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Home My WebLink About; Banks Residence 2740 Argonauto Street; Soils Report; 1989-09-27. C.H. WOOD CIVIL ENGINEER/GEOTECHNICAL ENGINEER BANKS RESIDENCE 2740 ARGONAUT0 S-I-. CARLSSAD 9 CAI-IF. AfHE; TRIFSTF DRIVE . CARLSBAD, CALIFORNIA 92008 l (619) 720-9641 C.H. WOOD CIVIL ENGINEER/GEOTECHNICAL ENGINEER File #035 09/27/89 Mr. Ron Banks 2740 Argonauto Street Carlsbad, California 92009 Subject: Soil Conditions, 2740 Argonauto Street, Cnrlsbad, California Dear Sir: In 1982, while working for Alpha Laboratories, I prepared two soils reports for your property located at the subject address. One was a “Preliminary Soils investigation” (pre1iminar.v to structural and grading design and prior to actual construction). The other was a quality control report (for earthwork construction of filled ground under and adjacent to the house that was constructed). These reports accurately depicted the natural soil conditions, the imported fill used during grading, and the filled ground after the completion of earthwork in 1982. Since 1982, a concrete crib-block retaining wall retaining about 3.5’ of soil was constructed in the north-easterly corner of the lot. The down-slope face of this wall is in the order of 8’ high. However, it appears that the base of the wall was extended down through the loose native soils and also to hold the wall footing (or bearing away from the face of slope. Roth of these were following the findings and recommendations contained in the “Preliminary Soils Investigation!’ of 1982. The report for the “Preliminary Soils Investigation” contained a plot plan with topography with 1’ contours. The plot plan was a reduced Zerox copy of the surveyed topography that was used later to prepare the grading plans. I used a hand level, this topography and my recollection of the site in 1982 to arrive at the fact that the wall retains only about 3.5 feet of fill. The retaining wall backfill appears (through the crib-block spaces) to be a select fill of granitic origin and it does not appear to have been compacted. By assuming the fill and backfill to have minimum strength parameters and to be compressible then the “worst case scenario” can be developed. Page 1 of 6 401!i TRIESTE DRIVE. CARLSBAD. CALIFORNIA 92008 l (619) 720-9641 vile #035 09/27/89 The minimum, conservative soil parameters for the “worst case” assumptions’ and the soil data from the 1982 reports are as follows: Soil Condition: Undisturbed, firm native Description of soil: Maximum Density: Optimum Moisture: Internal friction angle: Cohesion intercept: Relative compaction: Expansive potential: Compressibility Red/Tan, Clayey Gravel 127 pcf 12% 35 Deg. 250 psf 85% Sli$ht Very low Compacted, imported select fill Tan Silty Sand (DG mix) 122 pcf 10.5% 36 Deg. 120 psf got% Very low Uncompacted, fill and backfill __ Tan Silty/Clayey Sand 120-130 pcf 8 to 10% 29 Deg 0 psf 78% None to Slight Very high 1 These are Worst case assumrstiona and represent the worst conceivable conditions from known information. They form a u conservative basis for any calculations or analysis. Page 2 of 6 File #035 09/27/89 The following applicable parameters were cornouted’ from the above, conservative data shown on page 2: Soil Condition: Undisturbed, Compacted, Uncompacted, firm native imported fill and select fill backfill - Average field Density: 107.9 pcf 111.0 pcf 97.5 pcf Steepest slope ratio for 0.25:l lo’slope & Fs = 1.5 1.08:1 1.85:1 Active pressure (as 21.0 pcf 20.4 pcf 26.85 pcf fluid density) for wall with 3:12 batter and 1O:l sloping backfill Allowable passive 128 psf at 249 psf at 0 psf pressure for slope down surface & surface & & *way from wall at 1O:l increasing at increasing at ratio and wall with 3:12 384 pcf per 233 pcf per batter foot of depth. foot of depth. Minimum allowable foundation bearing Value: 2200 psf 2000 psf 0 psf (Do not bear foundations on this soil.) CONCLUSIONS: It is my opinion that the retaining wall is stable and will preform satisfactorily at the present geometry and as constructed. The shallow fill should be recompacted if it is to support structures that are susceptible to differential movement. While this fill is landscaped and is not depended upon for support of anything, I see no logical reason for recompacting at this time. However, any construction in this area without removing and recompacting the loose fill would end in disaster. * These values are computed values. They are the answers resulting from substituting the above conservative parameters into formulas (via computer). These s are shown for information only and for the sole purpose of substantiating the conclusions and recommendations. This format was chosen to convey the maximum information in the shortest space as concisely aa possible. These are up& recommendations. Obviously, flatter and lower slopes, higher soil strength parameters, and lighter foundation loads (all as related to this site) will produce m factors of safety than those used to calculate these values. c. H. wood (619) mo-SW C”l~,a& Xn-’ CuhbM, CA exQa Page 3 of 6 File #035 09/27/89 I make the following recommendations concerning any new construction: 1) The initial phases of w proposed construction be the physical checking of the .subgrade soils by conventional soil tests to determine compaction. Thereafter, all loose fill (compaction of less than 90%) in the vi.cinity of new construction be removed, replaced and recompacted to a minimum of 90% in accordance with the aDDliCable Do&ions of the attached recommended grading specifications. 2) Fill slopes steeper than 2:l are not recommended regardless of slope height. 3) Foundations should bear on competent soil (Compact fill or undisturbed native) and the foundation contact pressure should not exceed 2000 psf. 4) Active pressures as an equivalent fluid density for calculation of the stability of the crib wall with the 3 on 12 batter should equal or exceed 27 pcf. 5) Passive pressures for resistance to lateral movement may safely assumed to be 250 psf at the surface and increasing at the rate of 230 psf per foot of depth. The coefficient of friction of concrete to competent soil may be safely assumed to be 0.4 If you have questions, please contact me. This opportunity to be of service is appreciated. Respectfully Submitted, E4htL-4 C.H.Wood, RCE10776, GTE 903 cc: 3 submitted c. n. wood we) rmsw c%VH$,~~& a- l2adw. CA am8 Page 4 of 6 File #035 09/27/89 RECOMMENDED GRADING SPECIFICATIONS for Banks Residence 2740 Argonauta Street Carlsbad, California GENERAL: C.H.Wood and ‘Soil Engineer’ are synonymous hereinafter. He shall be employed to inspect and test earthwork in accordance with these specifications, the accepted plans, and the requirements of any jurisdictive governmental agencies. He is to be allowed adequate access so that the inspections and tests may be performed. The Soil Engineer shall be appraised of schedules and any unforeseen soil conditions. Substandard conditions or workmanship, inadequate compaction, adverse weather, or deviation from the lines and grades shown on the plans, etc., shall be cause for the soil engineer to either stop construction until the conditions are corrected or recommend rejection of the work. Refusal to comply with these specifications or the recommendations and/or interpretations of the soils engineer will be cause for the soils engineer and/or his representative to immediately terminate his services. SOIL TEST METHODS: Maximum Density & Opt Moisture-- Density of Soil In-Place -- Soil Expansion -- Shear Strength -- Gradation & Grain Size -- Capillary Moisture Tension -- LIMITING SOIL CONDITIONS: ASTM D1557-70 ASTM D1556 or ASTM D2922 and D3017 UBC STANDARD 29-2 ASTM D3080-72 ASTM D1140-71 ASTM D2325-68 Minimum Compaction -- 90% for ‘disturbed’ soils. (Existing fill, newly placed fill, plowed ground, etc.) -- 84% for natural, undisturbed soils. -- 95% for pavement subgrade within 2’ of finish grade and pavement base course. Expansive Soils -- Expansion index exceeding 20 Insufficient fines -- Less than 40% passing the #4 sieve. Oversized Particles -- Rocks over 10” in diameter. PREPARATION OF AREAS TO RECEIVE FILL: Brush, trash, debris and detrimental soils shall be cleared from the areas to receive fill. Detrimental soils (including insufficiently compacted soils) shall be removed to firm competent soil. Slopes exceeding 20% should be stepped uphill with benches 10’ or greater in width. Scarify area to receive fill to 6” depth and compact. FILL MATERIAL shall contain sufficient fines. Oversized particles and excessive Page 5 of 6 File #035 09/27/SY organics are not acceptable. On-site disposition of oversized rock or expansive soils are to be at the written direction of the Soils Engineer. Select fill shall be as specified by the Soils Engineer. All fill shall be comwcted anrJ tested -* UNFORESEEN CONDITIONS: C. H. Wood assumes no responsibility for conditions which differ from those described in the applicable current reports and documents for this property. Upon termination of the soil engineers services for any reason, his fees up to the time of termination become due and payable. If it is necessary for the soils engineer to issue an unfavorable report concerning the work that he has been hired to test and inspect, the soils engineer shall not be held liable for any damages that might result from his ‘unfavorable report’. c. H. wood (@IS) 1zow41 Ckil a Geowch. Engllmer 4015 Tries* rmn Carl-. CA 92008 Page 6 of 6 -S-L-O_P E STABILITY -_---_-_-- -Call- -Pet-am&et- Symb- -Value- MM factor of safety (Fsj = 1.98 Slope ratio (Br) = 2.00 :l Vertical slope height (till) = 10.0 ' Cohesion intercept (CO) = 120.0 psf Internal friction Groundwater height I;,'; ; 36.0 cieg Submergence height (HWj = ::: ' Soil dry densjty (Yd) = 111.0 pcf Specific Gravity (Gsj = 2.67 Surcharge atop slope (Qd) = 0 psf Consolidation w/r surchg (Es) = 100.0 % Dry tension crack depth (Td) = 0.0 ' Wet tension crack depth (Tw) q 0.0 ' % seismic (for Fs only) (Gv) = 0.0 % Press tU>p, cD>own, cR>evise. <C>alc, tM>atrix, cQ>uit 'JANBU/BAS' -Calc- cc;: <<:= <<;= <<;= <<=z <<3: I : 0 0 : e ; 19.00 t + + + H I e : 1: -XL --y___ 2.295 5.000 2.041 9.000 1.816 13.000 1.663 11.000 I.630 21.000 1.434 26.000 h 14.00 t 1 + + i / I + t : 9.00 t t t + t 5.00 ________;___ ---___ fector Safetr- --_--- / -----_---; 2.30 2.11 1.95 1.18 1.61 1.13 MER) to continue. ” c. H. wood (*to) 720-8811 Clv’l~,~~ E$gnw wr,*sd. CA ozcee