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1997-5212 G Street Address Category Serial # Name Description Plan ck. # Year SGC South /and Geotechnica/ Consultants R SOILS INVESTIGATION PROPOSED SINGLE - FAMILY RESIDENCE VACANT LOT, NORTH SIDE OF BUKAMADA LANE, LONE HILL ESTATES ENCINITAS, CALIFORNIA Project No. 148D41 May 29, 1997 wL Lei X99 - Prepared for: MR. MICHAEL PELTZ KTU + A 6165 Greenwich Drive, Suite 200 San Diego, California 92122 • 1238 GREENFIELD DRIVE, SU /TEA EL CAJON, CALIFORNIA 92021 • (619)442 -8022 • FAX (6 19144 2 -7859 SGC South /and Geotechnical Consultants r May 29, 1997 Project No. 148D41 To: Mr. Michael Peltz KTU + A 6165 Greenwich Drive, Suite 200 San Diego, California 92122 Subject: Soils Investigation, Proposed Single- Family Residence, Vacant Lot, North Side of Bukamada Lane, Lone Hill Estates, Encinitas, California Introduction ' Southland Geotechnical Consultants has performed a soils investigation for the proposed single - family residence located on a lot on the north side of Bukamada Lane ' in the Lone Hill Estates subdivision in Encinitas. This report presents a summary of our studies and provides our recommendations, from a geotechnical standpoint, relative to the proposed development. Purrose and Scope The purpose of our soils investigation was to evaluate the soils conditions at the property and provide recommendations relative to the proposed development. Our i scope of services included the following: - Review of geologic maps, literature, and aerial photographs pertaining to the ' site and vicinity. A preliminary project plan indicating the approximate location of the proposed residence and site improvements was also reviewed. A list of ' the documents reviewed is presented in Appendix A. -Field reconnaissance to observe the existing surficial soils conditions at the subject property and nearby vicinity. - Investigation of the subsurface soil conditions in the area of proposed ' development by excavating, logging and sampling six exploratory trenches at the site. Logs of the exploratory trenches are provided in Appendix B. ' - Appropriate laboratory testing of representative soil samples obtained during our subsurface investigation. Laboratory tests included expansion index and sulfate content tests. • 1238 GREENFIELD DRIVE, SU /TEA EL CAJON, CALIFORNIA 92021 • (619)442 -8022 • FAX (619)442 -7859 F Project No. 148D41 - Geotechnical analysis of the data obtained. - Preparation of this report summarizing the results of our soils investigation and presenting conclusions and recommendations, from a geotechnical standpoint, for the proposed development. Project Description The approximately two -acre subject property is a roughly rectangular lot located on the northern side of Bukamada Lane in the Lone Hill Estates subdivision in Encinitas (see Figure 1). The currently undeveloped lot slopes southerly at an overall gradient of approximately 6.5 to 1 (horizontal to vertical). A single - family residence exists to the north of the subject property. The adjacent lots to the west and east of the site are also currently undeveloped. The site is generally vegetated with grasses and weeds. Based on our conversations with you and our review of a project sketch, we understand that development of the property will consist of the construction of a two- story residence and associated improvements. It is assumed that the structure will be constructed with conventional materials including wood framing and concrete slab -on- ' grade floors. Building loads are assumed to be typical for this type of relatively light construction. Minor site grading (with cuts and fills up to a maximum of about 3 feet) is anticipated to attain design finished grades. Subsurface Investigation On May 7, 1997, six exploratory trenches were excavated at the project site. The exploratory trenches were excavated with a rubber -tire backhoe to a maximum depth of approximately 7 feet below the existing grade. The trenches were logged by an engineering geologist from our firm. Samples of the soils encountered during the subsurface investigation were obtained for laboratory testing. The approximate locations of the exploratory trenches are indicated on the Trench Location Map (Figure 2). Logs of the exploratory trenches are presented in Appendix B. Subsequent to logging and sampling, the trenches were backfilled. Laboratory Testing Appropriate laboratory tests were performed on representative samples of the onsite soils to evaluate their pertinent engineering properties. The tests included expansion index and sulfate content tests. The results of the tests are presented on Figure 3. r 2 SGC ` - Project No. 148D41 Soil and Geologic Units As encountered in our soils investigation, the project site is underlain by fill soils, topsoil and the Jurassic -aged Santiago Peak Volcanics. Following are brief descriptions of each unit: - Fill Soils - Relatively minor amounts of fill soils exist on the northeastern and southern portions of the site. In the northeastern portion of the site, the fill soils occur as a veneer of material overlying the natural ground surface. These soils generally consist of light brown silty sand with small green -gray claystone inclusions. In the southern portion of the site, the fill soils appear to be locally derived from weathered Santiago Peak Volcanics and appear to have been placed possibly during grading for the Bukamada Lane roadway. The fill soils at the site are considered potentially compressible and, in their present state, ` should not be relied upon for the support of structural loads. 1 - Topsoil - A topsoil layer of variable thickness has developed on and is gradational with the underlying Santiago Peak Volcanics. As encountered in our I exploratory trenches, the thickness of the topsoil layer ranged from 0 to 2.5 feet and generally consisted of red - brown, loose fine sandy silt, with roots and some weathered rock fragments. The topsoil was tested to have a low 1 expansion potential. However, in exploratory trench T -5, a topsoil horizon of 1 dark red - brown, silty clay with angular rock fragments was encountered. This clay horizon is similar to soils in the general area that have a high expansion potential when tested in accordance with UBC test designation 29 -2. The topsoil at the site is considered potentially compressible and, in its present state, should not be relied upon for the support of structural loads. - Santiago Peak Volcanics - The Santiago Peak Volcanics is the rock formation that underlies the entire site. Localized, surficial hard rock outcrops of the ' Santiago Peak Volcanics occur at the site. The Santiago Peak Volcanics generally consist of mildly metamorphosed volcanic and volcaniclastic rocks of variable composition and color. As encountered in our trenches, the Santiago Peak Volcanics are gray -green rocks and are variably weathered (from easily excavatable silty sand exhibiting relict rock features to hard, unweathered rock). The Santiago Peak Volcanics are considered suitable for the support of structural and fill loads. ' Review of Landslide Hazard Identification Mao Our review of the California Division of Mines and Geology Open -File Report 86 -15 (Appendix A, Reference 5) indicates that the property and nearby general sloped properties are mapped as Zone "2 ". Zone 2 pertains to areas which are "marginally 3 SG Project No. 148D41 susceptible" to "slope hazards" and includes "gentle to moderate slopes underlain by ' relatively competent material or colluvium that is considered unlikely to remobilize under natural conditions. Please note that the map was prepared for general land -use planning purposes and "it is not intended, nor suitable, for evaluation of individual sites" (Appendix A, Reference 5). Landslides and Slooe Stability Based on our review of aerial photographs (Appendix A) and our observations of onsite and nearby exposures, it is our opinion that the site does not appear to be underlain by a deep- seated landslide. In addition, the bedrock unit (Santiago Peak Volcanics) underlying the site is generally not known to be prone to slope instability in properly - engineered slopes. Faulting Our review of geologic maps and literature pertaining to the general site area (Appendix A) indicates that there are no known major or "active" faults on or in the immediate vicinity of the site. An "active" fault is defined by the CDMG (Appendix A, Reference 3) as one which has "had surface displacement within Holocene time (about the last 11,000 years) ". Evidence for active faulting on the site was not observed during our geotechnical investigation. The nearest known "active" fault is the Rose Canyon fault located offshore approximately 8.5 miles west of the site. Other known "active" faults in the region include the Elsinore fault located approximately 21 miles northeast of the site, and the Coronado Bank fault located offshore approximately 24 miles west of the site. The San Andreas fault is located approximately 65 miles northeasterly of the site. Groundwater and Surface Water Indications of a static, near - surface groundwater table were not encountered during our geotechnical investigation. Groundwater is not expected to be a constraint to construction of the proposed development. However, our experience indicates that near - surface groundwater conditions can develop in areas where no such groundwater conditions previously existed, especially in areas where a substantial increase in surface water infiltration results from landscape irrigation or unusually heavy precipitation. Site drainage generally occurs as sheet flow across the site. It is anticipated that site development will include appropriate surface drainage provisions. 4 Si7 C t Project No. 148D41 i Conclusions and Recommendations Based on the results of our soils investigation, it is our opinion that the, construction of the proposed residence and associated improvements is feasible from a geotechnical standpoint. The following sections discuss the geotechnical factors affecting the site and provide grading, foundation and other geotechnical recommendations which should be considered for design and construction of the proposed residential development. i Seismic Considerations The principal seismic considerations for most structures in southern California are surface rupturing of fault traces and damage caused by ground shaking or seismically - induced ground settlement or liquefaction. The seismic hazard most likely to impact the site is ground shaking resulting from an earthquake on one of the known active faults in the region. It is estimated that a magnitude 6.5 earthquake on the Rose Canyon fault, considered the design earthquake for the site, could produce a peak horizontal ground acceleration of 0.34g at the site. The effects of seismic shaking can be reduced by adhering to the most recent edition of the Uniform Building Code and current design parameters of the Structural Engineers Association of California. The possibility of damage due to ground rupture is considered low since no active faults are known to cross the site. Considering the dense nature of the underlying Santiago Peak Volcanics and lack of a static, near - surface groundwater table, it is our opinion that the potential for liquefaction or seismically- induced settlement at the site is low. Earthwork Site earthwork should be performed in accordance with the following recommendations and the general recommendations included in Appendix C (Recommended Earthwork Specifications). In the event of conflict, the recommendations presented herein supersede those of Appendix C. - Site Preparation - Prior to grading, the site should be cleared of surface and subsurface obstructions, and stripped of vegetation. Vegetation and debris should be properly disposed of off site. Holes resulting from removal of buried obstructions which extend below design finished grades should be filled with properly compacted fill soils. 5 SGC r. r Project No. 148D41 Areas to receive fill and /or structural improvements should be scarified to a depth of 6 inches, brought to near - optimum moisture conditions and uniformly compacted to a minimum of 90 percent relative compaction based on test method ASTM D1557. Removal and Recomoaction - The existing topsoil is considered compressible and unsuitable for the support of structural loads in its present condition. We recommend that the topsoil be removed in areas planned for structures, surface improvements or fill placement. As encountered in the exploratory pits, the ' topsoil apparently underlies some areas of the site to various depths. Actual depths should be evaluated by the geotechnical consultant during grading. The excavated soils may be stockpiled and are suitable for use as compacted fill provided they are free of organic material, deleterious debris and oversized materials (rocks with a maximum dimension greater than 6 inches). - Structural Fill Placement - The onsite soils are suitable for use as compacted fill provided they are free of organic material, deleterious debris and oversized materials (rocks with a maximum dimension greater than 6 inches). Areas to receive fill and /or structural improvements should be scarified to a minimum depth of 6 inches, brought to near - optimum moisture conditions and compacted to at least 90 percent relative compaction, based on laboratory standard ASTM D1557. The optimum lift thickness to produce a uniformly compacted fill will depend on the size and type of construction equipment used. In general, the fill should be placed in uniform lifts not exceeding 8 inches in loose thickness. Placement and compaction of fill should be observed and tested by the geotechnical consultant. In general, placement and compaction of fill should be performed in accordance with local grading ordinances, sound construction practices, and the Recommended Earthwork Specifications presented in Appendix C. Transition (Cut /Fill) Condition - If site grading results in a transition (cut -fill) condition underlying the proposed structure, we recommend that, to reduce the potential for damage to the structure due to differential settlement across the transition, a uniform fill thickness should be provided under the building. The cut portion of the building area should be overexcavated to a minimum depth of 3 feet and replaced with moisture - conditioned fill soils compacted to at least 90 percent relative compaction (ASTM D1557). The limits of overexcavation and recompaction should extend for a distance of at least 5 feet beyond the perimeter of the proposed building. - Graded Slopes - It is our opinion that cut and fill slopes (currently anticipated to be less than 5 feet in maximum height) will be generally stable if constructed at gradients of 2 to 1 (horizontal to vertical) or flatter. 6 S V C - Project No. 148D41 Excavations and Trench Backfill - It is anticipated that excavation of the onsite fill soils, topsoil and weathered Santiago Peak Volcanics can be accomplished by conventional grading equipment in good operating condition. However, hard Santiago Peak Volcanics rocks were observed at the surface of the site and heavy ripping, rock - splitting, blasting and /or jackhammering may be needed to facilitate excavation in hard rock areas. Trench backfill should be compacted in uniform lifts (not exceeding 8 inches in compacted thickness) by mechanical means to at least 90 percent relative compaction (ASTM D1557). - Imported Fill Soils - A cap of imported fill soils may be desired on the building pad area to facilitate foundation and utility trench excavation operations. Imported soils intended for such purposes should have a very low expansion index (expansion index less than 20) and should be tested by the geotechnical consultant for suitability prior to hauling on site. The imported soils should be brought to near - optimum moisture conditions and uniformly compacted to at least 90 percent relative compaction (ASTM D1557). Foundations Footings for the proposed single - family residential structure and associated improvements should be designed in accordance with structural considerations and the following recommendations. These recommendations assume that the near - surface soils will have a low expansion potential. If the expansion potential differs from that assumed herein, appropriate corresponding modifications to the foundation and slab recommendations may be necessary. Footings should be excavated entirely into dense formational materials (Santiago Peak Volcanics) or properly compacted fill soils. The proposed two -story structure may be supported by continuous or spread footings at a minimum depth of 18 inches below the lowest adjacent grade. Continuous footings should have a minimum width of 15 inches and be reinforced, at a minimum, with two No. 4 rebars (one near the top and one near the bottom). Spread footings should be designed in accordance with structural considerations and have a minimum width of 24 inches. At this depth, footings may be designed using an allowable bearing capacity of 2,000 pounds per square foot. This value may be increased by one -third for loads of short duration including wind or seismic loads. Slabs Concrete floor slabs underlain by soils with a very low to low expansion potential should have a minimum thickness of 4 inches and be reinforced at midheight with No. 7 S ^C • Project No. 148D41 3 rebars at 18 inches on center each way (or No. 4 rebars at 24 inches on center each way). Sidewalks should have a minimum thickness of 4 inches and be reinforced, as a minimum, at midheight with 6x6 -10/10 welded wire mesh. Care should be taken by the contractor to insure that the reinforcement is placed at slab midheight. Slabs and sidewalks should be designed with crack control joints at appropriate spacings for the anticipated loading. Nuisance cracking may be reduced by careful control of water /cement ratios. Floor slabs should be underlain by a minimum 2 -inch layer of clean sand (sand equivalent greater than 30). In moisture,sensitive areas or if floor coverings are planned, a 10 -mil moisture barrier is recommended beneath the t sand blanket. We recommend that a slip -sheet (or equivalent) be utilized if grouted tile or other crack - sensitive flooring is planned directly on the concrete slabs. The upper 12 inches of soils beneath the floor slabs should be moisture - conditioned to near - optimum moisture content prior to placement of the sand blanket, moisture barrier and concrete. Lateral Resistance and Retaining Wall Design Pressures Lateral loads can be resisted by assuming a passive pressure of 300 psf per foot of depth and a coefficient of friction of 0.35 between concrete and soil. The lateral resistance may be taken as the sum of the passive and frictional resistance, provided the passive resistance does not exceed two - thirds of the total resistance. Cantilever (yielding) retaining walls may be designed for an "active" equivalent fluid pressure of 35 pcf. Rigid (non - yielding) walls should be designed for an equivalent fluid pressure of 60 pcf. These values assume horizontal, nonexpansive, granular backfill and free - draining conditions. Walls subject to surcharge loading of vehicular traffic within a distance behind the wall equal to the wall height should be designed for an additional uniform pressure of 75 psf. If walls are surcharged by adjacent i structures, the wall design should take into account the surcharge load. We recommend that retaining walls be provided with appropriate drainage provisions. Appendix C contains a typical detail for drainage of retaining walls. The walls should be appropriately waterproofed. Appropriate waterproofing treatments and alternative, suitable wall drainage products are available commercially. Design of waterproofing and its protection during construction should be performed by the project architect. Wall backfill should be compacted by mechanical means to at least 90 percent relative compaction (ASTM D1557). Care should be taken when using compaction equipment in close proximity to retaining walls so that the walls are not damaged by excessive loading. 8 SG C Project No. 148D41 Site Drainage Drainage should be directed away from foundations, collected and tightlined to appropriate discharge points. Ponding of water should not be permitted. Landscape requiring a heavy irrigation schedule should not be planted adjacent to foundations or paved areas. Roof runoff should be collected and directed away from foundations via non - erosive devices. Slopes should be provided with appropriate surface drainage features and landscaped with drought - tolerant, slope - stabilising vegetation to reduce the potential for erosion. Berms should be maintained at the tops of fill slopes and brow ditches should be maintained at the tops of cut slopes. Inadvertent oversteepening of cut and fill slopes should be avoided during fine grading, landscaping and building construction. Sulfate Content The near - surface soils at the subject property have been tested to evaluate the degree of sulfate attack on ordinary (Type II) concrete. Based on the test results (Figure 3), it is our opinion that the degree of sulfate attack of the onsite soils is "negligible" based on 1994 Uniform Building Code Table 19 -A -3 criteria. However, the type of concrete specified and used should be determined by the structural engineer for the project. Plan Review /Construction Observation and Testing The recommendations provided in this report are based on preliminary project plans and interpolated subsurface conditions based on our exploratory trenches. Final project drawings for the proposed residential development should be reviewed by Southland Geotechnical Consultants prior to construction to check that the recommendations contained in this report are incorporated into project plans. Subsurface conditions should be checked in the field during construction. Geotechnical observation during site grading (removal /recompaction) and field density testing of compacted fill should be performed by Southland Geotechnical Consultants. Geotechnical observation of footing excavations should also be performed by the geotechnical consultant to check that construction is in accordance with the recommendations of this report. 9 SGC Project No. 148D41 ' If you have any questions regarding our report, please contact our office. Sincerely, r SOUTHLAND GEOTECHNICAL CONSULTANTS r ' Susan E. Tanges, CEG 1386 Ch les R. Corbin, RCE 36302 Managing Principal /Engineering Geologist Pr ject FtED GE O Q p ; OFESS /p,�� N E' TAN 0. v,�.ES R. C N0. 1386 �u'� <<:; ' CERTIFIED ENGINEERING J ,, GEOLOGIST � * Exp -'.L nO ' 6 ' 0 , F CAL ATF C I V 11- OF CA�� Attachments: Figure 1 - Site Location Map Figure 2 - Trench Location Map Figure 3 - Laboratory Test Results ' Appendix A - References Appendix 6 - Logs of Exploratory Trenches Appendix C - Recommended Earthwork Specifications Distribution: (3) Addressee 10 SV L YN 1 114 - VR Y 7 7 �7_ �_ t e v 3q 'W" -SITE J - `4 TA • �N SITE LOCATION MAP Project No. 148D41 Peitz Residence, Encinitas Scale (approximate): 1 inch = 2,000 feet Base Map: Geologic Map from CDMG Open-File Report 86-15LA, by Tan, 1987 FIGURE 1 SGC jib. . re r } r- r fir• • • • Project No. 148D41 LABORATORY TEST RESULTS Expansion Index The expansion potentials of two representative soil samples were evaluated. The tests were performed in general accordance with UBC Standard No. 29 -2. The results of the tests are presented below: SAMPLE LOCATION EXPANSION INDEX EXPANSION POTENTIAL Trench 1, Sample 1 @0 -1.5' 21 Low Trench 3, Sample 1 @0 -1' 27 Low Soluble Sulfate Content Soluble sulfate content tests were performed on representative samples of the onsite soils. The results are presented below. SAMPLE LOCATION SOLUBLE SULFATE CONTENT Trench 1, Sample 1 @0 -1.5' 28.7 mg /kg Trench 4, Sample 1 @0 -1.0' 74.9 mg /kg FIGURE 3 SV C r r. i i r APPENDIX A r a (J SGC i. Project No. 148D41 APPENDIX A REFERENCES 1. California Division of Mines and Geology, 1994, Fault activity map of California 1 ! and adjacent areas: CDMG Geologic Data Map No. 6. 2. Greensfelder, R.W., 1974, Maximum credible rock acceleration from earthquakes in California: California Division of Mines and Geology, Map ' Sheet 23. 3. Hart, E.W., 1994, Fault- rupture hazard zones in California: California Division of Mines and Geology, Special Publication 42, revised. 4. Southland Geotechnical Consultants, in -house geologic /geotechnical information. 5. Tan, S.S., 1987, Landslide hazards in the Rancho Santa Fe quadrangle, San Diego County, California: California Division of Mines and Geology, Open -file Report 86 -15LA. AERIAL PHOTOGRAPHS County of San Diego, 1928 -29, Photos 38E6 and 38E7 (stereoscopic). 1 County of San Diego, 1970, Series S.D.CO, Photos 6 -22 (115) and 6- 21(116), dated October 9 (color, stereoscopic). County of San Diego, 1978, Series SDCO 210, Flight Line 20C, Photo Nos. 17 (6385) and 18 (6386) (color, stereoscopic). MAPS Peitz Residence sketch provided by Michael Peitz. County of San Diego, 1982, Orthophoto topographic map, sheet 326 -1707, scale: 1" =200'. County of San Diego, Assessors Parcel Map Book Page 264 -03. County of San Diego, Parcel Map No. 16913, recorded July 29, 1992. 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U1 m x cu z m (D tr 0 U) ! I � � � •� rtS N m i . �. G U U 0 4-4 .o o Lz (0 ro 0 E U u I �+ En 4-4 ( — w > c0 W •~ w O U 1= U) U) >1 a) 4-I f0 N .°� W .° O U r-I U) rt N +� 1 , 4-) z L) 0 O U N < 1~ E 1 0 N U v O >1 0 - U U >1 4 -P U �4 r- Ln [ r �4 O 1~ U ro -H • 4J rn fr 3 >4 U rn x - Cil O II N I C N < r o U) (0 U 4J to ,--1 Q) 3 w Q) r- �4 ro M En c E .a O ' s~ • H N C: � z 1 U 4 e) 4-3 ro �J .-i fZ D U H 'o < (0 � N •H 0 H z co ro O N H N N S4 .0 ri �4 4- N "r 0t w M Z E-( 3> U 3 rd 4 w z 4 U ¢ -, CD < O O O (a F- N �4 p E1 < U) W U H z nn r Z a, v U) W Q a ro z z +-) U) U r. w U U _ CD M O O O C� U $. $ cr CL a. LU Southland Geotechnical Consultants i i r i i i i ' APPENDIX C t i � SGC RECOMMENDED EARTHWORK SPECIFICATIONS 1.0 General Intent These specifications are presented as general procedures and recommendations for grading and earthwork to be used in conjunction with the approved grading plans. These general earthwork specifications are considered a part of the recommendations contained in the geotechnical report and are superseded by recommendations in the geotechnical report in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new recommendations which could supersede these specifications or the recommendations of the geotechnical report. It shall be the responsibility of the contractor to read and understand these specifications, as well as the geotechnical report and approved grading plans. 2.0 Earthwork Observation and Testing Prior to grading, a qualified geotechnical consultant should be employed for the purpose of observing earthwork procedures and testing .fill placement for conformance with the recommendations of the geotechnical report and these specifications. It shall be the responsibility of the contractor to keep the geotechnical consultant apprised of work schedules and changes, at least 24 hours in advance, so that he may schedule his personnel accordingly. No ' grading operations shall be performed without the knowledge of the geotechnical consultant. The contractor shall not assume that the geotechnical consultant is aware of all site grading operations. It shall be the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable grading codes and agency ordinances, recommendations of the geotechnical report, and the approved grading plans. If, in the opinion of the geotechnical ' consultant, unsatisfactory conditions, such as unsuitable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resulting in a quality of work less than recommended in the geotechnical report and the specifications, the consultant will be empowered to reject the work and recommend that construction be stopped until the conditions are rectified. ' 3.0 Preparation of Areas to be Filled 3.1 Clearing and Grubbing Sufficient brush, vegetation, roots, and all other deleterious material should be removed or properly disposed of in a method acceptable to the owner, design engineer, governing agencies and the geotechnical consultant. SLYC r. The geotechnical consultant should evaluate the extent of these removals depending on specific site conditions. In general, no more than one percent (by volume) of the fill material should consist of these materials. In addition, nesting of these materials should not be allowed. 3.2 Processing The existing ground which has been evaluated by the geotechnical consultant to be satisfactory for support of fill, should be scarified to a minimum depth of 6 inches. Existing ground which is not satisfactory should be overexcavated as specified in the following section. Scarification should Continue until the soils are broken down and free of large clay lumps or clods and until the working surface is reasonably uniform, flat, and free of features which would inhibit uniform compaction. 3.3 Overexcavation Soft, dry, organic -rich, spongy, highly fractured, or otherwise unsuitable ground, extending to such a depth that surface processing cannot adequately improve the condition, should be overexcavated down to competent ground, as evaluated by the geotechnical consultant. For purposes of determining pay quantities of materials overexcavated, the services of a licensed land surveyor or civil engineer should be used. 3.4 Moisture Conditioning Overexcavated and processed soils should be watered, dried, or blended as necessary to attain a uniform near - optimum moisture content as determined by test method ASTM D1557. 3.5 RecoMDaction Overexcavated and processed soils which have been properly mixed, screened of deleterious material, and moisture- conditioned should be recompacted to a minimum relative compaction of 90 percent as determined by test method ASTM D1557. 3.6 Benching Where fills are placed on ground sloping steeper than 5:1 (horizontal to vertical), the ground should be stepped or benched. The lowest bench should be a minimum of 15 feet wide, excavated at least 2 feet into competent material as evaluated by the geotechnical consultant. Ground sloping flatter than 5:1 should be benched or otherwise overexcavated when recommended by the geotechnical consultant. 3.7 Evaluation of Fill Areas All areas to receive fill, including processed areas, areas of removal, and fill benches should be evaluated by the geotechnical consultant prior to fill placement. SGC IL 4.0 Fill Material 4.1 General Material to be placed as fill should be sufficiently free of organic matter and other deleterious substances, and should be evaluated by the geotechnical consultant prior to placement. Soils of poor gradation, expansion, or strength characteristics should be placed as recommended by the geotechnical consultant. 4.2 Oversize Material Oversize fill material, defined as material with a maximum dimension greater than 6 inches should not be buried or placed in fills unless the location, materials, and methods are specifically recommended by the geotechnical consultant. 4.3 lmoort If grading operations include importing of fill material, the import material should meet the requirements of Section 4.1. Sufficient time should be given to allow the geotechnical consultant to test and evaluate proposed import as necessary, prior to importing to the site. 5.0 Fill Placement and Compaction 5.1 Fill Lifts: Fill material should be placed in areas properly prepared and evaluated as acceptable to receive fill. Fill should be placed in near - horizontal layers approximately 6 inches in compacted thickness. Each layer should be spread evenly and thoroughly mixed to attain uniformity of material and moisture content throughout. 5.2 Moisture Conditioning Fill soils should be watered, dried or blended as necessary to attain a uniform near - optimum moisture content as determined by test method ASTM D1557. 5.3 Compaction of Fill After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to not less than 90 percent of maximum dry density as determined by test method ASTM D1557. Compaction equipment should be adequately sized and be either specifically designed for soil compaction or of proven reliability to efficiently achieve the specified degree and uniformity of compaction. 5.4 Fill Slopes Compaction of slopes should be accomplished, in addition to normal compaction procedures, by backrolling slopes with sheepsfoot rollers at increments of 3 to 4 feet in fill elevation gain, or by other methods producing satisfactory results. At the completion of grading, the relative compaction of the fill, including the embankment face should be at least 90 percent as determined by test method ASTM D1557. SGG T 5.5 Compaction Testing Field tests of the moisture content and degree of compaction of the fill soils should be performed by the geotechnical consultant. The location and frequency of tests should be at the consultant's discretion based on observations of the field conditions. In general, the tests should be taken at approximate intervals of 2 feet in elevation gain and /or each 1,000 cubic yards of fill placed. In addition, on slope faces, as a guideline, one test should be taken for each 5,000 square feet of slope face and /or each 10 -foot interval of vertical slope height. 6.0 Subdrain Construction Subdrain systems, if recommended, should be constructed in areas evaluated for suitability by the geotechnical consultant. The subdrain system should be constructed to the approximate alignment in accordance with the details shown on the approved plans or provided herein. The subdrain location or materials should not be modified unless recommended by the geotechnical consultant. The consultant may recommend modifications to the subdrain system depending on conditions encountered. Completed subdrains should be surveyed for line and grade by a licensed land surveyor or civil engineer. r 7.0 Excavations r Excavations and cut slopes should be evaluated by the geotechnical consultant during grading. If directed by the geotechnical consultant, further excavation, overexcavation, and /or remedial grading of cut slopes (i.e., stability fills or slope buttresses) may be recommended. 8.0 Quantity Determination The services of a licensed land surveyor or civil engineer should be retained to determine quantities of materials excavated during grading and /or the limits of overexcavation. sic TRANSITION LOT DETAILS CUT —FILL LOT EXISTING GROUND SURFACE - MIN. 3 ----------------------------- 8 MIN.* ------------ F I j --------- (OVEREXCAVATE AND RECOMPACT COMPETENT BEDROCK OR MATERIAL EVALUATE BY THE GEOTECHNICAL CONSULTANT CUT LOT EXISTING GROUND SURFACE REMOVE 5 •• UN SUITAB L E F N. MI N. ------------------------ I ------------ .38' MIN�* --------- ------- --------- -- -- -------- COMPACTED= =- ------ --------- G= 7 It = = F I LL REXCAVATE = _ =__ - AND RECOMPACT ------- COMPETENT BEDROCK R MATERIAL EVALUATED BY THE GEOTECHNICAL CONSULTANT *NOTE: Deeper or laterally more extensive overexcavation and recomoaction may be recommended by the geatechniCal consultant based on actual field conditions encountered and locations of proposed improvements SGC RETAINING WALL DRAINAGE DETAIL SOIL BACKFILL. COMPACTED TO 90 PERCENT RELATIVE COMPACTION ------------ ----------- ---------- RETAINING WALL -----.,..[ ------- ----- ------ 0 - -- 1 - 1 10 " ' S' M I N. " FILTER FABRIC ENVELOPE WALL WATERPROOFING OVERLAP 6 --- (MIRAFI 140N OR APPROVED PER ARCHITECT'S 0 0 a -- SPECIFICATIONS - EQUIVALENT) 1 MIN. 314'-1-112' CLEAN GRAVEL FINISH GRADE 0 *0 4' (MIN.) DIAMETER PERFORATED 0 0 PVC PIPE (SCHEDULE 40 OR EQUIVALENT) WITH PERFORATIONS ORIENTED DOWN AS DEPICTED ------------------------------ ----------------------------- - MINIMUM I PERCENT GRADIENT ----------------------------- :-- ---- TO SUITABLE OUTLET .COMPACTED - Z:: ---------------------- ------------ WALL FOOTING T 3 MIN. NOT TO SCALE COMPETENT BEDROCK OR MATERIAL AS EVALUATED BY THE GEOTECHNICAL SPECIFICATIONS FOR CALTRANS CONSULTANT CLASS 2 PERMEABLE MATERIAL U.S. Standard * BASED ON ASTM D1557 Sieve Size % Passing lit 100 ** IF CALTRANS CLASS 2 PERMEABLE MATERIAL 3/4 90-100 (SEE GRADATION TO LEFT) IS USED IN PLACE OF 3/8" 40-100 3/4'-1-1/2' GRAVEL, FILTER FABRIC MAY BE DELETED. CALTRANS CLASS 2 PERMEABLE No. 4 25-40 MATERIAL SHOULD BE COMPACTED TO 90 No. 8 18-33 PERCENT RELATIVE COMPACTION No. 30 5-15 No. 50 0-7 No. 200 0-3 NOTE:COMPOSITE DRAINAGE PRODUCTS SUCH AS MlIRADRAIN Sand EquivaTent>75 !OR J-DRAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR CLASS Z INSTALLATION SHOULD BE PERFORMED IN ACCORDANCE WITH MANUFACTURER'S SPECIFICATIONS. SGC KEY AND BENCHING DETAILS FILL SLOPE PROJECT 1 TO I LINE FROM TOE OF SLOPE OQ j To COMPETENT MATERIAL EXISTING -------- - GROUND SURFACE ---- ---- -- -- --------- - REMOVE UNSUITABLE MATERIAL BENCH 2% MIN. 2' MIN. 15 MIN KEY I LOWEST DEPTH BENCH (KEY) OMPACTED=�.7-_ FILL-OVER-CUT SLOPE EXISTING GROUND SURFACE /p BENCH -2 REMOVE UNSUITABLE 2 LOS'WMEISNT� MATERIAL MIN. BENCH KEY (KEY) KEY) lalll CUT SLOPE (TO BE EXCAVATED PRIOR TO FILL PLACEMENT) EXISTING GROUND SURFACE IV CUT SLOPE CUT-OVER-FILL SLOPE (TO BE EXCAVATED PRIOR TO FILL PLACEMENT) REMOVE UNSUITABLE PROJECT I TO I MATERIAL LINE FROM TOE OF SLOPE TO COMPETENT MATERIAL BENCH MIN. V , MIN 2 MIN.'� 5' MIN KEY DEPTH BENCH (KEY) NOTE: Sack drain may be recommended by the geotechnical consultant based an actual field conditions encountered. Bench dimension recommendations may also be altered based on field conditions encountered. SGC -- -- -- -- ---- -- -- -- -- -- ---- ---- ROCK DISPOSAL DETAIL SLOPE FACE OVERSIZE WINDROW GRANULAR SOIL (S.Ea 3a) TO BE DENSIFiED IN PLACE BY FLOODING DETAIL -~ TYPI CAL PROFILE ALONG WINDROW 1�Rockwn�hnnaximnum dimensions greater than 6 inches should not be used within 10 feet vertically of finish grade (or 2 feet below depth of lowest utility whichever is greater), and 15 feet horizontally of slope faces. 2) Rocks with maximum dimensions greater than 4feet should not be utilized in fills. 3) Rock placement, flooding of granular soil, and fill placement should be observed by the geotmchnioal consultant. U� 4] Maximum size and spacing of windrows should bein accordance with the above details Width mfwindrow should not exceed 4 feet. Windrows should be staggered vertically (ms depicted). 5) Rock mbquid be placed in excavated trenches. Granular soil (S'E' greater than or equal to 30) should be flooded in the windrow to com pl e tely fill voids around arid beneath �� rocks. SGC FROM PHONE NO. : 619 442 7859 Nov. 24 1997 03:30PM P2 SGC South /and Geotechnical Consultants November 24, 1997 Project No. 148D41.1 To: Mr. Michael Peitz KTU + A 6135 Greenwich Drive, Suite 200 San Diego, California 92122 Subject: As- Graded Geotechnical Report, Proposed Single - Family Residence, Vacant Lot, North Side of Lone Hill Estates Court, Encinitas, California (Portion of Parcel 2 of Parcel Map No. 16913) Reference: Soils Investigation, Proposed Single - Family Residence, Vacant Lot, North Side of Lone Hill Estates Court, Encinitas, California (Portion of Parcel 2 of Parcel Map No. 16913), Encinitas, California, by Southland Geotechnical Consultants, dated May 29, 1997 Introduction Southland Geotechnical Consultants has performed field observation and testing services during grading at the subject property located on the, North Side of Lone Hill Estates, Encinitas, California (Portion of Parcel 2 of Parcel Map No. 16913). This as- graded geotechnical report summarizes our observations and test results and presents recommendations, from a geotechnical standpoint, for design and construction of the proposed single - family residence on the property. Grading Operations Grading of the subject property was accomplished during the period of October 14 through November 14, 1997. Grading observation and testing of compacted fill were performed by a field technician from our firm who was on site as needed during site grading. Site grading generally conforms with the project grading plan entitled "Grading Plan for: Peitz Residence, Portion of Parcel 2 P.M. No. 16913," prepared by Nasland Engineering, Inc., dated September 15, 1997. Prior to grading, areas of the site to receive fill were stripped of surface vegetation, debris, and loose soils. Prior to filling, the natural ground was scarified, brought to near - optimum moisture conditions, and compacted to at least 90 percent of the laboratory maximum dry density as determined by ASTM D1557. Fill soils were brought to near - optimum moisture conditions, placed in approximately 8- to 10 -inch lifts, and compacted by mechanical means to at least 90 percent of the laboratory maximum dry density as determined by ASTM 131557. • 1238 GREENFIELD DRIVE, SUITE A Et CAJON, CALIFORNIA 92021 • (619)442 -8022 • FAX !6191442 -7859 FROM PHONE NO. 619 442 7859 Nov. 24 1997 03:30PM P3 Project No. 14SD41.1 Cut -Fill Transition Condition As shown on the grading plan, it was anticipated that site grading would result in a transition (cut -fill) condition underlying the building pad. To reduce the potential for structural damage due to differential settlement across the transition, the cut portion of the pad was overexcavated to a minimum depth of 3 feet below finished pad grade and replaced as moisture - conditioned, properly compacted fill soils. Field and Laboratory Tests Field density tests were performed in general accordance with ASTM 131556 (Sand - Cone Method). The results of the field density tests for the subject property are presented in Appendix A (Summary of Field Density Tests). The approximate locations of the field density tests and the approximate locations of the area of compacted fill placed during grading of the site are presented on Figure 1 (Field Density Test Location Map). The laboratory maximum dry density and optimum moisture content of the fill soils were determined in general accordance with ASTM D1557. The results of the laboratory tests are presented in Appendix A (Maximum Density Test Results). CONCLUSIONS AND RECOMMENDATIONS Our observations and field and laboratory test results indicate that the structural fiii soils placed during grading of the subject property have been compacted to at least 90 percent relative compaction as evaluated using test methods ASTM D1556 and ASTM D1557. The fill soils placed on site generally consisted of red- brown, silty to clayey fine -to coarse - grained sand. These soils are similar to soils in the general area found to have low expansion potential when tested in accordance with UBC Test Standard 29 -2. Recommendations for foundations, floor slabs and other construction considerations for the proposed structures are presented in the following sections (and are, in general, reiterated from our referenced report). Foundations Foundations should be designed in accordance with structural considerations and the following recommendations. These recommendations assume that the soils encountered during foundation excavation will have a low expansion potential. The proposed two -story structure may be supported by continuous or spread footings at 2 UGC FROM PHONE NO. : 619 442 7859 Nov. 24 1997 03:31PM P4 Project No. 1481341.1 a minimum depth of 18 inches below the lowest adjacent grade. Continuous footings should have a minimum width of 15 inches and be reinforced, at a minimum, with two No. 4 rebars (one near the top and one near the bottom). Spread footings should be designed in accordance with structural considerations and have a minimum width of 24 inches. At this depth, footings may be designed using an allowable bearing capacity of 2,000 pounds per square foot. This value may be increased by one -third for loads of short duration including wind or seismic loads. Slabs Concrete floor slabs underlain by soils with low expansion potential should have a minimum thickness of 4 inches and be reinforced at midheight with No. 3 rebars at 18 inches on center each way (or No. 4 rebars at 24 inches on center each way). Sidewalks should have a minimum thickness of 4 inches and be reinforced, as a minimum, at midheight with 6x6 -10/10 welded wire mesh. Care should be taken by the contractor to insure that the reinforcement is placed at slab midheight. Slabs and sidewalks should be designed with crack control joints at appropriate spacings for the anticipated loading. Nuisance cracking may be reduced by careful control of water /cement ratios. Floor slabs should be underlain by a minimum 2 -inch layer of clean sand (sand equivalent greater than 30). In moisture- sensitive areas or if floor coverings are planned, a 10 -mil moisture barrier is recommended beneath the sand blanket. We recommend that a slip -sheet (or equivalent) be utilized if grouted the or other crack- sensitive flooring is planned directly on the concrete slabs. The upper 12 inches of soils beneath the floor slabs should be moisture - conditioned to near - optimum moisture content prior to placement of the sand blanket, moisture barrier and concrete. Retaining Walls_ We recommend that retaining walls be provided with appropriate drainage provisions (Appendix C of the referenced report contains a typical detail for drainage of retaining walls). Appropriate waterproofing treatments and alternative wall drainage products are available commercially. Wall backfill should be compacted by mechanical means to at least 90 percent relative compaction (ASTM D1557). Care should taken when using compaction equipment in close proximity to retaining walls so that the walls are not damaged by excessive loading. 3 SGC FROM PHONE NO. : 619 442 7859 Nov. 24 1997 03:38PM P1 Project No. 148D41.1 to e L and Site Dr ina e Slopes should be provided with appropriate surface drainage features and landscaped with drought - tolerant, slope - stabilizing vegetation as soon as possible after grading to reduce the potential for erosion. Berms should be provided at the tops of fill slopes and brow ditches should be constructed at the tops of cut slopes. We recommend that measures be taken to properly finish grade the lot such that drainage is directed away from foundations (4 percent minimum_ for a distance of at least 5 feet). Drainage should be directed away from tops of slopes and foundations toward the street or collected and tightlined to appropriate discharge points. Lot drainage should be directed such that surface runoff on slope faces is minimized. Inadvertent oversteepening of cut and fill slopes should be avoided during fine grading and building construction. Landscape requiring a heavy irrigation schedule should not be planted adjacent to foundations. The use of eave gutters with downspouts that discharge to the street or other appropriate discharge point should be considered to control roof runoff. Water, either natural or from irrigation, should not be permitted to pond or saturate the surface soils or flow over the tops of any slopes. Construction Observation and Testing The recommendations provided in this report are based on our understanding of the proposed construction and our evaluation of the onsite soil conditions as tested during site grading. Construction inspection of foundations and field density testing of any additional compacted fill should also be performed by the geotechnical consultant to check that construction is in accordance with the recommendations of this report. 4 SGC FROM : PHONE NO. : 619 442 7859 Nov. 24 1997 03:39PM P2 Project No. 14SD41.1 If you have any questions regarding this report, please do not hesitate to contact our office. Sincerely, SOUTHLAND GEOTECHNICAL CONSULTANTS 4 ene Custenb f G 1319 Charle S� 6302 Principal E a �O gist Proje �� O �L w N O. 131f% a N0.36302 * CERTIFIED Exp tv - CV CNGINEERING GEOLOGIST 9cAt�F°�� Clv l9TF OF CAS -� Attachments: Figure 1 - Field Density Test Location Map Appendix A - Field and Laboratory Test Results Distribution: (3) Addressee 5 + ± ► C FROM PHONE NO. : 619 442 7859 Nov. 24 1997 03:39PM P3 Project No. 1481341.1 APPENDIX A - FIELD AND LABORATORY TEST RESULTS SUMMARY OF FIELD DENSITY TESTS Field density tests were performed in general accordance with ASTM D1556 (Sand - Cone Method). The results of the test are presented below: TEST ELEVATION SOIL FIELD DRY MAXIMUM FIELD OPTIMUM RELATIVE NO. I DATE (ftd) TYPE DENSITY DRY DENSITY MOISTURE MOISTURE COMPACTION x 1 10/15/97 371 A 97.1 117.5 17.4 13.0 83 2 1 10/16/97 371 A 115.4 117.5 13.0 13.0 98° 3 10/16/97 373 A 107.2 117.5 14.8 13.0 97 4 10/16/97 375 A 109.6 117.5 16.3 13.0 93 4 11/14/97 377 A 113.7 117.5 14.2 13.0 96 5 11/14/97 377 A 112.5 117.5 15.3 13.0 95 retested on 2 - a • retest of 1 MAXIMUM DENSITY TEST RESULTS A maximum dry density and optimum moisture content test was performed on a representative sample of the fill soils. The test was performed in general accordance with ASTM 131557. The results of the test are presented below: SAMPLE MAXIMUM OPTIMUM NUMBER SAMPLE DESCRIPTION DRY DENSITY MOISTURE (pcf) (%) A Red - brown, silty to slightly clayey, 117.5 13.0 fine- to coarse - grained sand. (SM -SC) ��! FROM PHONE NO. 619 442 7859 Nov. 24 1997 03 :40PM P4 � � N O! 1p :w u� FIELD DENSITY TEST LOCATION MAP LE GEND BASE MAP: Adapted from plan entitled Grading Plan for: Peitz Residence, Sheet 1, • Approximate location prepared by Nasland Engineering, dated of field density test September 15, 1997 Approx. scale: 1 inch = 40 feet Project No. 148D41.1 Figure 1