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HomeMy WebLinkAboutPD 2019-0032; GOERTZEN RESIDENCE; GEOTECHNICAL RESPONSE TO THIRD PARTY 1ST REVIEW; 2019-12-19'I-• :,._ jlH, TllnEII------------------------~------ December19, 2019 P.O. Box 119E Lakeside, Califorrtfa . 9204( Greg Goertzen 3466 Camino Michelle Carlsbad, California 92009 SUBJECT: File No. 1127H6-19 SITE INSPECTION Response to Third Party Geotechnical Review Proposed Residential Building Site El Fuerte Street and Acuna Court City of Carlsbad Dear Mr. Goertzen: In response to the third party review by Hetherington Engineering, dated October 3, 2019. 1. The consultant should review the project grading plan and foundation plans. We have reviewed the grading plan for Lot 84-El Fuerte Street by Pasco Laret Suiter & Associates, dated February 15, 2017, Drawing No. 520-8A (sheets 1 through 5) and find it confonns to the recommendations in our Site Inspection dated June 7, 2019. We have not been provided with the structural or architectural plans. 2. The consultant should provide a geotechnical map/plot plan utilizing the latest grading plan. Please see Plate IV and V attached. 3. The consultant should provide a geotechnical cross section. Please see Plate VI attached. 4. The consultant should provide a detailed description of the proposed site grading, structures/improvements, foundation type. The proposed grading is a cut/fill to create a 17 foot high 2: 1 fill slope to create a level building pad for the single family structure with a slab on grade construction. There will be a 2 to 3 foot retaining wall at the base of slope on north side of the site. I ~T,'i~~~.,,,. r~p.., rli ""' ~ . .., '•·..... ;; . t, ·~ .. • _ _,_:· LA1\,Ji'.) Dt:VELOPMENT . Ei\lGINEERING. (619) 443-006( ' . Greg Goertz File No. 1127H6-19 December 19, 2019 5. The consultant should discuss regional geologic conditions, geologic structure and faulting. The site is underlain with Mesozoic volcanic and metavolcanics structure. No known faulting in located in the area of the site .. 6. The consultant should provide a statement regarding the impact of the proposed grading and construction on adjacent properties and improvements. The proposed grading and construction should have no impact on adjacent properties and improvements. 7. The consultant should provide a description of approved foundation embedment materials. The foundation for the proposed structures should be founded a minimum of 18 inches into the fill soils compacted to 90 percent compaction. The proposed structures and other improvements should be located at least 7 from the top of compacted fill slopes. If proposed foundations and footings are located closer than 7 feet inside the top of compacted fill slopes, then must be deepened so that the face of footing at the elevation of the bottom is at least 7 feet back from the face of slope at that level. 8. The consultant should address expected total and differential settlement due to foundation loads. The estimated maximum values for the Total Settlement is 1 inch and for the Differential Settlement is 1/2 inch. 9. The consultant should provide hardscape recommendations (thickness, reinforcement, joints etc.). Recommendation of Portland Cement Concrete Pavement Section: (For Mechanical Equipment Utility Pad, Loading Slab) • Design Daily ESALs : 18 • Concrete Thickness = 6 inches with #4 deformed rebar @ 12" on center (O.C.) each way (E.W.) or 4.5 inches of asphalt. • Type II Aggregate Base = 6 inches (Compacted to 95 % of relative compaction) 2 '. ' . Greg Goertz File No. 1127H6-19 December 19, 2019 • Concrete tnix design: Type V Cement, Water/Cement Ratio, Max W/C, = 0.45, 28 days compressive strength = 4500 psi. Special Inspection not required. • Scarify the existing sub-base soil 12" and compacted to 95% or greater. • Slab Contraction Joint: Control Joint: Sawcut ¼ of slab thickness @ plus, minus 6' O.C. Expansion joint: @ the maximum of 24' plus · and minus O. C. with 1" diameter x 18" length smooth dowel @ 12" O.C. with 9" into each side of joint, with one fixed one with grease or wrapped with plastic for debond and temperature movement. Place½" expansion joint filler alone the joint. 10, The consultant should specify the sulfate exposure category (ACI 318) based on soluble sulfate testing and provide recommendations for sulfate resistant concrete if necessary. Sulfate testing was not required. We can provide this testing during the grading operation if necessary. · 11. The consultant should provide a list of recommended observation and testing during site grading. Please see our previously referenced report under Recommended Grading Specifications. 12. The consultant should provide the site seismic design category. Please see our report, page 2, #3 for seismic category D. 13. The foundation and slab design criteria for soils should be consistent with Section 1808.6 ofthe2016 California Building Code. The foundation and slab recommendations in our previously referenced report are consistent with Section 1808.6 of the 2016 California Building Code for moderately expansive soils (EI 65). 14. the consultant should provide a location map. See Plate I. 15. The consultant should provide the test exploration logs. See Plate II through III 3 Greg Goertz File No. 1127H6-19 December 19, 2019 16. The consultant should discuss potential geologic hazards including landslides, slope instability, liquefaction, tsunami potential, etc. The subject site is located approximately 7 miles from the nearest known fault (Rose Canyon Fault) and is not within a City designated fault zone or State of California Designated Alquist-Priolo Earthquake Fault Studies Zone. No known active faults underlie the site. Fault movement beneath the proposed improvements is considered to be low. During our on site visit, no visual seismic fissures were observed. The subject site is approximately 4 miles from the Pacific Ocean and approximately 360 feet above mean sea level. According to McCulloch (1985) the potential in the San Diego County coastal area for 100 year and 500 year tsunami waves is approximately five and eight feet or less. This suggests that there is a low probability of a tsunami reaching the site based on elevation above sea level. Based on the location of the site, elevation above sea level, no ground water encountered and the soil type it is our opinion the potential for liquefaction is considered to be negligible. " Reference to the geologic and Landslide Hazard Identification Map of the Rancho Santa Fe Quadrangle Tan (1986) indicates that the property is a marginally susceptible area. Based on the 8 percent grade, it is our professional opinion that landslide potential is negligible. 17. The consultant should provide a statement as to the feasibility of the project. We conclude that the proposed development of the site is feasible from a geotechnical standpoint provided· the recommendations in this report are incorporated into the design and construction of the project. 18. The consultant should provide a statement with respect to the stability of the slopes. The natural slope of the property is approximately 30 feet high with an 8 percent degree of inclination from the northeast to southwest.. This site demonstrates that inactions of 1.5: 1 (H: V) or flatter. No visual evidence of slope disturbance was noted at the time of our inspection of the site. Based on our experience with similar conditions, the slope, which is comprised of dense, very old volcanic and sedimentary rock, will demonstrate a minimum factor of safety against deep seated failures in excess 1.5. The proposed grading with the 2:1 slopes for the proposed construction will not significantly affect the overall stability of the slope or subject site. 4 Greg Goertz File No. 1127H6-19 December 19, 2019 19. The consultant should clarify remedial grading recommendations. Please see the Recommended Grading Specincations in our report in addition to the following: The cut portion of the cut/fill transition shall be undercut and over-excavated to a minimum of 3 feet in depth from finish grade. There should be a minimum of 12 inches of uniformly compacted fill under the proposed footings. Utility trench backfill beneath structures, pavements and hardscape should be a SE 30 soil or less and compacted to a minimum of 90% relative compaction. The upper 12 inches of subgrade beneath slabs and paved areas should be compacted to al least 95% relative compaction. Any organic or other deleterious material that may be encountered should be removed prior to recompaction. All graded fill slopes should be graded to a maximum of a 2: 1 gradient. Graded cut slopes will be stable at a 1.5:1 gradient 20. The consultant should provide recommendations for temporary excavations. There are no temporary excavations. 21. The consultant should provide recommendations for foundation slope setback. The proposed improvements meet the foundation slope setback. r/ l:'ur SI: I foot= 304.8 mm. FACE OF STRUCTURE TbPOF FACE OF FOOTING SLOPE ---------1-~,..,...,.-'----';- --~ H AT LEAST THE SMALLER OF H/3 AND 40 FEET . AT LEAST THE SMALLER OF Hl2 AND 15 FEET FIGURE 1808.7.1 FOUNDATION CLEARANCES FROM SLOPES 22. The consultant should provide retaining wall recommendations, if necessary. The proposed retaining wall is approximately 2 to 3 feet in height and is considered a landscape wall. 5 Greg Goertz File No. 1127H6-19 December 19, 2019 23. The consultant should provide a list of references utilized in the preparation of the report. Please see reference sheet attached. If we can be of any further assistance, please do not hesitate to contact our office. This opportunity to be of service is sincerely appreciated. Respectfully submitted, Chin C. Chen, RPE C34442 CCC/mlj 6 CITY OF OCEANSIDE PACIFIC OCEAN 78 VICINITY MAP PLATE I CITY OF ENCINITAS 1127H6-19 12-30-19 CITY OF VISTA TY OF N MARCOS ~ NO SCALE~ P.O. Box 1195 Lakeside, CA 92040 619-443-0060 ' Greg Goertz Plate No. II EXPLORATION NUMBER 1 Date Logged: Date Reported: n th U •fi d Cl ep, m ~e 0 to 6" SM 6 to 30" SC 05/02/19 11/29/19 'fi a.ss1 1cations Red brown, lawn roots Red brown, File No. 1127H6-19 December 19, 2019 Equipment Used: Hand dug Groundwater: Not Encountered 01 . escnpt10n S 'ID S ·1 T 01 ype dry, loose, SILiYSANDS (Topsoils) dry, dense, SIL iY CLAYEY SANDS 1 with some decomposed granite (Native) •J 30 to 48" SM Yellow tan, dry, dense, SILTY SANDS (Native) I , bottottt of excavation Greg Goertz Plate No. III EXPLORATION NUMBER 2 Date Logged: Date Reported: 05/02/19 11/29/19 D th U 'fi d Cl 'fi f ep Ill Je ~SSl 1ca lOilS 0 to 5" SM Dark brown, lawn roots 5 to 16" SM Light brown, with some clay 16 to 48" SM Orange brown, with some clay -------------·-·· --· ---· -· --· ·------ .. File No. 1127H6-19 Equipment Used: Groundwater: o.i escnp 10n S 'ID . f dry, loose, dry, firm to dense, dry, dense, --------------··--·------------·--::- bottom of ex9avation December 19, 2019 .Hand dug Not Encountered 01 ype SILTY SANDS (Topso.ils) SILTY SANDS (Native) SILTY SANDS (Native) ---------------- ' ' . 3'SLOPE· I I I I I I I I I 1 I L_ _ ____ _,___ --SIDEWALK ---- EL FUERTE STREET ~ · EXPLORATION TRENCH -=-RETAINING WALL II._ PROPOSED TOP OF SLOPE . . PROPOSED TOE OF SLOPE .~ EXISTING TOPOGRAPHY LOCATION OF EXPLORATION TRENCHES ~1tftf!i11itltkf4~li&\U.&11!~.~~t:t{;tfttrii 1127H6-19 JRK PLATE IV :),/:··;;::i;~,:,·,:.'3:·:::>:,:>]:iA'ir'.~;;~::;.{,:i'.~:.1ff.ii~~·i:i:/ 12-31-19 \ I I ~ ::> 0 u <( z ::> u <( ,..., NO SCALE,..., P.O. Box 1195 Lakeside, CA 92040 619-443-0060 . ' . • GE OLO GIC MAP PLATE V SIIJff MD. " . 10 " "' lWllll!W<CI - L TESTERS LEGEND APPROXIMATE TEST TRENCH LOCATION APPROXIMATE LIMITS OF THE 5-ITE 1z ARTIFICIAL FILL OVER 11 27H6-1 S NRCS-EXCHEQUER SURFACE SOILS-, ROCKY · 5-ILT LOAM, 9-TO 30% SLOPES. JURASSIC "AND CRETACEOUS METAMORPHOSED AND UNMETAMORPH05-ED VOLCANIC AND SEDIMENTARY ROCK FORMATION LOW-GRADE METAMORPHOS-ED ROCK CONGLOMERATE, SANDSTONE, AND SILTSTONE, SURFACE DESCRIPTION, " REDDIS-H-BROWN, YELLOW-BROWN, LIGHT BROWN AND ORANGE-BROWN COARSE TO FINE SAN-D· "AS BUILT" UITER OCIATES RCO __ ""'·--OATE .INSPECTOR DATE [7JI CITJ...2!.,~~~AD IITI . lWllJIC Pl.INS" P0lt GOERTZEN RESIDENCE LOT 84 -EL FUERTE STREET 11-00JQ e+. :::::&Ljf P11<U:cr NO. I[ -~G "o1 ~ ~.1 P02011-DO.l2 . 520--M I l .~. : .I Cf l"V 0 :~ n ;c a. Vl tn V') m n -, --0 z A 370 355 · GEOLOGIC SEClJON· A -A GOERTZEN RESIDENCE LOT -84, Et FUERTE STREET CARLS6AD, CALlFORNIA L•:.•· '.'::J Approximate limits of q9eumentec;tgradin9 ,an during s-tteet improvements . Muz Metamorphosed andunmetamo.r:phosed Vdkanic ~nd sedtmenta.ryrock formati.on, Redcbrown to Light . btown·sandstone and rock congtomerate BEST IMAGE ~ POSSIBLE t •• ' Greg Goertz File No. 1127H6-19 December 19, 2019 References Grading Plan by Pasco Laret Suiter, Project No. PD2019-0032, Drawing No. 520-8A Tan, S.S., 1986, Landslide Hazards in the Rancho Santa Fe Quadrangle, San Diego County, California Landslide Hazard Identification Map No. 6, OFR 86-15 -LA NRCS Soil Resource Report Geologic Map of the San Diego 30'x60' Quadrangle, California Hart, 1994, Fault-Rupture Hazard Zones in California, Earthwork Fault Zoning Act with Index to Earthquake Fault Zones Maps: California Division of Mines and geology, Special Publication 42,33 p.