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HomeMy WebLinkAboutE2016-0337 - SoilsCOAST GEOTECHNICAL, INC. 1200 W. Commonwealth Avenue, Fullerton, CA 92833 * Ph: (714) 870-1211 * Fax: (714) 870-1222 * E-mail: coastgeotec@sbcglobal.net October 15, 2019 Mr. and Mrs. John Manly 2612 Mesa Drive Newport Beach, CA 92660 References: W.O. 557918-03 Subject: Rough Grade Compaction Report for Additions at 2612 Mesa Drive, Newport Beach, California Geotechnical Engineering Investigation of Proposed Additions, 2612 Mesa Drive, Newport Beach, California; by COAST GEOTECIINICAL, INC., W.O. 557918-01, dated August 21, 2018. Response to Geotechnical Newport Beach, California December 5, 2018. Dear Mr. & Mrs. Manly: Report Review for Proposed Additions at 2612 Mesa Drive, by COAST GEOTECBNICAL, INC., W.O. 557918-02, dated Forwarded herewith is the rough grade compaction report for the subject site. Our observations and testing were performed periodically, as requested. The grading operation for the residential development consisted of grading the pad area to provide uniformly compacted fill soils for support of the residence. The grading operation was conducted from October 7, 2019 through October 11, 2019. PLACEMENT OF FILL Compacted fill material was placed to provide adequate support for the proposed structure. The over -excavation of the building pad area extended into competent native material. The depth of over -excavation was approximately three to five feet below the original grade. The proposed finish grade varies from two feet above to two feet below original grade. The exposed surface was scarified, moisture conditioned, and compacted to a minimum of 90% relative compaction. Subsequent fills were placed in six to eight inch loose lifts, moisture conditioned as needed, and compacted to a minimum of 90% relative compaction by track rolling. This process was followed to finish grade. Hardscape areas outside the building pad were over -excavated about 12 inches and recompacted to final grade to a minimum of 90% relative compaction. The driveway area was only partially graded. The remainder of the driveway will be graded at a later date. Limits of grading are shown on the attached Plate 1. COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 2 W.O. 557918-01 Rough Grade Compaction Report October 15, 2019 Equipment used for the compaction of fill soils consisted of a Cat 953 track loader. Soils were moisture conditioned by a water hose. Earthwork was by JD Demolition & Grading. TESTING Maximum density optimum moisture relationship determinations were performed for each soil type encountered during grading operations. Test results were as follows: Laboratory Standard: (ASTM:D-1557) 4-inch diameter mold; 1/30 ft3 volume; 5 layers at 25 blows per layer; 10 lb. hammer dropped 18 inches Soil Type Classification Optimum Moisture, % Max. Dry Density, lbs/ft3 1 Orange Brown Silty Clayey 9.5 125.0 Sand II Orange Brown Silty Clayey 9.0 127.0 Sand Compaction tests were performed a minimum of every two feet and/or 500 cubic yards of compacted fill soils placed. These tests were performed in accordance with an ASTM test method. The test results are summarized in Table 1. The approximate test locations are shown on Plate 1. FOUNDATIONS IN COMPACTED FILL The proposed additions may be supported by conventional foundations system deriving support from new engineered fill soil where feasible. Conventional foundations may consist of spread footings or isolated pads placed a minimum depth of 24 inches below lowest adjacent grade utilizing an allowable bearing value of 1,800 pounds per square foot. This value is for dead plus live load and may be increased 1/3 for total including seismic and wind loads where allowed by code. The footing width shall be at least 15 inches for the proposed two-story addition. Isolated pad footings shall be tied by grade beams to continuous footings. It is recommended that all footings be reinforced with a minimum of four #5 bars (two top and two bottom). The structural engineer's reinforcing requirements should be followed if more stringent. Footing excavations shall be observed by a representative of COAST GEOTECHNICAL, Inc., prior to placement of steel or concrete to verify competent soil conditions. If unacceptable soil conditions are exposed mitigation will be recommended. COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 3 W.O. 557918-01 Rough Grade Compaction Report October 15. 2019 FOUNDATIONS INTO COMPETENT NATIVE EARTH MATERIAL Where grading is not performed new foundations may be supported by competent native earth material utilizing the following design. Continuous footings placed a minimum of 12 inches into competent native earth material and at least 24 inches below lowest adjacent grade, whichever is deeper, may utilize an allowable bearing value of 1,800 psf. This value is for dead plus live load and may be increased by 1/3 for total including seismic and wind loads where allowed by code. Isolated pads placed a minimum of 12 inches into competent native earth material and at least 24 inches below lowest adjacent grade, whichever is deeper, may utilize an allowable bearing value of 1,800 psf This value is for dead plus live load and may be increased by 1/3 for total including seismic and wind loads where allowed by code. Isolated pads shall be tied into adjacent foundations with designed grade beams in at least two directions. Minimum geotechnical reinforcement of foundations shall be four #5 bars, two top and two bottom. Structural design may require additional reinforcement. Foundation excavations shall be observed by the project soil engineer to verify embedment requirements into competent earth material and compliance with project geotechnical requirements. Dependent on conditions exposed the project soils engineer may require the foundation excavations to be extended deeper or mitigation performed. LATERAL DESIGN Lateral restraint at the base of footings and on slabs may be assumed to be the product of the dead load and a coefficient of friction of .30. Passive pressure on the face of footings may also be used to resist lateral forces. A passive pressure of zero at the surface of finished grade, increasing at the rate of 300 pounds per square foot of depth to a maximum value of 3,000 pounds per square foot, may be used for compacted fill and native soils at this site. If passive pressure and friction are combined when evaluating the lateral resistance, then the value of the passive pressure should be limited to 2/3 of the values given above. EXPANSIVE SOILS Results of expansion tests indicate that the near surface soil at the completion of grading has a medium expansion potential. Irrigation should be controlled, limited and directed away from foundations. SOLUBLE SULFATES Typical on -site soils showed a soluble sulfate content of 33 ppm. This sulfate exposure is negligible. Type II concrete with minimum 2,500 psi compressive strength may be used and designed per the CBC and ACI. COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 4 W.O. 557918-01 Rough Grade Compaction Report October 15, 2019 FLOOR SLABS Where a slab on grade is utilized, the slab shall be supported on engineered fill compacted to a minimum of 90% relative compaction. Minimum geotechnical recommendations for on grade slab design are five inches actual thickness with #4 bars at twelve inches on center each way. Subgrade soil should be kept moist prior to casting the slab. However, if the soils at grade become disturbed during construction, they should be moisture conditioned to 3% to 4% over optimum moisture, and compacted to a minimum of 90% relative compaction prior to placing concrete. COAST GEOTECHNICAL, Inc. will need to verify adequate mitigation. The capillary break material shall comply with the requirements of the local jurisdiction and shall be a minimum of four inches in thickness. The city of Newport Beach requires the use of four inches of gravel (1/2-inch or larger clean aggregate). If gravels are used, a heavy filter fabric (Mirafi 140N) must be placed over the gravels prior to placement of the recommended vapor barrier to minimize puncturing of the vapor barrier. Additionally, a vibratory plate should be used over the gravels prior to placement of the recommended filter fabric to smooth out any sharp protuberances and consolidate the gravels. Slab areas should be underlain by a vapor retarder consisting of an engineered plastic film (as described by ASTM:E-1745). In areas where a moisture sensitive floor covering will be used and/or where moisture infiltration is not desirable, a vapor barrier with a permeance of less than 0.01perms (consistent with ACI 302.2R-06) such as 15 mil. Stego Wrap Vapor Barrier, or equivalent should be considered, and a qualified water proofing specialist should be consulted. The vapor barrier should be underlain by the above described capillary break materials and filter cloth. The capillary break materials should be compacted to a uniform condition prior to placement of the recommended filter cloth and vapor barrier. The vapor barrier should be properly lapped and sealed, and in contact with the slab bottom. UTILITY LINE BACKFILLS All utility line backfills, both interior and exterior, shall be compacted to a minimum of 90% relative compaction and shall require testing at a maximum of two -foot vertical intervals. Underground pipes shall be shaded with a minimum of one foot of sand. Where utility lines enter structures the utility trench shall have an impermeable plug of backfill placed to mitigate the potential migration of waters through the backfill zone underneath the slab. Utility lines shall be placed at appropriate depths. Shallow pipes can be damaged by the forces imposed by compacting backfill soils. If shallow pipes are not capable of withstanding the forces of backfill compaction, slurry backfill will be recommended. COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 5 W.O. 557918-01 Rough Grade Compaction Report October 15, 2019 HARDSCAPE AND SLABS Hardscape slab subgrade areas shall exhibit a minimum of 90% relative compaction and moisture content near optimum moisture content to a depth of at least one foot. Deeper removal and recompaction may be required if unacceptable conditions are encountered. These areas require testing just prior to placing concrete. The followings recommendations will minimize cracking and offsets, but will not eliminate concrete cracks. Minimum geotechnical recommendations for slab design are 4 inches actual thickness with #3 bars at twelve inches on center each way. As an alternative to rigid hardscape or brickwork, flexible pavers may be utilized. DRAINAGE Positive drainage should be planned for the site. Drainage should be directed away from structures via non -erodible conduits to suitable disposal areas. The structure should utilize roof gutters and down spouts tied directly to yard drainage. Unlined flowerbeds, planters, and lawns should not be constructed against the perimeter of the structure. If such landscaping (against the perimeter of a structure) is planned, it should be properly drained and lined or provided with an underground moisture barrier. Irrigation should be kept to a minimum. While the current CBC recommends 5% slope away from structures for landscape areas, 2% slope is allowable where justified. Our justification is the use roof drains tied into area drains, the use of area drains, and site grading which will mitigate the potential for moisture problems beneath a slab on grade. Hardscape areas shall be sloped a minimum of 2% where within ten feet of the residence unless allowed otherwise by the building official. We do not recommend the use of bottomless trench drains to conform with infiltration best management practice (BMP) such as infiltration trenches, infiltration basins, dry wells, permeable pavements or similar systems designed primarily to percolate water into the subsurface soils within ten feet of foundations. If infiltration system cannot be located away from foundations, from a geotechnical viewpoint surface drainage should be directed to the street or approved area in accordance with the Civil engineer. POST -GRADING SERVICES During construction of the residence, it is recommended, and at times required by the regulatory agency, the following be observed and/or tested by the geotechnical engineer: • Excavation of foundations • Backfill of interior trenches • Backfill of interior slab areas • Backfill of exterior utility trenches COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 6 W.O. 557918-01 Ron& Grade Compaction Report October 15 2019 Hardscape subgrade It is the responsibility of the developer to schedule the required observations and testing. REGULATORY COMPLIANCE I hereby certify that the subject grading was observed by a representative from this office, and the work was done in full compliance with the Grading Ordinance of the City of Newport Beach and in accordance with the best accepted practices of the applicable chapter of the California Building Code. All cuts, fills or processing of original ground under the purview of this report have been completed under the observation of and with selective testing by COAST GEOTECHNICAL, INC. and found to be in compliance with the Grading Code of the City of Newport Beach. The completed work has been observed by COAST GEOTECHNICAL, INC., and is considered adequate for the development. Our findings were made and recommendations prepared in accordance with generally accepted professional engineering practices, and no further warranty is implied nor made. This report is subject to review by the controlling authorities for this project. We appreciate this opportunity to be of service to you. Respectfully submitted: COAST GEOTECHNICAL, INC. Ming-Tarng Chen RCE54011 Q�p�ARNC No.54011 Exp. 12/31 /19 Darnel E. ere Staff Geologist COAST GEOTECHNICAL, INC. Mr. & Mrs. Manly 7 W.O. 557918-01 Rough Grade Compaction Report October 15, 2019 COMPACTION TEST RESULTS TABLE 1 Test No. Location Below Proposed Grade (ft) Moisture Content % Dry Unit Weight (lbs/fti) Soil Type Relative Compaction % Date 1 Pad Area 3.0-3.5 7.5 115.6 I 92.5 10/7/19 2 Pad Area 3.0-3.5 8.0 118.0 I 94.4 10/7/19 3 Pad Area 2.0-2.5 10.5 116.3 I 93.0 10/8/19 4 Pad Area 1.0-1.5 9.8 117.5 I 94.0 10/8/19 5 Pad Area 0.5-1.5 11.9 116.7 I 93.4 10/8/19 6 Pad Area 3.0-3.5 11.5 116.3 I 93.0 10/8/19 7 Pad Area 3.0-3.5 12.8 115.1 I 92.1 10/8/19 8 Pad Area 1.5-2.0 13.1 115.2 1 92.2 10/8/19 9 Pad Area 1.5-2.0 11.4 117.5 1 94.0 10/8/19 10 Pad Area 0.5-1.0 10.0 117.6 1 94.1 10/9/19 11 Pad Area 0.0-0.5 10.0 117.4 I 93.9 10/9/19 12 Pad Area 1.0-1.5 15.1 114.2 I 91.4 10/9/19 13 Pad Area 1.0-1.5 13.7 118.7 H 93.5 10/10/19 14 Pad Area 0.0-0.5 15.1 114.0 I 91.2 10/10/19 15 Pad Area 0.5-1.0 9.9 119.3 II 93.9 10/10/19 16 Pad Area F.G. 12.9 118.6 H 93.4 10/11/19 17 Pad Area F.G. 13.2 119.3 H 93.9 10/11/19 P19 18 Pad Area F.G. 12.5 117.7 II 92.7 10/11/19 Pad Area F.G. 13.4 118.4 II 93.2 10/11/19 F.G. Final Grade L EXIST PR' SEWEAJ IYATEL L Approximate Compaction L Test Location SITE PLAN, Partial .0,a-w-0- weal -i- - -! - - -\ - - ----- Scale 1" = 30' ti . 7 Approximate Limits of Grading For Hardscape COAST GEOTECHNICAL, INC. EXIST HOUSE TO REMAIN