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HomeMy WebLinkAboutCDP 98-40; Severino Single Family Residence; Geotechnical Investigation; 1998-04-29REPORT OF GEOTECHNICAL INVESTIGATION PARCEL 3 MAP NO. 16177 PARK DRIVE CARLSBAD, CALIFORNIA PREPARED FOR: SEVERING CONSTRUCTION 2186 BATISTA AVENUE VISTA, CALIFORNIA 92084 PREPARED BY: SOUTHERN CALIFORNIA SOIL AND TESTING, INC. 6280 RIVERDALE STREET SAN DIEGO, CALIFORNIA 92120 Providing Professional Engineering Services Since 1959 SOUTHERN CALIFORNIA SOIL & TESTING, INC. 6280 Riverdale Street, San Diego, CA 92120 P.O. Box 600627, San Diego, CA 92160-0627 619-280-4321, FAX 619-280-4717 April 29, 1998 Severino Construction 2186 Batista Avenue Vista, California 92084 SCS&T9811024.1 SUBJECT: Report of Geotechnical Investigation, Parcel 3, Map No. 16177, Park Drive, Carlsbad, California. Gentlemen: In accordance with your request, we have completed a geotechnical investigation for the subject project. The findings and recommendations of our study are presented herewith. In general, we found the site suitable for the proposed development provided the recommendations presented in the attached report are followed. The main geotechnical consideration affecting the proposed site development is the presence of a relatively thin mantle of loose surficial soils. This condition will require special site preparation consideration as described hereinafter. If you should have any questions after reviewing the findings and recommendations contained in the attached report, please do not hesitate to contact this office. This opportunity to be of professional service is sincerely appreciated. Respectfully submitted, SOUTHERN CALIFORNIA SOIL & TESTING, INC. DanielVB. Adltf, R.C.'S. #36037 DBA:CRB:mw cc: (6) Submitted Curtis R. Burdett, C.E.G. #1090 TABLE OF CONTENTS PAGE Introduction and Project Description 1 Project Scope 1 Findings 2 Site Description 2 General Geology and Subsurface Conditions 3 Geologic Setting and Soil Description 3 Santiago Formation 3 Alluvial Deposits 3 Topsoils 3 Artificial Fill 3 Tectonic Setting 3 Geologic Hazards 4 General 4 Ground Shaking 4 Landslide Potential and Slope Stability 5 Liquefaction 5 Flooding 5 Tsunamis 5 Seiches 5 Groundwater 5 Conclusions 6 General 6 Recommendations 6 Grading 6 Site Preparation 6 Wet Soils 6 Surface Drainage 6 Foundations 7 General 7 Reinforcement 7 Foundation Excavation Observation 7 Settlement Characteristics 7 Expansive Characteristics 8 Slabs-on-Grade 8 TABLE OF CONTENTS (continued) PAGE Concrete Slabs-on-Grade 8 Grading and Foundation Plan Review 8 Earth Retaining Walls 8 Foundations 8 Passive Pressure 8 Active Pressure 9 Waterproofing and Subdrain Observation 9 Backfill 9 Factor of Safety 9 Limitations 9 Review, Observation and Testing 9 Uniformity of Conditions 10 Change in Scope 10 Time Limitations 10 Professional Standard 10 Client's Responsibility 11 Field Explorations 11 Laboratory Testing 11 ATTACHMENTS FIGURE Figure 1 Site Vicinity Map, Follows Page 1 PLATES Plates 1 Plot Plan Plate 2 Unified Soil Classification Chart Plates 3-5 Trench Logs Plate 6 Grain Size Distribution Plate 7 Maximum Dry Density and Optimum Moisture Content Expansion Index Test Results Plate 8 Direct Shear Test Results Plate 9 Retaining Wall Subdrain Detail APPENDIX A - References SOUTHERN CALIFORNIA SOIL & TESTING, INC. 6280 Riverdale Street, San Diego, CA 92120 PO. Box 600627, San Diego, CA 92160-0627 619-280-4321, FAX 619-280-4717 GEOTECHNICAL INVESTIGATION PARCEL 3. MAP NO. 16177 PARK DRIVE CARLSBAD. CALIFORNIA INTRODUCTION AND PROJECT DESCRIPTION This report presents the results of our geotechnical investigation for a proposed residential site, located west of Park Drive, in the City of Carlsbad, California. The site location is shown on the vicinity map provided as Figure Number 1 on the following page. It is our understanding that the site will be developed to receive a one-and/or two-story residential structure, with an associated paved driveway. The structure will be of wood-frame construction. Shallow foundations and a concrete slab-on-grade floor system are proposed. Grading will consist of cuts and fills less than about five feet from existing grades. A masonry retaining wall up to 5.5 feet in height is proposed. To assist in the preparation of this report, we were provided with a site plan prepared by Joseph K. Lukoski, dated April 8, 1998. The site configuration, topography and approximate locations of our subsurface explorations are shown on Plate Number 1 of this report. PROJECT SCOPE The investigation consisted of: surface reconnaissance, subsurface explorations, obtaining representative disturbed and undisturbed samples, laboratory testing, analysis of the field and laboratory data, research of available geological literature pertaining to the site, and preparation of this report. More specifically, the intent of this analysis was to: a) Explore the subsurface conditions to the depths influenced by the proposed construction. \>^\\ j A ^x?A4l= J 5t sM^1 -< ";>^t!;i*^4% V ^^f^y i ^:'«r^S^~!±, ^Wl^a^V^Y^^^S•"' .id/c^/^-4 >f$^ w ^JL^d^^«ln^» yX SOUTHERN CALIFORNIA ^^y SOIL A TESTING, INC. PARCEL 3 MAP NO. 16177 BY:DBA JOB NUMBER : 981 1024 DATE: 04-28-98 FIGURE NO. 1 SCS&T9811024.1 April 29, 1998 Page No. 2 b) Evaluate, by laboratory tests, the pertinent engineering properties of the various strata which will influence proposed development, including their bearing capacities, expansive characteristics and settlement potential. c) Describe the general geology at the site including possible geologic hazards which could have an effect on the site development. d) Develop soil engineering criteria for site grading and provide design information regarding the stability of cut and fill slopes. e) Address potential construction difficulties and provide recommendations concerning these problems. f) Recommend an appropriate foundation system for the type of structure anticipated and develop soil engineering design criteria for the recommended foundation design. It was not within the scope of our services to perform laboratory tests to evaluate the chemical characteristics of the on-site soils in regard to their potentially corrosive impact to on-grade concrete and below grade improvements. If desired, we can obtain samples of representative soils and submit them to a chemical analysis laboratory for analysis. We suggest that such samples be obtained after mass site grading is complete and the soils that can affect concrete and other improvements are in place. Further, it should be understood that Southern California Soil and Testing, Inc. does not practice corrosion engineering. If such an analysis is considered necessary, we recommend that the client retain an engineering firm that specializes in this field to consult with them on this matter. FINDINGS SITE DESCRIPTION The subject site consists of a flag-shaped parcel of land, approximately 13,815 square feet in size, and is accessed via an unpaved private road easement extending west from Park Drive in the City of Carlsbad. The property is bounded on the north, south and east by developed or undeveloped residential lots and on the west by the proposed extension of James Drive and a drainage channel. The site has been graded but no improvements currently exist at the site. The grading has resulted in a 10-foot-high cut slope along the SCS&T 9811024.1 April 29, 1998 Page No. 3 eastern portion of the pad, a cut slope along a section of the northern portion of the pad, and a few feet of fill on the western portion of the pad. Vegetation consists of a moderate growth of grasses and forbs. GENERAL GEOLOGY AND SUBSURFACE CONDITIONS GEOLOGIC SETTING AND SOILS DESCRIPTIONS: The site is located in the Coastal Plains Physiographic Province of San Diego County. The project area of the property is underlain by Tertiary- age and Quaternary-age sedimentary deposits, associated surficial soils, and artificial fill. The following presents a description of each of the soil units encountered on the site. SANTIAGO FORMATION: The oldest materials encountered at the site are the sandstones of the Eocene Santiago Formation. These materials consist of tan, moist to very moist, dense to very dense silty sands. ALLUVIAL DEPOSITS: Unconformably overlying the Santiago Formation on the western portion of the site are Quaternary-age alluvial deposits consisting of reddish-brown, very moist to wet, loose to medium dense, silty sands. The alluvial deposits appear to range up to approximately five feet thick. TOPSOILS: Natural ground topsoils remain on portions of the project area. The encountered topsoils range from approximately one to two feet in thickness and consist of dark brown, wet, loose, silty sands. The topsoils have been removed from most of the site by the prior grading operations. ARTIFICIAL FELL: The western portion of the building pad is underlain by up to about five feet of artificial fill consisting of dark brown, wet, loose, silty sand. TECTONIC SETTING No major faults are known to traverse the subject site but it should be noted that much of Southern California, including the San Diego County area is characterized by a series of Quaternary-age fault zones which consist of several individual, en echelon faults that generally strike in a northerly to northwesterly direction. Some of these fault zones (and the individual faults within the zone) are classified as active while others are classified as only potentially active according to the criteria of the California Division of SCS&T 9811024.1 April 29, 1998 Page No. 4 Mines and Geology. Active fault zones are those which have shown conclusive evidence of faulting during the Holocene Epoch (the most recent 11,000 years) while potentially active fault zones have demonstrated movement during the Pleistocene Epoch (11,000 to 2 million years before the present) but no movement during Holocene time. A review of available geologic maps indicates that the active Rose Canyon Fault Zone is located approximately 13 miles west of the subject site. Other active fault zones in the region that could possibly affect the site include the Coronado Bank and San Clemente Fault Zones to the west; the Elsinore and San Jacinto Fault Zones to the northeast; and the Agua Blanca and San Miguel Fault Zones to the south. GEOLOGIC HAZARDS GENERAL: No geologic hazards of sufficient magnitude to preclude development of the site as we presently contemplate it are known to exist. In our professional opinion and to the best of our knowledge, the site is suitable for the proposed development. GROUND SHAKING: A likely geologic hazard to affect the site is ground shaking as a result of movement along one of the active fault zones mentioned above. The maximum bedrock accelerations that would be attributed to a maximum probable earthquake occurring along the nearest fault segments of selected fault zones that could affect the site are summarized in the following Table I. TABLE I Fault Zone Rose Canyon Coronado Bank Elsinore San Diego Trough San Jacinto Distance 6 miles 21 miles 23 miles 30 miles 48 miles Maximum Probable Earthquake 6.5 magnitude 7.0 magnitude 7.3 magnitude 7.3 magnitude 7.8 magnitude Maximum Bedrock Acceleration 0.30 g 0.15 g 0.16 g 0.12 g 0.11 g Probable ground shaking levels at the site could range from slight to moderate, depending on such factors as the magnitude of the seismic event and the distance to the epicenter. It is likely the site will experience the effects of at least one moderate to large earthquake during the life of the proposed structure. SCS&T 9811024.1 April 29, 1998 Page No. 5 Generally two-thirds the peak bedrock accelerations is considered when designing for seismic conditions. CDMG Open File Report 92-1, Peak Acceleration from Maximum Credible earthquakes in California (Rock and Stiff Soil Sites) shows a value of 0.5 g for the project area (Mualchin and Jones, 1992). LANDSLIDE POTENTIAL AND SLOPE STABILITY: As part of this investigation we reviewed the publication, "Landslide Hazards in the Northern Part of the San Diego Metropolitan Area," by Tan, 1995. This reference is a comprehensive study that classifies San Diego County into areas of relative landslide susceptibility. The subject site is located in classification 3-1. The 3-1 classification is assigned to areas considered generally susceptible to slope movement. Slopes within the 3-1 classification are considered at or near their stability limits due to steep slopes and can be expected to fail locally when adversely modified. Sites within this classification are located outside the boundaries of known landslides but contain observably unstable slopes that may be underlain by weak materials and/or adverse geologic structure. A review of the available aerial photographs revealed the presence of several topographic features that appeared to possibly be shallow, surficial slope failures. Proper landscaping and slope maintenance techniques should mitigate the potential for future slope instability problems. LIQUEFACTION: The materials at the site are not subject to liquefaction due to such factors as soil density, grain-size distribution, and groundwater conditions. FLOODING: Flooding is not expected to present a hazard to the proposed development. The site is located outside the boundary of both the 100-year and the 500-year flood plans. TSUNAMIS: Tsunamis are great sea waves produced by submarine earthquakes or volcanic eruptions. Due to the site's elevation and location, it is not likely to experience a tsunami. SEICHES: Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays or reservoirs. It is not likely the site will be affected by seiche activity. GROUNDWATER: No groundwater was encountered in our subsurface explorations. It should be recognized, however, that minor groundwater seepage problems might occur after development of a site even where none were present before development. These are usually minor phenomena and are often the result of an alteration in drainage patterns and/or an increase in irrigation water. Based on the SCS&T 9811024.1 April 29, 1998 Page No. 6 permeability characteristics of the soil and the anticipated usage and development, it is our opinion that any seepage problems which may occur will be minor in extent. It is further our opinion that these problems can be most effectively corrected on an individual basis if and when they occur. CONCLUSIONS GENERAL In general, no geotechnical conditions were encountered which would preclude the development of the site as presently proposed, provided the recommendations presented herein are followed. The subject site is underlain by a relatively thin mantle of loose fill, alluvium, and topsoils deposits extending to a maximum depth of about five feet. The depositsare considered unsuitable, in their present condition, for the support of settlement-sensitive improvements and will require removal and replacement as compacted fill. m RECOMMENDATIONS --** m GRADING •w*. SITE PREPARATION: Site preparation should begin with the removal of existing vegetation and deleterious matter from the area of the site to be developed. Existing fill, alluvium and slopewash deposits "MM underlying proposed fill areas and settlement-sensitive improvements should be removed to firm natural ground (exterior patio and driveway included). Based on our findings, it is anticipated that maximum *«R removal depth will be about five feet. The minimum horizontal limits of this operation should be five feet4H away from the perimeter of the improvements. The bottom of the excavations should be scarified to a «««» depth of at least six inches, moisture conditioned and compacted to at least 90 percent. am •m WET SOILS: The surficial soils encountered in our trenches were in a very moist and wet condition. <tm This material will have to be aerated prior to placement as compacted fill. .m SURFACE DRAINAGE: Pad drainage should be designed to collect and direct surface water away from "* proposed structure and the top of slopes, and toward approved draining facilities. Rain gutters are recommended. SCS&T 9811024.1 April 29, 1998 Page No. 7 The ground around the proposed structure should be graded so that surface water flows rapidly away from the structure without ponding. In general, we recommend that the ground adjacent to structures slope away at a gradient of at least two percent. Densely vegetated areas where runoff can be impaired should have a minimum gradient of at least five percent within the first five feet from the structure. The client should be advised that drainage patterns approved at the time of fine grading should be maintained throughout the life of the proposed structures. They should also be advised to limit site irrigation to the minimum necessary to sustain landscape growth. Should excessive irrigation, impaired drainage, or unusually high rainfall occur, saturated zones of perched groundwater conditions may occur. FOUNDATIONS GENERAL: Conventional spread foundations may be utilized for the support of the proposed structure. The footings should have a minimum depth of 12 inches and 18 inches below lowest adjacent finish pad grade for single and two story structures, respectively. A minimum width of 12 inches and 24 inches is recommended for continuous and isolated footings, respectively. An allowable soil bearing capacity of 2000 psf may be assumed for said footings with these minimum dimensions. This bearing capacity may be increased by one-third when considering wind and/or seismic forces. A minimum setback of seven feet should exist between the bottom of footing and the face of fill slopes. For retaining walls the minimum setback should be ten feet. REINFORCEMENT: Both exterior and interior continuous footings should be reinforced with at least one No. 5 bar positioned near the bottom of the footing and one No. 5 bar positioned near the top of the footing. This reinforcement is based on soil characteristics and is not intended to be in lieu of reinforcement necessary to satisfy structural considerations. FOUNDATION EXCAVATION OBSERVATION: It is recommended that all foundation excavations be approved by a representative from this office prior to forming or placement of reinforcing steel. SETTLEMENT CHARACTERISTICS: The anticipated total and/or differential settlements for the proposed structure may be considered to be within tolerable limits provided the recommendations presented in this report are followed. It should be recognized that minor cracks normally occur in concrete slabs and foundations due to shrinkage during curing or redistribution of stresses and some cracks may be anticipated. Such cracks are not necessarily an indication of excessive vertical movements. SCS&T9811024.1 April 29, 1998 Page No. 8 EXPANSIVE CHARACTERISTICS: The prevailing foundation soils was found to be nondetrimentally expansive. The recommendations presented in this report reflect this condition. SLABS-ON-GRADE CONCRETE SLABS-ON-GRADE: Concrete slabs-on-grade should have a thickness of at least four inches and be reinforced with at least No. 3 reinforcing bars placed at 18 inches on center each way. Slab reinforcement should be placed approximately at mid-height of the slab and should extend at least six inches down into the perimeter footings. The slabs should be underlain by a four-inch blanket of clean, poorly graded, coarse sand or crushed rock. This blanket should consist of 100 percent material passing the half-inch screen and no more than ten percent and five percent passing #100 and #200 sieve, respectively. Where moisture sensitive floor coverings are planned, a visqueen barrier should be placed over the sand layer. To allow for proper concrete curing, the visqueen should be overlain by at least two inches of sand. GRADING AND FOUNDATION PLAN REVIEW The grading and foundation plans should be submitted to this office for review to ascertain that the recommendations contained in this report are implemented and no revised recommendations are necessary due to changes in the development scheme. EARTH RETAINING WALLS FOUNDATIONS: The recommendations presented in the foundation section of this report are also applicable to earth retaining structures. PASSIVE PRESSURE: The passive pressure for the prevailing soil conditions may be considered to be 350 pounds per square foot per foot of depth. This pressure may be increased one-third for seismic loading. The coefficient of friction for concrete to soil may be assumed to be 0.35 for the resistance to lateral movement. When combining frictional and passive resistance, the friction should be reduced by one-third. The upper 12 inches of soil should not be considered when calculating passive pressures for exterior walls. SCS&T 9811024.1 April 29, 1998 Page No. 9 ACTIVE PRESSURE: The active soil pressure for the design of unrestrained earth retaining structures with level backfills may be assumed to be equivalent to the pressure of a fluid weighing 33 pounds per cubic foot. For restrained walls an equivalent fluid pressure of 48 pcf may be assumed. An additional 15 pcf should be added to said values for 2:1 (horizontal to vertical) sloping conditions. These pressures do not consider any other surcharge loads. If any are anticipated, this office should be contacted for the necessary increase in soil pressure. This value assumes a granular and drained backfill condition. Waterproofing specifications and details should be provided by the project architect. A typical wall subdrain detail is provided on the attached Plate Number 9. WATERPROOFING AND SUBDRAIN OBSERVATION: The geotechnical engineer should be requested to verify that waterproofing has been applied and that the subdrain has been properly installed. However, unless specifically asked to do so, we will not verify proper application of the waterproofing. BACKFILL: All backfill soils should be compacted to at least 90% relative compaction. Expansive or clayey soils should not be used for backfill material. The wall should not be backfilled until the masonry has reached an adequate strength. FACTOR OF SAFETY: The above values, with the exception of the allowable soil bearing pressure, do not include a factor of safety. Appropriate factors of safety should be incorporated into the design to prevent the walls from overturning and sliding. LIMITATIONS REVIEW, OBSERVATION AND TESTING The recommendations presented in this report are contingent upon our review of final plans and specifications. Such plans and specifications should be made available to the geotechnical engineer and engineering geologist so that they may review and verify their compliance with this report and with Chapter 70 of the Uniform Building Code. It is recommended that Southern California Soil & Testing, Inc. be retained to provide continuous soil engineering services during the earthwork operations. This is to verify compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. SCS&T9811024.1 April 29, 1998 Page No. 10 UNIFORMITY OF CONDITIONS The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration locations and on the assumption that the soil conditions do not deviate appreciably from those encountered. It should be recognized that the performance of the foundations and/or cut and fill slopes may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the geotechnical engineer so that he may make modifications if necessary. CHANGE IN SCOPE This office should be advised of any changes in the project scope or proposed site grading so that we may determine if the recommendations contained herein are appropriate. This should be verified in writing or modified by a written addendum. TIME LIMITATIONS The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur with the passage of time, whether they be due to natural processes or the work of man on this or adjacent properties. In addition, changes in the Standards-of-Practice and/or Government Codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control. Therefore, this report should not be relied upon after a period of two years without a review by us verifying the suitability of the conclusions and recommendations. PROFESSIONAL STANDARD In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the locations where our borings, surveys, and explorations are made, and that our data, interpretations, and recommendations be based solely on the information obtained by us. We will be responsible for those data, interpretations, and recommendations, but shall not be responsible for the interpretations by others SCS&T 9811024.1 April 29, 1998 Page No. 11 ** of the information developed. Our services consist of professional consultation and observation only, and ""* no warranty of any kind whatsoever, express or implied, is made or intended in connection with the work m performed or to be performed by us, or by our proposal for consulting or other services, or by our **" furnishing of oral or written reports or findings. ,m CLIENT'S RESPONSIBILITY <m — It is the responsibility of Severino Construction, or their representatives to ensure that the information «* and recommendations contained herein are brought to the attention of the structural engineer and architect •m for the project and incorporated into the project's plans and specifications. It is further their responsibility «• to take the necessary measures to insure that the contractor and their subcontractors carry out such .„ recommendations during construction. m FIELD EXPLORATIONS •<*» Three subsurface explorations were made at the locations indicated on the attached Plate Number 1 on m February 5, 1998. These explorations consisted of trenches excavated with a backhoe. The field work was conducted under the observation of our engineering geology personnel. m The subsurface explorations were carefully logged when made. These logs are presented on the following Plates Number 3, 4 and 5. The soils are described in accordance with the Unified Soils Classification System as illustrated on the attached simplified chart on Plate Number 5. In addition, a verbal textural •?% description, the wet color, the apparent moisture and the density or consistency are provided. The density >MT of granular soils is given as either very loose, loose, medium dense, dense or very dense. The consistency of silts or clays is given as either very soft, soft, medium stiff, stiff, very stiff, or hard. •KH *m Disturbed and undisturbed samples of typical and representative soils were obtained and returned to the laboratory for testing. •a» LABORATORY TESTING m -MM Laboratory tests were performed in accordance with the generally accepted American Society for Testing and Materials (ASTM) test methods or suggested procedures. A brief description of the tests performed '<Mi is presented below: — SCS&T9811024.1 April 29, 1998 Page No. 12 •¥•* ** a) CLASSIFICATION: Field classifications were verified in the laboratory by visual examination. The final soil classifications are in accordance with the Unified Soil Classifica- * tion System. »'H» m b) MOISTURE-DENSITY: In-place moisture contents and dry densities were determined for — representative soil samples. This information was an aid to classification and permitted ** recognition of variations in material consistency with depth. The dry unit weight is '- determined in pounds per cubic foot, and the in-place moisture content is determined as a *• percentage of the soil's dry weight. The results are summarized in the boring and trench logs. * c) GRAIN SIZE DISTRIBUTION: The grain size distribution was determined for representa- „ tive samples of the native soils in accordance with ASTM D422. The results of these tests are .» presented on Plate Number 6. ws m d) COMPACTION TEST: The maximum dry density and optimum moisture content of a typical soil as determined in the laboratory in accordance with ASTM Standard Test D-1557- m 91, Method A. The results of this test are presented on Plate Number 7. em — e) EXPANSION INDEX TEST: An expansion index test on remolded samples was performed on representative samples of soils likely to be present at finish grade. The test was performed•*^ on the portion of the sample passing the #4 standard sieve. The sample was brought to optimum moisture content and then dried back to a constant moisture content for 12 hours at "*•» 230 +_ 9 degrees Fahrenheit. The specimen was then compacted in a 4-inch-diameter mold l-W in two equal layers by means of a tamper, then trimmed to a final height of 1 inch, and brought to a saturation of approximately 50 percent. The specimen was placed in a<•* consolidometer with porous stones at the top and bottom, a total normal load of 12.63 pounds was placed (144.7 psf), and the sample was allowed to consolidate for a period of 10 minutes. w*. The sample was allowed to become saturated, and the change in vertical movement was recorded until the rate of expansion became nominal. The expansion index is reported on the M£ attached Plate Number 7 as the total vertical displacement times the fraction of the sample passing the #4 sieve times 1000. SCS&T 9811024.1 April 29, 1998 Page No. 13 CLASSIFICATION OF EXPANSIVE SOIL EXPANSION INDEX POTENTIAL EXPANSION 1-20 very low 21-50 low 51-90 medium 91-130 high Above 130 very high f) DIRECT SHEAR TESTS: A direct shear test was performed to determine the failure envelope based on yield shear strength. The shear box was designed to accommodate a sample having a diameter of 2.375 inches or 2.50 inches and a height of 1.0 inch. Samples were tested at different vertical loads and a saturated moisture content. The shear stress was applied at a constant rate of strain of approximately 0.05 inch per minute. The results of this test are presented on the attached Plate Number 8. SUBSURFACE EXPLORATION LEGEND UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION I. COARSE GRAINED, more than half of material is lareer than No. 200 sieve size. GRAVELS More than half of coarse fraction is larger than No. 4 sieve size but smaller than 3". CLEAN GRAVELS GROUP SYMBOL GW GP SANDS More than half of coarse fraction is smaller than No. 4 sieve size. II. GRAVELS WITH FINES (Appreciable amount of fines) CLEAN SANDS SANDS WITH FINES (Appreciable amount of fines) FINE GRAINED, more than half of material is smaller than No. 200 sieve size. SILTS AND CLAYS Liquid Limit SILTS AND CLAYS Liquid Limit greater than 50 GM GC SW SP SM SC ML CL OL MH CH OH HIGHLY ORGANIC SOILS PT y - Water level at time of excavation or as indicated US - Undisturbed, driven ring sample or tube sample SC - Sand Cone CON - Consolidation El - Expansion Index TYPICAL NAMES Well graded gravels, gravel-sand mixtures, little or no fines. Poorly graded gravels, gravel sand mixtures, little or no fines. Silty gravels, poorly graded gravel- sand-silt mixtures. Clayey gravels, poorly graded gravel- sand, clay mixtures. Well graded sand, gravelly sands, little or no fines. Poorly graded sands, gravelly sands, little or no fines. Silty sands, poorly graded sand and silty mixtures. Clayey sands, poorly graded sand and clay mixtures. Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt- sand mixtures with slight plasticity. Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. Organic silts and organic silty clays or low plasticity. Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. Inorganic clays of high plasticity, fat clays. Organic clays of medium to high plasticity. Peat and other highly organic soils. CK - Undisturbed chunk sample <^ - Bulk Sample SP - Standard penetration sample DS - Direct Shear SA - Sieve Analysis PI - Plastic Index <d£SOUTHERN CALIFORNIA y SOIL & TESTING, INC. PARCEL 3 MAP NO. 16177 BY: DBA JOB NUMBER: 9811024 DATE: 04-28-98 Plate No. 2 flM LOG OF TEST TRENCH NUMBER Tl Date Excav Equipment: Surface Ele DEPTH (ft)-I 2 3 - 4 _ - 5 - a ted: vatio GRAPHIC LOG-.- 2/5/98 T^ BACKHOE Prr n(ftV De SUMMARY OF SUBSURFACE CONDITIONS ALLUVIUM (Qal) - Light Brown, Wet, Loose, VERY SILTY SAND (SM) SANTIAGO FORMATION (Tsd) - Tan, Moist to Very Moist, Very Dense, SILTY SAND (SM), Moderately Cemented Trench Ended at 6 Feet gged by >ject Ms pth to V SAMPLES UNDISTURBEDCK CK m 1 I JBR mager /ater(f MOISTURE (%)15.2 15.0 DBA tV H D 112.2 113.9 LABORATORYTESTSXr\ SOUTHERN CALIFORNIA Pr°Ject Name: Pr°Ject No' Plate No' VflpyenTT „ „ „ PARCELS 98H024 3NTTX SOIL & TESTING, INC. MAp NQ mij J Date Excavated: Equipment: LOG OF TEST TRENCH NUMBER T2 2/5/98 Logged by:JBR BACKHOE Project Manager: Surface Elevation(ft):Depth to Water(ft): <c K (^WQ - 1 - 2 - 0 4 , 6 - 7 - 8 -GRAPHIC LOGSUMMARY OF SUBSURFACE CONDITIONS FILL (Qaf) - Dark Brown, Wet, Loose, SILTY SAND (SM) ALLUVIUM (Qal) - Red Brown, Very Moist, Loose to Medium Dense, SILTY SAND (SM) SANTIAGO FORMATION (Tsd) - Tan, Moist, Very Dense, SILTY SAND (SM) Pit Ended at 7.5 Feet SAMPLES UNDISTURBEDCK CK X_l 03 it MOISTURE (%)E-' £ H 2P ><?C* ooa LABORATORYTESTSSOUTHERN CALIFORNIA SOIL & TESTING, INC. Project Name: PARCEL 3 MAP NO. 16177 Project No. 9811024 Plate No. 4 Date Excavated: Equipment: LOG OF TEST TRENCH NUMBER T3 2/5/98 Logged by:JBR BACKHOE Project Manager: DBA Surface Elevation(ft):Depth to Water(ft):DEPTH (ft1 -J 2 3 4 - cJ OOJ GRAPHICSUMMARY OF SUBSURFACE CONDITIONS TOPSOIL - Brown, Wet, Soft, VERY SILTY SAND (SM) SANTIAGO FORMATION (Tsd) - Tan, Moist, Very Dense, VERY SILTY SAND (SM) Trench Ended at 5 Feet SAMPLES QWm £UNDISTUlCK J CQ /— ^l£ LL]MOISTURE-' ZP Q & £O LABORATTESTSSOUTHERN CALIFORNIA SOIL & TESTING, INC. Project Name: PARCEL 3 MAP NO. 16177 Project No. 9811024 Plate No. 5 •SCALE CORRECTION" t 1 JUJ en Ol 0IX UJ N 3 c(3 PERCENT FINER CO 2 CO in O u 5 5(/) UJ HI 03ffiOO § § UJ N CO UJ CO Qa. CO y£X. SOUTHERN CALIFORNIA X=j=X SOIL AND TESTING PROJECT: PARCEL 3 MAP NO. 16177 BY: DBA JOB NUMBER: 9811024 DATE: 04-28-98 Plate No. 6 MAXIMUM DENSITY ft OPTIMUM MOISTURE CONTENT ASTM D1557-91 METHOD A SAMPLE DESCRIPTION Maximum Density (pet) Optimum Moisture Cont(«/«) TI @ r-z1 Light Brown, Very Silty Sand 116.9 12.0 EXPANSION INDEX TEST RESULTS SAMPLE TI @ r-21 T3 @ 2' CONDITION Remolded Remolded INITIAL M.C.C/.)10.5 12.2 INITIAL DENSITY (PCFJ 108.0 101.8 FINAL M.C. («/.)20.2 21.8 NORMAL STRESS (PSF)|144.7 144.7 EXPANSION INDEX 21 SOUTHERN CALIFORNIA SOIL & TESTING, INC.BY: PARCEL 3 MAP NO. 16177 DBA JOB NUMBER: 9811024 DATE: 04-28-98 Plate No. 7 u_ CO COCO111cc CO UJ X CO DIRECT SHEAR SUMMARY 1 2M L (0.518) (1.036) 2 2L (2.070) NORMAL STRESS, KSF (2 72" SAMPLE) SAMPLE T1 @ V-2' DESCRIPTION Remolded to 90% ANGLE OF INTERNAL FRICTION 32 COHESION INTERCEPT (PSF) 200 PROVING RING No. /G[\ SOUTHERN CALIFORNIA \|/ SOIL & TESTING, INC. PARCEL 3 MAP NO. 16177 BY: DBA JOB NUMBER: 9811024 DATE: 04-28-98 PLATE No.: g APPENDIX A «- SCS&T 9811024.1 April 29, 1998 Appendix A, Page No. 1 •K * REFERENCES '*• m Anderson, J.G., Rockwell, R.K. and Agnew, D.C., 1989, Past and Possible Future Earthquakes of m Significance to the San Diego Region, Earthquake Spectra. Volume 5, No. 2, 1989. m Eisenberg, L.I., 1985, Pleistocene Faults and Marine Terraces, Northern San Diego County in On the m Manner of Deposition of the Eocene Strata in Northern San Diego County, San Diego Association of Geologists Annual Field Trip Guidebook, Editor: P.L. Abbott. m Jennings, C.W., 1975, Fault Map of California, California Division of Mines and Geology, Map No. 1, •*« Scale 1:750,000.•m "* Kern, P., 1989, Earthquakes and Faults in San Diego County, Pickle Press, 73 pp. ^*i Mualchin, L. and Jones, A.L., 1992, Peak Acceleration from Maximum Credible earthquakes in California •Ml (Rock and Stiff-Soil Sites) California Division of Mines and Geology Open-File Report 92-1. '**M m Tan, S.S. and Giffen, D.G., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego County, California, California Division of Mines and Geology Open-File Report 95-04. *m «B Wesnousky, S.G., 1986, "Earthquakes, Quaternary Faults, and Seismic Hazards in California," in Journal of Geophysical Research, Vol. 91, No. B12, pp 12,587 to 12,631, November 1986. « TOPOGRAPHIC MAPS m County of San Diego, 1975, Map Sheet 358-1665; Scale: 1 inch = 200 feet. m "*• U.S. Geological Survey, 1948, 7 l/i Minute Topographic Maps, San Luis Rey Quadrangle. >« •« U.S. Geological Survey, 1968, 7 l/2 Minute Topographic Maps, San Luis Rey Quadrangle. ><• - U.S. Geological Survey, 1975, 7 l/i Minute Topographic Maps (Photorevised), San Luis Rey Quadrangle. SCS&T 9811024.1 April 29, 1998 Appendix A, Page No. 2 PHOTOGRAPHS San Diego County, 1928, Photographs 30E2 and 30F2; Scale: 1 inch = 1000 feet (approximate). San Diego County, 1967, Photographs 142 and 143; Scale: 1 inch = 1000 feet (approximate). San Diego County, 1970, Flight 1, Photographs 2 and 3; Scale: 1 inch = 1000 feet (approximate). San Diego County, 1974, Flight 36, Photographs 4 and 5; Scale: 1 inch = 1000 feet (approximate). San Diego County, 1978, Flight 13B, Photographs 20 and 21; Scale: 1 inch = 1000 feet (approximate). San Diego County, 1983, Photographs 254 and 255; Scale: 1 inch = 2000 feet (approximate). San Diego County, 1989, Photograph 3-7; Scale: 1 inch = 2000 feet (approximate). United States Department of Agriculture, 1953, Photos AXN-4M, 17 and 18, Scale: 1 inch = 1700 feet (approximate). •m