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HomeMy WebLinkAboutS2021-0210 - Calcs (2)September 8, 2021 S2q? o2l0 21 tt4l' Wfi-6 e o s Consulting Engineering Geologists BUILDING DIVISION SEP z 0 2021 �'40O W Talmour Suchard W S.R.G. Project No. 211720 21 Harcourt Report No. 21-065 Newport Beach, CA 92657 Subject: Geotechnical Recommendations for Construction of Swimming Pool/Spa 21 Harcourt Newport Beach, California Reference: 1. Preliminary Geotechnical Investigation for the Proposed Swimming Pool/Spa Remodeling at 21 Harcourt, Newport Beach, California, by Applied Geotechnical, Inc. W.O. 2012-13, dated January 7, 2021. 2. Geotechnical response to City of Newport Beach geotechnical review comments dated January 14, 2021 21 Harcourt, Newport Beach, California, by Applied Geotechnical, Inc. W.O. 2012-13R2, dated January 29, 2021. Dear Mr. Suchard; The following geotechnical recommendations are provided for construction of the proposed swimming pool/spa at the subject site. These recommendations are based upon review of the referenced reports by Applied Geotechnical, Inc. and review of current swimming pool plans, as well as, conversations with the reviewing engineering geologist for the City of Newport Beach regarding City requirements for the project. Our scope of services has included review of current plans for the swimming pool/spa, observation of current site conditions, excavation of three hand auger borings at the proposed swimming pool location to verify depth to bedrock, and preparation of this brief report. The swimming pool and attached spa are proposed to in the rear yard and will overlap the location of an existing swimming pool/spa, as shown on Figure 1. Plans indicate that a negative edge trough is proposed at the perimeter of the swimming pool. The depth of the swimming pool will vary from 1 to 6 feet and the spa will be raised slightly above the elevation of the swimming pool. The maximum depth of proposed excavation is anticipated to be 7+ feet. The pool and excavation will be located at least 7 feet from the adjacent residential property to the north and will occur 3 feet horizontally from a low masonry wall with grass screen wall that occurs along the rear property boundary. Land bordering the reservoir to the rear of the site is undeveloped. ViaGeos* 305 N. Coast Highway, Suite R TEL (949) 494-2721 P.O. Box 309, Laguna Beach, CA 92652 FAX (949) 376-5766 21 Harcourt Sep tembcr 8, 2021 Newport Beach, Cali£omia P roject No. 211720 Report No. 21-065 Based upon review of the referenced reports by Applied Geotechnical, Inc., and as verified by three additional hand auger borings in the swimming pool spa location, the year yard is underlain by 2+ feet of engineered fill that overlies bedrock strata. The fill typically consists of silty sand with sandstone fragments, and the bedrock strata consist of very well indurated sandstone. Applied Geotechnical, Inc. reports that the fill materials have very low expansion potential based on laboratory testing of near surface soils. Conclusions 1. Construction of the proposed swimming pool/spa is considered geotechnically feasible provided the recommendations of this report are incorporated in design, construction and maintenance of the property. Proposed construction is not anticipated to adversely impact adjoining properties provided appropriate construction methods and care are utilized during construction. 2. The proposed swimming pool/spa shell shall be supported in competent bedrock and sand -cement slurry backfill placed above competent bedrock. Recommendations Temporary Excavations The temporary excavation for the swimming pool is anticipated to expose competent sandstone bedrock that is overlain by 2 to 2.5 feet of compacted fill. Temporary excavations for the swimming pool should be constructed in accordance with CalOSHA requirements and applicable agency grading and building codes. In general, temporary excavations may be constructed vertically to 5 feet in height with higher portions of excavations laid back at a 1:1 (horizontal:vertical) slope. Structural surcharge of the adjacent 2+ feet high masonry screen wall is not considered to be significant to stability of the temporary excavation for the swimming pool. Temporary shoring is not anticipated. Stability of temporary excavations is, in part, time dependent and the swimming pool shell should be constructed without undue delay. The builder must take appropriate precautions to protect temporary excavations from rainfall and surface water discharge which may cause or contribute to erosion or instability of temporary excavations during retaining wall construction. In general, un -shored temporary excavations should not remain exposed for more than three weeks. Structural Design of Swimmina Pool/SDa The swimming pool/spa should be supported entirely onto competent bedrock and/or sand cement slurry backfill placed onto competent bedrock. Where applicable and where it is verified that the existing pool shell is underlain by competent bedrock, sand -cement slurry backfill may be placed above portions of the existing pool shell that may remain in place (un - demolished) below the bottom of the proposed pool shell. This condition is anticipated to occur near the proposed spa and shallow end of the proposed swimming pool that is located over the deep end (6+ ft.) of the existing pool shell. (Refer to Figure 1.) It is recommended that a minimum 3 ft. x 3 ft. hole be demolished through the bottom of the existing pool shell to remain, prior to backfill with sand -cement slurry. The swimming pool/spa excavation should be observed by the engineering geologist prior to placement of slurry backfill and placement of steel, and supplemental recommendations for preparation of the bottom of the excavation may be provided at that time. ViaGeos 21 Harcourt Sep tember 8, 2021 Newport Beach, California P roject No. 211720 Report No. 21-065 An allowable vertical bearing value of 1500 pounds per square foot may be assumed for structural design. Design to resist lateral loads should be based upon passive pressures of 150 pounds per square foot per foot of depth in geotechnically approved on-site soils, up to a maximum value of 2250 pounds per square foot. The frictional resistance may be determined by using a coefficient of friction of 0.25. The swimming pool/spa shell should be designed and constructed with appropriate reinforcement based on an equivalent fluid pressure of 100 pounds per cubic foot for level backfill. Structural surcharges must be addressed by the Pool Engineer. Concrete Design Near surface soils are anticipated to result in conditions of negligible sulfate exposure (Exposure Class SO), based upon laboratory testing performed by Applied Geotechnical, Inc. Unless revised based upon results of additional testing at the completion of excavation, concrete design should be completed in accordance with ACI 318-14 based upon Sulfate Exposure Class SO. Use of Type V cement, although not specified per ACI, is considered prudent. Observation and Testing As a condition for use of this report, this office shall be retained to perform field observation and testing during construction which may include, but may not be limited to: • Observation of removal of existing fill and disturbed soils in locations of slurry backfill placed within the limits of the swimming pool shell, as well as, compacted soil backfill placed outside the limits of the proposed swimming pool shell. • Observation of swimming pool/spa excavation prior to placement of steel. • Compaction and moisture testing of all fills including soil backfill placed outside the limits of the proposed swimming pool shell and utility trench backfill. This observation and testing, as well as design consultation, pre -grade or other meetings, and response to agency review (City of Newport Beach) are outside of the scope of this investigation and budget and will be conducted on a time and expense basis as authorized by the owner, or the builder. Timely notification (48 hours) of geotechnically involved phases of construction is the responsibility of the owner and his builder. Limitations Our investigation has been performed using the degree of care and skill ordinarily exercised under similar circumstances by reputable geotechnical consultants practicing in this or similar localities. No warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The observations and interpretations presented herein are believed to be representative of the project site. However, soil and geologic conditions can vary significantly between observation points (borings) and field conditions revealed in future excavations may be at variance with the preliminary findings. Should this occur, the changed or differing conditions must be evaluated by the geotechnical consultant and design may be adjusted as required, or alternate design may be recommended as needed. ViaGeos 21 Harcourt Newport Beach, California September 8, 2021 P reject No. 211720 Report No. 21-065 This report is intended for the design life of this specific project and for the sole use and benefit of our client in conjunction with the undersigned consultants. It is not intended necessarily to be adequate for a contractor to provide a fixed price bid or for a client to expect that no changed or differing conditions will be encountered during construction. This report may not be assigned to a third party, and any transfer of information or data from this report is not valid, without first obtaining the written permission and consent of this office. Any unauthorized transfer of this report should be considered advice by the client. The opportunity to be of service is genuinely appreciated. If you have any questions or comments, please contact this office. Sincerely, VIaGBO ? PEDB �y<p No 1869 Fl ✓�O N ✓ I ! r��j,(!/ �yj� /t✓GL✓G� CERTIEe /�-��1. "� ✓--�� ti�.�--'�.. :,I ENGINEERING LP Exp it GIST ichael B. Childs, President Keith D. Tucker ngineering Geologist EG 16 OFcauFR.G.E. 841 Registration Expires 3/3122 Registration Expires 12/3122 Attachment: Figure 1 - Plot plan of proposed swimming pool ViaGeos Ni Figure 1 - Plot plan of proposed swimming pool