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HomeMy WebLinkAboutMS 04-05; LBC CONDOMINIUM PROJECT; UPDATE GEOTECHNICAL REPORT AND REMEDIAL GRADING GROUND STABILIZATION RECOMMENDATIONS; 2006-09-25PI\TrTNP PR 2450 Vineyard Avenue Escondido, California 92029-1229 Job #03-348-P September 25, 2006 Zijlstra Architecture Attention: Mr. Sjirk Zijlstra 731 South Highway 101 Suite I L Solana Beach, California 92075 Phone (760) 7434214 Fax (760) 739-0343 UPDATE GEOTECHNICAL REPORT AND REMEDIAL GRADING GROUND STABILIZATION RECOMMENDATIONS, LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD, CALIFORNIA I. INTRODUCTION The project site was the subject of a previous geotechnical study performed by this office entitled "Preliminary Geotechnical investigation, Lot 31, Tract 5162, Cove Drive, Carlsbad, California," Job #03-348-P, dated March 3, 2004. Subsequent repàrts and letters consisted of "Addendum Geotechnical Report, Lot 31, Tract 5162, Cove Drive, Carlsbad, California," dated November 19, 2003, and "FoUndation Plan Review, Proposed Three- Story Twin Homes, Lot 31, Tract 5162, Cove Drive, California," dated July 14, 2006. The referenced reports and letters are enclosed with this report as Appendices A through C, respectively. Based on our previous study, liquefaction of the underlying loose and saturated fills and lagoonal deposité is the most significant geotechnical concern at the site. Consequently, driven pile and grade beam foundation supports were initially recommended and considered. We now understénd that remedial grading and ground stabilization earthworks mitigation techniques as generally presented in the referenced Addendum Geotechnical Report (Appendix B), is being reconsidered. The purpose of this work was to review the referenced reports and provide detailed reóommendations that are consistent with remedial grading ground stabilization earthworks mitigation techniques. All conclusions and recommendations provided in the referenced reports and subsequent transmittals (Appendices A through C) remain valid and should be considered in final designs and implemented during the construction phase except where specifically superseded or amended below: Mr. Sjirk Zijlstra September 25, 2006 Page 2 II. REMEDIAL GRADING AND GROUND STABILIZATION Planned construction areas are underlain by loose to soft and saturated fills and alluvial soils which can undergo settlements and experience liquefaction and soil softening in their present conditions. Special ground stabilization and remedial grading techniques will be required in order to construct safe and stable building and pad surfaces as specified below. All grading and earthworks should be completed in accordance with Appendix Chapter 33 of the California Building Code, City of Carlsbad Grading. Ordinances, the Standard Specifications for Public Works Construction, and the requirements of the following sections: . Clearing and Grubbing: Remove trees, trash, debris, surface vegetation and other unsuitable/deleterious materials from all areas of planned new structures and improvements plus 5 feet minimum outside the perimeter where possible, and as directed in the field. Any construction debris generated from the demolition of existing site structures and improvements should also be properly removed and disposed of from the site. Vegetation, construction debris, grasses, lawns, trees, roots, stumps and other deleterious or unsuitable materials should be thoroughly removed and cleared from the construction site to the satisfaction of the project geotechnical consultant. All existing abandoned underground tanks, struôtures, pipes and irrigation lines should be properly removed from the construction areas. Existing underground utilities/plumbing in the construction areas should be pot-holed, identified and marked prior to the actual work. Abandoned pipes and irrigation lines should be properly capped and sealed:off to prevent any future water infiltrations into the foundation bearing and subgrade soils. Voids created by the removals of the abandoned underground utilities, pipes and structures should be properly backfilled with compacted fills in accordance with the requirements of this report. The prepared ground should be inspected and approved by the project geotechnical engineer or his designated representative. bewaterin: Groundwater was encountered at the project site at the depth of approximately 5 to 7 feet below the existing ground surfaces. Dewátering efforts should be anticipéted to complete remedial grading and earthwOrk operations at the site depending on the actual watertable conditions at the time of grading. • In the event of rise in watertable conditions due to seasonal and tidal conditions, some pre-dewatering . may also be considered appropriate for this project. Any dewatering technique suitable to the field conditions which can effectively remove the intruding water and allow soil removals and fill placement is considered acceptable provided it is approved by the project engineer. Dewatenng should continue until completion of remedial grading operations and should be VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 7434214 Mr. SjirkZijlstra September 25, 2006 Page 3 discontinued only upon approval of the project geotechnical engineer. Groundwater should be lowered a minimum of 2 feet below the specified bottom of over-excavation, toe of temporary slope or trench excavations unless otherwise directed in the field. Dewatering should not be allowed to adversely impact the nearby structures and improvements. The project àontractor may wish to install instrumentations on sensitive nearby structures and improvements to monitor possible settlements and potential impacts of dewatering so necessary field adjustments can be made. Completing grading during dry seasons of the year and low tidal conditions, should be considered to minimize difficulties associated with dewatering operations. 3. Setbacks, Shoring and Temporary Construction Slopes: Excavations and removals adjacent to the existing structures and 'improvements should be done under inspection of the project geotechnical engineer. Undermining existing improvements and structures by the removal operations shall not be allowed, lop of temporary construction slopes should be adequately set back from the existing structures and improvements as directed in the field. Construction slopes required during trenching and removal operations should not exceed 1:1 gradients maximum with the watertable lowered a minimum 2 feet below the bottom of excavation. The remaining wedge of soil should then be benched out and new backfill tightly keyed-in as the fill placement progresses. Vertical trenches greater than 3 feet high maximum require continuous shoring. Temporary shoring excavation support should also be anticipated as it is required in the field by the project geotechnical consultant, or where adjacent and nearby structures and improvements prohibits laid back construction slopes. Any shoring system which can effectively allow for àonStruction and provide safe and stable site conditions may be considered. Shoring should be provided as detailed on the approved Shoring Plans prepared by the project design/bUild contractor, based on the soils parameters provided herein. All temporary, construction slopes require continuous geotechnical inspections during the remedial, grading operations. Additional recommendations including revised slope gradients, set backs and the need 'for temporary shoring support should be given at that time as necessary. The project contractor shall also obtain appropriate permits, as needed, and conform to the Cal-OSHA and local governing agencies' requirements for trenching/open excavations and safety of the workmen during 'construction. VINJE & MIDDLETON ENG!NEERING, INC. • 2450 Vineyard Avenue 0 Escondido, California 92029-1229 • Phone (760) 7434214 Mr. SjirkZijlstra September 25, 2006 Page 4 Removals and Over-excavations: The building envelope plus a minimum of 5 feet where possible, and as directed in the field, should be over-excavated to a minimum depth of 5 feet below the existing ground levels and recompacted. Based on our subsurface exploratory excavations, the groundwater levels at the project areas are approximately 5 to 7 feet below the existing ground surfaces at the time of our field investigation and removal depths, may predominantly be near or above the indicated watertable levels. Building envelope includes all exterior pad footings, pop-outs, canopy supports, etc. Due to very loose to soft soils conditions in the project areas, appropriate construction equipment (such as an excavator) should be considered for soil removals. In the paving and improvement areas plus 3 feet outside the perimeter, removal depths should extend a minimum of 3 feet below the existing grades or 1-foot below the deepest utility, whichever is more, and recompacted. Deeper removals may be necessary based on the actual field exposures and should be anticipated. Actual depths should be established by the project geotechnical engineer at the time of remedial grading operations. The exposed bottom of over-excavation should be additionally prepared as directed in the field. All grounds steeper than 5:1 receiving fills/backfihls Should be properly benched and keyed as directed in the field. Stabilization Rock Blanket: The soft bottom of over-excavations in the building envelope plus a minimum of 5 feet, should be stabilized by placing minus 12-inch combined gradation rocks and tracking/consolidating with heavy construction equipments. Rock placement should continue until full rock interlocking conditions and non-yielding bottom of over-excavation is achieved as approved in the field by the project geotechnical engineer. Based on our experience with similar projects, rocks are typically pushed with heavy equipments approximately 2-3 feet into the soft soils before suitable bottom conditions are achieved. However, only actual site conditions will determine the quantity of rocks required to achieve non-yielding conditions. As a minimum and if groundwater conditions are favorable at the time of grading, dewatering sump pump(s) should be installed at low point(s) in the excavation as necessary, and become operational at the time of initial rock placement and remain in operations until completion of the bottom stabilization works is completed as directed in the field by the project geotechnical consultant. In the case of a rise in groundwater due to tidal and seasonal conditions, more ambitious dewatering methods will be necessary as specified. VINJE & MIDDLETON ENGINEERING, INC. a 2450 Vineyard Avenue 0 Escondido, California 920294229 • Phone (760) 743-1214 Mr. Sjirk Zijistra September 25, 2006 Page Minus 1%- inch rocks (combined gradation ranging from 1% inches to 4-inch is also acceptable) should then be placed and tracked-in with heavy construction equipments over the minus 12-inch rocks to a minimum thickness of 6 inches unless otherwise directed in the field. A layer of Mirafi 500X soil separation fabric should then be laid over the approved bottom and covered with initial fill lifts of better quality on-site or sandy import soils which are properly moisture conditioned, carefully placed in thin (8 inches) horizontal layers, and compacted as directed in the field. In the paving and improvement areas, stabilization rock blanket is not required and earth reinforcement geogrid should be considered to create stable bottom of over- excavations suitable to receiving new fills and backfills. 6. Earth Reinforcement, Shrinkage, Fill Materials and Compaction: Upon approval of the project geotechnical engineer, a layer of Tensar Geogrid BX-1 200 (orgreaterfrom the same series) should be neatly placed within the compacted fills approximately 2 feet above the Mirafi 500X soil separation fabric (at least 3 feet below the top of pad or 6 inches below the invert of utility lines, whichever is more). Subsequent fill lifts should then be carefully placed over the Geogrid and compacted until final grade elevations are achieved. Considerations should also be given to raise the building pad above the existing ground levels, as required, to accommodate the specified ground stabilization and bearing soils construction. All site fills and backfills should be adequately processed, thoroughly mixed, moisture conditioned to slightly above (2%) optimum moisture levels as directed in the field, placed in thin (8 inches maximum) uniform horizontal lifts and mechanically compacted to a minimum 95% of the corresponding laboratory maximum dry density, per ASTM D-1 557, unless otherwise specified. On-site soils will shrink approximately 15% to 25% on volume basis when compacted to minimum 95% levels. Additional import soils, if required to complete remedial grading and achieve final design grades, should be good quality, non- corrosive, very low expansive granular sandy (SM/SW) deposits (100% passing %- inch sieve, more than 50% passing #4 sieve and less than 20% passing #200 sieve with expansion index less than 21), tested and approved by the project soils engineer prior to delivery to the site. Unexpected conditions may result in revised stabilization procedures including added rocks, fabrics and geogrid as established in the field. Field conditions will control actual stabilization procedures. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Ways Escondido, California 92029-1229 0 Phone (760) 743-1214 Mr. SjirkZijlstra September 25, 2006 Page 6 Geotechnical Instrumentations and Monitoring: Geotechnical instrumentation devices consisting of two settlement plates and two settlement monuments should be installed at the project building site. The settlement plates should be placed at the bottom of the over-excavations to monitor settlement of the surcharged alluvium. The settlement monuments should be installed near the rough finish pad grades to monitor the post grading characteristics of the compacted fill mass. Geotechnical instrumentation sites should be installed at selected locations, not to interfere with the grading and post grading construction phases. Monitoring should be performed by means of field surveying shots periodically taken at each settlement plate installation site as the backfill placement progresses approximately once every 2 days. At the completion, of remedial grading, monitoring should continue for both settlement plates and settlement monument sites on a bi-weekly and monthly basis as directed, until construction is completed. Surveying shots should be reduced (plotted versus time in days) by the project soils engineer, to establish settlement patterns and soil compression characteristics with respect to surcharge loading, dewatering, compaction and earthworks activities, and self weight. Actual locations and construction details for the proposed settlement plates and settlement monuments should be given by the project geotechnical engineer at the time of initial field inspections prior to actual backfill and fill placement operations. Foundation trenching can only begin after completion (less than 0.01-foot or 0.12 inches between at least three consecutive readings per monitoring schedule) of primary soil compression and the approval by the project geotechnical consultant. Foundation and slab recommendations provided in the following sections should also be confirmed and/or revised based upon the settlement monitoring data compiled at the completion of remedial grading operations. Drainage and Erosion Control: A critical element to the continued stability of the graded building pads is adequate surface drainage and storm water control. This can most effectively be achieved by installation of appropriate drainage control systems per the project drainage improvement plans. Building pad surface run-off should be collected in approved drainage facilities and directed to selected locations in a controlled manner. Area drains should be installed. Surface and flood waters should not be allowed to impact site fills, structures and improvements, or penetrate into the underlying bearing soils. Storm water and surface run-off shall be diverted from entering the site. Temporary erosion control facilities and silt fences should be installed during the construction phase periods and until landscaping is fully established as indicated and specified on the approved project grading/erosion plans. VINJE & MIDDLETON ENGINEERING, INC. ' 2450 Vineyard Avenue ' Escondido, California 920294229 • Phone (760) 743-1214 Mr. Sjirk Zijlstra September 25, 2006 Page 9. Engineering Inspections: All grading and earthwork operations including removals, suitability of earth deposits used as compacted fill and compaction procedures, should be continuously inspected and tested by the project geotechnical consultant and presented in the final as-graded compaction report. The, nature of finished subgrade soils shoUld also, be confirmed in the final compaction report at the completion of grading. Geotechnical engineering inspections shall include, but not limited to the following: * Bottom of over-excavation inspection - After the bottom of over-excavation is exposed and prepared to receive stabilization rock blanket or geogrid, but before stabilization rock blanket or geogrid is installed. * Excavation inspection - After the excavation is started, but before the vertical depth of excavation is more than 3 feet. This includes all temporary excavations, backcuts and underground trenching. Safety requirements enforôed by the governing agencies for open excavations apply. Fill/backfill inspection - After the fill/backfill placement is started, but before the vertical height of fill/backfill exceeds 2 feet. 'Special inspection of the initial fill lift and placement of geogrid earth reinforcement will also be necessary. Final rough and finish pad grade tests shall be required regardless of fill/backfill thickness. * Foundation trench inspection - After foundation trench excavations, but before steel placement. * Foundation bearing/slab subgrade soils inspection - Prior to the placement of concrete for proper moisture and specified compaction levels. * Foundation/slab steel inspection - After steel placement is completed, but before the scheduled concrete pour. * Sibdrain/stabilization rock. blanket inspeótion - During the actual placement, all material shall conform to the project material specifications and approved by the project soils engineer. * . Underground utility/plumbing trench inspection After the trench excavations, but befOre installation of the underground facilities. Safety requirements enforced by governing agencies for open excavations apply. Inspection of the pipe bedding may also be required by the project soils engineer. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue' Escondido, California 92029-1229 • Phone (760) 7434214 Mr. Sjirk Zijlstra. September 25, 2006 Page 8 Underground utility/plumbing trench backfill inspection - After the backfill placement is started above the pipe zone, but before the vertical height of backfill exceeds 2 feet. Testing of the backfill within the pipe zone may also be required by the governing agencies. Pipe bedding and backfill materials shall conform to the requirements of governing agencies and project soils report if applicable. All trench backfills shall be mechanically compacted to a minimum 95% compaction levels per ASTM 0-1557, unless otherwise specified. Plumbing trenches over 12 inches deep maximum under the interior floor slabs should also be mechanically compacted and tested for a minimum 95% compaction levels. Flooding or jetting techniquesas a means of compaction method shall not be allowed. * lmprovements,.subgrade inspections -Prior to the placement of concrete or asphalt for proper moisture and specified compaction levels. Ill. MAT I GRADE BEAR FOUNDATIONS Concrete slab-on-ground mat foundations with interior and perimeter grade beams may be considered for building support. Actual mat foundation designs should be provided by the project structural engineer based on design loading conditions and following soil design parameters: * As a minimum, concrete slab-on-ground mat foundations should be a minimum of 10 inches thick reinforced with minimum #4 bars at 16 inches on centers maximum each way, top and bottom. Interior and perimeter grade beams should be a • minimum 18 inches wide and 24 inches deep reinforced with at least 245 bars top and bottom and #3 ties at 24 inches on centers maximum. All depths are measured from the lowest adjacent ground level not including the sand/gravel layer under the mat. Exterior grade beams should enclose the entire building perimeter. Foundation mats should be underlain by 4 inches of clean sand (SE 30 or greater) which is provided with a well performing moisture barrier/vapor retardant (minimum 15-mil plastic) placed mid-height in the sand. In the case of good quality sandy subgrade import soils, as approved by the project geotechnical engineer, the moisture barrier/vapor retardant may be laid directly over the slab subgrade and covered with a minimum 2 inches of clean sand (SE 30 or greater). Foundation bearing soils should be inspected and tested as required, to confirm specified conditions prior to poring the concrete. VINJE & MIODLETON ENGINEERING, INC. • 2450 Vineyard Avenue 0 Escondido, California 92029-1229 0 Phone (760) 7434214 Mr. Sjirk Zijlstra September 25, 2006 Page 9 EXTERIOR CONCRETE SLABS I FLATWORKS All exterior slabs (walkways, patios) should be a minimum 4 inches in thickness, reinforced with #3 bars at 16 inches on centers in both directions placed mid-height in slab. Subgrade soils should be compacted to a minimum 95% compaction levels as specified. Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not to exceed 10 feet maximum) each way. Tool or cut as soon as the slab will support weight and can be operated without disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. Tool orsoftcuts should be a minimum of 1-inch but should not exceed 1%- inches deep maximum. In case of softcut joints, anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. All exterior slab designs should be confirmed in the final as-graded compaction report. * Subgrade soils should be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of concrete. SOILS PARAMETERS AND LATERAL EARTH PRESSURES The following soil design parameters are based on tested representative samples of on-site earth deposits. All parameters should be re-evaluated when the characteristics of the final as-graded soils have been specifically determined: * Design wet density of on-site soil = 130 pcf. * Design angle of internal friction of on-site soil = 31 degrees. * Design active on-site soil pressure for retaining structures = 42 pcf (EFP), level backfill, cantilever, unrestrained walls. * Design at-rest on-site soil pressure for retaining structures = 63 pcf (EFP), non- yielding, restrained walls. * Design passive on-site soil resistance for retaining structures = 406 pcf (EFP), level surface at the toe. * Design co-efficient of friction for concrete on on-site soils = 0.38. * Design net allowable foundation pressure for 95% compacted fills = 2000 psf. * Allowable lateral bearing pressure (all structures except retaining walls) for on-site compacted fill = 200 psf/ft. * A soils module of subgrade reaction of 200 pci may be considered. VINJE & MIODLETON ENGINEERING, INC. 9 2450 Vineyard Avenue 0 Escondido, California 92029.1229 • Phone (760) 743-1214 Mr. Sjirk Zijistra September 25, 2006 Page 10 Notes: * Use a minimum safety factor of 1.5 for wall over-turning and sliding stability. However, because large movements must take place before maximum passive resistance can be developed, a safety factor of 2 may be considered for sliding stability where sensitive structures and improvements are planned near or on top of retaining walls. * When combining passive pressure and frictional resistance the. passive component should be reduced by one-third. * The àllowablefoundation pressures provided herein also applies to dead plus live loads and may be increased by one-third for wind and seismic loading, * The allowable lateral bearing earth pressures may be increased by the amount of the designated value for each additional foot of depth to a maximum of 1500 pounds per square foot. * Use minimum 4500 psi concrete for mat foundation design (also see corrosion mitigation recommendations in enclosed References). VI. ASPHALT AND PCC PAVEMENT DESIGN 1. Asphalt paving: Specific asphalt pavement designs can best be provided at the completion of rough grading based on. R-value tests of the actual finish subgrade soils. However, a. minimum section of 3 inches asphalt on 8: inches Class 2 aggregate base or the minimum section required by the City of Carlsbad, whichever is more, may be considered for initial planning phase cost estimating purposes only for the on-site asphalt paving surfaces outside public and private right-of-way (not for construction).- Final pavement sections will depend on the actual R-value* test results performed on finish subgrade soils, design TI, and approval of the City of Carlsbad. All design sections should be confirmed and/or revised as necessary at the completion of rough pavement subgrade preparations. Revised pavement sections should be anticipated. Base materials should be compacted to a minimum 95% of the corresponding maximum dry density (ASTM 0-1557). Subgrade soils beneath the asphalt paving surfaces should also be compacted to a minimum 95% of the corresponding maximum dry density within the upper 12 inches. . VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue 'Escondido, California 92029-1229 0 Phone (760) 743-1214 Mr. Sjirk Zijlstra September 25, 2006 Page 11 PCC Paving: Residential PCC driveways and parking supported on very low to low expansive (expansion index less than 51) subgrade soils should be a minimum of 5% inches in thickness, reinforced with #3 reinforcing bars at 16 inches on centers each way, placed at mid-height in the slab. Subgrade soils beneath the PCC driveways and parking should also be compacted to a minimum 95% of the corresponding maximum dry density. Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not to exceed 15 feet maximum) each way. Tool or cut as soon as the slab will support weight and can be operated without disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. Tool or softcuts should be a minimum 1-inch in depth but should not exceed 1%-inches deep maximum. In case of softcut joints, anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. General Paving: Base layer and subgrade soils should be tested for proper moisture and the specified compaction levels, and approved by the project geotechnical consultant prior to the placement of the base or asphalt/PCC finish surface. Base section and subgrade preparations per structural section design, will be required for all surfaces subject to traffic including roadways, travelways, drive lanes, driveway approaches and ribbon (cross) gutters. Driveway approaches within the public right-of-way should have 12 inches subgrade compacted to a minimum 95% compaction levels, and provided with 95% compacted Class 2 base section per the structural section design. Base layer under curb and gutters should also be compacted to a minimum 95% Compaction levels. Base section may not be required under curb and gutters, and sidewalks in the case of very low expansive subgrade soils (expansion index less than 21). Appropriate recommendations should be given in the final as-graded compaction report. VII. GENERAL RECOMMENDATIONS The minimum foundation design and steel reinforcement provided herein are based on soil characteristics and are not intended to be in lieu of reinforcement necessary for structural considerations. Adequate staking and grading control is a critical factor in properly completing the recommended remedial and site grading operations. Grading control and staking should be provided by the project grading contractor or surveyor/civil engineer, and VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue 0 Escondido, California 92029-1229 • Phone (760) 743-1214 Mr. Sjirk Zijlstra September 25, 2006 Page 12 is beyond the geotechnical engineering services. Inadequate staking and/or lack of grading control may result in unnecessary additional grading which will increase construction costs. Footings located on or adjacent to the top of slopes should be extended to a sufficient depth to provide minimum horizontal distance of 7 feet or one-third of the slope height, whichever is greater (need not exceed 40 feet maximum) between the bottom edge of the footing and face of slope. This requirement applies to all improvements and structures including fences, posts, pools, spas, etc. Concrete and AC improvements should be provided with a thickened edge to satisfy this requirement. Open or backfilled trenches parallel with a footing shall not be below a projected plane having a downward slope of 1-unit vertical to 2 units horizontal (50%) from a line 9 inches above the bottom edge of the footing, and not closer than 18 inches form the face of such footing. Where pipes cross under-footings, the footings shall be specially designed. Pipe sleeves shall be provided where pipescross through footings or footing walls, and sleeve clearances shall provide for possible footing settlement but not less than 1- inch all around the pipe. Foundations where the surface of the ground slopes more than 1-unit vertical in 10 units horizontal (10% slope) shall be level or shall be stepped so that both top and bottom of such foundations are level. Individual steps in continuous footings shall not exceed 18 inches in height, and the slope of a series of such steps shall not exceed 1-unit vertical to 2-units horizontal (50%) unless otherwise specified. The steps shall be detailed on the structural drawings. The local effects due to the discontinuity of the steps shall also be considered in the design of foundations as appropriate and applicable. Expansive clayey soils should not be used for backfilling of any retaining structure. All retaining/basement walls should be provided with a 1:1 wedge of granular, compacted backfill measured from the base of the wall footing to the finished surface, and a well constructed back drainage system as shown on the enclosed Plate 1. All underground utility and plumbing trenches should be mechanically compacted to a minimum 95% of the maximum dry density of the soil unless otherwise specified. Care should be taken not to crush the utilities or pipes during the compaction of the soil. Non-expansive, granular backfill soils should be used. Trench backfill materials and compaction beneath pavements within the public right-of-way shall conform .to the City of Carlsbad requirements. VINJE & MIDDLETON ENGINEERING, INC. a 2450 Vineyard Avenue • Escondido, California 92029-1229 0 Phone (760) 7434214 Mr. .Sjirk Zijlstra September 25, 2006 Page 13 Site drainage over the finished pad surfaces should flow away from struótures onto the street in a positive manner. Care should be taken during the construction, improvements, and fine grading phases not to disrupt the designed drainage patterns. Roof lines of the buildings should be provided with roof gutters. Roof water should be collected and directed away from the buildings and structures to a suitable location. Final plans should reflect preliminary recommendations given in this report. Final foundations and grading plans may also be reviewed by the project geotechnical consultant for conformance with the requirements of the geotechnical investigation report outlined herein. More specific.recommendations may be necessary and should be given when final grading and architectural/structural drawings are available. All foundation trenches should be inspected to ensure adequate footing embedment and confirm competent bearing soils. Foundation and slab reinforcements should also be inspected and approved by the project geotechnicàl consultant. The amount of shrinkage and related cracks that occurs in the concrete slab-on- grades, flatworks and driveways depend on many factors the most important of which is the amount of water in the concrete mix. The purpose of the slab reinforcement is to* keep normal concrete shrinkage. cracks closed tightly. The amount of concrete shrinkage can be minimized by reducing the amount of water in the mix. To keep shrinkage to a minimum the following should. be considered: * Use the stiffest mix that can be handled and consolidated iatisfactorily. * Use the largest maximum size of aggregate that is practical. For example, concrete made with %-inch maximum size aggregate usually requires about 40- lbs. more (nearly 5-gal.) water per cubic yard than concrete with 1-inch aggregate. * Cure the concrete as long as practical. The amount of slab reinforcement provided for conventional slab-on-grade construction considers that good quality concrete materials, proportioning, craftsmanship, and control tests where appropriate and applicable are provided. A preconstruction meeting between representatives of this office, the property owner or planner, city inspector, as well as the grading contractor/builder is recommended in order to discuss grading/construction details associated with site development. VINJE & MIDDLETON ENGINEERING, INC. 9 2450 Vineyard Avenue 0 Escondido, California 92029-1229 0 Phone (760) 743-1214 Mr. Sjirk Zijlstra September 25, 2006 Page 14 VIII. LIMITATIONS The conclusions and recommendations provided herein have been based on available data obtained from the review of pertinent reports and plans, subsurface exploratory excavations as 'well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in our laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between excavations. Of necessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of VINJE & MIDDLETON ENGINEERING, INC., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our inspection or control. The property owner(s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco are associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairline stucco cracks will often develop at window/door corners, and floor surface cracks up to ½-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. This report is issued with the understanding that the owner or his representative is responsible to ensure that the information and recommendations are provided to the project architect/structural engineer so that they can be incorporated into the plans. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 920294229 0 Phone (760) 743-1214 Mr. SjirkZijlstra September 25, 2006 Page 15 The project soils engineer should be provided the opportunity for a general review of the project final design plans and specifications in order to ensure that the recommendations provided in this report are property interpreted and implemented. The project soils engineer should also be provided the opportunity to verify the foundations prior the placing of concrete. If the project soils engineer is not provided the opportunity of making these reviews, he can assume no responsibility for misinterpretation of his recommendations. Vinje & Middleton Engineering, Inc., warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Job #03-348-P will help to expedite our response to your inquiries. - We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. AO n4U-J~ Dennis Middleton CEG#980 Eo MIDO1 CEG98O OX * CERTIFIED * ENGINEERING JV __ S. tj1ehdi S. Shariat ReE#46174 CA~- No. 46174 Exp. 12-31.06 ) /._ OF' IVI 2FCA Steven J. Melzer CEG #2362 Distribution: Addressee (5) Enclosures: Plate I Appendices A-C c:s'jtlmyfiles/06updates103-348-13 No. 2382 CERTIFIED , ENGINEERING GEOLOGIST Exp. 5-3 _•) ('J VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue 0 Escondido, California 92029-1229 0 Phone (760) 743-1214 p. r I- p. r r APPENDIX A I- r Preliminary Geotechnical Investigation Lot 31, Tract 5162, Cove Drive Carlsbad, California March 3, 2004 Prepared For: MR. JERZY J. LEWAK do Nisus Software, Inc. 107 South Cedros Avenue, Suite B Solana Beach, California 92075 Prepared By: VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, Suite 102 Escondido, California 92029 Job #03-348-P VINTE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue Job #03-348-P Escondido, California 92029-1229 Phone (760) 743-1214 Fax (760) 739-0343 March 3, 2004 Mr. Jerzy J. Levak do Nisus Software, Inc. 107 South Cedros Avenue, Suite B Solana Beach, California 92075 PRELIMINARY GEOTECHNICAL INVESTIGATION, LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD, CALIFORNIA Pursuant to your request, Vinje and Middleton Engineering, Inc., has completed the Preliminary Geotechnical Investigation Report for the above-referenced project site. The following report summarizes the results of our research, and review of pertinent geotechnical maps and reports, subsurface field investigation and soil sampling, laboratory testing, engineering analyses and provides conclusions and construction recommendations for the proposed development as, understood. From a geotechnical engineering standpoint, it is our opinion that the site is considered suitable for the support of the proposed duplex condominium building with the associated improvements, provided the recommendations presented in this report are incorporated into the design and construction of the project. ' The conclusions and recommendations provided in this study are consistent with the indicated site geotechnical conditions and are intended to aid in preparation of final development plans and'allow more accurate estimates of the construction costs. If you have any questions or need clarification, please do not hesitate to contact this office. Reference to our Job #03-348-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. I ia CEG98O ' CERTIFIED I * ENGINEERING Dennis Middleton J CEG#980 'OF dAlJe DMTjt , - - - - - - - - - 1 - -I •- - -, -1 -. - 1 - >oomWCnm - = - 'E.° U . C) nrnc)> C) C') V Cl) m 0 m j o z r- mcnm 0 m 0 m -I 0 o r CoC.gO m z 0 _ C g6cD C) < Cl) —IcLw': -u: 0 m ! -Cn0. rr, m co x CD X m m Ma 9. Z Z 0 0 CE Z D z Er :3::: : : Z CL r.L--n.. .. . . • . . . . . . m ar.:.. 0• z .0 J2 z . - ag o. • . . . .vot. . . . . —•. • . (0. . . . . . •o...• . . •A • • • . • • • • . • . 0.z• . • CO) Pr c • • • • . . • • . • • . •••fl••• : : ::::: : : •CD • ro o:::ø:.. . . • .. .. . • • •!.•••• . . I. .0 . . . . . • • HHHHH • . . . . • I- • • . . • • m • • . . . z . . • . - o. cc CO 4 0) UI .ph co) M - t.) 40 CD 01 C)1 C,3 TABLE OF CONTENTS (continued) PLATE NO. Regional Index Map . I Site Plan . 2 Architectural Site Plan ................................................3 Architectural Building Section ..........................................4 Boring Logs (with key) ...............................................5-6 Fault - Epicenter Map ..................................................7 Corrected N-values & Liquefaction Safety Factor Graphs .................8-9 Grain Size Analysis ..................................................10 Engineering Design Information by Foundation Pile, Inc . ....................................... Appendix A PRELIMINARY GEOTECHNICAL INVESTIGATION LOT 31, TRACT 5162, COVE DRIVE CARLSBAD, CALIFORNIA INTRODUCTION The property investigated herein is a small bay-side lot off of Agua Hedionda, near the coast in the City of Carlsbad. The approximate site location is depicted on a Regional Index Map enclosed with this report as Plate 1. We understand that the site is planned for the support of a duplex condominium structure which will occupy much of the lot surface. Consequently, this study was initiated to determine geologic and soils conditions beneath the property and their influence upon the planned development. Deep test hole borings, soil sampling and testing were among the activities conducted in connection with this effort which has resulted in the design and foundation recommendations presented herein. SITE DESCRIPTION The project site is a small, level lot between two developed buildings on either side. Cove Drive provides access and marks the front (western) boundary. A small graded and rock- lined slope marks the rear.(eastern) boundary which descends approximately 8 feet into the lagoonal waters. The lot surface soils support a light cover of native grasses. Site drainage is indistinct with no evidence of scouring or run-off erosion. Details of site conditions are shown on a Site Plan enclosed herein as Plate 2. Ill. PROPOSED DEVELOPMENT An Architectural Site Plan prepared by Zijlstra Architecture, and property layout are depicted on Plate 3. An architectural building section is also included herein as Plate 4. No grading is planned and finish grades are likely to be at or very near the existing ground surfaces. The use of conventional wood-frame with exterior stucco buildings supported on driven prestressed concrete pile foundations with raised structural floor type construction is also anticipated. The rear patio and the driveway will consist of flexible interlocking concrete payers set in sand. The project utilities/plumbing pipes will be suspended from the structural slab/grade beams.. IV. SITE INVESTIGATION Subsurface conditions at the project lot were chiefly determined from the excavation of 2 test boring drilled with a truck-mounted rotary drill. The borings were logged by our project geologist who also retained soil/rock samples for laboratory analysis. Test boring locations are shown on Plate 2. Logs of the borings are enclosed herein as Plates 5 and 6. Laboratory test results are summarized in a following section. VINJE & MIDÔLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 0 Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 2 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 V. GEOTECHNICAL CONDITIONS. The project site is situated upon level terrain created in the 1960's by placing imported fill soils over natural lagoonal areas adjacent to Agua Hedionda. Grading records for engineering inspections and compaction testing of the existing fills are unavailable. Earth Materials The following earth materials underlie the project site: Fill - Imported fill soils directly underlie the project site to an approximate depth of 15 feet. The fill consists chiefly of clayey sands in a loose to very looseand moist to saturated condition overall. Lagoonal Deposit - Natural lagoonal soils underlie site the fills to significant depths. These soils consist of variable sequence of dark colored clayey and silty soils with sandy lenses that occur in a saturated and very soft to very loose condition. Bedrock - The site is underlain at depths by sedimentary bedrock units which characterize nearby hillside terrain. The rocks consist chiefly of sandy to clayey siltstone units found in a cemented and firm condition. Based upon test boring exposures, bedrock units occur at approximate depths of 50 feet below the existing lot surface. - Details of site earth materials are given on the enclosed Boring Logs, Plates 5 and 6. Engineering properties are additionally defined in a following section. Groundwater Subsurface groundwater characterizes the project soil section at depths of 5 to 7 feet below existing lot surfaces. The water reflects lagoonal water which has saturated the underlying soils. The indicated levels are expected to fluctuate slightly, with changing tide levels. . Slope Stability A small graded slope descends into the lagOàn along the north property boundary. The slope is a 2:1 gradient embankment which is provided with large rock rip-rap facing. •No evidence of instability is apparent within the project slope. VINJE & MIDDLETON ENGINEERING, INC. 2450Vineyard Avenue Escondido, California 920294229 0 Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 3 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 D. Faults I Seismicity Faults or significant shear zones are not indicated on or near proximity to the project site. As with most areas of California, the San Diego region lies within a seismically active zone; however, coastal areas of the county are characterized by low levels of seismic activity relative to inland areas to the east. During a 40-year period (1934-1974), 37 earthquakes were recorded in San Diego coastal areas by the California Institute of Technology. None of the recorded events exceeded a Richter magnitude of 3.7, nor did any of the earthquakes generate more than modest ground shaking or significant damages. Most of the recorded events occurred along various offshore faults which characteristically generate modest earthquakes. Historically, the most significant earthquake events which affect local areas originate along well known, distant fault zones to the east and the Coronado Bank Fault to the west. Based upon available seismic data, compiled from California Earthquake Catalogs, the most significant historical event in the area of the study site occurred in 1800 at an estimated distance of 10 miles from the project area. This event, which is thought to have occurred along an off-shore fault, reached an estimated magnitude of 6.5 with estimated bedrock acceleration values of 0.128g at the project site. The following list represents the most significant faults which commonly impact the region. Estimated ground acceleration data compiled from Digitized California Faults (Computer Program EQ FAULT VERSION 3.00 updated) typically associated with the fault is also tabulated: TABLE I L Fault Zone Distance from Site Maximum Probable Acceleration Rose Canyon fault 5 miles 0.244g Newport-Inglewood fault 6.1 miles 0.220g Coronado Bank fault 21.2 miles 0.184g Elsinore fault 24.1 miles 0.142g The location of significant faults and earthquake events relative to the study site are depicted on a Fault - Epicenter Map enclosed herein as Plate 7. VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue ' Escondido, California 920294229 0 Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 4 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 More recently, the number of seismic events which affect the region appears to have heightened somewhat. Nearly 40 earthquakes of magnitude 3.5 or higher have been recorded in coastal regions between January 1984 and August 1986. Most of the earthquakes are thought to have been generated along offshore faults. For the most part, the recorded events remain moderate shocks which typically resulted in low levels of ground shaking to local areas. A notable exception to this pattern was recorded on July 13, 1986. An earthquake of magnitude 5.3 shook County coastal areas with moderate to locally heavy ground shaking resulting in $700,000 in damages, one death, and injuries to 30 people. The quake occurred along an offshore fault located nearly 30 miles southwest of Oceanside. A series of notable events shook County areas with a (maximum) magnitude 7.4 shock in the early morning of June 28, 1992. These quakes originated along related segments of the San Andreas Fault approximately 90 miles to the north. Locally high levels of ground shaking over an extended period of time resulted; however, significant damages to local structures were not reported. The increase in earthquake frequency in the region remains a subject of speculation among geologists; however, based upon empirical information and the recorded seismic history of County areas, the 1986 and 1992 events are thought to represent the highest levels of ground shaking which can be expected at the study site as a result of seismic activity. In recent years, the Rose Canyon Fault has received added attention from geologists. The fault is a significant structural feature in metropolitan San Diego which includes a series of parallel breaks trending southward from La Jolla Cove through San Diego Bay toward the Mexican border. Test trenching along the fault in Rose Canyon indicated that at that location the fault was last active 6,000 to 9,000 years ago. Thus, the fault is classified as 'active" by the State of California which defines faults that evidence displacement in the previous 11,000 years as active. More active faults (listed on the preceding page) are considered most likely to impact the region during the lifetime of the project. The faults are periodically active and capable of generating moderate to locally high levels of ground shaking at the site. Ground separation as a result of seismic activity is not expected at the property. For design purposes, site specific seismic parameters were determined as part of this investigation in accordance with the Uniform Building Code. The following parameters are consistent with the indicated project seismic environment and may be utilized for project design work: VINJE & MIDDLETON ENGINEERING, INC. 02450Vineyard Avenue 0 Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 5 LOT 31, TRACT 5162, COVE DRIVE; CARLSBAD MARCH 3, 2004 TABLE 2 Site Soil Profile Type Seismic Zone Seismic Zone Factor Seismic Source Type Seismic Response Coefficients Na J Nv Ca J Cv Ts SF [ 4 0.4 B J 1.0 I_1.1 I_0.66 I_1.92 I_1.164 I_0.233] According to Chapter 16, Division IV of the 1997 Uniform Building Code. Site probabilistic estimation of peak ground acceleration was also evaluated using the FRISKSP VERSION 4.00 UPDATE (T. Blake, 2000) computer program. Based on Boore et.al (1997), a 10 percent probability of exceedance in 50 years was estimated to generate a site specific peak ground acceleration of 0.350g. The result was obtained from the corresponding probability of exceedance versus acceleration curve. GeologicHazardsandLiquefactionPotential Based on our site specific geotechnical study, the most significant geologic hazard at the project site will be those associated with liquefaction and secondary ground rupture/movements which may be initiated by a major seismic event along a distant active fault. Significant slopes are not present at the project nor is site development expected to construct major graded slope conditions. A soil profile was modeled based on the new boring data and analyzed using the LIQUEFY2 VERSION 1.5 UPDATE (T. Blake, 1998) computer program. Based upon our analysis and assumptions using a design site specific peak ground acceleration of 0.350g, design earthquake magnitude of 7.5 and corrected N- values, saturated site fills and natural lagoonal deposits are highly liquefiable (safety factors less than 1.0). Corrected N-values and liquefaction safety factor graphs are included with this report as Plates 8 and 9. LaboratoryTesting I_Results Earth deposits encountered in our exploratory test excavations were closely examined and sampled for laboratory testing. Based upon our test trench data and field exposures site soils have been grouped into the following soil types: VINJE & MIDDLETON ENGINE EKING, INC. 0 2450 Vineyard Avenue 0 Escondido California 92029-1229 0 Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 6 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 TABLE 3 Soil Type . Description I brown clayey to silty sand (Fill) 2 dark brown to grey fine to medium sand with a trace of clay (fill) 3 grey to brown silty to sandy clay/clayey silt (Lagoonal deposit, fill) 4 tan medium to coarse sand (Lagoonal deposit) 5 dark brown silty to clayey sand (Lagoonal deposit) 6 olive fine sandy to clayey siltstone (Formational rock) The following tests were conducted in support of this investigation: Standard Penetration Tests: Standard penetration tests (SPT) were performed at the time of bore hole drilling in accordance with the ASTM standard procedure 0-1586, using a mechanical drive hammer. The procedure consisted of a standard 51 MM outside diameter sampler, 457 MM in length and 35 MM in inside diameter using 5 foot long AW drill rods. The bore hose was 200 MM (8 inches) in diameter and water was added for bore hole support. The test results are indicated at the corresponding locations on the Boring Logs. Maximum Dry Density and Optimum Moisture Content: The maximum dry density and optimum moisture content of Soil Type I was determined in accordance with ASTM 0-1557. The test result is presented in Table 4. TABLE 4 Location Soil Type Maximum Dry . Density (Ym-pcf) Optimum Moisture Content (uopt-%) I B-I c2' I i I 130.4 I 11.1 Moisture-Density Test (Undisturbed Ring Samples): In-place dry density and moisture content of representative soil deposits beneath the site were determined from a relatively undisturbed ring sample using the weights and measurements test method. The test result is presented in Table 5 and tabulated on the enclosed Boring Logs (Plates 5-6). VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue 0 Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 7 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 TABLES Field Ratio Of In-Place Dry Moisture .. Field Dry Max. Dry. Density To Max. Dry Sample Soil Content Density Density Density* Location Type (w-%) (Yci-pcf) (Ym-pcf) (Yd!Ym X 100) B-I © 3J I 5.8 - 130.4 J loose disturbed sample *Designated as relative compaction for structural fills. Required relative compaction for structural fill is 90% or greater. Expansion Index Test: One expansion index test was performed on a representative sample of Soil Type I in accordance with the Uniform Building Code Standard 18-2. The test result is presented in Table 6. TABLE 6 Sample Location Soil Type Remolded w (%) Saturation (%) Saturated w (%) Expansion Index (El) J_Potential rExpanslon F-B-1 @ 2'. 1 1 9.9 1 50.6 [ 17.9 1 25 1 low (w) = moisture content in percent. Direct Shear Test: One direct shear test was performed on a representative sample of Soil Type 1. The prepared specimen was soaked overnight, loaded with normal loads of 1, 2, and 4 kips per square foot respectively, and sheared to failure in an undrained condition. The test result is presented in Table 7. TABLE 7 Wet Angle of Apparent Sample Soil Sample I Density mt. Fric. Cohesion Location Type Condition I (Yw-pcf) (0-Deg.) (c-psf) I B-I _2' 1 remoldedto90%of Ym @_%wopt F 130.4 31 (_185 S. Grain Size Analysis: Grain size analyses were performed on representative samples of Soil Types 3 and 4. The test results are presented in Table 9 and graphically illustrated on the enclosed Plate 10. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue 0 Escondido, California 92029-1229 0 Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 8 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 TABLE 8 Amount of Material in Soils Finer Than the No. 200 Sieve: The amount of material in soils finer than No. 200 sieve tests were performed on representative selected samples of foundation bearing and pavement subgrade soils in accordance with the ASTM D-1 140. The test results are presented in Table 9. TABLE 9 Location Original Dry Mass (g) Dry Mass Retained after washing (g) Percent of Material Finer Than No. 200 Sieve Predominant Soil Type B-I @2' 751.2 .466.7 38 SM/SC B-I @7W 226.9 137.4 40 SC B-I @ 15' 256.7 - 20.9 92 ML/CL B-I @45' 100.0 72.2 28 SM Liquid Limit Plastic Limit and Plasticity Index: Liquid limit, plastic limit and plasticity index tests were performed on representative samples of Soil Types 3 and 4 in accordance with the ASTM D-4318. The test results are presented in Table 10. TABLE 10 Location Soil Type Liquid Limit (%) Plastic Limit (%) Plasticity In . (P1) B-1@15' 3 59 27 32 B-1 35' 4 - - non-plastic VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue 0 Escondido, California 920294229 0 Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 9 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 9. Sulfate Test: One sulfate test was performed on a representative sample of Soil Type I in accordance with the California Test 471. The test result is presented in Table 11. TABLE 11 Sample Location Soil Type Amount of Water Soluble Sulfate (so4) In Soil (% by Weight) I B-I @ 2' I i I 0.268 VI. CONCLUSIONS Based upon the foregoing investigation, development of the project lot for residential purposes is feasible from a geotechnical viewpoint. However, the site is underlain by a thick section of highly liquefiable loose and saturated soil deposits which will require special geotechnical engineering development techniques. The following factors are unique to the property and will most impact its development from a geotechnical viewpoint: Liquefaction is the most significant geotechnical concern at the project property. Secondary affects such as seismically induced settlements, sand boils, ground spreading and lurching also remain a major concern at the study property. The underlying loose and saturated fills and lagoonal deposits are also highly compressible. Project compressible soils are not suitable for foundation support. The upper fill soil above the water table are susceptible to collapse in their present conditions. However, remedial grading is not planned and project utility/plumbing pipes will be suspended from the structural slab/grade beams, and flexible interlocking payers will be used for the rear patio and driveway construction. In the absence of remedial grading removal and re-compaction, continued repairs of on-grade site improvements supported on the existing soils should be anticipated. The project property is not suitable for the support of shallow conventional foundations, and cut-fill and remedial grading is not planned. peep prestressed driven concrete pile foundations and structural floors should be used as recommended in the following sections. Competent formational bedrock units occur at depths of approximately 50 feet below the existing lot surfaces which could suitably support driven concrete pile foundations. VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue • Escondido, California 920294229 0 Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 10 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 Groundwater was encountered in both exploratory boring excavations at the depth of approximately 5 to 7 feet at the time of our field investigation. Groundwater conditions at the project site is expected to seasonally fluctuate and may impact foundation constructions. Site upper soils include some clay bearing deposits. Finish grade soils are expected to consist of clayey to silty sand (SM/SC) with low to very low expansion potential (expansion index less than 51). VII. RECOMMENDATIONS Recommendations provided herein are consistent with the indicated project conditions and are intended to preclude site adverse geotechnical factors impacting the future building structures. The following may be considered for site development and foundation designs: Cut-fill or remedial grading is not planned. Prestressed driven pile foundations will be used for support of the building. The rear patio and the driveway will consist of flexible interlocking concrete payers set in sand. The project utilities/plumbing pipes will also be suspended from the structural slab/grade beams. Pile foundations should be driven to adequate depths into the underlying formational bedrock bearing stratum by approved impact pile hammers. Actual pile foundations should be designed by the project structural engineer. However, the following geotechnical factors and soils design parameters associated with the structural pile design and installations are appropriate and should be considered where appropriate and applicable: The piles should consist of prestressed concrete piles proportioned, designed and manufactured to sustain the driving stresses and develop the design allowable pile capacity. A qualified contractor with experience with a similar project should be retained. A sample order form by Foundation Pile Inc., for engineering design information is enclosed herein as Appendix A. A minimum of 14 inches square prestressed concrete (fc = 5000 psi) piles or greater may be considered. A point of fixity at a minimum of 3 feet below the contact with the formational units may be considered for determining the maximum moments. * The pile spacing shall not be closer than 2½ times the pile diameter. Maximum spacing should be determined by the project structural engineer. * The capacity of pile groups will be less than the sum of individual piles in the same group and should be considered in the design. Actual supporting VINJE & MIODLETON ENGINEERING, INC. 0 2450 Vineyard Avenue 0 Escondido, California 92029-1229 • Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 11 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 capacity of piles driven closer than 8 times pile diameter, center to center, should be reduced using appropriate group efficiency formulas. * Piles should be driven into the underlying competent formational units until the design allowable pile capacity of 50 kips is developed. Formational units were encountered at the depth of 49 feet in our exploratory boring. Based on our analyses, design allowable pile capacity will be achieved when minimum 5 blows per inch of penetration for the last 3 inches of each pile in to the underlying formational units is indicated by the pile driving. Design blow counts in to the underlying formational units should be confirmed and/or revised as necessary by the project geotechnical consultant in the field based on the driving data obtained from the first pile. Pile lengths are not expected to exceed 60 to 65 feet maximum. Large rocks, cobble zones or hard and cemented layers which could influence pile driving through the site fills/lagoonal deposits were not indicated by our boring excavations where explored. Refer to the enclosed boring logs and gradation analyzes for establishing the characteristics of the underlying deposits for pile driving purposes. Damages to the piles shall be avoided or minimized by squaring the driving head with the energy source. Appropriate pile-driving caps and/or cushions should be used. Driving should be sopped when the required driving resistance is encountered. Driving refusal is defined as 4 to 5 (approximately) blows for the last 1h-inch of driving. * Actual pile capacities may vary, based on the blow counts. The design allowable pile capacity, however, is for dead plus live loads and may be increased by one-third for wind and seismic loads. * Pile settlement should be limited to Y2-inch maximum and less than 14-inch differential due to liquefaction and load induced settlements. * Piles may be pre-drilled with an auger with a diameter less than the pile width. Pre-drilling, if used, shall be terminated a minimum of 5 feet above the final pile tip elevations. Pile driving should not damage or disturb the existing adjacent structures and improvements. * Pile driving shall be continuously inspected and monitored by the project geotechnical consultant. Added or modified recommendations should be given in the field based on the data obtained during the installations as appropriate. VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue • Escondido, California 920294229 0 Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 12 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 Grade beams and raised structural floors also designed by the project structural engineer should be considered for the planned buildings. Based upon the results of the tested soil sample, the amount of water soluble sulfate (SO4) in the soil was found to be 0.268 percent by weight which is considered severe according to the California Building Code Table No. 19-A-4. Portland cement Type V and minimum 4500 psi (fc) concrete should be used. Flexible interlocking concrete payers set in sand are considered for the rear patio, driveway and on-site improvements. The payers may be placed over the existing subgrade soils, however, continued repairs and maintenance due to subgrade settlements should be anticipated. Final foundation and design plans should be provided to the project geotechnical consultant for review. Added or modified recommendations may be necessary based on the final design plans, and should be given at that time. VIII. LIMITATIONS The conclusions and recommendations provided herein have been based on available data obtained from pertinent reports and plans, subsurface exploratory excavations as well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in our laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between excavations. Of necessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of VINJE & MIDDLETON ENGINEERING, INC., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cuts, or changing drainage patterns which occur without our inspection or control. VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 7434214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 13 LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD MARCH 3, 2004 The property owner(s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco are associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairline stucco cracks will often develop at window/door corners, and floor surface cracks up to 1/8-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. Vinje & Middleton Engineering, Inc. warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Job #03-348-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. 1*1 Dennis Middleton CEMT CEG #980 ENGINE Op c S. Shariat 174 Steven J. I RG #6953 DM/SMSS/SJM/jt Distribution: Addressee (1) Zijlstra Architecture (4) JAY41, NO.6953 Exp.5.3i.o J!J VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue • Escondido, California 92029-1229 0 Phone (760) 7434214 TOPO! map printed on 03/09/04 from SnDiegotpoand UndtPedtpg 117,333330 W WGS64 117316670 W '\ li•Ii UEfJA\ fiSTA _7'. < Z z I - k A p'- ' IN lflT i WT VA 4A4D jIAJ A Well 0 \\ s 34 8 % ?-' \ I XfL ne 49, - vaey \( #( JE High Sth$ TUT Fk Id A Aix- St \-- '!Iftnh 69 • Ln vo sJTE IUICAT1( .. v a - - I - • \ ::", - ---- -' II ' }eservoIr - - - .1 low *tkFarr 1 - - :\ \ i'J;' \ ., CORP \. \\ 11733333° W WGSS4 11731667° W TN*/MN 1/2 EMILE INO 1 FEET a 500i 1000 V Printed from TOPO! 01999 Wildf1or Pmductios (wwtopo corn) SITE tht PLAN LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD, CALIF. 03-348—P Location of test boring Scale: 1 U201 BOAT BAY BAY SL:T PATIO )IHJJ —1: J I PROPOSED I • -o Ext. house 'VACANT LOT31 -ti Ext. house CONC. I JI J-f- 11COfip1 SIDEWALK COVE DRIVE COVE DRIVE PLATE 2 PRIMARY DIVISIONS GROUP SECONDARY DIVISIONS SYMBOL GRAVELS CLEAN GW Well graded gravels, gravel-sand mixtures, little or no fines*. GRAVELS CC 0 g MORE THAN HALF (LESS THAN GP Poorly graded gravels or gravel-sand mixtures, little or no fines. OF COARSE 5% FINES) GRAVEL GM Silty gravels, gravel-sand-silt mixtures, non-plastic fines. co M Q FRACTION IS a LL Z LU W OzN LARGER THAN WITH NO. 4 SIEVE FINES GC Clayey gravels, gravel-sand-clay mixtures, plastic fines. < cr < I (f I Ir j SANDS CLEAN SW. SANDS Well graded sands, gravelly sands, little or no fines. MORE THAN HALF (LESS THAN SP Poorly graded sands or gravelly sands, little or no fines. OF COARSE 5% FINES) < 8 w FRACTION IS SANDS SM Silty sands, sand-silt mixtures, non-plastic fines. Cr CD SMALLER THAN WITH - NO. 4 SIEVE SC FINES Clayey sands, sand-dày mixtures, plastic fines. W ML Inorganic silts and very fine sands, rock flour, silty or clayey fine u.. o w US SILTS AND CLAYS sands or clayey silts with slight plasticity. CL Inorganic clays of low to medium plasticity, gravelly clays, sandy LIQUID LIMIT IS LESS THAN 50% clays, silty clays, lean clays. OL Organic silts and organic silty clays of low plasticity. U) z u MI-i Inorganic silts, micaceous or diatomaceous fine sandy or silty < i —' CY . SILTS AND CLAYS soils, elastic silts. CH zO!z Inorganic clays of high plasticity, fat clays. LU IrW Z LIQUID LIMIT IS GREATER THAN 50% OH Organic clays of medium to high plasticity, organic silts. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils. GRAINSIZES U.S. STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINGS 200 40 10 4 3/4" 3" 12" SAND I GRAVEL I I SILTS AND CLAYS I 'COBBLES' BOULDERS FINE I MEDIUM I COARSE I FINE I COARSE I I RELATIVE DENSITY ANDS, GRAVELS AND NON-PLASTIC SILTS BLOWS/FOOT VERY LOOSE 0 - 4 LOOSE 4-10 MEDIUM DENSE 10 -30 DENSE 30 -50 VERY DENSE OVER 50 CONSISTENCY CLAYS AND PLASTIC SILTS STRENGTH BLOWS/FOOT VERY SOFT 0-'/4 0-2 SOFT 'A-Vs 2-4 FIRM '/2 -1 4-8 STIFF 1-2 8-16 VERY STIFF 2-4 16-32 HARD OVER 4 OVER 32 Blow count, 140 pound hammer falling 30 inches on 2 inch O.D. split spoon sampler (ASTM D-1 586) Unconfined compressive strength per SOILTEST pocket penetrometer CL-700 V Sand Cone Test • Bulk Sample 246 = Standard Penetration Test (SPT) (ASTM D-1 586) with blow counts per 6 inches 0 Chunk Sample 0 Driven Rings 246 = California Sampler with blow counts per 6 inches VINJE & MIDDLETON KEY TO EXPLORATORY BORING LOGS ENGINEERING, INC Unified Soil Classification System (ASTM D-2487) 2450 Vineyard Ave., #102 Escondido, CA 92029-1229 PROJECT NO. I KEY BORING LOG DEPTH SAMPLE Description USGS MOISTURE DRY DENSITY RELATIVE COMPACTION FT SYMBOL (%) (PCF) (%) FILL: - - Clayey to silty sand. Brown color. Moist. Loose. SM/SC 5.0 - Incomplete sample recovery at 3'. ST-I Clayey fine to medium sand with clay. Dark brown to grey color. Saturated. Free water visible. Very - - - - loose. SC 10 o Minimal sample recovery at 7W. No sample 3.5 recovery at 10'. ST-2 ) LAGOONAL DEPOSIT: Clayey silt to silty clay. Grey to brown color. 1 Locally sandy. Highly weathered. Very soft. High - plastic. Saturated. MUCH -20 - At 25', sampler sunk to 18" under weight of drill - stem. -25---- ST-3 ML ho Silt. Dark grey color. Saturated. Plastic. Very soft. - - Some shell fragments. ST-3 SW - 30 - Medium to coarse sand. Tan color. Saturated. - - Free water visible. Loose. ST-4 - - 35- 110,5,5 . Silty sand. Clayey. Dark grey color. Medium SM - - dense. ST-5 ML 40 /BEDROCK- - Fine sandy to clayey siltstone. Olive color. Moist. - - Cemented. Friable. - - ST-6 45_ iI467 _ -50- ) End Test Boring at 56W. -55 117819/ - - j Groundwater at 5'. Water added to aid drilling. - - - - Boring filled with bentonite. Bulk Sample U PROJECT: COVE DRIVE. CARLSBAD . Ring Sample. 0 SPT Sample Project No: 03-348-P Date Drilled: 8-14-03 Logged By:SJM Groundwater V Truck-mounted rotary drill, 8" Hollow stem auger. Drill, Sample Method: 140 lb. Hammer. 30" mechanical drop. 5' AW rods. PLATE 5 VINJE & MIDDLETON ENGINEERING, INC. ' BORING LOG 13-2 fla'rm+i,,an DRY RELATIVE DEPTH SAMPLE USGS MOISTURE DENSITY COMPACTION FT SYMBOL (%) (PCF) , (%) -- FILL: Silty sand. Trace of clay. Medium to coarse SM/SC - - I grained. Very moist. Loose. ST-2 - - Clayey silt to silty clay. 'Dark brown color. Very moist. Very soft. Low plastic. - - - ML/CL - - Becomes pale brown color below 10'. -10- IIo,i,i 5T3 :5: End Test Boring at 16W. :20: Groundwater at 7'. Boring filled with bentonite. -25- -30- -35 - 40 - -45 -. -50 - Bulk Sample I PROJECT: COVE DRIVE, CARLSBAD Ring Sample 0 SPT Sample II Project No: 03-348-P Date Drilled: 8-14-03 Logged By: SJM Groundwater ..L Truck mounted rotary drill, 8" Hollow Stem Auger. PLATE 6 Drill, Sample Method: 140 lb. Hammer, 30" mechanical drop. 5" AW rods. VINJE &' MIDDLETON ENGINEERING, INC. -\ ' Y / i / 0 2- iL \ to 0 41 in 6 — — q ee b N 0. — - - SITE _5 Son Diego 0 - c--- - \ 30 20 10 0 30 MILES FAULT — EPICENTER MAP SAN DIEGO COUNTY REGION INDICATED EARTHQUAKE EVENTS THROUGH 75 YEAR PERIOD (1900-1974) Map data is compiled from various sources including California Division of Mines and Geology, California Institude of. Technology and the National Oceanic and Atmospheric Administration. Map is reproduced from California Division of Mines and Geology, "Earthquake Epicenter Map of California; Map Sheet 39." Thrthquake Magnitude ..............4.0T04.9 0 ............5.0 TO 5.9 PROJECT: Job #03-348-P ID ............ 6.OTOG.9 (NID ..........7.0 TO 7.9 COVE DRIVE, CARLSBAD -- -- Fault. PLATE: 7 0 -5 -10 -15 -20 1: 7m 035 -40 -45 7m -50 -55 0 5 10 15 20 25 30 35 N160(bpf) I I J I • I P p p 1 I P (NI)60cs LOT 31 9 TRACT 5162 PLATE 8 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 0.0 Factor of Safety LOT 31, TRACT 5126 0.5 1.0 1.5 2.0 F.S. PLATE 9 Humb"i I. APPENDIX A I UTILITY INUET' 0 OIdcastIe ENGINEERING DESIGN INFORMATION REQUIREMENTS YOR PRESTRESSED CONCRETE PILES Projcc . PllaSiaiasdSb&pe - -- Is thee a miiirnum coaaete stregih specified? tc_ psi @28 days uiwifer Provide Pile Loads as Strength level (Fsc&ord Loads, 1999 UBC) What are the Loads? PrOVide total maxTm loads chat Our pile cm section will s. Include any P.Delta Mons due to laterally unsupported lengths if applicable. Show breakdown for Dead, Live and Seismic, itavallable; Dead Live EocW Total - -- -T Aadai Comprsuioa (kips or tons) Azial Teastoa (kips or tons) - - - ____ Bending Moare*t 0001-Icips) Sbear(kips) Specify Load Combinations to be desied for 13 _____ and Compression 0 Bending and Tension, Other, dambe ' 1ezural Length In Feet_- (attach Moment or Deflection Diaaw) NOTE: The above loads axid combinations should be shown on the Stnctural Drawings. Wcbe loads are oat shown, this fonn can be sent to the Structural Eugjneer to be completed. Sails Reports are good background information but should nor be used to obtain actual pile loads. Actual pile loads and conthinauons caine frosn the structure itself (and hence Strucnal Engineers Drawings). - -- (We) 350.1 584 Fax (906) 350-0620 ,0 FOUNDATION PILE, INC. CORROPAO ME** froLoingluxa JEFF REDMAN MsW Sisa Mnagr - - Pb Bo* 1107 7, CA 92334 Page 2 of 3 Customer Initial Pi Project le size Are there any spWified Structural Drawing Derails showing the following: Concrete cover over Spiral 13 Siraud quantity, size and Location Reinforcing bar length, ze, location and quantity Spiialsze and Spacing 13 Dowel tubes Strand Extensions D Rebar Extensions let Tubes For boxes checked above please attach it copy of Stntetural Drawing details. It the infonnanon is not in the Smcwral Drawing derails please artach copies of relevant portions of specifications or a sketch of what you or your cuercuier warn. How much cilia length is required at the top of the pile To allow for cut off? Any Special Codngs required on spiral, atrand or rebar? Please descr*bc See Page 3 Page 3 of 3 F p - / NOTE: The above information is a minimum that we ruire to design your pr dconc pile. 1lcae sip ddatc the boom of this pageto show this i$ what you want. Bawd on the above information we will engineer your pile and provide you with a drawing for fha1 appioval. Wemuac have you sign the drawing before we chedale production If Calcubczous andlor a Conczte Mix Design are required by a Registered Civil FaSinm these will also be provided with your drawing. The cost of Engineering is included in our qt$otc. If, however, thIC me later changes 10 the inlorinanon given on this form additional engeermg costs will be charged at the following rates: Registered Engineer $120.O(bour CAD Operator S0.00/hour Changes to this information will also result in delays to the submittal, production and dcbve*y schutules I'leasc give the items on this form careful consideration. Cusmomera who provide accurate inthniation up front will obviously receive products sooner than those who make changes Customer Signature Date Contractor Name_________________________ Job Name lob Local= For Internal Use Only; Cie Noc____ MD QCM - APPENDIX B P.NTTNTPPP 2450 Vineyard Avenue Job #03-348-P Escondido, California 920294229 Phone (760) 743-1214 Fax (760) 739-0343 November 19, 2003 Mr. Jerzy J. Lewak do Nisus Software, Inc. 107 South Cedros Avenue, Suite B Solana Beach, California 92075 ADDENDUM GEOTECHNICAL REPORT, LOT 31, TRACT 5162, COVE DRIVE, CARLSBAD, CALIFORNIA In response to your request, we have completed an evaluation of an alterative ground stabilization method and foundation system which can provide adequate support for the planned duplex condominium buildings at the above-referenced project site. Alternative ground stabilization techniques and foundation support are available. -However, the choice of an alterative method will depend on economic feasibility versus pros and cons of each technique. The following alternative ground stabilization method and foundation support system may be considered in lieu of driven concrete piles and structural floors as previously recommended in our original report dated September 24, 2003: I. Near Surface Ground Stabilization The building envelope plus a minimum of 5 feet where possible, and as directed in the field, should be over-excavated to a minimum depth of 5 feet below the existing ground levels. Based on our subsurface exploratory excavations, the groundwater levels at the project areas are approximately 5 to 7 feet below the existing ground surfaces at the time of our field investigation. Removal depths will be predominantly above the indicated water table levels. However, construction during the dry months of the year should be considered. The building envelope includes all exterior pad footings, pop-outs, canopy supports, etc. Due to very loose to soft soils conditions in the project areas appropriate construction equipments (such as an excavator) should be considered for soil removals. The soft bottom of over-excavations should be stabilized by placing minus 12-inch combined gradation rocks and tracking/consolidating with heavy construction equipment. Rock placement should continue until full rock interlocking conditions and non-yielding bottom of over-excavation is achieved as approved in the field by Mr. Jerzy J. Lewak November 19, 2003 Page 2 the project geotechnicalengineer. Based on our experience with similar projects, rocks are typically pushed with heavy equipments approximately 2-3 feet into the soft soils before suitable bottom conditions are achieved. However, only actual site conditions will determine the quantity of rocks required to achieve non-yielding conditions. Dewatering sump pump(s) should be installed at low point(s) in the excavation as necessary and become operational at the time of initial rock placement and remain in operation until the completion of the bottom stabilization work is completed as directed in the field by the project geotechnical consultant. Minus I 1,4 inch rocks (combined gradation ranging from 1%-inches to %-inch is also acceptable) should then be placed and tracked-in with heavy construction equipment over the minus 12-inch rocks to achieve a level surface at least 12 inches above the high static groundwater levels established at the site unless otherwise directed in the field. A layer of Mirafi 500X soil separation fabric should then be laid over the approved bottom and covered with a lift (8 to 12 inches) of better quality on-site or sandy import soils which are properly moisture conditioned and compacted as directed in the field. Upon approval of the project geotechnical engineer, a layer of Tensar Geogrid BX- 1200 (or greater from the same series) should then be neatly placed over the initial fill lift. The second lift of fill (12 inches maximum) should then placed over the Geogrid and compacted to a minimum of 95% compaction levels (per ASTM 0- 1557) as directed in the field. A second layer of Geogrid may also be required and should be placed over the approved bottom as directed in the field, and covered with 95% compacted fills. Fill placement should continue until final design grades are achieved. Consideration may also be given to raise the building pad above the existing ground levels as mush as possible. All site fills and back-fills should be adequately processed, thoroughly mixed,. moisture conditioned to near or slightly above optimum moisture levels as directed in the field, placed in thin uniform horizontal lifts and mechanically compacted to a minimum of 95% of the corresponding laboratory maximum dry density per ASTM D-1557, unless otherwise specified. On-site soils will shrink approximately 15% to 25% on volume basis when compacted to a minimum of 95% levels. Additional import soils, if required to complete grading and achieve final design grades, should be sandy granular deposits (SW/SM) with very low expansion potential (expansion index less than 21) .VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue • Escondido, California 920294229 0 Phone (760) 743-1214 Mr. Jerzy J. Lewak November 19, 2003 Page 3 according to the UBC classification. Import soils should be inspected, tested as necessary, and approved by the project geotechnical engineer prior to the delivery to the site. 8. Geotechnical inspections will be required during the construction particularly when placing the initial rock mat in order to monitor ground behavior. Remedial grading operations including removals, suitability of earth deposits used as compacted fill, and compaction procedures should be continuously inspected and tested by the project geotechnical consultant and presented in the final as-graded compaction report. The nature of finished foundation bearing and subgrade soils should also be confirmed in the final compaction report at the completion of grading. Unexpected conditions may result in revised stabilization procedures including added rocks, fabrics and Geogrid as established in the field. Field conditions will control actual stabilization procedures. II. Mat I Grade Beam Foundations 1. Concrete slab-on-ground mat foundations with interior and perimeter grade beams may be considered for building support. Actual mat foundation designs should be provided by the project structural engineer based on design loading conditions and the following soil design parameters: * A soil module of subgrade reaction of 200 pci may be considered. * A design coefficient of friction of 0.38 may be considered for concrete on foundation bearing soils. * A 2000 psf net allowable foundation pressure may be considered for certified 95% compacted foundation bearing soil. * Use a minimum 3000 psi concrete for mat foundation design. * Concrete slab-on-ground mat foundations should be a minimum of 10 inches thick, reinforced with a minimum of #4 bars at 16 inches on centers maximum each way, top and bottom. Interior and perimeter grade beams should be a minimum of 18 inches wide and 24 inches deep, reinforced with at least 245 bars top and bottom and #3 ties at 24 inches on centers maximum. All depths are measured from the lowest adjacent ground level not including the sand/gravel layer under the mat. Exterior grade beams should enclose the entire building perimeter. VINJE & MIDDLETON ENGINEERING, INC. ' 2450 Vineyard Avenue • Escondido, California 92029-1229 0 Phone (760) 743-1214 Mr. Jerzy J. Lewak November 19, 2003 Page 4 * Foundation mats should be underlain by 4 inches of clean sand (SE 30 or greater) which is provided with a 6-mil plastic moisture barrier placed mid-height in the sand. In the case of good quality sandy subgrade soils, as approved by the project geotechnical engineer, the 6-mil plastic moisture barrier may be laid directly over the slab subgrade and covered with a minimum of 2 inches of clean sand (SE 30 or greater). 2. Foundation bearing soils should be inspected and tested as required to confirm specified conditions prior to poring the concrete. III. General Recommendations Recommendations provided in the referenced report, dated September 24, 2003, also remain valid and should be incorporated into the designs and implemented during the construction phase where appropriate and applicable. Uniform and stable subgrade soil conditions should also be constructed underneath the planned site driveway, parking and improvements. For this purpose, the upper loose to soft compressible soils should be removed and recompacted using the remedial grading techniques. The existing eastern fill slope may also require further stabilization. Typical depths of removals in the driveway, parking and improvement areas will be on the order of 3 to 4 feet. However, locally deeper removals may be necessary based on the actual field exposures and should be anticipated. Fill placement and compaction requirements will remain unchanged as specified. Final plans should reflect preliminary recommendations given in this report and reviewed and approved by the project geotechnical consultant. More specific recommendations may also be necessary and should be given when final grading and architectural/structural drawings are available. IV. Pros and Cons The driven concrete pile foundations and structural floor recommendation outlined in our original report dated September 24, 2003, were provided with the intent to prevent impacts of liquefaction induced settlements in a major seismicevent. Alternative remedial grading and mat/grade beam foundation techniques will provide an adequate and safe building support and preclude significant structural damage or compromising the safety of its inhabitants in the -event of a major seismic activity. However, liquefaction induced settlements of the deeper underlying lagoonal deposits may still VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue • Escondido, California 92029-1229 0 Phone (760) 743-1214 Mr. Jerzy J. Lewak November 19, 2003 Page 5 occur causing pad grade irregularities requiring re-leveling and repairs. Other secondary affects such as ground spreading and sand boils will not be a factor provided our remedial grading recommendations for each alterative method are implemented. The home owner(s) should evaluate the cost-benefit aspects 0f each alternative for choosing a construction technique. The chosen construction technique and its pros and cons should also be disclosed to the future prospective buyers and/or home owner(s). If you have any questions or need clarification, please do not hesitate to contact this office. Reference to our Job #03-348-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. HI 111111111111111&4M j ~ W Y"WRAZIN Dennis Middleton CEG #980 /ED GS0 4s 'CEG98O * CERTIFIED * ENGINEERING - ' Op CA 0 i" S. Mphdi S. Shariat w No. 46174 Re'5#46 174 cr Exp. 12-31.06 DM/SMSS/jt Distribution: Addressee (2) - Zijistra Architecture, Attn: Mr. Sjirk Zijlstra (2) c:IjtJIetters.03/03-348-P VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Vineyard Avenue 0 Escondido, California 920294229 0 Phone (760) 743-1214 APPENDIX C VINTE & MIDDLETON ENGINEERING., INC. 2450 Vineyard Avenue Job #03-348-P Escondido, California 92029-1229 Phone (760) 743-1214 July 14, 2006 Fax (760) 739-0343 Zijistra Architecture Attn: Mr. Sjirk Zijistra 731 South Highway 101 Suite I L Solana Beach, California 92075 FOUNDATION PLAN REVIEW, PROPOSED THREE-STORY TWIN HOMES, LOT 319 TRACT 5162, COVE DRIVE, CARLSBAD, CALIFORNIA We have received and reviewed the project foundation plans and details for the above- referenced two units three-story residential building construction, prepared by Zijlstra Architecture (last dated June 12, 2006). According to the project plans, the project building will be supported on 15 inches square prestressed concrete driven piles and grade beam type foundations. The lower floors will be designed structural slabs spanning over the grade beams. Based on our review of drawings made available to us, and from a geotechnical engineering point of view, project foundation plans/details are in substantial compliance with our report entitled "Preliminary Geotechnical Investigation, Lot 31, Tract 5162, Cove Drive, Carlsbad, California," Job #03-348-P, dated March 3, 2004. The following comments are appropriate and should be considered and/or incorporated into the final foundation plans and implemented during the construction phase wherever appropriate and applicable: The referenced Preliminary Geotechnical Investigation Report, dated March 3, 2004, should be considered a part of the project foundation plans. Based upon the results of the tested soil sample, the amount of water soluble sulfate (SO4) in the soil was found to be 0.268 percent by weight which is considered severe according to the California Building Code Table No. .19-A-4. Consequently, the project site is classified as corrosive, and corrosion mitigation should be implemented and incorporated into the design of project structures and improvements as appropriate. A corrosion engineer may also be consulted in this regard. Portland cement Type V (minimum fc = 4500 psi, maximum water cement ratio = 0.45) or as determined by the project corrosion/structural engineer, should be considered. Mr. Sjirk Zijlstra July 14, 2006 Page 2 3. All construction works should be continuously inspected and tested as necessary and appropriate. Special geotechnical engineering .inspections will be required for the pile driving operations. The project contractor shall prepare and submit to the architect/engineer of work, detailed pile data and plant certifications as well as delivering, staging, driving methods and hammer data (including make and model number) for review and approval prior to the initiation of actual works. A table listing all construction works requiring special inspections may be included in the project plans. Engineering construction inspections and test results should be presented in written field and final reports. All design recommendations should be further field verified, confirmed, or revised if necessary. If you have any questions or need clarification, please do not hesitate to contact the undersigned. Reference to our Job #03-348-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Distribution: Addressee (2, fax) c:ltImyflIes/06-updates,etc. VINJE & MIDOLETON ENGINEERING. INC. 0 2450 Vineyard Avenue • Escondido, California 920294229 0 Phone (760) 743-1214