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2002-7439 G r i i ' MAC 2002 :wGINEERINGSERVI c�� CITYOFENCINITAS 1 REPORT OF FINAL GRADING OBSERVATION, 1 SOIL TESTING AND GEOTECHNICAL ENGINEERING Proposed Brown Residence ' 1515 Lake Drive Encinitas, California ' JOB NO. 01-8071 26 February 2002 ' Prepared for: ' Mr, and Mrs. Andrew Brown SPIN' GEOTECHNICAL EXPLORATION, INC. SOIL&FOUNDATION ENGINEERING • GROUNDWATER HAZARDOUS MATERIALS MANAGEMENT • ENGINEERING GEOLOGY 26 February 2002 ' Mr. and Mrs. Andrew Brown Job No. 01-8071 1515 Lake Drive Encinitas, CA 92024 ' Subject: Report of Rough Grading Observation, Soil Testing and Geotechnical Engineering ' Proposed Brown Residence 1515 Lake Drive Encinitas, California ' Dear Mr. and Mrs. Brown: ' As requested, Geotechnical Exploration, Inc., hereby submits the following report summarizing our work and test results, as well as our conclusions and recommendations concerning the subject project. A representative of our firm observed the recent rough grading operation and tested the fill soils that were removed and recompacted during the preparation of the building pad area. ' The grading described herein consisted of removing and recompacting on-site soils and importing fill soils and compacting them to reach the planned grades. The ' grading was observed and/or tested between December 26, 2001, and January 3, 2002. SCOPE OF WORK The scope of work of our services included: 1 1. Observations during rough grading of the site. ' 7420 TRADE STREET • SAN DIEGO, CA 92121 • (858)549-7222 • FAX: (858)549-1604 • E-MAIL: geotech @ixpres.com i Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 2 ' 2. Performing field density tests in the placed and compacted fill. ' 3. Performing laboratory tests on representative samples of the fill material. ' 4. Providing professional opinions, conclusions, and recommendations regarding the observed grading and the pending work. GENERAL SITE INFORMATION The property, consisting of approximately 5 acres, is located at 1515 Lake Drive, in ithe City of Encinitas, California. The property is bordered on the north, south and east by similar combined residential and agricultural properties; and on the west by ' Lake Drive. The new residence will be built on the northeast portion of the property. Prior to this grading, the site included a packing shed structure surrounded by parking and driveways with gravel pavement. Prior to grading, the building area of the property sloped from east to west, with elevations ranging from approximately 367 feet above mean sea level (MSL) to 363 ' feet above MSL. Precise survey information concerning actual elevations after grading was not available at the time of this report preparation. Existing structures on the property prior to grading included the packing shed, ' greenhouse structures on the south and northwest portions of the property, and a residence to the west of the existing packing shed. Existing vegetation prior to grading consisted of trees, shrubs and lawn grass. The site has been prepared to receive the proposed new residence, which will be a ' maximum of two stories in height. It is our understanding that the building will be constructed in conformance with the Uniform Building Code, utilizing conventional- � l- Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 3 ' type foundations, footings, and building materials. A Plot Plan illustrating the approximate location of all our tests taken throughout the grading operation is ' enclosed as Figure No. I. ' Work that remains to be completed at the site and that will require our observations and/or testing include any retaining wall backfill, trench backfill, R-value testing for areas to be paved, and final subgrade and base preparation of areas to receive pavement or rigid improvements. FIELD OBSERVATIONS Periodic tests and observations were provided by a representative of Geotechnical ' Exploration, Inc. to check the grading contractor's (Mr. Mike Scott) compliance with the drawings and job specifications. The presence of our field representative at the site was to provide to the client a continuing source of professional advice, opinions, and recommendations based upon the field representative's observations ' of the contractor's work, and did not include any superintending, supervision, or direction of the actual work of the contractor or the contractor's workers. Our visits ' were made on request of the contractor's representative. ' The grading operation was observed to be performed in the following general ' manner: ' 1. Prior to placing any compacted fill, the areas to be graded were cleared of surface trash, miscellaneous debris, and/or vegetation, and hauled off-site. ' 2. Uncompacted fills and loose or disturbed materials were removed to expose ' competent ground. The removed material in the building pad areas was extended to a depth of at least 3 feet below finish subgrade, and to at least 5 GHPIL 40 Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 4 feet beyond the perimeter building lines. In the drive and patio areas, the removal and recompaction of unsuitable soils was extended to a depth of at ' least 1 foot below finish subgrade. ' In slope fill areas, the slope toe was provided with a key excavation into competent bearing soil. The key had a width of at least 12 feet and a ' thickness of at least 2 feet. 3. The exposed ground surface was scarified at least 6 inches and uniformly recompacted prior to placement of compacted soil. Scarification or recompaction was not required on sound bedrock. 4. Areas to receive compacted fill were, in general, observed and evaluated by our field representative prior to placing compacted fill. In slope fill areas, ' adequate benching was provided by keying into competent natural ground or approved compacted fill as the compacted fill was placed above the toe area. 5. Soils approved for use in the compacted fill were placed in horizontal layers ' not exceeding approximately 10 inches in loose thickness. 6. Fill material was watered or dried at or near optimum moisture content, and ' mixed prior to compaction. 7. The soils utilized in the grading operation were from on-site and imported soils and consisted primarily of silty, fine to medium sands. ' 8. Fill materials were tested at specific test locations and found to be compacted ' at those locations to at least 90 percent of Maximum Dry Density. 4rpi Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 5 ' 9. Compaction was achieved by drying or wetting the soil, mixing it and rolling it with heavy construction equipment such as a D-6 dozer, a track-mounted ' loader, and an excavator. Water was provided with a water hose. ' 10. Field density tests were taken at the approximate locations shown on the plot plan (Figure No. I). TESTS Field density tests were performed in accordance with ASTM D1556 and D2922. ' Maximum density determinations were performed in accordance with ASTM D1557. The relative compaction results, as summarized on Figure No. II, are the ratios of ' the field densities to the laboratory Maximum Dry Densities, expressed as ' percentages. CONCLUSIONS AND RECOMMENDATIONS 1 The following conclusions and recommendations are based upon our analysis of all ' data available from the testing of the soils compacted on this site. Our observations of the grading operation (while in progress), our field and laboratory ' testing of the typical bearing soils, and our general knowledge and experience with the natural-ground soils and recompacted fill soils on this site were utilized in conducting our services. 1 A. General Grading 1. The soils utilized in the grading operation were from existing on-site soils that t were removed and recompacted, and imported materials that were placed and recompacted. The soils consisted primarily of silty, fine to medium ' Propose d Brown Residence Job No. 01-8071 Encinitas, California Page 6 ' sands. Soils of this type are considered very low to low expansive, as measured by the UBC Expansion Index Test (29-2 standard) and per simple ' visual inspection. ' 2. During the grading operation, the natural-ground soils were exposed (in the building pad area) and properly prepared to receive the fill soils. The fill soils ' were placed, watered, compacted, and then tested at specific test locations, and were found to be compacted at the tested locations to at least 90 ' percent of Maximum Dry Density, in accordance with the requirements of the City of Encinitas. The maximum depth of fill soils placed on this site at the time of the grading operation monitored by this firm was not in excess of 9 feet in vertical thickness. 3. Any surplus, loose, stockpiled soils remaining at the property should be ' removed and hauled off the site. ' 4. Grading work that needs to be completed and performed under our observations and testing include any retaining wall backfill, trench backfill, ' and finish subgrade and base preparation in areas to receive pavement or rigid improvements. B. Foundations and Slabs On-Grade 5. The continuous foundations and spread footings shall extend a minimum ' depth of 18 inches into the firm natural ground or properly compacted fill, and have a minimum width of 12 inches. The continuous foundations shall be reinforced with at least four No. 4 steel bars; two bars shall be located near the top of the foundations and two bars 3 inches from the bottom. Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 7 ' Additional steel may be required by the structural engineer in deeper footings. 6. Prior to pouring footings and foundations, and prior to placement of floor slab ' base sections, the soils shall be properly moistened. The subgrade moisture content and penetration should be verified by our field representative 24 hours prior to concrete pouring. The bottom of the foundation excavation should be firm, not muddy, and have the acceptable moisture content. 7. Concrete floor slabs shall be founded on at least 2 inches of sand overlying a ' moisture barrier on 2 inches of sand. The slabs shall be reinforced with at least No. 3 steel bars placed on 18-inch centers. Any steel reinforcement ' should be placed in the middle of the floor slab section. Proper supports should be used to keep the steel reinforcement separated from the base or ' soil subgrade. 8. It is recommended that all nonstructural concrete slabs (such as patios, sidewalks, etc.) be founded on at least 12 inches of low-expansive, properly ' compacted soils. Proper shrinkage joints (sawcuts) should be provided and spaced no farther than 10 feet or the width of the slab, whichever is less, and also at re-entrant corners. The sawcuts should be performed no later than 12 hours after pouring, or as soon as the concrete is set. Sawcuts should be deepened to at least one-quarter of the thickness of the slab. 9. All concrete (flatwork) slabs or rigid improvements should be built on ' properly compacted and approved subgrade and/or base material. Geotechnical Exploration, Inc, will accept no liability for damage to ' flatwork or rigid improvements built on untested or unapproved subgrade or base material. Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 8 ' C. Foundation Design Parameters ' 10. The recommended allowable soil bearing capacity of the properly compacted fill soils placed on the site is 2,500 pounds per square foot. The ' recommended allowable soil bearing capacity may be increased 1,200 psf for each additional foot in depth, and 600 psf for each additional foot in width. ' The total bearing capacity shall not exceed 6,000 psf. This soil-bearing value may be increased one-third for design loads that include wind or seismic tanalysis. Additionally, these bearing capacities may be utilized in the design of foundations and footings of the proposed structure when founded a ' minimum of 18 inches into the firm natural ground or compacted fill for the proposed structures. For on-site conditions, it is expected that the maximum settlement will not exceed 1 inch, and the maximum differential angular rotation will not exceed 1/240. 11. The passive earth pressure of the encountered natural-ground soils and well- ' compacted fill soils (to be used for design of building foundations and footings to resist the lateral forces) shall be based on an Equivalent Fluid ' Weight of 300 pounds per cubic foot. This passive earth pressure shall only be considered valid for design if the ground adjacent to the foundation structure is essentially level for a distance of at least three times the total depth of the foundation, the soil is properly compacted fill or natural dense tmaterial, and the concrete is poured tight against the walls of the excavation. 12. A Coefficient of Friction of 0.40 times the dead load may be used to calculate the total friction force between the bearing soils and the bottom of concrete wall foundations, or structure foundations, or floor slabs. 1 SHIM! q 1 l- Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 9 ' D. Retaining Wall Design Parameters ' 13. The active earth pressure (to be utilized in design of cantilever walls, etc.) shall be based on a Equivalent Fluid Weight of 38 pounds per cubic foot (for ' level backfill only and low-expansive, on-site native soils). In the event that the cantilever retaining wall is surcharged by sloping backfill, the design active earth pressure shall be based on an Equivalent Fluid Weight of 52 pcf. In the event that a retaining wall is to be designed for a restrained condition, a uniform pressure equal to 8xH (eight times the total ' height of retained soil, considered in pounds per square foot) shall be considered as acting everywhere on the back of the wall, in addition to the ' design Equivalent Fluid Weight. ' The design pressures presented above are based on utilization of an uncontrolled mixture of expansive or low-expansive soil native to the site 1 used in backfill operations. In the event that imported, clean, granular fill soils or approved, on-site, clean sands are to be utilized as backfill material, this firm should be contacted for possible reduction of design pressures due to level backfill, sloping backfill, or restrained wall conditions. r Additional surcharge pressures to be considered in the wall design include any loads applied within the failure block retained by the wall. ' E. Cut and Fill Slopes ' 14. Natural-ground cut slopes of maximum inclinations of 2.0 horizontal to 1.0 vertical, and compacted fill slopes of maximum inclinations of 2.0 horizontal 1 �- ' Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 10 ' to 1.0 vertical, shall be stable and free from deep-seated failures for materials native to the site and utilized in compacted fills. 1 15. Although the compacted fill soils have been verified at the tested locations to ' a relative compaction of 90 percent of Maximum Dry Density or better, the compacted fill soils that occur within 5 feet of the face of the fill slope may ' posses poor lateral stability. If not properly founded, any proposed structures and associated improvements (such as walls, fences, patios, ' sidewalks, swimming pools, driveways, asphalt paving, etc.) that are located within 5 feet of the face of compacted fill slopes could suffer differential ' movement as a result of the poor lateral stability of these soils. ' The foundations and footings of the proposed structures, fence posts, walls, etc., when founded 5 feet and farther away from the top of compacted fill slopes, may be of standard design in conformance with the recommended soil value. If proposed foundations and footings are located closer than 5 feet inside the top of compacted fill slopes, they shall be deepened to at least 11/2 feet below a line beginning at a point 5 feet horizontally inside the fill ' slopes, and projected outward and downward, parallel to the face of the fill slopes (see Figure No. III). 16. It is recommended that all compacted fill slopes and natural cut slopes be ' planted with an erosion-resistant plant, in conformance with the requirements of the City of Encinitas. F. Drainage 17. Adequate measures shall be taken to properly finish-grade the site after the structure and other improvements are in place. Drainage waters from this Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 11 I . ' site and adjacent properties are to be directed away from foundations, floor slabs, footings, and slopes, onto the natural drainage direction for this area ' or into properly designed and approved drainage facilities. Roof gutters and downspouts should be installed on the structure, and the runoff directed ' away from the foundations via closed drainage lines. Proper subsurface and surface drainage will help minimize the potential for waters to seek the level ' of the bearing soils under the foundations, footings, and floor slabs. Failure to observe this recommendation could result in uplift or undermining and Idifferential settlement of the structure or other improvements on the site. Sufficient area drains shall be placed in flower beds, planters, and landscape ' areas in general. ' 18. Proper subdrains shall be installed behind any retaining and restrained retaining walls, in addition to proper waterproofing of the back of the walls. ' The drainage of said subdrains shall be directed to the designed drainage for the project or the natural drainage for the area. 1 19. It should be noted that changes of surface and subsurface hydrologic ' conditions, plus irrigation of landscaping or significant increases in rainfall over the "accepted average-annual" rainfall for San Diego County in past ' years, may result in the appearance of minor amounts of surface or near- surface water at locations where none existed previously. The damage from ' such water is expected to be minor and cosmetic in nature, if corrected immediately. Corrective action should be taken on a site-specific basis if, and ' when, it becomes necessary. ' 20. Planter areas, flower beds, and planter boxes shall be sloped to drain away from the foundations, footings, and floor slabs. Planter boxes shall be ' constructed with a sealed bottom, and be provided a subsurface drain IProposed Brown Residence Job No. 01-8071 Encinitas, California Page 12 I installed in gravel, with the direction of subsurface and surface flow away from the foundations, footings, and floor slabs, to an adequate drainage Ifacility. ' 21. Any backfill soils placed adjacent to or close to foundations, in utility trenches, or behind retaining walls, that support structure and other improvements (such as patios, sidewalks, driveways, pavements, etc.), other than landscaping in level ground, shall be compacted to at least 90 percent of ' Maximum Dry Density. It is recommended that Geotechnical Exploration, Inc. observe and test the backfill during placement. Geotechnical Exploration, Inc. will accept no liability for damage to ' structures that occurs as a result of improperly backfilled trenches or walls, or as a result of fill soils placed without our observations and testing. G. Miscellaneous Recommendations 22. Following placement of concrete floor slabs, suff=icient drying time must be ' allowed prior to placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of ' the finish-floor materials. 23. Swimming pools and/or subsurface structures that are founded in any potentially expansive clay soils shall be properly designed by a structural engineer and/or soils engineer. 24. The remaining soil work to be completed at the site (such as trench backfilling or final subgrade base preparation in areas to receive exterior IProposed Brown Residence Job No. 01-8071 Encinitas, California Page 13 I hardscape or paving, etc.) should be performed under our observations and testing. I b a 25. It is also recommended that all footing excavations be observed y representative of this firm prior to placing concrete, to verify that footings are founded on satisfactory soils for which the recommendations expressed in the soil •investigation report remain applicable. ISUMMARY ' Based on our field testing and grading observation, it is our opinion that the grading operation described herein, in general, was performed in conformance with the City of Encinitas Grading Ordinance. It is to be understood that our test results and opinion of general acceptance do not guarantee that every cubic yard of compacted ' fill has been compacted to specification since not every cubic yard has been observed or tested. Our test results indicate the measured compaction degree ' obtained at the specific test location. We can only attest that our tests and observations have been made in accordance with the care and current professional ' standards in our field. ' All observed or tested work done during the grading operation appears, in general, to have been performed in accordance with the soil investigation report for this site, ' issued by our firm and dated October 16, 2001 (Job No. 01-8071). The grading described herein was observed and/or tested between December 26, 2001, and ' January 3, 2002. ' All statements in the report are applicable only for the grading operation observed by our firm, and are representative of the site at the time of our final site visit ' before the report was prepared. The firm of Geotechnical Exploration, Inc. shall G Proposed Brown Residence Job No. 01-8071 Encinitas, California Page 14 i . ' not be held responsible for fill soils placed without our observations and testing at any other time, or for subsequent changes to the site by others, which directly or ' indirectly cause poor surface or subsurface drainage, water erosion, and/or alteration of the strength of the compacted fill soils. In the event that any changes in the nature, design, or location of the building or ' improvements are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the ' conclusions of this report modified or verified in writing. ' Professional opinions presented herein have been made based on our tests, observations, and experience, and they have been made in accordance with ' generally accepted current geotechnical engineering principles and practices within the County of San Diego. This warranty is in lieu of all other warranties, either ' expressed or intended. ' Thank you for this opportunity to be of service. Should any questions arise concerning this report, please do not hesitate to contact us. Reference to our Job ' No. 01-8071 will help to expedite a reply to your inquiries. ' Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. ' Jaime-9. iferros, P.E. R.C.E. 34422/G.E. 2007 i No. 002007 l Senior Geotechnical Engineer ; Ex p.�,�,63 fJ r� J'f\cc0 Pv / cc: Addressee (4) GH HIS PLOT PLAN WAS PREPARED FROM AN -PLAN BY WILLIAM HOLCOMB ARCHITECT DATED �_7-OPP oxima__tely. .-__:__.._.� FROM ON-SITE FIELD RECONNAISSANCE 1'2'U. --y GEI. r - -nd APPROXIMATE LOCATION OF FIELD DENSITY TEST PROPOSED STRUCTURE h'+ t EXUS77NG PACIONG SHED BUILDING AREA UNDERCUT DRIVEWAY AND PATIO AREA UNDERCUT uirdercut) BOTTOM OF EXCAVATION SCHEMATIC Gravel p PLOT PLAN proxi- oxi Driveway itions Access to roved Brown Residence Lake Drive Ions' 1515 Leke Drive EW417 tag, CA Figure No.lb Jab No. 01-8071 OOOtOohnloal --- -- - bgsloratlon 1 no. 01-8071-P2 ' COMPACTION TEST RESULTS ' _]_ELEVATION MOISTURE FIELD SOIL RELATIVE TEST DATE LOCATION OF M DENSITY TYPE COMPACTION ' FILL ' 1 12127101 See plot plan 359' 13.6 119 pcf II 92% 2 12/27/01 See plot plan 360' 12.3 121 pcf II 94% ' 3 12/27101 See plot plan 361' 9.9 119 pcf II 92% 4 12/28/01 See plot plan 362' 10.2 124 pcf III 94% ' 5 12/28/01 See plot plan 363' 9.0 123 pcf III 93% ' 6 12/28/01 See plot plan 362' 11.1 121 pcf III 92% 7 1/3/02 See plot plan 365' 10.9 117 pcf II 91 % ' 8 1/3/02 See plot plan 365' 12.1 121 pcf III 92% 9 1/3/02 See plot plan 366'/FG 11.4 1 19 pcf III 90% ' 10 1/3/02 See plot plan 366'/FG 11.8 121 pcf III 92% ' SOIL CLASSIFICATION TYPE DESCRIPTION O.M.C. MAX. DRY DENSITY ' II Orange-brown, silty, fine to medium sand. 8.0% 129 pcf ' III Red-brown, silty, fine to medium sand (import). 9.0% 132 pcf I Job No. 01-8071 Irrl ' Figure No. 11 FOUNDATION REQUIREMENTS NEAR SLOPES ' Structure TOP OF COMPACTED HLL SLOPE Proposed Structure loose sots on the slope surface shall not be considered to provide lateral or vertical strength for the Concrete R=Slab ':; footing or for slope stability. Needed depth of imbedment shall be measured ' Setback - x from competent soil.) I� COMPACTED FILL SLOPE WITH MA)QMUM INCLINATION AS PER SOILS REPORT. Reinforcement of \ Foundations and Poor v v ` ww- ' Slabs Following the � Total Depth of Footing Recoffirnenckitions of the Measured from Finish W Architect or Structural Sub-Grade ' Engineer. \ COMPACTED HLL' Concrete Founcftn \ ' I Sm Minirnurn or as Deep \ _ Outer Most Face.- as Required for Lateral of Footing Stability TYPICAL SECTION ' (Showing Proposed Foundation Located Within 5 Feet of Top of Slope) I W FOOTING / 5' SETBACK ' Total Depth of Fooiing ' 1.5:1.0 SLOPE # 2.0:1.0 SLOPE 0 5(r 48" E 1' 51" 42 ' � 7 42 W 0 3' 34' 30° va 0 4' 26' 24" F' lg" ' # when applicable Figure Wo. F/! Job No. 01-8071 464 Cleatedudad EKpkwadon,