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Home My WebLink About6024-1; ; Geotechnical Evaluation La Costa Avenue Slope Failure; 2008-02-25GEOTECHNICAL EVALUATION LA COSTA AVENUE SLOPE FAILURE CARLSBAD, CALIFORNIA PREPARED FOR City of Carlsbad 1635 Faraday Avenue Carlsbad, California 92008 PREPARED BY Ninyo & Moore Geotechnical and Environmental Sciences Consultants 5710 Ruffin Road San Diego, California 92123 February 25, 2008 Project No. 106270001 5710 Ruffin Road • San Diego. California 92123 • Phone (858) 576-1000 • Fax (858) 576-9600 San Diego • Irvine • Ontario • Los Angeles • Oak/and • Las Vegas • Carson City • Phoen1x • Denver ~Min9o& Moo~e 'iiiiiiliiliiiiiiiiiii -I ,-I ' ~eotechn1cal and Environmental Sciences Consultants Ms. Sherri Howard, P. E. Associate Engineer City of Carlsbad 1635 Faraday Avenue Carlsbad, California 92008 Subject: Geotechnical Evaluation La Costa Avenue Slope Failure Carlsbad, California Dear Ms. Howard: February 25, 2008 Project No. 106270001 In accordance with your authorization, we have performed a geotechnical evaluation for the slope failure on the south side of La Costa Avenue in Carlsbad, California. This report presents our geo- technical findings, conclusions, and recommendations regarding the mitigation of the slope failure. We appreciate the opportunity to be of service on this project. Sincerely, NINYO & MOORE t24~ Andres Bernal, G.E. Senior Project Engineer ABS/FOM/JG/kh Distribution: (5) Addressee 5710 Ruffin Road • San Diego. California 92123 • Phone (858) 576-1000 • Fax (858) 576-9600 San Diego • Irvine • Ontario • Los Angeles • Oakland • Las Vegas • Carson City • Phoenix • Denver La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 TABLE OF CONTENTS Page 1. INTRODUCTION .................................................................................................................... 1 2. SCOPE OF SERVICES ............................................................................................................ 1 3. SITE AND PROJECT DESCRIPTION ................................................................................... .2 4. SUBSURFACE EXPLORATION AND LABORATORY TESTING .................................... 2 5. GEOLOGY AND SUBSURFACE CONDITIONS ................................................................. 2 5 .1. Site Geology ................................................................................................................. 3 5 .1.1. Landslide Debris ................................................................................................. 3 5.1.2. Santiago Formation ............................................................................................. 3 5.2. Rippability .................................................................................................................... 3 5.3. Groundwater ................................................................................................................. 3 6. CONCLUSIONS ...................................................................................................................... 4 7. RECOMMENDATIONS .......................................................................................................... 4 7.1. Earthwork ..................................................................................................................... 4 7 .1.1. Site Preparation ................................................................................................... 4 7.1.2. Treatment of Existing Landslide Debris ............................................................. 5 7.1.3. Excavation Characteristics .................................................................................. 5 7 .1.4. Materials for Fill ................................................................................................. 5 7.1.5. Compacted Fill .................................................................................................... 6 7.1.6. Temporary Excavations ....................................................................................... ? 7.1.7. Slopes .................................................................................................................. ? 7 .1.8. Drainage .............................................................................................................. 8 7.2. Pre-Construction Meeting ............................................................................................. 8 7.3. Plan Review and Construction Observation ................................................................. 9 8. LIMITATIONS ......................................................................................................................... 9 9. SELECTED REFERENCES .................................................................................................. 11 Figures Figure I -Site Location Map Figure 2 -Test Pit Location Map Appendices Appendix A-Test Pit Log Appendix B -Laboratory Testing Appendix C -Typical Earthwork Guidelines 106270001 Rdoc La Costa Avenue Slope Failure Carlsbad, California 1. INTRODUCTION February 25, 2008 Project No. 106270001 In accordance with your request and our proposal dated November 30, 2007, we have performed a geo- technical evaluation for the repair of an approximately 50-foot-wide by 12-foot-high slope failure on the south side of La Costa Avenue between Gibraltar and Romeria Streets in Carlsbad, California (Figures 1 and 2). Our work was requested as a response to an evaluation of the larger slope (of which the failure is a small portion) by another consultant (see References). lbis report presents our conclusions regarding the geotechnical conditions at the subject site and our recommendations for the mitigation of the failure. 2. SCOPE OF SERVICES Ninyo & Moore's scope of services for this project included review of pertinent background data, previous geotechnical reports, performance of a subsurface evaluation, and engineering analysis with regard to the repair of the subject slope. Specifically, we performed the following tasks: • Reviewing readily available published geotechnical literature, including geologic maps, geo- technical reports, engineering plans, and aerial photographs. • Performing a field reconnaissance to observe site conditions and to mark the location of our subsurface exploration. • Contacting Underground Service Alert (USA) to clear the proposed subsurface exploration location for conflicts with buried utilities. • Obtaining City of Carlsbad Right-of-Way permits. • Coordinating with City of Carlsbad inspectors. • Performing subsurface exploration consisting of the digging, logging and sampling of an exploratory test pit. Bulk soil samples were obtained at selected intervals from the test pit. Addi- tional soil samples were obtained by hand from areas of the slope adjoining the slope failure area. • Performing geotechnical laboratory testing on selected samples. • Compiling and analyzing the data obtained. • Preparing this report presenting our geotechnical findings, conclusions, and recommenda- tions regarding the geotechnical design and construction of the subject slope failure. Evaluating the global stability of the overall slope was beyond the scope of this report. 106270001 R.doc La CostaAvenue Slope Failure Carlsbad, California 3. SITE AND PROJECT DESCRIPTION February 25, 2008 Project No. 106270001 As noted, the proposed project involves the repair of a slope failure which occurred on the south side of La Costa Avenue in Carlsbad, California. This area of Carlsbad is predominantly residential. The failed area is located approximately 750 feet west of Romeria Street at the base of a north- facing cut slope. The slope failure is approximately 50 feet wide at the toe of the slope and extends approximately 12 feet up-slope. The elevation ofthe project site varies from approximately 142 feet above mean sea level (MSL) at the toe of the failure to approximately 154 feet above MSL at the top of the head scarp. As discussed, the slope failure is within a larger cut slope extending up ap- proximately 30 feet at the slope failure location. Above the cut slope, a natural slope extends an additional 50 feet to the rear of homes above. The slopes are heavily vegetated with a moderate to dense growth of weeds and brush. 4. SUBSURFACE EXPLORATION AND LABORATORY TESTING Our subsurface exploration was conducted on January 16, 2008 and consisted of excavating a sin- gle exploratory test pit (TP-1) using a John Deere 310 backhoe. Bulk soil samples, designated S-1 through S-3, were obtained at selected intervals from the test pit. Additional soil samples, desig- nated S-4 through S-6, were obtained from hand excavated borings in the area around the slope failure. The approximate locations of the test pit and hand sampling are shown on Figure 2. The test pit log is presented in Appendix A. Laboratory testing of representative soil samples included moisture content, in-situ moisture con- tent, grain size analysis, percent passing the No. 200 sieve, and Atterberg limits. The results of the laboratory tests performed are presented in Appendix B. 5. GEOLOGY AND SUBSURFACE CONDITIONS Our fmdings regarding site geology and groundwater conditions are provided in the following sections. 106270001 R.doc 2 - - .... ..... La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 5.1. Site Geology The geologic units encountered during our subsurface evaluation included landslide debris and ma- terials of the Santiago Formation. Generalized descriptions of the units encountered are provided in the subsequent sections. Detailed descriptions are also provided on the test pit log in Appendix A 5.1.1. Landslide Debris Landslide debris was encountered in the test pit from the ground surface to depths of up to approximately 6 feet. The landslide debris is derived from the underlying Santiago Forma- tion. As encountered, the landslide debris generally consisted of light brown, saturated, loose, clayey silt and clayey sand . 5.1.2. Santiago Formation Materials of the Santiago Formation were encountered in the test pit underlying the land- slide debris to the depth explored. The Santiago Formation was also encountered in our shallow sample locations around the slope failure. As encountered, the materials generally consisted of a light brown to light grayish brown, moist to wet, weakly cemented, clayey fine-to medium-grained sandstone. 5.2. Rippability Based on our site reconnaissance and subsurface exploration, the on-site landslide debris and materials of the Santiago Formation are expected to be rippable with normal heavy-duty earthmoving equipment. 5.3. Groundwater Groundwater seepage was noted in our test pit as well as at various other locations above, and to the west of the subject slope failure. This seepage was observed during our site visit in November 2007, and occurred during a dry period of approximately nine months without rainfall. Fluctuations in groundwater level may occur due to seasonal variations, irrigation, groundwater withdrawal or in- jection, and other factors. I 0627000 I R doc 3 La Costa Avenue Slope Failure Carlsbad, California 6. CONCLUSIONS February 25, 2008 Project No. 106270001 Based on our review of the referenced background data, geologic field reconnaissance, subsurface evaluation and laboratory testing, it is our opinion that the proposed slope failure repair is feasible from a geotechnical standpoint. Geotechnical considerations include the following: • The landslide debris at the site is in a saturated condition and unsuitable for use as fill in its current condition. Due to site constraints and the lack of an area to spread and dry the landslide debris, it is anticipated that the material will be removed from the site and replaced with imported fill. • Groundwater seepage is expected to be a constraint during construction. • • Backdrains for the landslide repair are recommended to mitigate groundwater seepage . .... - - 7. RECOMMENDATIONS The following recommendations are provided for use in design and construction of the proposed landslide repair. If additional geotechnical recommendations are needed, please contact this office. 7 .1. Earthwork In general, earthwork should be performed in accordance with the recommendations pre- sented in this report. In addition, Typical Earthwork Guidelines for the project are included as Appendix C. In the event of a conflict, the recommendations presented in the text of this re- port should supersede those in Appendix C. 106270001 R.doc 7.1.1. Site Preparation Site preparation should begin with the removal of vegetation and other deleterious de- bris from areas to be graded. Tree stumps and roots should be removed to such a depth that organic material is generally not present. Clearing and grubbing should extend to the outside of the proposed excavation and fill areas. The debris and unsuitable material generated during clearing and grubbing should be removed from areas to be graded and disposed of at a legal dumpsite away from the project area. 4 - - - La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 106270001 R.doc 7.1.2. Treatment of Existing Landslide Debris We recommend that landslide debris material be removed from the slope failure area. Due to the saturated condition of the landslide debris, we anticipate that this material will not be re- usable in its present condition and imported fill material will be needed to rebuild the slope. Due to seepage at the site, we also recommend that a back drain be incorporated into the landslide repair plans. The back drain should consist of open graded gravel enclosed in filter fabric placed against the back of the remedial excavation. A 4-inch perforated pipe should be placed at the bottom of the gravel drain and tight lined to a free outlet with a fall of 2 percent or more. Alternatively, a composite drain such as Miradrain 2000 or equivalent may be used in place of the gravel drain. The bottom and slope face of the remedial excavation should be evaluated by Ninyo & Moore's representative at the time of construction. 7.1.3. Excavation Characteristics The results of our geotechnical evaluation indicate that the project site, as presently pro- posed, is underlain by landslide debris and materials of the Santiago Formation. The on-site materials are expected to be generally rippable with normal heavy-duty earthmoving equip- ment. Strongly cemented material (concretions), however, may be encountered within the Santiago Formation which would entail heavy ripping or the use of rock breakers. 7.1.4. Materials for Fill On-site soils with an organic content of less than approximately 3 percent by volume (or 1 percent by weight) are suitable for use as fill. The on-site landslide debris, however, is likely to be too wet to use as fill without drying. In general, fill materials should not contain rocks or lumps over approximately 4 inches, and should not have more than ap- proximately 40 percent of the particles greater than % inch. Larger chunks, if generated during excavation, may be broken into acceptably sized pieces or disposed of offsite. Imported fill material, if needed for the project, should generally be granular soils with a low or very low expansion potential (i.e. Expansion Index, EI, lower than 50). Import 5 - - La CostaAvenue Slope Failure Carlsbad, California February 25, 2008 Project No. I 0627000 I I 0627000 I R doc material should also have generally low corrosion potential. Materials for use as fill should be evaluated by Ninyo & Moore's representative prior to filling or importing. 7.1.5. Compacted Fill The contractor should request an evaluation of the exposed ground surface by Ninyo & Moore prior to placement of compacted fill. Unless otherwise recommended, the ex- posed ground surface should be scarified to a depth of approximately 8 inches and watered or dried, as needed, to achieve a moisture content generally above the optimum moisture content. The scarified materials should then be compacted to a relative com- paction of 90 percent as evaluated by the American Society for Testing and Materials (ASTM) Test Method D1557. The evaluation of compaction by the geotechni- cal consultant should not be considered to preclude any requirements for observation or approval by governing agencies. It is the contractor's responsibility to notify our offices and the appropriate governing agency when project areas are ready for observation, and to provide reasonable time for that review. Fill materials should be moisture conditioned to generally above the laboratory optimum moisture content prior to placement. The optimum moisture content will vary with ma- terial type and other factors. Moisture conditioning of fill soils should be generally consistent within the soil mass. Prior to placement of additional compacted fill material following a delay in the grading operations, the exposed surface of previously compacted fill should be prepared to receive fill. Preparation may include scarification, moisture conditioning, and recompaction. Compacted fill should be placed in horizontal lifts of approximately 8 inches in loose thickness. Prior to compaction, each lift should be watered or dried as needed to achieve a moisture content generally above the laboratory optimum, mixed, and then compacted by mechanical methods, using sheepsfoot rollers, multiple-wheel pneumatic-tired rollers or other appropriate compacting rollers, to a relative compaction of 90 percent as evalu- 6 - - - La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 106270001 R.doc ated by ASTM D1557. Successive lifts should be treated in a like manner until the de- sired finished grades are achieved. 7.1.6. Temporary Excavations Although not anticipated, we recommend that trenches and excavations be designed and constructed in accordance with Occupational Safety & Health Administration (OSHA) regu- lations. These regulations provide trench sloping and shoring design parameters for trenches up to about 20 feet deep based on the soil types encountered. Trenches over 20 feet deep should be designed by the Contractor's engineer based on site-specific geotechnical analyses. For planning purposes, we recommend that the following OSHA soil classifications be used: Fill Santiago Formation TypeC TypeB Upon making the excavations, the soil classifications and excavation performance should be checked in the field by Ninyo & Moore's representative in accordance with the OSHA regulations. Temporary excavations should be constructed in accordance with OSHA recommenda- tions. For trench or other excavations, OSHA requirements regarding personnel safety should be met by using appropriate shoring (including trench boxes) or by laying back the slopes at inclinations no steeper than 1.5:1 (horizontal:vertical) in fill materials and 1:1 in materials of the Santiago Formation. Temporary excavations that encounter seepage may need shoring or may be stabilized by placing sandbags or gravel along the base of the seepage zone. Excavations encountering seepage should be evaluated on a case-by-case basis. On-site safety of personnel is the responsibility of the contractor. 7.1.7. Slopes We recommend that fill and cut slopes be constructed at an inclination of 2:1 (horizon- tal:vertical) to match the existing slope inclination. Compaction of the face of fill slopes should be performed by backrolling at intervals of 4 feet or less in vertical slope height or as 7 - .... La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. I 06270001 dictated by the capability of the available equipment, whichever is less. Fill slopes should be backrolled utilizing a sheepsfoot-type roller. Care should be taken in maintaining the desired moisture conditions and/or reestablishing them, as needed, prior to backrolling. The place- ment, moisture conditioning, and compaction of fill slope materials should be done in accordance with the recommendations presented in the Compacted Fill section of this report. Site runoff should not be permitted to flow over the tops of slopes. Positive drainage should be established away from the slopes. This may be accomplished by incorporating brow ditches placed at the top of the slopes to divert surface runoff away from the slope face where drainage devices are not otherwise available. The on-site soils are to be susceptible to erosion; therefore, the project plans and speci- fications should contain design features and construction requirements to mitigate erosion of on-site soils during and after construction. Slopes and other exposed ground surfaces should be appropriately planted with a protective ground cover. 7.1.8. Drainage Surface drainage on the site should generally be provided so that water is not permitted to pond. A gradient of 2 percent or steeper should be maintained and drainage patterns should be established to divert and remove water from the site to appropriate outlets. Care should be taken by the contractor during grading to preserve any berms, drainage terraces, interceptor swales or other drainage devices on or adjacent to the project site. Drainage patterns established at the time of grading should be maintained for the life of the project. The property maintenance personnel should be made aware that altering drainage patterns might be detrimental to long term stability of slopes. 7.2. Pre-Construction Meeting We recommend that a pre-construction meeting be held prior to the commencement of grad- ing. The owner or his representative, the agency representatives, the architect, the civil !06270001 R doc 8 --- -- - La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 engineer, Ninyo & Moore, and the contractor should be in attendance to discuss the plans, the project, and the proposed construction schedule. 7.3. Plan Review and Construction Observation The recommendations presented in this report are based on our understanding of the project and subsurface information disclosed by one exploratory test pit. Ninyo & Moore should check the subsurface conditions during construction. A representative of Ninyo & Moore should verifY the depth and extent of removals during construction. Observation and testing of compacted fill and backfill should be performed by Ninyo & Moore. We further recommend that project plans be re- viewed by the design engineer and Ninyo & Moore before construction. It should be noted that upon review of the project plans and specifications, some recommendations presented in this re- port might be revised or modified to meet the project requirements. 8. LIMITATIONS The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care exercised by geotechnical consultants performing similar tasks in the project area. No warranty, expressed or im- plied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncer- tainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials. This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. I 0627000 I R doc 9 ,..,. -- La Costa Avenue Slope Failure Carlsbad, California February 25, 2008 Project No. 106270001 This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant per- form an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing. Our conclusions, recommendations, and opinions are based on an analysis of the observed site con- ditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified, and additional recommendations, if warranted, will be provided upon re- quest. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government ac- tion or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control. This report is intended exclusively for use by the client. Any use or reuse of the findings, conclu- sions, and/or recommendations of this report by parties other than the client is undertaken at said parties' sole risk. 106270001 R,doc 10 .... "'"' - ---- La Costa Avenue Slope Failure Carlsbad, California 9. SELECTED REFERENCES February 25, 2008 Project No. 106270001 Benton Engineering, Inc., 1970, Final Report on Compacted Filled Ground, Lots 497 to 513, In- clusive, Lots 516 and 517, Lots 523 to 551, Inclusive, Lots 556 to 592, Inclusive, 596, 597, 601, 604, 605, and 613, Lots 622 to 658, Inclusive, and Report on Expansive Soils, La Costa South Unit No.7, San Diego, California: dated August 10. Benton Engineering, Inc., 1974, Final Report on Compacted Filled Ground, La Costa Vale Unit No. 1, Carlsbad, California: dated February 28. Bureau Veritas/Testing Engineers San Diego, 2007, Preliminary Reconnaissance of Existing Slope Area, La Costa Avenue, Between Gibraltar Street and Romeria Street, Carlsbad, California: dated November 5. California Building Standards Commission (CBSC), 2007, California Building Code (CBC), Ti- tle 24, Part 2, Volumes 1 and 2. County of San Diego, 1960, Topographic Survey, Sheet 334-1689, Scale 1" = 200'. County of San Diego, 1975, Topographic Survey (Orthotopographic), Sheet 334-1689, Scale 1" = 200'. International Code Council, Inc. (I CCI), 2006, International Building Code (IBC). Kennedy, Michael P. and Tan, Siang S., 2005, Geologic Map of the Oceanside 30' X 60' Quadran- gle, California: Regional Geologic Map Series, Map No. 2. United States Geological Survey, 1968 (photo-revised 1983), Rancho Santa Fe Quadrangle, Cali- fornia, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000. AERIAL PHOTOGRAPHS Source Date Fli~ht Numbers Scale USDA I 4-11-53 I AXN-8M I 17 and 18 I 1:20,000 106270001 R doc II - - - ... ----• -- 0 2400 4800 APPROXIMATE SCALE IN FEET PROJECT NO. DATE 106270001 2/08 SITE LOCATION MAP LA COSTA AVENUE SLOPE FAILURE CARLSBAD, CALIFORNIA FIGURE 1 -- APPROXIMATE LOCATION OF TP-1 EXPLORATORY TEST PIT e APPROXIMATE LOCATION OF S-6,S-6A SOIL SAMPLE 0 - -APPROXIMATE LIMIT OF SLOPE FAILURE AREA APPROXIMATE SCALE 40 80 FEET - NOTE· ALl DIMENSIONS. DIRECTIONS AND LOCATIONS ARE APPROXIMATE. PROJECT NO. DATE 106270001 2/08 ----- TEST PIT LOCATION MAP LA COSTA AVENUE SLOPE FAILURE CARLSBAD, CALIFORNIA REFERENCE; MICROSOFT VIRTUAl EARTH. 20011 FIGURE 2 La Costa Avenue Slope Failure Carlsbad, California APPENDIX A TEST PIT LOG Field Procedure for the Collection of Disturbed Samples February 25, 2008 Project No. 106270001 Disturbed soil samples were obtained in the field using the following method. Bulk Samples Bulk samples of representative earth materials were obtained from the exploratory test pit. The samples were bagged and transported to the laboratory for testing. I 0627000 I R doc "T1 Gi c ::0 m ~ ·~·fl(---= 'I· ,..••• .:: ftil'-•. -- Explanation of Test Pit, Core, Trench and Hand Auger Log Symbols PROJECT NO. DATE SCALE: 1 inch 1 foot =r== ~ w UJ !:!:-::r: f-a. w CJ 0 I 2 3 4 5 --= (/) UJ ...J a. :::: ~ <{ e... w (/) a::: ::::l ~td 1-(/) 0 ::E ---- -1 ~ -'¥ IX T xx!xx \ =r= =~ -- lL z () e:, 0 i= ~ <l::rfi EXCAVATION LOG () . U5 -U L1.. . EXPLANATION SHEET z -(/) w (/) . U)::::l CJ ::5 >-a::: () CJ SM f.I11: Bulk sample. ----f-----1----------------------------------------· ML Dashed line denotes material change. Drive sample. Sand cone performed. Seepage Groundwater encountered during excavation. No recovery with drive sampler. Groundwater encountered after excavation. Sample retained by others. Shelby tube sample. Distance pushed in inches/length of sample recovered in inches No '"w ""'· with Shelby tube sampler. SM AUJJVIUM Solid line denotes unit change. Attitude: Strike/Dip b: Bedding c: Contact j: Joint f: Fracture F: Fault cs: Clay Seam s: Shear bss: Basal Slide Surface sf: Shear Fracture sz: Shear Zone sbs: Sheared RPrlrlino Surface The total depth line is a solid line that is drawn at the bottom of the Jog. T estplt explanat1on.xls ---1(1n9D&cJV'DDre (/) LU -__J lL a.. -() I=' ~ ~ a.. LU <( ~ --TEST PIT LOG LU (/) LU >-lL a::: f---:::::> U5 f-z LA COST A A VENUE SLOPE F AlLURE (/) LU CARLSBAD, CALIFORNIA 0 0 ~ >-a::: 0 3 0 "---l---+---4 z 0 i= <(cr.) () . _() lL . _(J) (J)• (/):::::> <( __J () DATE EXCAVATED 1116/08 TEST PIT NO. TP-1 GROUND ELEVATION 142'± (MSL) LOGGED BY BTM METHOD OF EXCAVATION John Deere 310 Backhoe LOCATION Approximately 300' east of Gibraltar Street DESCRIPTION LANDSLIDE DEPOSIT (Qls): Light brown, moist to saturated, soft, clayey SILT; with sand; with clayey fine to medium SAND. moderately cemented, clayey, fine-to medium-grained Total Depth= 14 feet. Groundwater seepage encountered at approximately 4 feet. Backfilled on 1116/08. La Costa Avenue Slope Failure Carlsbad, California Classification APPENDIXB LABORATORY TESTING February 25, 2008 Project No. 106270001 Soils were visually and texturally classified in accordance with the Unified Soil Classification System (USCS) in general accordance with ASTM D 2488. Soil classifications are indicated on the log of the exploratory test pit in Appendix A. Moisture Content The moisture content of samples obtained from the exploratory excavations was evaluated in ac- cordance with ASTM D 2216. The test results are presented on the logs of the exploratory excavations in Appendix A. In-Place Moisture and Density Tests The moisture content and dry density of bulk and relatively undisturbed samples obtained from the exploratory excavation was evaluated in general accordance with ASTM D 293 7. The test results are presented on the log of the exploratory excavation and in Figure B-1. Gradation Analysis A gradation analysis test was performed on a selected representative soil sample in general ac- cordance with ASTM D 422. The grain-size distribution curve is shown on Figure B-2. These test results were utilized in evaluating the soil classifications in accordance with the uses. 200 Wash An evaluation of the percentage of minus-200 sieve material in a selected soil sample was performed in general accordance withASTM D 1140. The results ofthe test are presented on Figure B-3. Atterberg Limits A test was performed on a selected representative fine-grained soil sample to evaluate the liquid limit, plastic limit, and plasticity index in general accordance with ASTM D 4318. These test re- sults were utilized to evaluate the soil classification in accordance with the USCS. The test results and classification are shown on Figure B-4. I 0627000 I R doc SAMPLE MOISTURE DRY SAMPLE DEPTH DESCRIPTION CONTENT DENSITY LOCATION (FT) (%) (PCF) TP-1 (S-2) 3.0-4.0 Clayey SAND 13.7 -- S-4 0.0-1.0 Clayey SILT 35.8 -- S-6 0.5-1.0 Clayey SILT 23.9 - S-6A 1.0-2.0 Clayey SAND 18.0 99.7 PERFORMED IN GENERAL ACCORDANCE WITH ASTM 0 2937-04 PROJECT NO. 106270001 106270001 Moden xts DATE 2/08 IN-PLACE MOISTURE AND DENSITY TESTS LA COSTA AVENUE SLOPE FAILURE CARLSBAD, CALIFORNIA FIGURE B-1 I GRAVEL I SAND FINES I I Coarse Fine I Coarse Medium I Fine SILT CLAY I U.S. STANDARD SIEVE NUMBERS HYDROMETER 3" 2' HI" 1" ~ .. "'.!":X." 4 8 16 30 50 100 200 100.0 I I I I I I I I I h 1\ I I 90.0 I I I I I I I I I I I I I I 1\ I 80.0 I I I I i\ I I I I I I I I I I I-70.0 I I I I I I C) w I I I I I I I I I I ~ 60 0 I I I I I >-ID I I I I I I I I I I I 0:: 50.0 w I I I I I z u: I I I I I I I I I I I I-40.0 I I I I I z w I I I I I I I I I I I u 0:: 30.0 I I I I I w a. 20.0 I I I I I I I I I I I I I I I I I I I I I I 10.0 I I I I I I I I I I I I I I I I I I I I I I 0.0 I I I I I 100 10 1 01 0.01 0.001 0 0001 GRAIN SIZE IN MILLIMETERS Sample Depth Liquid Plastic Plasticity Passing Symbol Location (II) Limit Limit Index D1o D30 D6o Cu Cc No. 200 uses (%) I t'-1 • (Sample 1.0-2.0 ------- --------66 MH 1\ PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 422-63 (02) lfiD90&/(tOO~e GRADATION TEST RESULTS FIGURE PROJECT NO. DATE 8-2 LA COSTA AVENUE SLOPE FAILURE 106270001 2/08 CARLSBAD, CALIFORNIA 106270001 SIEVE TP-1 @ 1 0-2 0 x~ SAMPLE PERCENT PERCENT uses SAMPLE DEPTH DESCRIPTION PASSING PASSING (TOTAL LOCATION (FT) N0.4 NO. 200 SAMPLE) TP-1 1.0-1.5 Clayey SAND 100 45 ML (Sample 5) PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 1140-00 JYIR90&~00Y'e NO. 200 SIEVE ANALYSIS FIGURE PROJECT NO. DATE LA COSTA AVENUE SLOPE FAILURE B-3 106270001 2/08 CARLSBAD, CALIFORNIA 106270001·200 WASH TP·1@ 1 0-1.5 xis uses SYMBOL LOCATION DEPTH LIQUID PLASTIC PLASTICITY CLASSIFICATION uses (FT) LIMIT, LL LIMIT, PL INDEX, PI (Fraction Finer Than (Entire Sample) No. 40 Sieve) • TP-1 (Sample 3) 0.0-1.0 51 30 21 MH MH NP-INDICATES NON-PLASTIC 60 v / 50 v / a: CH or OH >< 40 / w v v 0 / z ~ 30 (} ~o,Ol v i= en ./ <( 20 MH orOH ...I v / a. / 10 / / / CL-ML / ML or OL 0 / I 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT, LL PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 4318-05 ATTERBERG LIMITS TEST RESULTS FIGURE PROJECT NO. 106270001 106270001 ATIERBERG Page*1.xls DATE 2/08 LA COSTA AVENUE SLOPE FAILURE CARLSBAD, CALIFORNIA 8-4 La Costa Avenue Slope Failure Carlsbad, California APPENDIXC TYPICAL EARTHWORK GUIDELINES 106270001 TEG.doc Appendix C Project No. 106270001 La Costa Avenue Slope Failure Carlsbad, California TABLE OF CONTENTS Appendix C Project No. 106270001 Page 1. GENERAL ................................................................................................................................ ! 2. OBLIGATIONS OF PARTIES ................................................................................................ 2 3. SITE PREPARATION ............................................................................................................. 3 4. REMOVALS AND EXCAVATIONS .................................................................................... .4 5. COMPACTED FILL ................................................................................................................ 5 6. OVERSIZED MATERIAL ...................................................................................................... 7 7. SLOPES .................................................................................................................................... 8 8. TRENCH BACKFILL ............................................................................................................ 11 9. DRAINAGE ........................................................................................................................... 13 10. SITE PROTECTION .............................................................................................................. 14 11. DEFINITIONS OF TERMS ................................................................................................... 16 Figures Figure A -Fill Slope Over Natural Ground or Cut Figure B -Transition and Undercut Lot Details Figure C -Canyon Subdrain Detail Figure D -Oversized Rock Placement Detail Figure E -Slope Drainage Detail Figure F -Shear Key Detail Figure G -Drain Detail 106270001 TEG doc Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 TYPICAL EARTHWORK GUIDELINES 1. GENERAL These guidelines and the standard details attached hereto are presented as general procedures for earthwork construction. They are to be utilized in conjunction with the project grading plans. These guidelines are considered a part of the geotechnical report, but are superseded by recom- mendations 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 super- sede these specifications and/or the recommendations of the geotechnical report. It is the responsibility of the contractor to read and understand these guidelines as well as the geotechni- cal report and project grading plans. 1.1. The contractor shall not vary from these guidelines without prior recommendations by the geotechnical consultant and the approval of the client or the client's author- ized representative. Recommendations by the geotechnical consultant and/or client shall not be considered to preclude requirements for approval by the jurisdictional agency prior to the execution of any changes. 1.2. The contractor shall perform the grading operations in accordance with these speci- fications, and shall be responsible for the quality of the finished product notwithstanding the fact that grading work will be observed and tested by the geo- technical consultant. 1.3. It is the responsibility of the grading contractor to notify the geotechnical consult- ant and the jurisdictional agencies, as needed, prior to the start of work at the site and at any time that grading resumes after interruption. Each step of the grading operations shall be observed and documented by the geotechnical consultant and, where necessary, reviewed by the appropriate jurisdictional agency prior to pro- ceeding with subsequent work. 1.4. If, during the grading operations, geotechnical conditions are encountered which were not anticipated or described in the geotechnical report, the geotechnical con- sultant shall be notified immediately and additional recommendations, if applicable, may be provided. 1.5. An as-graded report shall be prepared by the geotechnical consultant and signed by a registered engineer and registered engineering geologist. The report documents the geotechnical consultants' observations, and field and laboratory test results, and 106270001 TEG doc Rev. 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 provides conclusions regarding whether or not earthwork construction was per- formed in accordance with the geotechnical recommendations and the grading plans. Recommendations for foundation design, pavement design, subgrade treat- ment, etc., may also be included in the as-graded report. 1.6. For the purpose of evaluating quantities of materials excavated during grading and/or locating the limits of excavations, a licensed land surveyor or civil engineer shall be retained. 1.7. Definitions of terms utilized in the remainder of these specifications have been provided in Section 11. 2. OBLIGATIONS OF PARTIES The parties involved in the projects earthwork activities shall be responsible as outlined in the following sections. 2.1. The client is ultimately responsible for the aspects of the project. The client or the client's authorized representative has a responsibility to review the findings and recommendations of the geotechnical consultant. The client shall authorize the con- tractor and/or other consultants to perform work and/or provide services. During grading the client or the client's authorized representative shall remain on site or remain reasonably accessible to the concerned parties to make the decisions that may be needed to maintain the flow of the project. 2.2. The contractor is responsible for the safety of the project and satisfactory comple- tion of grading and other associated operations, including, but not limited to, earthwork in accordance with the project plans, specifications, and jurisdictional agency requirements. During grading, the contractor or the contractor's authorized representative shall remain on site. The contractor shall further remain accessible during non-working hours times, including at night and during days off. 2.3. The geotechnical consultant shall provide observation and testing services and shall make evaluations to advise the client on geotechnical matters. The geotechnical consultant shall report findings and recommendations to the client or the client's authorized representative. 2.4. Prior to proceeding with any grading operations, the geotechnical consultant shall be notified two working days in advance to schedule the needed observation and testing services. 10627000 I TEG doc 2 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 2.4.1. Prior to any significant expansion or reduction in the grading operation, the geotechnical consultant shall be provided with two working days notice to make appropriate adjustments in scheduling of on-site personnel. 2.4.2. Between phases of grading operations, the geotechnical consultant shall be provided with two working days notice in advance of commencement of ad- ditional grading operations. 3. SITE PREPARATION Site preparation shall be performed in accordance with the recommendations presented in the following sections. 3 .1. The client, prior to any site preparation or grading, shall arrange and attend a pre-grading meeting between the grading contractor, the design engineer, the geo- technical consultant, and representatives of appropriate governing authorities, as well as any other involved parties. The parties shall be given two working days no- tice. 3.2. Clearing and grubbing shall consist ofthe substantial removal ofvegetation, brush, grass, wood, stumps, trees, tree roots greater than 1/2-inch in diameter, and other deleterious materials from the areas to be graded. Clearing and grubbing shall ex- tend to the outside of the proposed excavation and fill areas. 3.3. Demolition in the areas to be graded shall include removal ofbuilding structures, foun- dations, reservoirs, utilities (including underground pipelines, septic tanks, leach fields, seepage pits, cisterns, etc.), and other manmade surface and subsurface improvements, and the backfilling of mining shafts, tunnels and surface depressions. Demolition of utilities shall include capping or rerouting of pipelines at the project perimeter, and abandonment of wells in accordance with the requirements of the governing authorities and the recommendations ofthe geotechnical consultant at the time of demolition. 3.4. The debris generated during clearing, grubbing and/or demolition operations shall be removed from areas to be graded and disposed of off site at a legal dump site. Clearing, grubbing, and demolition operations shall be performed under the obser- vation ofthe geotechnical consultant. 3.5. The ground surface beneath proposed fill areas shall be stripped of loose or unsuit- able soil. These soils may be used as compacted fill provided they are generally free of organic or other deleterious materials and evaluated for use by the geotech- nical consultant. The resulting surface shall be evaluated by the geotechnical consultant prior to proceeding. The cleared, natural ground surface shall be scari- I 0627000 I TEG doc 3 Rev. 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 fied to a depth of approximately 8 inches, moisture conditioned, and compacted in accordance with the specifications presented in Section 5 of these guidelines. 3.6. Where fills are to be constructed on hillsides or slopes, topsoil, slope wash, collu- vium, and other materials deemed unsuitable shall be removed. Where the exposed slope is steeper than 5 horizontal units to 1 vertical unit, or where recommended by the geotechnical consultant, the slope of the original ground on which the fill is to be placed shall be benched and a key as shown on Figure A of this document shall be provided by the contractor in accordance with the specifications presented in Section 7 of this document. The benches shall extend into the underlying bedrock or, where bedrock is not present, into suitable compacted fill as evaluated by the geotechnical consultant. 4. REMOVALS AND EXCAVATIONS Removals and excavations shall be performed as recommended in the following sections. 4.1. Removals 4.1.1. Materials which are considered unsuitable shall be excavated under the ob- servation of the geotechnical consultant in accordance with the recommendations contained herein. Unsuitable materials include, but may not be limited to, dry, loose, soft, wet, organic, compressible natural soils, frac- tured, weathered, soft bedrock, and undocumented or otherwise deleterious fill materials. 4.1.2. Materials deemed by the geotechnical consultant to be unsatisfactory due to moisture conditions shall be excavated in accordance with the recommenda- tions of the geotechnical consultant, watered or dried as needed, and mixed to a generally uniform moisture content in accordance with the specifications presented in Section 5 of this document. 4.2. Excavations I 0627000 I TEG doc 4.2.1. Temporary excavations no deeper than 5 feet in firm fill or natural materials may be made with vertical side slopes. To satisfy CAL OSHA requirements, any excavation deeper than 5 feet shall be shored or laid back at a 1: 1 (hori- zontal:vertical) inclination or flatter, depending on material type, if construction workers are to enter the excavation. 4 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California 5. COMPACTED FILL Appendix C Project No. 106270001 Fill shall be constructed as specified below or by other methods recommended by the geotechni- cal consultant. Unless otherwise specified, fill soils shall be compacted to 90 percent relative compaction, as evaluated in accordance with ASTM Test Method D 1557. 5.1. Prior to placement of compacted fill, the contractor shall request an evaluation of the exposed ground surface by the geotechnical consultant. Unless otherwise rec- ommended, the exposed ground surface shall then be scarified to a depth of approximately 8 inches and watered or dried, as needed, to achieve a generally uni- form moisture content at or near the optimum moisture content. The scarified materials shall then be compacted to 90 percent relative compaction. The evalua- tion of compaction by the geotechnical consultant shall not be considered to preclude any requirements for observation or approval by governing agencies. It is the contractor's responsibility to notify the geotechnical consultant and the appro- priate governing agency when project areas are ready for observation, and to provide reasonable time for that review. 5.2. Excavated on-site materials which are in general compliance with the recommenda- tions of the geotechnical consultant may be utilized as compacted fill provided they are generally free of organic or other deleterious materials and do not contain rock fragments greater than 6 inches in dimension. During grading, the contractor may encounter soil types other than those analyzed during the preliminary geotechnical study. The geotechnical consultant shall be consulted to evaluate the suitability of any such soils for use as compacted fill. 5.3. Where imported materials are to be used on site, the geotechnical consultant shall be notified three working days in advance of importation in order that it may sam- ple and test the materials from the proposed borrow sites. No imported materials shall be delivered for use on site without prior sampling, testing, and evaluation by the geotechnical consultant. 5.4. Soils imported for on-site use shall preferably have very low to low expansion po- tential (based on UBC Standard 18-2 test procedures). Lots on which expansive soils may be exposed at grade shall be undercut 3 feet or more and capped with very low to low expansion potential fill. Details of the undercutting are provided in the Transition and Undercut Lot Details, Figure B of these guidelines. In the event expansive soils are present near the ground surface, special design and construction considerations shall be utilized in general accordance with the recommendations of the geotechnical consultant. 5.5. Fill materials shall be moisture conditioned to near optimum moisture content prior to placement. The optimum moisture content will vary with material type and other 106270001 TEG doc 5 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 factors. Moisture conditioning of fill soils shall be generally uniform in the soil mass. 5.6. Prior to placement of additional compacted fill material following a delay in the grading operations, the exposed surface of previously compacted fill shall be pre- pared to receive fill. Preparation may include scarification, moisture conditioning, and recompaction. 5.7. Compacted fill shall be placed in horizontal lifts of approximately 8 inches in loose thickness. Prior to compaction, each lift shall be watered or dried as needed to achieve near optimum moisture condition, mixed, and then compacted by mechani- cal methods, using sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other appropriate compacting rollers, to the specified relative compaction. Succes- sive lifts shall be treated in a like manner until the desired finished grades are achieved. 5.8. Fill shall be tested in the field by the geotechnical consultant for evaluation of gen- eral compliance with the recommended relative compaction and moisture conditions. Field density testing shall conform to ASTM D 1556-00 (Sand Cone method), D 2937-00 (Drive-Cylinder method), and/or D 2922-96 and D 3017-96 (Nuclear Gauge method). Generally, one test shall be provided for approximately every 2 vertical feet of fill placed, or for approximately every 1,000 cubic yards of fill placed. In addition, on slope faces one or more tests shall be taken for approxi- mately every 10,000 square feet of slope face and/or approximately every 10 vertical feet of slope height. Actual test intervals may vary as field conditions dic- tate. Fill found to be out of conformance with the grading recommendations shall be removed, moisture conditioned, and compacted or otherwise handled to accom- plish general compliance with the grading recommendations. 5.9. The contractor shall assist the geotechnical consultant by excavating suitable test pits for removal evaluation and/or for testing of compacted fill. 5.1 0. At the request of the geotechnical consultant, the contractor shall "shut down" or restrict grading equipment from operating in the area being tested to provide ade- quate testing time and safety for the field technician. 5 .11. The geotechnical consultant shall maintain a map with the approximate locations of field density tests. Unless the client provides for surveying of the test locations, the locations shown by the geotechnical consultant will be estimated. The geotechnical consultant shall not be held responsible for the accuracy of the horizontal or verti- cal location or elevations. 5 .12. Grading operations shall be performed under the observation of the geotechnical consultant. Testing and evaluation by the geotechnical consultant does not preclude the need for approval by or other requirements of the jurisdictional agencies. 106270001 TEG doc 6 Rev. 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 5.13. Fill materials shall not be placed, spread or compacted during unfavorable weather conditions. When work is interrupted by heavy rains, the filling operation shall not be resumed until tests indicate that moisture content and density of the fill meet the project specifications. Regrading of the near-surface soil may be needed to achieve the specified moisture content and density. 5.14. Upon completion of grading and termination of observation by the geotechnical consultant, no further filling or excavating, including that planned for footings, foundations, retaining walls or other features, shall be performed without the in- volvement of the geotechnical consultant. 5.15. Fill placed in areas not previously viewed and evaluated by the geotechnical con- sultant may have to be removed and recompacted at the contractor's expense. The depth and extent of removal of the unobserved and undocumented fill will be de- cided based upon review ofthe field conditions by the geotechnical consultant. 5.16. Off-site fill shall be treated in the same manner as recommended in these specifica- tions for on-site fills. Off-site fill subdrains temporarily terminated (up gradient) shall be surveyed for future locating and connection. 5.17. Prior to placement of a canyon fill, a subdrain shall be installed in bedrock or com- pacted fill along the approximate alignment of the canyon bottom if recommended by the geotechnical consultant. Details of subdrain placement and configuration have been provided in the Canyon Subdrain Detail, Figure C, of these guidelines. 5 .18. Transition (cut/fill) lots shall generally be undercut 3 feet or more below finished grade to provide a generally uniform thickness of fill soil in the pad area. Where the depth of fill on a transition lot greatly exceeds 3 feet, overexcavation may be in- creased at the discretion of the geotechnical consultant. Details of the undercut for transition lots are provided in the Transition and Undercut Lot Detail, Figure B, of these guidelines. 6. OVERSIZED MATERIAL Oversized material shall be placed in accordance with the following recommendations. 6.1. During the course of grading operations, rocks or similar irreducible materials greater than 6 inches in dimension (oversized material) may be generated. These materials shall not be placed within the compacted fill unless placed in general ac- cordance with the recommendations of the geotechnical consultant. 6.2. Where oversized rock (greater than 6 inches in dimension) or similar irreducible material is generated during grading, it is recommended, where practical, to waste such material off site, or on site in areas designated as "nonstructural rock disposal I 0627000 I TEG doc 7 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 areas." Rock designated for disposal areas shall be placed with sufficient sandy soil to generally fill voids. The disposal area shall be capped with a 5-foot thickness of fill which is generally free of oversized material. 6.3. Rocks 6 inches in dimension and smaller may be utilized within the compacted fill, provided they are placed in such a manner that nesting of rock is not permitted. Fill shall be placed and compacted over and around the rock. The amount of rock greater than 3/4-inch in dimension shall generally not exceed 40 percent of the total dry weight of the fill mass, unless the fill is specially designed and constructed as a "rock fill." 6.4. Rocks or similar irreducible materials greater than 6 inches but less than 4 feet in dimension generated during grading may be placed in windrows and capped with finer materials in accordance with the recommendations of the geotechnical con- sultant, the approval of the governing agencies, and the Oversized Rock Placement Detail, FigureD, of these guidelines. Selected native or imported granular soil (Sand Equivalent of 30 or higher) shall be placed and flooded over and around the windrowed rock such that voids are filled. Windrows of oversized materials shall be staggered so that successive windrows of oversized materials are not in the same vertical plane. Rocks greater than 4 feet in dimension shall be broken down to 4 feet or smaller before placement, or they shall be disposed of off site. 7. SLOPES The following sections provide recommendations for cut and fill slopes. 7 .1. Cut Slopes 106270001 TEG doc 7 .1.1. Unless otherwise recommended by the geotechnical consultant and accepted by the building official, permanent cut slopes shall not be steeper than 2:1 (horizontal:vertical). The recommended height of a cut slope shall be evalu- ated by the geotechnical consultant. Slopes in excess of 30 feet high shall be provided with terrace drains (swales) in accordance with the recommenda- tions presented in the Uniform Building Code, Section 3315 and the details provided in Figure E of these guidelines. 7.1.2. The geotechnical consultant shall observe cut slopes during excavation. The geotechnical consultant shall be notified by the contractor prior to beginning slope excavations. 7.1.3. If excavations for cut slopes expose loose, cohesionless, significantly frac- tured, or otherwise unsuitable materials, overexcavation of the unsuitable material and replacement with a compacted stabilization fill shall be evalu- ated and may be recommended by the geotechnical consultant. Unless 8 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 otherwise specified by the geotechnical consultant, stabilization fill construc- tion shall be in general accordance with the details provided on Figure F of these guidelines. 7.1.4. If, during the course of grading, adverse or potentially adverse geotechnical conditions are encountered in the slope which were not anticipated in the pre- liminary evaluation report, the geotechnical consultant shall evaluate the conditions and provide appropriate recommendations. 7 .2. Fill Slopes I 0627000 I TEG.doc 7.2.1. When placing fill on slopes steeper than 5:1 (horizontal:vertical), topsoil, slope wash, colluvium, and other materials deemed unsuitable shall be re- moved. Near-horizontal keys and near-vertical benches shall be excavated into sound bedrock or firm fill material, in accordance with the recommenda- tion of the geotechnical consultant. Keying and benching shall be accomplished in general accordance with the details provided on Figure A of these guidelines. Compacted fill shall not be placed in an area subsequent to keying and benching until the area has been observed by the geotechnical consultant. Where the natural gradient of a slope is less than 5:1, benching is generally not recommended. However, fill shall not be placed on compressi- ble or otherwise unsuitable materials left on the slope face. 7.2.2. Within a single fill area where grading procedures dictate two or more sepa- rate fills, temporary slopes (false slopes) may be created. When placing fill adjacent to a temporary slope, benching shall be conducted in the manner de- scribed in Section 7.2.1. A 3-foot or higher near-vertical bench shall be excavated into the documented fill prior to placement of additional fill. 7.2.3. Unless otherwise recommended by the geotechnical consultant and by the building official, permanent fill slopes shall not be steeper than 2: I (horizon- tal:vertical). The height of a fill slope shall be evaluated by the geotechnical consultant. Slopes in excess of 30 feet high shall be provided with terrace drains (swales) and backdrains in accordance with the recommendations pre- sented in the Uniform Building Code, Section 3315 and the details provided in Figure E ofthese guidelines. 7.2.4. Unless specifically recommended otherwise, compacted fill slopes shall be overbuilt and cut back to grade, exposing firm compacted fill. The actual amount of overbuilding may vary as field conditions dictate. If the desired re- sults are not achieved, the existing slopes shall be overexcavated and reconstructed in accordance with the recommendations of the geotechnical consultant. The degree of overbuilding may be increased until the desired compacted slope face condition is achieved. Care shall be taken by the con- 9 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 tractor to provide mechanical compaction as close to the outer edge of the overbuilt slope surface as practical. 7.2.5. If access restrictions, property line location, or other constraints limit over- building and cutting back of the slope face, an alternative method for compaction of the slope face may be attempted by conventional construction procedures including backrolling at intervals of 4 feet or less in vertical slope height, or as dictated by the capability of the available equipment, whichever is less. Fill slopes shall be backrolled utilizing a conventional sheeps foot-type roller. Care shall be taken to maintain the specified moisture condi- tions and/or reestablish the same, as needed, prior to backrolling .. 7 .2.6. The placement, moisture conditioning and compaction of fill slope materials shall be done in accordance with the recommendations presented in Sec- tion 5. of these guidelines. 7.2.7. The contractor shall be ultimately responsible for placing and compacting the soil out to the slope face to obtain a relative compaction of 90 percent as evaluated by ASTM D 1557 and a moisture content in accordance with Sec- tion 5. The geotechnical consultant shall perform field moisture and density tests at intervals of one test for approximately every 10,000 square feet of slope face and/or approximately every 10 feet of vertical height of slope. 7.2.8. Backdrains shall be provided in fill slopes in accordance with the details pre- sented on Figure A of these guidelines, or as recommended by the geotechnical consultant. 7.3. Top-of-Slope Drainage 7.3.1. For pad areas above slopes, positive drainage shall be established away from the top of slope. This may be accomplished utilizing a berm and pad gradient of 2 percent or steeper at the top-of-slope areas. Site runoff shall not be per- mitted to flow over the tops of slopes. 7.3.2. Gunite-lined brow ditches shall be placed at the top of cut slopes to redirect surface runoff away from the slope face where drainage devices are not oth- erwise provided. 7.4. Slope Maintenance 106270001 TEG doc 7.4.1. In order to enhance surficial slope stability, slope planting shall be accom- plished at the completion of grading. Slope plants shall consist of deep- rooting, variable root depth, drought-tolerant vegetation. Native vegetation is generally desirable. Plants native to semiarid and arid areas may also be ap- propriate. Large-leafed ice plant should not be used on slopes. A landscape 10 Rev 12/05 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 architect shall be consulted regarding the actual types of plants and planting configuration to be used. 7 .4.2. Irrigation pipes shall be anchored to slope faces and not placed in trenches excavated into slope faces. Slope irrigation shall be maintained at a level just sufficient to support plant growth. Property owners shall be made aware that over watering of slopes is detrimental to slope stability. Slopes shall be moni- tored regularly and broken sprinkler heads and/or pipes shall be repaired immediately. 7.4.3. Periodic observation of landscaped slope areas shall be planned and appropri- ate measures taken to enhance growth oflandscape plants. 7 .4.4. Graded swales at the top of slopes and terrace drains shall be installed and the property owners notified that the drains shall be periodically checked so that they may be kept clear. Damage to drainage improvements shall be repaired immediately. To reduce siltation, terrace drains shall be constructed at a gra- dient of 3 percent or steeper, in accordance with the recommendations of the project civil engineer. 7.4.5. If slope failures occur, the geotechnical consultant shall be contacted immedi- ately for field review of site conditions and development of recommendations for evaluation and repair. 8. TRENCH BACKFILL The following sections provide recommendations for backfilling of trenches. 8.1. Trench backfill shall consist of granular soils (bedding) extending from the trench bottom to 1 or more feet above the pipe. On-site or imported fill which has been evaluated by the geotechnical consultant may be used above the granular backfill. The cover soils directly in contact with the pipe shall be classified as having a very low expansion potential, in accordance with UBC Standard 18-2, and shall contain no rocks or chunks of hard soil larger than 3/4-inch in diameter. 8.2. Trench backfill shall, unless otherwise recommended, be compacted by mechanical means to 90 percent relative compaction as evaluated in accordance with ASTM D 1557. Backfill soils shall be placed in loose lifts 8-inches thick or thinner, mois- ture conditioned, and compacted in accordance with the recommendations of Section 5. of these guidelines. The backfill shall be tested by the geotechnical con- sultant at vertical intervals of approximately 2 feet of backfill placed and at spacings along the trench of approximately I 00 feet in the same lift. I 0627000 I TEG doc 11 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 8.3. Jetting of trench backfill materials is generally not a recommended method of den- sification, unless the on-site soils are sufficiently free-draining and provisions have been made for adequate dissipation of the water utilized in the jetting process. 8.4. If it is decided that jetting may be utilized, granular material with a sand equivalent greater than 30 shall be used for backfilling in the areas to be jetted. Jetting shall generally be considered for trenches 2 feet or narrower in width and 4 feet or shal- lower in depth. Following jetting operations, trench backfill shall be mechanically compacted to the specified compaction to finish grade. 8.5. Trench backfill which underlies the zone of influence of foundations shall be me- chanically compacted to 90 percent relative compaction, as evaluated in accordance with ASTM D 1557. The zone of influence of the foundations is generally defined as the roughly triangular area within the limits of a 1:1 projection from the inner and outer edges of the foundation, projected down and out from both edges. 8.6. Trench backfill within slab areas shall be compacted by mechanical means to a relative compaction of 90 percent relative compaction, as evaluated in accordance with ASTM D 1557. For minor interior trenches, density testing may be omitted or spot testing may be performed, as deemed appropriate by the geotechnical consult- ant. 8.7. When compacting soil in close proximity to utilities, care shall be taken by the grading contractor so that mechanical methods used to compact the soils do not damage the utilities. If the utility contractors indicate that it is undesirable to use compaction equipment in close proximity to a buried conduit, then the grading con- tractor may elect to use light mechanical compaction equipment or, with the approval of the geotechnical consultant, cover the conduit with clean granular ma- terial. These granular materials shall be jetted in place to the top of the conduit in accordance with the recommendations of Section 8.4 prior to initiating mechanical compaction procedures. Other methods of utility trench compaction may also be appropriate, upon review by the geotechnical consultant and the utility contractor, at the time of construction. 8.8. Clean granular backfill and/or bedding materials are not recommended for use in slope areas unless provisions are made for a drainage system to mitigate the poten- tial for buildup of seepage forces or piping of backfill materials. 8.9. The contractor shall exercise the specified safety precautions, in accordance with OSHA Trench Safety Regulations, while conducting trenching operations. Such precautions include shoring or laying back trench excavations at 1:1 or flatter, de- pending on material type, for trenches in excess of 5 feet in depth. The geotechnical consultant is not responsible for the safety of trench operations or stability of the trenches. 106270001 TEG doc 12 Rev 12/05 La Costa Avenue Slope Failure Carlsbad, California 9. DRAINAGE Appendix C Project No. 106270001 The following sections provide recommendations pertaining to site drainage. 9.1. Canyon subdrain systems recommended by the geotechnical consultant shall be in- stalled in accordance with the Canyon Subdrain Detail, Figure C, provided in these guidelines. Canyon subdrains shall be installed to conform to the approximate alignment and details shown on project plans. The actual subdrain location shall be evaluated by the geotechnical consultant in the field during grading. Materials specified in the attached Canyon Subdrain Detail shall not be changed or modified unless so recommended by the geotechnical consultant. Subdrains shall be sur- veyed by a licensed land surveyor/civil engineer for line and grade after installation. Sufficient time shall be allowed for the surveys prior to commence- ment of filling over the subdrains. 9.2. Typical backdrains for stability, side hill, and shear key fills shall be installed in accordance with the details provided on Figure A, Figure F, and Figure G of these guidelines. 9.3. Roof, pad, and slope drainage shall be such that it is away from slopes and struc- tures to suitable discharge areas by non erodible devices (e.g., gutters, downspouts, concrete swales, etc.). 9.4. Positive drainage adjacent to structures shall be established and maintained. Posi- tive drainage may be accomplished by providing drainage away from the foundations of the structure at a gradient of 2 percent or steeper for a distance of 5 feet or more outside the building perimeter, further maintained by a graded swale leading to an appropriate outlet, in accordance with the recommendations of the project civil engineer and/or landscape architect. 9.5. Surface drainage on the site shall be provided so that water is not permitted to pond. A gradient of 2 percent or steeper shall be maintained over the pad area and drainage patterns shall be established to remove water from the site to an appropri- ate outlet. 9.6. Care shall be taken by the contractor during finish grading to preserve any berms, drainage terraces, interceptor swales or other drainage devices of a permanent na- ture on or adjacent to the property. Drainage patterns established at the time of finish grading shall be maintained for the life of the project. Property owners shall be made very clearly aware that altering drainage patterns may be detrimental to slope stability and foundation performance. 106270001 TEG.doc 13 Rev 12/05 La Costa Avenue Slope Failure Carlsbad, California 10. SITE PROTECTION The site shall be protected as outlined in the following sections. Appendix C Project No. 106270001 1 0.1. Protection of the site during the period of grading shall be the responsibility of the contractor unless other provisions are made in writing and agreed upon among the concerned parties. Completion of a portion of the project shall not be considered to preclude that portion or adjacent areas from the need for site protection, until such time as the project is finished as agreed upon by the geotechnical consultant, the client, and the regulatory agency. 1 0.2. The contractor is responsible for the stability of temporary excavations. Recom- mendations by the geotechnical consultant pertaining to temporary excavations are made in consideration of stability of the finished project and, therefore, shall not be considered to preclude the responsibilities of the contractor. Recommendations by the geotechnical consultant shall also not be considered to preclude more restrictive requirements by the applicable regulatory agencies. 1 0.3. Precautions shall be taken during the performance of site clearing, excavation, and grading to protect the site from flooding, ponding, or inundation by surface runoff. Temporary provisions shall be made during the rainy season so that surface runoff is away from and off the working site. Where low areas cannot be avoided, pumps shall be provided to remove water as needed during periods of rainfall. 1 0.4. During periods of rainfall, plastic sheeting shall be used as needed to reduce the po- tential for unprotected slopes to become saturated. Where needed, the contractor shall install check dams, desilting basins, riprap, sandbags or other appropriate de- vices or methods to reduce erosion and provide the recommended conditions during inclement weather. 10.5. During periods of rainfall, the geotechnical consultant shall be kept informed by the contractor of the nature of remedial or precautionary work being performed on site (e.g., pumping, placement of sandbags or plastic sheeting, other labor, dozing, etc.). 1 0.6. Following periods of rainfall, the contractor shall contact the geotechnical consult- ant and arrange a walk-over of the site in order to visually assess rain-related damage. The geotechnical consultant may also recommend excavation and testing in order to aid in the evaluation. At the request of the geotechnical consultant, the contractor shall make excavations in order to aid in evaluation of the extent of rain-related damage. 10.7. Rain-or irrigation-related damage shall be considered to include, but may not be limited to, erosion, silting, saturation, swelling, structural distress, and other ad- verse conditions noted by the geotechnical consultant. Soil adversely affected shall be classified as "Unsuitable Material" and shall be subject to overexcavation and I 0627000 I TEG doc 14 Rev 12/05 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 replacement with compacted fill or to other remedial grading as recommended by the geotechnical consultant. 1 0.8. Relatively level areas where saturated soils and/or erosion gullies exist to depths greater than 1 foot shall be overexcavated to competent materials as evaluated by the geotechnical consultant. Where adverse conditions extend to less than 1 foot in depth, saturated and/or eroded materials may be processed in-place. Overexcavated or in-place processed materials shall be moisture conditioned and compacted in ac- cordance with the recommendations provided in Section 5. If the desired results are not achieved, the affected materials shall be overexcavated, moisture conditioned, and compacted until the specifications are met. 10.9. Slope areas where saturated soil and/or erosion gullies exist to depths greater than 1 foot shall be overexcavated and replaced as compacted fill in accordance with the applicable specifications. Where adversely affected materials exist to depths of 1 foot or less below proposed finished grade, remedial grading by moisture condi- tioning in-place and compaction in accordance with the appropriate specifications may be attempted. If the desired results are not achieved, the affected materials shall be overexcavated, moisture conditioned, and compacted until the specifica- tions are met. As conditions dictate, other slope repair procedures may also be recommended by the geotechnical consultant. 10.1 0. During construction, the contractor shall grade the site to provide positive drainage away from structures and to keep water from ponding adjacent to structures. Water shall not be allowed to damage adjacent properties. Positive drainage shall be main- tained by the contractor until permanent drainage and erosion reducing devices are installed in accordance with project plans. 106270001 TEG doc 15 Rev. 12/05 La Costa Avenue Slope Failure Carlsbad, California 11. DEFINITIONS OF TERMS ALLUVIUM: AS-GRADED (AS-BUILT): BACK CUT: BACKDRAIN: BEDROCK: BENCH: BORROW (IMPORT): BUTTRESS FILL: CIVIL ENGINEER: CLIENT: COLLUVIUM: COMPACTION: 106270001 TEG doc Appendix C Project No. 106270001 Unconsolidated detrital deposits deposited by flowing water; includes sediments deposited in river beds, canyons, flood plains, lakes, fans at the foot of slopes, and in estuaries. The site conditions upon completion of grading. A temporary construction slope at the rear of earth-retaining structures such as buttresses, shear keys, stabilization fills, or retaining walls. Generally a pipe-and-gravel or similar drainage system placed behind earth-retaining structures such as buttresses, stabilization fills, and retaining walls. Relatively undisturbed in-place rock, either at the surface or beneath surficial deposits of soil. A relatively level step and near-vertical riser excavated into sloping ground on which fill is to be placed. Any fill material hauled to the project site from off-site areas. A fill mass, the configuration of which is designed by engi- neering calculations, to retain slopes containing adverse geologic features. A buttress is generally specified by a key width and depth and by a backcut angle. A buttress normally contains a back drainage system. The Registered Civil Engineer or consulting firm responsible for preparation of the grading plans and surveying, and evaluating as-graded topographic conditions. The developer or a project-responsible authorized represen- tative. The client has the responsibility of reviewing the findings and recommendations made by the geotechnical consultant and authorizing the contractor and/or other con- sultants to perform work and/or provide services. Generally loose deposits, usually found on the face or near the base of slopes and brought there chiefly by gravity through slow continuous downhill creep (see also Slope Wash). The densification of a fill by mechanical means. 16 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California CONTRACTOR: DEBRIS: ENGINEERED FILL: Appendix C Project No. 106270001 A person or company under contract or othetwise retained by the client to perform demolition, grading, and other site improvements. The products of clearing, grubbing, and/or demolition, or contaminated soil material unsuitable for reuse as compacted fill, and/or any other material so designated by the geotech- nical consultant. A fill which the geotechnical consultant or the consultant's representative has observed and/or tested during placement, enabling the consultant to conclude that the fill has been placed in substantial compliance with the recommendations of the geotechnical consultant and the governing agency re- quirements. ENGINEERING GEOLOGIST: A geologist registered by the state licensing agency who ap- plies geologic knowledge and principles to the exploration and evaluation of naturally occurring rock and soil, as re- lated to the design of civil works. EROSION: The wearing away of the ground surface as a result of the movement of wind, water, and/or ice. EXCAVATION: The mechanical removal of earth materials. EXISTING GRADE: The ground surface configuration prior to grading; original grade. FILL: Any deposit of soil, rock, soil-rock blends, or other similar materials placed by man. FINISH GRADE: The as-graded ground surface elevation that conforms to the grading plan. GEOFABRIC: An engineering textile utilized in geotechnical applications such as subgrade stabilization and filtering. GEOTECHNICAL CONSULTANT: The geotechnical engineering and engineering geology con- sulting firm retained to provide technical services for the project. For the purpose ofthese specifications, observations by the geotechnical consultant include observations by the geotechnical engineer, engineering geologist and other per- sons employed by and responsible to the geotechnical consultant. I 0627000 I TEG doc 17 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California GEOTECHNICAL ENGINEER: GRADING: LANDSLIDE DEPOSITS: OPTIMUM MOISTURE: RELATIVE COMPACTION: ROUGH GRADE: SHEAR KEY: SITE: SLOPE: SLOPE WASH: SLOUGH: SOIL: I 06270001 TEG doc Appendix C Project No. 106270001 A licensed civil engineer and geotechnical engineer, regis- tered by the state licensing agency, who applies scientific methods, engineering principles, and professional experience to the acquisition, interpretation, and use of knowledge of materials of the earth's crust to the resolution of engineering problems. Geotechnical engineering encompasses many of the engineering aspects of soil mechanics, rock mechanics, geology, geophysics, hydrology, and related sciences. Any operation consisting of excavation, filling, or combina- tions thereof and associated operations. Material, often porous and of low density, produced from instability of natural or manmade slopes. The moisture content that is considered optimum to compac- tion operations. The degree of compaction (expressed as a percentage) of a material as compared to the dry density obtained from ASTM test method D 1557. The ground surface configuration at which time the surface elevations approximately conform to the approved plan. Similar to a subsurface buttress; however, it is generally con- structed by excavating a slot within a natural slope in order to stabilize the upper portion of the slope without encroach- ing into the lower portion of the slope. The particular parcel of land where grading is being per- formed. An inclined ground surface, the steepness of which is gener- ally specified as a ratio of horizontal units to vertical units. Soil and/or rock material that has been transported down a slope by gravity assisted by the action of water not confined to channels (see also Colluvium). Loose, uncompacted fill material generated during grading operations. Naturally occurring deposits of sand, silt, clay, etc., or com- binations thereof. 18 Rev 12105 La Costa Avenue Slope Failure Carlsbad, California STABILIZATION FILL: SUBDRAIN: TAILINGS: TERRACE: TOPSOIL: WINDROW: 106270001 TEG doc Appendix C Project No. 106270001 A fill mass, the configuration of which is typically related to slope height and is specified by the standards of practice for enhancing the stability of locally adverse conditions. A stabi- lization fill is normally specified by a key width and depth and by a backcut angle. A stabilization fill may or may not have a back drainage system specified. Generally a pipe-and-gravel or similar drainage system placed beneath a fill along the alignment of buried canyons or former drainage channels. Non-engineered fill which accumulates on or adjacent to equipment haul roads. A relatively level bench constructed on the face of a graded slope surface for drainage and maintenance purposes. The upper zone of soil or bedrock materials, which is usually dark in color, loose, and contains organic materials. A row of large rocks buried within engineered fill in accor- dance with guidelines set forth by the geotechnical consultant. 19 Rev 12/05 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 FILL SLOPE OVER NATURAL GROUND SWALE AT TOP OF SLOPE / OUTLET PIPE DRAINS TO A SUITABL£ OUTLET IN ACCORDANCE WITH THE RECOMMENDATIONS OF THE CIVIL ENGINEER NATURAL GROUND NATURAL GROUND j_---- FILL_/ BENCH INCLINED SLIGHTLY INTO SLOPE 10' TYP--i BEDROCK OR I COMPETENT MATERIAL, .-/ ~ AS EVALUATED BY THE BACKDRAIN AND T-CONNECTION (SEE DRAIN DETAIL, FIGURE G) f GEOTECHNICAL CONSULTANT FILL SLOPE OVER CUT SWALE AT TOP OF SLOPE BENCH INCliNED SLIGHTLY INTO SLOPE f--lo' TYP--i BEDROCK OR / COMPETENT MATERIAL, _/ ~ AS EVALUATED BY THE f GEOTECHNICAL CONSULTANT BACK DRAIN AND T-CONNECTION {SEE DRAIN DETAIL, FIGURE G) *MINIIo4UM KEY WIDTH DIMENSION. ACTUAL WIDTH SHOULD BE PROVIDED BY GEOTECHNICAL CONSULTANT BASED ON EVALUATION Of SITE -SPECIF1C GEOTECHNICAL CONDmONS. NOTES: CUT SLOPE SHALL BE CONSTRUCTED PRIOR TO PLACEMENT OF RLL. aorthfo.dwg I 0627000 I TEG doc SLOPE DRAINAGE SHOULD BE PROVIDED IN ACCORDANCE WITH RECOMMENDATIONS PRESENTED ON fiGURE E NOT TO SCALE FILL SLOPE OVER NATURAL GROUND OR CUT La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 TRANSITION (CUT-FILL) LOT "''"''' ,,.,~ -- t COMPACTED FILL __I T OVEREXCAVATE AND RECOMPACT BEDROCK OR COMPETENT MATERIAL, ~ ~ AS EVALUATED BY THE ___...../ / GEOTECHNICAL CONSULTANT UNDERCUT LOT ~ N~RAL GROUND .-?' ___...--~ ------ 3' MIN. T OVEREXCAVATE AND RECOMPACT BEDROCK OR COMPETENT MATERIAL, ,- ~ AS EVALUATED BY THE ___...../ / GEOTECHNICAL CONSULTANT NOTE: DIMENSIONS PROVIDED IN THE DETAILS ABOVE ARE APPROXIMATE AND MAY BE MODiriED IN THE fiELD BY THE GEOTECHNICAL CONSULTANT AS CONDITIONS DICTATE. 10627000 I TEG doc NOT TO SCALE TRANSITION AND UNDERCUT LOT DETAILS FIGURE B La Costa Avenue Slope Failure Carlsbad, California CANYON SUBDRAIN NATURAL GROUND SEE FIGURE A FOR DETAILS OF BENCHES LOWEST BENCH INCLINED TOWARD DRAIN COMPACTED FILL - SUB DRAIN (SEE DRAIN DETAIL, rJGURE G) Appendix C Project No. 106270001 DETAIL OF CANYON SUBDRAJN TERMINATION DESIGN fiNISH GRADE SUBORAIN PIPE CUTOFF WALL CONSTRUCTED OUTLET PIPE DRAINS TO A SUITABLE OUTLET IN ACCORDANCE WITH THE OF GROUT, CONCRETE, BENTONITE, OR OTHER SUITABLE MATERIAL AS EVALUATED BY THE GEOTECHNICAL CONSULTANT RECOMMENDATIONS Of THE CIVIL ENGINEER - I 0627000 I TEG doc . . . · ~ FILTER MATERIAL ~~==========~~==~~====·~·=·~======~ ~ ·' ,· ;_·.-- NON-PERFORATED PIPE--+---PERFORATED PIPE 5' 20' MIN. IN. NOT TO SCALE a are -CANYON SUBDRAIN DETAIL FIGlflE c La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 WINDROW SECTION 30 5.1:. SOIL (rL.OOOCD) ~ '-.... I -~ -..... L-~ I __ ...... _J..--'_ ~~j "V" OR lii:CT~Glii.AR Ilii:NCH A ~INI~l.JM ~ Dr l r1:1:1 DI:I:P AND :0 ri:I:T WIDI: rXCAVA1T[) INTD COIAI'ACTrD rill. OR NAlURAL GROU~D PAD SECTION 70tlr A nt.fiSH GRAD!: :ZOI4C B t.IAitRIAL <=> ~ ~rrr . . ' 8' OR 2' DI:L.0\11 DCtF'I:ST PROPOSI"D UTILITY, WHII:tlrVI"R IS Slli'.ATfR 10Nr k COIIIPACII"D nLL WITH i;OtK ra.r.r;ur~ NO otiii'A'TI'n nlAN I ll«<lr! IN IIIWrTrll. 70Nr 1k ti:IMP.t.ClfD nLL WITH RDCK riA~Ufl'ml linYI'n"N I AND <13 IICHnl lrt IIWinrR W.T lir PI.AI:rla ~ SJAGGI"IIirD YJI"g~5 UP ll:J 1110" LONII I" 1HI~ ;r;!JN!;; ~g :SVIIIItJUNilW ll liiWIUI.N[ ~OIL. (lO 5AND WUI'I'AL~I'Il) D~IW IT fl.OQDIN~ RIJCI\ f"IWjiii:N~ 1.,1;'515 THNt ~ ll'al~ IN IIW.A!;;TtR I<MT Iii~ PI.At;W Ill Qlltro\Cf!;;l) fiL.L. ~OIL. 106270001 TEG doc NOT TO SCALF OVERSIZED ROCK PLACEMENT DETAIL FlGURE 0 La Costa Avenue Slope Failure Carlsbad, California Appendix C Project No. 106270001 eorthfe.dwg 106270001 TEG doc MID-SLOPE BACKDRAIN (SEE DRAIN DETAIL, SWALE AT TOP Of SLOPE -'15''-IMJN.j FIGURE G) --~- NON-PERFORATED OUTLET PIPE REINFORCED CONCRETE- PAVED TERRACE (SWALE) 2% ~ MAXIMUM VERTICAL SLOPE HEIGHT, H (FEET) LESS THAN 30 60 120 GREATER THAN 120 BEDROCK OR COMPETENT MATERIAL AS EVAWATED BY THE GEOTECHNICAL CONSULTANT WHEN POSSIBLE, LOWEST BACKDRAIN SHOULD BE PLACED IN THE BASE OF KEY (SEE DRAIN DETAIL, FIGURE G) * TERRACE WIDTH AND LOCATION NO TERRACE REQUIRED ONE TERRACE AT LEAST 6 FEET WIDE AT MIDHEIGHT ONE TERRACE AT LEAST 12 FEET WIDE AT APPROXIMATELY MIDHEIGHT AND 6-FOOT WIDE TERRACES CENTERED IN REMAINING SLOPES DESIGNED BY CIVIL ENGINEER WITH APPROVAL OF GOVERNING AUTHORITIES NOTES: 1. t.IID-SLOPE BACKORAINS SHOULD BE PL.>.CED IN Fill SLOPES IN CONJUNCTION WITH UCH TERRACE. 2. TERRACES SHOULD HAVE AT LEAST A 5-PERCENT GRADIENT, AND RUN orr SHOULD !If DIRECTED TO AN APPROPRIATE SURFACE DRAINAGE COLlECTOR. 3. TERRACES SHOULD BE CLUNED Of DEBRIS AND VEGETATION TO ALLOW UNRESTRICTED flOW Of WATER. 4. T£RRACES SHOULD BE KEPT IN GOOD REPAIR. 5. RITER TO UBC CHAPTER 70 fOR ADDITIONAL REQUIREMENTS. NOT TO SCALE SLOPE DRAINAGE DETAIL FIGURE E La Costa Avenue Slope Failure Carlsbad, California COMPACTED FILL -------.._ .._ Appendix C Project No. 106270001 r----PROPOSED GRADED SURFACE EXISTING GROUND SURFACE .......... UNSTABLE__) f MATERIAL BENCH INCUNED ..._ SUGHTL Y INTO SLOPE ..._ (SEE FIGURE A) P.LA~ 0~ :K~E7 - BEDROCK OR r COMPETENT MATERIAL, 1 AS EVALUATED BY THE GEOTECHNICAL CONSULTANT BACK DRAIN (SEE DRAIN DETAIL, FIGURE G} COMPACTED FILL T DEPTH OF KEY ~~~=====-1 =z% r---KEY WIDT~ NON-PERFORATED OUTLET PIPE NOTES: 1. THE DEPTH AND WIDTH Of kEY WlLL BE PROVIDED BY THE GEOTECHNICAL CONSULTANT BASED ON ANALYSIS OF SITE-SPECiriC GEOTECHNICAL CONDITIONS. 2. AN ADDITIONAL f.IID-SLOPE BACKDRAIN AND TERRACE DRAIN MAY BE RECOUMENDED FOR SLOPES OVER 30 FEET HIGH. SEE SlOPE DRAINAGE DETAIL. FIGURE E. 3. SLOPE DRAINAGE SHOUlD BE PROVIDED IN ACCORDANCE WITH RECOMMENDATIONS PRESENTED ON FIGURE E. NOT TO SCALE SHEAR KEY DETAIL FIGI.RO F 106270001 TEG.doc La Costa Avenue Slope Failure Carlsbad, California SUBDRAIN CONFIGURATION ALTERNATIVE A* ALTERNATIVE 8 PERFORATED PIPE INSTALLED WITH PERFORATION DOWN (SEE SCHEDULE BELOW) * ALTERNATIVE A SUBDRAIN CONFIGURATION MAY BE USED IN FILLS LESS THAN 25 FEET DEEP Appendix C Project No. 106270001 BACKDRAIN CONFIGURATION T -CONI'l£CTION (SEE DETAIL) FILTER MATERIAL (3 CUBIC f"EET PER LINEAR FOOT) PERFORATED PIPE, 4" MIN. SCH'EOULE 40 PVC OR EQUIVALENT INSTALLED WITH PERFORATIONS DOWN T -CONNECTION DETAIL PERFORATED PIPE SLOPED AT 1% MIN. I_ 10• MIN _I TOWARD OUTLET PIPE --:\ [EACH S1Dfl ><OH-PERFORA"D 0\JTLET PIPE UP TO~R ~END CAP 100' ON CENTER HORIZONTALLY FILTER MATERIAL FILTER MATERIAl SHAlL BE CLASS II PERMEABLE MATERIAL PER STATE Of CAlifORNIA STANDARD SPEC!FlCA liONS OR APPROVED ALTERNATE GEOFABRJC DRAIN SYSTEM. SIEVE SIZE 1" 3/4" 3/8" No. 4 No. 8 No. 30 No. 50 No. 200 CLASS II GRADATIONS PERCENT PASSING 100 90-100 4D-100 25-40 18-33 5-15 D-7 0-3 NOTE: AS AN ALTERNATIVE THE fiLTER MATERIAL MAY CONSIST Of UP TO 1" DIAMETER OPEN-GRADED GRAVEL WRAPPED IN AN APPROVED GEOFABRIC WITH 6-INCH OR MORE OVERLAP. eortl>fg.dwg 106270001 TEG doc PIPE SCHEDULE PERFORATED AND NON-PERFORATED PIPE SHALL BE SCHEDULE 40 POLYVINYL CHLORIDE (PVC) OR ACRYLONJTRILE BUTADIENE STYRENE (ABS) OR EQUIVAlENT. AND WILL HAVE A MINIMUM CRUSHING STRENGTH OF 1000 PSI FOR DEPTHS OF FILL UP TO 50 FEET. FOR DEEPER FllLS, PERFORATED AND NON-PERfORATED PIPE SHOULD BE DESIGNED WITH ADEQUATE CRUSHING STRENGTH. THE PIPE DIAMETER WILL GENERALLY MEET THE FOLLOWING CRITERIA, BUT MAY BE MODIFIED IN THE FlELD BY THE GEOTECHNICAL CONSULTANT AS CONDITIONS OlCTATE. THE LENGTH OF RUN IS MEASURED FROM THE HIGHEST ELEVATION. LENGTH Of RUN 0-500' 500-1500' > 1500" PIPE DIAMETER 4" 6" 8" NOT TO SCALE DRAIN DETAIL