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HomeMy WebLinkAboutMS 06-01; MCCARTHY RESIDENCE; PRELIMINARY SOILS INVESTIGATION FOR PROPOSED TWIN HOMES; 2004-09-08.0.t NORTh COUNTY COMPACTION ENGINEERING, INC. RECE7iI PRELIMINARY SOILS INVESTIGATION FOR PROPOSED TWIN HOMES 5115 CARLSBAD BOULEVARD CARLSBAD, CALIFORNIA CAROLINE DOOLEY 2979 STATE STREET SUITE A CARLSBAD, CA 92008 SEPTEMBER 8, 2004 PROJECT NO. CE-7275 M) ob-ol NORTH COUNTY COMPACTION ENGINEERING, INC. TABLE OF CONTENTS Page 1.) Purpose and Scope 1 2.) Location and Description of Site I 3.) Field Investigation 1 4.) Soil Conditions 2 5.) Laboratory Soil Testing 2 6.) Recommendations and Conclusions 3 A.) Grading 3 • B.) Foundations 4 • C.) Slopes 5 Retaining Walls 5 • Estimated Paving Sections 6 •: F.) Seismic Design Considerations 7 • G.) Review of Grading Plan 7 7.) Uncertainty and Limitations 7 APPENDIX Appendix A: Exploration Legend & Unified Soil Classification Chart Plate No. One Test Pit Location Plan Plate No. Two & Three Exploration Logs Plate No. Four Tabulation of Test Results Appendix B: Recommended Grading Specifications NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Caroline Dooley 2979 State St. Ste. A Carlsbad, CA 92008 SUBJECT: Preliminary Soils Investigation Proposed Twin Homes 5115 Carlsbad Boulevard Carlsbad, California Dear Ms. Dooley: In response to your request, we have performed a Preliminary Soils Investigation for the subject - project. The purpose of our investigation was to evaluate the suitability of the site for the proposed development and make recommendations with regard to site grading and foundation design. Briefly, our investigation revealed favorable soil conditions and in our opinion, the site is suitable for the proposed development, provided recommendations set forth in the attached report are adhered to. If you have any questions, please do not hesitate to contact us. This opportunity to be of service is sincerely appreciated. Respectfully submitted, North County COMPACTION ENGINEERING, INC. Ronald K. Adams President \, 1 GE 713 fI IJ ( rn c Ep 9/30/05 I Dale R. Regli OF Registered Civil E Geotechnical Engineer 000713 RKA:paj cc: (4) submitted P. 0. BOX 302002 * ESCONDIDO, CA 92030 * (760) 480-1116 FAX (760) 741-6568 1 ! NORTH COUNTY COMPAC11ON INC. Project No. CE-7275 ENGINEERING Page 1 September 8, 2004 1. PURPOSE AND SCOPE The purpose of the investigation was to determine if the site is suitable for the proposed twin homes. The scope of the investigation was to: Determine the physical properties and engineering characteristics of the surface and subsurface soils. Provide design information with regard to grading, site preparation, and foundation design of the proposed structure(s). 2. LOCATION AND DESCRIPTION OF SITE The site is located at 5115 Carlsbad Boulevard in the City of Carlsbad, California. The 75 X 80 foot rectangular shaped lot is bordered by single family dwellings to the north, south and west and Carlsbad Boulevard to the east. Site topography consists of a predominantly flat lot pitched downhill to the west. The site is presently occupied by single story duplex units. The duplex is generally landscaped with walkways, driveways, fences, lawns, shrubs, small trees, etc. 3. FIELD INVESTIGATION The field investigation was performed on August 24, 2004 and included an inspection of the site and excavation of one exploratory boring to depth of 15 feet, utilizing a truck mounted, 8 inch diameter continuous flight auger. Due to limited access at the rear yard area of the property, a hand dug test pit to a depth of 2 feet was also excavated. The location of the test pit and drill boring is delineated on attached Plate No. One entitled "Test Pit Location Plan." As excavation proceeded, the drill boring and test pit excavations were logged and both disturbed and undisturbed soil samples were collected at different depths and returned to our laboratory for testing. NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page 3 6. RECOMMENDATIONS AND CONCLUSIONS• General It is our understanding, the proposed twin homes will consist of wood frame construction utilizing slab on grade foundations. In our opinion, the site is suitable for the proposed twin homes. Recommendations presented in this report should be incorporated into the planning, design and construction phases of the subject project. 6A. Grading General Grading at the site will be performed to remove and recompact compressible top soils (old fill/plowed ground) and to construct a level building pad to accommodate the proposed twin home. All grading should be performed in accordance with the City of Carlsbad Grading Ordinance and the Recommendations/Specifications presented in this report. Subsequent to site demolition, loose surficial soils (plowed ground/old fill), as indicated on the attached Plate No's Two and Three, should be undercut or removed to firm native ground and recompacted in accordance with the attached Appendix 'B' entitled "Recommended Grading Specification". Firm native ground may be determined as undisturbed soil having an insitu density of greater than ninety percent (90%) of maximum dry density. We should be contacted to document firm native ground is exposed and properly prepared prior to filling. The removal area should extend under and a minimum of 5 feet beyond (where applicable) the footprint of the proposed structure and/or surface improvements. Prior to constructing fill slopes, shear keys should be excavated a minimum of 2 feet into firm native ground, inclined back into slope, and have a minimum width of 15 feet. We should be contacted to document keyways were properly constructed prior to placing fill. All fill soils generated from earthwork construction should be placed in conformance with the attached Appendix 'B' entitled, "Recommended Grading Specifications". NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page 2 Undisturbed samples were obtained by driving a 3 inch outside diameter California Split Spoon Sampler into undisturbed soil, utilizing 140 pound hammer, free falling a distance of 30 inches. Type of soils samples collected, natural densities, moisture content, blow counts and sample penetration are presented on the attached Plate No.'s Two and Three entitled "Exploration Logs". SOIL CONDITIONS Loose surficial soils (silty-sands) consisting of old fill and/or plowed ground were found to be 2 feet and 172 feet in depth in Drill Boring No. One and Test Pit No. One, respectively. Underlying native soils to depths explored were dense silty-sandstones of the Coastal Terrace Deposit. On-site soils were found to have an expansion index of less than 5 and are classified as being "very low" in expansion potential. Groundwater was not encountered at the time of our investigation, nor did caving of exploratory trenches occur. In addition, due to the dense nature of the underlying sandstone formation at the site, it is our opinion, soil liquefaction is unlikely to occur in the event grading is performed in accordance with the recommendations set forth in this report. LABORATORY SOIL TESTING All laboratory test were performed on typical soils in accordance with accepted test methods of the American Society for Testing and Materials (ASTM). Tests conducted include: Optimum Moisture & Maximum Density (ASTM D- 1557) Direct Shear (Remold) (ASTM D-3080) Q. Sieve Analysis (ASTM D-1 140) Field Density & Moisture (ASTM D-1 556) Expansion Potential (FHA Standard) Test results are tabulated on the attached Plate No.'s Two through Four entitled "Exploration Log" and "Tabulation of Test Results". NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page 4 If required, soils to be imported should be non-expansive (less than 2% swell) and granular by nature, having strength parameters equal to or greater than the prevailing on-site soils. We should be contacted to inspect an/or test imported soils prior to hauling then on-site to assure they will be suitable for the proposed construction. Particles of asphalt and concrete debris, having a diameter of greater than 6 inches, will not be suitable fill material and should be separated from fines during grading and hauled off-site. If encountered, leach lines and/or pipes should be removed. Concrete pipes may be crushed in place. Trench lines should be recompacted in accordance with Appendix 'B'. It is highly probable the proposed structure will be traversed by a transition from native ground to fill. Therefore, to reduce structural damage occurring from foundations bearing on two different soil types, the following measure should be employed: The native ground side of the transitional areas should be removed to a depth of 1 foot below the bottom of the deepest proposed footing and brought back to grade with properly compacted fill. This will allow the proposed structure to bear entirely on a compacted fill mat, thus reducing the probability of differential settlement. The removal area should extend under and a minimum of 5 feet beyond the proposed structure. 6B. Foundations General On-site soils are comprised of non-expansive sandy soils with above average strength parameters. Therefore, conventional foundation may be utilized provided the aforementioned grading recommendation are adhered to. For One-Story Construction: Continuous footing having a minimum width of 12 inches and founded a minimum depth of 12 inches below lowest adjacent grade will have an allowable soil bearing pressure of 2000 pounds per square foot. For Two-Story Construction: Continuous footings should have a minimum width of 15 inches and be founded a minimum depth of 18 inches below lowest adjacent grade. COMPACTION NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page Isolated square footings having a diameter of 18 inches and founded a minimum depth of 18 inches below lowest adjacent grade will have an allowable soil bearing pressure of 2000 pounds per square foot. All continuous footings are to be reinforced with one #5 bar top and bottom. Steel should be positioned 3 inches above bottom of footing and 3 inches below top of footing. Interior slabs should be a minimum of 4 inches thick and reinforced with #3 bars on 18 inch centers, both ways at mid-point of thickness. Slab underlayment should consist of 4 inches of washed concrete sand with a visqueen moisture • barrier installed at mid-point of sand (2 inches sand, visqueen, 2 inches sand). Sand should be tested in accordance with ASTM D-2419 to insure a minimum sand equivalent of 30. Foundation set-backs from top of slopes should be a minimum of 8 feet. If this cannot be achieved, footings near or on adjacent slopes should be founded at a depth such that the horizontal distance from the bottom outside edge of footing to the face of the slope is a minimum of 8 feet. Prior to pouring of concrete, North County COMPACTION ENGINEERING, INC. should be contacted to inspect foundation recommendations for compliance to those set forth. 6C. Slopes Cut and compacted fill slopes constructed to maximum heights of 10 feet with maximum slope ratios of 2:1 (horizontal to vertical units) will be stable with relation to deep seated failure, provided they are properly maintained. During grading, positive drainage away from top of slopes should be provided. Subsequent to completion of grading, slopes should be planted as soon as possible with light groundcover indigenous to the area. Our analysis was performed utilizing Taylor's Charts for cut and compacted fill slopes and a safety factor of 1.5. 61). Retaining Walls For static conditions, the prevailing soils will have an allowable equivalent passive fluid pressure of 365 psf, increasing 365 psf per foot in depth. Allowable pressures assume walls are backfilled with a non-expansive sand a distance behind the wall equivalent to two-thirds the retained height. NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page 6 Allowable active pressures may be assumed to be equivalent to the pressure of a fluid weighing 37 pcf for unrestrained walls. These values assume a vertical, smooth wall, and a level, drained backfill. Should these conditions not be met, we should be contacted for new values. Allowable active pressures for restrained walls may be assumed to be equivalent to the pressure of a fluid weighing 37 pcf, plus an additional uniform lateral pressure of 8H. H=height of retained soils above top of wall footing in vertical feet. Allowable active pressures for retaining walls with 2:1 inclinations of sloping surcharge may be assumed to be equivalent to a pressure of fluid weighing 53 pcf. The coefficient of friction of concrete to soil may be assumed to be .40 for resistance to horizontal movement. All walls should be provided with drains behind and at the base of the wall. To provide a well drained condition, Miradrain 6000 and/or its equivalent is recommended. Drains should be constructed in accordance with the manufacturers specifications. Back of walls should be water- proofed (when applicable) per the project structural engineers recommendations. 6E. Estimated Paving Section Structural section for asphaltic paving for the proposed driveways and parking area are based on an estimated R-Value of 45. The following section is provided for bid purposes only. Actual sections should be determined subsequent to completion of grading operations. Assumed Traffic Index = 4.5 (Light Vehicular Traffic) 2Y2 inches of asphaltic paving on 4 inches of select base coarse on 6 inches of recompacted native subgrade. All materials and construction for asphaltic paving and base should conform to the Standard Specifications of the State of California Business and Transportation Agency, Department of Transportation, Sections 39 and 26, respectively. Class II base material should have a minimum R-Value of 78 and a sand equivalent of 30. All materials should be compacted to a minimum of ninety-five percent (95%). NORTH COUNTY COMPACTION ENGINEERING, INC. Project No. CE-7275 September 8, 2004 Page 7 Rigid Concrete Paving: 4 inches of concrete reinforced with #3 bars on 18 inch center, both ways, on 12 inches of recompacted native subgrade soil compacted to a minimum of 95%. NOTE: All concrete should have a minimum compressive strength of 3250 psi. 6F. Seismic Design Considerations (Soil Parameters) Soil Profile = SD (Table 16-i of the 1997 Uniform Building Code) Type 'B' Fault (Rose Canyon) Distance =6 km (California Department of Conservation, Division of Mines and Geology [maps], in conjunction with Tables 16-S and 16-T of the 1997 Uniform Building Code) 6G. Review of Grading Plan Approved site and grading plans were not available at the time of our investigation. Therefore, upon their completion, we should review them to assure compliance with the recommendations presented in this report. 7. UNCERTAINTY AND LIMITATIONS Surface and subsurface soils are assumed to be uniform. Therefore, should soils encountered during construction differ from those presented in this report, we should be contacted to provide their engineering properties. It is the responsibility of the owner and contractor to carry out recommendations set forth in this report. During our investigation of the subject site, evidence of faulting was not encountered. Subsequent to review of available geologic literature, we feel any faulting in the vicinity of the site may be classified as inactive. However, it should be noted that San Diego County is located in a high seismic area with regard to earthquake. Earthquake proof projects are economically unfeasible. Therefore, damage as a result of earthquake is probable and we assume no liability. NORTH COMPACTION INC. Project No. CE-7275 ENGINEERING, September 8, 2004 Page 8 We assume the on-site safety of our personnel only. We cannot assume liability of personnel other than our own. It is the responsibility of the owner and contractor to insure construction operations are conducted in a safe manner and in conformance with regulations governed by CAL-OSHA and/or local agencies. Should you have any questions, please do not hesitate to contact us. This opportunity to be of service is sincerely appreciated. Respectfully submitted, North County COMPACTION ENGINEERING, INC. Ronald K. Adams President RKA:paj cc: (4) submitted I ;f(\oF ES S/3 CIO GE 713 'rn FIn. 9/30/05 4" 11 'FC Dale R. Regli Registered Civil En f q Geotechnical Engineer NORTH COUNTY COMPACTION ENGINEERING, INC. EXPLORATION LEGEND UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION COARSE GRAINED: More than half of material is larger than No. 200 sieve size. GRAVELS CLEAN GRAVELS More than half of coarse fraction is larger than No. 4 sieve size, but smaller than 3". GRAVELS WITH FINES (Appreciable amount of fines) SANDS CLEAN SANDS More than half of coarse fraction is smaller than No. 4 sieve size. 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 less than 50 SILTS AND CLAYS Liquid Limit greater than 50 HIGHLY ORGANIC SOILS GROUP SYMBOL TYPICAL NAMES OW Well graded gravels, gravel-sand mixtures, little or no fines. OP Poorly graded gravels, gravel sand mixtures, little or no fines. GM Silty gravels, poorly graded gravel- sand-silt mixtures. GC Clayey gravels, poorly graded gravel-sand, clay mixtures. SW Well graded sand, gravely sands, little or no fines. SP Poorly graded sands, gravely sands, little or no fines. SM Silty sands, poorly graded sand and silt mixtures. SC Clayey sands, poorly graded sand and clay mixtures. ML Inorganic silts and very fine sands, rock flour, sandy silt or clayey- silt-sand mixtures with slight plasticity. CL Inorganic clays of low to medium • plasticity, gravely clays, lean clays. OL Organic silts and organic silty clays of low plasticity. MH Inorganic silts, micaceous or • diatomaceous find sandy or silty soils, elastic silts. CH Inorganic clays of high plasticity, fat clays. OH Organic clays of medium to high plasticity. PT Peat and other highly organic soils. US - Undisturbed, driven ring sample or tube sample CK - Undisturbed chunk sample BG - Bulk sample . Water level at time of excavation or as indicated APPENDIX 'A' Proposed Twin Homes Carlsbad Boulevard Carlsbad, California Approx. Scale 151 - PAVrMrIJT NORTH COUNTY COMPACTION ENGINEERING, INC. SOIL TESTING & INSPECTION SERVICES TEST PIT LOCATION PLAN PROJECT NO. CE- 7275 PLATE NO. ONE NORTH COUNTY COMPACTION ENGINEERING, INC. EXPLORATION LOG PROJECT NAME: Carlsbad Blvd, Carlsbad DATE LOGGED: 08/24/04 ELEVATION: Existing Grade BORING NO.ONE Depth Sample Dry Moisture Passing Sample Soil Description & Remarks (Feet) Type Density Content #200 Depth Classif- ______ (pcf) (%) Sieve ication SM Brown Red, Dry, Loose Silty-Sand BG 21.9 it (Plowed Ground / Old Fill) (Remove and Recompact) ------- ---------- --------- - SM Brown Red, Humid, Dense, Silty-Sand U 118.1 5.8 3' (Firm Native Coastal Terrace) (Blow Count at 3 Feet .16 for 12 Inches) 4- 5- U 116.1 5.9 5' (Blow Count at 5 Feet = 23 for 12 inches) 6- 7- 8- 9- 10- U 118.7 4.8 11.8 10' SM Yellow Brown, Humid, Very Dense, Silty-Sandstone (Coastal Terrace) (Blow Count at 10 Feet = 36 for 11 Inches) PROJECT NO. CE-7275 PLATE NO. TWO NORTH COUNTY COMPACTION ENGINEERING, INC. EXPLORATION LOG PROJECT NAME: Carlsbad Blvd.Carlsbad DATE LOGGED: 08/24/04 ELEVATION: Existing Grade BORING NO. ONE cont'd Depth Sample Dry Moisture Passing Sample Soil Description & Remarks (Feet) Type Density Content #200 Depth Classif- ______ (pet) (%) Sieve ication SM Yellow Brown, Humid, Very Dense 11- Silty-Sandstone (Coastal Terrace) 12- 13- 14- 15- --U---. _____ ____ ____ _____ Bottom of Drill Boring 16- PROJECT NO. CE-7275 PLATE NO. TWO(cont'd) NORTH COUNTY COMPACTION ENGINEERING, INC. TABULATION OF TEST RESULTS OPTIMUM MOISTURE/MAXIMUM DENSITY SOIL DESCRIPTION TYPE MAX. DRY DENSITY OPT. MOISTURE (LB. CU. FT) (% DRY WT Brown Silty-Sand BI @ 1' 130.0 08.2 Brown Silty-Sand P1 @ 0-1' 123.5 : 09.4 EXPANSION POTENTIAL SAMPLE NO. B1@1' P1(0-1' CONDITION Remold 90% Remold 90% INITIAL MOISTURE (%) 7.9 9.4 AIR DRY MOISTURE (%) 1.0 1.8 FINAL MOISTURE (%) 12.6 16.8 DRY DENSITY (PCF) 117.0 111.2 LOAD (PSF) 150 150 SWELL (%) .000 .000 EXPANSION INDEX Less than 5 Less than 5 DIRECT SHEAR SAMPLE NO. BI @ 1' P1 @ 0-1, CONDITION Remold 90% Remold 90% ANGLE INTERNAL FRICTION 31 33 COHESION INTERCEPT (PCF) 125 100 PROJECT NO. CE-7275 PLATE NO. FOUR NORTH COUNTY COMPACTION ENGINEERING, INC. EXPLORATION LOG PROJECT NAME: Carlsbad Blvd. Carlsbad DATE LOGGED: 08/24/04 ELEVATION: Existing Grade TEST PIT NO.ONE Depth Sample Dry Moisture Passing Sample Soil Description & Remarks (Feet) Type Density Content #200 Depth Classif- ______ (pcf) (%) Sieve ication BO 24.1 0 -11 SM Brown, Dry, Loose, Silty-Sand (Plowed Ground / Fill) - (Remove and Recompact) SM Brown Red, Dry, Dense, Silty-Sand (Firm Native / Coastal Terrace) 2- ------ ____ --------- .-----• ------ ---___ .--- Bottom of Test Pit 3- PROJECT NO. CE-7275 PLATE NO.THREE - NORTH COUNTY COMPACTION ENGINEERING, INC. PLACING AND SPREADING OF FILL The selected fill material shall be placed in layers which when compacted will not exceed 6 inches in thickness. Each layer shall be spread evenly and shall be thoroughly blade mixed during the spreading to insure uniformity of material in each layer. When moisture content of the fill material is below that recommended by the Soils Engineer, water shall then be added until the moisture content is as specified to assure thorough bonding during the compacting process. When the moisture content of the fill materials is above that recommended by the Soils Engineer, the fill material shall be aerated by blading or other satisfactory methods until the moisture content is as specified. COMPACTION After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to not less than ninety percent (90%) relative compaction. Compaction shall be by sheepsfoot rollers multiple-wheel pneumatic tired rollers or other types of rollers. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolling each layer shall be continuous over it's entire area and the roller shall make sufficient trips to insure that the desired density has been obtained. The fill operation shall be continued in 6 inch compacted layers, or as specified above, until the fill has been brought to the finished slopes and grades shown on the project plans. WALL BACKFILL Backfill soils should consist of non-expansive sand, Compaction should be achieved with light hand-held pneumatic tampers to avoid over compaction and hence cause structural damage. Wall backfill should be compacted to a minimum of ninety percent (90%) of maximum density. TRENCH BACKFILL All trench backfill located within structural areas should be compacted to a minimum of ninety percent (90%) of maximum density. APPENDIX 'B'