Loading...
HomeMy WebLinkAbout; La Costa Vale Unit 3 Lot 473; Soils Report Preliminary; 1989-03-20-- - - x ‘- - - - - - .- - - -. PRELIMINARY GEOTECHNICAL INVESTIGATION, PROWSED SINGLE-FAMILY RESIDENCE, LOT 473, LA COSTA VALE, UNIT NO. 3 ; (TRACT MAP NO. 7950), BETWEEN CADENCIA STREET AND VENADO DRIVE, CARLSBAD, CALIFORNIA March 20, 1989 Project No. 8881297-01 ENGINEERING DEPT. LIBRARY City of Cartsbad 2075 Las Palmas Drive Carlsbad CA 92009-4859 ‘. .- ,,I ,.: f-T-1, ~-7: ,m I-3 r,,._ ,, I . ..1 ../.,_ ,,_,.. /.3 L‘-. x_,“.d_ ;. ~’ . &%, _ :; L:, .z L ;‘,‘. Prepared for: MR. AND MRS. RONALD BARELS 1832 Parliement Road Encinitas, California 92024 5421 AVENIDA ENCINA5, SUITE C, CARL&IQ CALIFORNIA 92008 (619) 931-9953 FAX (619) 931-9326 - - .- ,- March 20, 1989 Project No. 8881297-01 TO: Mr. and Mrs. Ronald Barels 1832 Parliement Road, Encinitas, California 92024 SUBJECT: Preliminary Geotechnical Investigation, Proposed Single-Family Residence, Lot 473, La Costa Vale, Unit No. 3 (Tract Map No. 7950). Between Cadencia Street and Venado Drive, Carlsbad, California In accordance with your signed authorization, we have conducted a preliminary geotechnical investigation of the subject site. The accompanying report presents a summary of our investigation and provides conclusions and recommendations relative to site development. If you have any questions regarding our report, please do not hesitate to contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. )$ ,d;r p4CLd. & Michael R. Stewart, EG 1349 (Exp. 6/30/90) Chief Engineering Geologist Stan Helenschmidt, RCE 36570 (Exp. 6/30/92) Chief Engineer(Manager RLW/MRS/SRH/bje Distribution: (3) Addressee (3) R.D.A. Design & Drafting Services Attention: Mr. Ronald Alvarez - 5421 AVENIDA ENCINAS, SUITE C, CARLSBAQ CALIKJRNIA 92008 (619) 931-9953 FAX (619) 931-9326 a ,- ~- - - - - - 8881297-01 Section TABLE OF CONTENTS 1.0 2.0 INTRODUCTION 1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT 2.1 Site Description and Location 2.2 Proposed Development 3.0 4.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING 4 SUMMARY OF GEOTECHNICAL CONDITIONS 4.1 Regional Geologic 4.2 Site Geology 4.3 Ground Water and Surface Water 4.4 Faulting and Seismicity 5.0 CONCLUSIONS 7 6.0 RECOMMENDATIONS 8 B ii ; 10 6.1 Earthwork 6.2 6.1.1 Site Preparation 6.1.2 Excavations and Backfill 6.1.3 Fill Placement and Compaction 6.1.4 Removal and Recompaction Slope Stability 6.2.1 Deep-Seated Stability 6.2.2 Surficial Slope Stability Surface Drainage and Erosion Foundation and Slab Design Considerations 6.4.1 Foundations 6.4.2 Concrete Flatwork Lateral Earth Pressures and Resistance Type of Cement for Construction Pavement Sections Construction Observation :: 10 11 :: :: :: lMHlD# AND ASSMAllS INC - - ..~ - , -- 3~ - s - 8881297-01 TABLE OF CONTENTS (Continued) LIST OF ILLUSTRATIONS Fiaures Figure 1 - Site Location Map Figure 2 - Regional Seismicity Index Map Figure 3 - Geotechnical Map Table 1 - Seismic Parameters for Active Faults Table 2 - Minimum Foundation and Slab Recommendations for Expansive Soils Appendix A - Appendix B - Appendix C - Appendix D - Appendix E - APPENDICES References Trench Logs Sampling and Laboratory Test Results Slope Maintenance Guidelines for Homeowners General Earthwork and Grading Specifications ” Rear of Texf Rear of Text Rear of Text Rear of Text 8881297-01 - 1 .O JJJTROOUCTIOR - M; report presents the results.of our geotechnical.investigation at the subject . The ouroose df the investlaatlon was to identlfv and evaluate the oeotech- nical conditions present on the site and to provide &nclusions and geotechnical recommendations regarding the proposed development. Our scope of services of the investigation included: - 0 l 0 .- l -~ l - : e l Review of available ertinent, published and unpublished geologic literature and maps (Appendix A P . Aerial photographic analysis to assess the general geology and possible fault- ing (Appendix A). Field reconnaissance of the existing on-site geotechnical conditions. Subsurface exploration consisting of the excavation, five exploratory backhoe trenches. log ing, il and sampling of The logs of the trenc es are presented in Appendix B. Ap ropriate laboratory testing of representative samples obtained from our su It surface exploration program (Appendix C). Geotechnical analysis of field data and laboratory test results. Preparation of this report presenting our findings, conclusions, and recomnen- dations with respect to the proposed development. -I- SITE LOCATION MA BARELS / LA COSTA CARLSBAD, CALIFORNIA - 2 I ..- .~ ,- ..~ ,- - ., - - .~. 8881297-01 2.1 2.2 2.0 SITE DESCRIPTION AND PROPOSED DEVELOPMENT Site Descriotion and Locatiop The subject site is roughly rectangular and is located between Venado Drive and Cadencia Street in the La Costa area of Carlsbad, California (Figure 1, pa e re atively 7 2). The -property encompasses approximately one acre of vacant and undeveloped land. Topographically, the site consists of a moderately steep to steep, westerly-facing hillside. (Appendix A, The project plans Reference 16) indicate that site elevations range from ap- proximately 235 feet near the northwest corner of the site to approximately 325 feet along Venado Drive. Site inclinations range from essentially level in the previously graded area of the site in the northwestern portion of the property to the approximately 2:l (horizontal to vertical) fill slope lo- cated along the west side of Venado Drive. Site vegetation primarily consists of weeds, grasses, and shrubs which are locally dense. Existing improvements in the vicinity of the site include Venado Drive and Cadencia Street, a dirt road which traverses across the southeastern portion of the site, and a San Diego Gas & Electric (SDG&E) power line easement located along the northern property boundary. Prooosed Develooment Based on our review of the project site plans prepared by R.D.A. Design & Drafting Services (Ap endix A, Reference 16), we understand the proposed site development WI 1 3 consist of a two-story, single-family residential structure with associated improvements. Further, we understand the struc- ture will utilize a combination of slab-on-grade and raised foundation construction. In addition, the residence will incorporate a 6- to 12-foot high retaining wall in the northeastern portion of the building pad. Structural information was not available at the time of this report. However, building loads are assumed to be typical for this type of struc- ture. The project P lans site will (Appendix A, Reference 16) indicate that grading of the resu t in cut and fill slopes to 26 and 14.5 feet, respectively. In accordance with City of Carlsbad grading ordinances, graded slopes are to be constructed at inclinations of 2:l (horizontal to vertical) or flatter. -3- 8881297-01 - - .- .- - __ 3.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING Our subsurface exploration program consisted of five exploratory backhoe trenches to a maximum depth of 10.5 feet. The approximate locations of the trenches are shown on the Geotechnical Map (Figure 3, rear of text). The purpose of this program was to evaluate the physical characteristics of the onsite soils per- tinent to the proposed development. In addition, these trenches provided data regarding the excavatability characteristics of the metavolcanic bedrock underly- ing the site. The trenches were geologically logged. Representative bulk soil samples were obtained from the trenches for laboratory testing. The trench logs are presented in Appendix B. were backfilled. Subsequent to logging and sampling, all trenches Appropriate laboratory testing was performed on representative samples to evaluate the expansion potential and sulfate content of the subsurface soils. A discussion of the laboratory tests performed and a summary of the laboratory test results are presented in Appendix C. -4- - 8881297-01 4.0 SUMMARY OF GEOTECHNICAL CONDITIONS 4.1 Reaional Geoloaic l The subject site is located in the coastal section of the Peninsular Range Province within the southern California batholith. The Peninsular Range Province is a physiographic province with a long and active history in southern California and is characterized by northwest-trending mountain ranges separated by subparallel fault zones. The Peninsular Range Province is traversed by several major, active faults (Figure 2). The Elsinore and San Jacinto faults (associated with the San Andreas fault system) are the major tectonic features. Both are strike-slip faults with predominantly right-lateral movement. The major tectonic ac- tivity appears to be a result of right-lateral movement on faults within the San Andreas fault system. 4.2 Site Geoloay - Based on o;id subsurface exploration (Appendix B analysis, review of pertinent geotechnica I* aerial photographic literature and maps (A pendix A), the site is underlain by the Jurrassic-aged Santiago Peak -7 Vo canics (Map Symbol - Jsp). This dense bedrock unit generally possesses a fine- to coarse-grained texture with scattered inclusions within the metavolcanic rock. The relatively dense metavolcanic rock was noted as highly weathered near the surface, becoming less weathered with increasing depth. Numerous high- and low-angle joints and randomly orientated frac- tures were noted in the metavolcanic rock during our subsurface exploration. These joints were measured as striking from N62'E to N47'W and dipping 32 to 87 degrees to the north and south. In general, the intervals between joints were typically on the order of 12 inches, ranging from 1 inch to 3 feet. A thin (approximately l- to 3-foot thick), topsoil horizon (unmapped unit) was noted mantling the metavolcanic rock. The topsoil grades into the weathered metavolcanic rock and generally consists of a medium brown to dark red-brown, damp to moist, soft to firm, sandy silt to sandy clay. Based on laboratory testing and visual classification, these soils generally have a low to moderate expansion potential and may be compressible upon loading in their present state. - _, Beneath the topsoil horizon, weathered. As encountered, the metavolcanics are generally extensively the upper metavolcanic bedrock generally weathers to a light brown to yellow-brown, damp to moist, firm to stiff, silty clay to clayey sand with resistant bedrock fragments to approximately 2 feet in size. Based on laboratory testing, these soils possess a very high potential for expansion. -5- - 8881297-01 As identified on the Geotechnical Ma 14-foot high, 2:l (horizontal to vertica (Fi ure 3, rear of text), a lo- to ! 9 fi 1 slope is located along the western edge of Venado Drive. These fi 1 soils appear to have been placed during the roadway construction although documentation has not been reviewed for its placement. These fill soils are, in turn, overlain by loose fill soils that appear to have been dumped over the top of slope. In addition! a small area of undocumented fill was identified in the northwestern portjon of the site. The soil utilized as fill appears to have been derived from the materials discussed above. - 4.3 Ground Water and Surface Water - - No indication of surface water or ground water was observed during our investigation. on the site. In addition, a shallow ground water table is not anticipated However, it should be noted that ground water may be stored within fractures and joints of the metavolcanic bedrock for short periods following storm activity or artificial recharge due to irrigation. This stored ground water may be evidenced as seeps where water-bearing fractures and joints are exposed at the surface or daylighted in excavations. Seasonal fluctuations In rainfal!, variations in ground surface topography, T;tel;ubsurface conditions may significantly affect surface and ground water 4.4 Faultina and Seismicitv - Our review of available geologic literature indicated that there are no known major or active faults on the site. The seismic hazard most likely to impact the site is ground shaking due to a large earthquake on a major active regional fault. The nearest active regional fault is the Elsinore Fault, located ap roximately 23 miles east of the site. The maximum an- ticipated bedroc f: acceleration on the site is estimated to be approximately 0.239 based on a maximum probable earthquake of 7.5 magnitude on the Elsinore fault. For design purposes, two-thirds of the maximum anticipated bedrock acceleration may be assumed for the repeatable ground acceleration. The effects of seismic shaking can be minimized if construction is in ac- cordance with the current edition of the Uniform Building Code or state-of- the-art seismic design criteria of the Structural Engineers Association of California. - L - - -6- lEiDUlW AND AEEWIATES MC - - - I- .~~ i- - - .- - - 8881297-01 5.0 QBCLUSIW Based on the results of our preliminary geotechnical investigation of the site, it is our opinion that the proposed development is feasible from a geotechnical standpoint provided the recommendations of this report are incorporated into the project plans and specifications. The following is a summary of the geotechnical factors which may affect develop- ment of the site. The site is entirely underlain by dense metavolcanic rock which will likely impact the ease and cost of excavation. In addition, cut slopes excavated in the metavolcanic bedrock may result in somewhat irregular slope faces. Our investigation indicates that the site is generally rippable to the depths of cut proposed by appropriate heavy construction equipment. However, due to possible irregular weathering of the metavolcanic bedrock, local anomalies of nonrippable rock may be encountered within the generally rippable zone. In addition, material. site grading is anticipated to generate quantities of oversize Active faults are not know to exist on or in the vicinity of the site. Based on our subsurface exploration and laboratory testin the topsoil encountered on the site is considered potentially compressib e. These soils 4' are not considered suitable for structural loads or support of fill in their present condition. Remedial grading measures such as removal and recompaction will be necessary to mitigate this condition (Section 6.1.4). Based on laboratory testing and visual classification, the onsite topsoil and weathered metavolcanic bedrock is anticipated to possess a moderate to very high expansion potential. Excavations in the metavolcanic rock may generate oversize materials which may be unsuitable for use in structural fills. The maximum anticipated bedrock acceleration on the site is estimated to be approximately 0.239 based on a maximum probable earthquake of Richter Magnitude 7.6 on the active Elsinore fault. No ground water was encountered during our investigation, nor is ground water anticipated to be encountered during site excavation and construction. Ground water is not anticipated to adversely affect the proposed development provided the recommendations of this report are followed. Loose fill soils are present over the existing 2:l (horizontal to vertical) fill slope beneath Venado Drive. grading of the site. These soils will require removal during If complete removal of loose soils is not possible without oversteepening the existing slo e, necessary. This area should be eva uated by the geotechnical consultatant ! special metigative measures may be during grading. -7- - - - - 8881297-01 6.0 RECOMMENDATIONS 6.1 hthwork We anticipate that earthwork on the site will consist of site preparation, excavation, and backfill. We recoanaend earthwork on the site be performed in accordance with the following recommendations and the General Earthwork and Grading Specifications included in Appendix E. In case of conflict, the following recoaaaendations shall supersede those in Appendix E. 6.1.1 - - 6.1.2 Excavat i ens and Backfi 11 ,'- Excavations on site will likely require the use of heavy construction equipment. Mass excavation should be generally achievable to the proposed grades with a dozer and ripper shank (D-9 or equivalent). However, local areas of nonrippable bedrock may require minor blast- Utility trenches and foundation excavations may also require ;%lized jackhammering and/or blasting. Excavations deeper than 5 feet should be shored or should be laid back to 1:l (horizontal to vertical) if workers are to enter such excavations. All excavations should be performed in accordance with OSHA requirements. - Site Preoaratioa Prior to grading, all areas to receive structural fill or engineered structures should be cleared of surface and subsurface obstructions, including any existing debris resulting from the removal of e;;;;;;i structures or improvements, and stripped of vegetation. debris and vegetation should be disposed of off site. Holes resulting from removal of buried obstructions which extend below finished site grades should be replaced with suitable compacted fill material. Loose or suitable fill soils, as evaluated by the geotechnical con- sultant during grading, should be removed to competent soils. All areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 6 inches, brought to near-optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method 01557-78). The onsite soils may be used as trench backfill provided they are screened of organic matter, debris, and rock fragments greater than 6 inches in diameter. Trench backfill should be compacted in uniform lifts (not exceeding 6 inches in thickness) by mechanical means to at least 90 percent relative compaction (ASTM Test Method 01557-78). As an alternative to mechanical compaction of the native soils, trenches may be backfilled with granular backfill (sand equivalent of 30 or better) and densified to at least 90 percent relative compaction. -8- - 8881297-01 - 6.1.3 Fill Placement and ComoactiQn .- Excavation of the onsite materials will generate abundant rock frag- ments. In general, the materials generated from excavation should be used in * nonstructural fill areas. However, minor structural fills from onsite soils for proposed driveways may be feasible if a "skeleton bucket" is used to remove large rock fragments from the excavated soils. Materials used as compacted fill should be free of organic material, maximum dimension. debris, and rock fragments larger than 6 inches in All structural fill soils should be brought to near-optimum moisture conditions and compacted in uniform lifts to at ilast 90 percent relative compaction based on ASTM Test Method .D1557- The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equip- ment used. In general, fill should be placed in lifts not exceeding 8 inches in thickness. Placement and compaction of fill should be performed in accordance with the current, local grading ordinances, sound construction practice, and the General Earthwork and Grading Specifications (Appendix E). 6.1.4 Removal and Recomoaction The topsoil accumulations present on the site may be potentially compressible in their present state and may settle under the surcharge of fills or foundation loads. In areas that receive fill or other surface improvements, these soils should be excavated to competent bedrock materials, scarified, and recom acted in accordance with Section 6.1.1. Based on our subsurface exp oration, Y these potentially compressible soils across the site are on the order of 2 to 3 feet thick. The approximate depth of these soils encountered in our sub- surface exploration is presented on Figure 3 (rear of text). The thickness of these soils may vary across the site and should be checked at the time of grading operations by the geotechnical consult- ant. As mentioned in Section 4.2, a fill slope exists along the western edge of Venado Drive. of this investigation. Evaluation of this slope was beyond the sco e In addition, documentation of these fill sol *! s has not been reviewed by this office. We understand that the loose, undocumented fill which has been dumped over the top of slope will be removed as part of the slope grading, and the slope face will be reconstructed. We recoanaend that after removal of the undocumented fill the geotechnical consultant evaluate the contact of the existing fill slope with the proposed 2:l (horizontal to vertical) cut slope to determine if the fill was properly benched into the ori s inal hillside. If the fill slope is evaluated to have been improper y constructed, remedial grading measures such as construction of a fill slope key may be recommended. -9- LMllroll AlID ASSOClATf$. WC 8881297-01 - 9s ivdicated on Figure.3 aeveropment currently 1s (rear of.text), we understand that structural ,not planned in the area of undocumented- fill ^ . . identified in the nortnwest corner ot tne property. snouta future develo ment be considered in this area, we recommend an additional geotec nical I: investigation be performed to evaluate the engineering characteristics of the fill materials and to provide appropriate recoauaendations. 6.2 Slooe Stability - . . 6.2.1 Deco-Seaed Stability - Based on our analysis of the geotechnical conditions encountered during our investigation, it is our opinion that cut slopes excavated in the massive metavolcanic bedrock will be grossly stable at slope ratios of 2:l (horizontal to vertical) or flatter, assuming no adverse geolo ic conditions. However, 9 we recommend that the geotechnical consu tant document and geologically map all excavations, including cut slopes, during construction. The purpose of this mapping is to substantiate the geologic conditions assumed in our analysis. 6.2.2 Syrficial Slooe Stability Based on our experience with similar materials, we anticipate that the proposed slopes be constructed on the site will demonstrate acceptable factors of safety as related to surficial stability provided they are constructed in accordance with the recommendations contained herewith. We recommend that all cut and fill slopes be landscaped with drought- tolerant, slo e-stabilizing vegetation as soon as possible to minimize the potentia Y for erosion. In addition, we recommend that the site drainage recommendations outlined in Section 6.3 also be implemented to reduce the potential for excessive rilling. 6.3 Surface Drainaae and Erosion Surface drainage should be controlled at all times. The proposed residence should have appropriate drainage systems to collect roof runoff. Positive surface drainage should be provided to direct surface water away from the structure toward the street or suitable drainage facilities. Positive drainage may be accomplished by providing a minimum 2 percent gradient from the building. ~;~l~~ci~ unless Planters should not.be designed below grade adjacent to the provisions for drainage such as catch.basins and pipe drains In general, ponding of water should be avoided adjacent to the building'and concrete flatwork. - 10 - -. 8881297-01 6.4 1 - In order to help reduce the potential for excessive erosion ofoya$t slopes, we recotmaend berms and/or swales be provided along the to slopes and lot drainage directed such that surface runoff on the s Y ope faces is minimized. Protective measures to mitigate excessive site erosion durin construction should also be implemented in accordance with the latest loca 9 grading ordinances. Foundations and slabs should be designed in accordance with structural considerations and the following recoaaaendations. These recommendations assume that the soils encountered within 4 feet of pad grade have a very high potential for expansion. 6.4.1 Foundation2 We understand that currently the proposed design includes a combina- tion slab on grade and raised foundation. For the slab portion, post- tensioned slabs should be utilized and constructed in accordance with the recommendations of the structural engineer. Thickened erimeters for post-tensioned slabs should extend at least 18 inches be ow finish ! grade to help provide a barrier for migration of moisture into the slab subgrade. Living area slabs should be underlain by a 6-mil Visqueen moisture barrier midheight in a 4-inch layer of clean sand. Slab subgrade soils should be presoaked to 1.4 times optimum moisture to a depth of 24 inches prior to slab construction. For the raised foundation, continuous footings may be utilized, founded at a minimum depth of 24 inches below lowest adjacent grade. Continuous footings should be at least 12 inches in width and have a minimum reinforcement of two No. 5 rebars (one top and one bottom). Due to the very highly expansive nature of the site soils, isolated spread footings are not recommended. Footings and post-tensioned slabs as described above may be designed for an allowable bearing capacity of 2500 psf. A lateral resistance of 300 psf per foot of depth may be assumed for lateral loading. For sliding, a coefficient of friction of 0.30 may be assumed. Passive and frictional resistance may be combined provided the passive portion does not exceed two-thirds of the total resistance. These values may be increased by one-third for loads of short duration such as wind or seismic forces. - 11 - -- 888129741 - We recoaunend a minimum horizontal setback distance from the face of slopes for all structural footings and settlement-sensitive struc- tures. This distance is measured from the outside edge of the footing, horizontally to the slope face (or to the face of a retaining wall) and should be a minimum:of H/2, where H is the slope height (in feet). The setback should not be less than 5 feet and need not be greater than 10 feet. We should note that soils within the structural setback area retaining assess poor lateral stability, and improvements (such as wa Is, ! pools, sidewalks, fences, pavements, etc.) con- strutted within this setback area may be subject to lateral movement and/or differential settlement. In order to reduce the effects of differential settlement, we recom- mend foundations be deepened where necessary, such that they extend into the competent bedrock through any fill or compressible topsoil that may exist beneath the foundations. 6.4.2 Concrete Flatwork In order to reduce potential cracking of concrete flatwork due to expansive soils (patios, walkways, driveways, etc.), concrete should be at least 4 inches in thickness and be reinforced with 6x6-6/6 welded wire mesh placed midheight in the concrete. Walkways should be provided with construction joints (or sawcuts) spaced not more than 1.5 times the width of the walkway. Patios and driveways should provided with construction joints (or sawcuts) at intervals not ceeding 10 feet. be ex- 6.5 I&era1 Earth Pressures and Resistance ..- Embedded structural walls should be designed for lateral earth pressures exerted on them. The magnitude of these pressures depends on the amount of deformation that the wall can yield under load. If the wall can yield enough to mobilize the full shear strength of the soil, it can be designed for active pressure. If the wall cannot yield under the applied load, the shear strength of the soil cannot be mobilized and the earth pressure will be higher. Such walls should be designed for "at rest" conditions. If a structure moves toward the soil, the resulting resistance developed by the soil is the "passive" resistance. The recommended equivalent fluid pressures for each case for walls founded above the static ground water table are provided below: Sauivalent Fluid Weiaht focf). .- -- G onditiong !2wl Active 35 At Rest 55 Passive 300 2:1 50 90 150 (Sloping Down) - 12 - 8881297-01 - 6.6 6.7 - The above pressures assume nonexpansive, level backfill and free-draining conditions. Nonexpansive backfill should extend horizontally at least 0.5H from .the back of the wall where W is the wall height: It should be noted ;~~;,in areas where nonstructural fills are located adjacent to retaining the above criteria for nonexpansive backfill should be met to avoid excesiive pressure on retaining walls Retaining Walls should be provided with appropriate drainage as shown in Appendix E. Wall footings should be designed in accordance with the previous building foundation recommendations as stated in Section 6.4.1, and reinforced in accordance with structural considerations. The soil resistance against lateral loading consists of friction or adhesion at the base of the foundations and passive resistance against the embedded portion of the structure. Concrete foundations placed directly on properly compacted fill and/or competent formational materials may be designed using a coefficient of friction of 0.30 ficient of friction times the 6 total frictiona;nres;:;t::; equals coef- ead load). resistance applications, a passive resistance of 300 psf per foot of depth with a maximum value of 2,500 psf can be used for design. The allowable lateral resistance can be taken as the sum of the frictional resistance and the passive resistance not exceed two-thirds of the total al ! rovided the passive resistance does owable lateral resistance. The coef- ficient of friction and passive resistance values can be increased by one- third when considering loads of short duration such as wind or seismic loading. Jvoe of Cement for ConstructiQn Concrete in direct contact with soil or water that contains a high con- centration of soluble sulfates can be subject to chemical deterioration commonly known as "sulfate attack." Based on U.S. Bureau of Reclamation and Cement Industry Technical Connaittee of California criteria, a typical sample obtained and tested for the subject site possesses a negligible potential for "sulfate attack" (Appendix C). Foundation members and flatwork should not require the use of special sulfate resistant cement. Therefore, Type II cement (or equivalent) may be used for construction purposes. Pavement Sections Uesign of pavement sections for the proposed driveway was not included within the scope of this report. Pavement sections will depend largely on the subgrade soil conditions after grading. Pavement sections can be provided upon completion of grading based on laboratory R-value testing of subgrade soils. - - 13 - 8881297-01 - 6.8 Construction Observation - The recolrmendations provided in this report are based on preliminary design information and subsurface conditions disclosed by widely spaced trenches. The interpolated subsurface conditions should be checked .in the field during construction. Construction observation of all onsite excavations and field density testing of all compacted fill should be performed by a repre- sentative of this office so that construction is in accordance with the recommendations of this report. We recoannend that cut slopes be geologi- cally mapped by the geotechnical consultant during of R otentially adverse geologic conditions. Fina 9 rading for the presence project drawings should be c ecked by Leighton and Associates, Inc. before grading to see that the recommendations provided in this report are incorporated in project plans. - - - - - - 14 - - :- ~ i- 6.. .- MAJOR EARTHQUAKES AND RECENTLY ACTIVE FAULTS IN THE SOUTHERN CALIFORNIA REGION EXPLANATION’ ACllVE FAULTS ~OWKE wnoNs Fzy L M d WI zpw M!f, beaks Hol#me deposits hod seismc ocl~nly. Fault ngmml with wfacr N e during m historic Apporimla cpianfrd ORO d ewthqwkes that obzclmd 17699933. MO llUdK od m&cd b innrlruments pior lo 14 wea eslimded hem domoqc rcpwls orripe m lotens& H [Mifird Mmdi scdellaqmt~, lhkhm@y quidmt lo Richln Y6.0. 31 modaMP eafthqwkes. 7 mop md m gwl rorCk@e I16571 were reported b hr 164~yw~ paiod R69-033. s f*nbq,~*cdmR*codwm~, Molocmr Kkmic awily -Q Eolihwb epimlas simx 19% PJmkd hc.?! inpmrcdiammlmk z3flc&mw-Mdlka mpreomudnm~hhr4o-yu period 8334973, . salmu.I*I(w,knr~~cJ~~du ” CIL-*ri~~~*im.lu*li.‘~~*II~,CIdrlU*.rH *r,ewr~ot.*dr%Lr~*; arrmLulbl%; edm*rmc*6uF. REGIONAL SEISMICITY INDEX MAP project No. iw!L297-01 pIokct NamaBARELS/LA COSTA CI-.- 3/15/89 C.-..-- ..~ 3 E 5 5 F v C ( I ( F ( L TABLE 1 SEISMIC PARAMETERS FOR ACTIVE AND POTENTIALLY ACTIVE FAULTS Barels/La Costa Potential Causative fault Distance from Fault To Site (Miles) Maximum MAXIMUM PROBABLE EARTHQUAKE Credible (functional Basis Earthquake) Earthquake Peak Bedrock/ Predominant Bu;ation of Repeatable Period At Strong Richter Richter Horizontal Site In Shaking at Magnitude Magnitude Ground Acceleration** Seconds Site In (Gravity) Seconds :lsinore 23 7.6 7.3 0.23 0.35 25 ;an Andreas 66 8.5 8.3 0.09 0.63 5 ;an Jacinto 48 7.6 7.3 0.10 0.42 10 Iewport-Ingle- 27 7.0 6.5 0.11 0.29 12 vood (offshore) Coronado Banks 24 6.5 6.0 0.09 0.27 5 ioffshore) ;an Clemente 54 7.5 7.0 0.06 0.45 22 Ioffshore) I lose Canyon* 9 7.1 NA mm_- ---- -- Ioffshore) .a Nation* 26 6.5 NA -..w- --mm _- l l * This fault fs considered "potentially active," of the San Diego County area. based on our current knowledge of the geologic conditions For design purposes, the repeatable horizontal ground acceleration may be taken as 65 percent of the peak acceleration for the site with *20 miles of the epfcenter (after Ploessel and Slosson, 1974). - - - ._~ ,:- - I- - I_ l_i - L ._ - 8881297-01 TABLE 2 llIk1IUJll FOUNUATIOM MI SLA6 RECOIUIEWOATIONS FOR EXPANSIVE SOILS (ONE- AND lW-STOW RESIOENTIAL BUILOIU6S) L-Story Footlnps (s.. not. I) Z-Story Footings (SC. WOI. 1, Mln1.m Footlnp YIdth Smg. Door 5r.d. Be.. (Se* WOI. 2) Livlnp Cc. Floor Slabs (3.4 lmes 3. 4 and 5, 6arq. Floor Sl.bs (SC. notes 4 and 6) Pr.so.kiq of LM.q Are. ..d 6rr.g. 51.01 U.B.C. EXPUSION IkOEX O-20 I YEW LOU EXPANSIOII All footings 12' deep. R.lnforcment for co"tl""Lws footings: on. I(o. 4 brr too md bottcu. Esterfor fwtlngs 18' deep. Interior footings 12' deep. R.lnforc..Mt tar c.ntlnUOUs footings: on. "o. 4 bar top and Dottcs. Continuous: 12. for ,-story Contfn"o"s: 15' for z-story Isolated c01un: 24' A grad. beam 12' wld. x 12' deep (16' deep for Z-story) should be prwlded aross the g&-q. .ntranc.. "omln.1 4' thick slab. 6x6-10110 WF reinforcement at mid-height. K-m11 Visqueen molstur. brrrler on pad grad. ulth 1' smd above Visqwn. ~I"., 4. thick slab on pad gr.d.. 6.r.g. slrbs should be qwrter-ran. 6.woptimum ta 1 depth of 6'. U.6.C EX;M:O" I"UEX LOU EXPANSION A11 fwtinps 12' deep. R.inforc.m.nt for cOntl""."I fo.tl"gs: on. Ho. 4 bar tap and bottm. Exterior footings 16' deep. Interior footinps 12' deep. Il.lllforc.9.nt for cO"tl""o"s fclotfngs: on. HO. 4 bar top and b0tt.m. Contimws: 12' for ,-story Contln"o"s: IS' for z-story Isolated colwn: 24' A grsd. be.. 12' wld. I 12' deep (IO' deep for L-story) should be prwided wross the 6.r.g. .ntr.nc.. W.ln.1 4' thick sleb. 6x6-10110 WF reinforceaent 4t .ld-helgbt. 6-n,, Vlsqueen moIstwe bawler abor. 2' sand b.s. with I' sand &or. Visqueen. W.in.1 4' thick slab on 2' sand base. 6arsg. sl.bs should be qurrter-sari.. (I.21 s aptbun to a depth of 12'. U.B.E. EXPAlSIOW IWOEX 51-90 PEOIUH EXPANSIUN Exterior footl"6s IS' deep. Interior foot‘nps 12' deep. R.inforcn.nt for continuous footings: on. "0. 4 b.r top and bottom. Exterior footings 16' deep. Interior footiqs 12' deep. R.lnforca.nt for c.ntllluO"s footings: on. "0. 4 bar top and botto.. Contln”o”s: 12' for l-story COntlnYOUs: IS for z-story ,ro,at.d colun: 24' A gmd. hem 12' wide ‘ 16' deep should be provided across the 6.r.g. entrance. Nollln.1 4' thick slrb. 6x6-6/6 WF reinforcement at mld-height. S-ml1 Vlsqueen lolstur. berrier above 3' sand base with 1' sand above Vlsqueen. "c&n., 4' thick slab on 3' sand base. 6arq. should be quartcr- s."" or relnforced rlth 6x6-10110 WF at mld- height. (1.3) I optiau t. 1 depth of 16'. Ions: 1. Depth of interior or erterlor hottqs t. be ".sur.d frm lwest adjecmt flnlsh gr.d.. 2. The base of the gnd. b.r should be It the sw e1.vrti.n .I th.t of the .djoiniq footings. 3. Lirfq we. sI.bs q ey be tI.d to the fwtlnps .I dlrected by the structur.1 enp1ne.r. For "16" EXPIIISIOn: bus should be p1.c.d at 36 Inches on centers 1" the f..tl"6s .nd bent 3 feet Into the slab. U.B.C. EXPANSION IWEX 91-130 Will EXPANSION Erterlor footlrqs 24' deep. Intrrlor footlqs 16' deep. Rclnforc.m.nt for contln”o”s fOOtlqs: on. n.. 5 bar top .nd botta; 4lt.m.t.ly. two "0. 4 bars top. two No. 4 b.rs b&ta. Exterior footings 24' d..p. Interior fwtlngs 16' deep. R.lnforc.lllnt for c0nt1n!40us footings: on. !I.. 5 bar top .nd bottca; slt.r".t.ly. tro "0. 4 brrs top. two lo. 4 b.rs b&toll. Continuous: 12' for l-story ContlmmJs: 15' for z-story 1sol.t.d colun: 24' A grad. bea, Ii rid. I 24' d..p should be provided across the garage entrance. Full 4. thick s1.b. 6x6-616 WF relnfwcant at mid-height. S-m41 vIsqu.." ao1st!4rs b.rr1.r abr,". 4' sand bar. with 1' and 4b.v. Y~squeen. Hm‘nrl I- thick s1.b on 4' r.nd b.s.. 6rr.g. slrbs should be qurrter-sawn and reinforced with 6x6-616 WF rt mld-height. (1.4) I OptlW t. . depth of 24'. OweIs consist,ng Of NO. 3 4. It h.s been observed th.t welded rlr. f,brlc relnforcant selda stays .t the design height ulthln concrete sllbs. Ye r.c....nd the us. of Ho. 3 b.rs .t 24 fncbes O.C. fnst.,d of 6x6-10110 WF 4nd "o. 3 brrs .t I6 inches O.C. lnsteod of 6x6-616 WF. 5. 6-111 Visqueen sheeting h.s proved succ.ssfuI. Equlr.l.nts 4~. .ccept.bl.. 6. 6.r.q. sl.bs sbauld be 1s.l.t.d frm st" 11.11 fwtiqs with . q lnimw 316' felt expansion joint. =,I**- ,u jl.bs As an .lt.rnat. t. convention.1 f.""d.tions. bulldlqs q ey be supportrd on post-tensioned slabs to be designed by a str"ctur.1 enpineer In consult.tlon w‘th the ge.t.chnlc.1 consult.nt. In 4ddlti.n. II post-tensioned s1.b II also r.Co..."d.d for VERY "IS" .ip.nslon potential (Erp.nsion lnd., gr..t.r th." 130,. If encountered. Post-t.nslon.d slabs shwld h.". perlmeta footings embedded a .,n‘.w of 12 Inches beln the sdjrcent 30 feet "Itbout d ! r.d.. The sl.bs rb.uld be des‘gned such th.t they can be deformed .pprox‘m.t.Iy 1 inch rert‘crlly over . rldth ,,f stress In the went of shrlnkag. or sw.lllng of the wpportlng solIs. Lfvfng arc. slabs should be underI.‘" by I 6-n‘, Vlsq".." lolstur. b.rr1.r covered by I I-Inch 1.y.r of smd. Pr.ro.klq .I r.con.n.nd.d for conr.ntlon.I ‘Wtlngs (1.2, I opt,n". t. I d.pth of 12. (1.3) x .pt‘.um to 1 depth Of IS. and II.0 I optlm"" to 1 depth .f 24 Inches for "ED,"". HIS". and VERV "16" .xp.nslon potentlo, soils. respectively. are also suggested for post-tensioned s1.b systems. 3% YM -- 8881297-01 -. - 1. 2. 3. .- - 4. - 5. Bonilla, 6. .~- 1. 7. - 8. 9. -- 10. APPENOIX A REFERENCES I Albee, A.L., and Smith, J.L, 1966, Earthquake characteristics and fault activity in southern California a Lung, R. and Proctor, R., eds., Engineering Geologist in Southern California, Association of Engineering Geologists, Special Publication, dated October. Allen, C.R., Amand, P., Richter, C.F., and Nordquist, J.M., 1965, Relationship between seismicity and geologic structure in southern California, Seismological Society of America Bulletin, Vol. 55, No. 4, p. 753-797. Bell, J.MjAu;;;;, Dimensionless Parameters for Homogeneous Earth Slopes, So11 Mechanics and Foundations Division, Amencan Society of Civii Engineers, No. SM5, September. Bolt, B.A., 1973, Duration of strong ground motion, Proc. Fifth W;;;d Conference on Earthquake Engineering, Rome, Paper No. , pp. 1304-1313, dated June. M.J., 1970, Surface faulting and related effects b Wiegel, R. (editor), Earthquake Engineering, Prentice-Hall, Inc., New Jersey, pp. 47-74. Greensfelder, R.W., 1974, Maximum credible rock acceleration from earthquakes in California, California Division of Mines and Geology, Map Sheet 23. Hannan, D.L., 1975, Faulting in the Oceanside, Carlsbad, and Vista areas, ;;;thern San Diego County, California 111 Ross, A. and Dowlen, R.J., Studies on the geology of Camp Pendleton and western San Oieg: County, California, San Oiego Association of Geologist Field Trip Guidebook, pp. 56-60. Hart, 1985, Fault-rupture hazard zones in California, Alquist-Priolo Special Studies Zones Act of 1972 with index to special study zones maps: De artment Pu lication 42. 1 of Conservation, Division of Mines and Geology, Special Jennings, C.W., 1975, Fault map of California, Scale 1:750,000: California Division of Mines and Geology, Geologic Map No. 1 Lamar, D.L., Merifield, P.M., and Proctor, R-J., 1973, Earthquake recurrence intervals on major faults in southern California j,~ Moran, D.E., Slosson, J.E., Stone, R.O., Yelverton, California, eds., 1973, Geology, seismicity, and environmental impact: Association of Engineering Geologists, Special publication. - - A-i - - .- .- - - - - ,.- .~- - - 8881297-01 REFERENCES 1CONTINUEDL 11. Leighton and Awociates, Inc., 1983, Seismic safety element for the City of San Diego. 12. , Unpublished in-house data. 13. Peterson, G.L., and Abbott, P.L., 1975, Paleocene age of lateritic paleosol, r;tern San DIego County, California, g Ross, A., and Dowlen, eds, Studies on the Geology of Camp Pendleton and Western San O;egh County, California, San Oiego Association of Geologists Field Trip Guidebook, pp. 60-65. 14. - 1981, Early Cenozoic torrid climate, coastal southern California, j,~i ' Abbott, P.L. and O'Dunn, S., eds., Geologic Investigation of the Coastal Plain, San Oiego County, California, San Diego Association of Geologists Field Trip Guidebook, pp. 90-96. 15. Ploessel, M.R., and Slosson, J.E., 1974, Repeatable high ground accelera- tions from earthquakes-important design criteria, California Geology, Vol. 27, No. 9, dated September. 16. R.D.A. Design & Drafting Services, 1989, Site plan/ rading plan, a proposed residence for: Mr. and Mrs. Ronald Bare s, 3 Job No. Barels, Scale l"-16', dated February 28. 17. San Dieguito Soils, Inc., 1984, S;bl yd geologic investigation of Lot 473, La Costa Vale, Unit No. SDS 7377, dated August i3.’ Carlsbad, California, ProJect 24. Weber, F. Harold Jr., 1982, Recent slope failures, ancient landslides and related geology of the north-central coastal area, San Diego County, California, California Division of Mines and Geology, Open File Report 82-12, LA. AERIAL PHOTOGRAPHS Source Flioht Photo No. Scale Date County of San Diego AXN-8M 73 and 74 1"=1,667' 04-11-53 - - A - ii I 1 , / I I I I I I I 1, I i- Equipment: c GEOLOGIC AITITUDES Project Name: Barels/La Costa Lossed By: BJM Project Number: 8881297-01 Elevation: *298’ TRENCH NO. T-l ase 5BOE Backhoe Location: See Geotechnical Mao DATE: February 22, 1989 DESCRIPTION: GEOLOGIC UNIT TOPSOIL: q Medium brown, damp, loose, clayey, sandy silt; @ 0.5' grades Topsoil to dark red-brown, slightly moist, firm, sandy, silty clay; roots and rootlets throughout 3 a j:N36E/83E 3 b j:N33W/32S GRAPHIC REPRE I WEATHERED SANTIAGO PEAK VOLCANICS: cl B Brown, moist, firm, silty clay with floaters of metavol- JSP canic rock to 2 feet in longest dimenfion;grades to mottled (weathered) red-brown and gray, cla ey, medium- to coarse-grained sand and gravel; grades to C ii rock rota1 Depth = 5 Feet (at refusal) lo Ground Water Encountered backfilled 2/22/BQ SANTIAGO PEAK VOLCANICS: 0 C Gray-green, very hard, jointed and fractured, metavolcanic JSP ,NTATION East Wall SCALE: 1" = 5' SUR -, I I I I I I I I ENGINEERING PROPER c. iA b L-l . IL/CL ;P-GC I I PACE SL0PE:*1-2° TRBMD: N35E. I I I I - z. 3:: E 2 3 l@ to 3 I I I 1 I I I I I I / I I Project Name: Bare:s/La Costa LogRed By: BJM Project Number: 8881297~01 Elevation: i290’ TRENCH NO. T-2 3quipment: & GEOLOGIC AlTIlUDES as T 3j:N62E/67W b ~:N43E/57W e 5BOE Backhoe Location: See Geotechnical Map DATE: February 22, 1989 DESCRIPTION: TOPSOIL: 0 A Dark red-brown, damp to moist, firm, slightly sandy, silty clay; scattered chunks of gray-green. metavolcanic rock; roots and rootlets throughout HIGHLY WEATHERED SANTIAGO PEAK VOLCANICS: cl B Yellow-tan, damp, dense, clayey, silty sand to clayey, sandy silt; contains small chunks of metavolcanic rock; the original bedrock structure is apparent; jointed; joints are clay-lined Total Depth = 10.5 Feet (easy digging) Geologically Logged to 6 Feet No Ground Water Encountered Backfilled 2/22/89 GRAPHIC REPRESENTATION North Wall SCALE: 1” = 5’ SURFACE SlnP CEOLDCIC UNIT Topsoil JSP (weathere -r -t I I I I CL X/ML :*8-looTREND: N7' I ,ERIM lOPER 7 - C. Y”, 2 I I I I I /, I I I / / Project Name: Barels/La Costa Logged By: BJM 'rOject Number: BBBI2g7-01 ENGINEERING PROPERTiES Elevation: *296’ TRENCH NO. T-3 c Iquipment : Case 5BOE Backhoe GC:: Location: See Geotechnical Map L, g 2: sg GEOKIGIC GEOLOGIC t, o &I AITITIJDES DATE: February 22, 1989 DESCRIPTION: UNIT 5 u” . TOPSOIL: q Dark red-brown, damp, loose, silty clay to clayey silt; Topsoil CL/ML @ 6" grades to dark red-brown, moist, soft to firm clay; CL roots and rootlets throughout WEATHERED SANTIAGO PEAK VOLCANICS: cl B Yellow-tan, damp, medium dense to firm, silty, fine-grained JSP SMfML cl sand to sandy silt mixed with bedrock; grades to q (weathered) C Chunky pieces of highly fractured, gray-green, metavol- canic rock; stained red along fracture and joints 0 1 a 6 to 8’ -I!- Total Depth = 9 Feet (at refusal) Geologically Logged to 6.5 Feet No Ground Water Encountered ackfilled 2/22/89 GRAPHIC REPRESENTATION North Wall SCALE: 1” = 5’ SURFACE SLOPE:*g-looTREND: N6BW - -- East Wall I / / I I I 1 I / / 1 ‘reject Name: Barels/La Costa LogBed By: BJM ‘reject Number: 888129 7-01 Elevation: *282’ ENGINEERING PROPERTIES TRENCH NO. iquipment : T-4 c Case 5BOE Backhoe Location: See Geotechnical Map t, GEOLOGIC I-J Pi .g 5: AITITUDES DATE: February 22, 1989 DESCRIPTION: GEOLOGIC ’ t, n 5 ,- UNIT 0 TOPSOIL: q Dark red-brown, moist, firm. slightly sandy, silty clay to very clayey, sandy silt; rootlets throughout Topsoil CL/ML 0 @ 0.5 SANTIAGO PEAK VOLCANICS: to 2' gj:N56E/55E q Highly jointed and fractured, gray-green, metavolcanic 2@ - 9 j:N47W/72N rock; stained red; rippable; large floaters of bedrock JSP 0 3 to5' surrounded by clay along the joint surfaces Total Depth = 6.5 Feet (on boulder) Still Rippable Large Chunks 1 to 2 Foot Square Were Excavated No Ground Water Encountered Backfilled 2/22/89 GRAPHIC REPRESENTATION North Wall SCALE: l@l = 5' SURFACE SLOPE:*l8-20yREND: N71W- / I, I I ! i I I I / I I I 1 I I Project Name: Barels/La Costa Logged By: BJM 'reject Number: _88612g7-()1 ENGINEERING PROPERTIES Elevation: *2B2' TRENCH NO. ‘r-5 c iquipment: Case 5BOE Backhoe Location: See Geotechnical Map id sz GEOUXIC i-J &j g sz. ATTITUDES DATE : February 22, 1989 DESCRIPTION: GEOLOGIC' t, n UNIT 3 u” TOPSOIL: cl A Dark red-brown, damp, loose, slightly sandy, clayey silt; Topsoil ML 1 @ @ 0.5' grades to dark red-brown, moist, firm, silty clay 8 TX .5 with scattered bedrock floaters; rootlets throughout; to 2' grades tom . WEATHERED SANTIAGO PEAK VOLCANICS: El B Yellow-tan-brown, damp to moist, stiff, silty, sandy clay;' JSP CL a@ El grades to q 2to 4' "Crumbly," yellow-tan, damp, firm to stiff, sandy, silty. CL clay; appears to be highly weathered, fractured bedrock (original structure apparent) Total Depth = 7.5 Feet -L Geologically Logged to 6 Feet No Ground Water Encountered Bacfilled 2/22/89 GRAPHIC REPRESENTAi”ON North Wall SCALE: I#@ D 5' SURFACE SLOPE: 10” TREND: N75W - 8881297-01 .- .- - - - APPENDIX C SAMPLING AND LABORATORY TESTING PROCEDURES AND LABORATORY TEST RESULTS @iPLING PROCEDURES Disturbed Samoles: Bulk samples of representative materials were also obtained from the trenches, bagged, and transported to our laboratory for testing. LABORATORY TESTING PROCEDURFS Exoansion Index Test: The expansion potential of a selected material was evaluated by the Expansion Index Test, U.B.C. Standard No. 29-2. Specimens were remolded at near-optimum moisture content to 90 percent relative compaction under a given compactive energy to approximately 50 percent saturation. The prepared specimens (4-inch diameter by l-inch length were loaded to an equivalent 144 psf 4 surcharge and inundated with tap water unti volumetric equilibrium was reached. The results of this test are presented in the test data. Soluble Sulfate Tests: The percent of soluble sulfates in a representative sample was determined by the California Materials Method No. 417 utilizing a hand-held terbidmeter. GENERAL NOTE: All references to the American Society for Testing and Materials (ASTM) imply the latest standards. - - - c-i - - - - - - - - - - - . - - - - ,- - - EXPANSION INDEX TEST RESULTS ‘EST SAMPLE INrrlAL COMPACTED FNAL VOLUMETRIC EXPANSION EXPANSION NO. LOCATION MOlsluRE DRY DENsrrY Moy$l?E (CL) (PCFI SWELL m INDEX PoTpmAL 1 T-5;@@ 13.5 87.3 42.7 13.4 134 Very High 2 - 4’ 8881297-01 LilGHlDN AND ASSOCIAlS BARELS/LA COSTA -. - - - - - - - -~ - - - ,- SAMPLE + r-2; @ f3 2 - 51 SOLUBLE SULFATES READINQ PPM 400 POTENTIAL DEQREE X SULFATES OF SULFATE ATTACK 0.04 Negligible ~RELS/LA COSTA 8881297-01 APPENIIX 0 SLOPE MAINTENANCE GUIDELINES FOR HOMEOWNERS JIPS FOR THE HOMEOWNER Homesites, in general, and hillside lots, in particular, need maintenance to continue to function and retain their value. Many homeowners are unaware' of this and allow deterioration of their property. In addition to his own property, the homeowner may be subject to liability for damage occurring to neighboring properties as a result of his negligence. It is therefore important to familiarize homeowners with some guidelines for maintenance of their properties and make them aware of the importance of maintenance. - Nature slowly wears away land, but human activities such as construction increase the rate of erosion 200, even 2,000 times that amount. When we remove vegetation or other objects that hold soil in place, we expose it to the action of wind and water and increase its chances of eroding. The following maintenance guidelines are provided for the protection of the homeowner's investment, and should be employed throughout the year. - a) b) cl 4 4 f) 9) Care should be taken that slopes, terraces, berms (ridges at crown of slopes), and proper lot drainage are not disturbed. Surface drainage should be conducted from the rear yard to the street by a graded swale through the sideyard, or alternative approved devices. In general, roof and yard runoff should be storm drain by nonerosive devices such as gutters, and driveways. Drainage systems expert consultation. conducted to either the street or sidewalks, drainage pipes, ground should not be altered without All drains should be kept cleaned and unclogged, including gutters and downspouts. Terrace drains or Gunite ditches be kept free of debris to allow proper draina e. drainage system shou d 9 During heavy rain $ou,$ be inspected. Pro lems, & performance of the 'such as gullying and ponding, if observed, should be corrected as soon as possible. Any leakage from pools, water lines, etc. or bypassing of drains should be repaired as soon as possible. Animal burrows should be filled since they may cause diversion of surface runoff, promote accelerated erosion, and even trigger shallow soil failures. Slopes should not be altered without expert consultation. Whenever a homeowner plans a significant topographic modification of the lot or slope, a qualified geotechnical consultant chnuld be contacted. If plans for modification of cut, fill, or natural slopes within a property are considered, an engineering geologist should be consulted. Any over- steepening may result in a need for expensive retaining devices. Undercutting of the bottom of a slope may lead to slope instability or failure and should not be undertaken without expert consultation. D-i 8881297-01 SLOPE MAINTENANCE GUIDELINES FOR HOMEOWNERS (CONTINUEDL .~. - . . - h) If unusual cracking, settling, or earth slippage occurs on the property, the homeowner should consult a qualified soil engineer or an engineering geologist immediately. i) The most common causes of slope erosion and shallow slope failures are as follows: l Gross neglect of the care and maintenance of the slopes and drainage devices. a Inadequate and/or improper planting. (Barren areas should be replanted as soon as possible.) l Excessive or insufficient irrigation or diversion of runoff over the slope. l Foot traffic on slopes destroying vegetation and exposing soil to erosion potential. j) Homeowners should not let conditions on their property create a problem for their neighbors. Cooperation with neighbors could prevent problems and also increase the aesthetic attractiveness of the property. Winter Alert It is especially important to "winterize" your property by mid-September. Do not wait until spring to put in landscaping. You need winter protection. Final landscaping can be done later. Inexpensive measures installed by mid-September will give you protection quickly that will last all during the wet season. l Check before storms to see that drains, gutters, downspouts, and ditches are not clogged by leaves and rubble. l Check after major storms to be sure drains are clear and vegetation is holding on slopes. Repair as necessary. l Spot seed any bare areas. Broadcast seeds or use a mechanical seeder. A typical slope or bare areas can be done in less than one hour. l Give seeds a boost with fertilizer. l Mulch if you can, with grass clippings and leaves, bark chips or straw. l Use netting to hold soil and seeds on steep slopes. o Check with your landscape architect or local nursery for advise. l Prepare berms and ditches to drain surface runoff water away from problem areas such as steep, bare slopes. l Prepare bare areas on slopes for seeding by raking the surface to loosen and roughen soil so it will hold seeds. - 0 - ii - SLOPE MAINTENANCE GUIDELINES FOR HOMEOWNERS (CONTINUED1 - KMlRUCTIoW - a Plan construction activities during spring and summer so that erosion control measures can be in place when the rain comes. e Examine your site carefully before building. Be aware of the slope, drainage patterns and soil types. stabilization work. Proper site design will help you avoid expensive - 0 Preserve existing vegetation as much as possible. Vegetation will naturally curb erosion, improve the a pearance and the value of your property, and reduce the cost of landscaping e ater. - a Use fencing to protect plants from fill material and traffic. If you have to pave near trees, do so with permeable asphalt or porous paving blocks. ,- s Preserve the natural contours of the land and disturb the earth as little as possible. Limit the time in which graded areas are exposed. a Minimize the length and steepness of slopes by benching, terracing, or constructing diversion structures. slope and improve its appearance. Landscape benched areas to stabilize the 0 As soon as possible after grading a site, plant vegetation on all areas that are not to be paved or otherwise covered. ‘- TMWRARY MWRES TO STABILIZE THE SOIL Grass provides the cheapest and most effective short-term erosion control. It grows quickly and covers the ground completely. To find the best seed mixtures and plants for your area, check with your local landscape architect, local nursery, or the U.S. Department of Agriculture Soil Conservation Service. - 8881297-01 Mulches hold soil moisture and provide ground protection from rain damage. They also provide a favorable environment for starting and growing plants. Easy-to- obtain mulches are grass clippings, leaves, sawdust, bark chips, and straw. Straw mulch is nearly 100 percent effective when held in place by spra ing with an organic glue or wood fiber (tackifiers), by punching it into the sol with a 4 shovel or roller, or by tacking a netting over it. .- Commercial ap lications fertilizers ( ydraulic R of wood fibprs combined with various seeds and mulching) Are effective in stabilizing sloped areas. Hydraulic mulching with a tackifier should be done in two separate applications: the first composed of seed fertilizer and half the mulch, the second composed of the remaining mulch and tackifier. Coaanercial hydraulic mulch ap licators 4 - who also provide other erosion control services - are listed under the phone book. andscaping" in D - iii 8881297-01 SLOPE MAINTENANCE GUIDELINES FOR HOMEOWNFRS fCONTINUE0) Mats of excelsior, jute netting, and plastic sheets can be effective temporary covers, but they must be in contact with the soils and fastened securely to work effectively. Roof drainaae can be collected in barrels or storage containers or routed into lawns, planter boxes, and gardens. Be sure to cover stored water so you do not collect mosquitos. Excessive runoff should be directed away from your house. Too much water can damage trees and make foundations unstable. - STRUCTURAL RUNDFF CmLS -. Even with proper timing and planting, you may need to protect disturbed areas from rainfall until the plans have time to establish themselves. Or you may need permanent ways to transport water across your property so that it does not cause erosion. J;,k;;i water from carrying soil from your site and dumping-it into nearby lots, streams and channels, you need ways to reduce its volume and speed. Some eximples of what you might use are: 0 .- l 0 e a - a - a - - - - Riprap (rock lining) - to protect channel banks from erosive water flow. Sediment trap - to stop runoff carrying sediment and trap the sediment. Storm drain outlet protection - to reduce the speed of water flowing from a pipe onto open ground or into a natural channel. Diversion dike or perimeter dike - to divert excess water to places where it can be disposed of properly. Straw bale dike - to stop and detain sediment from small unprotected areas (a short-term measure). Perimeter swale - to divert runoff from a disturbed area or to contain runoff within a disturbed area. Grade stabilization structure - to carry concentrated runoff down a slope. D - iv 8881297-01 APPWIX E GENERAL EARTHWORK AND GRADING SPECIFICATIONS - - _- 1.0 General Intent These specifications are presented as general procedures and recommendations for grading and earthwork to be utilized in conjunction with the approved grading plans. These general earthwork and grading specifications are a part of the recommendations contained in the geotechnical report and shall be superseded by the 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 supers$e W;; specifications or the recommendations of the geotechnical report. 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 Testinq Prior to the commencement of grading, a qualified geotechnical consultant should be employed for the purpose of observing earthwork rocedures and testing the fills for conformance with the recommendations of t e R geotechni- cal report and these specifications. It shall be the responsibility of the contractor to assist the consultant and keep him apprised of work schedules and changes, at least 24 hours in advance, so that he may schedule his per- sonnel accordingly. No grading operations should be performed without the knowledge of the 9 eotechnical consultant. The contractor shall not assume that the geotechnica consultant is aware of all 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 in the geotechnical report and the approved grading lans observation of the geotechnica 7 not withstanding the testing and consultant. If, in the opinion of the consultant, unsatisfactory conditions, such as unsuitable soil, poor mois- ture condition, inadequate compaction, adverse weather, etc., are resulting in a quality of work less than recoannended 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. Maximum dry density tests used to evaluate the degree of compaction should be performed in general accordance with the latest version of the American Society for testing and Materials test method ASTM 01557. 3.0 Preoaration of Areas to be Filled 3.1 Glearina and Grubbinq: 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. E-i - 8881297-01 - 3.2 - - 3.3 - - 3.4 3.5 3.6 3.7 GEWERAL EARTWWORK AND GRADING SPECIFICATIONS KontinuedI The geotechnical consultant should evaluate the .extent of these removals depending on specific site conditions. In general, no more than 1 7 ercent (by volume) of the fill material should consist of these materia s and nesting of these materials should not be allowed. Processinq: 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 uneven features which would inhibit uniform compaction. 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 overex- cavated down to competent ground, as evaluated by the geotechnical consultant. For purposes of determining quantities of materials over- excavated, a licensed land surveyor/civil engineer should be utilized. Moisture Conditioninq: Overexcavated and processed soils should be watered, dried-back, blended, and/or mixed, as necessary to attain a uniform moisture content near optimum. Recomoaction: 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 or as otherwise recommended by the geotechnical consultant. Benchinq: Where fills are,to be placed on ground with slopes steeper ;i;hahi;l (horizontal to vertical b* the ground should be stepped or The lowest bench s ould be a minimum of 15 feet wide, at least 2'feet into competent material as evaluated by the geotechnical consultant. Other benches should be excavated into competent material as evaluated by the geotechnical consultant. Ground sloping flatter than 5:l should be benched or otherwise overexcavated when recoasaended by the geotechnical consultant. Evaluation of Fil? Areas: All areas to receive fill, including processed areas, removal areas, and toe-of-fill benches, should be evaluated by the geotechnical consultant prior to fill placement. E - ii - .~ - .~ - .- ,- - - - - 8881297-01 GENERAL EARTHWORK AND 6RADIN6 SPECIFICATIONS (Continued1 4.0 Fill Material , 4.1 General: Material to be laced as fill should be sufficiently free of matter and R ot er deleterious substances and should be ~C~~!:~ed by the geotechnical consultant prior to plaiement. Soils of poor gradation, expansion, or strength characteristics should be placed as recommended by the geotechnical consultant or mixed with other soils to achieve satisfactory fill material. 4.2 Oversize: Oversize material, defined as rock or other irreducible material with a maximum dimension greater than 6 inches, should not be buried or placed in fills, unless the location, materials, and disposal methods are specifically recoanaended by the geotechnical consultant. Oversize disposal operations should be such that nesting of oversize material does not occur, and such that the oversize material is com- pletely surrounded by compacted or densified fill. Oversize materials should not be placed within 10 feet vertically of finish grade, within 2 feet of future utilities or underground construction, or within 15 feet horizontally of slope faces, in accordance with the attached detail. 4.3 Imoort: If importing of fill material is required fo;e;;;f;ng,4tie import material should meet the requirements of Sufficient time should be give to allow the geotechnical consultant'to observe (and test, if necessary) the proposed import materials. 5.0 Fill Placement and Comoaction 5.1 5.2 5.3 Fill Lifts: Fill material should previously evaluated to receive proximately 6 inches in compacted spread evenly and thoroughly mixed moisture throughout. be placed .in areas prepared and fill, in near-horizontal layers a - thickness. Each layer should ge to attain uniformity of material and Moisture Conditioninq: Fill soils should be watered, dried-back, blended, and/or mixed, as necessary to attain a uniform moisture con- tent near optimum. Comoaction 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 (unless otherwise specified). Compaction equipment should be adequately sized and be either specifi- cally designed for soil compaction or of proven reliability, to efficiently achieve the specified degree and uniformity of compaction. E - iii .- 8881297-01 GENERAL EARTHWRK AND GRADING SPECIFICATIOWS [ContinuedI 6.0 - 7.0 .- 8.0 Duantitv Determination 5.4 5.5 Fill Slooep: Compacting of slopes should be accompli,shed, in addi;;;; to normal compacting procedures, by backrolling of slopes sheepsfoot rollers at increments of 3 to 4 feet in fill elevation gain, or by other methods producing satisfactory results. At the completion of 9 rading, the relative compaction of the fill out to the slope face shou d be at least 90 percent. Compaction Testinq: Field tests of the moisture content and degree of compaction of the fill soils should be performed by the 9 eotechnical consultant. The location and frequency of tests shou d be at the consultant's discretion based on field conditions encountered. In general, the tests should be taken at approximate intervals of 2 fe;; in vertical rise and/or 1,000 cubic yards of compacted fill soils. addition, on slope faces, as a guideline approximately one test should be taken for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. Subdrain installation Subdrain systems, if recommended should be installed in areas previously evaluated for suitability by the geotechnical consultant, to conform to the approximate alignment and details shown on the plans or herein. The sub- drain location or materials should not be changed or modified unless recommended by the geotechnical consultant. The consultant, however, may recommend chang;fl in subdrain line or grade depending on conditions encountered. subdrains should be surveyed by a licensed land surveyor/civil engineer for line and grade after installation. Sufficient time shall be allowed for the surveys, prior to commencement of filling over the subdrains. Excavation Excavations and cut slopes should be evaluated by a representative of the geotechnical consultant (as necessary) during grading. If directed b the geotechnical consultant, further excavation, overexcavation, and 4 refi ling of cut areas and/or remedial grading of cut slopes (i.e., stability fills or slope buttresses) may be recommended. i;;,!Tposes of.determinino q;;;;;;ies determining of materials excavated during grading "‘It! of overexcavation, a licensed land surveyor/civil engineer should be utilized. E - iv - ..- - - - - ,._~ - - .~- -~ - .- STABILITY FILL / BUTTRESS DETAIL KEY WIDTH AS NOTED ON QRAOINQ PLANS lS* MIN. f SEE T-CONNECTION 0’ MIN. DETAIL OVERLAq ,; FILTER FABRIC - iNVELOPE (YIRAFI 40N OR APPROVED :OU~VALENT)* i= MIN. BEDDINQ #TED SUBDRAIN TRENCH DETAIL * IF CALTRANS CLASS 2 PERMEABLE MATERIAL IS USED IN PLACE OF 3/4*-l-112* QRAVEL. FILTER FABRIC MAY SE DELETED SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Sieve Size % Passing 1" 100 314" 90-100 3/a" 40-100 NO. 4 25-40 No. a la-33 No. 30 5-15 No. 50 o-7 No. 200 o-3 Sand Equivalent>75 NOTES: for buttwoo dlmrn~lono. so. 2oolochnlcoI roportlplwo. Accuol dlmonrlonr of buttroar wtd wbdrolr may bo chonaod by the qootochnlcol conrultont bosod on flold condltlons. SUBDRAIN INSTALLATION-Subdroln pip. should bo In~t~llod with porfor~tlonr down . . doplctod. At locotlonr rocommondod by the 2ootochnlcol~conwltont. nonporforotod plpo should bo Inotallod SUSDRAIN TYPE-Subdroln typo rhould bo Acrylonltrll. Sutodlono Styron. (A.S.S.1. Polyvinyl Chlorldo (PVC) 01 approved l qulrolont. Clone 12S,SOR 32.5 should bo urod for morlmum till depths of 3S foot Clooo 204SDR 21 should bo umd for morlmum fill dopthl of 100 foot. - - - .- - - - KEY AND BENCHING DETAILS FILL SLOPE PROJECT 1 TO 1 LINE FROM TOE OF SLOPE TO COMPETENT MATERIAL EXISTlNQ SROUND SURFACE MATERIAL DEPTH BENCH (KEW FILL-OVER-CUT SLOPE CUT-OVER-FILL SLOPE L CIJT SLOPE (TO SE EXCAVATED PRIOR TO FILL I PLACEMENT) PROJECT 1 TO 1 ‘MATERIAL LINE FROM TOE NOTE: Sack drain may be recommended by the geotechnical consultant bared on actual field conditions encountered. Bench dimension recommendation6 may rho be altered based on field candltiana encountered. SIDE HILL STABILITY FILL DETAIL . FINN SHED SLOPE FACE PROJECT 1 TO 1 LINE F!W+l TOP OF SLOPE TO OUTSIDE EDQE OF KEY OVERBURDEN OR UNSUITABLE AND REC RECOsuenueo 8~ QEOTECHNICAL CONS BASED ON ACTUAL c CONDITIONS ENCOU :OYPACTION MAY SE . ..a--.-__ _.- -lE ,i;TANT . . ‘NTEREO. OMPETENT SEDROCK OR IAL AS EVALUATED SY THE QEOTECliNlCAL CONSULTANT NOTE: Subdrsin details and key width recommendations to be provided based on exposed subsurface condition8 - - - - -, 2 - - - - - TRANSlTl.ON LOT DETAILS CUT-FILL LOT EXISTINQ QROUND SURFACE I (OVEREXCAVATE AN0 RECOMPACT COMPETENT BEDROCK 7 OR MATERIAL EVALUATED J J ~SY THE QEOTECHNICAL CONSULTANT CUT LOT EXISTINQ QROUND SURFACE OVEREXCAVATE AND RECOMPACT ~~$%JE~T~c~~~/ CONSULTANT *NOTE: Deeper or laterally more extensive overexckation and recompaction may be recommended by the geotechnicai conruitant bared on actual field conditions encountered’ and iocationr of propored improvementr CANYON SUBDRAIN DETAILS - TRENCH, SEE BELOW SUBDRAIN TRENCH DETAILS .= “I” ““cq~p ” “..... “.C, \ FILTER FABRIC ENVELOPE ,(MIRAFI 140N OR APPROVED 6. MIN. OVERLAP , /, AZ= - S’ MIN. Li COYER. - 6’ # MIN. - l IF CALTRANS CLASS 2 PERWEAI PERPORATED MATERIAL IS USED IN PLACE. OF PIPE 314*-l-112= QRAVEL. FUTER FA2 MAY SE DELETED DETAIL OF CANYON SUBDRAIN TERMINAL SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Sieve Size X Passing :/4” II 90-100 100 318” 40-100 No. 4 25-40 No. 8 18-33 No. 30 5-15 No. 50 o-7 No. 200 o-3 Sand Equivalent>75 SubdraIn rhould bo constructed only on compotant matorI 6I waluated by the geotrchntc6t con6ult6nt. SUSORAIN INSTALLATION SubdraIn 6lF. lhould b. lnat6lled with porforatlona down . . d*Dlct.d. At locatIon recommendad by the 6*otechnlcal conwltant. nonPwfor6tod plp6 should bq In616lled. SUSORAIN TYPE-Subdr6ln type should be Acrylonitrll, Butadlww Styrene (A.S.8.). Polyrlnyt Chloride (PVC) or 6PDrOY~d l qulvalent. Claao 124SDR 32.6 ahould be wed for maxImum fill doptha of 36 feet. EI~~J 2DD,SDR 21 should 30 wad for m6xlmum fllt depth6 of 100 1a.t. ,~. - - ,~- - - - - ~, /- ;~ jam- i. ; .- Jo . . _. - L__ RETAINING WALL DRAINAGE DETAIL RETAININQ WALL- WALL’ WATERPROOFINQ PER ARCHITECT’S SPECIFICATIONS FINISH QRAOE > SOIL BACKFILL. COMPACTED TO 90 PERCENT RELATIVE COMPACTION* FILTER FABRIC ENVELOPE (YIRAFI 14011 OR APPROVED EQUIVALENT1 * 314’~l-112= CLEAN ORAVELn 4%iIN3 OIAYETER PERFORATED ~PVC PIPE (SCHEDULE 40 OR EQUIVALENT) WITH PERFORATIONS ORIENTED DOWN AS OEPlCTEO MINIMUM 1 PERCENT QRAOIENT TO SUITABLE OUTLET giir -3’ MIN. SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Sieve Size X Par-:,,y :;v 3/a* No. 4 No. a 18-33 No. 30 5-15 No. 50 No. 200 ;:: Sand Equivalent>75 \ COMPETENT BEDROCK OR MATERIAL A8 EVALUATED BY THE QEOTECHNICAL CONSULTANT *BASED ON ASTM D1567 l l IF CALTRANS CLASS 2 PERMEABLE MATERIAL (SEE QRA~AT~~N TO LEFT) IS USED IN PLACE OF 3/4*-1-l/2= QRAVEL. FILTER FABRIC MAY BE DELETED. CALTRANS CLASS 2 PERMEABLE MATERIAL SHOULD SE COMPACTED TO SO PERCENT RELATIVE COMPACTION l NOT TO SCALE .- - - * ,~L % r- : i- - -- - ROCK DISPOSAL DETAIL FINISH ORAPE DETAIL _------------es _------------- --------------- _-_------------ _-------- --A-- _-_--------- --- TYPICAL PROFILE ALONG WINDROW 1) Rock with maximum dimensions greater than 6 inches should not be used within 10 feet vertically of.flnlsh 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 4 feet should not be utillzed in fills. 31 Rock placement, flooding of granular soil, and fill placement should be observed by th’ geoteohnical consultant. 4) Maxlmum size and spacing of wlndrows should be In accordance with the above detail: Width of wlndrow should not exceed 4 feet. Wlndrows should be staggered vertically (as depicted). 6) Rock should be placed In excavated trenches. Granular soil (SE. greater than or egua to 301 rhould be flooded In the wlndrow to completely fill voids around and beneath rocks.