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HomeMy WebLinkAbout2 SUNSET HARBOR - SOILSOrange County / Environmental / Corporate 3185-A Airway Avenue Costa Mesa, California 92626 T: 714 549 8921 P: 714 549 1438 past + present + future its in our science Engineers, Geologists Environmental Scientists May 28, 2009 J.N. 153-04 Site Address: 2 Sunset Harbor Newport Coast Grading Permit No.: GB 940159 MR. AND MRS. RON ARAKELIAN c/o The Richard Crawford Company 245 Fischer Avenue, Suite B 1 Costa Mesa, CA 92626 Subject: Geotechnical Review of Revision No. 4 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California. References: 1) Geotechnical Investigation, Proposed Single -Family Residence, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; report by Petra Geotechnical, Inc., dated July 13, 2004, 2) Response to Geotechnical Report Review Sheet by the County of Orange Planning and Development Services Department for Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated January 3, 2005. 3) Geotechnical Review of Revised Precise Grading Plan, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated September 16, 2005. 4) Geotechnical Review of Revision No. 2 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc, dated November 10, 2005. 5) Geotechnical Review of Revision No. 3 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated September 30, 2008. Dear Mr. and Mrs. Aralcelian: Toal Engineering, Inc., project civil engineer, has revised the precise grading plan for the subject site. This revision is designated on the plans as Revision No. 4 and is dated January 21, 2009. Based on our review, the revised grading plan is essentially the same as the previous grading plan that we reviewed as part of the preparation of our previous review letter (Reference No. 5) with the exception of the following revisions: MR. AND MRS. RON ARAKELIAN May 28, 2009 J.N. 153-04 Page 2 1) The pool equipment vault that was previously removed has been put back on the plans. 2) The retaining wall proposed along the rear yard property line at the top of the descending slope has been removed and replaced with a wrought -iron fence. Based on our review, the revised grading plan is considered acceptable from a geotechnical point of view and has incorporated the recommendations of our previous reports. The changes are relatively minor and do not result in any changes to our previous geotechnical recommendations; therefore, revised or additional recommendations are not considered necessary with the exception of the following comments. Since the wrought -iron fence is a light weight and flexible structure, it does not need to supported on special deepened footings. However, it should be noted that some outer and downward movement of the wrought -iron fence may occur with time due to slope creep. Therefore, either a positive separation should be maintained between the wrought -iron fence and any other structures, or, if the wrought -iron fence is connected to another structure, the connection should be flexible or hinged to allow differential movement to occur without damage to the connection. We hope this letter serves your needs at this time. Please call if you have any questions or require further assistance. Respectfully submitted, PETRA GEOTECHNICAL, INC. David Hansen Senior Associate Engineer RCE 56591 DH/kg W:\2004New\I00\153-04\300\Review of Revision No. 4.doc `,1 d Na C 50591 r-j T. Orange County / Environmental / Corporate 3185-A Airway Avenue Costa Mesa, California 92626 T. 714 549 8921 F: 714 549 1438 MR. AND MRS. RON ARAKELIAN c/o The Richard Crawford Company 245 Fischer Avenue, Suite B 1 Costa Mesa, CA 92626 N - 0, i ON O C T 2 12003 past + present + future its in our science Engineers, Geologists Environmental Scientists �v October 20, 2008 E A X E 1. J.N. 153-04 Site Address: 2 Sunset Harbor Newport Coast Grading Permit No.: GB 040159 Subject: Response to Geotechnical Report Review Sheet for Lot 107, 'Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California. References: 1) Geotechnical Investigation, Proposed Single-Farnily Residence, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; report by Petra Geotechnical, Inc., dated July 13, 2004. 2) Response to Geotechnical Report Review Sheet by the County of Orange Planning and Development Services Department for Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated January 3, 2005. 3) Geotechnical Review of Revised Precise Grading Plan, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated September 16, 2005. 4) Geotechnical Review of Revision No. 2 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc, dated November 10, 2005. 5) Geotechnical Review of Revision No. 3 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated September 30, 2008. Dear Mr. and Mrs. Arakelian: This letter has been prepared in response to a geoteclulical report review sheet prepared by Mr. Michael Fisher (County of Orange Geotechnical Report Reviewer) following his review of our latest revised grading plan review letter for the subject site (Reference No. 5). The following item numbers correspond to the OCT 21 1008 MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 2 review sheet continent numbers. A copy of the review sheet is attached to the end of this response letter for ease of reference. Review Sheet Comments Review Sheet Comment No. 1 The Grading Permit for this property expired on 05128108. Please have the owner's agent contact the district grading inspector to extend the permit expiration time (contact: Jerry Anderson 714-796-0446). z Response to Item No. 1 It is our understanding that the owner's agent has already contacted the district grading inspector to extend the permit expiration time. Review Sheet Comment No. 2 Please provide the review sheets approving Revisions I and 2. Response to Item No. 2 Our previous reviews of Revisions 1 and 2 were approved by the County; however, due to the age of this j ob, we had the j ob file stored with an offsite storage company. Unfortunately, they have misplaced the file for this j ob. As a result, we cannot locate the previous review sheets approving Revisions 1 and 2; however, we do have the text of our previous grading plan review letters saved digitally and can print theirs out. We have sent copies of these previous review letters for your use. Review Sheet Comment No. 3 Please provide your recommendations for the caissons supporting the proposed spa at the top of the slope in the rear yard. Please reproduce your caisson recommendations with this Revision 3 report. Response to Item No. 3 Recommendations for the foundations for the spa and pool (including caissons) are reiterated in the following sections. MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 3 Swimming Pool and Spa Construction General Comments Past history has shown that swinuning pools, spas, and similar structures and their associated decking constructed in close proximity to descending slopes cornnionly suffer distress in the form of cracking, lifting, horizontal separations and tilting. Consequently, it is our professional opinion that the proposed swinuning pool, if constructed in its currently proposed locations, may experience some level of distress unless mitigating measures are taken. The swinuning pool and spa recommendations that follow are considered suitable to reduce the potential for future movement or distress of this structure; however, these recommendations should be followed in acknowledgment of the risks involved in the proposed construction adj acent to the slope. These reconunendations are intended to reduce the detrimental effects of slope creep. However, it should be understood. that a certain amount of cracking may occur, as well as horizontal and vertical movement of pool decking. Although a certain amount of distress may occur, it is our opinion that construction of the pool and spa will not have any adverse impact on the adj acent slope or properties provided that they are designed and constructed in accordance with our recommendations. Structural Setback The westerly sides of the swinuning pool and spa are proposed within close proximity of the top of the adj acent descending slope. Therefore, in order to provide adequate vertical and lateral support of the pool, the westerly pool and spa walls should be designed as free-standing walls that are structurally tied to the pool bottom. These walls should also be supported by deepened continuous footings or caissons, as necessary, such that a minimum horizontal setback of at least 15 feet is maintained between the outside bottom edge of the footings and the slope face. This recommended setback will exceed the reconunendations of the 2007 CBC and also takes into consideration the anticipated creep zone within the rear yard descending slope. Reconunendations for deepened footings or caissons are provided below. Deepened Pootim: Footings for the westerly walls of the pool and spa proposed along the top of the rear yard descending slopes should be founded at a depth that will provide a minimum footing setback of at least 15 feet measured along a horizontal line projected from the outside bottom edges of the footings to the daylight contact with the slope face in order to extend the footings below the creep zone. It should be noted that additional footing depths may be required to resist the potential creep forces and MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 4 to achieve the necessary passive resistance against lateral movement as determined by the project structural engineer based on the soil parameters provided below. Footings for the pool and spa walls at the above recommended minimum setbacks may be designed using the allowable bearing values of 1500 pounds per square foot increasing to 2500 pounds per square foot as reconunended previously for building footings in our original report; however, when calculating passive resistance, the passive earth pressure should be reduced to 150 pounds per square foot, per foot of depth, to a maximum value of 1,500 pounds per square foot. In addition, the lateral resistance should be ignored for the upper portions of the wall footings located within the creep zone (upper 5 feet). It should be noted that if deepened footings are used, the upper portions of these footings that are below grade but are located within the creep zone will essentially become retaining walls due to the outward and downward movement of the surficial slope soils away from the outer face of the wall. By constructing a continuous footing, it is anticipated that the earth materials behind the footing will no longer be able to creep past the footing and exert creep forces; however, they will exert an active earth pressure equivalent to a fluid having a density of 45 pounds per cubic foot. To mitigate the buildup of any hydrostatic pressure, a subdrain system should be installed below the pool and spa as recorninended in a subsequent section. Cast -In -Place Caissons: In lieu of deepened conventional footings, cast -in -place concrete caissons and grade beams may be used to support the wall proposed along the top of the rear yard descending slopes. Specific design recommendations for the caissons and grade beams are provided below" i. Grade Beam Embedment: The tops of the grade beams may be located near the ground surface. No specific setback will be required between the outside bottom edges of the grade beams and slope face. ii. Lateral Resistance for Grade Beams: Due to downward and outward movement of the surficial soils within the creep zone, lateral resistance and bearing capacity should be ignored in design of grade beams. W. Caisson Capacity: End bearing capacity and skin friction may be combined to determine allowable caisson capacities provided the minimum caisson diameter is 18 inches. Ali allowable end bearing capacity of 5,000 pounds per square foot may be used for caissons embedded at least two caisson diameters or 4 feet below the creep zone and into compacted fill, whichever is greater. A value of 400 pounds per square foot may be used to determine the skin friction between the concrete and the surrounding fill materials; however, when calculating skin friction, the upper portions of the caissons located within the creep zone should be ignored. iv. Passive Resistance for Caissons: A passive earth pressure of 450 pounds per foot of caisson width per foot of depth may be used to determine lateral resistance for those portions of the caissons founded in compacted fill; however, lateral resistance should be ignored for the upper portions of the caissons located within the creep zone. MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 5 v. Lateral Loading: To compensate for potential creep forces, the caissons should be designed to resist a lateral load imposed by creep affected slope materials. This lateral load should be assumed to be equal to 1,000 pounds per foot of embedment in the creep zone. The reason that the creep force provided is independent of caisson width is that we compensate for this effect by limiting the caisson spacing to a maximum of six caisson diameters, center to center (see item viii). In other words, if 18-inch caissons were used, the maximum spacing would be 9 feet, center to center, while 24-inch caissons would have a maximum spacing of 12 feet, center to center. The creep forces acting on 18-inch caissons spaced 9 feet are considered to be equivalent to the creep forces acting on 24-inch caissons spaced 12 feet. If the grade beams are constructed below grade and within the creep zone, an active earth pressure equivalent to a fluid having a density of 45 pounds per cubic foot should be assumed to be acting on these grade beams. However, wall steins and other structural elements con-structed on top of the grade beams and above the creep prone soils will not be subject to creep forces. Our recommendations to limit the maximum spacing of the caissons to six caisson diameters, center to center, will create an arching effect between the piles and mitigate the potential for slope creep to adversely affect any structures located behind the caissons. vi. Point of Fixity: The point of fixity for the caissons should be determined by the proj ect structural engineer. However, as an approximation, the point of fixity may be assumed at a depth equal to the depth of the creep zone plus two times the caisson diameter. vii. lfJEM: Caissons may be considered to resist uplift forces equal to the skin friction between the concrete caisson and the surrounding fill as described above. Allowable uplift capacity should not exceed 55 percent of the allowable downward capacity. viii. Caisson Depth and Spacing: Caisson depth and spacing should be determined by the project structural engineer based on total wall loads and lateral loading. However, ininimum clear spacing between caissons should be two caisson diameters, sidewall to sidewall. In addition, maximum spacing between caissons should not exceed six caisson diameters, center to center. Further, the caissons should have a minimum depth of at least two caisson diameters or 4 feet below the creep zone, whichever is greater and the total depth should be deep enough such that a minimum horizontal setback of at least 15 feet is maintained between the outside bottom edges of the caissons and the face of the adjacent slope. ix. Caisson Locations Relative to Wall: To prevent eccentric loading, the centerlines of the caissons should correspond to the centerline of the wall. x. Reinforcement: Reinforcement for caissons should be determined by the project structural engineer with regard to strengthening the concrete to resist lateral forces. MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 6 A. Geotechnical Observations: All caisson excavations should be observed by a representative of the project geotechnical consultant to verify minimum embedments determined by the project structural engineer. The drilled holes should also be cleared of loose materials and any construction debris prior to pouring concrete. Al. Concrete Placement: Concrete should be placed by the tremie method and not allowed to free fall to prevent segregation of the concrete, as well as scouring or erosion of the sidewalls of drilled holes. The lower end of the trernie pipe should be continually immersed in fresh concrete and slowly withdrawn as the concrete is deposited. Subdrainage Due to the proximity of the pool and spa to the adjacent descending slope, there is a possibility of distress to the slope in the event of an undetected plumbing leak. Therefore, in order to prevent the possible accumulation of leaking water in the area of the slope, a perforated pipe and gravel subdrain should be installed in a 12-inch by 12-inch trench excavated across the deepest part of each pool excavation. The perforated subdrain pipe should consist of 4-inch diameter ABS SDR-35 or PVC Schedule 40. Gravel placed around the perforated pipe should consist of 3/4- to 1'/2-inch open -graded gravel completely wrapped with filter fabric. Filter fabric should consist of Mirafi 140N, or equal. The perforated pipe should be underlain by approximately 2 inches of the open -graded gravel and should be laid with the perforations down. The perforated pipe should be connected to a 4-inch-diameter ABS SDR-35 or PVC Schedule 40 solid pipe that is routed to a suitable discharge point. The pipe should not be routed onto the face of the adjacent slope as this could result in future slope erosion and surficial soil saturation. To ensure a positive gravity flow, the perforated pipe and solid outlet pipe sections should be installed at a minimum gradient of 1 percent. Stability of Temporary Excavation The pool and spa excavation is expected to expose competent compacted fill materials. Based on the anticipated physical characteristics of these materials, the excavation sidewalls may remain at a vertical gradient. The temporary sidewalls are expected to remain stable during construction of the pool; however, the temporary excavation sidewalls should be observed by a representative of the project geoteelulical consultant for any evidence of potential instability. Depending upon the results of these observations, revised sidewall slope configurations may be necessary and forming of the pool and spa walls may be necessary. MR. AND MRS. RON ARAKELIAN October 20, 2008 J.N. 153-04 Page 7 Temporary Access Ramps It is essential that all backfill placed within temporary access ramps extending into the pool and spa excavation be properly compacted and tested. This will mitigate excessive settlement of the backfill and subsequent damage to pool decking or other structures placed on the backfill. Pool and Spa Bottoms It is expected that the swinuning pool and spa bottoms will rest entirely on compacted fill. Therefore, care should be taken while excavating these structures to prevent disturbance of subgrade soils exposed at grade in 11 the pool bottom. Pool Decking Pool decking should be constructed in accordance with the recommendations presented in the "Exterior Concrete Flatwork" section of this report. Plumbing Fixtures Leakage from the swinuning pool or spa or from any of the appurtenant plumbing could create adverse saturated conditions of the surrounding subgrade soils. Localized areas of oversaturation can lead to differential expansion (heave) of the subgrade soils and subsequent raising and shifting of concrete flatwork. Therefore, it is essential that all plumbing and pool fixtures be absolutely leak -free. For similar reasons, drainage from pool deck areas should be directed to local area drains and/or graded earth swales designed to cant' runoff water to a suitable discharge point. Review Sheet Comment No. 4 What are the minimum setbacks for the spa and caissons? Will it meet the latest CBC minimum setbacks? MR. AND MRS. RON ARAKELIAN Response to Item No. 4 October 20, 2008 J.N. 153-04 Page 8 As described in the previous response to Comment No. 3, a minimum setback of 15 feet is recommended between the outside bottom edge of the caissons and the face of the adjacent slope. This minimum setback meets the latest CBC minimum setback requirements. Review Sheet Comment No. 5 Should you have any questions you can call me Response to Item No. 5 Acknowledged. No response required. We trust this letter serves your needs at this time. Should you have any questions, please feel free to call. Respectfully submitted, PETRA GEOTECHNICAL, INC. David Hansen,°<.� Senior Associate Engineer RCE 56591 DH/kgt W:\2004New\100\153-04\300\Response Lettendoc 1 :01 o County of Grange Resources and Development Management Department — Grading Section o 300 North Flower Street - P.O. Box 4048 0 Santa Ana, California 92702-4048 (714) 834-6156 FAX (714) 834-5413 GE®TECHNICAL REPORT REVIEW SKEET Review of Ge®techffiYcal Reports inclaodiffia: & rt Date Date Received 5011 Report RiTyoe of Reuort Geologic Report Preliminary (Initial) Geotechnical In -grading or interim 09-30-08 09-30-08 Response Supplemental or Addendum Revision 3 Tract: 14065 Lot: 107 - - - � ---. Site Address: 2 Sunset Harbor, Newport Coast, County of Orange, California Precise Grading Permit No. GB040159 .Developer/Owner: Mr, and Mrs. Ron Arakelian c/o The Richard Crawford Company Address: 245 .Fischer Avenue, Suite B-1, Coast Mesa, CA 92626 Senior Associate .Engineer: Mr. David Hansen, RCE 56591 Prior to thend to the following 1. The Grading Permit for this property expired on 05/29/08. Please have the owner's agent contact the district grading inspector to extend the permit expiration time (contact: Jerry Anderson 714-796-0446). 2. Please provide the review sheets approving Revisions 1 and 2. 3. Please provide your recommendations for the caissons supporting the proposed spa at the top of slope in the rear yard. Please reproduce your caisson recommendations with this Revision 3 report. 4. What are the minimum setbacks for the spa and caissons? Will it meet the latest CBC minimum setbacks? 5. Should you have questions you can call me. Report Reviewed by: "W (For NJB) October 7, 2008 Michael Fisher, PG Geotechnical Report Reviewer Date: michael.fisher@rdmd.ocgov.com Orange County / Environmental / Corporate 3185-A Airway Avenue Costa Mesa, California 92626 T. 714 549 8921 F: 714 549 1438 past + present + future its in our science Engineers. Geologists Environmental Scientists September 30, 2008 J.N. 153-04 Site Address: 2 Sunset Harbor Newport Coast Grading Permit No.: GB 040159 MR. AND MRS. RON ARAKELIAN c/o The Richard Crawford Company 245 Fischer Avenue, Suite B 1 Costa Mesa, CA 92626 Subject: Geotechnical Review of Revision No. 3 to Precise Grading Plans, Lot 107, Tract 14065,2 Sunset Harbor, Newport Coast, County of Orange, California. References: 1) Geotechnical Investigation, Proposed Single -Family Residence, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; report by Petra Geotechnical, Inc., dated July 13, 2004. 2) Response to Geotechnical Report Review Sheet by the County of Orange Planning and Development Services Department for Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated January 3, 2005. 3) Geotechnical Review of Revised Precise Grading Plan, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc., dated September 16, 2005. 4) Geotechnical Review of Revision No. 2 to Precise Grading Plans, Lot 107, Tract 14065, 2 Sunset Harbor, Newport Coast, County of Orange, California; letter by Petra Geotechnical, Inc, dated November 10, 2005. Dear Mr. and Mrs. Arakelian: Toal Engineering, Inc., project civil engineer, has revised the precise grading plan for the subject site. This revision is designated on the plans as Revision No. 3 and is dated August 8, 2008. Based on our review, the revised grading plan is essentially the same as the previous grading plan that we reviewed as part of the preparation of our previous review letter (Reference No. 4) with the exception of the following revisions: 1) The pool equipment vault previously proposed in the rear yard has been removed.. 2) The size of the spa has been increased. a MR. AND MRS. RON ARAKELIAN September 30, 2008 J.N. 153-04 Page 2 3) The location of the storm water lift station has been revised. 4) Retaining walls have been added between the pool and spa and to the northeast of the proposed spa. 5) Retaining walls have been added along the northeast side of the driveway that provides access to the upper garage. 6) The layout of the concrete flatwork and the corresponding drainage within all of the yard area has been changed. Based on our review, the revised grading plan is considered acceptable from a geotechnical point of view and has incorporated the recommendations of our previous reports. The changes are relatively minor and do not result in any changes to our previous geotechnical recommendations; therefore, revised or additional recommendations are not considered necessary with the exception of the following comments. The retaining walls proposed between the pool and spa and to the northeast of the spa are proposed in close proximity of the adjacent descending slope. Therefore, these walls should be supported on caissons in order to meet setback requirements and mitigate the adverse affects of slope creep. These caissons may be designed using the recommendations of our previous reports. We hope this letter serves your needs at this time. Please call if you have any questions or require further assistance. Respectfully submitted, PETRA GEOTECHNICAL, INC. D� — David Hansen Senior Associate Engineer RCE 56591 DH/kg W:\2004New\100\153-04\300\Review of Revised Grading Plan.doc B.a A