to prevent the build-up of hydrostatic pressures from surface water infiltration. We recommend, in addition to waterproofing, that back drainage be provided by a composite drainage material such as MiraDrain 6000/6200 or equivalent. The backdrain material should terminate 12 inches below the finish surface where the surface is covered by slabs or 18 inches below the finish surface in landscape areas. Waterproofing should continue to 6 inches above top of wall. A subdrain (such as TotalDrain or perforated pipe in an envelope of crushed rock gravel a maximum of 1 inch in diameter and wrapped with geofabric such as Mirafi 140N), should be placed at the bottom of retaining walls. Backfill placed behind the walls should be compacted to a minimum degree of compaction of 90 percent' using light compaction equipment. If heavy equipment is used, the walls should be appropriately temporarily braced. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 30 Shoring walls, if required, may be designed for the same soil pressure indicated above. The soldier piles passive resistance may be calculated as 750 pcf times the diameter of the pile, times the depth of embedment of the pile below the cut surface. D. Concrete Slab On-Grade Criteria Slabs on-grade may only be used on new, properly compacted fill or when bearing on medium dense natural soils. Minimum Floor Slab Reinforcement: Based on our experience, we have found that, for various reasons, floor slabs occasionally crack. Therefore, we recommend that all slabs on-grade contain at least a minimum amount of reinforcing steel to reduce the separation of cracks, should they occur. Slab subgrade soil should be verified by a Geotechnical Exploration, Inc. representative to have the proper moisture content within 48 hours prior to placement of the vapor barrier and pouring of concrete. New interior floor slabs should be a minimum of 4 inches actual thickness and be reinforced with No. 3 bars on 18-inch centers, both ways, placed at midheight in the slab. Soil moisture content should be kept above the optimum prior to waterproofing placement under the new concrete slab. 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. Slab Moisture Emission: Although it is not the responsibility of geotechnical engineering firms to provide moisture protection recommendations, as a Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 31 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. 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' 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-mu. 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 E1745-97 (2009) Standard Specification for Plastic Water Vapor Retarders Used in Contact Concrete Slabs; ASTM E154-88 (2005) Standard Test Methods for Water Vapor Retarders Used in Contact with Earth; ASTM E96-95 Standard Test Methods for Water Vapor Transmission of Materials; ASTM E1643-98 (2009) Standard Practice for Installation of Water Vapor Retarders Used in Contact Under Concrete Slabs; and ACI 302.211-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 32 16.1 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 E1745 Section 7.1 and subparagraphs 7.1.1-7.1.5) should be less than 0.01 perms (grains/square foot/hour/per inch of Mercury) and comply with the ASTM E1745 Class A requirements. Installation of vapor barriers should be in accordance with ASTM E1643. The basis of design is 15-mil StegoWrap 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 surface smooth compacted subgrade soil. 16.2 Common to al acceptable products, vapor retarder/barrier joints must be tapped and sealed with mastic or the manufacturer's recommended tape or sealing products. 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. 16.3 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 33 owner and project designers should be consulted to determine the specific level of protection required. 16.4 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. Concrete Isolation Joints: We recommend the project Civil/Structural Engineer incorporate isolation joints and sawcuts to at least one-fourth the thickness of the slab in any floor designs. The joints and cuts, if properly placed, should reduce the potential for and help control floor slab cracking. We recommend that concrete shrinkage joints be spaced no farther than approximately 20 feet apart, and also at re-entrant corners. However, due to a number of reasons (such as base preparation, construction techniques, curing procedures, and normal shrinkage of concrete), some cracking of slabs can be expected. Structural slabs should not be provided with control joints. Exterior Slab Reinforcement: Exterior, concrete slabs should be at least 4 inches thick. As a minimum for protection of on-site improvements, we recommend that all nonstructural concrete slabs (such as patios, sidewalks, etc.), be founded on properly compacted and tested fill or medium dense native formation and be underlain (if needed) by 2 inches and no more than 3 inches of clean leveling sand, with No. 3 bars at 18-inch centers, both ways, at the center of the slab. Exterior slabs should 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 34 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. The subgrade of exterior improvements should be verified as properly prepared within 48 hours prior to concrete placement. A minimum thickness of 2 feet of properly recompacted soils should underlie the exterior slabs on-grade or they should be constructed on dense formational soils. 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 and isolation joints in exterior slabs should be sealed with elastomeric joint sealant. The sealant should be inspected every 6 months and be properly maintained. E. Pavement Concrete Pavement: Our preliminary recommendation is that concrete driveway pavements, subject only to automobile and light truck traffic be 6 inches thick and be supported directly on properly prepared/compacted on- site subgrade soils. The upper 8 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. Permeable Payers: Permeable payers should consist of vehicular payers placed on 2 inches of #8 sand, over 6 inches of No. 51 crushed rock gravel, over properly compacted subgrade soils to at least 95 percent. Proper surface and subsurface drainage should be provided to the pavement areas. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 35 F. Site Drainage Considerations 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. 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 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. 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 36 be allowed to pond adjacent to the residence or other improvements or anywhere on the site. G. General Recommendations Project Start Uv 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.). 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. 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 Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 37 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. XL 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 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. XII. LIMITATIONS 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, Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 38 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. 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 grading and structural plans. We should be retained to review the project plans once they are available, to verify that our recommendations are adequately incorporated in them. Additional or modified recommendations may be issued if warranted after plan review. Proposed Lanshire Townhome Project Job No. 18-11968 Carlsbad, California Page 39 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 responsibilityof 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. Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 18-11968 will expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. 2Z7-TiiA. Cerros, P.E. R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer Project Geologist GE 002007 Exp 9/3o/,9j' Jon an . Browning P.G. 012/ .E.G. 2615 Senio roj ct Geologist NAL o JONAThANA. IL BROV*IING NL2 CERTIFIED. S ENGINEERING & GEOLOGIST "s_oF VICINITY MAP NOWL L SAV JE j 0 /SpL/ k2 SThATFORDLN Q ,TA I UI LAGUIA OR k3.NAQR 14 IfA 0 6 / U, - - 'gM \' s' ' Holiday ' Park 00, olary lark Ci j 0 <c. - Pine hase Fie \. O PL A - : '\\ ç$ ' ' \. \BI " o •- ( \ 7 0 - s •;i' , • - 4Q \•• 7 <A''/ ' N Carlsbad\ '9 -Ci •• '? ' iU 2 SCENIC \ State \ ' AQUA HEDIONDA LAGOON Thomas Guide San Diego County Edition pg 1106-E5 Lanshire Townhomes SE Corner of Madison Street and Oak Avenue Carlsbad, CA. Figure No. I Job No. 18-11968 EQUIPMENT DIMENSION & TYPE OFEXCAVATION DATE LOGGED Hand Tools 2' X 2' X 3' Handpit 8-1348 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 54.75' Mean Sea Level Not Encountered JKH FIELD DESCRIPTION - - - - AND CLASSIFICATION —wx . w>. w Cr a • + CL LU M CL DESCRIPTION AND REMARKS (Grain size, Densfty, isture, Color) th ar U)=3 z o u, >- ZO a. Z 0 O O z U) U) Z Z 3 - SILTY SAND , fine-to medium-grained, with SM - - - - - - , some gravel. Loose. Dry. Gray-brown. FILL (Oaf) 1- SILTY SAND , fine- to medium-grained; poorly to SM - moderately cemented. Medium dense to dense. Dry to damp. Red-brown. - OLD PARAIJC DEPOSITS (Qop ) 2 - - iron nodules. - I - 23% passing #200 sieve. 2.1 3 Bottom @ 3' 4- lu %Y PERCHED WATER TABLE JOB NAME Lanshire Townhomes BULK BAG SAMPLE SITE LOCATION [] IN-PLACE SAMPLE SE Corner of Madison St. and Oak Ave., Carlsbad, CA JOB NUMBER REVIEWED BY LDRIJAC LOG No. S • MODIFIED CALIFORNIA SAMPLE Ms NUCLEAR FIELD DENSITY TEST 18-11968 HP=2 GeotechnkaltIon. JflC. Eit STANDARD PENETRATION TEST FIGURE NUMBER IlIb EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 2' Handpit 843-18 SURFACE ELEVATION GROUNDWATER! SEEPAGE DEPTH LOGGED BY ± 54.25' Mean Sea Level Not Encountered JKH - - FIELD DESCRIPTION - AND CLASSIFICATION w ui> . 2 0 ci a LU U, _____________________________ DESCRIP11ONANDREMARKS - - W (Grsze,Density,isture,CoIor)LU ILO C. C) LU C.) Cl) SILTY SAND , fine- to medium-grained, with SM - - - - - - some gravel. Loose. Dry. Gray-brown. - : FILL (Qaf) -. SILTY SAND , fine- to medium-grained; poorly to - SM - moderately cemented. Medium dense to dense. Dry to damp. Red-brown. - OLD PARAUC DEPOSITS (Qop ) - - iron nodules. - - Bottom @2' 3- 4- - ul Y PERCHED WATER TABLE JOB NAME Lanshire Townhomes SITE LOCATION BULK BAG SAMPLE IN-PLACE SAMPLE SE Corner of Madison St. and Oak Ave., Carlsbad, CA JOB NUMBER REVIEWED BY LDRIJAC LOG No MODIFIED CALIFORNIA SAMPLE [] NUCLEAR FIELD DENSITY TEST 1811968 HP=3 4r4j .ot.c.ln.cal Exploration, Inc. STANDARD PENETRATION TEST FIGURE NUMBER IlIc I EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 2.5' Handplt 8-13-18 SURFACE ELEVATION GROUNDWATER) SEEPAGE DEPTh LOGGED BY 154.75' Mean Sea Level Not Encountered JKH FIELD DESCRIPTION - - - - AND - . - I x Ui CLASSIFICATION _____________________________ w uJ ° .a w>_ ij d • o __JUJ - Ui CL LU DESCRIPTION AND REMARKS (Groin size, Density, Moisture, Color) ci cn Cn - 9 V5 ZO Cl) ,Z 3 Z Q. c ., . SILTY SAND, fine- to medium-grained, with SM - - - - - - - some gravel and brick. Loose. Dry. Gray-brown. - FILL (Qaf) 1- SILTY SAND, fine- to medium-grained; poorly to SM - moderately cemented. Medium dense to dense. Dry to damp. Red-brown. - OLD PARAUC DEPOSITS (Qop ) 2 - - - iron nodules. Bottom @ 2.5' 4- Y PERCHED WATER TABLE JOB NAME Lanshire Townhomes SITE LOCATION z $ BULK BAG SAMPLE [II IN-PLACE SAMPLE SE Corner of Madison St. and Oak Ave., Carlsbad, CA REVIEWED BY LDRIJAC LOG No MODIFIED CALIFORNIA SAMPLE NUMBER [] NUCLEAR FIELD DENSITY TEST 18-11968 HP=4 GeoteCluffCal I Exploration, Inc FIGURE NUMBER STANDARD PENETRATION TEST hid EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Hand Tools 2' X 2' X 2.5' Handplt 8-13-18 SURFACE ELEVATION GROUNDWATER) SEEPAGE DEPTH LOGGED BY ± 55.5' Mean Sea Level Not Encountered JKH FIELD DESCRIPTION I AND CLASSIFICATION ' —w uj 0 + 8 - W W C) u CflUJ DESCRIPTION AND REMARKS u (Grain size, Density, Meisture, Color) uS 'r - _ w C) 9 o - SILTY SAND, fine- to medium-grained, with SM - - - - - - - some gravel. Loose. Dry. Gray-brown. T • FILL (Oaf) T - tree roots up to 2" in diameter. 1- SILTY SAND , fine- to medium-grained; poorly to SM moderately cemented. Medium dense to dense. Dry to damp. Red-brown. OLD PARAUC DEPOSITS (Qop ) 2— iron nodules. Bottom @ 2.5' 4— tu PERCHED WATER TABLE NAME Lanshire Townhomes z Z BULK BAG SAMPLE SITE LOCATION [1) IN-PLACE SAMPLE SE Corner of Madison St. and Oak Ave., Carlsbad, CA JOB NMIER REV1EWEDBY LDR!JACI LOG No. MODIFIED CALIFORNIA SAMPLE III NUCLEAR FIELD DENSITY TEST I HP=5 18-11968 Ifp .ut Geotecimical a. STANDARD PENETRATION TEST FIGURE NUMBER I .......... ••UUU•P•LU ........... ........... ........... ........... ........... ........... MEMMMEMEMEM MEMEMEMEMEM UUUM UUUU1L uuuUia ••••••u ......." UUUU•UUUU••kL ............' .............'. ............... ................ ................ ................ ................. .............'... ................. ................. ................. ................. Lfl•I 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 GW Well-graded gravels, gravel and sand mixtures, little (More than half of coarse fraction or no fines. is larger than No. 4 sieve size, but smaller than 3") GP Poorly graded gravels, gravel and sand mixtures, little or no fines. GRAVELS WITH FINES GC Clay gravels, poorly graded gravel-sand-silt mixtures (Appreciable amount) SANDS, CLEAN SANDS SW Well-graded sand, gravelly sands, little or no fines (More than half of coarse fraction is smaller than a No. 4 sieve) SP Poorly graded sands, gravelly sands, little or no fines. SANDS WITH FINES SM Silty sands, poorly graded sand and silty mixtures. (Appreciable amount) SC 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 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. Liquid Limit Greater than 50 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. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils APPENDIX B INFILTRATION TEST DATA AND RATE CALCULATIONS Simple Open Pit Falling Head Test Sheet Project Name: Lanshire Townhomes Tested By: SO Project No. 18-11968 Soil Classification: SM Date Excavated: 10/4/18 Depth of Test Hole: 34 Test Hole No: INF-1 Test Hole Dia: 24" Initial Time (Minutes) Final Time (Minutes) Time interval (minutes) Initial Water Level (inches) Final Water Level (inches) Change in water (Inches) Falling Head Rate (min/inches) 1010 1100 50 27.750 30.250 2.500 20.000 1100 1200 60 28.000 30.125 2.125 28.235 1200 1300 60 28.000 29.750 1.750 34.286 Simple Open Pit Falling Head Test Sheet Project Name: Lanshire Townhomes Tested By: SO Project No. 18-11968 Soil Classification: SM Date Excavated: 10/4/18 Depth of Test Hole: 36" Test Hole No: INF-2 Test Hole Dia: 24" Initial Time (Minutes) Final Time (Minutes) Time interval (minutes) Initial Water Level (Inches) Final Water Level (inches) Change in water (inches) Falling Head Rate (mm/inches) 1020 1120 60 27.500 29.500 2.000 30.000 1120 1220 60 28.500 29.750 1.250 48.000 1220 1320 60 28.500 29.500 1.000 60.000 Simple Open Pit Rate to Infiltration Rate Conversion (Porchet Method) Project Name: Lanshire Townhomes Calculated By: SO Date: 10/4/2018 Project No. 18-11968 Checked By: Date: Test Hole No: lNF-1 Test Hole DIa: 24" Depth of Test Hole: 34" Porchet Corrections Infiltration rate=((delta h60r)/(delta t*(r+2 h avg)) Test No. EB Depth (Inches) Delta T (mm) Water Depth 1 (Inches) Water Depth 2 (inches) h 1 (Inches) h 2 (inches) delta h (Inches) h avg (inches) r (radius) (inches) delta h60r delta t(r+2 h avgi Infiltration rate (ln/hr) 1 34 50 27.750 30.250 6.250 3.750 2.500 5.000 12 1800 1100 1.636 2 34 60 28.000 30.125 6.000 3.875 2.125 4.938 12 1530 1312.5 1.166 3 34 60 28.000 29.750 6.000 4.250 1.750 5.125 12 1260 1335 0.944 4 s 6 7 8 Simple Open Pit Rate to Infiltration Rate Conversion (Porchet Method) Project Name: Lanshire Townhomes Calculated By: SO Date: 10/4/2018 Project No. 18-11968 Checked By: Date: Test Hole No: INF-2 Test Hole Dia: 24° Depth of Test Hole: 36" Porchet Corrections Infiltration rate=((delta h60r)/(delta t(r+2 h avg)) Test ES Depth (inches) Delta I (mm) Water Depth 1 (inches) Water Depth 2 (Inches) h 1 (Inches) h.2 (Inches) delta h (Inches) h avg (Inches) r (radius) (inches) delta _h'60i delta t(r+2 Infiltration rate (In/hr) h ava) 1 36 60 27.500 29.500 8.500 6.500 2.000 7.500 12 1440 1620 0.889 2 36 60 28.500 29.750 7.500 6.250 1.250 6.875 12 900 1545 0.583 3 36 60 28.500 29.500 7.500 6.500 1.000 7.000 12 720 1560 0.462 4 S 6 7 Lanshlre Townitomes Prolect 18-11968 Appendix I: Forms and Checklists k'1 j!Th LilthIy itffi*i]j Feasibilitg - Would Infiltration of the full design volume be feasible flout a physical perspective without any undesirable consequences that cannot be seasonably mitigated? Screening Question Yes No Is the estimated reliable Infiltration rate below proposed facility locations greater than 03 Inches per hour? The response I to this Screening Question shall be based on a comprehensive X evaluation of the factors presented in Appendix Ci and Appendix D. Provide basis: The Infitretlon test results at the locations where testing was conducted on the site were 0.472 and 0.231 Indies per hour with a minimum Is of sefely of 2 applied. Based on the InhItiiotion rote lIndngs below the locations. Institution rates greater than 0.5 Indies per hour were not encountered. Simple open pit testing was performed at 2 locations on the site In accordance with Appendix 001 the City of Carlsbad BMP design manuel. In addition,. comprehensive evaluation of the site was conducted in accordance with Apirendbc C.2. Please refer to cur Repert of Prelimleary Geotedetical Invastgctlon dated October 10, 2018 for details of the comprehensive evaluation end Investigation conducted, simple open pit test rates and simple open pit rate to brllbation rate celuilolians aid maps representative of the study. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Can Infiltration greater than 0,5 inches per hour be allowed without Increasing risk of geotechnical hazard. (elope stability, 2 groundwater mounding, utilities, or other factors) that at be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of - the factors presented in Appendix Ci. Provide basis: The Infilbetlon test results at the locations where testing was conducted on the site ranged from 0.472 to 0.231 indies per hour with a mInimum factor of scf.ty 012 sppfiet Based on the bifJbetion test rate findings below the locations. Infiltration retes greater then 0.5 Indies per hour were not encountered. Therefore, a narrative disasslon of the assodeted geotedvilcol hesrads that cannot be mitigated to an eonptable level Is not applicable. Please refer to ow Report of Preliminray Geotodinimul k1v5st1ge80n dated October 4, 2018 for details 01 the comprehensive evaluation and Investigation conducted, simple open pit test rates end simple open pit rote to Infiltration rate celcoictions and maps representative ofthe study. Sum,md,. findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 1-3 February 2016 Lanshtrelownhomes Proett 18-11968 Appendix I. Forms and Checklists Part 2— PartIal lnfihivationv.. No Infihrstson Fecaihifity Sceernlng Caiterla Would infiltration of water In any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria Screening Question Yea No Do soil and geologic conditions allow for infiltration In any appreciable rate or volume? The response to this Screening X Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. Provide baths: The ittilifratlon teat results at the locations altere tasting was conducted at the aft ranged from 0.472 to 0231 btobes per hour with a minimum factor of safety of 2 applied. Based on our Infiltration test rates and limited gaotedtntcal hwestlgetion of the site, It is our opinion that the soil and geologic conditions allow for partial lnilltraticn rates. However, we reoom,,,end that the sidewall, of the proposed basins be lined. Please refer to cur 'Report of Preliminary Geotsthnlcal Investigation' dated October 10. 2018 for details of the comprehensive evaluation and investigation conducted, simple open pit teat rates end simple open pit rate to Inlilbvtion rate CaICtistioriS and maps representative of the study. Summarize findings of studies; provide reference to studies, calculations, maps, data sources. etc. Provide narrative discussion of study/data source applicability and why trees not feasible to mitigate low infiltration rates. Can Infiltration In any appreciable quantity be allowed without Increasing risk of geotechnleal hazards (elope 6 stability, groundwater mounding, utilities, or other factors) x that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the actors presented in Appendix C.2. Provide basis:- In our opinion, any 10119 term partial Inilbition at the site will not result In geotechnical hazards which cannot be reasonable mItigated loan acceptable level. However, we recommend that the sidewall, of the proposed basins be lined. Please refer to ow 'Report of Preliminary Gactechnical bwestlgation' dated October 10,2018 for details of the conrprahensive evaluation and Investigation conducted, alniple open pit test rates and simple open pit rate to lnlilfration rate calculations and maps representative of the study. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. 1-5 February 2016 Lanshire Townhomes Proe 18-11968 Appendix I: Forms and Checklists rriE siay d-1110 &NftD{ii1tLti*smmew F Category Factor Description Assigned Assigned Factor Product (p) (w) Value (v) p = w xv Soil assessment methods 0.25 2 0.5 Predominant soil texture 0.25 2 0.5 A Suitability Site soil variability 0.25 2 0.5 Assessment Depth to groundeater / lavious layer Oz 2 0.5 Suitability Assessment Safety Factor, SA = IF 2.0 Level of pretreatmcnt/ expected 05 sediment loads B Design Redundancy/traillenCy 0.25 Compaction during construction 0.25 Design Safety Factor, Sn = Ep Combined Safety Factor, Sr-- SAX Se Observed Infiltration Rate inch/hr, K (corrected for test-specific bias) Design Infiltration Rate, in/hr, K = Katm / Sm Supporting Data Briefly describe infiltration teat and provide reference to test fortua Simple open pit testing was performed at 21, - r H, 1 on th, ails per the requIrements of the City of Carlsbad Storm Water Stendards, BMP Design MnucI, In acccrdcnc. with Appendix D. Pletre refer to our 'Report of PrelimInary Geotedinicel InveatIgotion dated Odobar 10, 2015 for datsUn of the oorehenalve evluolion and Invesdgction cenduded, simple open pit test rates and simple open pit rate to hiRbeban rate ealaibtions and maps representatIve of the study. 1-7 February 2016 APPENDIX C USDA WEB SOIL SURVEY MAP Hydrologic Soil Group—San Diego County Area, California (Lanshire Townhomes) 4T11 If 7/fff 467777 4677 4€7 4€71E1 4R71*Y1 If a 33735N - 33 35 N F, 11 )t 571 ,tI 33- N 4,Th31 46T769 46T771 4677 46T793 1 1 Map Scale: 1:359prii1adonA6-ndaape (11"x8.5") sheeL z N 0 5 10 A -- Fea 0 15 OD 90 Map &ion: Web Mer - Cme -dinat: WGS84 Edge U: LITM Zone uN WGS84 USDA Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey - 3a34-N 417l(Y4 a 10/10/2018 Page 1 0f4 Hydrologic Soil Group—San Diego County Area, California Lanshlre Townhomes Hydrologic Soil Group Map unit symbol Map unit name Rating Acres In AOl Percent of AOl MIC Marina loamy coarse sand, 2 to percent -s B 0.2 100.0% Totals for Area of Interest 0.2 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (ND, B/D, and CID). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (ND, BID, or CID), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Natural Resources Web Soil Survey - 10/10/2018 - Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—San Diego County Area, California Lanshire Townhomes Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Web Soil Survey 10/10/2018 Conservation Service National Cooperative Soil Survey Page 4014 APPENDIX D USGS Design Maps Summary Report Report Title Lanshire Townhomes Tue October 9, 2018 23:37:44 UTC Building Code Reference Document ASCE 7-10 Standard (which utilizes USGS hazard data available in 2008) Site Coordinates 33.15970N, 117.3454°W Site Soil Classification Site Class D - "Stiff Soil" Risk Category 1/11/111 WRI M tTh .i - 'Vista oceansiqç Design Maps Summary Report Pagel of2 LJSGS Design Maps Summary Report User—Specified Input CarIsbadr A 1I Sn Marcos Escondido! -—, USGS—Provided Output Ss = 1.150g SMs= 1.196g SDS= 0.797g S1 = 0.441 g SM1 = 0.687 g SD, = 0.458 g For information on how the SS and Si values above have been calculated from probabilistic (risk-targeted) and deterministic ground motions in the direction of maximum horizontal response, please return to the application and select the "2009 NEHRP" building code reference document. NICER Response Spectrum Desfgn Response Spectrum l,' I)' 14' If,, Us' Period. 'I isco Period. T sec For PGA, T, C, and C, values, please https ://prodO 1 -earthquake.cr.usgs. gov/designrnaps/us/summary .php?template=rninimal&la... 10/9/2018 Design Maps Detailed Report Page 1 of ZIJSGS Design Maps Detailed Report ASCE 7-10 Standard (33.1597°N, 117.3454°W) Site Class D - "Stiff Soil", Risk Category I/Il/Ill Section 11.4.1 - Mapped Acceleration Parameters Note: Ground motion values provided below are for the direction of maximum horizontal spectral response acceleration. They have been converted from corresponding geometric mean ground motions computed by the USGS by applying factors of 1.1 (to obtain Ss) and 1.3 (to obtain Si). Maps in the 2010 ASCE-7 Standard are provided for Site Class B. Adjustments for other Site Classes are made, as needed, in Section 11.4.3. From Figure 22-1. S5 = 1.150 g From Figure 22-2 (2J S1 = 0.441 g Section 11.4.2 - Site Class The authority having jurisdiction (not the USGS), site-specific geotechnical data, and/or the default has classified the site as Site Class D, based on the site soil properties in accordance with Chapter 20. Table 20.3-1 Site Classification Site Class v5 . or W. s Hard Rock >5,000 ft/s N/A N/A Rock 2,500 to 5,000 ft/s N/A N/A Very dense soil and soft rock 1,200 to 2,500 ft/s >50 >2,000 psf Stiff Soil 600 to 1,200 ft/s 15 to 50 1,000 to 2,000 psI Soft clay soil <600 ft/s <15 <1,000 psI Any profile with more than 10 ft of soil having the characteristics: Plasticity index P1> 20, Moisture content w 2: 40%, and Undrained shear strength s, < 500 psI F. Soils requiring site response See Section 20.3.1 analysis in accordance with Section 21.1 For SL lit/s = 0.3048 m/s 1lb/ft2 = 0.0479 kN/m2 https://prodOl-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minirnal&latjtu... 10/9/2018 Design Maps Detailed Report Page 2 of 6 Section 11.4.3 - Site Coefficients and Risk-Targeted Maximum Considered Earthquake (MCER) Spectral Response Acceleration Parameters Table 11.4-1: Site Coefficient F. Site Class Mapped MCE R Spectral Response Acceleration Parameter at Short Period S5 :5 0.25 S5 = 0.50 Ss = 0.75 Ss = 1.00 S5 2: 1.25 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 0 1.6 1.4 1.2 J 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S5 For Site Class = D and S. = 1.150 g, F = 1.040 Table 11.4-2: Site Coefficient F Site Class Mapped MCE R Spectral Response Acceleration Parameter at 1-s Period S < 0.10 S = 0.20 S = 0.30 S1 = 0.40 S 2: 0.50 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.7 1.6 1.5 1.4 1.3 0 2.4 2.0 1.8 1.6 1.5 E 3.5 3.2 2.8 2.4 2.4 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S1 For Site Class = D and S = 0.441 g, F. = 1.559 https://prodO 1-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&Iatitu... 10/9/2018 Design Maps Detailed Report Page 3 of 6 Equation (11.4-1): SMS = FaSs = 1.040 X 1.150 = 1.196 9 Equation (11.4-2): SMI = FS, = 1.559 x 0.441 = 0.687 g Section 11.4.4 - Design Spectral Acceleration Parameters Equation (11.4-3): SDs = % Sms = % x 1.196 = 0.797 g Equation (11.4-4): S01 = % S = % x 0.687 = 0.458 g Section 11.4.5 - Design Response Spectrum From Figure 22-12E31 TL = 8 seconds Figure 11.4-1: Design Response Spectrum TcT0:S=S, (OA .O.BTIT) ( I TTT5:S. I I I I5 TTL S. = S!T I • I , TT1:S,= ST, /T2 1• I I I I I 51)1=0.458 I I -r -------------------- I I I • I • I I I I I I I I I I I I I I I I I I = 0.115 T5 = 11.575 1.0011 PedT(irc) https://prodOlearthquake.cr.usgs.gov/designniaps/us/report.php?temp1ate=mjnima1&1atj 10/9/2018 T0 =0.fl5 T5 =O.574 1.000 5M5= 1.196 Design Maps Detailed Report Page 4 of 6 Section 11.4.6 - Risk-Targeted Maximum Considered Earthquake (MCER) Response Spectrum The MCER Response Spectrum is determined by multiplying the design response spectrum above by 1.5. https://prodO 1-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&latitu... 10/9/2018 Design Maps Detailed Report Page 5 of 6 Section 11.8.3 - Additional Geotechnical Investigation Report Requirements for Seismic Design Categories D through F From Figure 22-7 (4] PGA = 0.456 Equation (11.8-1): PGAM = FPGAPGA = 1.044 x 0.456 = 0.476 9 Table 11.8-1: Site Coefficient FwA Site Mapped MCE Geometric Mean Peak Ground Acceleration, PGA Class PGA PGA = PGA PGA = PGA 2: 0.10 0.20 0.30 0.40 0.50 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of PGA For Site Class = D and PGA = 0.456 g, F = 1.044 Section 21.2.1.1 - Method 1 (from Chapter 21 - Site-Specific Ground Motion Procedures for Seismic Design) From Figure 22-i7' CRS = 0.941 From Figure 22-18E61 CRI = 0.993 https://prod0 1-earthquake.cr.usgs.gov/designmaps/us/report.php?template=mjnjmal&laijtu... 10/9/2018 Design Maps Detailed Report Page 6 of 6 Section 11.6 - Seismic Design Category Table 11.6-1 Seismic Desian Cateaory Based on Short Period Resoonse Acceleration Parameter VALUE SDs RISK CATEGORY loril III IV Sc<O.1679 A A A 0.167gSs<0.33g B B C 0.33g Sts < 0.50g C C D 0.5og :5 SOS D D D For Risk Category = I and SDS = 0.797 g, Seismic Design Category = D Table 11.6-2 Seismic Desian Cateoory Based on i-c Period Recnnnce Acceleration Parameter VALUE OF S RISK CATEGORY lorll III IV S0 < 0.0679 A A A 0.0679 S01 < 0.133g B B C 0.133g SDI < 0.209 C C D 0.20g 5 SD1 D D D For Risk Category = I and S61 = 0.458 g, Seismic Design Category =D Note: When S1 is greater than or equal to 0.75g, the Seismic Design Category is E for buildings in Risk Categories I, II, and III, and F for those in Risk Category IV, irrespective of the above. Seismic Design Category "the more severe design category in accordance with Table 11.6-1 or 11.6-2" = D Note: See Section 11.6 for alternative approaches to calculating Seismic Design Category. References Figure 22-1: https://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2O1QASCE-7_Figure_22-1.pdf Figure 22-2: https://earthquake. usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-2. pdf Figure 22-12: https://earthquake. usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-12. pdf Figure 22-7: https://earthquake. usgs.gov/hazards/designmaps/downloads/ pdfs/2010_ASCE-7_Figure_22-7. pdf Figure 22-17: https :1/earthquake. usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-17. pdf Figure 22-18: https ://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7j1gure_22-18.pdf https://prod02-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&latitu... 10/9/2018