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HomeMy WebLinkAboutCT 82-23; PLAZA PASEO REAL; PRELIMINARY GEOTECHNICAL INVESTIGATION; 1987-03-24I I 1. I I 1 PRELIMINARY GEOTECHNICAL INVESTIGATION PROPOSED COMMERCIAL DEVELOPMENT I CITY PARCEL. 1, A.P. 215-050-61 OF CARLSBAD, CALIFORNIA I PREPAiED iR: MR. FRET) VON fZ I F.T. VON DE A." -7- CCV.ANY i1 DOVE ST1EEV. UiT. 242 BEACH, CALIFORNL8 i NEWPORT I I, :I MARCH 24, 1987 PROJECT NO. 100170-01 I, 'I I I F.T. \'oa Der Ahe Company March 24, 1987 Project No. 100170-01 Table of Contents Page Introduction ........................................................... .......................................... 1 Scope of Services ........................................................................................... 1 Site Description .............................................................................................. 2 Proposed Development....................................................................................2 Subsurface Exploration....................................................................................3 Laboratory Testing.........................................................................................3 Geology ...................................................... ...................................................... 3 Ground Wate, ................................................................................................. 4 Sisricty.......................................................................................... .............. 4 EarthquakeEffects .......................................................................................... 5 Conclusions and Recommendations ................................................................... 6 's•' '.• r , - ,'vO, A.. ................................................................................................. I Faticn azi Slab Reco:nmends:ions..................... . ........................... . Surface Drainage ........................................................... .....................11 Pavement Design ................................................................................... .1 2 Construction Observation..............................................................................12 I Illustrations Figure 1 — Site Location Map Figure 2 — Geologic Map Figure 3 — Subdrain Detail Figure 4 — Benching Detail I I F T Von Dr Abe Compary March 24, 1987 Project No. 100170-01 I I Table 1 - Seismic Parameters for Active Faults I Appendices Appendix A - References ' Appendix B - Test Pit Logs Appendix C - Laboratory Test Summary Appendix D - Slope Stability E - Property Maintenance Guidelines, for Homeowners i Appendix I S S I 'I 5. .1 . I . I I ' S 1 O&ffil Geotechnical Consultants I . March 24, 1987 Project No. 100170-01 1 F.T. Von Der Ahe Company I 1601 Dove Street, Suite 242 Newport Beach, California 92660 I Attention: , Mr. Fred Von Der Ahe Subject: , Preliminary Geotechnical Investigation, Proposed I . Commercial Development, Parcel 1, A.P. No. 215-050-61, City of Carlsbad, California I Introduction In accordance with your request and authorization, we have performed a geotechni- I ci investigation of the subject site. This investigation was performed to evaluate for development the suitability of the site, the proposed and to provide rec- ommandatlons ralative to sitet grading and building fcundation desgn. Scope of Services The scope of services included background search, field investigation, and laboratory testing and geotechnical analysis. Specifically, the following tasks were performed: I. Review of the geotechnical literature referenced in Appendix A. I o Geotechnical site reconnaissance. A subsurface investigation that consisted of eight backhoe-excavated .test pits to evaluate subsurface soil conditions. Test pits were logged I and sampled by a geologist from this firm. I Soil Engineering o Geology a Groundwater 1 10225 Barnes Canyon Road • Suite A-112 • San Diego. CA 92121 c (619) 457-0400 F.T. Von der Ahe Company March 24, 1987 Project No. 100170-01 I 1 Geologic mapping of the site. Laboratory testing of representative soil samples. I o Geotechnical engineering analysis of the accumulated data. a Preparation of this report which presents our findings, conclusions, and I : recommendations. I Site Description I Costa The subject site consists of a roughly rectangular 8-acre parcel located in the La Carlsbad, area of California (see Figure 1, Site Location Map). The site is bounded by El Caminô Real on the east, a graded parcel to the south and undevel- oped parcels to the north and west. -The topography of the site may be divided into two sections. The western quarter of the site is marked by a west facing I . slope, whereas the eastern portion of the site slopes toward the south. Slope ratios vary between 10:1 (horizontal to vertical) and 1:1 . (horionta1. to vertical). Generally north-south trending erosion gullies extend to depths of approximately 5 I . feet but locally are in excess of 20 feet deep in the southern portion of the site. Vegetation on the site is composed of a moderately dense growth of coastal I sagebrush charraI. At the time of our site exploration, the only improvements to the site :poeared to be the construction of. two desilting ponds and drainage inlets. I These drainage improvements are located along the southern property boundary. Proposed Development Detailed development plans were . unavailable for our review at the time of this in- vest igation. However it is our understanding that cut and fill grading techniques may be used to construct relatively level building pads, roadways and parking areas. I : Proposed Structures may include one- and two-story commercial type buildings. An- ticipated loads for the proposed structures are consistent with this type of con- - . struction. I . . 2 1 I F.T. Von der Ahe Company March 24, 1987 Project No. 100170-01 Subsurface Exploration Subsurface exploration consisted of excavating eight test pits to a maximum depth of 13 feet. The test pits were excavated with a light duty backhoe. The test pits were observed, logged, and sampled by a geologist from this office. Undisturbed and bulk samples were obtained for laboratory testing. Test pit locations are shown on Figure 2. Test pit logs are included in Appendix B. Laboratory Testing Laboratory tests were performed on representative soil samples obtained during ex- cavation to evaluate engineering characteristics. Laboratory tests included in-place moisture and density, U.B.C. Expansion Index tests, maximum density tests, and di- rect shear. tests. A description of laboratory tests and a summary of test results are presented in Appendix C. The subject site is located in the Coastal Plain of the Peninsular Ranges Geomor- phic Province, near the eastern margin of the Southern California Batholith. As rapped by Tan (Appendix A, Reference 4), the site Is underlain by the middle Eocene Scripps Formation. Geologic materials observed during our exploration in- cluded both soil and bedrock units. Brief descriptions of the units observed are presented below. Fill (Map symbol Qaf) Fill soils were encountered along the southern portion of the site. These soils consisted of brown to black, damp, medium dense, sandy clay and clayey sand. Fill soils were encountered to a maximum depth of 5.5 feet in test pit T-2. Documentation regarding fill place- ment was not available for our review. 1 I 3 I 1 I I I Ii] I 1 I I I I F.T. Von der Ahe Company March 24, 1987 Project No. 100170-01 Topsoil Topsoil was encountered throughout the site. In general topsoil con- sists of a light brown, moist to wet, loose to medium dense, silty sand. Topsoils were encountered to 4.0 feet in test pit T-4, but aver- aged 2.5 feet throughout the site. Bedrock (Map symbol Tsc) The entire site is underlain by the Eocene Scripps Formation. This unit generally consists of a brown-gray, massive, fine to medium grained, dense, sandstone with interbeds of. siltstone and claystone. Ground \Vater Ground v-nter was not encountered in any of the test pits. 'Sei smicitv The sue is located within a seismically active region. However, no active faults were observed on or adjacent to the site. The overall seismic risk is considered low, as compared'to some other areas of Southern California, due to the distance to active faults and the presence of firm bedrock below the site. Seismic hazards within the site can be attributed to ground shaking resulting from events on distant active faults. Listed on Table 1 are the faults which signifi- cantly affect the site. 4 I I I I 1 I I I I 1 I 1 I I I I I I .1 F.T. Von der Abe Company March 24, 1987 ilr:ject No. 100170-01 Earthqiake_Effects Earthauake Accelerations Analysis of the possible earthquake accelerations at the site indicate that for the intended use, the most significant event is a 6.7 magni- tude earthquake located on the Elsinore Fault Zone. A magnitude 6.7 earthquake on the Elsinore Fault Zone could produce a peak bedrock acceleration of 0.14g at the subject site. Peak accelerations are not, hcwever, representative of the accelerations for which structures are actually designed. Design of structures should be completed in com- pliance with the requirements of the governing jurisdictions and stan- dard practices of the Structural Engineers Association of California. Liqueraction Liquefaction is known to occur in saturated, loose, sands and silts. Because ground water and/cr sstrcted soil were not encountored during this investigation, and all loose soil will he recompacted, the liquefaction potentici of :he site considered to be very low. Lurching and Shallow Ground Rupture Breaking of the ground due to active faulting is not likely to occur on the site due to the absence of active faults. Cracking due to shaking from distant events is not considered a significant hazard, although it is a possibility at any site. Landslides No areas within the site were identified as being susceptible to seismically induced !andsliding.. 5 11 F.T. Von der Ahe Company March 24, 1987 Project o. 100170-01 CONCLUSIONS AND RECOMMENDATIONS Based on the results of our investigation, it is our opinion that the subject site is suited for the proposed improvements from a geotechnical viewpoint provided that the preliminary recommendations presented in the following sections are incdrpo- rated into the design, grading, and construction aspects of the project. The fol- lowing is a summary of significant geotechnical factors which will affect the development of the site. Site materials include soil and bedrock units. With the exception of the very dense unweathered bedrock, the site soil units (fill and topsoil) are in •a loose to medium dense condition, and will need to be removed and recompacted. Specific care should be used in the cleanout of the desilting ponds located along t!e southern portion of the site, ad the gulies which extend the length of the property. We anticipate that the site materia's may be excavated using conventional heavy duty earthrnoving equipment. The v6iune charge of excavated on-site materais u:ori recompsctlor as fill is expected to vary with rraterial . type and iooation. The soil and bedrock materials vary in natural and maximum density, and accu- rate overall determination of in-place and compacted density cannot be made. Therefore, accurate earthwork shrinkage estrnates cannot be determined. However, based on our limited laboratory testing and our experience with similar materials, the following shrinkage values are provided as guideline estimates: - Fill: 0 to 10 percent shrinkage. - Topsoil: Up to 20 percent shrinkage. - Bedrock: Up to 5 percent bulking. F.T. Von der Ahe Company •' March 24, 1987 Project No. 100170-01 The expansion ptential of the site materials varies from low for sand- stone-derived soil to medium to high for claystone-derived soil. Although ground water was not encountered in any of the test pits, and is not expected to significantly affect site grading, changes due to grade alteration and irrigation practices may significantly change the future ground water conditions. Earthwork- IV,- anticipate that the proposed construction will consist of cut and fill earthwork. Please note that no grading plans were available for our review prior to issuing this report. Final grading plans and specifications should he reviewed by the geotech- nical consultant to see if additional earthwork recommendations are needed. She Prerati)n Pro: to ding, the site should be cie:red of all undocumented fill, loose soil, veati -. ::rfce and bstfce o tructins, including any existing debris and bu:ei ii:cs, nf--; ' ;'d of vet.tio. Vegetaton d debris should be of off-sie. 1-lules resulting rroni removal of hried obstructions which extnc below finished graes should be filled with compacted soil. As previously stated there are several gulies on the site. These gullies should be fiied with properly c;mpacted flil. Prior to the placement of fill i;i these gullies all loose scil from the bottom and sides of the gullies should be removed to expose dense bedrock. The minimum width of the bottom of the resulting trench should be sufficient to provide adequate compaction of the soil. Excavation walls In dense bedrock may be constructed at slope ratios of 1:1 (horizontal to vertical). In order to reduce the potential for a buildup of hydrostatic pressure within the fill, a subdrain should be placed at the bottom of the drainage. The subdrain should be constructed at a gradknt which will allow for gravity flow, and exit at a suitable location. A subdrain detail is presented in Figure .3. 7 I F.T. Von der Ahe Company March 24, 1987 Project No. 100170-01 Additionally, there are several desilting basins along the southern portion of the site. All loose or saturated soil should be removed to expose dense bedrock within these basins prior to the placement of fill. Fills The on-site soils are generally suitable for use as compacted fill provided they are free of organic material and debris. Prior to the placement of fill, all loose soil should be removed to expose dense bedrock. The exposed surface should be scarified to a minimum depth of 6 inches, brought to near-optimum moisture conditions, and recompacted. Fills should generally be placed in uniform lifts not exceeding 8 inches. The optimum lift thickness to produce uniformly compacted fIll will depend on the size and type of construction equipment utilized Fill soils s1.Juld be moisture conditioned so that they are slightly above the optimum moisture coi;tent. Al fills should be cmpacted: to at lea_-. 90 pernent oz the maximum dry density as determined by ASIAN! 01557-7S. Fi!s placed on slopes steeper than 5:1 (horizontal to vertical) should be keyed and bched iito dense b:eck units see Figure 4. Ai fill slopes should be provided with an 3pproprat iw at the toe of the slope. This key should have a m 7ni!I1um width of 15 feet and be founded at least 2 feet into dense bedrock (see Figure 4). Fill slopes should be constructed at slope ratios of 2:1 (horizontal to vertical) or flatter. Fill slopes should be backrolled at frequent Intervals during construction of j the slope. At the completion of grading, the relative compaction of the entire iupe, including the slope face, should be at least 90 percent of the maximum dry density. Grading of Expansive Soils Any expansive soils encountered during grading operations should be placed in fill areas below a minimum depth of 3 feet measured from finished grade. Highly expansive soils should not be placed within 15 feet of the face of any slope to reduce the likelihood of surficial slope instability and sloughing. 1 8 F.T. Von der Ahe Company March 24, 1987 Pr.ject No. 100170-01 Transition Lots 3nd Lot Capping It is recommended that all cut pads exposing unsuitable materials such as expansive soil, topsoil, and the cut portions of 'transition lots (due to grading), be overexcavated a minimum depth of 2 feet beneath the deepest footing, for a minimum distance of 5 feet outside building areas. Based on in-grading inspection, localized deeper overexcavation and recompaction of the unsuitable soils may be re- quired. Trench Excavations and Backfill The on-site soils are generally suitable as utility trench backfill, provided they are screened of organic 'matter and cobbles over 6 inches in diameter. Backfill should be coinpcted in uniform lifts (not exceeding 8 inches iii coipacted thickness) by mechanical means to at least 90 percent r&'ative compaction (ASTM D 1557-78). Ste St ability Our calculations. for surficial stability (Appendix 0), ei!ming an in1iite slope and - cepc : ri lc' to tie ope cr. a c 'at'4 Ir of safetv of 1.3 or grear or fill slopes const.c.ed at a ratio of 2; t (horonta1 to verti- cal) or flatter. Gross stability calculations (Appendix D) for a fill slope constructed at a ratio of 2:1 (horizontal to vertical), show a calculated factor of safety of 1.5 or greater for sloe heights of 50 feet or less. Erosion and/or surficial failure potential of fill slopes may be reduced if the following ineasures are implemented during design and construction of the subject slopes: Selective Grading of Fill Materials We recommend against the exclusive use of either highly expansive clayey soils or poorly graded sands in the faces of fill slopes. Highly expansive soils are subject to surficial failures when exposed in slope faces. Poorly graded sands utilized in slope faces may be subject to I F.T. Von der Ahe Company March 24, 1987 Project No. 700170-01 excessive erosion and ruling. A thorough mixture of clayey and sandy fill soils is recommended to reduce the overall expansion potential and slope erosion. We recommend that mixture of soils he approved by the project geotechnical engineer prior to placement in fill slopes. Slope Landscaping and Drainage C] Cut and fill slopes should• be provided with appropriate surface drainage features and landscaped with drought-tolerant, slope stabilizing vegetation as soon as possible after grading to minimize the potential for erosion. Berms should be provided at the topof all slopes and lot drainage directed such that surface runoff on slope faces is minimized. Foundation and Slab Recommendations Proposed structures 'may be founded on 1sc.t'ed and/or contnuous footings bearing completely in rproperly compacted fill or dense be.rock. otcgs for relatively li,;ht-weight wood-frame srucres shoud aend to a thlrdmum !th of 12 nd 1 i:ches below Lhe lowest adjacent finished grade, for one- and cwo-story buildings, respectively. All footings should have 'a minimum width of 12 inches. If large warehouse-type structures are planned, they may be fOunded on isolated spread footings which are founded at least 3 inches below the lowest adjacent grade and are at !cast 24 inches wide. Isolated and continuous footings may be designed for a dead pius live, allowable soil bearing value of 2000 pounds per square foot. This value may be increased by one-third for wind or seismic loads. A lateral bearing value of 300 pounds per square foot per foot of depth, neglecting the initial foot I' of embedment, and a coefficient of friction between concrete and soil of 0.35 may be utilized. These values assume that footings will be constructed on clean, dense soils. .1: 10 It I F.T. Von der Abe Corn March 24, 1987pany Project No. 100170-01 I 1 Continuous footings should be reinforced with a minimum of four No. 4 reinforcing bars, two paced near the top and two near the bottom of the footings. Spread 1 footings should be reinforced as specified by the structural engineer. Footing ex- cavations should be observed by the geotechnical consultant prior to the placement 1 of reinforcing steel and concrete. Footings adjacent to slopes should be deepened to provide a minimum of 10 feet of horizontal distance between the outside edge of the footing and the slope face, measured from the bottom of the footing. Providing there will be no highly expansive soils placed in the upper 3 feet, floor 1 slabs should be at least 4 inches thick and be reinforced with a minimum of No. 3 bars spaced at 18 inches centers, with the bars placed on chairs so that the 1 reinforcement is in the center third of the slab. If moisture-sensitive floor cov- erings are planned, floor slabs should be underlain by a 6-mU Visqueen moisture barrier covered with 2 inches of clean washed sand and underlain by an additional 2 inches of cican washed sand. Slab subgrde S3iS hoUd be soaked to at least 3 I percent above optimum moisture content and tested by the geotechnical consultant prior to slab placement. I Wn understood that there arc no rc;osed retaining walls at the Sft3. If such wells are nned lateral earth pressures COP, ;rovicd by tha geotechnicel consultant. These recommendations are preliminary and based on current conditions. Expansion tes:ig at the completion of grading will be necessary to substantiate or modify these recommendations to reflect the as-graded condition. Surface Drainage I Surface drainage should be controlled at all times. Positive drainage should be provided to direct surfade water away from structures, slopes parking and driveways and toward the street or other suitable drainage facilities. Ponding of water on I the site should be avoided. We recommend that eave gutters and downspouts be I 11 F.T. Von der Ahe Company March 24, 1987 Project No. 100170-01 used. Roof runoff should not be allowed to discharge within 5 feet of the building. Area drains should be provided in areas of decking and lawns. Owners should be reminded of their responsibilities for the maintenance of. proper lot drainage, the undertaking of property improvements in accordance with sound engineering practices, and proper maintenance of vegetation Including cautious lot and slope irrigation (see Appendix E, Property Maintenance Guidelines for Home- owners). Pavement Design Design of .a pavement section will be based on. anticipated traffic and strength characteristics of the near-surface soils in the proposed roadways and parking areas. Recommended nave!nent sections will be provided as proposed grading is completed. Construction c'ervatf on Construction of founa:ion excavation, and testing and. observation, fill D1anment be -:orme by the goctenhnical consuitai. Addiiona1ly, all cut s•'es, finished arid/c.t eoorary istrctlon sopcs, should be evuated by the g-otechnical consultant. We recommend that grading plans be reviewed by the gec.echnical consultant so that the recommendations provided herein are incorporated in project plans. We further emphasize that the recommendations pro- vi.icd in this report may need to he modified or revised after review of detailed grading plans. . The field investIgation, laboratory testing and geotechnical analysis presented In this report have been conducted in accordance with current geotechnical practice. Our observations are based on test excavations located across the site and our recom- mendations reflect generally uniforin conditions . between the test excavations. Variations may exist and conditions not observed or described in this report may be encountered during construction. If conditions different from those described in 12 F.T. Von der Abe Company March 24, 1987 Project No. 100170-01 this report are encountered, this office should be notified and additional recommen- dations, if applicable, will be provided upon request. We appreêiate the opportunity to be of service, and if you should have any ques- tions regarding this matter pie9 this office. 01 Respectfully submitted, NINYO & MOORE --::~ Barry S Pulver, RG 4236 Projp-ct Geolist ZV Stephen W. jetr:n, CEG 1074 Princi'pal GeoIcgt -. Roy . Moore, RCE 28119 Plncipal Ut.Uor1: (41 Addressee 13 R.G. 4236 ! * \OFCAU vo 47o J - L - _L1Li2TPcJ r-- TT 2 I N, >< fl..• I '. 24 J-T / \SITE co jr I _26: f 25 I I ) FtO i I - V---' •ii -V "'V.. ........... I cO-j c- REFERENCE: 196 AaI Foto-Map Book. I; fl I I I I 0 2000 4000 Scale in Feet .:A SITE LOCATION MAP I LA LA COSTA COMMERCIAL COSTA, CALIFORNIA PROJECT NO. DATE' V. F;GURE 1 100170-01 4/2/87 I i LL. - ITF \\ IIT-8 - \:. ) PARCEL\I " \ ..J Al f T75. / R. Ds\MANo 9O \. \ I I I II I I LEGEND T-8 - Approximate location of exploratory test pit 0 so 160 Oaf Fill. Approximate Scale in Feet Tsc Scripps Formation NORTH - Approximate geologic contact TOPSOIL DEPOSITS NOT SHOWN. ALL DIMENSIONS ARE APPROXIMATE. BASE MAP ADAPTED FROM RICK ENGINEERING COMPANY, SAN DIEGO, CALIFORNIA, PARCEL MAP, DATED 1/6/87. I I I I I I SURFACE OF FIRM ,- - EARTh MATERIAL COMPACTED FILL TYPICAL BENCHING / REMOVE UNSUITABLE MATERIAL SEE DETAIL BELOW - INCLINE TOWARD DRAIN DETAIL MMUM 9 FT 3 PER UNEAR FOO 07 APKiOVED FILTER 14ATERIAL NZIMUM 4 DIAMETER APPROVE PERFORATED 'E (PERFORATIONS DOWN) MATERIAL BEDDING. 14 MINIMUM FILTER MATERIAL TO YEET THE FOLLOWWC S1'ECI C!.Ti3N OR APPCVET) UUAL SIEVE SIZE TERCEN'fAGE 1" 100 3/4" 90 - 100 3 /8" 40 - J.00 NO.4 25-40 NO. 30, 5-15 NO. 50 0-7 NO. 200 0-3 APPP.OVEDPIPE TO BE SCHEDULE 40 (,v.c.) OR APPiC.VED IQtL.L. MINIMTJI., CRUSH STRENGIH 1000 psi PIPE )IANETER TO 1IET THE F0LLO!ING CRITERIA, SUBJECT TO FIELD REVIEW BASED ON ACTUAL GECTECH1ICAL CONDITIONS ENCOUNTERED DURING GRADING LENGTH OF RUN PIPE DIAMETER UPPER 500' 4" NEXT 1000' 6" > 1500' 8" TYPICAL CANYON SUBDRAIN DETAIL LA COSTA COMMERCIAL J. LA COSTA, CALIFORNIA PROJECT NO. DATE 100170-01 4/2/87 FIGURE 3 BECHIING DETAL LA COSTA COMMERCIAL LA COSTA, CALIFORNIA PROJECT NO. 100170-01 DATE 4/2/07 FIGURE 4 --------------- FILL SLOPE COMPACTED= FILL - :-- i__--_--_- --- - _'-- ---- -- PROJECTED PLINE lAVA' 1 to 1 mxInwrn 1ru too (it — slope to approved ground REMOVE UNSUITABLE NATURAL MATERIAL GROUND B NCH HEIGHT c BENCH :-kMiN -y (typical) VARIES ----r 2' MIN. L. 15' KEY LOWEST BENCH 1 DEPTH (KEY) n..nn'.*.fl 3 F.T. Von der Abe Company March 24, 1987 Project No. 100170-01 TABLE I SEISMIC PARAMETERS FOR ACTIVE FAULTS MAXIMUM PROBABLE EARTHQUAKE (Functional Basis Earthquake) Maximum Approximate Probable Distance Earthquake Peak **Repeatable From Fault Bedrock High Ground To Site Richter Acceleration Acceleration Fault . (Miles) Magnitude (Gravity) . (Gravity) Coronado Banks 26 6.0 0.10 Elinore 26 . 0.7 . 0.14 San Jacinto 54 7.2 0.07 Rose Canyon* 15 6.0 0.20 0.13 * This fault is considered "pote!aily active's. ** The repeatable high ground acceleration may be taken a 65% of the peak acceleration for sites within 20 miles of the epicenter (after Ploessel and Slosson, 1974, Appendix A, Reference 3). I F.T.Von Der Ahe Company I. I I APPENDIX A March 24, 1987 Project No. 100170-01 References V • Greensfelder, R.W.., 1974, Maximum credible rock acceleration from earth- quakes in California: C.D.M.G. Map Sheet 23. :I . 2. Jennings,. C.W., 1975, Fault map of California: C.D.M.G. Geologic Data Map V Series No. I. V 3• Ploessel, M.R., and Slosson, J.E., 1974, Repeatable high ground accelerations I. from earthquakes, important design criteria: California Geology, V. 27, p.. 195-199. I 4. Tan, S.S., 1986, Landslide hazards in the Encinitas quadrangle, San Diego V V County: C.D.M.G. Open-file report 86-8 LA. V I I I I I I I I I V V V V I I V V V F.T. Von Der AheCornpany March 24, 1987 Project No. 100170-01 1. 0 APPENDIX B • Test Pit Logs SI Li Depth Description I 0-1.5 feet. TOPSOIL: Brown to brown-gray, dry, medium dense CLAYEY SAND (SC), mottled, iron oxide, caliche stringers. 1 1.5-5.0 feet BEDROCK (SCRIPPS FORMATION): Orange-gray, damp, very • dense, SANDSTONE, massive. I Test pit terminated © 5.0 feet. No ground water. No caving. Test pit excavated and backfiiied on 02123/87.. I I 1it1 'jje 0-5.5 feet nLL: Dark brwn t.j yellow-brown, damp, medium dense, I IM e0r Ch rf:ott!ed lens s. 5.5-9.5 feet TJEL;ROCKSCRIPPS FORMATION): Light gray, danp, medium ' dense, SILT' SANDSTONE 9.5-10.0 feet BEDROCK (SCRIPPS FORMATION): Brown-red, damp, hard, CLAYSTONE, callche stringers. 0 I . Test pit terminated at 10.'0 feet No ground water. No caving. • S Test pit excavated and backfilled on 02/23/87. . 0 'V. 5 0 I t- • 5 5 Depth • Descpt1on 5 • 0-2.5 feet FILL: Brown-gray, damp, loose, SANDY GRAVEL (GP). I I I i S 0 • IL I . Depth 0-2.0 feet I I. I , F.T. Von Der Ahe Company I I 2.5-4.5 feet I 4.5-12.5 feet March 24, 1987 Project No. 100170-01 FILL: Black to black-gray, damp, soft, SANDY CLAY (CL), large roots, organic-like odor. BEDROCK (SCRIPPS FORMATION): Gray-brown, damp, medium dense, SILTY SANDSTONE, massive. Test pit terminated at 12.5 feet. No ground water. No caving. Test pit excavated and backfilled on 02123/87. T-4 Depth 0-4.0 feet 4.0-12.0 feet Description TOPSOIL: Orange-brown, moist to. wet, medium dense, SILTY SANDY (SM), roots to 1/4 inch diameter. BEDROCK (SCRIPPS FORMATION): Brown orange, damp, very dense, SILTY SANDSTONE. Test pit terminated at 12.0 feet. No ground water. Nc .cavtng. . . . .' Test Mt excaated t'id DacrIled c' !2.3/8 1'. I 0-2.5 feet I 2.5-8.5 feet 0escrcti on TOPSO!L:, Brown-orange, damp, medium dense, SILTY FINE SAND (SM). BEDROCK (SCRMPS_F'ORMAT!ONJ Gray-orange, damp, very dense, interbedded SANDSTONE and SILTS TONE. Test pit terminated at 8.5 feet. No ground water. No caving. . Test pit excavated and backfilled on 02/23/87. Description TOPSOIL: Brown-orange, damp,, medium dense, SILTY SAND (SM). F.T. Von Der Ahe Company March 24, 1987 Project No. 100170-01 2.0-5.5 feet BEDROCK (SCRIPPS FORMATION): Varicolored blue-gray and yellow brown, moist, very dense, SANDSTONE. 5.5-12.0 feet BEDROCK (SCRIPPS FORMATION) : Gray, damp, very hard, CLAYSTONE. 12.0-13.0 feet BEDROCK (SCRIPPS FORMATION): Orange-brown, damp, very dense, SANDSTONE, fossiliferous below 12.5 feet. Test pit terminated at 13.0 feet. No ground water., No caving. Test pit excavated and backfilled on 02 /23/87. T-7 Depth 01.0 foot 1.0-2.0 feet 3.0-12.0 feet Description TOPSOIL: Brown, dry to damp, loose, SILTY, SAND (SM). TOPSOIL: Brown, damp, medium dense, CLAYEY SAND (SC). BED('Cr( (CPIPPS FORMAT rON) Varicolored dark gray and orange-brown, damp, very dense, interbedded SANDSTONE and SI LTSTONE. Test pit terminated at 12.0 •feet. - No ground ater. No ca'i. '. Test pit excavated and bakfilIed on. C/24/87. - 111 F.T. Von Der Ahe Company March 24, 1987 Project No. 100170-01 APPENDIX C Laboratory Testing Classification Soils were visually and texturally classified in accordance with the Unified Soil Classification System. Soil classifications are indicated on the test pit logs in Ap- pendix B. Direct Shear Tests Direct shear tests were performed on remolded samples in general accordance with ASTM D3080-72 to evaluate the shear strength characteristics of selected materials. The samples, were inundated during shearing to represent adverse field conditions. Results are presented on Figure C-3. xpansion index- Tests T expansion potential of selected materials w&s evaluated in generl accordance the Expansion index Tat, U.B.C. Standard o. 29-2. Specimens ware molded unec a givL compaction energy to approximately 30 percent saturation (plus or ns I oerc.n;. Tie. praciarod 1-inch thick b. 4-inch a;ne.er snecimens were coded to Ryi equivalent 144 pounds per square foot sur.tharge and were inundated with. tao wacer and readings of volumetric swell were made for a period of 24 ours. The results of these tests are presented in the test data. Maximum Dry Density and Optimum Moisture Content Tests The maximum cry density and, optimum moisture content of selected representative soil saroples were evaluated in general accordance with ASTM D1557-78. The re- sults of the tests are summarized on Figure C-3. M 1 F.T.Von Der Ahe Cornpdny. March 24, 1987 I Project No, 100170-01 Field Density Tests Field density tests were performed to evaluate in-place density, in 'general accor- dance with ASTM D1556-82 (Sand Cone method). The, results 'of the field density tests are provided in Figure C-I. Disturbed Samples . I Bulk samples of representative materials were trenches. They were bagged and transported to the obtained from borings and/or laboratory. for testing. - I I I I I 1 I I I I I I I FIELD DENSITY TEST SU:ii'ARY FIGURE C-i In-place In-place Test pit Depth Moisture Dry Density No. (feet) Content (%) (pcf) Remarks T-4 3.0 18.5 87.9 Topsoil T-6 5.0 9.0. 121.3 Bedrock T-7 0.5 13.9. 92.5 Topsoil T-8 4.0 6.2 119.7 Bedrock FIELD DENSITY TEST SUMMARY La Costa Commercial La Costa, California PROJECT NOJ DATE 10010-01 1 3/16/87 FIGURE C-i EXPANSION INDEX TEST RESULTS PERFORMED IN GENERAL ACCORDANCE WITH USC STANDARD 29-2. SAMPLE LOCATION _& DEPTH INITIAL MOISTIJRE (%) COMPACTED DRY DENSITY (PCF) FLUAL MOISTURE (%) VOLUMETRIC SWELL (IN.) vp EA 4SiON INDEX E>'PANSlO'1 POTENTIAL TP-3 @ 2.5' 13.5 96.8 25.3 0.038 . 38 Low TP-6 @ 5.5' 15.8 90.3 34.8 0.089 89 Medium to high MAXiMUM DENSITY TEST RESULTS PERFORMED IN GENERAL ACC ORDANCE WITH ASTM D1557-78. SAS?LE MAXtMJA OPTIMUM LOCATiON SOIL DESCRIPTION DRY DENSITY MOISTURE (PCF) CONT ENT 7 "S @ I Yilc rwn, silty sand. • 115.2 1 14.5 La Costa Commercial La Costa,California PR0JCTNO. DATE 100U0-Q1 3/16/87 FIGURE C-2 MAI ASSUMED PARAMETERS Z = Depth of saturation 3 feet i = Slope Angle 25.6 = Unit Weight of Water = 62.4 pcf Saturated Unit Weight of Sail = 120 pcf 0 = Aparen: Angle of lnernaJ. Fricticn = 34 C = Apparent Cohesion = 250 psf FS = C +c7tan 0 = C c0s2 i tan 0 = 250(120 - 62.4) cos2 26 tan 34 T Z sin i cos i 120 sin 25 cos 26 FS =6 Note: Assumes sandstone derived fill compacted to 90% of the maximum dry density SIJRFICIAL SLOPE STABILITY ANALYSIS LA COSTA COMMERCIAL LA COSTA, PROJECT NO. DATE 100170-01 4/2/87 FIGURE D-1 I I J. Fi ]. L UO8Tc J DAI i F:i 1 r - Ul.JF I ' F I L cC- l I 11 4c1 I S , S I L .-I t I Type .. i 1 / I 'ii, c—jr c cc—il i T'c' Soi 1. T C. ]. SctLtrited or,eion Fric:t ion Pore Fressur N 1 - 'ie Urc:i L tt Unit 41. .[ntrc:.pt (n c1 ' F'reszLtr t:::cnt,nt S ..L.. ). c:- ) . (d&) Fcrm. ± ) Nc. 2 6 S I i 3 Ld I c: c' ;c': D. LA F. 1.J;cci HEiI Technique F& 6=nerstinq irr egular Surf ac es,Has Besn Specified. o !Via! Surfaces Have.Deen C.i'rL.d 10 Surface~:. initiate From Etch Of io Po:ints Equally Spiced Ainng The Ground Surf X 00 f t. and x = 40.00 it. SL -+ 1:-mi. X :. 00 ft and • x = 150.00 ft. Unless Further Limi t ations Wer I mposeci The Minimum Elevali cni At WI.-fich SurfaceExt ends is Y 10,00 +t. 12.00 it. Line Segments Define Each Trial Failure Surf Beuc: WmEed Upon The itc!e Of initiati on, Haz ,Sean Restricted Between r .The Angle he Angles Of And .I .•_0••.; 00 ng Di SPI eyed the - t---Mmst Cri tichl OF Th! trial Failure Sarfazes Examined . -..- re Or-d•zr-e: - Nos t t.:it:icj•I S: et ' Factors Are C1 cuI LecI By The Modified J:nbu Method * * Fai l urO Surface Soec::if led By t2 Coordinate Points Poi nt X-Sur-F Y-Surf c-ft) 1 2000 1000 • 2 32.00 10.32 : 43.99 • 10.07 .7 07 77.60 97,45 33.40 107.63 -9 '.0 i.'-+,,cj SPecif ied Sy 12 Coor yinateF':::tc. No. (t ) 1 . 2 : 7.,87 127 79.86 13.20 89.64 2'i&.. 8 99.97 26.26 9 08.:.4 ::4.8 10 116.45 43.71 7-1. 1 .905 .Failure SL j?C:]. +i.:d By 3.2 Coordinate Point s pmi• : —L r-t • O_ • +t) .1 24.44 12.22 7:6. 12.52 - '-1 72.32 j r, 84.31 1 5.42 9-4..0E 22.38 8 10.1.41. 28.49 9 • 112.79 37.08 1.20.90 . 4_ 93 Li 129.63 54.16 j2 132.89 56.78 2. o:..: Fai lure -f cJ Dy 12 Coordinate Points:. -L...Lrt. ,-•:-•.;-.j- y__'..:.. Failura Surface 8aEi fled By I') Caordi. nE;tc? Points vci -: >-Surf Y-bur1 (f h) (-ft) 16.67 32 S 57.25 10. M 00 16.03 79.14 22.45 90.19 26.64 7 :0.28 03• q4 2 10E.53 42.11 40.1.3 • 124.1 58.87 • 2.082 3-** Fa ilure Seci f I ed By ii. Coordi na te Faints Faint X-8Lt Y-b'urf (ft) (fl:) .1 .I.LI :15.56 43.07 16. 4' 07 16. I 66.93 .14.40 78.83 6. 98 22.5V • - 17 • .119 .76 41. s126.17 51.17 Fail ure Surf ace Specified By . Wordinate Poi nts r::L nt MD (Ft) (ft) 247 :i33 2 38.66 13.44 50.66 14. 05 i. 62.51 15.89 74.43 V.7.30 6 86.27 M 28 7 97.50 -21.50 107. o:. . 30.20 114.27 33.45 10 J.25..71 45.8 .L .L p rcr- r . ._,.j fl 52.96 7 . 12 13./.70 55.57 .2.095 *4 Failure Purface SPec ified By i C;ccrd . n Pc:i ;:t Poi nt :-t.:--f (+t) 15 .56 '2 43M 55.11 :15.90 4 67.07 5 90 :18.29 6 90.98 18.75 7 .100.75 . 25.7:1 1.11.08 :je 9 119.46 40.41 10 127.54 4926 .11 :134.98 5605 :2.i2:: Fail ure S L" +pcc': +2 '.'( :1.:: C:i.c:i-'c: :')ç.:. r'': Point X-Surf ft:.. +t) ]. .: 48.26 10. 71.63 15. Sa S1.61 2:2..52 104.16 30. 7A 92 i.l. i)T.- 1,24.95 42..45 1 I L . 1 C'_i C' I .1 - . .....•. 56.74 2.126 Fai lure Sur face Specif ied y 10 Coordina te Poi nts $t) (ft) .1 31.11 2 42..!.1 15.86 :3 5.,/2 A. 79.13 2.:s...4.... L - - H /.t'I . • • •/ 1.04.81 44.,E3I, CD 5 - -I jF . It. - • 1) I ') 59.45 : i:t A X .1 S F X • ±----------+---------4-----------+--------------------+ ..rz; .00 _L - - .L4 I t GENERAL PROPERTY MAINTENANCE GUIDELINES FOR HOMEOWNERS INTRODUCTION 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 lack of property máinte- nance. It is therefore important for the homeowner to be familiar with some guidelines for maintenance of residential properties and aware of the importance of proper maintenance procedures. Some common causes of erosion problems and shallow slope failures are outlined below: Sxrse and/or improper planting and maintenance of slopes and yards. I.)per maintenance of drainage devices. Over-watering of slopes or yards or diversion of runoff over the slopes. Foot traffic on slopes, which destroys veqetation and increases the poteriLa for erosion. M?INTENANCE GUIDELINES The following maintenance guidelines are provided for the protection of the hcimecwrer's investment and should be utilized throughout the year. Care should be taken that slopes, terraces, berms (ridges at crown of slopes,, and proper lot drainage are not disturbed. Surface drainage should be directed off site by a graded swale (gentle graded ditch) or other appropriate device. In general, roof and yard runoff should be. conducted to either the street or storm drain by appropriate erosion control devices such as graded swales, rain gutters and downspouts, sidewalks, drainage pipes, and ground gutters. Drainage systems should not be altered without professional consultation. I I All drains including gutters and downspouts should be kept clean and unclogged. Terrace drains and gunite ditchs should be kept free of debris to allow proper drainage. The perforrnaneof the drainage system should be periodically inspected. Problems, such as gullying and ponding, should be corrected as soon as possible. Any leakage from pools, waterlines, etc., should be repaired as soon as possible. Animal burrows should be filled since they may cause diversion of surface, runoff, promote accelerated erosion, and may even trigger shallow slope failures. . Slopes should not be altered without professional consultation. Whenever .a homeowner plans a significant topographic modification of the lot or slope, a geotechnical consultant should be contacted. If.plans for modification of cut, fill, or natural slopes within a property are considered, a geotechnical consultant should be contacted. Oversteepening of slopes may result in the need for eensive retaining devices. Undercuttinq of the bottom of a slope rr.y lead to slope instability or'failur• tnd should not be undertaken without .exert consultation. . . If unusual cracking, settling, or soil failure occurs,' the homeowner should consult a geotechnical consultant immediately. i; Cbck :fore and aftr rnaor storm t.o be sure drains, gutters, downspouts, and ditches are .Lear and that vegetation is in-place on slopes. 'Spot seed..any bare areas. Check with a, landscape architect or local nursery for advice. Prepare berms and ditches to drain surface runoff water away from slopes. - 2 - EROSION REDUCTION GUIDELINES Care should be taken to provide ground cover at all times, but particu- larly during the wet winter months. Some suggestions for soil stabilizing ground covers are provided below: Grass may be an inexpensive and effective material for erosion control. It grows quickly and covers the ground completely. To find the best seed mixtures and plants for your area, check with a land- scape architect, local nursery, or the U.S. Department of Agriculture Soil Conservation Service. Mulches hold, soil moisture and provide ground protection from rain damage. They also provide a favorable environment for starting and growing plants. Easily obtained mulches include grass clippings, leaves, sawdust, bark chips, and straw. Commercial application of wood fibers combined with various seeds and fertilizer (hydraulic muLching) are effective in stabilizing sloped areas. Mat.3 Of excelsior, jute netting, and plastic sheets'can'be.effective temiorary covers, but they must be in contact, with the soil and fastened securely to work effectively. . opti qoal of .0.1anA.,ig slopes iS to achieve a dense growth ef getation which includes plants of vary iug root depths) requiring minimum irrigation. A landscape architect an recommend drought tolerant species which may be appropriate for conditions on your property. Plants having shallow root systems and requiring abundant water (many types of ice plant) are poor choices for slope stabilizing ground covers. Is - 3 -