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HomeMy WebLinkAboutRW080308 - SOILS1),w 30t' Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY May 2, 2008 Project No. 9208 8'2-021 Site Address: 23000 Newport Coast Drive To: Marriott Vacation Club International 3130 South Harbor Boulevard, Suite 500 Santa Ana, California 92704 Attention: Mr. Gene Ong Subject: Geotechnical Review of Precise Grading Plan for La Vista Pool Bar, Tract No, 15697, Marriott's N.P.C. Villas, Newport Coast, County of Orange, California Introduction In accordance with your .request, Leighton and Associates, Inc. (Leighton) is pleased to present our geotechnical review of the precise grading plan, for. La Vista Pool Bar located within Marriott's N.P.C. Villas at the Newport Coast, County of Orange, California, The subject of our review i.s the 5-scale Precise Grading Plan prepared by RBF Consulting and received by us on April 24, 2008. This report presents the results of our review along with geotechnical recommendations for the proposed improvements. Scope. of Work Our scope of work has included the following: • Review of existing in-house reports and geology maps pertinent to the site; • Geotechnical review of the precise grading plan with respect to the geotechnical conditions of the site; and • Preparation of this report presenting our findings, conclusions, and .recommendations for design and construction. 17781 Cowan ■ Irvine, CA 92614-600- 949.250,1421 r Fax 949,250.1114 is www,leightongeo.com /, 920882.021 Previous Grading La Vista. pool is located at the southwestern portion of the site for Marriott's N.P.C, Villas and was constructed during Construction Phase 1. Grading and construction of the pool and its vicinity were performed under the observation and testing of Leighton. The proposed pool. bar and its associated improvements will be located in the southern portion of La Vista Pool, Precise Grading Plan Review The precise grading plan was prepared by RJ3F Consulting, dated April 21., 2008, and was received by us on April 24, 2008. The plan is titled "Precise Grading Plan for Building: La Vista Pool Bar of Marriott's Newport Coast Villas, Tract No, 15697". The received plan. consists of 6 sheets and was reviewed. from a geotechnical standpoint. The plan is not included in this report; however, the geoteohnically»related information pertinent to the development is addressed in this report. Tlie precise grading plan may be obtained through RJ33F Consulting, if additional information is needed. Our review of the plan indicates: The existing improvements, including brick paving and concrete sidewalk as part of the existi..ng pool, will be demolished, • The site will be precise graded to accommodate the proposed pool bar and its associated improvements, such as concrete sidewalks around the pool bar, 24.in.cl7 wide seat walls. pilaster and areas drains. The precise grading will consist of cut and fill of less than one foot.. Grading notes, paving notes, construction notes, erosion notes are shown on the plan. • The pool bar footprint, pad and finish floor elevations, finish surface elevations, rough grade contours and the surrounding slopes are shows, on the plan. The plan, set also inoludes demolition plan and erosion control plan with details. • Surface drainage of the pool bar pad is generally collected through area drains that drain into the storm drain system. 4 z - Leighton 920882.021 Conclusion The precise grading plait is acceptable from a geoterhnical standpoint provided the recommendations presented in this report are implemented in the design and construction of the project. We did not encounter signif..tcant geotechnioal constraints onsi.te that cannot be mitigated by proper planning, design, and sound construction practices, In the event that any significant changes are made to the proposed site development, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the recommendations of this report. are verified or modified in writing by Leighton. The conclusions and recommendations in this report are based in part upon data obtained from �a limited number of observations, site visits, excavation.., samples, and tests, Such information is by necessity incomplete. The nature of rnany sites is such that differing geotechnical or geological conditions can occur within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time, Therefore, the findings, conclusions, and recommendations presented in this and referenced reports can be relied upon only if Leighton has the opportunity to observe the subsurface conditions during grading and construction of the project in order to confirm that our preliminary findings are representative for the site.. Recommendations Our recommendations are considered .minimums and may be superseded by more restrictive requirements of the architect, structural engineer, building code, or governing agencies. I. Precise Grading Operations: Prior to the precise grading, the existing improvements should be removed properly. Any vegetation and. debris should be removed and disposed of offsite. .All. weathered and dry nxaaterials not removed by the proposed grading should 'be scarified, moisture -conditioned to near optimum and compacted prior to placement of additional till and/or pool bar construction, Fill materials should be free of debris and organic matter. Pill materials should be placed in loose, horizontal lifts no thicker than 8 inches, moisture -conditioned and mixed, as necessary: and compacted to a min.im.um of 90 percent of maximum dry density as determined by -3- 4 Leighton 920882-021 A.STM Test Method D1557. Fill on sloping ground should be benched into firm, competent material. 2. Four datioi_Sel.ection; Based on the precise grading plan and information provided to us, the pool bar will be located south of the existing pool maintenance building at a minimum distance of 12 feet from the top of a 30-foot high descending slope. The pool bar is expected to be located outside of the slope creep zone; and, therefore, may be supported on conventional shallow foundation, To reduce the potential impact from slope creep, structural improvements within the creep zone shown in Figure 1 may he supported on deepened footings or caissons. 3. Foundation, Design and Allowable _ earjng Pre ure: Results of expansion testing of representative samples from the adjacent site indicate the soils have na.edium expansion potential. Due to variability of the onsite soils, 1;hc proposed structures should be designed assuming an expansion potential of high. In addition, subgracle below slabs -on -grade should be presaturated to a minimum of 1.4 times optimum -moisture content to a minimum depth of 24 inches. An allowable bearing pressure of 1,500 pounds per square foot (psf) may be useci for conventional footings having a tnininium embedment in approved material of 1 foot below the lowest adjacent grade and a minimum width of 1 foot, The bearing capacity may be increased by 300 psf for each additional foot of width or each additional foot of embedment, to a maximum value of 3,500 psf. The allowable bearing may be increased by one-third for wind or seismic loading. Total and differential settlement due to footing loads is anticipated to be less than l and % inch over a distance of 30feet, respectively, 4, Footing Se tbaek; Footings to be constructed. on or above slopes should. maintain a setback or be of sufficient depth such that the outside bottom, edge of the footing is Z1/3 horizontal feet from the face of the slope, where H is the height of the slope. The setback should be a minimum of 5 feet but need not exceed 40 feet, This setback is based on the expansive nature of the site soils and is intended to reduce the potential impacts of slope creep. The setback may be increased to reduce potential of slope creep depending oil actual field conditions, and may be accomplished by deepened footings or caissons. Deepened footings or, caissons should be designed to account for lateral load due to slope creep as shown on Figure 1, Geotechnical Parameters for Design of Structure Potrndation within Creep Zone. As indicated on the figure, the at -rest pressure should be used to account for the load due to slope creep and the passive pressure within the creep roue should be ignored. 4 4 Leighton 920882-021 5, Seismic Design Parameter: This site is not located within a currently designated Alqu.ist-Priakk Earthquake Fault Zone, However, strong ground shaking due to seismic activity is anticipated at the site. The nearest fault from the site is Newport -Inglewood fault at the distance of 1.5 miles. The following seismic design values in the table are based on 2007 California Building Code (CSC, 2007). These parameters should be considered as the minimum for the seismic analysis of the subject site. Additional seismic analyses may be necessary based on structural requirements. Seismic Design Parameters (CBC, 2007) Categorization/Coefficient Design Value Site Class D Short Period. (0.2 sec) Site Coefficient, F. 1.0 Long Period (1,0 sec) Site Coefficient, F,, 1.5 Design (5% damped) spectral response acceleration parameter at short period, Sin 1.130 Design (5% damped) spectral response acceleration parameter at a period. of 1 sec, Sr,, 0,614 6, Concrete S1 ,s-Ork-Grade: Subgrade for concrete slabs -on -grade should be pn saturated to a minimum of 1..4 times the optimum -moisture content and to a minimum depth of 24 inches based on the high expansion potential of the site soils. A. 6-aril. vi.squeen or equivalent barrier, sandwiched within a minimum 4-inah layer of sand, should be provided below the slabs where moisture sensitive improvements are planned. In addition, the edges of the slabs should. be deepened to a minimum thickness of 24 inches to reduce migration of. moisture. Concrete slabs -on -grade should have a rninirnutn thickness of 6 inches and reinforced with No. 3 rebar at 18 inches on center. These recotnmendations are minimum and may be superseded by the requirements of the structural engineer. ','r. Cement Type: Due to the anticipated variation in sulfate content of the onsite soi.is, Type \` cement or equivalent should be used for all concrete in contact with the near -surface onsite earth. The concrete should be designed in accordance with ACT 318. All concrete is subject to hazards such as excessive cracking, excessive water vapor transmission, sulfate attack, efflorescence, and other modes of decay. Adherence to the following guidelines will help minimize the susceptibility of completed work to the above hazards, 5 4 Leighton 92088Z 021. • Drying Shrinkage Cracking: Follow recommendations of AC,I 302.1R for industrial/commercial structures, follow recommendations of ACT 332.R for residential construction, as appropriate; — Maintain concrete slump below 5 inches; — Use minimum cement required to achieve desired strength; — Provide effective concrete curing for seven clays after placing; — Design control joints into slab; and Do not place concrete on. hot, windy, tow -humidity days. .Reduction of "Vapor Transmission: Maintain concrete slump below 5 inches; - Avoid construction punctures of vapor barriers; Seal vapor barrier joints; Extend vapor barrier into grade beam concrete; - Prevent overirrigation of landscaping; and Use floor -covering adhesives that are not water soluble. or 8. Corrosion Protection Measures: The low resistivity of th,e near -surface clays at the site indicates that these soils are potentially corrosive to metals, Special measures for corrosion control for metal in contact with the subgrade soils, such as cathodic protection, corrosion allowance or protective coating or sleeving, may be needed. 9. Concrete Driveway, Driveway Approaches, Curb and Gutter: Cracking of concrete is often not due to settlement/heave of soils, but often due to other factors such as tltc use of too high water/cement ratio and/or inadequate steps being taken to prevent moisture loss during curing. Appropriate steps should be taken to minimize cracking of the concrete due to these factors. To reduce the extent of unsightly cracking, concrete driveways, driveway approaches, curb and gutter should be a minimum of 6 inches thick and provided with construction or weakened plano joints every 10 feet or loss. A. layer of crashed rock, gravel, or clean sand having a minimum. thickness of 4 inches should underlie the slabs. Presoaking of the subgrade to a minimum 140 percent of optic um -moisture content to a minimum depth of 24 inches is also recommended, Reimfomement of tho slabs may also be considered. 4 Leighton 920882-021 11. Other Concrete Pl.atwork: AS with driveways, because of expansive soil forces and other factors, concrete flatwork (such as walkways, swimming pool decks, patio slabs, etc.) has the potential for cracking. To reduce the potential for excessive cracking, con.erete should be a minimum of 4 inches thick and provided with construction or weakened plane joints at frequent intervals (e.g,, every 6 feet or less). A layer of dished rock, gravel., or clean sand, and presoaking of the slab subgrad.e, as recommended in the above section for concrete driveway, is also recommended for other concrete flatwark. Reinforcing the sl.abs may also be considered and is recommended for any flatwork near the top -of -slope. 1~latwork located near the top of the slope is likely to be more susceptible to cracking over, the long terra because of slope creep. All of the steps indicated above should reduce the potential for excessive cracking, but may .not completely eliminate it. As an alternative, consideration can also be given to using flexible flatwork, such as pavers, near the top••of.slape. 12. Surface Drainage: Soil moisture; content around the perimeter of the proposed building should be maintained as near, to optimum as possible. This may be achieved by maintaining adequate surface drainage and controlling irrigation. Ponding of water adjacent to structures must be avoided; roof gutters, downspouts, drainage males, and area drains should be aligned so as to transport surface water away from structures. Area drain inlets and drainage swal.es should be adequately maintained and kept clear of debris. Care should be taken to ensure that yard landscaping does riot cause any obstruction. to the area drains and yard drainage. Rerouting of the area drains and yard drainage pattern should he undertaken, if necessary. Irrigation should be controlled through the various seasons of the year, adjusting for periods of excessive rainfall or aridity, so as to prevent saturation and/or dryness of the soils. Overwatering and undetwatering of landscape areas must be avoided. Locating planters adjacent to building or structure should be avoided, if possible. If planters are utilized in these .locations, they should be properly designed so as to prevent fluctuations in subgrade moisture content. Planters adjacent to building should be properly lined, such as with a membrane, to reduce penetration of irrigation water into the adjacent footing subgrades. Planting areas at grade should be provided with appropriate positive drainage. Planters should not be depressed below adjacent paved grades unless provisions for drainage, suds). as catch basins and drains, are made. Adequate drainage gradients, devices, and curbing should be provided to prevent runoff frorn adjacent pavement or walks into planting areas. 13 Trend Baekftll: Trench excavations for utility pipes may be backfilled with onsite soils under the observation of the representative of the geotechnical engineer. After utility pipes have been laid, the space under and around the pipe should be backfilled with clean sand or gravel, having sand equivalent of 30 or greater, to a depth of at least 1 foot over the tt of the -7- Leighton 920882 -02 t pipe (or in accordance with the plans and specifications if more than 1 foot is specified). before the controlled baciclill is placed. Where utility trenches cross underneath building footing, the trenches should be plugged by a minimum of 2 feet of onsite soil or sand/cement slurry to reduce the potential for water intrusion, underneath the slab -an -grade. Trenches excavated on a slope face for utility or irri.gation limes and/or other purposes should be properly backfilled and compacted out to the slope face by a vibratory plate, or equivalent, in order to obtain a minimum 90 percent relative compaction, in accordance with ASTM Test Method 01557. Observation/testing and acceptance by this gcotccbni.cal consultant during trench bacicfill is recommended. 14. Slope Maintenance/Erosion control: To reduce the erosion, and slumping potential, any graded slope should be planted with ground -cover vegetation (e.g., grasses) and deep-rooted vegetation (e.g., trees and shrubs) as soon as practical. Erosion and slumping potential remains high until the vegetation is established. Prior to landscaping, consideration should be given to hydroseeding, or placement of a polymer layer or other protection for the slope face. Oversteepening of slopes should be avoided during future grading et construction. The maintenance of proper pad drainage, the design and construction of property improvements in accordance with sound engineeri.n.g practices, and proper maintenance of landscaping, including regular .pad and slope irrigation, should be ,performed. Establishing and maintaining a rodent -control program is also recommended to reduce surfeial slope deterioration often associated with rodent burrowing. 15. GeotechnicalQbservationl'Te tfng durin Any Future Cr •a.dln : Observation/testing should be perfontied by the geotechnical consultant during at least the following stages: • During precise grading; • During placement ofbackfill for utility trenches; • After footing excavation and prior to pouring concrete; • During subgrade presaturation; and • When any unusual soil conditions arc encountered during any construction, subsequent to the issuance of this report. -8- Leighton 92O 82 021. If you have any questions regarding this report, please do not hesitate to contact this office, We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. Djan F1.landra, PE, GE 2376 Senior Principal Engineer Tf/DJCI1r Attachment: Figure 1 - Geoteohr ical Parameters for Design of Structure Foundation within Creep Zone Distribution: (3) Addressee Leighton r! H/: min, 5 font to max. 40 font.— (ti a Slope Helghi) t, Ignore Passive Pressure Within Creep Zone Passive Pressure Deepened Fooling or Caisson At —Rest Pressure Pressure Diagram 0FFPE NL:L7 ►`OOTING At —Rest Equivalent Fluid Prassurca = (35 pcf Passive Equivalent Fluid Pressure = 120 pcf Coefficient of Friction = 0.35 Allowable Searing Pressure* = 1,600 psf (May be Increased by Sop pot for each additional foot of width or embedment to maximum value of 2,300 pef) C,n,15.S CI t At —Rest Equivalent Fluid Pressure = 65 pcf x 1. ( L = Caisson Spacing) Passive Equivalent Fluid Pressure = 120 pcf x 3D (D= Caisson Diameter) Coefficient of Friction ts 0.35 Allowable Bearing Pressure* = Same as Above (Maximum value: 5,000 psf) Allowable Skin Friction* _ (200 x 'rro) lbs/ft Below Creep Zone ("May bo Inaroomed by 1/5 for chart —form loading) Figure GEOTECHMICAL PARAMETERS FOR DESIGN OF STRUCTURE FOUNDATION WITHIN CREEP ZONE Prot: 920882-021 Date: 5/0B Eng: DJC Scale: NTS r:tortAP711,0020862%211f10ilnE1.2.1)wn(NM)t-01 AA1,10PMl Plotted CY. •m}h.h Leighton and Associates. inc. a aa�gvrno .)hour cQareu•