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HomeMy WebLinkAboutCT 01-12; RIVA GARDENS; REPORT OF PRELIM GEOTECH INVESTIGATION; 2002-08-28REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Riva Gardens Residential Development - CTOl-12 1080 Chestnut Avenue Carlsbad, California JOB NO. 02-8291 28 August 2002 Prepared for: Joseph and Nadja Spano GEOTECHNICAL EXPLORATION, INC SOIL & FOUNDATION ENGINEERING • GROUNDWATER H/\ZARDOUS MATERIALS MANAGEMENT • ENGINEERING GEOLOGY 28 August 2002 Joseph and Nadja Spano Job No. 02-8291 c/o JACK HENTHORN & ASSOCIATES 5365 Avenida Encinas, Suite A Carlsbad, CA 92008 Subject: Report of Preliminary Geotechnical Investigation Riva Gardens Residential Developnnent - CTOl-12 1080 Chestnut Avenue Carlsbad, California Dear Mr. And Mrs. Spano: In accordance your request, and our proposal of July 17, 2002, Geotechnical Exploration^ Inc. has prepared this report of geotechnical investigation for the subject site. The field work was performed on July 25, 2002. It is our understanding that the existing residential lot is being split into 5 parcels and it is proposed to develop the site to receive 3 new single-family residences with attached garages and associated improvements. The proposed structures are to be a maximum of two stories in height and are to be constructed of standard-type building materials utilizing a concrete slab-on-grade foundation system. The purpose of our investigation was to evaluate the soil conditions in the proposed building areas, recommend any necessary site preparation procedures, assess the allowable bearing value of the on-site soils, and to provide slab and foundation design recommendations. Our investigation revealed that the site is underlain by medium dense, moderately well cemented, terrace deposit formational materials overlain with Vh to 2 feet of loose to medium dense cultivated topsoils. These variable density topsoils will not provide a stable soil base for the proposed structures and associated improvements. As such, we recommend that these shallow topsoils be removed, scarified and recompacted to a depth of approximately 2 feet as part of site preparation prior to the addition of any new fill or structural improvements. In our opinion, ifthe conclusions and recommendations presented in this report are implemented during site preparation, the site will be suited for the proposed structures and improvements. 7420 TRADE STREET • SAN DIEGO, CA 92121 • (858) 549-7222 • FAX: (858) 549-1604 • E-MAIL; geotech@ixpres,conn This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please do not hesitate to contact us. Reference to our Job No. 02-8291 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. Jaime A. Cerros, P.E. R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer JKH/JAC/pj TABLE OF CONTENTS I. SCOPE OF WORK II. SITE DESCRIPTION III. FIELD INVESTIGATION IV. SOIL DESCRIPTION V GROUNDWATER VI. LABORATORY TESTS AND SOIL INFORMATION VII. CONCLUSION AND RECOMMENDATIONS VIII. GRADING NOTES IX. LIMITATIONS PAGE 1 2 3 3 4 5 7 19 20 REFERENCES FIGURES I. II. Illa-e. IV. Vicinity Map Plot Plan Excavation Logs Laboratory Test Results APPENDICES A. B. Unified Soil Classification System General Earthwork Specifications REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Riva Gardens Residential Development 1080 Chestnut Avenue Carlsbad, California Job NO. 02-8291 The following report presents the findings and recommendations of Geotechnical Exploration, Inc. for the subject project (for project location see Figure No. I). I. SCOPE OF WORK It is our understanding, based on communications with Mr. Jack Henthorn, that the existing residential lot is being split into 5 parcels and it is proposed to develop the site to receive 3 new single-family residences with attached garages and associated improvements (see Figure No. II for Plot Plan). The proposed structures are to be a maximum of two stories in height and are to be constructed of standard-type building materials utilizing a concrete slab-on-grade foundation system. With the above in mind, the Scope of Work is briefly outlined as follows: 1. Identify and classify the surface and subsurface soils in the area of the proposed construction, in conformance with the Unified Soil Classification System (refer to Appendix A and Figure No. III). 2. Recommend site preparation procedures. 3. Recommend the allowable bearing capacities for the on-site dense natural soils or properly compacted fills. 4. Evaluate the settlement potential of the bearing soils under the proposed structural loads. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 2 5. Recommend preliminary foundation design information and provide active and passive earth pressures to be utilized in design of any proposed retaining walls and foundation structures. II. SITE DESCRIPTION The property is known as Assessor's Parcel No. 205-112-18-00, Lots 5 and 6, according to Recorded Map No. 1805, in the City of Carlsbad, County of San Diego, State of California. The rectangular site, consisting of approximately 1.13 acres, is located at 1080 Chestnut Avenue. The property is bordered on the north and west by similar residential properties; on the south by Chestnut Avenue; and on the east by Adams Street. Existing structures on the eastern portion of the site at the time of our investigation included two single-family residential structures and associated improvements. Small sheds are located on the undeveloped portion of the site and are used primarily for roadside flower and vegetable sales. Vegetation on the site consists of decorative shrubbery, grass, several mature pine trees, and flowers and vegetables for commercial sales. The property consists of a relatively level building pad with a gentle slope (gradient of approximately 5%) to the west. Approximate elevations across the site ranging from a high of 95 feet above mean seal level (MSL) at the northeast corner of the site, to a low of 80 feet above MSL at the southwest corner of the site (see Figure No. II). Survey information concerning actual elevations across the site was obtained from a topographic provided by the owner; dated March 13, 2001. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 3 III. FIELD INVESTIGATION Five exploratory handpits were placed on the site, in unbuilt areas and to obtain representative soil samples to define the soil profile across the property. The soil in the exploratory handpits was logged by our fleld representative, and samples were taken of the predominant soils throughout the fleld operation. Excavation logs have been prepared on the basis of our observations and the results have been summarized on Figure No. III. The predominant soils have been classifled in conformance with the Unifled Soil Classification System (referto Appendix A). IV. SOIL DESCRIPTION Our investigation and review of pertinent geologic maps and reports indicate that the medium dense to dense formational material of the Pleistocene-age terrace deposits underlie the entire site. The encountered soil proflle consists of up to 2 feet of cultivated topsoils overlying the terrace deposits. The encountered topsoil consists of up to 2 feet of dry to damp, dark brown, silty, flne to medium sand. These soils are considered to be of variable density, of low expansion potential, and not suitable in their current condition for bearing support. The flil soils are underlain by medium dense, moderately well cemented, terrace deposit formational material consisting of tan to red-brown, silty, flne to medium sand. The terrace deposit soils are, in general, of very low expansion potential and have excellent bearing strength characteristics. Refer to Figure Nos. Ill and IV for details. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 4 V. GROUNDWATER No groundwater was encountered in our exploratory excavations during our fleld investigation and we do not expect signiflcant problems to develop in the future — if our recommendations for proper drainage on the site are followed and proper drainage is maintained. The potential does exist for a perched water condition to develop if rainwater and irrigation waters are allowed to inflitrate through near-surface soils and encounter the less permeable formation, or flow beneath the structure along utility laterals if not properly sealed at footing penetrations. Preventative action such as placement of properly constructed subdrains around below-grade walls must be taken. Attempts must also be made to reduce the potential for a perched water condition by providing proper surface drainage. It should also be kept in mind that any required grading operations may change surface drainage patterns and/or reduce permeabilities due to the densiflcation of compacted soils. Such changes of surface and subsurface hydrologic conditions, plus irrigation of landscaping or signiflcant increases in rainfall, may result in the appearance of surface or near-surface water at locations where none existed previously. The damage from such water is expected to be localized and cosmetic in nature, if good positive drainage is implemented, as recommended in this report, during and at the completion of construction. It must be understood, however, that unless discovered during initial site exploration or encountered during construction, it is extremely difflcult to predict if or where perched or true groundwater conditions may appear in the future. When site flil or formational soils are flne-grained and of low permeability, water problems may not become apparent for extended periods of time. Riva Garden Residential Development Carlsbad, California Job No. 02-8291 Page 5 Water conditions, where suspected or encountered during construction, should be evaluated and remedied by the project civil and geotechnical consultants. The project developer and homeowner, however, must realize that additional post- construction appearances of groundwater may have to be dealt with on a site- speciflc basis. The alternative to the possible post-construction, site-speciflc appearance and resolution of subsurface water problems is the design and construction of extensive subdrain dewatering systems during the initial site development process. This option is usually selected when there is sufficient evidence during initial exploration or site grading to indicate such efforts are warranted. VI. LABORATORY TESTS AND SOIL INFORMATION Laboratory tests were performed on the disturbed and relatively undisturbed soil samples in order to evaluate their physical and mechanical properties and their ability to support the proposed residential structures. The following tests were conducted on the sampled soils: 1. Moisture Content (ASTM D2216-98) 2. Moisture/Density Relations (ASTM D1557-98, Method A) 3. Density Measurements (ASTM Dl 188-90 and D1556-98) 4. Mechanical Analysis (ASTM D422-98) The moisture content of a soil sample is a measure of the weight of water, expressed as a percentage ofthe dry weight ofthe sample. Riva Garden Residential Development Carlsbad, California Job No. 02-8291 Page 6 The relationship between the moisture and density of remolded soil samples gives qualitative information regarding the soil strength characteristics and compaction soil conditions to be anticipated during any future grading operation. The expansion potential of soils is determined utilizing the Uniform Building Code Test Method for Expansive Soils (UBC Standard No. 29-2). In accordance with the UBC (Table 18-1-B), expansive soils are classified as follows: EXPANSION INDEX POTENTIAL EXPANSION 0 to 20 Very low 21 to 50 Low 51 to 90 Medium 91 to 130 High Above 130 Very high Based on visual classiflcation, the on-site soils have a very low expansion potential, with an expansion index of less than 20. The Mechanical Analysis Test was used to aid in the classiflcation of the soils according to the Unified Soil Classiflcation System. Based on laboratory test data, our observations of the primary soil types on the project, and our previous experience with laboratory testing of similar soils, our Geotechnical Engineer had assigned conservative values for friction angle, coefflcient of friction, and cohesion to those soils that will have significant lateral support or bearing functions on the project. The assigned values are presented in Figure No. IV and have been utilized in the calculation of recommended bearing value as well as active and passive earth pressure for foundation design. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 7 VII. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based upon the practical fleld investigation conducted by our flrm, and resulting laboratory tests, in conjunction with our knowledge and experience with the soils in the City of Carlsbad. Our investigation revealed the site is underlain at depth by medium dense terrace deposit formational materials, with up to 2 feet of variable-density cultivated topsoil encountered in the proposed building areas. In their present condition, the topsoils will not provide a stable base for the proposed structures and improvements. As such, we recommend that the topsoils be removed to at least 2 feet, be scarified, moisture conditioned, and recompacted as part of site preparation prior to the addition of any new fill or structural improvements. In addition it is recommended that the proposed driveway area extending from Adams Street to Lot 4 be excavated to an approximate depth of 2 feet, scarifled, and recompacted as part of site preparation prior to the addition of any new flil or driveway improvements. To reduce differential movements associated with structures straddling cut/flll transitions, foundation excavations shall extend through compacted flil soils into the overlying formational materials or the entire pad shall be undercut to provide at least 1 foot of flil under the foundations. Slabs on-grade shall be founded either entirely on flil or entirely on cemented terrace, or have the compacted flil portion placed at a minimum of 95 percent relative compaction. A. Preparation of Soils for Site Development 1. The existing improvements and vegetation observed on the site must be removed prior to the preparation of the building pad and/or areas to receive Riva Garden Residential Development Job No. 02-8291 Carlsbad, California ^^9^ ^ new structural improvements. This includes any roots from existing trees and shrubbery that could cause damage to new foundations and slabs. In order to provide a uniform, firm soils base for the proposed structures and major improvements, the existing variable density topsoils located in the proposed building and improvement areas, and the proposed driveway area extending from Adams Street to Lot 4, and extending for a distance of at least 5 feet beyond the perimeter thereof (where possible), shall be excavated to expose flrm, native soil, or as per the indications of our field representative. This depth is expected to be approximately 2 to 272 feet. The excavated loose soils shall be cleaned of any debris and deleterious materials, watered to the approximate optimum moisture content, placed where needed to reach planned grades, and compacted to at least 90 percent of Maximum Dry Density, in accordance with ASTM D1557-98 standards. As previously stated, to reduce differential movements associated with structures straddling cut to fill transitions, foundation excavations shall extend through compacted flil soils into the overlying formational materials or the flil portion shall be compacted to at least 95 percent relative compaction. Additionally, slabs on-grade and foundations shall either be totally underlain by a minimum of 12 inches of compacted flil or have the flil portion of the cut/fill area compacted All placed at a minimum of 95 percent relative compaction. Any areas that are to support proposed improvements or retaining structures should be prepared in a like manner. Foundation bottoms shall consist entirely of dense formational material or combined with flil soils compacted to at least 95 percent of Maximum Dry Density. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 9 We do not anticipate that medium or highly expansive clay soils will be encountered during grading. Should such soils be encountered and used as flil, however, they shall be scarifled, moisture conditioned to at least 5 percent above optimum moisture content, and be compacted to at least 90 percent. 3. No uncontrolled flil soils shall remain on the site after completion of any future site work. In the event that temporary ramps or pads are constructed of uncontrolled fill soils, the loose fill soils shall be removed and/or recompacted prior to completion ofthe grading operation. 4. Any buried objects, abandoned utility lines, or particular soft soil areas, etc., which might be discovered in the construction areas, shall be removed and the excavation properly backfllled with approved on-site or imported fill soils and compacted to at least 90 percent of Maximum Dry Density. 5. Any backflll soils placed in utility trenches or behind retaining walls that support structures and other improvements (such as patios, sidewalks, driveways, pavements, etc.) shall be compacted to at least 90 percent of Maximum Dry Density. Backflll soils placed behind retaining walls and/or crawl space retaining walls shall be installed as early as the retaining walls are capable of supporting lateral loads. B. Desian Parameters for Proposed Foundations 6. For preliminary foundation design of new footings, based on the assumption that new footings will be placed at least 18 inches below lowest adjacent grade, we provide a preliminary allowable soil bearing capacity equal to 2,500 pounds per square foot (psf). This applies to footings at least 18 inches in Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 10 width. For wider and/or deeper footings, the allowable soil bearing capacity may be calculated based on the following equation: Qa = 1200D-I-700W where "Qa" is the allowable soil bearing capacity (in psf); "D" is the depth of the footing (in feet) as measured from the lowest adjacent grade; and "W" is the width ofthe footing (in feet). The allowable soil bearing capacity may be increased one-third for analysis including wind or earthquake loads. The maximum total allowable soil bearing capacity for dense Alls or natural formation is 6,000 psf. 7. The passive earth pressure of the encountered natural-ground soils and any properly compacted All soils (to be used for design of shallow foundation 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 foundations structure is essentially level for a distance of at least three times the total depth of the foundation. 8. A Coefflcient of Friction of 0.40 times the dead load may be used to calculate friction force between the bearing soils and concrete wall foundations or structure foundations and floor slabs. Riva Garden Residential Development Carlsbad, California Job No. 02-8291 Page 11 The following table summarizes site-speciflc seismic design criteria to calculate the base shear needed for the design of the residential structure. The design criteria was obtained from the Uniform Building Code (1997 edition). The coefficient values are based on the site soil proflle and the distance to the closest active fault. Parameter Value Reference Seismic Zone Factor, Z 0.40 Table 16-1 Soil Proflle Type Sc Table 16-J Seismic CoefAcient, Ca 0.40Na Table 16-Q Seismic CoefAcient, Cv 0.56Nv Table 16-R Near-Source Factor, Na 1.05 Table 16-S Near-Source Factor, Nv 1.22 Table 16-T Seismic Source Type B Table 16-U 10. Our experience indicates that, for various reasons, footings and slabs occasionally crack, causing ceramic tiles and brittle surfaces to become damaged. Therefore, we recommend that all conventional shallow footings and slabs-on-grade contain at least a minimum amount of reinforcing steel to reduce the separation of cracks, should they occur. 10.1 A minimum of steel for continuous footings should include at least four No. 4 steel bars continuous, with two bars near the bottom of the footing and two bars near the top. A minimum clearance of 3 inches shall be maintained between steel reinforcement and the top, bottom or sides of the footing. 10.2 Isolated square footings should contain, as a minimum, a grid ofthree No. 4 steel bars on 12-inch centers, both ways, with no less than three bars each way. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 12 10.3 Interior floor slabs should be a minimum of 4 inches actual thickness • and be reinforced with No. 3 bars on 18-inch centers, both ways, placed at midheight in the slab. Slabs at the main floor level shall be underlain by a 2-inch-thick layer of clean sand (S.E. = 30 or greater) overlying a moisture retardant membrane over 2 Inches of sand. Slab subgrade soil shall be verlAed by a Geotechnical Exploration, Inc. representative to have the proper moisture content within 48 hours prior to placement of the vapor barrier and pouring of concrete. We recommend the project Civil/Structural Engineer incorporate isolation joints and sawcuts to at least one-fourth the thickness ofthe slab in any Aoor designs. The joints and cuts, if properly placed, should reduce the potential for and help control floor slab cracking. It is recommended that concrete shrinkage joints be placed no farther than approximately 20 feet, and also at re-entrant corners. However, due to a number of reasons (such as base preparation, construction techniques, curing procedures, and normal shrinkage of concrete), some cracking of slabs can be expected. Basement slabs may be provided with a higher percent of steel reinforcing to eliminate control joints. NOTE: The project Civil/Structural Engineer shall review all reinforcing schedules. The reinforcing minimums recommended herein are not to be construed as structural designs, but merely as minimum safeguards to reduce possible crack separations. Based on our laboratory test results and our experience with the soil types on the subject site, the dense natural soils and properly compacted flil soils should experience differential angular rotation of less than 1/240 under the recommended allowable loads. The maximum differential settlement across Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 13 the structure and footings when founded on properly compacted fill or dense natural formation shall be on the order of 1 inch. 11. As a minimum for protection of on-site improvements, it is recommended that all nonstructural concrete slabs (such as patios, sidewalks, etc.), be founded on properly compacted and tested fill or dense native formation and underlain (if applicable) by 3 inches of leveling clean sand, with 6x6-6/6 welded wire mesh at the center of the slab, and contain adequate isolation and control joints. The performance of on-site improvements can be greatly affected by soil base preparation and the quality of construction. It is therefore important that all improvements are properly designed and constructed for the existing soil conditions. The improvements should not be built on loose soils or fills placed without our observations and testing. Any rigid improvements founded on the existing loose surface soils can be expected to undergo movement and possible damage and is therefore not recommended, Geotechnical Exploration, Inc. takes no responsibility for the performance of the improvements built or loose or inadequately compacted flils. Any exterior area to receive concrete improvements shall be verifled for compaction and moisture within 48 hours prior to concrete placement. For exterior slabs with the minimum shrinkage reinforcement, control joints shall be placed at spaces no farther than 15 feet apart and at re-entrant corners. Control joints in exterior slabs shall be sealed with elastomeric joint sealant. The sealant shall be inspected every 6 months and be properly maintained. 12. Driveway pavement, consisting of Portland cement concrete at least 5 inches in thickness, may be placed on properly compacted subgrade soils. The Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 14 concrete shall be at least 3,250 psi compressive strength, with control joints no farther than 15 feet apart. Pavement joints shall be properly sealed with the permanent joint sealant, as required in sections 201.3.6 through 201.3.8 of the Standard Speciflcations for Public Work Construction, 2000 Edition. All control joints shall penetrate at least one-quarter the thickness of the slab, and shall be placed within 12 hours after concrete placement. Asphalt concrete pavement for access or interior roads may utilize a preliminary estimate (based on an assumed R-value of 20 and a TI of 55) to consist of 3 inches of asphalt on 8 inches of Class II base. Final pavement section design is to be verified, with actual R-value tests performed after street rough grading is completed. C. Floor Slab Vapor Transmission 13. Vapor moisture can cause some problems on moisture sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor, in addition to mildew and staining on slabs, walls and carpets. 14. The common practice in Southern California is to place vapor retarders made of PVC, or of polyethylene. PVC retarders are made in thickness ranging from 10- to 60-mil. Polyethylene retarders, called visqueen, range from 5- to 10-mil in thickness. The thicker the plastic, the stronger the resistance will be against puncturing. 15. Although polyethylene (visqueen) products are most commonly used, products such as Vaporshield possess much higher tensile strength and are more speciflcally designed for and intended to retard moisture transmission into concrete slabs. The use of Vaporshield or equivalent is highly Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 15 recommended when a structure is intended for moisture-sensitive floor coverings or uses. 16. The vapor retarders need to have joints lapped and sealed with mastic or manufacturer's recommended tape for additional protection. To provide some protection to the moisture retarder, a layer of at least 2 inches of clean sand on top and 2 inches at the bottom shall also be provided. No heavy equipment, stakes or other puncturing instruments shall be used on top of the liner before or during concrete placement. In actual practice, stakes are often driven through the retarder material, equipment is dragged or rolled across the retarder, overlapping or jointing is not properly implemented, etc. All these construction deAciencies reduce the retarder's effectiveness. The vapor retarders are not waterproof. They are intended to help prevent or reduce capillary migration of vapor through the soil into the pores of concrete slabs. Other waterprooAng systems must supplement vapor retarders if full waterprooAng is desired. The owner should be consulted to determine the speciflc level of protection required in particular, at the basement level. D. Retainina Walls 17. The active earth pressure (to be utilized in the design of any cantilever retaining walls, utilizing on-site or imported very low expansive to low expansive soils [EI less than 50] as backflll) shall be based on an Equivalent Fluid Weight of 38 pounds per cubic foot (for level backflll only). For 2.0:1.0 sloping backflll, the equivalent fluid weight shall be not less than 52 pcf utilizing low expansive backflll. Clayey soils shall not be used as wall backfill material, except as capping material in the upper 1 foot. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 16 In the event that a retaining wall is to be designed for a restrained condition (such as for basement retaining walls), 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 soil pressure produced by any footings, improvements, or any other surcharge placed within a horizontal distance equal to the height ofthe retaining portion ofthe wall shall be included in the wall design pressure. Any loads placed on the active wedge behind the wall shall be included in the design by multiplying the load weight by a factor of 0.32. For restrained walls, use a factor equal to 0.52. The retaining wall and/or building retaining wall plans shall indicate that the walls shall be backfllled with very low to low expansive soils (EI=less than 50). 18. Proper subdrains and free-draining backwall material or geofabric drainage shall be installed behind all retaining walls (in addition to proper waterprooflng) on the subject project. Geotechnical Exploration, Inc. will assume no liability for damage to structures or improvements that is attributable to poor drainage. The architectural plans shall clearly indicate that the subdrains for any lower-level walls shall be placed at an elevation at least 1 foot below the bottom of the interior slabs being protected. At least 0.5-percent fall shall be provided for the subdrain. The subdrain shall be placed in an envelope of crushed rock gravel up to 1 inch in maximum diameter, and be wrapped with MiraA 140N fliter or equivalent. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 17 E. Site Drainage Considerations 19. Adequate measures shall be taken to properly flnish-grade the building site after the structures and other improvements are in place. Drainage waters from this site and adjacent properties are to be directed away from the 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 structures, with 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 undermining and possible differential settlement of the structure or other improvements on the site. Currently, the Uniform Building Code requires a minimum 2-percent surface gradient for proper drainage of building pads unless waived by the building offlciai. Concrete pavement may have a minimum gradient of 0.5-percent. In addition, appropriate erosion control measures shall be taken at all times during and after construction to prevent surface runoff waters from entering footing excavations or ponding on flnished building pad areas. 20. Planter areas, flower beds and planter boxes shall be sloped to drain away from the foundations, footings, and floor slabs at a gradient of at least 5 percent within 5 feet from the perimeter walls. Any planter areas adjacent to the buildings or surrounded by concrete improvements shall be provided with sufficient area drains to help with rapid runoff disposal. No water shall be allowed to pond adjacent to the buildings or other improvements. Planter boxes shall be constructed with a closed bottom and a subsurface drain. Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 18 installed in gravel, with the direction of subsurface and surface flow away from the slopes, foundations, footings, and floor slabs, to an adequate drainage facility. Sufflcient area drains and proper surface gradient shall be provided throughout the project. Roof gutter and downspouts shall be tied to storm drain lines. F. General Recommendations 21. Following placement of any concrete floor slabs, sufflcient 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 Anish floor materials. 22. Where not superseded by speciflc recommendations presented in this report, trenches, excavations and temporary slopes at the subject site shall be constructed in accordance with Title 8, Construction Safety Orders, issued by Cal-OSHA. 23. In order to minimize any work delays at the subject site during site development, this flrm should be contacted 24 hours prior to any need for observation of footing excavations or fleld density testing of compacted flil soils. If possible, placement of formwork and steel reinforcement in footing excavations should not occur prior to observing the excavations; in the event that our observations reveal the need for deepening or redesigning foundation structures at any locations, any formwork or steel reinforcement in the affected footing excavation areas would have to be removed prior to correction of the observed problem (i.e., deepening the footing excavation, recompacting soil in the bottom ofthe excavation, etc.) Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 19 VIII. GRADING NOTES Any required grading operations shall be performed in accordance with the General Earthwork Speciflcations (Appendix B) and the requirements of the City of Carlsbad Grading Ordinance. 24. Geotechnical Exploration, Inc. recommends that we be asked to verify the actual soil conditions revealed during site grading work and footing excavation to be as anticipated in this "Report of Preliminary Geotechnical Investigation" for the project. In addition, the compaction of any All soils placed during site grading work must be tested by the soil engineer. It is the responsibility of the grading contractor to comply with the requirements on the grading plans and the local grading ordinance. All retaining wall and trench backAII that will support structures or rigid improvements shall be properly compacted. Geotechnical Exploration, Inc. will assume no liability for damage occurring due to improperly or uncompacted backflll placed without our observations and testing. 25. It is the responsibility of the owner and/or developer to ensure that the recommendations summarized in this report are carried out in the fleld operations and that our recommendations for design of this project are incorporated in the structural plans. We shall be provided with the opportunity to review the project plans once they are available, to see that our recommendations are adequately incorporated in the plans. 26. This flrm does not practice or consult in the fleld of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if Riva Garden Residential Development Job No. 02-8291 Carlsbad, California Page 20 he considered any of the recommended actions presented herein to be unsafe. IX. LIMITATIONS Our conclusions and recommendations have been based on all available data obtained from our fleld investigation and laboratory analysis, as well as our experience with the soils and formational materials located in the City of Carlsbad. Of necessity, we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is, therefore, necessary that all observations, conclusions, and recommendations be verifled at the time grading operations begin or when footing excavations are placed. In the event discrepancies are noted, additional recommendations may be issued, if required. The work performed and recommendations presented herein are the result of an investigation and analysis that meet the contemporary standard of care in our profession within the County of San Diego. No warranty is provided. This report should be considered valid for a period of two (2) years, and is subject to review by our flrm following that time. If signiflcant modiflcations are made to the building plans, especially with respect to the height and location of any proposed structures, this report must be presented to us for immediate review and possible revision. The flrm of Geotechnical Exploration, Inc. shall not be held responsible for changes to the physical condition of the property, such as addition of flil soils or changing drainage patterns, which occur subsequent to issuance of this report and the changes are made without our observations, testing, and approval. Riva Garden Residential Development Carlsbad, California Job No. 02-8291 Page 21 Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 02-8291 will expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. Jay "K^" Keiser Project Coordinator JKH/JAC/pj Jaime A. Cerros, P.E. R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer 2 (; No. 002 I Exp. ^ 30/ VICINITY MAP DR BASSWOOD <X ^ 1300 Mi tim , ^ PARK J -J ' BSI&ILY \ CHASE mu) CHESTNUT^ ?^ .0 JR HS r\ mi Riva Gardens Residential Development 1080 Chestnut Avenue Carlsbad, CA. Figure No. I Job No. 02-8291 '"EQUIPMENT Hand Tools DIMENSION & TYPE OF EXCAVATION 2' X 2' X 2' Handpit DATE LOGGED 7-25-02 SURFACE ELEVATION 184' Mean Sea Level GROUNDWATER DEPTH Not Encountered LOGGED BY JKH t •I Q-LU a FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size, Density, Moisture, Cola) UJ cc 3fc UJ -LU s ce QI O o s Q ^ o 38 ca o LU </) U- X SILTY FINE TO MEDIUM SAND, w/ some roots. Loose to medium dense. Dry to damp. Dark brown. CULTIVATED TOPSOIL SM 8.0 110.3 87 2- 4- SILTY FINE TO MEDIUM SAND, moderately well cemented. Medium dense. Damp. Red-brown. TERRACE DEPOSITS (Qt) SM 11.0 127.0 No groundwater encountered. Bottom @ 5' JL WATERTABLE LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE H] SAND CONBF.D.T. ^ STANDARD PENETRATION TEST JOB NAME Riva Gardens Residential Development SITE LOCATION 1080 Chestnut Avenue, Carlsbad, Califomia JOB NUMBER 02-8291 FIGURE NUMBER Ilia REVIEWED BY JAC GCOiCClHIfCSl Exploratfon, Inc. LOG No. HP-1 EQUIPMENT Hand Tools DIMENSION & TYPE OF EXCAVATION 2' X 2' X 2' Handpit DATE LOGGED 7-25-02 SURFACE ELEVATION ± 87* Mean Sea Level GROUNDWATER DEPTH Not Encountered LOGGED BY JKH X 1— Q_ UJ Q O FIELD DESCRIPTION AND CU\SSIFICAT10N DESCRIPTION AND REMARKS (Grain size. Density, Moisture, Color) in ^ UJ 5: o o s <t UJ o >-ci CO _J u b „ UJ to li SILTY FINE TO MEDIUM SAND, w/ some roots. Loose to medium dense. Dry to damp. Dark brown. CULTIVATED TOPSOIL SM 1 - SILTY FINE TO MEDIUM SAND, moderately well cemented. Medium dense. Damp. Tan to red-brown. TERRACE DEPOSITS (Qt) SM 3- No groundwater encountered. Bottom @ 5' 6- I WATERTABLE IEI LOOSE BAG SAMPLE [T| IN-PLACE SAMPLE • DRIVE SAMPLE \s} SAND CONeF.D.T. ^ ^ STANDARD PENETRATION TEST JOBNAME Riva Gardens Residential Deveiopment I WATERTABLE IEI LOOSE BAG SAMPLE [T| IN-PLACE SAMPLE • DRIVE SAMPLE \s} SAND CONeF.D.T. ^ ^ STANDARD PENETRATION TEST SITE LOCATION 1080 Chestnut Avenue, Carlsbad, Califomia I WATERTABLE IEI LOOSE BAG SAMPLE [T| IN-PLACE SAMPLE • DRIVE SAMPLE \s} SAND CONeF.D.T. ^ ^ STANDARD PENETRATION TEST JOB NUMBER 02-8291 REVIEWED BY JAC Ifr4&£ Geotectinical LOG No HP-2 J I WATERTABLE IEI LOOSE BAG SAMPLE [T| IN-PLACE SAMPLE • DRIVE SAMPLE \s} SAND CONeF.D.T. ^ ^ STANDARD PENETRATION TEST FIGURE NUMBER lllb T cxpiorauoii, inc. LOG No HP-2 J ''EQUIPMENT Hand Tools DIMENSION & TYPE OF EXCAVATION 2' X 2' X 2' Handpit DATE LOGGED ^ 7-25-02 SURFACE ELEVATION ±81' Mean Sea Level GROUNDWATER DEPTH Not Encountered LOGGED BY JKH X (— Q-UJ O FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size. Density, Moisture, Color) UJ ct Is CL Z -S, UJ S IT ZD ZD Q_ O o s Q 38 CO o o d _ UJ UD ;r' LU S; X SILTY FINE TO MEDIUM SAND, wl some roots. Loose to medium dense. Dry to damp. Dark brown. CULTIVATED TOPSOIL SM 1 - 2- SiLTY FINE TO MEDIUM SAND, moderately well cemented. Medium dense. Damp. Tan to red-brown. TERRACE DEPOSITS (Qt) SM 11" 3- No groundwater encountered. Bottom @ 4" I WATERTABLE ^ LOOSE BAG SAMPLE E IN-PLACE SAMPLE • DRIVE SAMPLE m SAND CONE/F.D.T. ^ STANDARD PENETRATION TEST JOB NAME Riva Gardens Residential Development I WATERTABLE ^ LOOSE BAG SAMPLE E IN-PLACE SAMPLE • DRIVE SAMPLE m SAND CONE/F.D.T. ^ STANDARD PENETRATION TEST SITE LOCATION 1080 Chestnut Avenue, Carlsbad, Califomia I WATERTABLE ^ LOOSE BAG SAMPLE E IN-PLACE SAMPLE • DRIVE SAMPLE m SAND CONE/F.D.T. ^ STANDARD PENETRATION TEST JOB NUMBER 02-8291 REVIEWED BY JAC Geotectinical LOG No. HP-3 I WATERTABLE ^ LOOSE BAG SAMPLE E IN-PLACE SAMPLE • DRIVE SAMPLE m SAND CONE/F.D.T. ^ STANDARD PENETRATION TEST FIGURE NUMBER llic LOG No. HP-3 '^EQUIPMENT Hand Tools DIMENSION & TYPE OF EXCAVATION 2' X 2' X 2' Handpit DATE LOGGED ^ 7-25-02 SURFACE ELEVATION ± 86' Mean Sea Level GROUNDWATER DEPTH Not Encountered LOGGED BY JKH lil FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size. Density, Moisture, Color) UJ cc 9 => o 5 CO Q_ Z. ZD CO CL O O S o ^3 38 Q CD „ UJ CO —I UJ CL X <g CO =i SILTY FINE TO MEDIUM SAND, w/ some roots. Loose to medium dense. Dry to damp. Dark brown. CULTIVATED TOPSOIL SM 2-i 3- 5- SILTY FINE TO MEDIUM SAND, moderately well cemented. Medium dense. Damp. Red-brown. TERRACE DEPOSITS (Qt) SM No groundwater encountered. Bottom @ 4' WATERTABLE ^ LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE [s] SAND CONeF.D.T. ^ STANDARD PENETRATION TEST JOB NAME Riva Gardens Residential Development WATERTABLE ^ LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE [s] SAND CONeF.D.T. ^ STANDARD PENETRATION TEST SITE LOCATION 1080 Chestnut Avenue, Carlsbad, Califomia WATERTABLE ^ LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE [s] SAND CONeF.D.T. ^ STANDARD PENETRATION TEST JOB NUMBER 02-8291 FIGURE NUMBER llld REVIEWED BY JAC llrl^-S Geotectinical ^IW ^ Exploratton, Inc LOG No. HP-4 WATERTABLE ^ LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE [s] SAND CONeF.D.T. ^ STANDARD PENETRATION TEST JOB NUMBER 02-8291 FIGURE NUMBER llld LOG No. HP-4 ''EQUIPMENT Hand Tools DIMENSION & TYPE OF EXCAVATION 2' X 2' X 2- Handpit DATE LOGGED ^ 7-25-02 SURFACE ELEVATION + 90' Mean Sea Level GROUNDWATER DEPTH Not Encountered LOGGED BY JKH o ri tn FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS (Grain size, Density, Moisture, Color) UJ cc 5:5 SI Ul 5_ s cc ZD ZD K. o o s I CD O o d „ Ul CO —i Ul CL X S O SILTY FINE TO MEDIUM SAND, w/ abundant roots and some rock fragments. Loose to medium dense. Dry to damp. Dark brown. CULTIVATED TOPSOIL SM 1 - 2- SILTY FINE TO MEDIUM SAND, moderately well cemented. Medium dense. Damp. Red-brown. TERRACE DEPOSITS (Qt) SM No groundwater encountered. Bottom @ 4' 5- i WATERTABLE Kl LOOSE BAG SAMPLE [T] IN-PLACE SAMPLE • DRIVE SAMPLE [s] SAND CONE/F.D.T. ^ STANDARD PENETRATION TEST JOB NAME Riva Gardens Residential Deveiopment SITE LOCATION 1080 Chestnut Avenue, Carlsbad, Califomia JOB NUMBER 02-8291 FIGURE NUMBER Hie REVIEWED BY JAC Geotectinical E3g»teratlon. inc. LOG No. HP-5 Legend LP Chestnut Avenue Refsr«ne«! This Plot Plan iua» praparad rrom an sxlstrng plan provrdsd by tha clfant datad Mardn 13, 20»I and from on-«rta riald raconnare»anca parfomsd by Q£\. NOTE: This Plot Plan is not to be used for legal purposes. Locations and dimensions are approxi- mate. Actual property dimensions and locations of utilities may be obtained from the Approved Building Plans or tho "As-Built" Grading Plans. HP-4 cr o ASSUMED PROPERTY BOUNDARY APPROXIMATE LOCATION OF EXISTING STRUCTURE APPROXIMATE LOCATION OF EXPLORATORY TEST PIT EXISTING TOPOGRAPY (feet) EXISTING TREE Scale:!" = 30' PLOT PLAN Riva Gardens Residential Dewe/opment 7080 Ctiestnut Avenue Cartsbsxi, CA. Figure No. II Job No. 02-8291 4WN Geotechnical 02-8291-P Augusf2002 ^ Exploration, Inc. 140 130 120 110 100 90 80 LABORATORY SOIL DATA SUMMARY MAXIMUM DRY DENSITY (pcf) OPTIMUM MOISTURE CONTENT (X) 127 11.0 DIRECT SHEAR TEST DATA 1 2 3 APPARENT COHESION (psf) 100 APPARENT FRICTION ANGLE 32° -'- AqsinnpH Val IIP Gravel Sand Fines Coai-se To Medi um Fi ne Clay U.S. standard sieve sizes ooo go (VJ o d o o o o 100 80 6C a 40 20 1 1 1 I- :G _[_ I 1 1 l.L.__ ... T [ O kO .—I ' ' o a^ •—• ^ CO *T ^ O O O O o o GFJMN DIAMEI-K, MM 2.70 2.60. 2.50-^ SPECIFIC GRAVITY 10 20 30 LABORATORY COMPACTION TEST ZERO AIR VOIDS CURVES SOIL TYPE SOiL CLASSIFICATION BORING No. TRENCH No. DEPTH 1 SILTY FINE TO MEDIUM SAND. Dark brown. TOPSOIL HP-1 1 ' 2 3 SWELL TEST DATA 1 2 3 INITIAL DRY DENSITY (pcf) - INITIAL MATER CONTENT {%) - LOAD (psf) - PERCENT SWELL ^|^ <20 FIGURE NUMBER IV JOB NUMBER 02-8291 (i4 (10 ID APPENDIX A UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION Coarse-grained (More than half of material is larger than a No. 200 sieve) GRAVELS, CLEAN GRAVELS (More than half of coarse fraction is larger than No. 4 sieve size, but smaller than 3") GRAVELS WITH FINES (Appreciable amount) SANDS, CLEAN SANDS (More than half of coarse fraction IS smaller than a No. 4 sieve) SANDS WITH FINES (Appreciable amount) GW Well-graded gravels, gravel and sand mixtures, little or no fines. GP Poorly graded gravels, gravel and sand mixtures, little or no fines. GC Clay gravels, poorly graded gravel-sand-siit mixtures SW Well-graded sand, gravelly sands, little or no fines SP Poorly graded sands, gravelly sands, little or no fines. SM Silty sands, poorly graded sand and silty mixtures. SC Clayey sands, poorly graded sand and clay mixtures. FINE-GRAINED (More than half of material is smaller than a No. 200 sieve) SILTS AND CLAYS Liquid Limit Less than 50 Liquid Limit Greater than 50 HIGHLY ORGANIC SOILS ML Inorganic silts and very fine sands, rock flour, sandy silt and clayey-silt sand mixtures with a slight plasticity. CL Inorganic clays of low to medium plasticity, gravelly clays, silty clays, clean clays. OL Organic silts and organic silty clays of low plasticity. MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. CH Inorganic clays of high plasticity, fat clays. OH Organic clays of medium to high plasticity. PT Peat and other highly organic soils APPENDIX B GENERAL EARTHWORK SPECIFICATIONS General The objective of these specifications is to properly establish procedures for the clearing and preparation of the existing natural ground or properly compacted fill to receive new fill; for the selection of the fill material; and for the fill compaction and testing methods to be used. Scope of Work The earthwork includes all the activities and resources provided by the contractor to construct in a good workmanlike manner all the grades of the filled areas shown in the plans. The major items of work covered in this section include all clearing and grubbing, removing and disposing of materials, preparing areas to be filled, compacting of fill, compacting of backfills, subdrain installations, and all other work necessary to complete the grading of the filled areas. Site Visit and Site Investigation 1. The contractor shall visit the site and carefully study it, and make all inspections necessary in order to determine the full extent of the work required to complete all grading in conformance with the drawings and specifications. The contractor shall satisfy himself as to the nature, location, and extent of the work conditions, the conformation and condition of the existing ground surface; and the type of equipment, labor, and facilities needed prior to and during prosecution of the work. The contractor shall satisfy himself as to the character, quality, and quantity of surface and subsurface materials or obstacles to be encountered. Any inaccuracies or discrepancies between the actual field conditions and the drawings, or between the drawings and specifications, must be brought to the engineer's attention in order to clarify the exact nature of the work to be performed. 2. A soils investigation report has been prepared for this project by GEI. It is available for review and should be used as a reference to the surface and subsurface soil and bedrock conditions on this project. Any recommendations made in the report of the soil investigation or subsequent reports shall become an addendum to these specifications. Authoritv of the Soils Engineer and Enqineerinq Geologist The soils engineer shall be the owner's representative to observe and test the construction of fills. Excavation and the placing of fill shall be under the observation of the soils engineer and his/her representative, and he/she shall give a written opinion regarding conformance with the specifications upon completion of grading. The soils engineer shall have the authority to cause the removal and replacement of porous topsoils, uncompacted or improperly compacted fills, disturbed bedrock materials, and soft alluvium, and shall have the authority to approve or reject materials proposed for use in the compacted fill areas. The soils engineer shall have, in conjunction with the engineering geologist, the authority to approve the preparation of natural ground and toe-of-fill benches to receive fill material. The engineering geologist shall have the authority to evaluate the stability of the existing or proposed slopes, and to evaluate the necessity of remedial measures. If any unstable condition is being created by cutting or filling, the engineering geologist and/or soils engineer shall advise the contractor and owner immediately, and prohibit grading in the affected area until such time as corrective measures are taken. The owner shall decide all questions regarding: (1) the interpretation of the drawings and specifications, (2) the acceptable fulfillment of the contract on the part of the contractor, and (3) the matter of compensation. Appendix B Page 2 Clearinq and Grubbinq 1. Clearing and grubbing shall consist of the removal from all areas to be graded of all surface trash, abandoned improvements, paving, culverts, pipe, and vegetation (including - but not limited to - heavy weed growth, trees, stumps, logs and roots larger than 1-inch in diameter). 2. All organic and inorganic materials resulting from the clearing and grubbing operations shall be collected, piled, and disposed of by the contractor to give the cleared areas a neat and finished appearance. Burning of combustible materials on-site shall not be permitted unless allowed by local regulations, and at such times and in such a manner to prevent the fire from spreading to areas adjoining the property or cleared area. 3. It is understood that minor amounts of organic materials may remain in the fill soils due to the near impossibility of complete removal. The amount remaining, however, must be considered negligible, and in no case can be allowed to occur in concentrations or total quantities sufficient to contribute to settlement upon decomposition. Preparation of Areas to be Filled 1. After clearing and grubbing, all uncompacted or improperly compacted fills, soft or loose soils, or unsuitable materials, shall be removed to expose competent natural ground, undisturbed bedrock, or properly compacted fill as indicated in the soils investigation report or by our field representative. Where the unsuitable materials are exposed in final graded areas, they shall be removed and replaced as compacted fill. 2. The ground surface exposed after removal of unsuitable soils shall be scarified to a depth of at least 6 inches, brought to the specified moisture content, and then the scarified ground compacted to at least the specified density. Where undisturbed bedrock is exposed at the surface, scarification and recompaction shall not be required. 3. All areas to receive compacted fill, including all removal areas and toe-of-fill benches, shall be observed and approved by the soils engineer and/or engineering geologist prior to placing compacted fill. 4. Where fills are made on hillsides or exposed slope areas with gradients greater than 20 percent, horizontal benches shall be cut into firm, undisturbed, natural ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer is placed and compacted on a horizontal plane. The initial bench at the toe of the fill shall be at least 10 feet in width on firm, undisturbed, natural ground at the elevation of the toe stake placed at the bottom of the design slope. The engineer shall determine the width and frequency of all succeeding benches, which will vary with the soil conditions and the steepness of the slope. Ground slopes flatter than 20 percent (5.0:1.0) shall be benched when considered necessary by the soils engineer. Fill and Backfill Material Unless otherwise specified, the on-site material obtained from the project excavations may be used as fill or backfill, provided that all organic material, rubbish, debris, and other objectionable material contained therein is first removed. In the event that expansive materials are encountered during foundation excavations within 3 feet of finished grade and they have not been properly processed, they shall be entirely removed or thoroughly mixed with good, granular material before incorporating them in fills. No footing shall be allowed to bear on soils which, in the opinion of the soils engineer, are detrimentally expansive - unless designed for this clayey condition. However, rocks, boulders, broken Portland cement concrete, and bituminous-type pavement obtained from the project excavations may be permitted in the backfill or fill with the following limitations: Appendix B Page 3 1. The maximum dimension of any piece used in the top 10 feet shall be no larger than 6 inches. 2 Clods or hard lumps of earth of 6 inches in greatest dimension shall be broken up before compacting the material in fill. 3. If the fill material originating from the project excavation contains large rocks, boulders, or hard lumps that cannot be broken readily, pieces ranging from 6 inches in diameter to 2 feet in maximum dimension may be used in fills below final subgrade if all pieces are placed in such a manner (such as windrows) as to eliminate nesting or voids between them. No rocks over 4 feet will be allowed in the fill. 4. Pieces larger than 6 inches shall not be placed within 12 inches of any structure. 5. Pieces larger than 3 inches shall not be placed within 12 inches of the subgrade for paving. 6. Rockfills containing less than 40 percent of soil passing 3/4-inch sieve may be permitted in designated areas. Specific recommendations shall be made by the soils engineer and be subject to approval by the city engineer. 7. Continuous observation by the soils engineer is required during rock placement. 8. Special and/or additional recommendations may be provided in writing by the soils engineer to modify, clarify, or amplify these specifications. 9. During grading operations, soil types other than those analyzed in the soil investigation report may be encountered by the contractor. The soils engineer shall be consulted to evaluate the suitability of these soils as fill materials. Placinq and Compactinq Fill Material 1. After preparing the areas to be filled, the approved fill material shall be placed in approximately horizontal layers, with lift thickness compatible to the material being placed and the type of equipment being used. Unless otherwise approved by the soils engineer, each layer spread for compaction shall not exceed 8 inches of loose thickness. Adequate drainage of the fill shall be provided at all times during the construction period. 2. When the moisture content of the fill material is below that specified by the engineer, water shall be added to it until the moisture content is as specified. 3. When the moisture content of the fill material is above that specified by the engineer, resulting in inadequate compaction or unstable fill, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is as specified. 4. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to not less than the density set forth in the specifications. Compaction shall be accomplished with sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other approved types of acceptable compaction equipment. Equipment shall be of such design that it will be able to compact the fill to the specified relative compaction. Compaction shall cover the entire fill area, and the equipment shall make sufficient trips to ensure that the desired density has been obtained throughout the entire fill. At locations where it would be impractical due to inaccessibility of rolling compacting equipment, fill layers shall be compacted to the specified requirements by hand-directed compaction equipment. Appendix B Page 4 5. When soil types or combination of soil types are encountered which tend to develop densely packed surfaces as a result of spreading or compacting operations, the surface of each layer of fill shall be sufficiently roughened after compaction to ensure bond to the succeeding layer. 6. Unless otherwise specified, fill slopes shall not be steeper than 2.0 horizontal to 1.0 vertical. In general, fill slopes shall be finished in conformance with the lines and grades shown on the plans. The surface of fill slopes shall be overfilled to a distance from finished slopes such that it will allow compaction equipment to operate freely within the zone of the finished slope, and then cut back to the finished grade to expose the compacted core. Alternate compaction procedures include the backrolling of slopes with sheepsfoot rollers in increments of 3 to 5 feet in elevation gain. Alternate methods may be used by the contractor, but they shall be evaluated for approval by the soils engineer. 7. Unless otherwise specified, all allowed expansive fill material shall be compacted to a moisture content of approximately 2 to 4 percent above the optimum moisture content. Nonexpansive fill shall be compacted at near-optimum moisture content. All fill shall be compacted, unless otherwise specified, to a relative compaction not less than 95 percent for fill in the upper 12 inches of subgrades under areas to be paved with asphalt concrete or Portland concrete, and not less than 90 percent for other fill. The relative compaction is the ratio of the dry unit weight of the compacted fill to the laboratory maximum dry unit weight of a sample of the same soil, obtained in accordance with A.S.T.M. D-1557 test method. 8. The observation and periodic testing by the soils engineer are intended to provide the contractor with an ongoing measure of the quality of the fill compaction operation. It is the responsibility of the grading contractor to utilize this information to establish the degrees of compactive effort required on the project. More importantly, it is the responsibility of the grading contractor to ensure that proper compactive effort is applied at all times during the grading operation, including during the absence of soils engineering representatives. Trench Backfill 1. Trench excavations which extend under graded lots, paved areas, areas under the influence of structural loading, in slopes or close to slope areas, shall be backfilled under the observations and testing of the soils engineer. All trenches not falling within the aforementioned locations shall be backfilled in accordance with the City or County regulating agency specifications. 2. Unless otherwise specified, the minimum degree of compaction shall be 90 percent of the laboratory maximum dry density. 3. Any soft, spongy, unstable, or other similar material encountered in the trench excavation upon which the bedding material or pipe is to be placed, shall be removed to a depth recommended by the soils engineer and replaced with bedding materials suitably densified. Bedding material shall first be placed so that the pipe is supported for the full length of the barrel with full bearing on the bottom segment. After the needed testing of the pipe is accomplished, the bedding shall be completed to at least 1 foot on top of the pipe. The bedding shall be properly densified before backfill is placed. Bedding shall consist of granular material with a sand equivalent not less than 30, or other material approved by the engineer. 4. No rocks greater than 6 inches in diameter will be allowed in the backfill placed between 1 foot above the pipe and 1 foot below finished subgrade. Rocks greater than 2.5 inches in any dimension will not be allowed in the backfill placed within 1 foot of pavement subgrade. Appendix B Page 5 5. Material for mechanically compacted backfill shall be placed in lifts of horizontal layers and properly moistened prior to compaction. In addition, the layers shall have a thickness compatible with the material being placed and the type of equipment being used. Each layer shall be evenly spread, moistened or dried, and then tamped or rolled until the specified relative compaction has been attained. 6. Backfill shall be mechanically compacted by means of tamping rollers, sheepsfoot rollers, pneumatic tire rollers, vibratory rollers, or other mechanical tampers. Impact-type pavement breakers (stompers) will not be permitted over clay, asbestos cement, plastic, cast iron, or nonreinforced concrete pipe. Permission to use specific compaction equipment shall not be construed as guaranteeing or implying that the use of such equipment will not result in damage to adjacent ground, existing improvements, or improvements installed under the contract. The contractor shall make his/her own determination in this regard. 7. Jetting shall not be permitted as a compaction method unless the soils engineer allows it in writing. 8. Clean granular material shall not be used as backfill or bedding in trenches located in slope areas or within a distance of 10 feet of the top of slopes unless provisions are made for a drainage system to mitigate the potential buildup of seepage forces into the slope mass. Observations and Testing 1. The soils engineers or their representatives shall sufficiently observe and test the grading operations so that they can state their opinion as to whether or not the fill was constructed in accordance with the specifications. 2. The soils engineers or their representatives shall take sufficient density tests during the placement of compacted fill. The contractor should assist the soils engineer and/or his/her representative by digging test pits for removal determinations and/or for testing compacted fill. In addition, the contractor should cooperate with the soils engineer by removing or shutting down equipment from the area being tested. 3. Fill shall be tested for compliance with the recommended relative compaction and moisture conditions. Field density testing should be performed by using approved methods by A.S.T.M., such as A.S.T.M. D1556, D2922, and/or D2937. Tests to evaluate density of compacted fill should be provided on the basis of not less than one test for each 2-foot vertical lift of the fill, but not less than one test for each 1,000 cubic yards of fill placed. Actual test intervals may vary as field conditions dictate. In fill slopes, approximately half of the tests shall be made at the fill slope, except that not more than one test needs to be made for each 50 horizontal feet of slope in each 2-foot vertical lift. Actual test intervals may vary as field conditions dictate. 4. Fill found not to be in conformance with the grading recommendations should be removed or otherwise handled as recommended by the soils engineer. Site Protection It shall be the grading contractor's obligation to take all measures deemed necessary during grading to maintain adequate safety measures and working conditions, and to provide erosion-control devices for the protection of excavated areas, slope areas, finished work on the site and adjoining properties, from storm damage and flood hazard originating on the project. It shall be the contractor's responsibility to maintain slopes in their as-graded form until all slopes are in satisfactory compliance with the job specifications, all berms and benches have been properly constructed, and all associated drainage devices have been installed and meet the requirements of the specifications. Appendix B Page 6 All observations, testing services, and approvals given by the soils engineer and/or geologist shall not relieve the contractor of his/her responsibilities of performing the work in accordance with these specifications. After grading is completed and the soils engineer has finished his/her observations and/or testing of the work, no further excavation or filling shall be done except under his/her observations. Adverse Weather Conditions 1. Precautions shall be taken by the contractor during the performance of site clearing, excavations, and grading to protect the worksite from flooding, ponding, or inundation by poor or improper surface drainage. Temporary provisions shall be made during the rainy season to adequately direct surface drainage away from and off the worksite. Where low areas cannot be avoided, pumps should be kept on hand to continually remove water during periods of rainfall. 2. During periods of rainfall, plastic sheeting shall be kept reasonably accessible to prevent unprotected slopes from becoming saturated. Where necessary during periods of rainfall, the contractor shall install checkdams, desilting basins, rip-rap, sandbags, or other devices or methods necessary to control erosion and provide safe conditions. 3. During periods of rainfall, the soils engineer should be kept informed by the contractor as to the nature of remedial or preventative work being performed (e.g. pumping, placement of sandbags or plastic sheeting, other labor, dozing, etc.). 4. Following periods of rainfall, the contractor shall contact the soils engineer and arrange a walk-over of the site in order to visually assess rain-related damage. The soils engineer may also recommend excavations and testing in order to aid in his/her assessments. At the request of the soils engineer, the contractor shall make excavations in order to evaluate the extent of rain-related damage. 5. Rain-related damage shall be considered to include, but may not be limited to, erosion, silting, saturation, swelling, structural distress, and other adverse conditions identified by the soils engineer. Soil adversely affected shall be classified as Unsuitable Materials, and shall be subject to overexcavation and replacement with compacted fill or other remedial grading, as recommended by the soils engineer. 6. Relatively level areas, where saturated soils and/or erosion gullies exist to depths of greater than 1.0 foot, shall be overexcavated to unaffected, competent material. Where less than 1.0 foot in depth, unsuitable materials may be processed in place to achieve near-optimum moisture conditions, then thoroughly recompacted in accordance with the applicable specifications. If the desired results are not achieved, the affected materials shall be over-excavated, then replaced in accordance with the applicable specifications. 7. In slope areas, where saturated soils and/or erosion gullies exist to depths of greater than 1.0 foot, they shall be overexcavated and replaced as compacted fill in accordance with the applicable specifications. Where affected materials exist to depths of 1.0 foot or less below proposed finished grade, remedial grading by moisture-conditioning in place, followed by thorough recompaction in accordance with the applicable grading guidelines herein presented may be attempted. If materials shall be overexcavated and replaced as compacted fill, it shall be done in accordance with the slope-repair recommendations herein. As field conditions dictate, other slope-repair procedures may be recommended by the soils engineer.