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Home My WebLink AboutCT 72-24; Spanish Village Unit 1 & 2; Soils Report; 1973-05-10,,: ,I pan -,.1, i_. _, ~: ~, ~- BENTON ENGINEERING, INC. *PPLIED SOIL MECHANIC8 - FO”ND*T,ON* 8717 CONYO” COURT 8AN DIEGO. CALIFORNIA oz,,, La Costa Land Company Costa Del Mar Road Carl&ad, California 92008 Attention: Mr. IN fbston SUbjeCti Proiect No. 73-3-l Preliminary Soils C~ Spanish Village Units ament to Proiect No. 70-l l-188 Phase I of Pre-Preliminary Soil Investigation MBD Property, Ranch0 La Costa Dated December 11, 1970) Ranch0 La Costa Carl&d, California Gentlemen: CONCLUSIONS AND RECOMMENDATIONS It is concluded frun the results of field investigations and labamtary tests that: 1. The subsurface conditions within the subject property are generally favorable for the proposed development with same precautions as described in paragraphs 2 to 4, inclusive, that follow. 2. The unfavomble geotechnical features that deserve special attention for the proposed developments are tabulated below: a) Evidence of previous movement of soil mantles was noted to a depth of 16.0 feet (to appmximotely Elevatian 107.0 feet) below the existing ground surface in the area of Boring 2A, and potentially expansive cloy and claystone layers were encountered below 16.0 feet in depth. b) Soft cla\ntone with block carbonaceous moteriols was encountered In some zones below a depth of 17.0 feet in the area of Boring 3 01 below Elevation 113.0 feet. c) Ground woty was found at a depth of 9.6~~feet below the existing ground surface or below Elevation 44.4 feet in the areo of Boring 6 located at the southwest corner of the,site. Cov- ing of the boring was noted below the water table. Project No. 73-3-16BC La Costa Land Company -2- Moy 10, 1973 4 A previous londslided zone was found between the depths of 25.5 and 30.0 feet in the oreo of Boring 10 or approximately between Elevations 161.5 and 157.0 feet. e) lane was noted between the depths of 4.0 and 4.7 feet, or between Another%at Boring 11. Elevations 173.0 and f) A lands1 id-e was encountemd on top of a clay horizon at Elevation 87.5 feet in Borlng 1 of Spanish Village West, 7 Acres Site Project under Project No. 73-3-9BC. The boring locations of this project ore also shown an Drawing No. 1, in the southwest corner of the site. This clay horizon and slip zone will be exposed by the grade excavation along most of the street from El Camino Real eastward to the first road intersection. The out of slope 31’ and should be either buttressed or excavated at a flatt downward , 9) A &j&de 70-a yvas encountered on top of a clay horizon at Elevation 86.0 feet ‘” Boring 2 Of Spanish Village West, 7 Acres Site Project under Project No. 73-3-9&,; This slip plane dips 29’ out of slope. Care should be taken to lay these siopes back if the slip plane ond underlying clays are encountered during gmding. h) Wherever the chamcteristic La Costa green clays are encountered durlng grading, they should be laid back to slopes of 3:l horizontal to vertical or fiattec. We anticipate that they will be found below Elevation 1 IO.0 feet in the north portion, below Elevation 90.0 feet in the southwest area, below Elevation 120.0 feet in the central orea, and below Elevation 160.0 feet in the eastern area. 3. Present plans call for excavations thrcugh the problematic zones of (a), (b), (d), (e), (f), (g) and (h) described above. It is themfom recommended the excavations in these areas 3 be kept to a minimum height at o slope fur than 3 hortpptpl to 1 vertical. These unstable * zones should be carefully examined during gmding opemtions to ascertain whether stabilised fills or buttress fills are needed to correct the unstable conditions. If possible, grading should be planned to avoid constructing exposed cut slopes in these unstable zones. 4. Present plans toll for fills up to approximately 7.0 feet in thickness in the problem- atic zone of (c) described in pamgraph 2. Because of the presence of the ground water table and caving in the boring, buildings with high concentrated column loads or high rise buildings should be avoided in Boring 6 area, unless special foundations such OS driven piles ore used. 5. The favomble geotechnical conditions of the subject property am that the soil mantles can be excavated by conventional equipment without msortlng to extm heavy excavatien equipment. 6. in estimates of earthwork quantities, a shrinkage factor of 3 percent may be used for the excavated soils below the topsoil and up to 25 percent in the loose topsoil layers. In that the upper 2 feet of soils encwntemd in all the borings drilled for this pmiect are loose, settlements of the upper soils up to 6 inches may also be taken into account for eorthwork estimates. 7. The excavated gmnular type of soils such as silty sand, slightly silty sand, clayey sand and fine to medium sand may be used for structuml support both as natural soils and OS can- pocted filled ground. The fine-gmined types of soils such as claystone, clay, silty clay, and clayey silt should not be used for structuml support because’ of their expansive potentials os tndi- coted by the results of loboratory tests and our past experience with the flne-gmined types of sails in the Lo Costa area, unless special design precautions are used for footings, and concrete slabs. Project No. 73-3-16BC La Costa Land Campany -3- May 10,’ 1973 a. * When used as compacted fill materiol,&e fine-grained soils should be placed no closer to exposed slopes then 20 fset, for reasons of stability of fill slpoes. When these types of soils are placed in approved omas, (i.e., 20 feet or more inside of fill slopes), either of the two following altemotive procedures may be used. A) Place these soils at depths of 3 feet or more below finish grade, in which case no special design precautions will be needed. W If such solls ore placed within the upper 3 feet below final grade, the special design precouticns presented in the attached Appendix C shwld be adopted. if, during groding, these expansive soils ore found to exist within the upper 3 feet below finished grade in cut omas, either of the two options presented above is acceptable. Alter- native (A) can be effected by over-excavating these soils to a depth of 3 feet and replacing the excavated sells with properly ccmpacted nonexpansive soils. In any case, it is recommended that all lots be inspected at the time of grading in order to determine those lots which contain poten- tially expansive clay rolls within the upper 3 feet below grade; in some cases it may be necessary to hand-auger 3 feet deep holes in order to make this determination. 9. A one-foot wide continuous footing placed one foot below the proposed,finished grades of both compacted filled ground and naturol ground, may be designed far a safe allowable bearing value of 1658 pounds per square foot. This value is applicable to both fine-gmined type and granular type of soils. The settlement of a one foot wide continuous footing placed as recom- mended and loaded to 1658 pounds per square foot is estimated to be less than l/4 inch. 10. When bedding plane failures are not involved, cut slopes may be made safely up to the following maximum heights with adequate factors of safety: Main Soil Type In Cut Slope Fine-gmined soils Slope Gradient Horirontol to Vertical 2 :l 3 :l 4:l ’ Safe Maximum Heights in Feet Case (A) Cme (B) 23 35 19 51H 26 Gmnulor soils 1.5:1 30 2 :l 54 j Case (A) applies to the excavations made through a relatively integrated soil mass that contains few or none of the conspicuouspmvicusly-described sliding planes. if excavations am ta be made through the problematic zones as described in paragraph 2 of this mport, a cut slope 3 horizontal to 1 verticoi or flatter should be used. Under this condition Case (B) would apply. 11. Compacted fill slopes thot am mode of the excavated soils compacted to at least 90 percent of maximum dry density obtained by the A.S.T.M. D 1557-70 method of compactian may be safely ccnstructed to the maximum heights presented below, with adequate factors of safety: BENTON ENGINEERING. INC. Pmiect No. 733-16BC La Costa Land Company Moy 10, .1973 Fill Slope Recommended Maximum Horizontal to Vertical Heights in Feet 1.5:1 38 2 :l 66 2.5:1 154 - ? It is assumed that the excavated fine-gmined soils will be placed at least 20 feet or morefram ony compacted fill slope ond that grading operations will be conducted under contin- uous engineering inspection in accordance with the applicable sections of the ottached Appendix AA, entitled “Standard Specifications for the Placement of Compacted Filled Grwnd.” 12. The mcommended maximum heights of both cut slopes and compacted fill slopes ore predicated upon the assumption that proper erosion cantml and drainage devices will be pro- vided at the tops of slopes in order to pmvent excess surface water frcm sheeting aver the slopes. 13. Residential buildings may be ccnstructed partly on cut and partly on compacted filled ground provided the load-settlement chamcteristics of the bearing soils are comparable. 14. If any soil types ore encountered during grading apemtions that were not tested in this investigation, additional labomtory testr should be conducted in order to determine the physical chamcteristics and engineering behaviour of the soils. Supplementary reports and recom- mendations will then become a part of this report. 15. A mport of a~geological investigation conducted at this site will be forwarded in the near future. Respectfully submitted, BENTON ENGINEERING, INC. By ,-2f /y--,...- S. H. Shu, Civil Engineer Reviewed by A M. V. Pothier, Civil Engineer Chief Engineer . Distr: (4) Addressee (1) Attention: Mr. Bab Stork (2) Rick Engineering, San Diego Attention: Mr. Smn Gaines LIENTON ENGINEERING. INC. SHS/MVP/ew Project No. 73-3-16BC La Costa Land Company -5- May 10, 1973 DISCUSSION A preliminary soils investigation has been completed on the subiect property, known as Spanish Viltoge Units 1 and 2 and located southerly of La Costa Avenue and easterly of El Camino Real in Carlsbad, San Diego Cwnty, California. This repert is intended to serve as e supplement to a limited soil investigation undertaken pmviously by our firm under Project No. 70-11-188 with a report dated December 11, 1970 entitled “Phase 1, Pre-Preliminary Soils Investigation, MBD Property, Ranch0 La Casta, San Diego County, California.” The obiectlves of this investigation were ta study the geneml subsurface conditions within the subject property that were not previwsly investigated, to identify potentially problematic or hmardcus areas to the proposed developments, and to present appropriate soil parameters for preparing gmding plans and foundation design. The geneml topography of the areo may be described as gently tolling ta steep sloping termin. A high ridge extends in an east-west direction in the north centml portion of the site that has a I imited run-off to the north, and a WI Iey In the southern portion dim& the major dminage to the west. According to the “Soil Map” prepamd by the U. S. Department of Agriculture, the upper soils in the area am described as Huerhuerto fine sandy loam, Carl&ad lwmy fine sand, Las Flams loamy fine sand, and Botello loamy sand. The soils encwntered in both investigatiw consisted primarily of slightly silty fine to medium sand, fine to medium sand, silty very fine to fine sand, slightly silty fine sand, very fine sandy silt, clayey fine sand, fine sandy clay, slightly clayey fine sand, clay, silty clay and clayey very fine to fine sand. Field Investlgatian A total of fwrteen borings were drilled with a truck-mounted rotary bucket-type drill rig at the approximate locations shown an the attached Drawing No. 1, entitled “Location of Test Borings.” The borings were drilled ta depths of 11 to 55 feet below the existing ground surface. A contin- uous log of the soils encountered in the borings was recorded at the time of drilling and 1s shown In detail on Drawing Nos. 2 to 28, inclusive, each entitled “Summary Sheet.” Also shown on Drawing No. 1 om-seveml locations of borings mode adiacent to the sub/ect property in order to provide cross-sections of the subsurface conditions of the adjacent areas. The soils were visually classified by field identification procedures in accordaice with the Unifled Soil Classification Chart. A simplified description of this classificatian system is presented in the attached Appendix A at the end of this report. Undisturbed samples were obtained at frequent intervals in the soils ahead of the drilling. The drop weights used for driving the sampling tube into the soils were the “Kelly” bar of the drill rig which weigh 1623 pounds and 22OG pounds, and the average drop was 12 inches. The general procedures used in field sampling am described under “Sampling” in Appendix 8. BENTON ENGINEERING. INC. Project No. 73-3-16BC La Cesta Land Campany 4- May 10, 1973 Laboratory Tests Labomtery tests warn performed on selected undisturbed samples of the soils in order to determine the dry density and moisture content. They ore presented on Drawing Nos. 8, 10, 12, 13, 14 and 16 to 28, inclusive. Consolklation tesk were performed an repmsentativc samples obtained in the proposed filled ground ama and in the representative excavated soils that might be used for ccm- pactd fills in order to determine the load-settlement chamcterittlcs of these soils. The results of these tak ore pmsented on Drewing Nos. 29 to 31, inclusive, each entitled “Consolidation Curves.” In addition to the above labomtory tesk, expansion tesk were performed on o representative clay- stone sample and some representative excavated soils to determine their volumetric change character- istics with change in meisture content. The mcorded expansions of the samples ore presented as follews: Percent Expansion Percent Expansion Under Unit Load of Under Unlt Load of Depth of 150 Pounds per Square 500 Pwnds per Square Boring Sample Sample, Soil Foot from Air Dry Foot from Air Dry No. No. in Feet Description to Saturation to Saturation 3 6 26.0 Claystone 8. kl2 4.0 -~,S;D Silty fine to medium sand 11 l Bog1 3.0- 4.0 Alternoting silty fine sand ond clayey fine sand 11 * kg3 25.0 - 26.0 Clayey silt 5.75 1.78 3.01 2.39 l Remolded to 92 percent of maximum dry density. The geneml pracedums used for the above iabomtory tesk are described briefly in Appendix 8. Compaction tesk were performed on representative samples of the soils to be excavated to estoblish compaction criteria. The soils were tested according to the A.S.T.M. D 1557-70 method of compaction which uses 25 blows of a 10 pound rammer dropping 18 inches on each of 5 layers in a 4 inch diameter l/30 cubic foot mold. The msul k of the tesk ore presented as follows: Maximum Optimum Mois- Bering Bag Depth Sol1 Dry Density turn Content No. Sample in Feet Description Ib/cu ft %drywt a 2 4.0- 5.0 Silty fyne to medium sand 119.2 11.4 11 1 3.0- 4.0 Alternating silty fine sand 114.3 14.0 and clayey fine sand 11 3 25.0-26.0 Clayey silt 113.4 15.1 12 1 5.0- 6.0 Silty fine to mediun sand 114.0 13.6 12 2 26.0-27.0 Silty fine sand 114.0 11.5 BENTON ENGINEERINO. INC Prejeet No. 73-3-16BC -a- May 10, 1973 La Cesta Lond Company Mechaniwi analysis tesk were performed on representative samples in accordance with A.S.T.M. D 422-61T and the msuik are presented in the following tabulation: U.S. Sieve Size l/2 Inch No. 4 No. 10 No. 30 No. 40 No. 60 No. 100 No. 200 Soil Clossifii Boring 8 Bag2 Depth: 4.0-5.0’ Boring 11 Boring 11 ‘%I kJ 3 Depth: Depth: 3.0-4.0’ 25.0-26.0 Percent Finer by Weight 100.0 99.1 96.6 89.1 2.62 23:6 100.0 99.9 100.0 98.4 99.9 96.7 98.4 95.7 97.9 92.4 95.6 77.0 89.4 33.8 47.6 Silty flne Silty fine Clayey very to medium sand fine sand Boring 12 Boring 12 Bag 1 kg2 Depth: Depth: 5.0-6.0’ 26.0-29.0’ 100.0 100.0 99.9 99.9 98.5 99.1 95.0 98.1 62.5 85.9 31.0 49.1 16.2 19.6 Silty ftne to medlum sand Silty fine sand In order better to classify the finer gmined soils, Atterberg Limit tesk were performed on selected samples in accordance with A.S.T.M. Designations D 423-61T and D 424-59. The results of the tesk and the final group symbols ore presented as follows: Boring Sample Depth Soil Liquid Plastic Plasticity Grwp No. No. in Feet Description Limit Limit index Symbol 2A 6 25.5-26.0 Cloy 56 18 CH 3 kl4 21.0-22.0 Clay i: 22 2 CH I3 Bag2 4.0- 5.0 Silty tTne to 21 10 CL * medium sand with clay binder 11 b3 1 3.0- 4.0 Alternating 37 20 17 CL l ,silty fine sand and clayey fine sond 11 kg3 25.0-26.0 Clayey very 36 17 19 CL * fine sand * Minus No. 40 sieve sample that contains clay binder BENTON ENGINEERING. INC. Project No. 73-3-16BC La Costa Lond Company -8- May 10, 1973 Direct shear tests were performed on selected loose soil samples remolded to 90 percent of maximum dry density ond on selected undisturbed scmples thot were all saturated and drained prior to testing. The muik of these tests are presented below: (A) Undisburbed Samples Boring 8, Sample 2 Depth: I1 .O feet Boring 10, Sample 1 Depth: 3.0 feet Boring 11, Sample 5 Depth: 25.0 Feet Boring 13, Sample 5 Depth: 25.0 feat (B) Remolded Sample Boring 8, Bog Sample 2 Depth: 4.0 to 5.0 feet Normal Load in klps/sq ft 0.5 1.23 1.0 1.53 2.0 3.78 0.5 100 2.0 0.5 1.0 2.0 0.5 2.27 1.0 1.92 2c.o 3.15 0.5 0.72 1.0 1.02 2.0 1.67 Moxjmum Angle of Shear Internal Load Friction ‘Wsq ff Degmes 31.0 930 1.01 1.54 2.23 35.0 660 4.59 4.07 4.98 15.0 1900 30.0 1330 32.0 380 Apparent Cohesion Ib/sq ft Using the lower values of internal angle of friction and apporent cohesion, and the Terzaghi Formula for local shear failum, the sofe allowable beoring pressures for both compacted filled ground and natural ground are determined on the following page. BENTON ENGINEERING. INC, Project No. 73-3-16BC Lo Costa Land Company -9- May 10, 1973 Local Shear Formula: Q’d = Z/3 C W’, + y Df Wq + Y BN’y Assumptions: (1) Continuous footing 1 foot wide = 28 (2) Depth of footing = 1 foot = Df Undisturbed Natural Soils Q, = 15 Degrees C =660 Ib/sq ft y = 115 Ib/cu ft Nlc = 10 Nlq =4 N’y = 2 Q’,-j = (2/3 x 660 x 10) + (115 x 1 x 4) + (I 15 x 0.5 x 2) = 4975 Ib,‘sq ft Q’,j SCife = Q’d $3 (Factor of Safety) = 1658 Ib/sq ft Fill SoilsCompacted to 90 Percent of Maximum Dry Density Q = 32 Degrees C = 380 Ib/sq ft Y = 116 Ib,‘cu ft Nlc= 21 N’q = 11 N’y = 7 Q’d = (2/3 x 380 x 21) + (116 xlxll)+(ll6x0.5x7)=7OO2ib/sqft ” Q’d Safe = Q’d r3 (Factor of Safety) = 2334 Ib/sq ft BENTON ENGINEERING. INC. , , z ml :! 4- . -0 SUMMARY SHEET z 2: i;r i 3; 2sz BORING NO. 1 5 ELEVATION c Brown, Dry, Medium Firm, Very Cloy Bindor Slightly Moist, Vary Firm Moist Brown, Moist, Very Firm, Slight Cloy Binder iLIGHTLY SILTY :INE TO MEDIUM SAND I FINE TO MEDIUM SAND (Merges) ALTERNATING -AYERS OF SILTY JERY FINE TO ?NE SAND AND iLIGHTLY SILTY FINE SAND - iti i? “E p - - 7.4 - 5.7 !4.d - - - - Continued on Drawing No. 3 0 - Indicates Undisturbed Drive Sample Cl - Indicates Loose Bog Sample 1 I * - The elevotions presented herein were detormincd by interpolating between the contour lines shown on a plan furnished by Rick Engineering Company. PROJECT NO. 7%3-16BC I RENTON ENGINEERING, INC. I DRAWING NO. 2 i ! . t ’ _ , i ,a : 0’; *d SUMMARY SHEET ; ES “2% ; 2; ,osz BORING NO..-.J&mt.) : Brown, Moist, Very Firm, Slight Cloy Binder ALTERNATING .AYERS OF SILTY /ERY FINE TO FINE SAND AND iLIGHTLY SILTY FINE SAND iO.0 l0.C 15 A I1 .( 1 I PROJECT NO. DRAWING NO. 73-3-16BC RENTON ENGINEERING, INC. 3 t Us 5 p’r’ Ia; SUMMARY SHEET x ZL 5;s r 2; 51ci2 BORING NO.-L&anl.) : B! I 1 3 Brown, Moist, Vary Firm, . 18 I9 aht Cloy Binder- Few Siltstone ond Cloyey Si I tstone Lenses 12- 13- 14- 15: @ l6- i7- i8- IP- ,:@ il- i2. i3- 4- ;&I Brown, Moist, Very Firm, Cemented, Few Shells Light Brown and Light Gmy, Moist, Very Firm ALTERNATING LAYERS OF SILTY /ERY FINE TO :INE SAND AND SLIGHTLY SILTY FINE SAND SANDSTONE SILTY VERY FINE TO FINE SAND 4ND SLIGHTLY SILTY FINE SAND - 5 ;i! 5: IlIE iIt 0 - 54.! 67.1 46.C 12 , 1 - WI g; :c - - - - - - 1 I PROJECT NO. 7%3-16BC BENTON ENGINEERING, INC. I DRAWING NO. 4 z ,a :! p’;: *d SUMMARY SHEET ; SE ‘2r 2 z; 2r;z BORING NO. 2 z ELEVATION 155' Yellow-brown Light Groy - '. ., 7 .,", j@g :. yy@j Light Groy, Moist, Very Firm @jj Light Groy, Moist, Very Firm SLIGHTLY SILTY FINE TO MEDIUM SAND ALTERNATING LAYERS OF SLIGHTLY SILTY FINE SAND AND SILTY VERY FINE TO FINE SAND ALTERNATING LAYERS OF SLIGHTLY SILTY FINE SAND, iiLTY VERY FINE TO FINE SAND, ilLT AND VERY FINE SANDY SILT SILTY VERY INE TO FINE SAND Continued on Drawing No. 6 - 9. ?.i PROJECT NO. 73-3-16BC RENTON ENGINEERING, INC. DRAWING NO. 5 SUMMARY SHEET BORING NO.i)(Cont-) Light Groy, Moist, Very Firm Groy, Dry, Very Firm, Lime Cemented SILTY VERY FINE TO FINE SAND j9.t i0.t 4.5 SANDSTONE Could not excavate sandstone with drill rig. ;a ig Y 1 BENTON ENGINEERING, INC. DRAWING NO. 6 C LI : 1 : J i 1 c D r 4 c -I .i 3 = ,I 5 i: . -m SUMMARY SHEET e ES 13% t 2,’ 26% BORING NO. 2A E ELEVATION 123’ Yellow-brown, Moist 9- Lenses of Brownish-gray Clayey o- e Sand and Pockets of 1:@ 2- Yellow-brown, Moist, Medium 3- 4- 5 6-O Chunks of Cemented Fine Sond and Pockets of 7- 8- 9- C\s;lov Surface Dies 23*to N 63% = Olive-gmy, Moist, Very Firm CLAYEY FINE SAND (Merges) FINE SANDY CLAY (Merges) CLAYEY FINE SAND SLIGHTLY CLAYEY FINE SAND SILTY VERY FINE TO FINE SAND CLAY CLAYSTONE /- 9 .! - - 1 Contfnued on Drowing No. 8 PROJECT NO. RENTON ENGINEERING, INC. DRAWING NO. 73-3-16BC 7 . t : . ! 4 z z 1 1 z 1 z ! E E 3 I I I I I I . 5- :( :6 7- 8- 9- (> '1 I( 2- 3- 4- 5- QC . . ..a- *d SUMMARY SHEET ;:r .u’* BORING NO.ant.) I 1 Olive-gray, Moist, Very Firm CLAYSTONE -2! 6’ 6” *‘ SLIGHTLY SILTY FINE TO MEDIUM SAND Light Gray, Slightly Moist, Very Firm, Scattered Coarse - Olive-gray, Moist, Very Firm = Dips 9“ to SE - - - 19. /’ i9.c '0.C 3 Olive-gray and Orange-brown Light Red-brown With Yellow- Few Small Pockets of Silty Fine Sand and Gypsum Crystals Merges to Softer Claystone CLAYSTONE - jlLTY VERY FINE TO FINE’SAND Light Gray With Yellow-brown and Rust-brown, Slightly Moist, ! 4.6 - - - I EC1 NO. 3-16BC RENTON ENGINEERING, INC. DRAWING No. 8 = ma E 0’;: “d SUMMARY SHEET 2 ES iz?s r $2 2GZ BORING NO.A,Le r; ELEVATION 130’ Groy-brown, Slightly Moist, Slightly Porous 7- 8- 9 Olive-gray, Red-brawn and Yellow-brown, Moist, Vary Light Red-brown With Yellow- brown, Moist, Very Firm, Soft Black Carbonaceous Material in Some Zones and Yellow-brown Streaks JLTY VERY FINE ro FINE SAND S 1 \ S v S SI , CLAYEY FINE SAND /ERY FINE ANDY CLAY {ITH VERY FINE iANDY SILT AND ILTY VERY FINE SAND SILTY CLAY CLAYSTONE - c at ti :E ft a - 1 .A 9.; - .r - 3.7 - i EI I?; !=a ,0* =a - - - Et pi ;: s - - - - - - - 1 I Continued on Drawing No. 10 PROJECT NO. RENTON ENGINEERING, INC. DRAWING NO. 73-3-16K 9 L s . . t c 0 r : : . c. BORING NO.-?&Ft-) Yellow-brown Streoks, Moist, inner With Increase Continued on Drawing No. 11 - Eti ES => :2 aa l- I ! : ;i ; I I b- I- 5- 5-c 7- l- ?- 3- I-( SUMMARY SHEET BORING NO.at.1 ‘ CLAYSTONE ENGINEERING, INC. SUMMARY SHEET BORING NO.4 ELEVATION la’ my-brown, !:@ I- I:@ i- i- m 1- ?- ::o Gmy-brown, Slightly Moist, SILTY VERY FINE TO FINE SAND - Brown, Moist, Firm . . CLAYEY VERY FINE TO FINE SAND IOJECT NO. 73-3-16BC RENTON ENGINEERING, 6.5 6 .f - - In+ =3 2, urn 6C =1 - 7.1 - INC. DRAWING NO. 12 t 5 . 4 : (: , , < 4 ; . rg Er ME ik z ,I I r 2;: *mi SUMMARY SHEET ; LS ! : t / c i ;zr zg Y BORING NO. 5 ! ” ,un : ELEVATION & 8 :, :, : : y.;.:.).:{,:. Light Gmy-brown, ,:a$ \Pomus Dry, Loose S ILTY VERY FINE 1 ++\Flllll TO FINE SAND - - ) ;/: ;: ,. .“:::“‘. . Light Brown, Dry, Firm JLTY VERY FINE 6.5 . . 4 :O FINE SAND . . 4 4 v - .: .: c WITH CLAYEY 3- :,:, :,:, 1 . . . . . . . 4-E JEfK~fEi-F / :,::..::i>.:-: Light Brown, Dry, Firm, 4.9 4.4 38.1 -El . . ..~ ilLTY VERY FINE - Small Chunks of Claystone . 1 r0 FINE SAND 5- . I -\ NITH CLAYEY . . . . __ Moist . . . . \ /ERY FINE TO .,~, 6- ::._.: : f :INE SAND AND ‘.‘, ‘.‘, 7:@ s iLIGHTLY SILTY . -\ /ERY FINE TO 14.6 - . . . . . . - Gmy-brown, Moist, Very Firm FINE SAND / 8- . CLAYEY . 9- FINE SAND . . . . 0-g . . . . . 16.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- . . - A CR !OJECT NO. !OJECT NO. 7 ‘3-3- 16BC ‘3-3- 16BC I BENTON BENTON ENGINEERING, INC. ENGINEERING, INC. I DRAWING NO. DRAWING NO. 13 13 .-.-. ! ,.. ‘- 7 8; 1 [ L I 1 I i i E i, ! ; > ,b 3 I; :t ,’ :: / ; / I ii i.8 ; ) I ~....Le.. . ,,--,,, .A,* -.,,, -_, -, SILTY VEKY FINE c c 2 A I i t : c I c o( r 2 c = 5 -r .IL c E v: Light Brown, Dry, l.oose Mcdium‘Firm - --I_ Light Brown, Dry, Firm, &w/ Smoll Clwnks ol: OlivwO’..w Cloystonc owl rockr:ts nf Finn to Medium Sand; Some Zrwes Slightly Ccm,ontad, S!igh+ Porous --,. Light P;oc-n and Grey-hrotrm, Moist, Medium Loozf AL-..- -. Gray-brown, Moist, Medium LOOSl? TO FINE SAND 6.’ il.4 4. - 12.t No No - I’ i SLIGHTLY,SILTY VERY FINE TO FINE SAND ,, ,, :,,, ,i’ - 0.8 0.8 ,,‘, “: SLIGHTLY ‘~ SILTY FINE TO MEDIUM SAND -- Very Moist -.. Gray-brcwn With I,ight Brown,, ,~ Saturated ,. pi’, ,,,.. / ‘j -i / ,~’ I !I .I , C’ ~. 7,: ,, ,: I.. “8 ,.,,- “‘T mU-“,,. - e,.--.,m ,,,.. i,n~ .,., iW.2JCr:1 A$:). --.m-rrl”r~r~.-ru.-- t w.-“““-.“l~*.u.-.-~M.” ..nsd, I.,, I ./I, .I”~” ,... .’ I 73--3-16BC p” ..<$,;‘y#.* E:%!MEc~iho&, p;1c. ‘. ..a se.*>, ,.-I’ I, ee4,,I-N,....- ., _. ..I._ ,- ,.,),.,,,, Z...i./ .I.I . .._ ,_, j_l,.~ *,r.& ,., ,_ . i Gt?,q,“‘fi~j P’ c ; 14 i! _. ,_~~ i, mm.- --,a’~ a**“. ,~.-- ^-., ,_-. 1~ L : . : 1 I : (I , < < I ; 7 I ‘ u i 4 k ,I Y ‘r’ . *m ; “cr ti- c l > 03s : nz a”- 0 SUMMARY ,$HEET BORING NO.7 ELEVATION 134’ Light Brown, Dry, Laase ;iiLm Very Firm Light Yellow-brown and Gray-brown, Moist Lightly Cemented @j Mars Cemented With Increase 7- a- 9- p-0 2- 3- 4- 5- 6- 7. -El B- ?- -I in Depth With Intorboddod Layers of Rod-brawn Fine Sandy Silt SILTY VERY FINE TO FINE SAND . . . . . 3- b . . . . . Gmy, Moist, Very Firm, :LAYEY VERY FINE \ Cemented f0 FINE SAND , - - 6NGINEERING, INC. DRAWING NO. 15 cy oe r! s ! = .- > 5 6 a v: I c ; c c PROJECT ND. 7%3-16BC SUMMARY SHEET BORING NO. 8 ELEVATION247.0’ Dclrk brawn, Moist, Loose, Rot Porous, Tapsall, Seashells ,Scathmd On Surface Orange-brawn, Slightly Maisl Firm,Slightly Micaceaus ut Brow Light Brawn T”, Light Gray, Slightly Moist, Very Finn, Clc Binder, Slightly Micaceaus Slightly Moist Ta Moist, Micacoaus i Inch Highly Ceniented And Ialcamaus Zone Cantinl CLAYEY FINE TO MEDIUM SAND (M-ernes) , SILTY FINE TO MEDIUM SAND an Drawing No. 17 $5.1 j0.t r.6 o- Indicates Laase Bag Sample O- Indicates Undisturbed Drive Sample * - Elevations Shown Wem Obtained From The Tentctivo Map and Specific Plan Pmpamd by glck Enginesring of Carlsbad, Califamla Which is Entitled Carl&d Trcct 72-24, Spanish Village at La Casta, Units 1 and 2, and dated July 20, 1972. DRAWING ND. BENTON ENGINEERING, INC. 16 SUMMARY SHEET BORING No. 8 (Cant) Firm, Clay Binder, Micaceaus 3- 4- 5- 6. 7. 8- 9. IO 11. 121 13 14 15 - SUMMARY SHEET BORING NO. 9 ELEVATION 200.0’ hlte To Light Gray To Light Brawn, Slightly Moist, Very Firm, Mica+xaus, Raatleh, Clay Filled Fmctums LAYEY FINE TO IEDIUM SAND , SILTY FINE TO MEDIUM SAND - > UC 5% St WY > & 0 - 17.4 Lt.0 7.8 1 - ;i E. EC >I4 Ed - - 03. 10. 10. 96. - - - - PROJECT NO. I DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 18 SUMMARY SHEET BORING NO. 10 ELEVATION_187 _ 0’ Brown To Dark Brown, Moist, Loose, Porous, Rook, Topsoil, Lenses of Clayey Fine To Mediu MEDIUM SAND To Medium Sand ALTERNATING WITH LAYERS OF SILTY FINE TO xed Orange, Yellow and Light ray, Slightly Moist, Micaceau - ?i. Kk 3 YY >’ & 0 - - 1.0 - Il.4 W.0 - - i8.2 - 15.0 / 1 1 0.3 - 7.1 9.2 - - 15.0 - 19.6 - gi IJI =5 iq z? 0 - - 37.7 1O.f 14.1 - 12.t - 07.f - “0; Y $d wt& i5Gi5 :z - - - - - - - - - - - PROJECT NO. 73-3-16BC Continued on Drawing No. 20 DRAWING NO. BENTON ENGINEERING, INC. 19 c a c J . . A , , E : . 2 .! I 4’ , 4 5 !? f !i 1 Z 3 5 v) I 0 n 0 u a i z “s ! wpc z FA f&i EG I 29: SUMMARY SHEET St Z$ iilj” OlTZ I-,, BORING NO. IO (Cant) fire 92, 22 YY Lyz”LL isq A2 >’ i& “8:: gkl tizr od ;z 0 I Brown To Light Brown and Gray-brown, Moist, Vary Firm, Micaceous Brown,Oronge and Yellow l ry Moist To Sotumted,Soft To CLAYEY SILT Firm,Landslide Zone, Fractures in 1 MIXED WITH Severn1 Directions: At 25.5 Feet I r, AVFV FI NF I South 80 Degrees E-t 1 Foot Layer of l/4 Inch Ight Brown To Brown and Light Groy Mixed, Moist To Very CLAYEY FINE 1 I I I I MoiskVery Firm,Thinbedded Dips - 5 Dagrees,Clay Seams Fine Sand I 1 PROJECT NO. I I DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 20 SUMMARY SHEET BORING NO. 11 ELEVATION 17.0’ Brawn, Moirt,Lao+ Porous, CLAYEY FINE TO Roots, Topsoli MEDIUM SAND 1 Brown To . . . . . Orange-brawn, Moist, CLAYEY \ Old Slip Plane Dips 19 Dear&/ FINE .-*.,I3 Pods I and Streaks of Orange and SILTY FINE Yeliow,Siightiy Moist,Very Firm SAND 1 v m Mkxceour,Silghtiy Poraw, ALTERNATING kmtiots on Fractures,Ciay ITH LAYERS OF a!\ Filled Fractures FINE SAND AND, CLAYEY FINE SAND 1 Slip Plane Dipping 45 Degrees North 15 Degrees West, l/8 Inch Brawn Clay -. I ,- Light Yellow-Gray To Light SLIGHTLY SILTY Yellow-brown, Slightly ~otst, TO SILTY FINE Very Compact TO MEDlUM.SAND Orange,Bruwn and Gray, SILTY FINE TO MEDIUM #SAND i 79.2 15.6 107. 125.4 10.6313.1 I I Light Brown To Light Gray, 1 FINE SANDY 17- 18- l’,Ici !I- 16- . . . . - Light Bmwn,Slightiy Moist TO Motst,Very Firm,Lensee of Silty . . . . CLAYEY Fine Send, Micaceous, FINE . With Pink Clay SAND / 107.8 Slightly Moist,Very 3 SILTY Firm, Mlcaceous FINE SAND Continued on Drawing No. 22 12.2 111, -- d - PROJECT NO. DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 21 n oi Y .- .c 1 = c f I c I c < .ight Orange-brown To Brown With Orange Streaks and Pods, Moist, Very Firm, Micoceous -. 22 23- 4- Y5I. I 261° 27- 28- :a 361- 32- 33 34 Dark Orange-brown, Gray, and Dark Orange-brown, Gray, and Red-brown, Slightly Moist,Very Red-brown, Slightly Moist,Very Firm, Lenses of Silty Fine Sand, Occasional Lenses of Clayey Fine Sand inue d on Drawing No. 24 JLTY FINE SANC :l.AYEY VERY FINE SAND iLIGHTLY SILTY INE TO MEDIUM SAND 66.0 56.1 36.4 94.6 I I I PROJECT NO. DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 22 :: z % = 5 f ,- !i n I 0 8 0 : 2 i ?.i. SUMMARY SHEET =lL BORING NO. 11 (tit) 22 $5 & ,. SLIGHTLY SILTY FINE TO MEDIUM SAND Q73.9 PROJECT NO. 73-3-16BC I BENTON ENGINEERING, INC. I ORAWNG NO, 23 ZlY!?I .!z:! SUMMARY SHEET GORING NO. l’l ELEVATION 235.0’ 4 a ,Orange-brown Orange-red-brown, Moist, Medium Firm, Pods of Fine Sandy Clay, Porous, Roots C 0 Light Groy To Light Brown With Streaks of Orange,Slightly El Moist, Very Firm, Micaceous, Lenses of Slightly Silty Fine To Medium Sand, Brown Clay Fll led Frocturar 1: .I; Lenses of Silty Fine Sand, Occasional Clay Pods 1 5 \ h \ \ t , \ Yellow-gray-brown and Light Gray, Slightly Moist, Very Firm, Micaceous Continued on br vwing No. 26 ,lLTY FINE SAN1 :LAYEY FINE SAND SILTY FINE TO AEDIUM SAND iLTY FINE SANL Il.1 p9.i 7.2 9.7 I I I PROJECT NO. 73-3-16BC BENTON ENGINEERING, INC. v 6 E ‘2 3 8 a = ,- > $j Ei n I 0 a 3 0 r 2 8 L I? 55 ? k t%g x $2 !l,-- G?- !3- :;I3 ;;;@I za- 29- 3a 31- 32- 33- 4- :,I@ $6- 37- $a- 39- IO-@ ti- z Cd i3$ SUMMARY SHEET $EZ BORING NO. 92 12(cOllt) SILTY FINE SAND Lenses of Clayey Fine Sand Drawing No. 27 PROJECT NO. I DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 25 SUMMARY SHEET BORING NO. 12(cont\ Light Brown To Brown With Orange Streaks, Slightly Moist, SILTY FINE SAND Very Firm, Micoceous PROJECT NO. DRAWING NO. 73-3-16BC BENTON ENGINEERING, INC. 26 c 0 . ? : : , . i ( Lenses of Clayey Fine Sand, 1 To 1 Inch Cloy Seams SILTY FINE SAND SUMMARY SHEET GORING NO. 13 ELEVATION_L89.0’ Abirt,Soft To Medium Firm, IXED WITH SILT’ Root Holee, Pomur,OccasIorml NE TO COARSE Shell Fragments, Friable II I Continued on Drawing No. 29 35.6 23.2 !8.6 10.; 9’ .A - 9.6 - 811 1O.f D6.: - - 32.: - - - PROJECT NO. 73-3-168-C I BENTON ENGINEERING, INC. I DRAWING NO 27 c 0 r 4 1 - , , z E . J .! I 2 I 1 c , SUMMARY SHEET BORING NO.at) ork Bmvm To Orange-brown, tLAYEY FINE TO bist, Soft To Medium Finn, MEDIUM SAND .iable, Shell Frqgmenh MIXED WITH SLIGHTLY SILTY elNE TO MEDIU SAND Y ‘my-green To Green Wfth tmoks Of Yellow and Orange, hoist, Soft To Medium Finn, lighly Fractured and Mixed Into l/4 To l/2 Inch Chunks, Gypsum and Yellow Iron Stain Filling Fractures In All Directions Lhers of Brown With Stnaks Of Yellow, Red, Omnge Mixed With Green And Groy L Very Finn Olive-Gray-Groy-Grn, Moirt,Very Finn, Gypsum Common, Pockets Of Whlte Cloy,Lemes Of Over 50 Percent Shel I Fragments, Lem Of Medium To Coarse Sandy Cloy Grey-green And Green With Streaks Of Orange And Yellow Moirt,Very Finn, H* -rmctlrred In Many Directions, CLAY SILTY CLAY CLAY LJ, :. $ ;z u* St’ 0 - - 33.r - 70.1 - - 5.6 - 0.2 - lL 50.6 18.8 lC8.: Y ot & gzrr :z - - - - - - - - - I DRAWING NO. BENTON ENGINEERING, INC. 28 BENTON ENGINEERING, INC. APPLIED SOIL MECHANICS - FO”ND*T,ON* 6717 CONVOY COURT SAN DIEGO. CALIFORNIA 82111 PHlLlP HENKING BENTON P”L*IDENT. ClYlL LHGINILI TELEPHDNF ,714) 56%18SS APPENDIX AA STANDARD SPECIFICATIONS FOR PLACEMENT OF COMPACTED FILLED GROUND 1. General Description. The objective is to obtoin uniformity and adequate internal strength in filled ground by proven engineering procedures and tests so that the proposed structures may be safely supported. The procedures include the clearing and grubbing, removal of existing structures, preparation of land to be filled, filling of the land, the spreading, and compaction of the filled areas to conform with the lines, grades, and slopes as shown on the accepted plans. The owner shall employ CI qualified soils engineer to inspect and test the filled ground as placed to verify the uniformity of compaction of filled ground to the specified 90 percent of maximum dry density. The soils engineer shall advise the owner and grading contractor immediately if any unsatisfactory conditions are observed to exist and shall have the authority to reject the compacted filled ground until such time that corrective measures are token necessary to comply with the specifications. It shall be the sole responsibility of the grading contractor to achieve the specified degree of compaction. 2. Clearing, Grubbing, and Preparing Areas to be Filled. (a) All brush, vegetation and any rubbish shall be removed, piled, and burned or other- wise disposed of so as to leave the areas to be filled free of vegetation and debris. Any soft, swampy or otherwise unsuitable areas shall be corrected by draining or removal, or both. (b) The natural ground which is determined to be satisfactory for the support of the filled ground shall then be plowed or scarified to a depth of at least six inches (6”), and until the surface is free from ruts, hummocks, or other uneven features which would tend to prevent uniform compaction by the equipment to be used. (c) Where fills ore made on hillsides or exposed slope areas, greater than 10 percent, horizontal benches shall be cut into firm undisturbed noturol ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer is placed and compacted on CI horizontal plane. The initial bench at the toe of the fill shall be at least 10 feet in width on firm undisturbed natural ground at the eleva- tion of the toe stake placed at the natural angle of repose or design slope. The soils engineer shall determine the width and frequency of all succeeding benches which will vary with the soil conditions and the steepness of slope. (4 APPENDIX AA -2- After the natural ground has been prepared, it shall then be brought to the proper mois- ture content and compacted to not less than ninety percent of maxlmum density in accordance with A.S.T.M. D-1557- 70 method that uses 25 blowr of a 10 pound hammer falling from 18 inches on each of 5 layers in a 4” diameter cylindrical meld of a 1/30th cubic foot volume. 3. Materials and Special Requirements. The fill soils shall consist of select materials so graded that at least 40 percent of the material passes a No. 4 sieve. This may be obtoined from the excavation of banks, borrow pits of any other approved sources and by mixirg soils from one or more sources. The material uses shall be free from vegetable matter, and other de- leterious substances, and shall not contain rocks or lumps of greater than 6 inches in diameter. If excessive vegetation, rocks, or soils with inadequate strength or other unacceptable physical characteristics are encountered, these shall be disposed of in waste areas as shown on the plans or OS directed by the soils ellgineer. If during grading operations, soils not encountered and tested in the preliminary investigation are found, tests on these soils shall be performed to determine their physical characteristics. Any special treatment recommended in the preliminary or subsequent soil reports not covered herein shall become an addendum to these specifications. The testing and specifications for the compaction of subgrade,subbase, and base ,naterials far roads, streets, highways, or other public property or rights-of-way shall be in accordance with those of the governmental agency having jurisdiction. 4. Placing, Spreading, and CompactiT Fill Materials. (a) The suitable fill material shall be placed in layers which, when compacted shall not exceed six inches (6”). Each layer shall be spread evenly and shall be throughly mixed duriw the spreading to insure uniformity of material and moisture in each layer. (b) When the moisture content of the fill material is below that specified by the soils ewineer, water shall be added until the moisture content is near optimum as specified by the soils engineer to assure thorough bonding durirrg the compacting process. (c) Wen the moisture content of the fill material is above that specified by the soils ewineer, the fill material shall be aerated by blading and scarifyi% or other satis- factory methods until the moistuie content is near optimum as specified by the soils ergineer . (d) After each layer has been placed, mixed and spread evenly, It shall be thoroughly compacted to not less than ninety percent of maximum density in accordance with A.S.T.M. D-1557- 70 modified as described in 2 (d) above. Compaction shall be accomplished with sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other approved types of compaction equipment, such as vibratory equipment that is specially designed for certain soil types. Rollers shall be of such design ~?hat they will be able -_..--.. -..- . ..---. _.- ._.- APPENDIX AA 5. 6. 7. a. (e) -3- ta compact the fill material to the specified density, Rolling shall be accamplished while the fill material is at the specified moisture content. Rolliw of each layer shall be continuous over Its entire area and the roller shall make sufficient trips to insure that the desired density has been obtained. The entire areas to be filled shall be compacted. Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compacting operations shall be continued until the slopes are stable but not too dense for planting and until there is no appreciable amount of loose soil on the slopes. Compacting of the slopes shall be accomplished by backrolliw the slopes In increments of 3 to 5 feet In elevation goin or by other methods producing satisfactory results. Field density tests shall betoken by the soils engineer for approximately each foot in elevation gain after compaction, but not to exceed two feet in vertical height between tests. Field density tests may be taken at intervals of 6 inches ‘in elevation gain if required by the soils engineer. Th e ocation of the tests in plan shall be so spaced to I give the best possible coverage and shall be taken no farther apart than 100 feet. Tests shall be taken on corner and terrace lots for each two feet In elevation gain. The soils engineer may take additional tests as considered necessary to check on the uniformity of compaction. Where sheepsfoot rollers are used, the tests shall be taken in the com- pacted material below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that the specified density has been obtalned. The fill operation shall be continued in six inch (6”) compacted layers, as specified above, until the fill has been brought to the finlshed slopes and grades as shown on the accepted plans. Inspection. SuffTclent lnspection’by the soils engineer shall be maintalned during the filling and compoctlng operations so that he can certify-that the fill was constructed in accordance with the accepted specifications. Seasonal Limits. No fill material shall be placed, spread, or rolled if weather conditions increase the moisture content above permissible limlts. When the work is interrupted by rain, fill operations shall not be resumed until field tests by the soils ewineer Indicate that the moisture content and density of the fill are as previously specified. Limiting Values of Nonexpansive Soils. Those soils that expand 2.5 percent or less from air dry to saturation under a unit load of 500 pounds per square foot are consldered to be nonexpansive. All recommendations presented in the “Conclusions” section of the attached report are a part of these specifications. --..--.. -..- .._ --...- .._ BENTON ENGINEERING, INC. APPLIED BOIL “EC”(*NICS - FOUNDATION* .3717 CONVOI COURT P”lLlP “ENKINCI BENTON CIISIcmWI ClYlL LNCINIEE” APPENDIX A Unified Soil Classification Chart* SOIL DESCRIPTION GROUP SYMBOL I. COARSE GRAINED, More than half of material is &te~ than No. 200 sieve size.** GRAVELS CLEAN GRAVELS s half of coarse fraction is larger thon No. 4 sieve size but SmallerGRAVELS WITH FINES than 3 inches (Appreciable amount of fines) SANDS CLEAN SANDS More than half of coarse fraction is smaller than No. 4 sieve size SANDS WITH FINES (Appreciable amount of fines) II. FINE GRAINED, More than half of material is smaller than No. 200 sieve size.** SILTS AND CLAYS Liquid Limit Less than 50 SILTS AND CLAYS Liquid Limit Greoter than 50 III. HIGHLY ORGANIC SOILS GW GP GM GC Well graded gravels, gravel-sond mixtures, little or no fines. Poorly graded gravels, gravel-sand mixtures, little or no fines. Silty gravels, poorly graded gravel- sand-silt mixtures. Clayey gravels, poorly graded grovel- sand-clay mixtures. SW SP SM SC Well graded sand, gravelly sands, little or no fines. Poorly graded sands, gravelly sands, little or no fines. Silty sands, poorly graded sand-silt mixtures. Clayey sands, poorly graded sand-clay mixtures. ML CL OL MH CH OH Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt-sand mixtures with slight plasticity. Inorganic clays of low to medium plos- ticity, gravelly clays, sandy clays, silty clays, lean clays. Organic silts and organic silty-clays of low plasticity. Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. Inorganic clays of high plasticity, fat clays. Organic clays of medium to high plasticity PT Peat and other highly organic soils. TYPICAL NAMES TELLPHONE ,714, S(1B.1SSS * AAn+wl h\, An I-mm. nf t=nni.x.~.. nnrl R,wen,,nf R~~lnmniinn ;n Inmmrv 1957 BENTON ENGINEERING, INC. APPLIED SOIL MECHANICS - FOUNDITIONS 6717 CONVO” COURT SAN DIEGO. CALIFORNIA 82111 PHlLlP HENKING BENTON P”1.10Lz111. ClYlL EHGINTER APPENDIX B Sampling The undisturbed soil samples are obtained by forcing a special sampling tube into the undisturbed soils at the bottom of the boring, at frequent intervals below the ground surface. The sampling tube consists of a steel barrel 3.0 inches outside diameter, with a special cutting tip on one end and a double ball valve on the other, and with a lining of twelve thin brass rings, each one inch long by 2.42 inches inside diameter. The sampler, connected to a twelve inch long waste barrel, is either pushed or driven approximately 18 inches into the soil and a six inch section of the center portion of the sample is taken for laboratory tests, the soil being still confined in the brass rings, after extraction from the sampler tube. The samples are taken to the laboratory in close fitting waterproof containers in order to retain the field moisture until completion of the tests. The driving energy is calculated as the average energy in foot-kips required to force the sampling tube through one foot of soil at the depth at which the sample is obtained. .- Shear Tests The shear tests ore run using a direct shear machine of the strain control type in which the rate of deformation is approximately 0.05 inch per minute. The machine is so designed that the tests are made without removing the samples from the brass liner rings in which they are secured. Each sample is sheared under a normal load equivalent to the weight of the soil above the point of sampling. In some instances, samples are sheared under various normal loads in order to obtain the internal angle of friction and cohesion.. Where considered necessary, samples are saturated and drained before shearing in order to simulate extreme field moisture conditions. Consolidation Tests The apparatus used for the consolidation tests is designed to receive one of the one inch high rings of soil as it comes from the field. Loads are applied in several increments to the upper surface of the test specimen and the resulting deformations are recorded at selected time intervals for each increment. Generally, each increment of load is maintained on the sample until the rate of deformation is equal to or less than l/10000 inch per hour. Porous stones are placed in contact wlth the top and bottom of each specimen to permit the ready addition or release of water. Expansion Tests One inch high samples confined In the brass rings are permitted to air dry at 105’ F for at least 48 hours prior to placing into the expansion apparatus. A unit load of 500 pounds per square foot is then applied to the upper porous stone in contact with the top of each sample. Water is permitted to contact both the top and bottom of each sample through porous stones. Continuous observations are made until downward movement stops. The dial reading is recorded and expansion is recorded until the rate of upward movement is less than l/10000 inch per hour. APPENDIX C BENTON ENGINEERING. INC. RECOMMENDATIONS FOR EXPANSNE SOILS Case (I): 1. 2. 3. 4. 5. 6. Case (II). 1. 2. For soils with an expansion potential over 6 percent under unit load of 150 pounds per square foot from air dry to satumtion(Tests to be made after grading), Use continuous interconnected reinforced footings throughout, ond place these at a minimum depth of two feet below the lowest adjacent exterior final ground surface. Avoid the use of isolated interior piers where possible. Reinforce and Interconnect continuously with steel bars 011 Interior ond exterior footings with a minimum of one #5 bar at 3 inches above the bottom of all footings and one #5 bar placed 1 l/2 inches,below the top of the stems of the footings. Use raised wooden floors spanning between continuous footings If possible. Reinforce all concrete slabs on grade with a minimum of 6 x 6 - lo/10 welded wire fabric and provide a base layer of at least 4 inches of crushed rock beneoth all concrete slabs. A moisture barrier should be provided above the crushed rock and then 2 inches of sand should be placed over the moisture barrier ond below the bottom of the slab. Separate gamge slabs from perimeter footings by l/2 inch thickness of construc- tion felt or equivalent, to allow independent movement of garage slabs relative to perimeter footings. Assure complete separation by extending the construction felt over the full depth of the front thickened edge of the garage slab. Cut off garage door stops at least l/2 inch above the garage slab. Provide positive drainage away from all perimeter footlngs with a vertical fall of at least 6 inches in a horizontal distance of 5 feet, outslde the house walls. Exercise every effort to assure that the sol1 under the foundatlons and slabs has a uniform moisture content at least 1 to 3 percent greater than optimum throughout the top 3 feet below finished grade at the time of placing the foundations and slabs. For soils with an expansion potential over 2 percent but less than 6 percent under unit load of 150 pounds per square foot from air dry to saturation, Same OS Core (I) with the following exceptions: Continuous footings may be placed at Q minimum depth of 18 inches in lieu of 2 feet as indicated in Item 1 under Core (I) No. 4 reinforcing bars may be used in lieu of No. 5 bars as indicated in Section 2 under Case I. BENTON ENGINEERING. INC. APPENDIX D Sponish Village Unit Nos. 1 and 2 Roneho La Costa Carlsbad, California Project No. 73-3-16Bc May 16, 1973 -2- As a part of the subject preliminary Soils Investigation, we have also completed o reconnaissance geologic investigation and transmit herewith our findings. The intent of this appendix is to summorize our observations concerning the geology and potential geologic haz- ards on the subject site. The scope of this investigation consisted of a visual site examination, literature research, and a review of several soils investigation reports in the immediate vicinity. In general, the site is underlain by the Delmar Formation, Torrey Sandstone, alluvium, colluvium landslide debris, and topsoils. Principal geologic hazards include: old landslide zones, the clayey Delmor Formation which is landslide-prone and contains expansive c&s, and thick de- posik of soft compressible alluvium in the major stream valley. It is our understanding that one and/or two story wood frame dwellings are planned for this proposed development. On April 6, 10 and 11, 1973, a visual sits examination was made and surrounding areas were inspected to provide relevant information for comparison. Available pertinent literature was searched for data on geology and geologic hazards in the vicinity. Boring logs from this soils in- vestigation as well as from our previous soils investigations in the immediate vicinity were reviewed. This irregularly-shaped parcel consists of approximately 142 acres bounded by La Cost0 Ave- nue on the north, El Camino Reol and the proposed Lo Costa Plaza on the west, Wiegand property (proposed El Camino Glens) on the south ond Lo Costa South on the east and northeast, It lies in a portion of the SE l/4 Section 35, the SW l/4 Section 36 T12S, R4W, SBBM, and the N l/2 of Section 2, T13S, R4W, SBBM, City of Corlsbod, San Diego County, California. Moderately sloping topography is predominant on this site which includes rounded hilltops, moderately to steeply sloping valley and canyon sides, and gently sloping valley bottoms. Drainage is in a westerly direction. Annual grasses and scrub brush cover most of this area which has been partly cultivated in the recent past. Elevations vary from 49.3 feet in the valley bottom adjacent to El Camino Real along the southwest boundary to 252.9 feet on the hilltop in the northwestern part of the property. Total relief is 203.6 feet, which gives a gwd indication of the hilly nature and high topographic relief of the area. The soils and geology were observed in natural surface exposures and in nearby and adjacent cut slopes. In addition, boring logs from this soils investigation and from previous soils investigat- ions were reviewed. These previous investigations include the following: Project No. 70-11-188, entitled “Phase I, Pre-Preliminary Soils Investigation, MBD Property, Rantho La Costa, San Diego County, California,” dated December 11. 197Oi Prolect No. 69-9-8C, entitled “Preliminary Soils Investigation, La Costa South Unit Nos. 5, 6, and 7, East of the Intersection of La Costa Avenue and El Camino Real, San Diego County, California,” dated November 7, 1969; Project No. 69-3- 24BC, entitled “Preliminary Soils Investigation, La Costa South Unit Nos. 2, 3, and 4, East of the lntemection of La Costa Avenue and El Camino Real, San Diego County, California,” dated May 22, reject No. 73-3-lA, entitled “La Costa de Marbella. Lot 206, La Costa South Unit No. 3. , California,” dated April 11, 197% Project No. 72-l-llA, entitled “Soils Investigation, Proposed Borrow Area, Southeast Comer of the lntenection of El Camino Real and La Costa Avenue, La Costa, California,” dated February 18, 1972; Project No. 72-6-2BC, entitled “Preliminary Soils Investigation, Wiegand Parcel, San Diego County, California,” dated Jul 20 1972; and Pro- ject No. 73-3-9BC entitled “Preliminary Soils Investigation, Spanish Village - +%+7Zre Site, La Costa, Carlsbad, California,” report forthcoming. BENTON ENGINEERING. INC -3- The entire area is underlain by the Middle Eocene age (approximately 45 million years before present) Delmar Formation which crops out along the lower valley sides. It is overlain by the Middle Eocene age Torrey Sandstone which crops out on the higher elevation ridges and hilltops. Quaternary alluvium and colluvium are present in the canyon and valley bottoms and lower valley sides. Landslide and slump debris is present locally, especially along the sides of the main east-west t-valley and on the steep scarp facing La Costa Avenue along the north boundary. Topsoils are variable in thickness aniiave been deeply cultivated on most of the gently sloping cmd flat,-land areas. The Delmar Formation is the oldest and lowest elevation unit, underlying all of the other formations which are younger in age. Due to a slight regional dip of approximately 1.5’ down- ward in a west-southwesterly direction, the top of the Delmar Formation is at different elevations across the area. Along the northern boundary the top is at about 107 feet elevation, near the southwestern boundary the top is at about 87 feet elevation, and in the eastern section the top is at about 158 feet elevation. The base of this formation is not evosed in this area, but it is at least as low as 50 feet elevation where the formation is exposed in road cuts along El Camino Real. The Delmar Formation is composed primarily of green and gray-green clay, and clayey silt with interbeds of light gray and light brown clayey and silty sand. Clays in this formation are es- pecially weak and landslide-prone. Special attention should be given to them when they are en- countered during grading to assure that cut and/or fill slopes are not over-steepened. In addition to their landslide danger, they are also critically expansive and special foundation designs will be required if they ore allowed to remain within the footing zone of proposed structures. In general, we recommend laying cut slopes made entirely or in part within this clayey formation back to at least 3:l (horizontal to vertical) or flatter. Of particular note, in this regard, is the grade planned for Levante Street extension at El Camino Real where several hundred feet of roadway will encounter the Delmar Formation clay. Torrey Sandstone overlies the Delmar Formation and forms the high-relief rugged badlands- appearing topography in the higher elevations. It underlies the highest hills and ridges which stand out in bold relief in contrast to the Delmar Formation which is found in subdued gentle relief only in the lower elevations along the valley bottoms. Torrey Sandstone is composed primarily of light gray and light brown slightly silty to silty and clayey fine to medium sand. Locally, these soils can be expansive and should be tested prior to use for select borrow material. The Torrey Sandstone is not normally subject to landsliding by itself. However, since it overlies the landslide-prone Del- mar Formation, it is often directly involved riding down “piggy-bock” style with the underlying failing Delmar clays. Torrey Sandstone and Del- mar Formation green clays are encountered in , the entire cut slope should be treated as though it was bll clay and be loid back to slopes in ‘the order of 3:l (horiiontal to vertical) or flatter to mitigate the possibility of landslidina. / Quaternary alluvium and colluvium are present in the main canyon and valley bottoms and lower valley sides. Colluvium in this area is essentially slope wash that has not yet been transported downward into the creek bottoms and it may be treated like alluvium for grading purposes. Alluvium in the maln eat-west valley is at least 2ot feet thick in ik lower reaches. It consists of loose and soft, porous deposits of sand, silt and clay in varying mixtures. In all cases, alluvial and colluvial materials should be removed and recompacted, or in the case of deep valley fill partially removed and recompacted prior to placing additional fill or footings. The water table in the lower reaches of the main east-west valley is at about 44 to 45 feet elevation. BENTC.~ ENL3INEERING. INC. -4- Landslide and slump debris is present along the side of the main east-west valley and along the north side of the property facing La Cost0 Avenue. In each case, failures ore related to the clayey Delmqr Formatio . Ps outlined in ouPoforementioned Pre-Preliminary Soils Investi- gation of the MBD Propert Ip we still do not recommend development of the northern part of this area along La Costa Avenue We recommend that any proposed development be placed a minimum of 50 feet back from the top orthe scarp above La Costa Avenue. . Along the sides of the moin east-west valley, numerous small slumps, pop-outs and old soil failures ore present. Most of these and their accompanying loose material can be removed and re- compacted during grading. Two slides of particular interest were encountered in borings on the ridges on each side of the mouth of the main east-west (Borings 1 and 2 of the soils report on Spanish Village - West - 7 Acre Site, in progress). These old slide zones were located in ?he upper part of the Delmar Formation clay and are dipping adversely downward out of slope. Grading operations around these two ridges (especially along Levante Avenue extension) should be done with caution; buttressing or laying the slopes back may be necessary, depending upon each individual situation. Another weok landslide zone was encountered in Boring No. 10 of this report ot o depth of 25.5 to 27 feet. It dips generally easterly across the proposed cut slope, but it will doy-light at just about the pod elevotion of the lok in the “C” Street cul-de-sac. Buttressing or low slope rot- ios may be required in this area to mitigate possible slope failure. A weak landslide zone was encountered in Boring No. 13 of this report at a depth of 16.5 to 24 feet. However, the dip is favorable into the existing hillside and filled ground is proposed to cover the entire area, ‘ Several maior landslides and potential maior landslides were observed during our reconnais- sance of the site. In addition, shallow slumping ond creep was noted in the topsoils and in the clayey Delmar Formation. The principal slide areas and weak landslide-prone Delmar Formation are discussed in the paragraphs above. Based on our observations to date, it is our opinion that cut slopes entire’ly within the Torrey Sandstone may be planned for ratios of 1 .5: 1 (horizontal to verti- cal) or flatter and cut slopes within the Delmar Formation or combined Uarmarrmation-Torrey Sandstone should be planned for cut slope ratios ofhorizontal to vertical) or flatter unless special recommendations are mode to the contrary. Locally, small faulk are present in the area, but none are known to be active at this time. The closest potentially active fault is the north-northwest trending Rose Canyon fault located approx- imately 6.3 miles southwesterly under the Pacific Ocean. No ma or art ed or are known to have occurred along this fault in recent i e hauakgf have been record- h istory. A few minor low magnitude earthquakes hove been reported in the general area, however, but have caused little, if any, damage. 0 The closest large active faulk are the Elsinore and San Jacinto faults located 25.5 and 49 miles northeasterly, respectively. The closest major earthquakes have occurred to the northeast along the San Jacinto fault and 56 miles to the northwest on the Newport-lnglewood fault. These moder- ate-sized earthquakes had Richter scale magnitudes ronging from 6.0 to 6.8 and produced Modified Mercalli scale intensities on the order of V to VI in the La Costa area. These intensities are approx- imotely equivalent to ground accelerations of 0.015 g to 0.032 g, respectively. In our opinion, simi- lar earthquakes in the future will generate similar ground accelerations in the La Cost0 area. BENTON ENGINEERING. INC. -5 An area subjected to Modified Mercalli scale intensity VI ground accelerations would ex- perience the following maximum effects: Felt by all; many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster or damaged chimneys. Pendulum clocks stop. Damage slight. No damage is anticipated to buildings of good design and construction. Southern California has been placed in Seismic Risk Probability Zone No. 3dUniform Building Code, 1970, Page 122). In this zone, Modified Mercalli scale intensities of VIII (approx- imately equal to a ground acceleration of 0.149 g) or greater may be expected. An areo subjected to earthquake induced Modified Mercalli scale VIII ground accelerations would experience the fol- lowing effects: Damage slight in specially designed structures, considerable in ordinary substantial buildings, and great in poorly built structures. Panel walls thrown out of frame structures. Fall of chimneys, columns, and walls. Heavy furniture overturned. Well-water levels change. Persons driving motor cars disturbed. However, based on our experience in the area and the known seismic r &, it is our opinion that Intensity VIII or greater seismic ground accelerations are unlike y to occur in the La Costa area. r Therefore, a normal seismic factor for this area of Southern California should be adequate for most structural design, If you have any questions ofter reviewing this appendix, please do not hesitate to contact this office. This opportunity to be of service is sincerely appreciated. Respectfully submitted, BENTON ENGINEERING, INC. By w.,! w W. J. Elliott, Registered Ceologist, 1101 Reviewed by M. V. .Pothier, Civil Engineer Distr: (4) Addressee WJ E/PHB/meg BENTON ENGINEERING, INC. APPLIED SOIL MECtiANICB - FOUND*TIONS 6717 CONVOY COURT SAN DIEGO. CALI.=ORNIA 92111 PHlllP HENKlNO BENTON PRESIDLNT ClYlL SNGIHEER May 31, 1973 TELEPHONE (71.3, 865.1856 La Costa Land Company Costa Del Mar Rood Carl&d, Colifornia 92008 Attention: Mr. Irv Roston Subject: Project Ido. 73-3-16BC Review of Preliminory Grading Plon Spanish Village Units 1 ond 2 Ranch0 La Costo Carlsbad, California Gentlemen: In accordance with the request made by Mr. Sam Gaines of Rick Engineering in Son Diego, California, a review wos made of the preliminory grading plan prepared by Rick Engineering of San Diego ond dated April 2, 1973 with a revision on May 23, 1973. The preliminary grad- ing plan shows a total of 129 lots easterly of Borings 4 ond 11 described in our report doted May 10, 1973. Generally, the proposed cut and fill slopes shown on the grading plan are feasible from slope stobility point of view except the proposed 2 horizontal to 1 vertical cut slope southerly of Boring 10 area where the proposed excovotion will cut through a previous landslided zone in the toe area of the slope. It is therefore, recommended that the proposed cut slope in the area . be changed to 3 horizontal to 1 vertical or flotter. In lieu of this, the previous landslided zone may be overexcavated to a distance equivalent to the height of cut or greater inside the proposed fill slope surface and then recompacted to a 2 horizontal to 1 vertical stabilized fill slopes. This area should be carefully examined by an and eetric .,_p_** ? stability analysis based on the gzrnxic the lat~!,,~e~~~ e... ,_II .,,_, ,., ,, determine the required thickness of the stabilized fills and the necessity of a sheor key for the fill slope. The recommended thickness of overexcavation may have to be odjusted in accordonce with the findings of the slope stability analysis. Respectfully submitted, BENTON ENGINEERING,INC. Distr: (4) Addressee (1) Attention: Mr. Bob Stork (2) Rick Engineering, San Diego Attention: Mr. Sam Gaines PWlLlP “ENKIN(I mENTON l II.IDINT ClWL 1*01*1&m BENTON ENGINEERING. INC. APPLIED *OIL YLCHANICI - FO”NDATIONO 0 67.9 EL CNON moULE”II1D .AN DICQO. CALlroRNlA *2,,s December 11, 1970 Ranch0 Lo Costa Route 1, Box 2550 Encinitas, California 92024 Subject: Project No. 70-11-188 Phase I, Pre-Preliminary Soils Investigation MBD Property Ranch0 La Costa San Diego County, California Gentlemen: CONCLUSIONS It is concluded from this initial limited investigation and laboratory test results that: 1. Generally the medium firm to very firm natural soils are suitable for the support of compacted fi I led ground and/or proposed two story apartment buildings. However, a land- slide was found at Boring 2A and it is possible that other unstable areas could exist alox ?%i and northwest sides of the property. Severol slide oreos have previously been encoun- tered during grading on areas east of this property. These slides are generally caused by shear e underlying claystone formotion which in some cases dips downward to the therefore generally recommended that building ond the placing of filled 2 imate location of this recommended limit of development is shown on Drawing Id from within the north and northwesterly portions of the site. The approx- . 0.1. Itmay be possible to mvare only ror llmlted building sites north of this line to as low as devotion 150 feet, provided additional investigations and geologic studies verify each area is stable. 2. The resulk of the laboratory expansion test and Atterberg Limit tests indicate that the claystone encountered in Borings 2A and 3 is on “expansive” and “CH” relatively high plasticity type clay. The results of tests performed during investigations of adiacent areas also indicate that the clays, silty clays, and cloystone in the vicinity ore “exponrive” soils. &Ised on the findings in this initial investigation, it would appear that it will be possible ta develop most of the ored without moking excavations to within 3 feet above these underlying expansive soils. If this cOn be accomplished, then specially designed footings and slabs would not be required. However, if the expansive soils are allowed to remain in the upper 3 feet below finished grade in either cut or compacted filled ground areas, then it is recommended that footings and slob be specially designed. It is probable that the silty cloy and claystone form- ations would be exposed if excavations are carried below Elevation 116 feet in the vicinity of Boring No. 3. Project No. 70-11-188 Roncho Lo Costa -2- December 11, 1970 3. The results of the load-consolidation tests indicate that certain of the alluvial soils in the valley in the southerly portion of the site are somewhot compressible under relatively small unit loods when ollowed to become saturated. It is therefore recommended thot buildings in this area be supported on a minimum thickness of 5 feet of compacted filled ground. This would require the removal and recompoction of the upper oiluviol soils in those areas where either less than 5 feet of filled ground is to be pieced or where less than 5 feet of excavation is plonned. 4. All of the soils may be satisfactorily compacted in the fill oreas. The filled ground should be placed on noturol sails determined suitable for support and should be uniformly com- pacted to at least 90 percent of maximum dry density in accordance with the attached “Standard Specifications for Placement of Compacted Filled Graund,” Appendix AA. Any existing fill soils, such as exist for former earth fill reservoirs, and any loose, soft, or compressible soils existing in proposed compacted filled ground areas should be removed OS required by the sails engineer and the compacted filled ground placed on approved natural soils. 5. It is probable that cuts in the silty sand and clayey sand sails, and compacted fills constructed using these soils will be stable with an adequate factor of safety for heights up to 40 feet when constructed on a slope ratio of 1 l/2 horizontal to 1 vertical. However, if exca- vations ore made in the clay or claystone formations, it is recommended that these be cut on a slope ratio of 2 l/2 horizontal ta 1 vertical or flatter. The above conclusions assume that suit- able erosional control and proper droinoge will be provided to prevent woter from running over the top of expased slopes, The samples obtained in this investigation will be retained in our laboratory for a period of 90 days. In order to complete a preliminary soils investigation report additional tests would have to be performed on the samples already taken and additional borings and field invest- igation would be required to better determine the suitability of certain areas for development as may be proposed by the design grading plans. We will owait your further instructions before proceeding with any additional testing. j Respectfully submitted, BENTON ENGINEERING, INC. BY is?PL R. C. Remer Distr: (2) Addresee (1) Rick Engineering Company (1) Mr. Benny Gonzales 6FNTr2,! FPIGlWEERING. INC. Project No. 70-11-188 Ron&a La Costa -3- December 11, 1970 DISCUSSION The initial limited phase of a preliminary sails investigation has been completed on the MBD property located on the south side of La Costa Avenue and east of El Camino Real in San Diego County, Califomio. The objective of this initial investigation was primarily to determine the existence of any soil conditions which might be detrimental or require special consideration in developing the site for the construction of two story apartment buildings. In order to accomplish this objective, eight borings were drilled, undisturbed and loose bog samples were obtained, ond laboratory tests were performed on certain somples. A limited geologic reconnaissance wos also made of the area by Dr. Richard L. Threet, Geologist, and a copy of his report is attached hereto as Appendix C. The general topography of the area may be described as gently rolling to steep sloping terrain. A high ridge extends in an east-west direction in the north central portion of the site that has limited run off to the north ond a valley in the southern portion direck the major drainage to the west. According to the “Soil Map” prepared by the U. 5. Department of agriculture, the upper sails in the Oreo ore described OS Huerhuero fine sandy loam, Carlsbad loamy fine sand, Los Flores loamy fine sand, and Botelia loamy sand. The sails encountered in the investigation consisted primarily of slightly silty fine to medium sand, fine to medium sand, silty very fine to fine sand, slightly silty fine sand, very fine sandy silt, clayey fine sand, fine sandy clay, slightly clayey fine sand, clay, silty cloy, and clayey very fine to fine sand. Field investigation Eight borings were drilled with a truck-mounted rotary bucket-type drill rig at the approximate locations shown on the attached Drawing No. 1, entitled “Location of Test Borings.” The borings were drilled to depths of 11 to 55 feet below the existing ground surface. A continuous log of the soils encountered in the borings was recorded at the time of drilling and is shown in detail on Drowing Nos. 2 to 15, inclusive, each entitled “Summary Sheet.” The soils were visually classified by field identification procedures in accordance with the Unified Soil Classification Chart. A simplified descriptlan of this clossifiwtion system is presented in the attached Appendix A at the end of this report. Undisturbed samples were obtained at frequent intervals, in the sails oheod of the drilling. The drop weight used for driving the sampling tube into the soils was the “Kelly” bar of the drill rig which weighs 1623 pounds, and the overage drop was 12 inches. The general procedures used in field sampling are described under “Sampling” in Appendix B. Laboratory Tests Laboratory tests were performed on certain undisturbed samples of the soils in order to determine the dry density and moisture content. The results of these tests are presented on Drawing Nos. 8, 10, 12, 13, and 14. Consolidation tests were performed on representative samples obtained in BENTON ENGINEERING. INC Proiect No. 70-l 1-18B Roncho La Costa -4- December 11, 1970 Borings 4, 5, and 6 in order to determine the load-settlement characteristics of these soils. The results of these task ore presented on Drawing Nos. 16 and 17, each entitled “Consolidation Curves. ” in addition to the above laboratory tests, an expansion test was performed on a representative sample of the cloystone encountered to determine its volumetric change chorocteristics with change in moisture content. The recorded expansion of the sample is presented OS follows: Percent Expanslon Under Unit Load of Depth of 500 Pounds per Square Boring Sample Sample, Foot from Air Dry No. No. in Feet Soil Description to Satumtion 3 6 26 Cloystone 5.75 The general procedures used for the laboratory tesk ore described briefly in Appendix B. In order better to classify the finer groined soils, Atterberg Limit tests were performed on selected samples in accordance with A.S.T.M. Designations D 423-6lT and D424-59. The results of the tesk and the final group symbols ore presented as follows: Baring No. Sample No. Depth in Feet Sail Description Liquid Limit Plastic Limit Plasticity Group index Symbol 2A 6 25.5-26.0 Clay 56.2 18.6 37.6 CH 3 b4 21 .O-22.0 Cloy 62.2 21.8 40.4 CH sENTON ENGINEERING. INC :,,Y’ _’ :, Pre-preliminary geologic investigation of property near Ranch0 La Costa, San Diego County, California The subject property, about 175 acres, is part of a dissected, elevated coastal plain lying mostly east of El Camino Real and south of La Costa Avenue (essenfially the southeast quarter of section 35 and the south half,!of the southwest quarter of section 36, T. 12 S., R. 4 W., plus rhe?north-central portion I spent several hours in the field', noting observations of road cuts and natural outcropson a large-scale topographic map furnished by the client. It is my conclusion that the prop- erty is composed entirely of flat-lying~'(Eocene-Tertiary) nreen -and irregular beds of muddy sandstone below the lOO- to 10%foot contour in the northern part of the subject property (dipping gently southward to lie below the go-foot contour in the southern part of the property) , overlain by the,Del Mar Sand- stone which makes up the higher parts cf:the property. There are remnants of Pleistocene marine terrace deposits and fossil shells at .various levels. The sedimentary strata are mostly covered by a veneer, a few feet to perhapsten feet thick, of loamy residual soil or slope wash (colluvium). ,, , ;:,I,:. ,.In the vicinity of,~the con@ict:,be,tween the two main sedimentary formations, considerable ground. water moisture is present, supporting a fringe of reeds (esp,ecially on north-facing slopes, but there, is little evidence.of extensive landsliding. In,qeneral, the weathered sandstone above, the impermeable mud- stone merely disintegrates or is sapped at the zone of moisture, creating sapping amphitheaters and benchesabove the slopes of green mudstone. A southerly tilted block o'f sandstone was found in an unusually low position in the maingully just east of the large road,cut across La Costa Avenue ~from,the sewage treatment plant, possibly indicating minor qlide-block landslidiqin the oversteepened bluffs overlooking the valley of San Marcos Creek. In any case, the.green mudstone-is highlyexpansive and can be expected to be subject to extensive soil,*creep to depths of E :‘p;;:;;l; Pre-preliminary geologic reconnaistsancel,L,a.,Costa 2 several feet. Where grading is done on tne.northrfacing,slopes, cuts in the sandstone and in the expansive~mudkon4~'must be scrupulously protected against surface run off. Especially where existing slopes of the expansive mudstone are loaded with fills, adequate provisions for keying the fills to the base and forproper sub- surface drainaqe beneath tl m $44~ must be made, to avoid later- ally floating the fills off the mudstone base. The ~remainder of the subject property,seems to be free of geologic problems related to grading, ,except for the tilled sdils developed mostly on the expansive'~ggeen mudstone in the valley in the southern and southwesterti"&rtion off the property. '. Those soils have been disturbed and modifaed, probably to depths of several feet, by ,repeated wetting and drying, and they may require special treatment for suitable foundations. November 23, 1970 c Richard L:Threet ,' Registered~Ceolo.gist No. 340 5737 Trinity Place San Diego, California 92120 .I t:; .;i ;:.- , i”.~ ,~ “‘+(’ CONSOLIDATION CURVES LOAD IN NIPS PER SOUARE FOOT 0.6 0.8 1.0 2 4 6 -- PROJECT NO. -mTm- IO I’ Hole 4 Sample 2 Hole 5 Sample 2 A’ . 0 INDICATES PERCENT CDNSOLIDATION AT FIELD MOISTURE . INDICATES PERCENT CONSOLIDATIDN AFTER SATURATION BENTON ENGINEERING, INC. I DRAWlNO NO. 29 I . . ” 0:. ,.,. ‘~ ii ,. .,_-_ ..,,. ^ ,,__ ._... 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