Loading...
HomeMy WebLinkAboutTract Map 3883 Lot 198 Subsurface Soils & Geological Investigation " ,r< ,; r . . . . RECEIVED S ptember ~~do~ 2002 v .0. OO~ OF TEMECULA ENGINEERING DEPARTMENT Mr. Brian Clark 30000 Via Norte T emecula, CA wac BBDTBCRNICAL -INC. I"iZ. ~:;r, u, \"18 Subject: Subsurface Soils Engineering and Engineering Geologic Investigation for Proposed Residential GradinglResidential Building Construction and Foundation Evaluation for Property Known as Lot 198, Tract 3883, City of Temecula, County of Riverside, California A.P.N.919-092-007 , Gentlemen: , Presented herein, per your request, are the results of our preliminary subsurface soils engineering I feasibility investigation for proposed residential development for Lot 198, Tract 3883, City of I Temecula, County of Riverside, California (see Figure 1, site vicinity map). , The results of our investigation indicate that the soils underlying the proposed building and grading areas are comprised of colluvial soils consisting of silty very fme to medium-grained sand in aloose to medium dense state in turn, underlain by bedrock comprised of clayey silty very fme to medium-grained sandstone. Based upon information supplied to this office it is proposed to grade the subject property in preparation for residential building construction. At the time of this investigation, a Grading Plan was available for review, plan was utilized as a base map for field i review and plotting of exploratory borings (plate 1). Cut ,and fill grading is proposed for pad development on the order of approximately 2-8 ~ feet. Fill slopes at 2: 1 gradient are proposed along southern and eastern pad limits. Cut slope at 2: I , gradient, to heights up to, approximately 19 feet is proposed northwestern property corner. It is proposed to construct conventional spread footings for slab-on-grade residential building. It is our opinion that the site should be considered suitable for the plarmed development, provided the recommendations presented herein are incorporated into design and in construction, Adequately constructed spread footings founded into competent, field approved dense compacted fill are expected to provide necessary support for the planned residential structure. This report has been prepared in accordance with the generally accepted engineering standards I considered necessary for the proposed development. . '\ ,- ,0 ~ E) r :s; :I> ~ ~ ,iT! c;} :3 11l g JIi <0 '" '" <0 ,.... 1:1 ,0> l'lil Ilo G) 5: '<0 I~ ':I> i", . . e1998 Thomas Bras. Maos c... CD (II CD )> III o o ..:~'::-:". .-,. le.': "-: 311'(.) -.', - Site Vicinity Map Z- Figure I '\ '1 I ,'~ f r . . AP.N. 919-092..Q07; Lot 198, Tract No. 3883 W.O, 00599 I 1.0 In trod u ction This report presents the results of our preliminary subsurface soils engineering feasibility ! investigation for proposed residential development for Lot 198, Tract 3883, City of Temecula, County of Riverside, California (see Figure 1, site vicinity map). i The purpose of this evaluation is to determine the nature and engineering properties of the i subsurface soils, engineering geologic site evaluation and to provide necessary geotechnical I recommendations for fOundation design, site grading, utility trench backfill, and field review during construction. Our evaluation included field review, subsurface exploration, soil sampling, laboratory testing, engineering analyses, review of referenced published information and preparation ofthis report. The recommendations contained herein reflect our professional opinions for the subsurface soil conditions encountered during our field investigation. 1.1 Proposed Development Based upon information supplied to this office it is proposed to grade the subject property in I preparation for residential building construction. A grading plan, prepared at a scale of one-inch equals 20 was reviewed. Plan was used as a base map for this report and is attached as Plate I. , Access to subject property is off Via Norte. It is proposed the grade the subject lot to produce i two' buildings pads, residential and barn. Pads are to be developed by cut and fill grading techniques producing a 2:1 cut slope-, approximately 19 feet in height (northwestern corner area o~pad) and fill slopes at 2:1 gradient to heights up to 8 ~ feet. Access to the developed property I is via a graded driveway emanating off Via Norte. Property is to be served by a seepage pit , sewage system. Conventional spread footings are proposed for the building pad areas. Developed lot is to be served by leach line system. It is our opinion that the site should be considered suitable for the planned development, provided the recommendations presented herein are incorporated into design and in construction. Adequately constructed spread footings founded into competent, field approved compacted fill materials are expected to provide necessary support for the plarmed I residential structures. 1.2 ,site Description The subject property is located on the southern side of Via Norte, Temecula, California and is bounded by Via Norte to ,the north (with residential property on the north side of Via Norte), residential property to the west, open space to the east and south. The subject property is lower in: elevation than Via Norte and is comprised of gentle in gradient, hillside terrain (approximately 4: I to 5: I in gradient, sloping from north to south). The property is mantled with native grass and I weeds. Drainage is via sheet flow to the south. An' existing 2: 1 fill slope is located along the I northern central property1boundary, placed during grading of Via Norte. i PAGE 3 WAC Geotechnical, Inc. ~ . . . A.P,N, 919-092.007; Lot 198, Tract No, 3883 W,O. 00599 2.1I -Scope or Work Geotechnical investigation for the subject site included subsurface exploration utilizing a truck mounted B-34, 8-inch auger-drill rig, soil sampling, laboratory testing, engineering analyses and preparation of this report. In general, scope of work included the following tasks: o Two exploratory auger borings were excavated, advanced to a maximum depth of 15.0 feet below the existing grade (see Plate I & Boring Logs, Appendix Section). During exploration, encountered subsurface soils were logged based upon visual and tactile ,methods with bulk samples obtained at subsurface zones at or near programmed pad grade. Collected samples were transferred to our laboratory for testing and analyses. Descriptions of encountered subsurface soils are provided on the Boring Logs in Appendix Section. Approximate locations of test borings are shown on Plate 1. o Laboratory testing conducted on select bulk and remolded samples were programmed according to the project requirements. The laboratory testing included determinations of Moisture Content, Maximum Dry Density and Optimum Moisture content, soil Shear Strength, Consolidation characteristics (based upon remolded samples) under anticipated structural loadings and expansive index. Descriptions of the test procedures used and test results are provided in Appendix Section. o Based upon obtained data resulting from our field investigation, laboratory testing and engineering analyses, this report presents this firms recommendations for foundation design, site preparation, grading and inspections necessary during site construction. I 3.0 'Subsurface Conditions , Our evaluation of the site subsoil conditions are based upon subsurface soil exploration and noted laboratory testing. For the depths explored, proposed pad areas, contains loose porous colluvial soils to an approximate depth of3.0 ~ feet consisting of silty very fine to medium-grained sand. Underlying i bedrock soils are comprised of dense, clayey silty fine to medium-grained sandstone and siltstone. Based upon our field investigation, soil sampling and subsequent laboratory and engineering analyses, the following characteristics for the site soils are observed: i In,genera1, the upper 0 to 3.0.:t feet of the site soils comprising the structural pad areas are loose and compressible. These soils, will require removal to competent bearing subgrade (bedrock) followed by void replacement with compacted fill placement for slab on grade construction or for foundations straddling a cut/fill transition line. In-place and approved competent dense bedrock PAGE 4 WAC Geotechnical, Inc. -\ . I I . . AP,N. 919~92~07; Lot 198, Tract No, 3883 W.O. 00599 materials should be considered to be suitable for structural fill support for planned residential construction. At time of construction, actual field exposures will dictate site suitability based upon field review by the project engineering geologist or soils engineering consultant. Fill slopes i will require construction of fill keyway. Keyways should be a minimum of 15 feet or 1/2 the slope height, plus benches (if any) whichever is greater. Keyway should have a positive tilt with the heel founded I-foot deeper than toe. Laboratory shear tests cQnducted on the upper bulk samples remolded to 90 percent of the laboratory determined Maximum Dry Density indicate moderate shear strengths under increased moisture conditions. Results of the laboratory shear tests are provided in Plate A-I in Appendix , Section. , Consolidation tests conducted on remolded samples at depths of 0-5 feet, indicate low potential for compressibility under anticipated structural loadings. Results of the laboratory determined seils consolidation potential are shown on Plate B-1, Appendix Section. i Site soils are classified as clayey silty fine to coarse-grained sand. Site soils are considered to have very low expansive potential with an expansive index ofE.I. of 19. 3;2 i Excavatibility Considering the state of the non-lithified colluvial soil and underlying sandstone/siltstone bedrock materials below current surface grade, it is our opinion that grading and excavation required for I the project may be ,accomplished using conventional construction equipment to proposed design grades and recommended removal depths. Our subsurface drilling program drilled to depths up to 15 feet. 3J3 Groundwater' Encountered subsoils at depths of 15.0 feet were in a moist state. Groundwater was not encountered during our subsurface drilling excavation to depths up to 15.0 feet. Proposed censtruction area i~ on a gentle slope ridge and flank underlain by dense sandstone/siltstone bedrock materiaIs, Ground water is not expected to be a problem during site grading to I anticipated removal depths. 3)4 'Subsurface Variations Based upon the results of our subsurface investigation and on past experience, it is the opinion of this 'firm that variations in the continuity, depths of subsoil deposits may be expected. Due to the nature and characteristics of the soils underlying the subject site, care should be exercised in interpolating or extrapolating the conditions and prope-rties of the subsoils beyond the boring locations. PAGE 5 WAC Geotechnical, Inc. '5 .', . . AP.N. 919-092..007; Lot 198, Tract No. 3883 W,O, 00599 3.5 Geology The subject property is located within a Pleistocene non-marine terrane. Deposits on-site are classified as colluvial deposits comprised of silty very fine to medium-grained sand. Underlying bedrock soils are compri~d of dense, clayey silty fine to medium-grained sandstone and siltstone. i The natural slopes in and around the property are very shallow gradient (approximately 4-5:1) and i oflow relief(approximately 20 feet) and are not affected by known landsliding. Large natural bodies of water do not exist on the subject property or adjacent to the subject I property. Therefore, the ~ubject property is not threatened by seismic induced tsunami or seiching i phenomenon. I Design engineer should review subject property for drainage from off site property and design , grading appropriately for subject development. 3.6 AlquistlPriolo Special Studies Zones I The subject property is not located in a state mandated Special Studies Zone for Active faulting. ,3.7 Potential Seismic Hazards Seismic Design Parameters Based UDon 1997 UBC The seismic design fault for the subject property is the Elsinore Fault, Glen Ivy segment which is , located within 5.0 kilometers to the subject property. The fault type is "B." The maximum I magnitude is noted by the UBC as 6.8. The slip rate is 5 mmlyr. The Near-Source Factor N., is I noted as 1.0; the Near-Source Factor Nv is noted as 1.2. I The colluvial soil and sandstone/siltstone bedrock underlying the subject site, is assigned the Soil I Type Profile SD, The Seismic Zone Factor is 0.40. The Seismic Coefficient, C., is noted as 0.44Na; the Seismic Coefficient, Cv, is noted as 0.64Nv. 3.8 Liquefaction Liquefaction is caused by the build up of excess hydrostatic pressure in saturated cohesionless ! soils due to cyclic stress generated by ground shaking during an earthquake. The significant i factors on which liquefaction potential of a soil deposit depends, among others include, soil type, relative soil density, intensity of earthquake, duration of ground shaking, and depth of ground water. Ground water was not encountered in our subsurface exploration program and is not considered , to'be within 15 feet of the surface grade. Underlying in-place bedrock materials consist of dense I sandstone and siltstone. Based upon available information from this investigation, it is the opinion i of this firm that the potential for liquefaction is minimal for the subject property. PAGE 6 WAC Geotechnical, Inc. '" ~- i . . A.P.N. 919-092-007; Lot 198, Tl8ctNo. 3883 W.O, 00599 I 4.0 Evaluations and Recommendations 411 i General Evaluations Based on this firm's field investigation, laboratory testing and subsequent engineering analysis, it is our opinion that, from a geotechnical viewpoint, the site should be considered suitable for the planned development, provided the recommendations presented herein, are incorporated into final , design and in construction. Site preparation and grading should be performed in accordance with the enclosed grading section i recommendations of this ,report, except as modified in the main text and with the applicable portions of Appendix Chapter 33 of the current UBC or applicable local ordinance. i Structural design considerations should include the probability of moderate to high peak ground accelerations from relatively active nearby earthquake faults as noted in Section 3.7. I 411.1 SubGrade Preparations for Structural Fill Area Project soils engineering consultant and/or engineering geologist should review removal of unsuitable soil materials to a minimum depth on-feet and a minimum of 5-feet outside building footprint to competent structural earth materials, as field approved by the project engineering geologist. Exposed earth materials shall be a minimum of90% relative dry density as compared to the prevailing maximum dry density for the site soils and verified by testing (ASTM D1557-9l and D 2922-96). Fill should be placed under the observation and testing of the project soils e~gineering consultant. Building structural areas that fall within a cut/fill transition line should be i overexcavated a minimum of3.0 feet in depth to 5-feet outside building footprint to insure a uniform base for compacted fill placement. Following excavation, the bottom exposure should be further scarified to'6-inches, moisture conditioned and recompacted to 90% prior to new fill placement. Fill blanket placed should be compacted to at least 90 percent of the Maximum Dry I Density as determined by the laboratory standard ASTM Dl557-91 test standard. In-place and I approved competent dense bedrock materials should be considered to be suitable for structural fill support for planned residential construction. At time of construction, actual field exposures will dictate site suitability based upon field review by the project engineering geologist or soils i engineering consultant. Fill slopes will require construction of fill keyway. Keyways should be a I minimum of 15 feet or 1/2 the slope height, plus benches (if any) whichever is greater. Keyway should have a positive tilt with the heel founded I-foot deeper than toe. The need for backdrains I will be evaluated in the field by the project engineering geologist/soils engineering consultant. I General earthwork recommendations are enclosed with this report. Recommendations for field placement offill is to take the form of thin layers of soil (not to I exceed 6 inches) moisture conditioned and compacted by sheepsfoot roller (or other approved compaction equipment) with 90% relative compaction as compared to the Maximum Density/Optimum Moisture value of the soil. Fill should be placed under the observation and , testing of the project soils engineering consultant and as noted below in grading section. PAGE 7 WAC Geotechnical, Inc. "\ . . A.PN, 919-092-007; Lot 193, Tract No, 3883 W.O. 00599 GRADING I. 2. 3. 4. 5. 6. : PAGE 8 After approval of overexcavation and prior to placement of any compacted fill, the materials, the exposed stripped ground surface and bottoms of all excavated areas which are to receive fill should be scarified to a minimum depth 0 f 6 inches, moisture conditioned to slightly above optimum moisture content and then rolled and compacted to 90 percent of the laboratory maximum density as determined in accordance with ASTM: Test Method D-1557-91. Unless otherwise specified, all references to compaction within this report relate to that standard. Approved on-site earth materials or imported soils should then be spread in thin lifts, watered to slightly above optimum moisture content and then rolled and compacted to a minimum of90 percent of the applicable laboratory maximum density. Each lift should be treated in a like manner until the desired grade is achieved. Import soils, if required, should consist of clean, non-expansive compactible materials similar to on-site soils and should be free of trash, debris or other objectionable materials. Plans and specifications should indicate that the grading contractor shall notify the project soils engineer not less than 72 hours in advance of the location of any soils proposed for import. Each proposed import source shall be sampled, tested andappr(Jved prior to delivery of soils for use on the site. All of the above overexcavation and earthwork should be performed under the observation and testing of the project soils engineering consultant and engineering geologist., All fill should be tested at the time of placement to ascertain that the required compaction is achieved. The minimum basis oftesting should be one (1) testper two (2) feet offill depth or per each 500 cubic yards offill placed. Subdrainswill be required in the natural swale areas below engineered fills. The lower portions of the subdrains may require outletting through compacted fill via solid pipe. A concrete headwall will be required at the fill/bedrock contact. Backdrainage devices with lateral outlets will be required for stabilization fills over 10 feet in vertical height or as field conditions dictate. The installation of the backdrainage systems should be observed by the soils engineer and/or engineering geologist. WAC Geotechnical, Inc. ~ ,.------;--- . . I AP.N. 919-092-007; Lot 198, Tract No. 3883 W,O. 00599 ,8. 9. I PAGE 9 7. The cut portion of the building pads traversed by cut/fill daylight lines should be overexcavated to a minimum depth of three feet and replaced to design grade with a compacted blanket fill to reduce potential differential settlement effects. Building pads above stabilization fills must also be overexcavated a minimum of three feet ,and capped with a compacted fill blanket to inhibit surface moisture infiltration. Cut pads which may expose fault or shear zones at finish grade should be overexcavated to a minimum depth of four feet and replaced to grade as directed by the soils engineer and/or engineering geologist. Fill,over-cuts are acceptable provided the fill portions are constructed on a keyway founded in firm bedrock. The width of the keyway should be excavated to one-half the slope height or a minimum of 15 feet, which ever is greater. The keyway should slope from toe to heel with a minimum differential of one foot. Where uncertainty relative to the suitability of the cut is present. the cut portion should be,exposed prior to fill placement. Final determination should be made bv the proiect enl!ineerinl! l!eolol!ist. 10. Where th~ natural or existing graded slope is steeper than 5 feet horizontal to foot vertical and where designated by the soils engineer or engineering geologist, compacted fill material should be keyed and benched into bedrock or firm material during grading. Care should be taken to avoid benching above the proposed finished pad surface. 11. In order to minimize surficial slumping on compacted fill slopes, the following grading procedures should be undertaken: a. Compacted fill slopes should be backrolled during placement at intervals not exceeding 4 feet in vertical height. Care should be taken to construct the slopes in a workmanlike manner so that they are positioned at the design orientation and slope ratio. Achieving a uniform slope surface by subsequent thin wedge filling must be avoided. Any add-on correction to a fill slope should be conducted by overfilling the affected area in horizontal, compacted lifts which must be benched into the existing fill prism. The overfill slope may then be trimmed to the design gradient. After completion, the fill slope faces shall be rolled for the entire height with a sheepsfoot roller and the finished with a grid roller. Ifthe desired compaction is not obtained in this manner, a vibratory sheepsfoot roller WAC Geotechnical, Inc. '\ . , . . AP,N, 919-092-007; Lot 198. Tract No, 3883 W.O. 00599 13. 14. I PAGE 10 may be required. To be most effective. this equipment should be anchored and manipulated from a side-boom tractor. In lieu of a grid roller, the slope may be track rolled with a D-8 dozer or equivalent machinery on slopes of2: I or flatter. To obtain the required compaction and appearance ofthe slope face, the soil'moisture should be maintained at or near optimum from the time of mass filling to the completion of grid rolling. b. As an alternative to Item a., fill slopes may be constructed by overfilling a minimum 00 feet, compacting and then trimming back such as to expose the dense .inner core of the slope face, c. The grading contractor should be aware that care must be taken to avoid sloughing ofloose material down the face of the slopes during construction. Fine grading operations should not deposit loose, trimmed soils on any of the finished slope surfaces. These materials should be removed from slope areas. 12. Although oversized rock material was not encountered during our investigation, should oversize boulders be generated during grading, all rock burial must be in accordance with the Grading Code and recommendations from this firm, or be wasted off site. All haul roads, ramp fills, and tailing areas should be removed during and as part of the mass grading operations. Normal earthwork grading schedules are established by the project grading contractor, initially in the bidding and subsequent pre-job planning stages of the project. Delineating and maintaining absolute controls over specific backcut exposure time imposes difficulties in enforcement, particularly when considering the wide variation in size of engineered earthwork stabilization and the range in capabilities of grading contractors participating in the bidding process. In lieu of assigning a specific time limit, this firm would recommend incorporating the following as a note on the grading plan. "It is imperative that the grading schedule be coordinated by the project grading contractor to minimize the unsupported exposure time of temporary backcuts created during landslide or buttress and stabilization fill construction as well as other unsuitable soils removal. Once started, temporary excavations and subsequent fill operations should be maintained to completion without intervening delays imposed by avoidable circumstances. Grading should be planned to avoid WAC Geotechnical, Inc. \0 " . . AP,N, 919-092-007; Lot 198, Tract No, 3883 W.O. 00599 exposure at or near-grade temporary backcut excavation through non-work periods. Where improvements (either on or offsite) may be affected by temporary instability, further restrictions such as slot cutting, extending work day and"or weekend schedules, or other requirements considered critical to serving the specific circumstances may be imposed. " i 4.2 :Spread Foundations ! For adequate support, th~ proposed structures may be constructed on continuous and/or isolated spread footings founded exclusively into field approved compacted fill materials. Conventional shallow fOljIldation system is considered suitable for plarmed residential and ancillary structures. Sulfate content is considered moderate. Type II, IP(MS), IS (MS) cement is recommended. Foundations may be designed based upon the following values: Allowable Bearing: Lateral Bearing: Sliding Coefficient: 1800 Ibs.lsq.ft. 247lbs.lsq.ft. per foot of depth to a maximum of IS00 lbs.lsq.ft. 0.30 The above values may be increased as allowed by Code to resist transient loads such as wind or I seismic. Building code and structural design considerations may govern depth and reinforcement requirements and should be evaluated. 2.' Other Design Recommendations * FOOTING DEPTH Exterior 12-inches below lowest adjacent grade in approved compacted fill for one story and IS-inches below adjacent grade in approved compacted fill for 2-story. Interior 12-inches below lowest adjacent grade in approved compacted fill for one story and IS-inches below adjacent grade in approved compacted fill for 2-story. * FOOTING WIDTH Exterior 12-15 inches minimum for one and 2-story, respectively. Interior 12-15 inches minimum for one and 2-story, respectively. i PAGE 11 WAC Geotechnical, Inc. \\ . . AP,N, 919-{)92-{)07; 1.01198. Tract No, 3883 W.O, 00599 * FOOTING REINFORCEMENT Exterior & Interior All continuous; four No.4 bars, two near the top, two near the bottom for exterior and two No.4 bars, one near the top and one near the bottom for the interior. Concrete Slabs Slab Thickness: 4-inches net, reinforced with 6x6-6/6 WWF, or with #3 rebar at l6-inch o/c, is recommended. Reinforcement should be installed at mid-height in the slab. * Under-Slab Treatment Living Areas 10-mil Visqueen; cover with at least 2 inches of sand. Subgrade soils should be presoaked to contain at least optimum moisture content immediately prior to placing Visqueen and to be verified by the so ils engineering consultant. The sand cover should be moistened prior to placing concrete. Grade Beam A grade beam reinforced continuously with the garage footings should be constructed across all garage entrances, tying together the ends of the garage footings. This grade beam should be embedded at the same depth as the adjacent perimeter footings Garage Slab Optimum moisture content in subgrade soil verified by the soils engineering consultant. * Fireolace Footings - Fireplace footings shall have a minimum embeddment depth of l2-inches measured from the lowest adjacent grade and should be an integral part of the building foundation system. Fireplace slabs shall be treated in the same manner as the living area slabs. , *Prior to pouring footings, soils should be pre-moistened and field approved by the project soils I engineering consultant or his representative. The settlement of properly designed and constructed foundations supported on approved earth materials, carrying maximum anticipated vertical loadings, are expected to be within tolerable limits. Estimated total and differential settlements should be no more than 3/4 and 1/2-inch, respectively for 40 lineal feet. , PAGE 12 WAC Geotechnical, Inc. \'2-- . . A:P,N, 919-092-007; L01198, Tract No, 3883 W.O, 00599 43 Resistance to Lateral Loads Resistance to lateral loads can be restrained by friction acting at the base offoundations and by passive earth pressure, A coefficient of friction of 0.30 may be assumed with the normal dead load ferces for footing established on compacted fill. An allowable passive lateral earth resistance of 247 pounds per square foot per foot of depth, may be assumed for the sides offoundations poured against compacted fill, However, the maximum lateral passive earth pressure is recommended not to exceed 1800 pounds. For design, lateral earth pressures oflocal soils when used as level backfill may be estimated from the following equivalent fluid density: Active: Passive: At Rest: 41 pcf 247 pcf 62 pcf 4~4 Shrinkage and Sul!sidence Based on the results of in-situ density and laboratory resting conducted for the project areas under study, it is our opinion that local site soils when used during grading, may be subjected to a I volume change. Assuming a 90% relative compaction for the compacted fill, and assuming an overexcavation and recompaction of36-inches of the existing surficial soils, such volume change due to shrinkage is expected to be on the order of 10 to 20 percent for colluvial soils. lihe above percentages are for estimation purposes. Actual percentage may vary during I construction, , Bedrock cut materials are expected to bulk on the order of 0-5 percent when placed as compacted I fill. i 4.4.1 Fill Slopes Fill slopes should be keyed with a D'linimnnl of 15 feet in width keyway with the toe and heel founded with a I-foot differential (heel deeper). I 4.4.2 Cut Slope!! All cut slopes should be field evaluated by the project engineering geologist. PAGE 13 WAC Geotechnical, Inc. \:? . . AP.N. 919-092-007; Lot 198, Tract No. 3883 w.o, 00599 , 415 Construction Considerations 415.1 Unsupported Excavation Temporary construction excavations up to a maximum depth of 5 feet may be made without any lateral support. It is recommended that no surcharge loads such as construction equipment, be allowed within a line drawn upward at 45 degree from the toe of excavation. Use of sloping for deep excavations may be,applicable where plan dimensions of the excavation are not constrained i by any existing structure. I 4,5.2 Supported Excavations I It:vertical excavations exceeding 5 feet in depth become warranted, excavation should use shoring I to support side walls. 4.6 ,Site Preparation I Site preparations should include cut subexcavations and placement of soils as engineered fill. Such earth work should be in accordance with the applicable grading recommendations provided in the current UBC and as recommended within this report. This office should be notified 72 hours in advance of importing soils to site for placement as I compacted fill. It will be necessary for the project soils engineering consultant to sample import soils with subsequent laboratory testing to determine suitability of import soils for project I construction. It is strongly recommended that import soils be similar to site soils. The use of clayey soils for pad construction is not recommended. 4.7 'Soil Caving i During excavations for deep utility trenches, 'some' caving may be expected. All temporary excavations should be made at a 2: I (horizontal to vertical) slope ratio or flatter, and/or as per the , construction guidelines provided by CaIOSHA. I 4.8 Retaining Wall , Retaining structures, ifplarmed, should be designed using the following equivalent fluid density: Slope Surface of Equivalent Fluid Density (pel) Retained Material Imported Local (horz. to vert.) Clean Sand Site Soil Level 30 41 2:1 35 62 , PAGE 14 WAC Geotechnical, Inc. '^ . . AP,N, 919-092-007; Lot 198, Tract No, 3883 W,O, 00599 Only free-draining ,granular materials (sand or grave~ SE equal to or greater than 30) as retaining ! wall backfill. Backdrains will be required behind all retaining walls. 4;9 Utility Trench Backfill Utility trench backfill within the structural pad and beyond, should be placed in accordance with the following recommendations: o Exterior trenches along a foundation or a toe of a slope and extending below a 1: 1 imaginary line projected from the outside bottom edge of the footing or toe of the slope, should be compacted to a minimum 90 percent. I 0 All excavated trenches should conform to the requirements and safety as specified by the CalOSHA i 4,10 Pre-Construction Meeting It is recommended that no clearing of the site or any grading operation be performed without i the presence of a representative of this office. An on-site pregrading meeting should be arranged between the soils engineering consultant and the grading contractor prior to any construction. I 4.11 Seasonal Limitations No structural fill shall be placed, spread or rolled during unfavorable weather conditions. Where the work is interrupted by heavy rains, fill operations shall not be resumed until moisture conditions are considered favorable by the soils engineering consultant. , 4112 Planters To minimize potential differential settlement to foundations, planters requiring irrigation should be restricted from use adjacent to footings. If unavoidable, planter boxes with sealed bottoms and ! drain outlets to approved areas away from the foundation, should be constructed. 4.13 Landscape Maint!lnanceJDrainage Only the amount of irrigation necessary to sustain plant life should be provided. Pad drainage should be directed towards streets and to other approved areas awtry from foundations. Slope I areas, when applicable, should be planted with draught resistant vegetation. 4114 Observations and Testing During Construction , Recommendations:provided in this report are based upon the assumption that all foundations will i be placed upon field approved fill materials for structure. Excavated footings should be field ! Pi\GE 15 WAC Geotechnical, Inc. \~ . . AP,N, 919-092-007; Lot 198, TmctNo, 3883 W,O. 00599 reviewed, verified and certified by soils engineering consultant and/or engineering geologist prior to steel and concrete placement to ensure their sufficient embeddment and proper bearing on approved dense compacted fill. Additional field reviews by soils engineering consultant and/or I engineering geologist are recommended to verifY footing excavations being free ofloose and i disturbed material. All structural backfill should be placed and compacted under direct observations and testing by this facility. Excess soils generated from footing excavations should be removed from pad areas and such should not be allowed on subgrades as uncompacted fill for areas programmed to receive concrete slab-on-grade. ! 4;15 Plan Review I The recommendations presented herein should be considered 'preliminary.' It is recommended that "precise grading plans" should be available to this office for review to minimize , misunderstandings between the plans and recommendations presented. Further, excavated , footings should be ,verified as recommended earlier. If during construction, conditions are observed to be different from those as described in this report, revised and/or updated I recommendations will be, required. , PAGE 16 WAC Geotechnical, Inc. \4> . . AP,N, 919-092-007; Lot 198. Tract No, 3883 W.O. 00599 I 5.0 Closure I The conclusions and rec!>mmendations contained herein, are based on the findings and observations made,at the, time of the subsurface investigation. The recommendations presented, should be considered "preliminary" since they are based on soil samples only. If during construction, the subsoil conditions appear to be different from those disclosed during field investigation, this office should be notified to consider any possible need for modification for the geotechnical recommendations provided in this report. ! Recommendations provided are based on the assumptions that structural footings will be established exclusively into field approved compacted fill materials. It is recommended that final "precise grading and foundation plans" should incorporated recommendations made by this office. Site grading must be performed under review by geotechnical representatives of this office. All footing excavations should be field reviewed prior to steel and concrete placement to ensure that foundations are founded into satisfactory soils and I excavations are free ofloose and disturbed materials. A: pregrading meeting between grading contractor and soils engineering consultant should be arranged, preferably at the site, to discuss the grading procedures to be implemented and other ! requirements descnl>ed in this report to be fulfilled. This report has been prepared exclusively for the use of the addressee for the project referenced in context. It shall not be transferred or be used by other parties without written consent by WAC Geotechnical, Inc., We carmot be respollSlble for use of this report by others without I review of the grading op~ration by our personnel. Should the project be delayed beyond one year after the date of this report, the , recommendations presented shall be reviewed to consider any possible change in site conditions. The recommendations pr~sented are based on the assumption that the necessary geotechnical I observations and testing during construction will be performed by a representative of this office. I The field observations are considered a continuation of the geotechnical investigation performed. ! If another firm is retained for geotechnical observations and testing, our professional liability and I responsibility shall be limited to the extent that WAC Geotechnical, Inc. would not be the geotechnical engineering consultant of record. ! PAGE 17 WAC Geotechnical, Inc. \\ AP,N, 919.{)92.{)07; Lot 198, Truet No, 3883 I. Field Exploration , 2. Boring Logs 3, Laboratory Test Programs , 4. Earthwork Specifications 5, 'Professional Limitations 6, References 7. 'Plate 1 PAGE 18 . . W,O. 00599 APPENDIX Section WAC Geotechnical, Inc. ,ro . . AP,N, 919.092.007; Lot 198, TmctNo. 3883 W.O, 00599 Field Exploration The field investigation for the project included site reconnaissance and subsurface exploration using a truck mounted B-34 auger drill rig for subsurface investigation. During the site reconnaissance, the surface conditions were note-d and test boring locations were determined. Soils encountered during exploration were continuously logged and classified by visual observations and tactile methods in accordance with generally accepted field classification. The field descriptions were modified, where appropriate, to reflect laboratory test results. Where appropriate, representative bulk soil samples were obtained. Logs of the exploratory borings are presented in the following summary sheets, that include the description of the subsoil materials encountered. PAGE 19 WAC Geotechnical, Inc. \<\ . A:P.N. 919-092.007; Lot 198, Tract No. 3883 PAGE 20 Boring Logs WAC Geotechnical, Inc. . W.o. 00599 1P . . Borio!! Lo!!s B-34 Auger Drill Rig R-l. Elevation: Elevation as of 8/05/02 , Depth in Feet Description 0.0-3.0' Colluvium Silty fine to medium-grained sand, It. brn, dry to. slightly moist, loose, porous; Soil Classification: SM 3.0-4.8' Bedrock: Slightly clayey silty very fine-grained ~stone, It brn, moist, dense; Soil Classification: SM 4.8" 10.0' silty very fine-grained sandstone, gray tan, moist, very dense; Soil Classification: SM End of boring @ 10.0', no water, no caving B-2. Elevation: Elevation as of 8/05/02 Depth in Feet Description 0.0-3.2 Colluvium Silty very fine, to coarse-grained sand, It. brn, dry to. slightly moist, loose, porous; Soil Classification: SM J.2~5.5' Bedrock: Slightly clayey silty fine-grained sandstone, It tan brn, moist, dense; Soil Classification: SM 5'.5~ 7 .5' Gray siltstone/fine-grained sandstone, moist, dense Soil Classification: SM 7.5-15.0' Lt brn clayey siltstone/fine to medium-grained sandstone, moist, dense to very dense End of boring @ 15.0', no water, no caving WAC Geotechnical, Inc. Sample Bulk @ 0.0-5.0' Sample '/;\ . . AP,N, 919.Q92-Q07; Lot 198. Tract No, 3883 w.o, 00599 Laboratory Test Prtlgrams Laboratory tests were conducted on representative soils for the purpose of classification and for the determination of the physical properties and engineering characteristics. The number and selection ofthe types oftesting for a'given study are based on the geotechnical conditions of the site. A summary of the various laboratory tests performed for the project is presented below. Direct Shear (ASTM D 3080) Data obtained from this test performed at increased moisture conditions on remolded soil samples were used to evaluate soil shear strengths. Samples contained in brass sampler rings, placed directly on test apparatus are sheared 'at a constant strain rate under a normal load, appropriate to represent anticipated structural loadings, Shearing deformations are recorded to failure. Peak and/or residual shear strengths are obtained from the measured shearing load versus deflection curve. Test results, plotted on graphical form, are presented on Plate A-I of this section. Consolidation (ASTM D2435) Data obtained from this test performed on remolded to 90% samples, were used to evaluate the consolidation characteristics offoundation soils under anticipated foundation loading. Preparation for this test involved trimming the sample, placing it in one inch high brass ring, and loading it into the test apparatus which contained porous stones to accommodate drainage during testing, Normal axial loads are applied at a load increment ratio, successive loads being generally twice the preceding. Soil samples are usually under light normal load conditions to accommodate seating of the apparatus. Samples were tested at the field moisture conditions at a predetermined normal load, Potentially moisture sensitive soil typically demonstrate significant volume change with the introduction of free water, The results of the consolidation tests are presented in graphical forms on Plate B-1. Expansion Index ASTM 04829 The site soils are comprised of silty fine to coarse-grained sand and are considered to have very low potential for expansion with an expansion index of (E.\. 19). Laboratorv Test Results Maximum Dry Density/Optimum Moisture Content Relationship SamDle Location Max. Drv Densitv (oct) Ont. Moisture Content (%) B-1, 0-5.0 feet 127.2 9,1 (ASTM 01557-91) PAGE 21 WAC Geotechnical, Inc.a tL- I- o ~ [oj =: -< :l 0' m =: [oj ~ m e: ::0: . [oj to) z -< ?- m 1ii [oj =: t:) z = -< [oj :I: m . . . DIRECT SHEAR TESTS III M = M III - /' =: - III = /'" => o 0.5 1.0 1.5 2.0 NORMAL LOAD - KIPS PER SQUARE FOOT 2.5 SYMBOL LOCATION ... [3-\ DEPTH (ft) 0-5 COHESION FRICTION (psi) (degrees) /10 S I TEST CONDITION ReMoWEt) ~o ~o SATIJIu.r~ tPA-Ail'leo PROJECf NO. OOS9'} WAC Geotechnical, Inc., P.O. BOx 354 PLATE A-I 39210 North Shore Drive, Fawnskin, CA 92333-0354 ~ i I' % o - f- er C - ..J o en Z o (J I~ Iz w (J c:: w a. ,~ " 1, , , , , , , , " , , , , , , , " , , , II' , , , , , , , ; , , '" , ,,, " :'1' '" , '1'1 , , , . CONSOLIDATION TES. \ LOAD IN KIPS PER SOUARE FOOT 1 3 ' 4 6 --- 8 .,10, ;. ~ 5 6 7 8 " " , 9 10 , ,. 11 11 13 " , " 14 " li.11 " , 15 " , , , , " ; , , , , " 'I" , , " ; , , " , , , ", , ' 16 . WATER PERMITTED TO CONTACT SAMPLE WAC GEOTECHNICAL, INC. P.O. Box 354-39210 North Shore Drive Fawnskin, CA 92333-0354 800-288-0707 , , - 10 ."1 " t; it I:! " 'I! 1,1. , " II II" :1.1 , 1'1' " B ~11 o-~' ReMOl..() ;0 qo,-c) PROJECT NO. PLATE ooS'''Iq B-1 'J-,t>... . . EARTHWORK SPECIFICATIONS These specifications present generally accepted standards and minimum earthwork requirements for the development of the project. These speci1ications shaI1 be the project guidelines for earthwork :except where specifically superseded in preliminary geology and soils reports, grading plan review reports or by prevailing grading co~es or ordinances of the controlling agency. L GENERAL A. The contractor shall be responsible for the satisfactory completion. of all earthwork in accordance with the project plans and speci1ications. B. The project Soil Engineer and Eng#leering Geologist, or their representatives, shall provide testing services and geotechnical consultation for,the duration of the project. C. All clearing, grubbing, stripping, and site preparation for the project shall be accomplished by the Contractor to the satisfaction of the Soil Engineer. D, IH$'tllilCciiiiractor'srespoiiSlblliiY-io prepare tJi'e-growidsiirfac-e to receive fills :to the satisfaction of the Soil Engineer and to place, spread, mix, and compact the till in accordance with the job specifications and as required by the i Soil Engineer. The Contractor shall also remove all material considered by the Soil Engineer to be unsuitable for use in the construction of compacted till. E. The <::;ontractor shall have suitable and sufficient equipment in operation to handle the amount offill being placed. When necessary, equipment will be shut down temporarily in order to pennit proper compaction of fills. II. SITE PREPARATION A. iExcessive vegetation and all deleterious material shall be disposed of off-site as required by the Soil Engineer. Existing till, soil, alluvium or rock ~erials determined by the Soil Engineer as being unsuitable for placeQlent in compacted fills shall be removed and wasted from the site. Where applicable, the Contractor mat obtain the approval of the Soil Engineer and the controlling authorities for the project to dispose of the described materials, or a portion thereof, in designated areas on-site. After removals as described above have been accomplished, excavation of earth materials deemed unsuitable in their natural, in-place condition, shall be removed as recommended by the Soil EngineertEngineering Geologist. 1.;5 . . F. Where the moisture content of the fill material is below the limit specified by the Soil Engineer, water shall be added and the materials sha1l be blended until a uniform moisture content, within specified limits. is 1lChieved. Where the moisture content of the fill material is above the limits specified by the Soil Engin~er, the fill materials shall be aerated by discing, blading or other satisfactory methods until the moisture content is within the limits specified. . . , G. Each fill layer shall be compacted to minimum project standards, in ~ompliance with the testing methods specified by the controlling governmental agency and in accordance'with recommendations of the Soil Engineer. H. In the absence of specific recommendations by the Soil Engineer to the ~ontrary, the compaction standard shall be A.S.T.M.: DI557-70. ' L Where a slope receiving fill exceeds a ratio of five-horizontal to one-vertical, _ the fill ,shall be keyed and benched through all unsuitable topsoil, colluvium, alluvium,- or creep 'li1ateiial, mto sound bedrock or firm material, in accordance with the recommendations and approval of the Soil Engineer. 1. Side hill fills shall have a minimum kev width of 15 feei into bedrock or firm materials, unless othenvise specified in the soil report and approved by the Soil Engineer in the field. K. ;rIte Contractor shall be required to maintain the specified minimum relative compaction out to the finish slope face of fill slopes, buttresses, and stabilization fills as directed by the Soil Engineer and/or the governing ~ency for the project. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct compaction of the slope face with suitable equipment, or by any other procedure which produces the designated result. L. Fill-aver-cut slopes shall be properly keyed through topsoil, colluvium or creep material into rock or firm material; and the transition shall be stripped of all soil or unsuitable materials prior to placing fill. :The Cut portion should be made and evaluated by the Engineering ,Geologist prior to placement of fill above. M. Pad areas in natural ground and cut shall be approved by the Soil Engineer. Finished surfaces of these pads may require scarification and recompaction. 1>P . I " . . IV. em: SLOPES A.. The Engineering Geologist shall inspect all art slopes and shall be notified by the ContraCtor when art slopes are started. B. n: during the course of grading, tmforeseen adverse or potentially adverse geologic conditions are encountered. the Engineering Geologist and Soil Engineer shall investigate. anaIyze;'1ud make recommendations to treat these problems. C. Non-erodible interceptor swales shall b~ 'placed at the top of cut slopes that face the same direciion as the prevailing drainage. . . ..' . D. Pnless otherwise sPecified in soil.and' geol~gic reports., no art' slopes shcll be excavated higher or steeper thai1 that allowed by the ordinances of contrOffing governmental agencies. "~E. Drainage terraces shall be constructed in compliance with the ordinances of contrOffing governmental agencies, and/or in accordance with--"h;: recommendations of the Soil Engineer or Engineering Geologist. V. GRADING CONTROL . . A. Fill placement shall be observed'by the Soil Engineer and/or his irepres~ve during the progress of grading. :Field density tests shall be made by the Soil Engineer or his representative .to evaluate the compaction and moisture compliance of each layer of fill. ,Density tests shall be performed at intervaJs not to exceed two feet of fill ,height. Where sheepsfoot roners are used, the soil may be disturbed to a I depth of several inches~ Density cfetenninations shall be taken in the I compacted material below the disturbed surfuce at a depth determined by ! the Soil Engineer or his representative. B. ; Where tests indicate that the density of any layer of fill, or portion thereot: is below the required relative, compaction, or improper moistUre is in i evidence, the particular Jayet or portion shall be reworked until the I required density and/or moisture content has been attained. No additional I fill shall be placed until the last placed lift of fill has been tested and found . to meet the density and moisture requirementS and that lift approved by the Soil Engineer. ' ~'\ . , . ' . . ." '. c. [Where the work is interrupted bY heavy rains, fill operations shaD not be .resumed until field observations and tests by the Soil Engineer indicate, the ,moisture content and density of the fill are within the timits previously ,specified. . D. ,During construction, the Contractor shall properly grade all surlkces to ,maintain good drainage and . prevent ponding of water. The Contractor :shall take remedial measures to control surlkce water and to prevent erosion of graded areas until such time as permanent drainage and erosion ,control measures have been installed. E. ,Observation and testing by the Soil Engmeer shall be conducted during the ,filling and compacting operations in order that he wiD be able tQ state in hjS :opinion all cut and filled areas are graded in accordance with the approved ,specifications. . . F. :After completion of grading and after the Soil Engineer and Engineering :Geologist have finished their observat;ions of !!te work, final reports shall ,be submitted. No further excavation or filling s1uill be Undertaken without ,prior notification of the Soil Engineer and/or Engineering Geologist. VI. SLOPE PROTECTION Al1fini~hed cut and fill slopes shall be planted and/or protected from erosion in accordance with the project specifications and/or as recommended by a landscape architect. 7!b . . A.P,N,385.200-003.3 . . W,Q. 00553 PROFESSIONAL LIMITATIONS Our investigatiOli was performed using the degree of care and skill ordinarily exercised, under similar circumstances by other reputable Soils Engineering Consultants practicing in this general or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advise included in this report. :The investigations are based on soil samples only, consequently the recommendations provided :shall be considered ~preliminary'. The samples taken and used for testing and the observations made are believed representative of site conditions; however, soil and geologic conditions can vary significantly between borings. As in most major projects, conditions revealed by excavations may vary with preliminary fmdings. If this occurs, the changed conditions must be evaluated by the Project Soils Engineering Consultant and designs adjusted as required or alternate design recommended. The report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are brought to the attention of the project architect and engineers. Appropriate recommendations should be incorporated into structural plans. The necessary steps should be taken to see that the contractor and subcontractors carry out such recommendations in field. The findings of this report are valid as of this present date. However, changes in the conditions of a property can occur with the passage of time, whether they due to natural process or the works of man on this or adjacent properties. In addition, cnanges in applicable or appropriate standards may occur from legislation or broadening of knowledge. Accordingly, the findings of this report may be inyalidated wholly or partially by change outside of our control. Therefore, this report is subject to review and should be updated after a period of one year. RECOMMENDED SERVICES . The review of gr~ding, plans and specifications, field observations and testing by the geotechnical : representative is an integral part of the conclusions and recommendations made in this report. If WAC Geotechnical, I~c. is not retained for these services, the Client agrees to assume WAC I Geotechnical, Inc. responsibility for any potential claims that may arise during and after , construction, or during the lifetime use of the structure and its appurtenant. The required tests, 'observations and consultation by the geotechnical consultant during construction includes, but 'not be limited to: la. Continuous observation, geologic mapping and testing during site preparation and grading, and :placement of engineered fill. b. Observation and field review of footing trench prior to steel and concrete placement, C. Consultations as required during construction, or upon your request. PAGE 22 WAC Geotechnical, Inc. 1J\ -- , .-- !oa/,oa 20U' UII;40 r~ IIVII ...... ;... " - .~4:' \ ~ 0.;;. I ~ ,lI- '6'" Kt'" amac. 'BLOCK 1<1:.1 AIN_ WtcLL \...~ '"f0.0' SB-2 AppR"i-,,.,rl,TE t?>.JlJl-f:o L.ocIlTIO/V 10 I \"::: '2,0 0, ^ TC 1