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HomeMy WebLinkAbout; Rancho Santa Fe Road and Mission Estancia; Updated Recommendations; 1989-11-27REPORT OF UPDATED RBGCHHENDKTIONS TIENDA DE IA ESQUINA RANCTO SANTA FE ROAD AND MISSION ESTANCIA CARLSBAD, CALIFORNIA PREPARED FOR: Cunningham - Barisic Development Company 340 South Flover Street Orange, California 92668 PREPARED BY: Southern California Soil & Testing, Inc, Post Office Box 20627 6280 Riverdale Street San Diego, California 92120 SOUTHERN CALIFORNIA SOIL AND TESTING, INC. 62SD RIVERDALE ST. SAN DIEGD, CALIF. 921 ZQ ' TELE 2BO-43Z1 • P.O. BOX ZD6Z7 SAN DIEGD, CALIF. 921 ZD ENTERPRISE ESCDNDIDQ,CALIF.9ZDZ5 TELE 7 A 6 - A 5 November 27, 1989 Cunningham - Barisic Development Corrpany 340 South Flower Street Orange, California 92668 SCS&T 8921180 Report No. 1 ATTENTION: Mr. Mark Gerber SUBJECT: Updated Recommendations, Tienda De La Esquina, Rancho Santa Fe Road and Mission Estancia, Carlsbad, California. REFERENCES: 1) "Tentative Map - Site Development Plan, Tienda De La Esquina;" Rick Engineering Company; Printed October 25, 1989. 2) "Report of In-Place Density Tests, SE-17 Site;" Southern California Soil and Testing, Inc.; December 19 1985. 3) "Report of Geotechnical Investigation, Rancho Santa Fe Road Inprovements and SE-17 Site;" Southern California Soil and Testing, Inc.; Septeirfoer 11, 1985. Gentlemen: In accordance with your request, we have prepared this report to present updated site preparations and foundation recommendations for the subject site. The following recommendations reflect current geotechnical State-of-the-Practice standards in the San Diego County area and the proposed development scheme shown on the referenced map. In conjunction with the preparation of this report we performed a site reconnaissance. This indicated that the site remains essentially unchanged from 1985 when mass grading was performed. SOUTHERN CALIFORNIA SOIL AND TESTING,N C . SCS&T 8921180 November 27, 1989 Page 2 PROJECT DESCRIPTION It is our understanding that the site will be developed to receive a shopping center. The proposed structures will be one and/or two stories high and of wood-frame construction. Shallow foundations and conventional slab-on-grade floor systems are anticipated. Most of the proposed grading will consist of cuts and fills less than five feet deep. In addition, grading associated with the construction of proposed cribwalls will consist of cuts and fills up to ten feet and 18 feet deep, respectively. CONCLUSIONS AND RECOMMENDATIONS The following updated recommendations reflect information available in our files regarding the soil conditions at the site. These recommendations assume a nondetrimentally expansive soil condition within four feet from existing grade. This should be confirmed during grading operations. Furthermore, the existing slopes along Mission Estancia and Rancho Santa Fe Road consist of buttress fills. The impact of proposed cribwalls to be constructed into the slopes should be evaluated. GRADING SITE PREPARATION: Site preparation should begin with the removal from the site of any deleterious matter and vegetation. Existing surface soils should be scarified to a depth of 12 inches, moisture conditioned and compacted to at least 90 percent as determined in accordance with ASTM D1557-78, Method A or C. Fill deposits may then be placed in thin compacted layers. SEU3CT GRADING: It is recommended that expansive soils (expansion index exceeding 50) not be placed within a distance of four feet and two feet from finish pad grade in proposed building and parking areas, respectively. In addition expansive soils should not be placed within a distance of ten feet from the face of fill slopes. SCS&T 8921180 November 27, 1989 Page 3 SURFACE DRMNBCE: It is recommended that all surface drainage be directed away from the proposed structures and the top of slopes. Ponding of water should not be allowed adjacent to the foundation. EAFOHWORK: All earthwork and grading contemplated for site preparation should be accomplished in accordance with the attached Recommended Grading Specifications and Special Provisions. All special site preparation recommendations presented in the sections above will supersede those in the standard Recommended Grading Specifications. All embankments, structural fill and fill should be compacted to at least 90% relative compaction at or slightly over optimum moisture content. Utility trench backfill within five feet of the proposed structures and beneath asphalt pavements should be compacted to minimum of 90% of its maximum dry density. The upper twelve inches of subgrade beneath paved areas should be compacted to 95% of its maximum dry density. This compaction should be obtained by the paving contractor just prior to placing the aggregate base material and should not be part of the mass grading requirements. The maximum dry density of each soil type should be determined in accordance with A.S.T.M. Test Method D-1557-78, MBthod A or C. SLOPE STABILITY Although no major slopes are proposed it is our opinion that cut and fill slopes constructed at a 2:1 (horizontal to vertical) inclination, will possess and adequate factor-of-safety with respect to deep seated rotational failure to a height of at least 20 feet. FOUNDATICNS GENERAL: Conventional shallow footings are recommended for the support of the proposed structures. These footings should be founded at least 12 inches and 18 inches below lowest adjacent finish pad grade for single and two-story structures, respectively. The minimum width for continuous and isolated footings should be 12 inches and 24 inches, respectively. Such footings may be designed for an allowable soil bearing pressure of 2,000 psf. The bearing pressure may be increased by one-third when considering SCS&T 8921180 November 27, 1989 Page 4 wind and/or seismic loading. A minimum setback of seven feet should be observed between footings and the face of slopes. Retaining wall footings in similar conditions should be evaluated by this office. REINFORCEMENT: It is recommended that minimum reinforcement for shallow continuous footings consist of at least two continuous No. 5 reinforcing bars, one located near the top of the footings and two near the bottom. This reinforcement is based on soil characteristics and is not intended to be in lieu of reinforcement necessary to satisfy structural considerations. INTERIOR CGNJKbTLU SUVBS-QH-GRADB: Concrete slabs-on-grade should have a thickness of four inches and be reinforced with No. 3 reinforcing bars placed at 24 inches on center each way. A 6"x6"-W2.9xW2.9 welded wire mesh may be used in lieu of the rebar. The reinforcement should be placed near the middle of the slab. A four-inch-thick layer of clean, coarse sand or crushed rock should be placed under the slab. This layer should consist of material having 100 percent passing the one-half-inch screen, no more than ten percent passing sieve #100 and no more than five percent passing sieve #200. Where moisture-sensitive floor coverings are planned, the sand or rock should be overlain by a visqueen moisture barrier. A two-inch-thick layer of silty sand should be provided above the visqueen to allow proper concrete curing. EXTERIOR SUfflS-CN-GZWDE: Exterior slabs should have a minimnn thickness of four inches. Walks or slabs five feet in width should be reinforced with 6"x6"-W1.4xW1.4 (6"x6"-10/10) welded wire rresh and provided with weakened plane joints. Any slabs between five and ten feet should be provided with longitudinal weakened plane joints at the center lines. Slabs exceeding ten feet in width should be provided with a weakened plane joint located three feet inside the exterior perimeter as indicated on attached Plate Number 1. Both traverse and longitudinal weakened plane joints should be constructed as detailed in Plate Number 1. Exterior slabs adjacent to doors and garage openings should be connected to the footings by dowels consisting of No. 3 reinforcing bars placed at 24-inch intervals extending 18 inches into the footing and the slab. SCS&T 8921180 November 27, 1989 Page 5 SETTLEMENT CHBRflCIERISincSi The anticipated total and/or differential settlements for the proposed structure may be considered to be within tolerable limits provided the recontnendations presented in this report are followed. It should be recognized that minor hairline cracks on concrete due to shrinkage of construction materials or redistribution of stresses are normal and may be anticipated. EAKIH RETAINING WALLS PASSIVE PRESSURE: The passive pressure for the prevailing soil conditions may be considered to be 400 pounds per square foot per foot of depth. This pressure may be increased one-third for seismic loading. The coefficient of friction for concrete to soil may be assumed to be 0.35 for the resistance to lateral movement. When combining frictional and passive resistance, the former should be reduced by one-third. The upper 12 inches of exterior retaining wall footings should not be included in passive pressures calculations. ACTIVE PRESSURE: The active soil pressure for the design of unrestrained earth retaining structures with level backfills may be assumed to be equivalent to the pressure of a fluid weighing 32 pounds per cubic foot. For a 2:1 (horizontal to vertical) sloping backfill 15 pcf should be added. These pressures do not consider any other surcharge. If any are anticipated, this office should be contacted for the necessary increase in soil pressure. This value assumes a drained backfill condition. Waterproofing details should be provided by the project architect. A wall drainage detail is provided on the attached Plate Number 2. BBCKFUi: All backfill soils should be contacted to at least 90% relative compaction. Expansive or clayey soils should not be used for backfill material. The wall should not be backfilled until the masonry has reached an adequate strength. FACTOR OF SAFETY: The above values, with the exception of the allowable soil friction coefficient do not include a factor of safety. Appropriate factors of safety should be incorporated into the design to prevent the walls from overturning and sliding. SCS&T 8921180 November 27, 1989 Page 6 CRIBWMiS: The aforementioned design values may be utilized for critwall design. A bearing capacity of 3000 psf may be utilized for cribwalls founded at least 12 inches into compacted fill or firm natural ground. UHTEATICNS The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration locations and the assumption that the soil conditions do not deviate appreciably from those encountered. It should be recognized that the performance of the foundations and/or cut and fill slopes may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the soils engineer so that he may make modifications if necessary. In addition, this office should be advised of any changes in the project scope or proposed site grading so that it may be determined if the reconmendations contained herein are appropriate. This should be verified in writing or modified by a written addendum. If you have any questions after reviewing the findings and recommendations contained in the attached report, please do not hesitate to contact this office. This opportunity to be of professional service is sincerely appreciated. Respectfully submitted, 3RN CALIFORNIA SOIL STING, INC, Daniel B. fidler, R.C.E. #36037 DEAtmw cc: (3) Submitted (3) Rick Engineering Company TRANSVERSE WEAKENED PLANE JOINTS 6* ON CENTER (MAXIMUM) WEAKENED PLANE JOINTS 10' SLABS IN EXCESS OF 10 FEET IN WIDTH w , W/2t ^^ « X W/2 ^ 1 5'-lO' SLABS' 6 TO 10 FEET IN WIDTH PLAN NO SCALE TOOLED JOINT 1-1/4' T/2 •3 I *5 REBARS AT 18 ON CENTER EACH WAY WEAKENED PLANE JOINT DETAIL NO SCALE ylgXs SOUTHERN CALIFORNIA N^^ SOIL 4 TESTING. INC. TIENDA DE LA ESQUINA BYi - DBA JOB NUMBER: 892 11 80 DATE: -11-27-89 PLATE NO. 1 WATERPROOF BACK OF WALL PER ARCHITECTS SPECIFICATIONS 3/4 INCH CRUSHED ROCK OR MARIDRAINSOOO OR EQUIVALENT QEOFABRIC BETWEEN ROCK AND SOIL 4" DIAMETER PERFORATED PIPE HOUSE ON GRADE SLAB HOUSE RETAINING WALL SUBDRAIN DETAIL NO SCALE ./V SOUTHERN CALIFORNIA <^"X SOIL A TESTING, INC. TIENDA DE LA ESQUINA BY: DBA JOB NUMBER: 8921180 DATE: 11-27-89 PLATE NO. 2 TIENDA DE LA ESQUINA, RANCK) SANTA FE ROAD AND MISSION ESTANCIA, CARLSBAD RBCCMMENDED GRADING SPECIFICATIONS - (SNERAL PROVISICNS GENERAL INTENT The intent of these specifications is to establish procedures for clearing, contacting natural ground, preparing areas to be filled, and placing and compacting fill soils to the lines and grades shown on the accepted plans. The recomnendations contained in the preliminary gee-technical investigation report and/or the attached Special Provisions are a part of the Recommended Grading Specifications and shall supersede the provisions contained hereinafter in the case of conflict. These specifications shall only be used in conjunction with the geotechnical report for which they are a part. No deviation from these specifications will be allowed, except where specified in the geotechnical report or in other written communication signed by the Geotechnical Engineer. OBSERVATION AND TESTING Southern California Soil and Testing, Inc., shall be retained as the Geotechnical Engineer to observe and test the earthwork in accordance with these specifications. It will be necessary that the Geotechnical Engineer or his representative provide adequate observation so that he may provide his opinion as to whether or not the work was accomplished as specified. It shall be the responsibility of the contractor to assist the Geotechnical Engineer and to keep him appraised of work schedules, changes and new information and data so that he may provide these opinions. In the event that any unusual conditions not covered by the special provisions or preliminary geotechnical report are encountered during the grading operations, the Geotechnical Engineer shall be contacted for further recommendations. (R-9/89) SCS&T 8921180 November 21, 1989 Appendix, Page 2 If, in the opinion of the Geotechnical Engineer, substandard conditions are encountered, such as questionable or unsuitable soil, unacceptable moisture content, inadequate compaction, adverse weather, etc.; construction should be stopped until the conditions are remedied or corrected or he shall recommend rejection of this work. Tests used to determine the degree of compaction should be performed in accordance with the following American Society for Testing and Materials test methods: Maximum Density & Optimum Moisture Content - ASTM D-1557-78. Density of Soil In-Place - ASTM D-1556-64 or ASTM D-2922. All densities shall be expressed in terms of Relative Compaction as determined by the foregoing ASTM testing procedures. PREPARATION OF AREAS TO RECEIVE FIU. All vegetation, brush and debris derived from clearing operations shall be removed, and legally disposed of. All areas disturbed by site grading should be left in a neat and finished appearance, free from unsightly debris. After clearing or benching the natural ground, the areas to be filled shall be scarified to a depth of 6 inches, brought to the proper moisture content, compacted and tested for the specified minimum degree of compaction. All loose soils in excess of 6 inches thick should be removed to firm natural ground which is defined as natural soils which possesses an in-situ density of at least 90% of its maximum dry density. (R-9/89) SCS&T 8921180 November 21, 1989 Appendix, Page 3 When the slope of the natural ground receiving fill exceeds 20% (5 horizontal units to 1 vertical unit), the original ground shall be stepped or benched. Benches shall be cut to a firm competent formational soils. The lower bench shall be at least 10 feet wide or 1-1/2 times the the equipment width whichever is greater and shall be sloped back into the hillside at a gradient of not less than two (2) percent. All other benches should be at least 6 feet wide. The horizontal portion of each bench shall be compacted prior to receiving fill as specified herein for compacted natural ground. Ground slopes flatter than 20% shall be benched when considered necessary by the Geotechnical Engineer. Any abandoned buried structures encountered during grading operations must be totally removed. All underground utilities to be abandoned beneath any proposed structure should be removed from within 10 feet of the structure and properly capped off. The resulting depressions from the above described procedures should be backfilled with acceptable soil that is compacted to the requirements of the Geotechnical Engineer. This includes, but is not limited to, septic tanks, fuel tanks, sewer lines or leach lines, storm drains and water lines. Any buried structures or utilities not to be abandoned should be brought to the attention of the Geotechnical Engineer so that he may determine if any special recommendation will be necessary. All water wells which will be abandoned should be backfilled and capped in accordance to the requirements set forth by the Geotechnical Engineer. The top of the cap should be at least 4 feet below finish grade or 3 feet below the bottom of footing whichever is greater. The type of cap will depend on the diameter of the well and should be determined by the Geotechnical Engineer and/or a qualified Structural Engineer. (R-9/89) SCS&T 8921180 November 27, 1989 Appendix, Page 4 FILL MB3ERIAL Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of vegetable matter and other deleterious substances. Granular soil shall contain sufficient fine material to fill the voids. The definition and disposition of oversized rocks and expansive or detrimental soils are covered in the geotechnical report or Special Provisions. Expansive soils, soils of poor gradation, or soils with low strength characteristics may be thoroughly mixed with other soils to provide satisfactory fill material, but only with the explicit consent of the Geotechnical Engineer. Any import material shall be approved by the Geotechnical Engineer before being brought to the site. PIJCING AND OCMPJCTION OF FILL Approved fill material shall be placed in areas prepared to receive fill in layers not to exceed 6 inches in compacted thickness. Each layer shall have a uniform moisture content in the range that will allow the compaction effort to be efficiently applied to achieve the specified degree of compaction. Each layer shall be uniformly compacted to the specified minimum degree of compaction with equipment of adequate size to economically compact the layer. Compaction equipment should either be specifically designed for soil compaction or of proven reliability. The minimum degree of compaction to be achieved is specified in either the Special Provisions or the recommendations contained in the preliminary geotechnical investigation report. When the structural fill material includes rocks, no rocks will be allowed to nest and all voids must be carefully filled with soil such that the minimum degree of compaction recommended in the Special Provisions is achieved. The maximum size and spacing of rock permitted in structural fills and in non-structural fills is discussed in the geotechnical report, when applicable. (R-9/89) SCS&T 8921180 November 27, 1989 Appendix, Page 5 Field observation and compaction tests to estimate the degree of compaction of the fill will be taken by the Geotechnical Engineer or his representative. The location and frequency of the tests shall be at the Geotechnical Engineer's discretion. When the compaction test indicates that a particular layer is at less than the required degree of compaction, the layer shall be reworked to the satisfaction of the Geotechnical Engineer and until the desired relative compaction has been obtained. Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction by sheepsfoot rollers shall be at vertical intervals of not greater than four feet. In addition, fill slopes at a ratio of two horizontal to one vertical or flatter, should be trackrolled. Steeper fill slopes shall be over-built and cut-back to finish contours after the slope has been constructed. Slope compaction operations shall result in all fill material six or more inches inward from the finished face of the slope having a relative compaction of at least 90% of maximum dry density or the degree of compaction specified in the Special Provisions section of this specification. The compaction operation on the slopes shall be continued until the Geotechnical Engineer is of the opinion that the slopes will be stable surficially stable. Density tests in the slopes will be made by the Geotechnical Engineer during construction of the slopes to determine if the required compaction is being achieved. Where failing tests occur or other field problems arise, the Contractor will be notified that day of such conditions by written communication from the Geotechnical Engineer or his representative in the form of a daily field report. If the method of achieving the required slope compaction selected by the Contractor fails to produce the necessary results, the Contractor shall rework or rebuild such slopes until the required degree of compaction is obtained, at no cost to the Owner or Geotechnical Engineer. (R-9/89) SCS&T 8921180 November 21, 1989 Appendix, Page 6 CUT SCOPES The Engineering Geologist shall inspect cut slopes excavated in rock or lithified formational material during the grading operations at intervals determined at his discretion. If any conditions not anticipated in the preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions shall be analyzed by the Engineering Geologist and Soil Engineer to determine if mitigating measures are necessary. Unless otherwise specified in the geotechnical report, no cut slopes shall be excavated higher or steeper than that allowed by the ordinances of the controlling governmental agency. ENGINEERING OBSERVATICN Field observation by the Geotechnical Engineer or his representative shall be made during the filling and compacting operations so that he can express his opinion regarding the conformance of the grading with acceptable standards of practice. Neither the presence of the Geotechnical Engineer or his representative or the observation and testing shall not release the Grading Contractor from his duty to compact all fill material to the specified degree of compaction. SEflSCN LIMITS Fill shall not be placed during unfavorable weather conditions. When work is interrupted by heavy rain, filling operations shall not be resumed until the proper moisture content and density of the fill materials can be achieved. Damaged site conditions resulting from weather or acts of God shall be repaired before acceptance of work. (R-9/89) SCS&T 8921180 November 27, 1989 Appendix, Page 7 REOCMMMJED GRADING SPECIFICATIONS - SPECIAL PROVISIONS RELATIVE COMPACTION: The minirann degree of conpaction to be obtained in compacted natural ground, compacted fill, and compacted backfill shall be at least 90 percent. For street and parking lot subgrade, the upper six inches should be compacted to at least 95% relative conpaction. EXPANSIVE SOUS: Detrimentally expansive soil is defined as clayey soil which has an expansion index of 50 or greater when tested in accordance with the Uniform Building Code Standard 29-C. OVERSIZED MATERIAL: Oversized fill material is generally defined herein as rocks or lumps of soil over 6 inches in diameter. Oversize materials should not be placed in fill unless recommendations of placement of such material is provided by the geotechnical engineer. At least 40 percent of the fill soils shall pass through a No. 4 U.S. Standard Sieve. TRANSmCN DJrS: Where transitions between cut and fill occur within the proposed building pad, the cut portion should be undercut a minimum of one foot below the base of the proposed footings and recompacted as structural backfill. In certain cases that would be addressed in the geotechnical report, special footing reinforcement or a combination of special footing reinforcement and undercutting may be required. (R-9/89)