CITY VENTURES HOMEBUILDING, INC.

GEOTECHNICAL INVESTIGATION OCEANSIDE 2 PROJECT WEST OF VINE STREET

OCEANSIDE, CALIFORNIA

Prepared for:

CITY VENTURES HOMEBUILDING, INC. 3121 Michelson Drive, Suite150

Irvine, California 92612

Project No. 10864.001

June 1, 2015

3934 Murphy Canyon Road, Suite B205 ■ San Diego, CA 92123-4425 858.292.8030 ■ Fax 858.292.0771 ■ www.leightongroup.com

Geotechnical Investigation, Oceanside 2 10864.001

i

TABLE OF CONTENTS Section Page

1.0 INTRODUCTION ...................................................................................................... 1

1.1 PURPOSE AND SCOPE ............................................................................................. 1 1.2 SITE LOCATION AND DESCRIPTION ............................................................................ 1 1.3 PROPOSED DEVELOPMENT ...................................................................................... 2

2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING .......................... 3

2.1 SITE INVESTIGATION ................................................................................................ 3 2.2 PREVIOUS FIELD INVESTIGATION AND GRADING ......................................................... 3 2.3 RELEVANT STUDIES ................................................................................................ 3

3.0 SUMMARY OF GEOTECHNICAL CONDITIONS .................................................... 5

3.1 GEOLOGIC SETTING ................................................................................................ 5 3.2 SITE-SPECIFIC GEOLOGY ........................................................................................ 5

3.2.1 Artificial Fill (Afo) ........................................................................................... 5 3.2.2 Quaternary-Aged Alluvium (Qal) ................................................................... 6 3.2.3 Tertiary-Aged Santiago Formation (Tsa) ....................................................... 6

3.3 GROUND WATER ..................................................................................................... 6 3.4 ENGINEERING CHARACTERISTICS OF ON-SITE SOILS .................................................. 7

3.4.1 Expansion Potential ....................................................................................... 7 3.4.2 Compressible Soils and Collapse Potential ................................................... 7 3.4.3 Soil Corrosivity .............................................................................................. 7 3.4.4 Excavation Characteristics ............................................................................ 8 3.4.5 Infiltration ....................................................................................................... 8

4.0 SEISMIC AND GEOLOGIC HAZARDS ................................................................... 9

4.1 REGIONAL TECTONIC SETTING ................................................................................. 9 4.2 LOCAL FAULTING .................................................................................................... 9 4.3 SEISMICITY ........................................................................................................... 10 4.4 SEISMIC HAZARDS ................................................................................................ 10

4.4.1 Mapped Fault Zones ................................................................................... 11 4.4.2 Site Class .................................................................................................... 11 4.4.3 Building Code Mapped Spectral Acceleration Parameters .......................... 11

4.5 SECONDARY SEISMIC HAZARDS ............................................................................. 12 4.5.1 Shallow Ground Rupture ............................................................................. 12 4.5.2 Liquefaction and Dynamic Settlement ......................................................... 12 4.5.3 Lateral Spread ............................................................................................. 14 4.5.4 Tsunamis and Seiches ................................................................................ 14

4.6 LANDSLIDES ......................................................................................................... 14


ii

TABLE OF CONTENTS (Continued) Section Page

5.0 CONCLUSIONS ..................................................................................................... 15

6.0 RECOMMENDATIONS .......................................................................................... 17

6.1 EARTHWORK ........................................................................................................ 17 6.1.1 Site Preparation ........................................................................................... 17 6.1.2 Removal of Compressible Soils ................................................................... 17 6.1.3 Cut/Fill Transition Mitigation ........................................................................ 18 6.1.4 Excavations and Oversize Material ............................................................. 19 6.1.5 Engineered Fill ............................................................................................ 19 6.1.6 Earthwork Shrinkage/Bulking ...................................................................... 20 6.1.7 Import Soils ................................................................................................. 20 6.1.8 Expansive Soils and Selective Grading ....................................................... 20

6.2 FOUNDATION AND SLAB CONSIDERATIONS .............................................................. 21 6.2.1 Conventional Foundations ........................................................................... 21 6.2.2 Preliminary Foundation and Slab Design .................................................... 21 6.2.3 Foundation Setback .................................................................................... 22 6.2.4 Settlement ................................................................................................... 23 6.2.5 Moisture Conditioning .................................................................................. 24 6.2.6 Post-Tension Foundation Recommendations .............................................. 25

6.3 LATERAL EARTH PRESSURES AND RETAINING WALL DESIGN .................................... 26 6.4 GEOCHEMICAL CONSIDERATIONS ........................................................................... 28 6.5 CONCRETE FLATWORK .......................................................................................... 28 6.6 PRELIMINARY PAVEMENT DESIGN ........................................................................... 28 6.7 CONTROL OF GROUND WATER AND SURFACE WATERS ............................................ 29 6.8 CONSTRUCTION OBSERVATION .............................................................................. 30 6.9 PLAN REVIEW ....................................................................................................... 31

7.0 LIMITATIONS ........................................................................................................ 32


iii

TABLE OF CONTENTS (Continued)

TABLES TABLE 1 - SEISMIC PARAMETERS FOR ACTIVE FAULTS - PAGE 10 TABLE 2 - CBC MAPPED SPECTRAL ACCELERATION PARAMETERS - PAGE 11 TABLE 3 – CALCULATED POST LIQUEFACTION SETTLEMENT - PAGE 13 TABLE 4 - MINIMUM FOUNDATION SETBACK FROM SLOPE FACES - PAGE 23 TABLE 5 - PRESOAKING RECOMMENDATIONS BASED ON FINISH GRADE SOIL EXPANSION

POTENTIAL - PAGE 24 TABLE 6 - POST-TENSIONED FOUNDATION DESIGN RECOMMENDATIONS - PAGE 25 TABLE 7 - STATIC EQUIVALENT FLUID WEIGHT (PCF) - PAGE 27 TABLE 8 - PRELIMINARY PRIVATE PAVEMENT SECTIONS - PAGE 29 FIGURES

FIGURE 1 - SITE LOCATION MAP - REAR OF TEXT FIGURE 2 - GEOLOGIC CROSS-SECTION - REAR OF TEXT

PLATE

PLATE 1 - GEOTECHNICAL MAP - IN POCKET

APPENDICES APPENDIX A - REFERENCES APPENDIX B - CPT LOGS APPENDIX C - CALCULATIONS APPENDIX D - GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING APPENDIX E - ASFE INSERT


1

1.0 INTRODUCTION

We recommend that all individuals utilizing this report read the preceding information sheet prepared by ASFE (the Association of Engineering Firms Practicing in the Geosciences) and proceeding statement of Limitations located in Section 7.0 at the end of this report.

1.1 Purpose and Scope

This report presents the results of our geotechnical investigation for the site located west of Vine Street and north of Oceanside Boulevard in the City of Oceanside, California (Figure 1). Our investigation included a review of the Conceptual Grading Plan (PSL, 2015), dated May 21, 2015. The intent of this report is to provide specific geotechnical conclusions and recommendations for the currently proposed project.

1.2 Site Location and Description The subject site is bounded to the east by Vine Street, to the south by an existing Fresh and Easy grocery store, to the west and north by ascending slopes where elevated terrace topography hosts residential developments (see Figure 1). As background, the site, an irregular shaped, originally had a natural ridge line in the northern portion of the site with a canyon drainage along the western perimeter and into the southern portion of the site prior grading in the late 80’s. In summary, the previous grading resulted in a terraced parcel with an upper and lower building pad areas and improvements that include a storm drain and sewer utilities. An unpaved gravel access road off Vine Street was also constructed that bisects the lower pad from the upper terraced pad from the east to the northwest. Currently, the building pad areas are vacant and established with native grasses and weeds. Topography of the site is a terraced parcel with an approximate elevation of 40 feet above mean sea level (msl) for the upper pad area, and an approximate elevation of 20 feet msl for the lower pad area. The existing slope between the pad areas is at a 2:1 (horizontal to vertical) inclination.


2

Site Latitude and Longitude 33.1896º N 117.3653º W

1.3 Proposed Development Based on our review of the conceptual plans (PSE, 2015), we understand that the proposed Oceanside 2 project will be a multi-family residential development with eight buildings and a total of 59 townhome residences. The proposed grades have minor cuts and fills that will be needed to complete construction of the building pad areas (i.e., proposed grades range from 40 to 42 feet msl on the upper pad area and 23 to 24 feet msl on the lower pad area). The new development will also include private drives connecting to Vine Street, and four bio-retention ponds. The proposed residential buildings are anticipated to be two- to three-story structures constructed with slab-on-grade foundations and wood framing. The proposed fill slope between the upper and lower building pad areas and along Vine Street are to be constructed at a 2:1 (horizontal to vertical) inclination. A retaining wall, up to 5 feet tall, is also proposed at the toe of the slope along Vine Street and the private drive.


3

2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING 2.1 Site Investigation

Our exploration consisted of advancing eight (8) cone penetration test (CPT) soundings and two (2) percolation test borings. The CPTs were advanced to depths ranging between approximately 21 and 57 feet below the existing ground surface using a 30-ton, purpose modified truck, utilizing an integrated, electronic, metal alloy cone. Data was obtained at 2.5 cm intervals and in general accordance to American Society of Testing and Materials (ASTM) method D5778. The percolation tests were advanced with a 4-inch diameter conventional hand auger to a depth ranging from 4 to 5 feet below the existing ground surface. The percolation test wells were presoaked overnight and the testing was performed the following day by the falling head method. The locations of each CPT sounding and percolation test boring are presented on Plate 1, Geotechnical Map, and results of the soundings are presented in Appendix B. The results of the percolation test are discussed in Section 3.4.5.

2.2 Previous Field Investigation and Grading

A preliminary geotechnical investigation was performed by Geotechnical Engineering Incorporated (GEI) in 1983 to address site conditions and provide geotechnical recommendations with respect to site improvements (GEI, 1983). Subsequently, site grading was performed in 1987 to develop the site to present conditions (GEI, 1987). Note that complete versions of the GEI reports were not available for our review.

2.3 Relevant Studies and Laboratory Testing

In 2008, a geotechnical investigation was performed by Leighton for the Vine Street Commercial Property (Fresh and Easy) located immediately south of the subject site (Leighton, 2008). In summary, the study included three borings and six CPT’s.

As part of the Leighton investigation for Fresh and Easy and the GEI geotechnical investigation, representative soil samples were obtained during the course of the investigations for laboratory testing. The test results from those


4

studies have been incorporated into our analysis and the development of recommendations for the subject site.


5

3.0 SUMMARY OF GEOTECHNICAL CONDITIONS 3.1 Geologic Setting

The site is located in the coastal section of the Peninsular Range Province, a geomorphic province with a long and active geologic history throughout Southern California. Throughout the last 54 million years, the area known as “San Diego Embayment” has undergone several episodes of marine inundation and subsequent marine regression, resulting in the deposition of a thick sequence of marine and non-marine sedimentary rocks on the basement rock of the Southern California batholith.

Gradual emergence of the region from the sea occurred in Pleistocene time, and numerous wave-cut platforms, most of which were covered by relatively thin marine and non-marine terrace deposits, formed as the sea receded from the land. Accelerated fluvial erosion during periods of heavy rainfall, coupled with the lowering of the base sea level during Quaternary times, resulted in the rolling hills, mesas, and deeply incised canyons which characterize the landforms we see in the general site area today.

3.2 Site-Specific Geology Based on our subsurface exploration, geologic mapping during previous site exploration (GEI, 1983), as-graded reporting (GEI, 1987), and review of pertinent geologic literature and maps, the geologic units underlying the site consist of artificial fill soils, Quaternary-aged Alluvium, and the Tertiary-aged Santiago Formation. Brief descriptions of the geologic units present on the site are presented in the following sections. The approximate aerial distributions of those units are shown on the Geotechnical Map (Plate 1). A brief description of the geologic units encountered on the site is presented below.

3.2.1 Artificial Fill (Afo) The site is generally overlain by a previously placed compacted fill soil. The depth of compacted fill across the site is expected to be on the order of 4 to 15 feet, and the upper 2 to 5 feet is considered weathered and disturbed. Prior to placement of the compacted fill, the alluvial soils were reportedly


6

removed to approximately 2 feet below the water table. Reportedly, the fill soils were derived from onsite sandy material and site excavations during the original 1987 grading activities. In addition, at the southern end of the lower terrace pad area, short concrete piles were reportedly pushed into a temporary construction roadway to improve the stability of the subgrade soils and to support traffic prior to fill placement. Imported gravel and concrete debris were also utilized to stabilize the subgrade for support of construction activities in soft saturated areas at the southern end of the lower terrace pad area. Medium to highly expansive soils that were reused as compacted fill were reported placed at least 3 feet below the existing finish grade elevations. The upper fill soils were described as silty sand with gravel, silty sand with clay, silty sand with traces of clay and gravel, and imported crushed gravel.

3.2.2 Quaternary-Aged Alluvium (Qal)

Alluvium is present beneath the compacted fill throughout the southern portion of the site. The alluvium that was left in-place is considered to be saturated and generally increases in depth to the south and east. The materials that comprise the alluvial materials were predominantly clayey with interbedded layers of sands and silty sands to sandy silts. The soundings CPT-1 and CPT-4 through CPT-8 show that alluvial materials were encountered for the remaining depths of the soundings below the overlying compacted fill materials.

3.2.3 Tertiary-Aged Santiago Formation (Tsa)

The Tertiary-aged Santiago Formation is considered to be present beneath the alluvial soils in the southern portion of the site and was encountered below the alluvium in the previous boring B-6 (GEI, 1983). The north portion of the site has as encountered; the materials were described as fine silty sand with clay binder.

3.3 Ground Water

Ground water was encountered at an elevation of 10 feet above mean sea level during the previous exploration activities of the site (GEI, 1983). Materials below this elevation are considered to be saturated.


7

3.4 Engineering Characteristics of On-site Soils

Based on the results of our previous laboratory testing of representative soils on the adjacent site (Leighton 2008), laboratory analysis performed by others representing portions of the on-site soils (GEI, 1983), and our professional experience on similar sites with similar soils conditions, the engineering characteristics of the on-site soils are discussed below.

3.4.1 Expansion Potential

The near surface soils (i.e., soil within the upper 3 feet) are expected to generally possess a low to medium expansion potential. Based on our 2008 study of the adjacent site and review of the GEI as graded report, medium to highly expansive soils were reused as compacted fill and placed at least 3 feet below the existing ground surface elevation. Geotechnical observation and/or laboratory testing upon completion of the graded pads is recommended to determine the actual expansion potential of finish grade soils on the graded lots.

3.4.2 Compressible Soils and Collapse Potential

Based on our analysis of the current site conditions, previous testing (GEI, 1983), relevant adjacent studies (Leighton, 2008), and our professional experience, the artificial fill soils are considered to have low compressibility and a low collapse potential. As for the alluvial soils beneath the lower southern pad area, they are considered to be slightly compressible. However, since 7 to 15 feet of fill soils has been surcharging the saturated alluvial for over 28 years (GEI, 1987), the compressibility and susceptibility to collapse of the alluvium is considered low for proposed final grades and relatively lightly loaded residential structures.

3.4.3 Soil Corrosivity

Based on our analysis of the adjacent site (Leighton, 2008), the potential for sulfate attack to the building foundation is considered low. Laboratory


8

testing should be performed on the soils placed at or near finish grade after completion of site grading to ascertain the corrosivity characteristics.

3.4.4 Excavation Characteristics

The site is underlain by older compacted fill, alluvium and the Santiago Formation at depth. Generally, it is anticipated the on-site soils can be excavated with conventional heavy-duty construction equipment. Deep excavations into or near groundwater may experience instability (i.e., trench excavations or back cuts for slopes). In addition, excavations near the ground water table area may require specialized low ground pressure grading equipment.

3.4.5 Infiltration

Two field percolation tests (P-1 and P-2) were performed to evaluate the existing onsite soils for potential infiltration of storm water. The results of the preliminary field percolation tests indicated that the existing onsite soils have a percolation rate ranging between 55 and 63 minutes per inch (i.e., 1.08 and 0.95 inches per hour). However, note that these percolation rates will not be representative of the site soils following the remedial grading activities (i.e., removal of disturbed and/or compressible soils and placement of compacted fill). A factor of safety should be applied by the project civil engineer to account accumulation of silt in the proposed bio-retention systems. In summary, the existing artificial fill that consist of mixture of silty sands, silts and clays with permeable and impermeable layers can transmit and perched ground water in unpredictable ways. Therefore, Low Impact Development (LID) measures may impact down gradient improvements and the use of some LID measures may not be appropriate for this project. Bio-retention systems should be setback from slopes and structures a minimum of 8 feet, and should be lined if within 20 feet of a descending slope. All Infiltration and Bioretention Stormwater Systems design should be reviewed by geotechnical consultant.


9

4.0 SEISMIC AND GEOLOGIC HAZARDS

4.1 Regional Tectonic Setting

Our discussion of faults on the site is prefaced with a discussion of California

legislation and state policies concerning the classification and land-use criteria associated with faults. By definition of the California Mining and Geology Board, an active fault is a fault which has had surface displacement within Holocene time (about the last 11,000 years). The State Geologist has defined a potentially active fault as any fault considered to have been active during Quaternary time (last 1,600,000 years) but that has not been proven to be active or inactive. This definition is used in delineating Fault-Rupture Hazard Zones as mandated by the Alquist-Priolo Earthquake Fault Zoning Act of 1972 and as most recently revised in 2007 (Bryant and Hart, 2007). The intent of this act is to assure that unwise urban development does not occur across the traces of active faults. Based on our review of the Fault-Rupture Hazard Zones, the site is not located within any Fault-Rupture Hazard Zone as created by the Alquist-Priolo Act.

San Diego, like the rest of Southern California, is seismically active as a result of being located near the active margin between the North American and Pacific tectonic plates. The principal source of seismic activity is movement along the northwest-trending regional fault zones such as the San Andreas, San Jacinto and Elsinore Faults Zones, as well as along less active faults such as the Rose Canyon Fault Zone.

4.2 Local Faulting Our review of available geologic literature (Appendix A) indicates that there are no known major or active faults on or in the immediate vicinity of the site. The nearest active regional fault is the offshore segment of the Newport-Inglewood Fault located approximately 4.3 miles (6.9 kilometers) west of the site.

It should be noted that an “inactive” fault was previously identified in the cut slope in the northern vicinity of the site. Based on the fault analysis prepared by GEI and our professional opinion, the potential for surface rupture at the site is considered low.


10

4.3 Seismicity

The site is considered to lie within a seismically active region, as is all of Southern California. As previously mentioned above, the Newport-Inglewood fault zone located approximately 4.3 miles west of the site is considered the ‘active’ fault having the most significant effect at the site from a design standpoint.

Table 1

Seismic Parameters for Active Faults

Potential Causative Fault Distance from Fault to Site (Miles/km)

Maximum Magnitud

e (Mw)

Peak Horizontal Ground

Acceleration (g)

Newport-Inglewood (Offshore)

4.3/7.0 7.1 0.31

Rose Canyon (Offshore) 5.7/9.1 7.2 0.29

Coronado Bank/Aqua Blanca 21.4/34.4 7.6 0.19

Elsinore Temecula 23.4/37.7 6.8 0.14

Elsinore Julian 24.2/38.9 7.1 0.16

As indicated in Table 1, the offshore segment of the Newport-Inglewood Fault is the ‘active’ fault considered to have the most significant effect at the site from a design standpoint. For a magnitude of 7.1 earthquake on the fault, a peak horizontal ground acceleration of 0.31g is estimated at the site.

4.4 Seismic Hazards

Severe ground shaking is most likely to occur during an earthquake on one of the regional active faults in Southern California. The effect of seismic shaking may be mitigated by adhering to the California Building Code or state-of-the-art seismic design parameters of the Structural Engineers Association of California.


11

4.4.1 Mapped Fault Zones

The site is not located within a State mapped Earthquake Fault Zone (EFZ). As previously discussed, the subject site is not underlain by known active or potentially active faults.

4.4.2 Site Class Utilizing 2013 California Building Code (CBC) procedures, we have characterized the site soil profile to be Site Class D based on our experience with similar sites in the project area and the results of our subsurface evaluation.

4.4.3 Building Code Mapped Spectral Acceleration Parameters

The effect of seismic shaking may be mitigated by adhering to the California Building Code and state-of-the-art seismic design practices of the Structural Engineers Association of California. Provided below in Table 2 are the risk-targeted spectral acceleration parameters for the project determined in accordance with the 2013 California Building Code (CBSC, 2013) and the USGS Worldwide Seismic Design Values tool (Version 3.1.0).

Table 2

CBC Mapped Spectral Acceleration Parameters

Site Class D

Site Coefficients Fa

Fv = =

1.035 1.553

Mapped MCER Spectral Accelerations SS

S1 = =

1.163g0.447g

Site Modified MCER Spectral Accelerations SMS

SM1 = =

1.204g0.694g

Design Spectral Accelerations SDS

SD1 = =

0.802g0.463g

Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the following additional parameters for the peak horizontal ground


12

acceleration are associated with the Geometric Mean Maximum Considered Earthquake (MCEG). The mapped MCEG peak ground acceleration (PGA) is 0.460g for the site. For a Site Class D, the FPGA is 1.040 and the mapped peak ground acceleration adjusted for Site Class effects (PGAM) is 0.478g for the site.

4.5 Secondary Seismic Hazards In general, secondary seismic hazards can include soil liquefaction, seismically-induced settlement, lateral displacement, surface manifestations of liquefaction, landsliding, seiches, and tsunamis. The potential for secondary seismic hazards at the subject site is discussed below. 4.5.1 Shallow Ground Rupture

No active faults are mapped crossing the site, and the site is not located within a mapped Alquist-Priolo Earthquake Fault Zone (Bryant and Hart, 2007); therefore, shallow ground rupture due to shaking from distant seismic events is not considered a significant hazard. However, an in-active faulting was previously identified onsite and based on previous analysis performed by GEI and our experience with similar faults we conclude the fault is inactive.

4.5.2 Liquefaction and Dynamic Settlement

Liquefaction and dynamic settlement of soils can be caused by strong vibratory motion due to earthquakes. Research and historical data indicate that loose granular soils underlain by a near surface ground water table are most susceptible to liquefaction, while the most clayey materials are not susceptible to liquefaction. Liquefaction is characterized by a loss of shear strength in the affected soil layer, thereby causing the soil to behave as a viscous liquid. This effect may be manifested at the ground surface by settlement and, possibly, sand boils where insufficient confining overburden is present over liquefied layers. Where sloping ground conditions are present, liquefaction-induced instability can result.

For the liquefaction analysis, we used the software CLiq (v.1.7.6.34). The design ground motions considered in our liquefaction triggering analyses


13

was a 0.48g acceleration based on a maximum moment magnitude earthquake of (M) 6.9. Liquefaction analysis was performed utilizing the procedures of Robertson and Wride and NCEER guidance (Youd, T.L., Idriss, I.M. and Others, 2001). Based on our analysis, much of the alluvial soils encountered in the southern portion of the site are considered too clay rich to experience liquefaction. Where liquefaction potential was identified, the potential was found to be within relatively thin layers, with increasing thickness in some of the soundings at greater depths. Table 3 provides a summary of the calculated post-liquefaction settlement that may be experienced as a result of the design earthquake event. Note that CPT-2 and CPT-3 were performed in the northern portion of the site, which is underlain by non-liquefiable compacted fill and formational material.

Table 3 Calculated Post-Liquefaction Settlement

Location Settlement

(in)

CPT-1 1.1

CPT-2 NL

CPT-3 NL

CPT-4 0.6

CPT-5 <0.1

CPT-6 <0.5

CPT-7 0.3

CPT-8 0.4

As historic data has not supported the development of liquefaction at depths greater than 50 feet in naturally deposited materials, it should be noted that the calculated post-liquefaction settlements correspond to analysis of the upper 50 feet of the sounding profile.


14

4.5.3 Lateral Spread Empirical relationships have been derived (Youd et al., 1999) to estimate the magnitude of lateral spread due to liquefaction. These relationships include parameters such as earthquake magnitude, distance of the earthquake from the site, slope height and angle, the thickness of liquefiable soil, and gradation characteristics of the soil. The susceptibility to earthquake-induced lateral spread is considered to be low for the site.

4.5.4 Tsunamis and Seiches Based on our review of the San Diego County Tsunami Inundation Map for Emergency Planning, Oceanside/San Luis Rey Quadrangle, (Calif. EMA, 2009), the favorable geologic and seismic conditions along the coastline, and site elevation, there is little potential for catastrophic damage due to tsunamis.

4.6 Landslides

Several formations within the San Diego region are particularly prone to landsliding. These formations generally have high clay content and mobilize when they become saturated with water. Other factors, such as steeply dipping bedding that project out of the face of the slope and/or the presence of fracture planes, will also increase the potential for landsliding. No landslides or indications of deep-seated landsliding were indicated at the site during our field exploration or our review of available geologic literature, topographic maps, and stereoscopic aerial photographs. Furthermore, our field reconnaissance and the local geologic maps indicate the site is generally underlain by favorable geologic structure. However, based on available geologic literature and maps, the site is classified as generally susceptible to landslide hazards.


15

5.0 CONCLUSIONS Based on the results of our geotechnical investigation of the site, it is our opinion that the proposed development is feasible from a geotechnical standpoint, provided the following conclusions and recommendations are incorporated into the project plans and specifications. The following is a summary of the significant geotechnical factors that we expect may affect development of the site. The site is overlain by existing compacted fill. The depth of compacted fill is expected

to be on the order of 4 to 15 feet, and the upper 2 to 5 feet is considered weathered and disturbed.

The near surface on-site soils (i.e., the upper 3 to 4 feet) are expected to generally

possess a very low to medium expansion potential with Expansion Index values less than 90. Deeper fill soils are expected to be medium to highly expansive.

Onsite soils are expected to have a low to potential for sulfate attack on concrete. The existing upper onsite soils appear to be suitable material for use as compacted

fill provided they are free of organic material, debris, and rock fragments larger than 6 inches in maximum dimension. Note that soil placed within 4 feet of the building pad grade should possess an expansion index less than 90.

There are no known major or active faults on or in the immediate vicinity of the site. In

addition, evidence of active faulting was not encountered within the site during our previous field investigation or the prior grading operations. Because of the lack of known active faults on the site, the potential for surface rupture at the site is considered low. Note that an “inactive” fault was identified in the northwestern vicinity of the site; however, it is not considered a site constraint.

The main seismic hazard that may affect the site is ground shaking from one of the

active regional faults. The nearest known active fault is the Newport-Inglewood, which is located approximately 4.3 miles (6.9 kilometers) west of the site.

Our liquefaction analysis indicates that there is liquefaction potential in the southern

portion of the site within relatively thin layers of the alluvial soils, and increasing


16

thickness in some of the soundings at greater depths. Note that in the northern portion of the site, compacted fill and formational material are non-liquefiable.

The calculated post-liquefaction total settlement in the southern portion of the site is

anticipated to be less than 1 ½ inches with differential less than ¾ of an inch. Ground water is anticipated at an elevation of 10 feet above mean sea level, based

on the results of previous subsurface explorations. Zones of perched groundwater should also be anticipated.

The new artificial fill consisting of mixture of soils ranging from silty sands to sandy clays will have permeable and impermeable layers that can transmit and perched groundwater in unpredictable ways. Low Impact Development (LID) measures may impact down gradient improvements and the use of some LID measures may not be appropriate for this project.


17

6.0 RECOMMENDATIONS

6.1 Earthwork

We anticipate that earthwork at the site will consist of site preparation, and remedial grading. We recommend that earthwork on the site be performed in accordance with the City of Oceanside grading requirements, following recommendations and the General Earthwork and Grading Specifications for Rough Grading included in Appendix D. In case of conflict, the following recommendations supersede those in Appendix D.

6.1.1 Site Preparation

Prior to grading, all areas to receive structural fill, engineered structures, pavements, or hardscape should be cleared of surface and subsurface obstructions, including any existing debris and undocumented, loose, compressible, or unsuitable soils, and stripped of vegetation. Removed vegetation and debris should be properly disposed off-site. All areas to receive fill and/or other surface improvements should be performed in accordance to Section 6.1.5.

6.1.2 Removal of Compressible Soils

Potentially compressible undocumented fill, weathered older fill and alluvium (i.e., beneath the central fill slope) that may settle as a result of wetting or settle under the surcharge of improvements, such as, engineered fill and/or structural loads supported on shallow foundations. Therefore, remedial grading is recommended across the entire site to remove weathered artificial fill and potential undocumented fill (Plate 1). These soils should be removed to undisturbed artificial fill and replaced as moisture conditioned engineered fill. In general, removal depths will range from 2 to 5 feet below the existing ground surface across the site. The lateral limits of the removal bottom should extend at least 10 feet beyond the proposed building pad limits where possible. Note that complete removal of alluvial material is recommended beneath the proposed central slope and retaining wall area. The approximate limits of alluvium removal beneath the central fill slope is presented on the Geotechnical Map (Plate


18

1). The bottom of all removals should be evaluated by a Certified Engineering Geologist to confirm conditions are as anticipated. In general, the soil that is removed may be reused and placed as engineered fill provided the material is free of oversized rock, organic materials, and deleterious debris, and moisture conditioned to above optimum moisture content. As previously mentioned, some medium to high expansive material may be encountered 3 feet below existing grades. Soil with an expansion index greater than 50 should not be used within 5 feet of finish grade in the building pad. The actual depth and extent of the required removals should be confirmed during grading operations by the geotechnical consultant.

6.1.3 Cut/Fill Transition Mitigation Grading a site can typically results in cut/fill transitions across the building pad. As the subject site has underwent at the least one grading event, cut/fill transitions may not pose a concern to the design improvements, however, there may be localized areas exposed during remedial grading where cut/fill transitions occur in the northern portion of the site; and as a result the introduction of materials (fill compared to Santiago Formation) having differing permeability and density into the site may create a condition where surface infiltration of water may accumulate below grade. As such, overexcavation of the Santiago Formation, if encountered during remedial grading should be sloped at 1 percent toward the streets or deeper fills. To mitigate the impact of the underlying cut/fill transition condition beneath possible structures that are planned across existing or future cut/fill transitions, the cut portion should be over-excavated to at least 5 feet below the bottoms of proposed foundations. The over-excavated material should be replaced with properly compacted fill. The overexcavation should laterally extend at least 5 feet beyond the building pad area and all associated settlement-sensitive structures. Test pits performed by grading contracting will be necessary during site grading to determine if cut/fill transitions exist.


19

6.1.4 Excavations and Oversize Material

Excavations of the onsite materials within the artificial fill and alluvium may generally be accomplished with conventional heavy-duty earthwork equipment. However, if excavations encounter or are near groundwater or zones of perched groundwater, low impact earthwork equipment may be warranted. Temporary excavations in the artificial fill and alluvium, such as utility trenches with vertical sides, may slough over time.

In accordance with OSHA requirements, excavations deeper than 5 feet should be shored or be laid back, if workers are to enter such excavations. Temporary sloping gradients should be determined in the field by a “competent person” as defined by OSHA. For preliminary planning, sloping of fill soils at 1:1 (horizontal to vertical) may be assumed. Excavations supporting structures or greater than 20 feet in height will require an alternative sloping plan or shoring plan prepared by a California registered civil engineer.

6.1.5 Engineered Fill After preparation and mitigation of areas to receive engineered fill (see section 6.1.1 through section 6.1.3), the existing upper 8 inches of subgrade soils should be scarified then moisture conditioned to moisture content at or above the optimum content and compacted to 90 percent or more of the maximum laboratory dry density, as evaluated by ASTM D 1557. Soil utilized as fill should be free of oversized rock, organic materials, and deleterious debris. Rocks greater than 6 inches in diameter should not be placed within 2 feet of finished grade. Fill should be moisture conditioned to at least 2 percent above the optimum moisture content and compacted to 90 percent or more relative compaction, in accordance with ASTM D 1557. Although the optimum lift thickness for fill soils will be dependent on the type of compaction equipment utilized, fill should generally be placed in uniform lifts not exceeding approximately 8 inches in loose thickness. In vehicle pavement and trash enclosure areas, the upper 12 inches of subgrade soils should be scarified then moisture conditioned to a moisture


20

content above optimum content and compacted to 95 percent or more of the maximum laboratory dry density, as evaluated by ASTM D 1557. Placement and compaction of fill should be performed in general accordance with current City of Oceanside grading ordinances, California Building Code, sound construction practice, these recommendations and the General Earthwork and Grading Specifications for Rough Grading presented in Appendix D.

6.1.6 Earthwork Shrinkage/Bulking

As the site has undergone at least one grading event, the volume change of excavated onsite materials upon recompaction as fill is not expected to significantly impact grading quantities. However, typically the surficial soils and formational materials vary significantly in natural and compacted density, and therefore, accurate earthwork shrinkage/bulking estimates cannot be determined. If needed and based on the results of our geotechnical analysis and our experience, a 5 to 15 percent shrinkage factor is considered appropriate for the undocumented fill and alluvium and a 5 percent bulking factor is considered appropriate for the Santiago Formation.

6.1.7 Import Soils If import soils are necessary to bring the site up to the proposed grades, the soil should be granular in nature, environmentally clean, have an expansion index less than 50 (per ASTM Test Method D4829) and have a low corrosion impact to the proposed improvements. Import soils and/or the borrow site location should be evaluated by the geotechnical consultant prior to import.

6.1.8 Expansive Soils and Selective Grading We anticipate the near surface onsite soil materials to possess a low to medium expansion potential and medium to highly expansive below 3 feet in select areas. Should an abundance of highly expansive materials be encountered, selective grading may need to be performed, such as, placing these materials in the deeper portions of the planned fill areas. In


21

addition, to accommodate conventional foundation design, the upper 5 feet of materials within the building pad and 5 feet outside the limits of the building foundation should have a very low to medium expansion potential (EI<70).

6.2 Foundation and Slab Considerations

At the time of drafting this report, building loads were not known. However, based on our understanding of the project, the proposed multi-family residential buildings may be constructed with conventional foundations or post-tensioned foundations. Foundations and slabs should be designed in accordance with structural considerations and the following recommendations. The recommendations for conventional foundations assume that the soils encountered within 5 feet of pad grade have a low potential for expansion (EI<70). If more expansive materials are encountered and selective grading cannot be accomplished, revised conventional foundations recommendations or the use of post-tensioned foundations may be necessary. The foundation recommendations below assume that the all building foundations will be underlain by properly compacted fill. 6.2.1 Conventional Foundations

Foundations and slabs should be designed in accordance with structural considerations and the following recommendations. These recommendations assume that the soils encountered within 5 feet of pad grade have a low to medium potential for expansion and a differential fill thickness of less than 10 feet. Additional expansion testing should be performed as part of the fine grading operations. If medium or highly expansive soils are encountered and selective grading cannot be accomplished, additional foundation design may be necessary.

6.2.2 Preliminary Foundation and Slab Design

The proposed buildings may be supported by conventional, continuous or isolated spread footings. Footings should extend a minimum of 24 inches beneath the lowest adjacent soil grade. At these depths, footings may be designed for a maximum allowable bearing pressure of 2,500 pounds per


22

square foot (psf) if founded in dense compacted fill soils. The allowable bearing pressures may also be increased by one-third when considering loads of short duration such as wind or seismic forces. The minimum recommended width of footings is 18 inches for continuous footings and 24 inches for square or round footings. Footings should be designed in accordance with the structural engineer’s requirements.

Slabs on grade should be reinforced with reinforcing bars placed at slab mid-height. Slabs should have crack joints at spacings designed by the structural engineer. Columns, if any, should be structurally isolated from slabs. Slabs should be a minimum of 5 inches thick and reinforced with No. 3 rebars at 18 inches on center on center (each way). The slab should be underlain by 2-inch layer of clean sand (S.E. greater than 30). A moisture barrier (10-mil non-recycled plastic sheeting) should be placed below the sand layer if reduction of moisture vapor up through the concrete slab is desired (such as below equipment, living/office areas, etc.), which is in turn underlain by an additional 2-inches of clean sand. If applicable, slabs should also be designed for the anticipated traffic loading using a modulus of subgrade reaction of 140 pounds per cubic inch. All waterproofing measures should be designed by the project architect. The slab subgrade soils underlying the foundation systems should be presoaked in accordance with the recommendations presented in Table 5 prior to placement of the moisture barrier and slab concrete. The subgrade soil moisture content should be checked by a representative of Leighton prior to slab construction.

6.2.3 Foundation Setback

We recommend a minimum horizontal setback distance from the face of slopes for all structural foundations, footings, and other settlement-sensitive structures as indicated on the Table 4 below. The minimum recommended setback distance from the face of a retaining wall is equal to the height of the retaining wall. The distance is measured from the outside bottom edge of the footing, horizontally to the slope or retaining wall face, and is based on the slope or wall height. However, the foundation setback distance may be revised by the geotechnical consultant on a case-by-case basis if the geotechnical conditions are different than anticipated.


23

Table 4

Minimum Foundation Setback from Slope Faces

Slope Height Setback

less than 5 feet 5 feet

5 to 15 feet 7 feet

Please note that the soils within the structural setback area possess poor lateral stability, and improvements (such as retaining walls, sidewalks, fences, pavements, etc.) constructed within this setback area may be subject to lateral movement and/or differential settlement. Potential distress to such improvements may be mitigated by providing a deepened footing or a grade beam foundation system to support the improvement. In addition, open or backfilled utility trenches that parallel or nearly parallel structure footings should not encroach within an imaginary 2:1 (horizontal to vertical) downward sloping line starting 9 inches above the bottom edge of the footing and should also not be located closer than 18 inches from the face of the footing. Deepened footings should meet the setbacks as described above. Also, over-excavation should be accomplished such that deepening of footings to accomplish the setback will not introduce a cut/fill transition bearing condition. Where pipes cross under footings, the footings should be specially designed. Pipe sleeves should be provided where pipes cross through footings or footing walls and sleeve clearances should provide for possible footing settlement, but not less than 1 inch around the pipe.

6.2.4 Settlement For conventional footings, the recommended allowable-bearing capacity is based on a maximum total and differential static settlement 1.5 inches and ¾ of inch, respectively. Since settlements are a function of footing size and contact bearing pressures, some differential settlement can be expected where a large differential loading condition exists.


24

6.2.5 Moisture Conditioning The slab subgrade soils underlying the foundation systems should be presoaked in accordance with the recommendations presented in Table 5 prior to placement of the moisture barrier and slab concrete. The subgrade soil moisture content should be checked by a representative of Leighton prior to slab construction. Presoaking or moisture conditioning may be achieved in a number of ways. But based on our professional experience, we have found that minimizing the moisture loss on pads that has been completed (by periodic wetting to keep the upper portion of the pad from drying out) and/or berming the lot and flooding for a short period of time (days to a few weeks) are some of the more efficient ways to meet the presoaking recommendations. If flooding is performed, a couple of days to let the upper portion of the pad dry out and form a crust so equipment can be utilized should be anticipated.

Table 5 Presoaking Recommendations Based on Finish Grade Soil Expansion

Potential

Expansion Potential Presoaking Recommendations

Very Low Near-optimum moisture content to a minimum depth of 6 inches

Low 120 percent of the optimum moisture content to a minimum depth of 12 inches below slab subgrade

Medium 130 percent of the optimum moisture content to a minimum depth of 18 inches below slab subgrade

High 130 percent of the optimum moisture content to a minimum depth of 36 inches below slab subgrade


25

6.2.6 Post-Tension Foundation Recommendations

As an alternative to the conventional foundations for the buildings, post-tensioned foundations may be used. We recommend that post-tensioned foundations be designed using the geotechnical parameters presented in table below and criteria of the 2013 California Building Code and the Third Edition of Post-Tension Institute Manual. A post-tensioned foundation system designed and constructed in accordance with these recommendations is expected to be structurally adequate for the support of the buildings planned at the site provided our recommendations for surface drainage and landscaping are carried out and maintained through the design life of the project. Based on an evaluation of the depths of fill beneath the building pads and the expansion potential, the attached Table 6 presents the recommended post-tension foundation category for residential buildings for this site.

Table 6 Post-Tensioned Foundation Design Recommendations

Design Criteria

Category I Very Low to

Low Expansion Potential

(EI 0 to 50)

Category II Medium

Expansion Potential

(EI 50 to 90)

Category III High

Expansion Potential

(EI 90 to 130)

Edge Moisture Variation, em

Center Lift:

9.0 feet 8.3 feet 7.0 feet

Edge Lift:

4.8 feet 4.2 feet 3.7 feet

Differential Swell, ym

Center Lift:

0.46 inches 0.75 inches 1.09 inches

Edge Lift:

0.65 inches 1.09 inches 1.65 inches

Perimeter Footing Depth:

18 inches 24 inches 30 inches

Allowable Bearing Capacity

2,000 psf


26

The post-tensioned (PT) foundation and slab should also be designed in accordance with structural considerations. For a ribbed PT foundation, the concrete slabs section should be at least 5 inches thick. Continuous footings (ribs or thickened edges) with a minimum width of 12 inches and a minimum depth of 12 inches below lowest adjacent soil grade may be designed for a maximum allowable bearing pressure of 2,000 pounds per square foot. For a uniform thickness “mat” PT foundation, the perimeter cut off wall should be at least 8 inches below the lowest adjacent grade. However, note that where a foundation footing or perimeter cut off wall is within 3 feet (horizontally) of adjacent drainage swales, the adjacent footing should be embedded a minimum depth of 12 inches below the swale flow line. The allowable bearing capacity may be increased by one-third for short-term loading. The slab subgrade soils should be presoaked in accordance with the recommendation presented in Table 3 above prior to placement of the moisture barrier. The slab should be underlain by a moisture barrier as discussed in Section 6.2.2 above. Note that moisture barriers can retard, but not eliminate moisture vapor movement from the underlying soils up through the slabs. We recommend that the floor covering installer test the moisture vapor flux rate prior to attempting applications of the flooring. "Breathable" floor coverings should be considered if the vapor flux rates are high. A slip-sheet or equivalent should be utilized above the concrete slab if crack-sensitive floor coverings (such as ceramic tiles, etc.) are to be placed directly on the concrete slab. Additional guidance is provided in ACI Publications 302.1R-04 Guide for Concrete Floor and Slab Construction and 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Floor Materials.

6.3 Lateral Earth Pressures and Retaining Wall Design

Table 7 presents the lateral earth pressure values for level or sloping backfill for walls backfilled with and bearing against fully drained soils of very low to low expansion potential (less than 50 per ASTM D4829).


27

Table 7 Static Equivalent Fluid Weight (pcf)

Conditions Level 2:1 Slope

Active 35 55 At-Rest 55 65

Passive 350

(Maximum of 3 ksf)150

(sloping down)

Walls up to 10 feet in height should be designed for the applicable pressure values provided above. If conditions other than those covered herein are anticipated, the equivalent fluid pressure values should be provided on an individual case-by-case basis by the geotechnical engineer. A surcharge load for a restrained or unrestrained wall resulting from automobile traffic may be assumed to be equivalent to a uniform lateral pressure of 75 psf which is in addition to the equivalent fluid pressure given above. For other uniform surcharge loads, a uniform pressure equal to 0.35q should be applied to the wall. The wall pressures assume walls are backfilled with free draining materials and water is not allowed to accumulate behind walls. A typical drainage design is contained in Appendix D. Wall backfill should be compacted by mechanical methods to at least 90 percent relative compaction (based on ASTM D1557). If foundations are planned over the backfill, the backfill should be compacted to 95 percent. Wall footings should be designed in accordance with the foundation design recommendations and reinforced in accordance with structural considerations. For all retaining walls, we recommend a minimum horizontal distance from the outside base of the footing to daylight as outlined in Section 6.2.3. Lateral soil resistance developed against lateral structural movement can be obtained from the passive pressure value provided above. Further, for sliding resistance, the friction coefficient of 0.35 may be used at the concrete and soil interface. These values may be increased by one-third when considering loads of short duration including wind or seismic loads. The total resistance may be taken as the sum of the frictional and passive resistance provided that the passive portion does not exceed two-thirds of the total resistance. To account for potential redistribution of forces during a seismic event, retaining walls providing lateral support where exterior grades on opposites sides differ by


28

more than 6 feet fall under the requirements of 2013 CBC Section 1803.5.12 and/or ASCE 7-10 Section 15.6.1 and should also be analyzed for seismic loading. For that analysis, an additional uniform lateral seismic force of 8H should be considered for the design of the retaining walls with level backfill, where H is the height of the wall. This value should be increased by 150% for restrained walls.

6.4 Geochemical Considerations

Concrete in direct contact with soil or water that contains a high concentration of soluble sulfates can be subject to chemical deterioration commonly known as “sulfate attack.” Laboratory testing should be performed on the soils placed at or near finish grade after completion of site grading to ascertain the corrosivity characteristics. In addition, we recommend that concrete in contact with earth materials be designed in accordance with Section 4 of ACI 318-11 (ACI, 2011).We recommend measures to mitigate corrosion be implemented during design and construction.

6.5 Concrete Flatwork Concrete sidewalks and other flatwork (including construction joints) should be designed by the project civil engineer and should have a minimum thickness of 4 inches. For all concrete flatwork, the upper 12 inches of subgrade soils should be moisture conditioned to at least 2 percent above optimum moisture content and compacted to at least 90 percent relative compaction based on ASTM Test Method D1557 prior to the concrete placement.

6.6 Preliminary Pavement Design The appropriate pavement section will depend on the type of subgrade soil, shear strength, traffic load, and planned pavement life. Pavement sections for the City Streets should be designed in accordance with the City of Oceanside requirements. For planning purposes only, preliminary pavement sections were developed based on an assumed minimum R-value of 5 and potential Traffic Indices (TI) of 4.5, 5, and 6. As required by the City of Oceanside, final pavement designs should be completed after grading operations, but prior to street section


29

construction where an R-value confirmation tests can be performed on actual subgrade materials.

Table 8

Preliminary Pavement Sections

Traffic Index

Preliminary Pavement

4.5 3 inches AC over 8 inches Aggregate Base

5 3 inches AC over 10 inches Aggregate Base

6.5 4 inches AC over 14 inches Aggregate Base

Prior to placement of the aggregate base, the upper 12 inches of subgrade soils should be scarified, moisture-conditioned to at least optimum moisture content and compacted to a minimum 95 percent relative compaction based on American Standard of Testing and Materials (ASTM) Test Method D1557. Class 2 Aggregate Base or Crushed Aggregate Base should then be placed and compacted at a minimum 95 percent relative compaction in accordance with ASTM Test Method D1557. The aggregate base material (AB) should be a maximum of 6 inches thick below the curb and gutter and extend a minimum of 6 inches behind the back of the curb. The AB should conform to and placed in accordance with the approved grading plans, and latest revision of the Standard Specifications Public Works Construction (Greenbook). If pavement areas are adjacent to heavily watered landscaping areas, we recommend some measures of moisture control be taken to prevent the subgrade soils from becoming saturated. It is recommended that the concrete curbing, separating the landscaping area from the pavement, extend below the aggregate base to help seal the ends of the sections where heavy landscape watering may have access to the aggregate base. Concrete swales should be designed if asphalt pavement is used for drainage of surface waters.

6.7 Control of Ground Water and Surface Waters Bio-retention and storm water infiltration systems may cause adverse impacts to the project and adjacent properties. Therefore, unlined infiltration type LID measures are not considered to be appropriate for this site and project. To prevent


30

lateral migration of storm water, a 30-mil HDPE liner should be installed at the bottom and sides of proposed bioretention and infiltration systems. Surface drainage should be controlled at all times and carefully taken into consideration during precise grading, landscaping, and construction of site improvements. Positive drainage (e.g., roof gutters, downspouts, area drains, etc.) should be provided to direct surface water away from structures and improvements and towards the street or suitable drainage devices. Ponding of water adjacent to structures or pavements should be avoided. Roof gutters, downspouts, and area drains should be aligned so as to transport surface water to a minimum distance of 5 feet away from structures. The performance of structural foundations is dependent upon maintaining adequate surface drainage away from structures. Water should be transported off the site in approved drainage devices or unobstructed swales. We recommend a minimum flow gradient for unpaved drainage within 5 feet of structures of 2 percent sloping away. The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow ground water conditions where previously none existed. Maintaining adequate surface drainage and controlled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements such as heaving and shrinkage due to the change in moisture content of foundation soils, which may cause distress to a structure and improvements, moisture content of the soils surrounding the structure should be kept as relatively constant as possible. Below grade planters should not be situated adjacent to structures or pavements unless provisions for drainage such as catch basins and drains are made. All area drain inlets should be maintained and kept clear of debris in order to function properly. In addition, landscaping should not cause any obstruction to site drainage. Rerouting of drainage patterns and/or installation of area drains should be performed, if necessary, by a qualified civil engineer or a landscape architect.

6.8 Construction Observation The recommendations provided in this report are based on preliminary design information and subsurface conditions disclosed by widely spaced excavations. The interpolated subsurface conditions should be checked by Leighton in the


31

field during construction. Construction observation of all onsite excavations and field density testing of all compacted fill should be performed by a representative of this office. We recommend that all excavations be mapped by the geotechnical consultant during grading to determine if any potentially adverse geologic conditions exist at the site.

6.9 Plan Review Final project grading and foundation plans should be reviewed by Leighton as part of the design development process to ensure that recommendations in this report are incorporated in project plans.


32

7.0 LIMITATIONS The conclusions and recommendations presented in this report are based in part upon data that were obtained from a limited number of observations, site visits, excavations, samples, and tests. Such information is by necessity incomplete. The nature of many sites is such that differing geotechnical or geological conditions can occur within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Therefore, the findings, conclusions, and recommendations presented in this report can be relied upon only if Leighton has the opportunity to observe the subsurface conditions during grading and construction of the project, in order to confirm that our preliminary findings are representative for the site.

Figures and Plate

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/AirbusDS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, andthe GIS User Community, Esri, HERE, DeLorme, MapmyIndia, ©OpenStreetMap contributors

³0 2,000 4,000

Feet

Figure 1Scale:

LeightonBase Map: ESRI ArcGIS Online 2015Thematic Information: Leighton

1 " = 2,000 '

Project: 10864.001 Eng/Geol: WDO/MDJ

Map Saved as V:\Drafting\10864\001\Maps\10864.001_F01_SLM_2014-12-2.mxd on 12/23/2014 10:23:08 AM

Author: (mmurphy)

Date: June 2015 SITE LOCATION MAPCity VenturesOceanside 2

Oceanside, California

ApproximateSite Location

Feet

400 80

GEOLOGIC CROSS-SECTION A-A'City Ventures

Oceanside 2


Project:

Scale:

10864.001

1"=40'

Eng/Geol: WDO/MDJ

Date: June 2015

Reference:

Author: MAM

P:\10864\001\2015-05-28\10864.001_F02_CSAA_2015-05-29.DWG (06-02-15 9:42:55AM) Plotted by: mmurphy

Leighton

Figure 2

LEGEND

?

?

?

?

?

A

p

p

r

o

x

im

a

t

e

F

a

u

lt

L

in

e

L

o

c

a

t

io

n

P:\10864\001\2015-05-28\10864.001_P01_GM_2015-05-28.DWG (06-02-15 9:44:05AM) Plotted by: mmurphy

Proj: 10864.001

GEOTECHNICAL MAPCity Ventures

Oceanside 2


PLATE 1

Eng/Geol: WDO/MDJ

Scale: 1"=40' Date: June 2015

Drafted By: MAM Checked By:

Leighton

LEGEND

CITY VENTURES HOMEBUILDING, INC.

Documents

Transcript of CITY VENTURES HOMEBUILDING, INC.