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HomeMy WebLinkAboutW.O. P-1568; Proposed 5 Condominiums - Mark Goethales; 5 Condominiums La Costa Avenue; 1998-09-30September 30, 1998 BARRY AND ASSOCIATES GEOTECHNICAL ENGINEERING P.O. Box 230348 Encinitas, CA 92023-0348 (760) 753-9940 Mr. Mark J. Goethales 2614 Unicornio La Costa, California 92009-5330 Subject: PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed 5 Condominiums La Costa Avenue Carlsbad, California 92009 Dear Mr. Goethales, In response to your request, we have performed a preliminary geotechnical investigation at the subject site for the proposed 5 condominiums. The findings of the investigation, laboratory test results and recommendations for grading and foundation design are presented in this report. From a geotechnical point of view, it is our opinion that the site is suitable for the proposed project, provided the recommendations in this report are implemented during the design and construction phases. If you have any questions, please contact us at (760) 753-9940. This opportunity to be of service is appreciated. Respectfully submitted, A.R. BARRY AND A.R. Barry, P.E. Principal Engine PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed 5 Condominiums La Costa Avenue Carlsbad, California 92009 Prepared For Mr. Mark Goethales 2614 Unicornio La Costa, California 92009 September 30, 1998 W.O. P-1568 Prepared By: A.R. BARRY AND ASSOCIATES P.O. Box 230348 Encinitas, CA 92023-0348 TABLE OF CONTENTS INTRODUCTION 2 SITE CONDITIONS 2 PROPOSED DEVELOPMENT 2 SITE INVESTIGATION 2 LABORATORY TESTING 3 GEOTECHNICAL CONDITIONS 3 CONCLUSIONS AND RECOMMENDATIONS 4 A. GENERAL 4 B . GRADING 4 C . FOUNDATIONS 4 D . SLABS ON GRADE 5 E . RETAINING WALL 6 F . DRIVEWAY 6 G . DRAINAGE 7 H. FOOTING INSPECTION 7 I. PLAN REVIEW 7 LIMITATIONS 7 LOG OF TEST TRENCHES 10 APPENDICES APPENDIX A VICINITY MAP SITE PLAN (SHOWING LOCATION OF TEST TRENCHES APPENDIX B GRADING SPECIFICATIONS September 30, 1998 W.O. ttP-1568 Page 2 INTRODUCTION This report presents the results of our preliminary geotechnical investigation. The purpose of this study is to evaluate the nature and characteristics of the earth materials underlying the property and their influence on the proposed 5 condominiums. SITE CONDITIONS The property is located between the north side of La Costa Avenue and the south side of the La Costa Golf Course, and between El Camino Real and Viejo Castilla, in the City of Carlsbad, California. PROPOSED DEVELOPMENT At the time of our investigation, neither grading plans nor building plans were available, however it is our understanding that a level building pad will be graded for the construction of 5 two story condominiums. It is also our understanding that the foundation will be bearing on a level graded pad with slab on grade construction. SITE INVESTIGATION Three backhoe trenches were excavated to a maximum depth of 14 feet. Earth materials encountered were visually classified and logged by our field engineer. Bulk samples were obtained and transported to our laboratory for testing and analysis. September 30, 199 W.O. ttP-1568 Page 3 LABORATORY TESTING Classification The field classification was verified through laboratory examination in accordance with the Unified Soil Classification System. The final classification is shown on the enclosed Logs. GEOTECHNICAL CONDITIONS The site contains fill soil in varying depths to 5 feet. Most of the fill soil was properly compacted and contains clayey sand, sandy clay, and silty sand to the bottom of the excavations. Fill soil will be imported and compacted to 90% of maximum density. Expansive Soil Existing on site soils were found to range in expansion potential from low to moderate. Since imported soil will be used to bring the pads up to grade we will select a sandy non-detrimentally expansive soil. Groundwater Groundwater was not encountered in our test trenches to a depth of 14 feet. Groundwater related problems are not anticipated during of after construction. September 30, 1998 W.O. ttP-1568 Page 4 CONCLUSIONS AND RECOMMENDATIONS General The on site soils are suitable to receive the imported fill soil provided the existing soil be removed and re-compacted to a depth of 2 feet. Final depth of removal will be determined during grading. Grading General Grading will consist of the preparation of on site soil to receive the imported fill, cutting and filling the northerly facing slope in order to create a level building pad for the 5 proposed condominiums. The excavation and re-compaction should include the area 5 feet beyond the building line. See Grading Specifications, Appendix B Foundation Footings for the proposed residence and garage should be a minimum of 15 inches wide and founded a minimum of 18" below grade. A 12- inch-by-12-inch grade beam should be placed across the garage opening. Footings founded a minimum of 18" below grade may be designed for a bearing value of 1500 psf. The bearing value indicated above is for the total of dead and applied live loads. This value may be increased by 33 percent for September 30, 1998 W.O. #P-1568 Page 5 short durations of loading, including the effects of wind and seismic forces. Resistance to lateral load may be provided by friction acting at the base of foundations and passive earth pressure. A coefficient of friction of 0.3 should be used with dead-load forces. A passive earth pressure of 250 pounds per square foot, per foot of depth of fill penetrated to a maximum of 1500 pounds should be used in the design. Steel reinforcement should consist of 4-#4 bars, 2 placed 3" from the bottom of the footing and 2 placed 2" below the top of the footing. Slabs on grade If slab on grade is planned it should be a minimum of 4.0 inches thick and reinforced in both directions with No. 3 bars, placed 18 inches on center. The slab should be underlain by a minimum 4-inch sand blanket which incorporates a minimum 6.0-mil Visqueen or equivalent moisture barrier in its center, for moisture sensitive floors. Utility trenches underlying the slab should be bedded in clean sand to at least one foot above the top of the conduit, then backfilled with the on-site granular materials, compacted to a minimum of 90 percent of the laboratory maximum dry density. However, sufficiently compacting the backfill deposits may damage or break shallow utility lines. Therefore, minor settlement of the September 30, 1998 W.O. #P-1568 Page 6 backfill in the trenches is anticipated in these shallow areas. To reduce the possibility of cracks occurring, the slab should be provided with additional reinforcement to bridge the trenches. Retaining Walls Retaining walls should be designed in accordance with the following soil perimeters: Soil Type Equivalent Additional Uniform Fluid Pressure (PCF) Pressure (PSF) (Unrestrained Walls) (Restrained Walls) Native Soil 33 6xH* {Level Backfill) *H= Height of wall in feet Walls should be adequately drained to prevent build-up of hydrostatic pressures. Footings should be designed in accordance with the previous foundation recommendations. Driveway The following recommendations are submitted as preliminary guidelines for pavement construction and are based on a non- expansive soils condition in the upper 12" of subgrade. Asphalt Concrete The driveway section should consist of 2.0 inches of asphalt over 4.0 inches of Class II base. The Class II base and the upper 12 inches of the subgrade deposits should be compacted to a minimum of September 30, 1998 W.O. ttP-1568 Page 7 95 percent of the laboratory maximum dry density. The upper 12" of subgrade should consist of non-expansive soil. Paved areas should be protected from moisture migrating under pavement. Drainage All roof water should be collected and conducted to a suitable location via non-erodible devices. Roof gutters are recommended. Pad water should be directed away from foundations and around the residence to a suitable location. Pad water should not pond. Footing Inspections Structural footing excavations should be inspected by a representative of this firm prior to the placement of reinforcing steel. Plan Review A copy of the final building plans should be submitted to this office for review, prior to the initiation of construction. Additional recommendations may be necessary at that time. moderately LIMITATIONS This report is presented with the provision that it is the responsibility of the owner or the owner's representative to bring the information and recommendations given herein to the attention September 30, 1998 W.O. #P-1568 Page 8 of the project's architects and/or engineers so that they may be incorporated into the plans. If conditions encountered during construction appear to differ from those described in this report, our office should be notified so that we may consider whether or not modifications are needed. No responsibility for construction compliance with design concepts, specifications or recommendations given in this report is assumed unless on-site review is performed during the course of construction. The conclusions and recommendations of this report apply as of the current date. In time, however, changes can occur on a property whether caused by acts of man or nature on this or adjoining properties. Additionally, changes in professional standards may be brought about by legislation or the expansion of knowledge. Consequently, the conclusions and recommendations of this report may be rendered wholly or partially invalid by events beyond our control. This report is therefore subject to review and should not be relied upon after the passage of three years. The professional judgments presented herein are founded partly on our assessment of the technical data gathered, partly on our understanding of the proposed construction and partly on our general experience in the geotechnical field. September 30, 1998 W.O. #P-1568 Page 9 If you have any questions, 760.753.9940. please contact our office at The opportunity to be of service is appreciated Respectfully submitted, A. R. BARRY, A.R. Barry, P.E. Principal Engine September 30, 199 W.O. ttP-1568 Page 10 LOG OF EXPLORATORY TRENCHES TRENCH # DEPTH CLASSIFICATION TP-1 TP-2 0-2' 2' -5' 5'-14' 0-2 2-10 SM SM,SC SM,SC SM SM,SC DESCRIPTION Fill- Gray and tan clayey sand, loose, dry Fill- Gray and tan silty sand and sandy clay, mod. dense, moist. Brown to gray silty sand and sandy clay, mod.dense, moist. Bottom of excavation 14 feet, no groundwater. Fill- Dark brown silty sand dry, loose Fill- Gray and tan silty sand and sandy clay, mod. dense, moist. Bottom of excavation 10', no groundwater. TP-3 0-2 2-10 SM SM,SC Fill- Dark: brown silty sand dry, loose Fill- Gray and tan silty sand and sandy clay, mod. dense, moist. Bottom of excavation 10', no groundwater. ARRENDIX A J>tt / i i ', 7 \HM>IU7 «\\^..:,\ ^w^&ss^ 5 g$ -fc «'?lj! . Kff-LB..^5*^ LA TA SITE ' MAX, PAtP STUPV TEST TRENCH LOCATION PLAN ARRENDIX B APPENDIX B RECOMMENDED GRADING SPECIFICATIONS GRADING INTENT The intent of these specifications is to establish procedures for clearing, compacting natural ground, preparing areas to be filled and placing and compacting fill soil to the lines and grades shown on the accepted plans. The recommendations contained in the preliminary geotechnical investigation report are a part of the recommended grading specifications and would supersede the provisions contained herein in case of conflict. INSPECTION AND TESTING A geotechnical engineer should be employed to observe and test the earthwork in accordance with these specifications. It will be necessary that the geotechnical engineer or his representative make adequate observations so that he may provide a memorandum that the work was or was not accomplished as specified. Deviations from these specifications will be permitted only upon written authorization from the geotechnical engineer. It should be the responsibility of the contractor to assist the geotechnical engineer and to keep him apprised of work schedules, changes and new information and data so that he may provide the memorandum to the owner and governmental agency as required. If in the opinion of the geotechnical engineer, substandard conditions such as questionable soil, poor moisture control, inadequate compaction, adverse weather, etc. are encountered, the contractor should stop construction until the conditions are remedied. Unless otherwise specified, fill material should be compacted by the contractor while near the optimum moisture content to a density that is no less than 90 percent of the maximum dry density determined in accordance with ASTM Test No. D1557-78 or other density test methods that will yield equivalent results. CLEARING AND PREPARATION OF AREAS TO RECEIVE FILL All trees, brush, grass and other objectionable material should be collected, piled and burned or otherwise disposed of by the contractor so as to leave the areas that have been cleared with a neat and finished appearance, free from unsightly debris. APPENDIX B Page 2 All vegetable matter and objectionable material should be removed by the contractor from the surface upon which the fill is to be placed, and any loose or porous soils should be removed or compacted to the depth determined by the geotechnical engineer. The surface should then be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment to be used. When the slope of the natural ground receiving fill exceeds 20 percent (5 horizontal to 1 vertical), the original ground should be stepped or benched as shown on the attached plate. tBenches should be cut to a firm, competent soil condition. The lower bench should be at least 10 feet wide and all other benches at least 6 feet wide, ground slopes flatter than 20 percent should be benched when considered necessary by the geotechnical engineer. FILL MATERIAL Materials for compacted soil should consist of any material imported or excavated from the cut areas that in the opinion of the geotechnical engineer is suitable for use in construction fills. The material should contain no rocks or hard lumps greater than 12 inches in size and should contain at least 40 percent of material smaller than 1/4 inch in size. (Materials greater than 6 inches in size should be placed by the contractor so that they are surrounded by compacted fines; no nesting of rocks will be permitted.) No material of a perishable, spongy or otherwise improper nature should be used in filling. Material placed within 36 inches of rough grade should be select material that contains no rocks or hard lumps greater than 6 inches in size and that swells less than 3 percent when compacted (as specified later herein for compacted fill) and soaked under an axial pressure of 150 psf. Potentially expansive soils may be used in fills below a depth of 36 inches and should be compacted' at a moisture greater than the optimum moisture content for the material. PLACING, SPREADING AND COMPACTING OF FILL Approved material should be placed in areas prepared to receive fill in layers not to exceed 6 inches in compacted thickness. Each layer should have a uniform moisture content in the range that will allow the compaction effort to be efficiently applied to achieve the specified degree of compaction to a minimum specified density with adequately sized equipment, either specifically designed for soil compaction or of proven reliability. Compaction should be continuous over the entire area and the equipment should make APPENDIX B Page 3 sufficient trips to ensure that the desired density has been obtained throughout the fill. When moisture content of the fill material is below that specified by the geotechnical engineer, water should be added by the contractor until the moisture content is as specified. When the moisture content of the fill material is above that specified by the geotechnical engineer, the fill material should be aerated by the contractor by blading, mixing or other satisfactory methods until the moisture content is as specified. The surface of fill slopes should be compacted and there should be no excess loose soil on the slopes. UNIFIED SOIL CLASSIFICATION Identifying Criteria Group Symbol Soil Description COARSE-GRAINED (more than 50 percent larger than #200 sieve) Gravel {more than 50 percent larger than #4 sieve but smaller than three inches) Non-plastic GW GP Sands (more than 50 percent smaller than #4 sieve) GM GC SW SP Gravel, well-graded gravel-sand mixture, little or no fines Gravel, poorly grad- ed gravel-sand mix- ture, little or no fines Gravel, silty, poor- ly graded, gravel- sand-silt mixtures Gravel, clayey, poorly graded, grav- el-sand-clay mixture Sand, well-graded, gravelly sands, little or no fines Sand, poorly graded, gravelly sands, little or no fines APPENDIX B Page 4 SM Sand, silty, poorly graded, sand-clay mixtures FINE-GRAINED (more than 50 percent but smaller than #200 sieve) Liquid limit less than 50 ML CL Liquid limit greater than 50 OL MH CH OH Silt, inorganic silt and fine sand, sandy silt or clayey-silt- sand mixtures with slight plasticity Clay, inorganic clay of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Silt, inorganic, silts and organic silt-clays of low plasticity Silt, inorganic, silts micaceous or diatomaceous fine, sandy or silty soils elastic silts Clay, inorganic, clays of medium to high plasticity, fat clays Clay, organic, clays of medium to high plasticity HIGHLY ORGANIC SOILS PT Peat, other highly organic swamp soils APPENDIX B Page 5 INSPECTION Observation and compaction tests will be made by the geotechnical engineer during the filling and compacting operations so that he can state whether the fill was constructed in accordance with the specifications. The geotechnical engineer will make field density tests in accordance with ASTM Test No. D1557-78. Density tests will be made in the compacted materials below the surface where the surface is disturbed. When these tests indicated that the density of any layer of fill or portion thereof is below the specified density, that particular layer or portion should be reworked until the specified density has been obtained. The location and frequency of the tests well be at the soil engineer's discretion. In general, the density tests will be made at an interval not exceeding 2 feet in vertical rise and/or 500 cubic yards of embankment. PROTECTION OF WORK During construction, the contractor should properly grade all excavated surfaces to provide positive drainage and prevent ponding of water. He should control surface water to avoid damage to adjoining properties or to finished work on the site. The contractor should take remedial measures to prevent erosion of freshly graded areas and until such time as permanent drainage and erosion control features have been installed.