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HomeMy WebLinkAboutParcel Map 13428 Parcel C Soils Report MGP 170 North Maple Street, Suite 108 Corona, CA 92880 www.altageotechnical.com LINFIELD CHRISTIAN SCHOOL January 21, 2025 31950 Pauba Road Project No. 1-0155-B Temecula, California 92592 Attention: Mr. Marc Horton Subject: UPDATED GEOTECHNICAL REPORT Linfield Way Extension and Mass Grading Area, City of Temecula, California References: See Appendix A. Dear Mr. Horton: Presented herein is Alta California Geotechnical Inc.’s (Alta) updated geotechnical report for the proposed Linfield Way extension and associated mass grading, located in the City of Temecula, California. This letter is based on a review of the mass grading plans, the precise grading plans, and the referenced reports. 1.0 PREVIOUS INVESTIGATION Alta conducted a geotechnical investigation of the Linfield Property, Tract 36098-1, Parcels 1 through 3 and Tract 36098-2, Parcel 1 in 2015 consisting of the excavation, logging, and sampling of five (5) bucket-auger borings, fifteen (15) backhoe test pits, and associated laboratory testing (Alta, 2015). The proposed development at that time consisted of mixed-use and residential construction. Locations of test pits and borings within the proposed development are shown on Plates 1 through 3, and their logs are presented in Appendix B. APPROVED BY CITY OF TEMECULA PUBLIC WORKS david.pina 01/31/2025 01/31/2025 01/31/2025 01/31/20 Project Number 1-0155-B Page 2 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 2.0 PROPOSED DEVELOPMENT Based on a review of the plans and our discussions with you, the proposed development consists of extending Linfield Way north to Rancho Vista Road. As part of the proposed work, mass grading efforts will create a stockpile for future use. It is anticipated that conventional cut/fill grading techniques will be utilized in site development. Recommendations pertaining to the mass grading and street improvements are included herein. 3.0 GEOLOGIC CONDITIONS 3.1 Stratigraphy Based on Alta’s review of geologic literature and the previous subsurface investigation the project site is underlain by surficial units of artificial fill, topsoil, and alluvium. Underlying these surficial deposits is the Pleistocene- aged Pauba Formation. The approximate distribution of the geologic units are shown on Plates 1 through 3. The following is a brief description of these geologic units in order of oldest to youngest. 3.1.1 Pauba Formation (Map Symbol Qp) The Pauba Formation, which consists of early Pleistocene-aged deposits, underly the site. The Pauba Formation observed onsite consists primarily of reddish brown, fine grained clayey sands in a moist, dense condition. Bedding is massive with horizontal, gradational contacts. Project Number 1-0155-B Page 3 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 3.1.2 Alluvium (Map symbol Qal) Holocene-aged alluvium was encountered during our previous investigation primarily within south-flowing drainage areas. The alluvium within the areas of the proposed development are estimated to range approximately 2.5 to 6 feet thick. The alluvium generally consists of brown silty and clayey sands in a moist, loose to medium dense condition. 3.1.3 Topsoil (no map symbol) Relatively thin topsoil blankets most of the site. It consists primarily of brown to yellowish brown silty and clayey sands in a moist, loose to medium dense condition. The average thickness of the topsoil is approximately one (1) foot. 3.1.4 Artificial Fill (Map symbol af) Artificial fill exists primarily within areas recently used as overflow parking; however artificial fill is anticipated to be encountered within the approximate area previously occupied by a single-family home. The artificial fill consists primarily of yellowish brown silty sands in a moist, loose condition. 4.0 MASS GRADING AND STOCKPILE As previously mentioned, mass grading efforts will create a temporary stockpile of soils to be utilized or sold. In preparing the recommendations presented herein, Alta reviewed the mass grading plan prepared by KWC Engineers (Plate 1). Project Number 1-0155-B Page 4 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 4.1 Site Preparation A significant amount of vegetation, debris, and all other deleterious materials should be removed from the proposed stockpile area prior to stockpile operation. 4.2 Fill Placement As presented on the mass grading plans, an initial estimate of 10,889 CY will be stockpiled. It is our understanding that the soils will be placed as uncompacted, non-certified fill within the limits presented on Plate 1. Gently sloped (5:1) fill slopes are proposed along the south side of the stockpile area. As an erosion mitigation strategy, the faces of the proposed slope should be “track-walked” or otherwise compacted. Additional erosion mitigation strategies may include planting, hydro-seeding, and jute netting. 5.0 STREET IMPROVEMENTS The proposed Linfield Way extension consists of rough grading, curb and gutter, and asphalt paving operations. Based on a review of the precise grading plans (Plate 2 and 3), the majority of the proposed Linfield Way extension is in cut. The approximate maximum amount of cut is approximately 16-feet, in the vicinity of Finish Surface 1212.19. Minor amounts of fill are proposed, on the order of approximately 5 feet. Fill slopes on the order of 12 feet tall and cut slopes on the order of 15 feet tall are proposed to support the Linfield Way Extension. 5.1 General Earthwork Recommendations All grading shall be accomplished under the observation and testing of the project geotechnical consultant in accordance with the recommendations contained herein and the City of Temecula criteria. Project Number 1-0155-B Page 5 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 5.1.1 Site Preparation Vegetation, construction debris, and other deleterious materials are unsuitable as structural fill material and should be disposed of offsite prior to commencing grading/construction. Any septic tanks, seepage pits or wells should be abandoned as per the County of Riverside Department of Health Services. 5.1.2 Unsuitable Soil Removals For fill areas underlain by Pauba Formation, removal and recompaction of the upper two (2) feet is recommended. For cuts greater than two (2) feet in street areas, removals are not required. For cuts less than two (2) feet, the two (2) foot removal and recompaction applies. For fill areas underlain by alluvium, the alluvium shall be removed to expose competent Pauba Formation. It is anticipated that removals will range between approximately 2.5 to 6 feet in depth within alluvial areas. Based on a review of the precise grading plans, the proposed fill slope is underlain by Pauba Formation. The upper one (1) to three (3) feet of the Pauba Formation are highly weathered and therefore not suitable for the support of compacted fill. As such, this material should be removed and recompacted to project specifications prior to the placement of engineered fill. Material removed as part of the unsuitable soil removals can be used as artificial fill, provided it is free of deleterious materials. 5.1.3 Compaction Standards All fill and processed natural ground shall be compacted to a minimum relative compaction of 90 percent, as determined by ASTM Test Method: Project Number 1-0155-B Page 6 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. D-1557. Fill placed within the upper 1-foot of proposed subgrade shall be compacted to a minimum 95%, as determined by ASTM Test Method: D- 1557. Fill material should be moisture conditioned to optimum moisture or above. Compaction shall be achieved with the use of sheepsfoot rollers or similar kneading type equipment. Mixing and moisture conditioning will be required in order to achieve the recommended moisture conditions. 5.1.4 Documentation of Removals All removal/over-excavation bottoms should be observed and approved by the project Geotechnical Consultant prior to fill placement. Consideration should be given to surveying the removal bottoms and undercuts after approval by the geotechnical consultant and prior to the placement of fill. Staking should be provided in order to verify undercut locations and depths. 5.1.5 Treatment of Removal Bottoms At the completion of removals/over-excavation, the exposed removal bottom should be ripped to a minimum depth of eight (8) inches, moisture-conditioned to above optimum moisture content and compacted in-place to the project standards. 5.1.6 Fill Placement After removals, scarification, and compaction of in-place materials are completed, additional fill may be placed. Fill should be placed in eight- inch bulk maximum lifts, moisture conditioned to optimum moisture Project Number 1-0155-B Page 7 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. content or above, compacted and tested as grading/construction progresses until final grades are attained. 5.2 Slope Construction 5.2.1 Fill Slope Construction Fill slopes should be overfilled to an extent determined by the contractor, but not less than two (2) feet measured perpendicular to the slope face, so that when trimmed back to the compacted core a minimum 90 percent relative compaction is achieved. Compaction of each fill lift should extend out to the temporary slope face. Back-rolling during mass filling at intervals not exceeding four (4) feet in height is recommended, unless more extensive overfilling is undertaken. As an alternative to overfilling, fill slopes may be built to the finish slope face in accordance with the following recommendations: 1. Compaction of each fill lift should extend to the face of the slopes. 2. Back-rolling during mass grading should be undertaken at intervals not exceeding four (4) feet in height. Back-rolling at more frequent intervals may be required. 3. Care should be taken to avoid spillage of loose materials down the face of any slopes during grading. Spill fill will require complete removal prior to compaction, shaping, and grid rolling. 4. At completion of mass filling, the slope surface should be watered, shaped, and compacted by track walking with a D-8 bulldozer, or equivalent, such that compaction to project standards is achieved to the slope face. Project Number 1-0155-B Page 8 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. Proper seeding and planting of the slopes should follow as soon as practical to inhibit erosion and deterioration of the slope surfaces. Proper moisture control will enhance the long-term stability of the finish slope surface. 5.3 Slope Stability 5.3.1 Fill Slopes It is anticipated that the proposed fill slope will be designed at a slope ratio of 3:1 (horizontal:vertical) or flatter to vertical heights of up to approximately 12-feet. Fill slopes, when properly constructed with onsite materials, are expected to be grossly stable as designed. Skin-fill slope conditions should be avoided. If these conditions exist or are created during grading, they should be evaluated. Typical remediation for skin fill conditions are shown on Plate G-11 (Appendix D). 5.3.2 Cut Slopes It is anticipated that the proposed cut slopes will be designed at slope ratio of 3:1 (horizontal:vertical) or flatter to vertical heights of up to approximately 15-feet. Alta anticipates that cut slopes will primarily be excavated in the Pauba Formation. Upon exposing competent Pauba Formation, the cut slopes are expected to be grossly stable as designed. All cut slopes should be observed during grading by the Project Geotechnical Consultant. If adverse bedding, fracture or joint patterns, or other unstable geological conditions are exposed, then cut slopes may need to be replaced with a drained stabilization fill, as generally depicted on Plates G-8, G-9 and G-10 in Appendix D. Project Number 1-0155-B Page 9 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 5.4 Preliminary Pavement Design Recommendations The design recommendations presented herein are based on an assumed R- Value and Traffic Index for the proposed extension. Preliminarily, based on an assumed R-value of 25, the pavement may be designed utilizing the sections presented in Table 4-1. These sections should be verified upon the completion of grading, based on R-value testing. The ultimate pavement section design for public streets is under the City of Temecula’s purview. Table 4-1 Preliminary Pavement Sections Traffic Index Pavement Section Options 6.0 4.0 inches AC over 7.5 inches AB AC-Asphalt Concrete AB-Caltrans Class II Base Construction of the streets should be accomplished in accordance with the current criteria of the City of Temecula. Prior to the placement of base material, the subgrade should be suitably moisture conditioned, processed and compacted to a minimum 95 percent of the laboratory maximum density (ASTM: D 1557) to at least twelve (12) inches below subgrade. After subgrade compaction, the exposed grade should then be "proof"-rolled with heavy equipment to ensure the grade does not "pump" and is verified as non-yielding. Aggregate base material should be placed on the compacted subgrade and compacted in-place to a minimum 95 percent of the laboratory standard obtained per ASTM: D 1557. 5.5 Utility Trenches Based on a review of the precise grading plans, storm drain / drainage improvements are proposed along the intersection of the proposed Linfield Way extension and Rancho Vista Road. Project Number 1-0155-B Page 10 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 5.5.1 Excavation Utility trenches should be supported, either by laying back excavations or shoring, in accordance with applicable OSHA standards. The existing site soils are classified as Soil Types "B" and “C” per OSHA standards. Upon completion of the recommended removals and recompaction, the artificial fill will be classified as Soil Type “B”. The Project Geotechnical Consulting should be consulted if geologic conditions vary from what is presented in this report. 5.5.2 Backfill Trench backfill should be compacted to at least 90 percent of maximum dry density as determined by ASTM D-1557. Onsite soils will not be suitable for use as bedding material but will be suitable for use in backfill provided oversized materials are removed. No surcharge loads should be imposed above excavations. This includes spoil piles, lumber, concrete trucks, or other construction materials and equipment. Drainage above excavations should be directed away from the banks. Care should be taken to avoid saturation of the soils. Compaction should be accomplished by mechanical means. Jetting of native soils will not be acceptable. 5.6 Exterior Slabs and Walkways Exterior concrete slabs and walkways should be designed and constructed in consideration of the following recommendations. Project Number 1-0155-B Page 11 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 5.6.1 Subgrade Compaction The subgrade below exterior concrete slabs should be compacted to a minimum of 90 percent relative compaction as determined by ASTM Test Method: D 1557. Per City of Temecula Standard No. 200, the subgrade below curb and gutter should be suitably moisture conditioned, processed and compacted to a minimum 95 percent relative compaction. 5.6.2 Subgrade Moisture The subgrade below concrete slabs should be moisture conditioned to a minimum of 110 percent of optimum moisture prior to concrete placement for areas with very low to low expansion potential, and 120 percent of optimum moisture content prior to concrete placement for areas with medium expansion potential. 5.6.3 Concrete Slab Thickness Concrete flatwork and driveways should be designed utilizing four-inch minimum thickness. 5.6.4 Concrete Slab Reinforcement Utilization of reinforcement for flatwork and driveways is subject to a cost/benefit analysis. Reinforcement will decrease the amount of cracking that may occur in flatwork, however, planning for occasional repairs may be more cost effective. Utilizing closely spaced control joints is likely more cost-effective than utilizing reinforcement. The majority of the soils onsite are classified as very low in expansion potential. Consideration should be given to reinforcing flatwork with irregular (non- square/rectangular) shapes. Project Number 1-0155-B Page 12 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. 5.6.5 Control Joints Weakened plane joints should be installed on walkways at intervals of approximately eight feet (maximum) or less. Exterior slabs should be designed to withstand shrinkage of the concrete. 5.7 Concrete Design As stated in Alta, 2015, negligible concentrations of sulfates were detected in the onsite soils (Class S0). Therefore, the use of sulfate resistant concrete is not required per ACI 318-14 at this time. Post-grading conditions should be evaluated, and final recommendations made at that time. Alta California Geotechnical, Inc., appreciates the opportunity to be of service to you and your organization. Should you have any questions or need additional information, please contact the undersigned at (951) 509-7090. Respectfully submitted, Alta California Geotechnical, Inc. _______________________________ LOGAN A. MARQUETTE Civil Engineering Associate _______________________________ SCOTT A. GRAY/RGE 2857 Reg. Exp.: 12-31-26 Registered Geotechnical Engineer President Distribution: (1) Addressee SAG: 1-0155-B, January 21, 2025 (Updated Geotechnical Report, Linfield Way Extension, Temecula) ALTA CALIFORNIA GEOTECHNICAL, INC. APPENDIX A REFERENCES Project Number 1-0155-B Page A-1 January 21, 2025 ALTA CALIFORNIA GEOTECHNICAL, INC. APPENDIX A Selected References Alta California Geotechnical, Inc., 2017, Updated Preliminary Pavement Design Recommendations, Linfield Village, APN 955-020-006, City of Temecula, California, dated November 10, 2017 (Project No. 1-0155-A). Alta California Geotechnical, Inc., 2015, Geotechnical Investigation, Linfield Property, Tract 36098-1, Parcels 1 through 3, and Tract 36098-2, Parcel 1, City of Temecula, California, dated June 15, 2015 (Project No. 1-0155-A). ALTA CALIFORNIA GEOTECHNICAL, INC. APPENDIX B PREVIOUS SUBSURFACE INVESTIGATION (ALTA, 2015) UNIFIED SOI L CLASSIFIICATION SYSTEM Major Divisions lfl tr Description Major Divisions an tr Coarse Grained Soils N4ore than 50% retained on No 200 steve Gravel and Sravelly Soils han 50% frachon relained on No, 4 'l ts* ,-l* EIF GW Well-graded grcvels or gravel sand mixtures, little or no fines Fine (lrained isoils l\lore than Silts And Clays LL,<50 n ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clavev silts with slioht olasticitv GP Poorly-graded gravels or gravel sand mixture, little or no fines CL Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean claysSilty gravels, gravel-sand-silt mixtures OL Organic silts and organic silt-clays of low plasticity Clayey gravels, gravel-sand-clay mixtures Silts And Clays LL,<50 MF Inorganic silts, micaceous or diatomaceous fine or silty soils, elastic siltsSand and Sandy Soils than 50% fraclion Passes on No, 4 i'+. 3_'.JV! Well-graded sands or gravelly sands, little or no fines on No 200 steve VH Inorganic clays of high plasticity, fat claysSP Poorly-graded sands or gravelly sands, little or no fines SM Silty sands, sarrd-silt mixtures OF Organic clays of medium to high plasticity sc Clayey sands, and-clay mixtures Highly Organic Soils PT Peat and other highly organic soils BoUNDARY CLASSIFICATIoN: Soils possessing characteristics of two groups are designated by combinations of group symbols PARTICLE SIZ:E LIMITS U.S. STANDA,RD SiERIES SIEVE 200 40 10 4 CLEAR SQUARE SIEVE OPENINGS 3t4" 3,, ,t2" LABORATORY TESTS Symbol Tesl DS DSR cc)N SA MAX RV EI SE AL CHEM HY Direct Shear Direct Shear (Remolded) Sieve Analysis Maximum Density Resistance (R) Value Expansion Index Sand Equivalent Atterberg Limits Chemical Analysis Hydrometer Analysis SOIL MOISTURE SIZE PROPORTIONS Trace - <5% Few-5to10% Some - 15 to 25% Increasing \/isual Moisture Content Silts an0 Clays Sand Gravel Cobbles Boulders Fine Medium Coarsi€r Fine Coarse RELATIVE DENSITY Sands and Gravels Blows/Foot (SPT) Very Loose Loose Medium Dense Dense Very Dense <4 4-10 11-30 31 -50 >50 CON SI STENCY C IASSI FI CATI ON Silts and Clays Criteria Very Soft Soft Firm stiff Very Stiff Thumb penetrates soil >1 in. Thumb penetrates soil 1 in, Thumb penetrates soil 1/4 in Readily indented with thumbnail Thumbnail will not indent soil HARDNESS KEY TO EXPLORATORY BORING LOGS} ,n /L>//J, ALTA CALIFORNTA GEOTECHNTCAL tNC. /\ PI-ATE B ALTA CALIFORNIA GEOTECHNICAL, INC. APPENDIX C EARTHWORK SPECIFICATIONS ALTA CALIFORNIA GEOTECHNICAL, INC. APPENDIX D GRADING DETAILS Qp Qp Qp af Qal Qal af (Qal) af (Qal) T-19 af (Qp) af (Qp) B-5 0-1.5' Topsoil 1.5-31' Qp T.D. = 31' No G.W. 0-2.5' Qal 2.5-4.5' Qp T.D. = 4.5' No G.W. T-21 0-6' Qal 6-8' Qp T.D. = 8' No G.W. T-18 0-2.5' Qp T.D. = 2.5' No G.W. 170 N. MAPLE STREET, STE 108, CORONA, CA 92880 TELEPHONE: (951) 509-7090 ALTA CALIFORNIA GEOTECHNICAL, INC. LEGEND ARTIFICIAL FILL ALLUVIUM (BRACKETED WHERE BURIED) PAUBA FORMATION (BRACKETED WHERE BURIED) APPROXIMATE LOCATION OF GEOLOGIC CONTACT (DOTTED WHERE BURIED) APPROXIMATE LOCATION OF BACKHOE TEST PIT (ALTA, 2015) APPROXIMATE LOCATION OF BORING (ALTA, 2015) af Qal PLATE 1 T-19 Qp B-5 Qp Qp af (Qp) af (Qal) Qal Qal 0-2.5' Qal 2.5-4.5' Qp T.D. = 4.5' No G.W. T-21 170 N. MAPLE STREET, STE 108, CORONA, CA 92880 TELEPHONE: (951) 509-7090 ALTA CALIFORNIA GEOTECHNICAL, INC. PLATE 2See Plate 1 for Legend Qp Qp af B-5 0-1.5' Topsoil 1.5-31' Qp T.D. = 31' T.E. No G.W. 170 N. MAPLE STREET, STE 108, CORONA, CA 92880 TELEPHONE: (951) 509-7090 ALTA CALIFORNIA GEOTECHNICAL, INC. PLATE 3See Plate 1 for Legend