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Home My WebLink AboutCT 13-03; RANCHO COSTERA; RESPONSE TO CITY OF CARLSBAD REVIEW OF THE VERDURA RETAINING WALL PLANS; DWG 480-3A; 2016-06-14* SOIL RETENTION DESIGNS I N C. RECEIVED JUN 21 2016 LAND DEVELOPMENT El\ir""'1· ,,,....r,ING • 'l l::J I !\, t=. t: i""{ ·· Date: June 14, 2016 SRD Project No: 1303-006 To: Toll Brothers, Inc. Attn: Mr. Kevin Brickley 725 W. Town & Country Road Suite 200 Orange, CA 92868 IlECORD COPY c#v y_jµ;/!<1 ---, Initial Date Subject: Response to City of Carlsbad Review of the Verdu~4t:ettmift1i!:':"'n'mi:--fJJta Report, Rancho Costera, Carlsbad, CA --~~ es1gn References: "Verdura® Retaining Wall Design, Rancho Costera, prepared by Soil Retention Designs, Inc., SRD Project No. 1303-006, dated April 4, 2016. "Verdura® Retaining Wall Plans, Rancho Costera, prepared by Soil Retention Designs, Inc., SRD Project No. 1303-006, dated April 18, 2015. Per your request, Soil Retention Designs, Inc. (SRD) has prepared this letter to address plan check comments regarding the Verdura® Retaining Wall design and plans for the subject project. Our responses are provided on an item by item basis with the City of Carlsbad review comments attached at the rear of text for reference. It should be noted that the accompanying construction drawings for the Verdura® Retaining Wall are structural wall design plans. Accommodation for drainage provisions, temporary excavations, cable railing, fencing and all other site geometries should be part of the grading plans for the proposed project. Within our construction drawings, the grading plan is copied for reference only. Corrections noted below are included on the updated construction drawings (Verdura® Retaining Wall Plans, Sheets 56 through 60, dated June 14, 2016) which accompany this response report. REDLINE COMMENTS IN DESIGN REPORT: Comment on Page 6 -Provide documentation from LGC (signed & stamped) stating the above requirement. • Please see the attached letter from LGC. Comment en Page 8 -Why NIA? Is the lower wall not tiered w/ upper wall? Please address. (typ). • While the lower and upper walls are tiered walls, the offset between the walls require for these walls to be analyzed separately where the lower wall has a surcharge in the design to account for the upper wall. 2501 State Street • Carlsbad, CA 92008 • P: (760) 966-6090 • F: (760) 966-6099 • www.soilretention.com Response to Review Comments -Rancho Costera SRD Project No. 1303-006 June 14,201 REDLINE COMMENTS ON WALL PLANS: Comment on 57 -Show existing grade • Existing grade has been added to the wall profiles. ~ Comment on 57 -X-section not included on Sheet 16 -Sheet 18? • A section callout has been provided and refers back to Sheet 18. Page2 Comment on 58 -Include I Show info on Sheet 6. Sheet 6 not provided to verify info was included. • Sheet 6 has been included as a reference drawing in this package. i •• Comment on 58 -Avoid overlap for clarity • 2% callout has been adjusted as requested. Comment on 60-Lower Retaining Wall I Upper Retaining Wall • The retaining walls in the Top of Wall Details have been called out as requested. Should you have any questions, please contact the undersigned. Respectfull subfli 'ed, ~0.(tt~ Niklas E. l sson, PE Vice Pres'i nt Dis~n: (2) Addressee Attachments: Geotechnical Response to the City of Carlsbad Plan Check Review Comment 2501 State Street • Carlsbad, CA 92008 • P: (760) 966-6090 • F: (760) 966-6099 • www.soilretention.com November 9, 2015 Mr. Kevin Brickley Toll Brothers LGC Valley, Inc. Geotechnical Consulting 725 Town and Country Road, Suite 500 Orange, California 92868 Project No. 133023-03 Subject: Geotechnical Response to the City of Carlsbad Plan Check Review Comment, Regarding Verdura Retaining Walls No. 24 and 30, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California References: LGC Valley, Inc., 2015, Geotechnical Review of Mechanically Stabilized Retaining Walls No. 24 and 30, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated October 8, 2015 LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014 Carlsbad City, 2015, First Review of the Verdura Retaining Walls Nos. 24 and 30, Rancho Castera, Carlsbad, California, dated October 23, 2015 In accordance with your request, we have prepared this letter to address the plan check review comment made by the City of Carlsbad regarding the proposed Verdura Retaining Walls Number 24 and 30 within the Robertson Ranch project located in the City of Carlsbad, California. The review comment was hand written on the Soil Retention Design Inc. design calculation report. For ease of review the review comment is provided below and the hand written comment on Soil Retentions design calculation report is also attached to this response. Review Comment Provide documentation from LGC (signed and stamped) stating the above requirement. "It is the project geotechnical engineer-of-record's responsibility to review the enclosed design calculations, plans, and specifications in order to ensure that the assumptions made herein are consistent with their intentions. The geotechnical engineer of record will be responsible for ensuring that the soil, materials, and methods used in construction of the proposed Verdura retaining wall systems are conducted in accordance with the specifications outlined herein." Response to Review Comment LGC Valley, Inc. (LGC) is the geotechnical engineer-of-record for the subject Robertson Ranch Carlsbad Tract 13-03 project and has been performing geotechnical observation and testing during the grading and post-grading operations. 2420 Grand Avenue, Suite F2 • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007 LGC performed a geotechnical evaluation and review of the proposed Verdura mechanically-stabilized retaining wall design calculations, plans, and specifications for Retaining Wall Numbers 24 and 30 within the Robertson Ranch/Rancho Costera project located in the City of Carlsbad, California. LGC performed our review on October 8, 2015 as documented in the referenced letter. This letter (LGC, 2015) is attached to this response. The latest Verdura Segmental Wall Plans, dated September 11, 2015, and the Wall Design Summary report dated September 14, 2015 prepared by Soil Retention Design, Inc. (SRD) were the subject of our geotechnical review. The purpose of our evaluation was to review the plans and geotechnical soil parameters utilized in the design for conformance with the recommendations provided in the referenced geotechnical documents (LGC, 2014). Based on our review, it is our opinion that the recommendations included in the referenced geotechnical report (LGC, 2014) have been properly incorporated in the Verdura wall plans, design, and specifications, and the Verdura Retaining Walls/slopes are globally stable as designed. Therefore, LGC finds the plans, design, and specifications are acceptable from a geotechnical point of view provided the recommendations of the referenced report are implemented during construction. LGC's geotechnical observation and testing and documentation services during construction of the Verdura Retaining Walls ensured that the soil, materials, and method of construction of the Verdura Retaining wall systems was constructed in accordance with the specification of the referenced geotechnical report and the Verdura Wall design plans and specifications. If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at (760) 599-7000. Respectfully submitted, LGC Valley, Inc. Randall Wagner, CEG 1612 Senior Project Geologist '8--11-!4 Basil Hattar, GE 2734 Principal Engineer Attachments: 1) City of Carlsbad, 2015, Retaining Wall Review Comments, 1st Review, dated October 23, 2015 2) Geotechnical Review of Mechanically Stabilized Retaining Walls No. 24 and 30, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, dated October 8, 2015 by LGC Valley, Inc. Distribution: (2) Addressee (2) City of Carlsbad Attention: Mr. Grant Clavier Project No. 133023-03 Page2 November 9, 2015 f Project No. 133023-03 Attachment No. 1 City of Carlsbad Retaining Wall Review Comments, 1st Review, dated October 23, 2015 Attachment No. 1 November 9, 2015 \ ii-t'" w: (/IV 101~~1,~/ ,i. t;l -( ·¥·-~'-'---1 >JIU;' ,---f 4<""'*"41!#' \-'fi'1"'1<fliM' %"·/ii" ··--w,ci· </f-;'!10{,,,:0•'"'1<'-·,-·~·-k''<,--:y,,," -·c;,,c,~e·y:-.. >'-.,,-.·1,--,i~•;.:.~-·-";"·,,'' ...• a,, ...•• ·.{l5:.;:,)5,~· ·.·.··'it ···'1.if: .. ·ji/ltf ·11;/ Verdura® Retaining WallDesign · .frl"oject: R.ancho.Costera . . wa1.1s•24&.30 Caflsbad, CA Prepared for: Toll Brothers, Inc. 725 W. Town & Country Road . Suite 200 Orange,,CA ·92868 SRD Project No: 1303-006 September 14, 2015 j' I f I I .i u I I I I I I I I I I I I I I I I I t t$ SOIL RETENTION .;, ,, -,,,,.,' ., ' DESIGNS I N C. Date: September 14, 2015 SRO Project No.: 1303-0f6 To: Toll Brothers, Inc. 725 W. Town & Country Road Suite 200 Orange, CA 92868 Attention: Mr. Kevin Brickley Subject: Verd11ra® Retaining Wall Design, Rancho Costera, Walls 24 & 30, Carlsbad, CA In accordance with your request, Soil Retention Designs, Inc. (SRD) has prepared this report for the proposed Verd11ra® retaining walls at the subject site. The enclosed structural design addresses four (4) walls located within the proposed project site as depicted within the accompanying construction drawings (Verd11ra® Retaining Wall Plans--Sheets 56 through 60). The subject structural design is based upon the referenced grading plans and wall profiles, which were prepared by Michael Baker International. REFERENCED DOCUMENTS The infi·?··~. ation p. ~.ovid·:.d fi.··o·r· .. u· •s· e in. ~.··h·e· enclose·d··· s·.tru· . c~ral analyses···.1.·n·.·.cluded the following:,:~;···:·:·;·· ... '.·.•.· ..... · .. ·.·.·.· t:..co.},\ ~•, ~'-~'*'. '; ... ~~ \:)y. D Do..J r~on'l:v\~"h,-C,\;r,·, · t.~, I. ani.ding and W:atflffln . .· . : tiertson ~ch West N'illage, 'Rancho Costera, prepared 'ymlchael Baker International, dated 09/09/20 !.IJ · · · · 2. "Geotechnical Evaluation and Mass Grading Recommendations, Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, CA", prepared by LGC Valley, Inc., dated 04/24/2014. SCOPE OF WORK The scope of design services provided for this project included the following: 1. Review of the above referenced documents relative to obtaining necessary design parameters. 2. In-office analysis and design of the proposed Verd11ra® Retaining Walls as required to accommodate the established civil design. 3. Preparation of this report, which contains our calculations and associated specifications, accompanying construction plans that relate directly and specifically to the proposed retaining walls. 2501 State Street• Carlsbad, CA 92008 • P: (760) 966-6090 • F: (760) 966-6099 • www.sollretentlon.com Verdura«' Retaining Wall Design .. Rancho Costcra (Walls 24, & 30) SRD Project No. 1303-006 September 14, 2015 Construction Details.-Detailed specifications, relative to the construction of the Verd11ra® retaining wall system, are provided on the accompanying construction drawings (Verd11rtl' Segmental Wall Plans - Sheets 56 through 60). The length, strength and spacing of geosynthetic reinforcements are depicted on the wall profile. The minimum recommended geogrid lengths in accordance with the total heights should be maintained throughout the wall per the accompanying drawings. Geogrid spacing for all wall areas shall not be more than 3 block courses except for top of wall areas as noted on the accompanying construction plans. PlantabUity and Landscaping:,-The Verd11r"'1 retaining wall system has a fully plantable fascia. The Verd11rae SRW unit is designed with a "lip" on the block which helps to retain soils within the block when the units are spaced apart up to 9 inches. The free-face design allows for vegetation to root itself back into the cooler soils of the reinforced mass and does not limit the root area to a smaller concrete planter pocket. A landscape architect should be consulted for the site specific applications. GLOBAL STABILITY ANALYSES Global stability of earthen slopes surcharged by retaining walls is independent of local structural design for retaining walls and hence ha.s not been conducted as part of the design included herein. The global stability of the slope and retaining wall combination is the responsibility of the geotechnical engineer-of- record and should be provided under separate cover prior to initiation of construction. Minimum safety factors for potential failure surfaces that may occur behind and beneath the Verd11ra® retaining walls within the surrounding slopes should be documented and approved by all appropriate reviewing agencies. GEOTECHNICAL ENGINEER-OF-RECORD It is the project geotecbnical engineer-of-record's responsibility to review the enclosed design calculations, plans, and specifications iil order to ensure that the assumptions made herein are consistent with their intentions. The geotechnical engineer of record will be responsible for ensuring that the soil, materials, and methods used in construction of the proposed Verd11ra® retaining wall systems are conducted in accordance with the specifications outlined herein. l , 'y rvv:~ ~oc..lJ~(!M\~O'I\ . t ~~ t.---t-& Cs :~rJ ' s~~reAJ s-~\:V\! ~ \ r ,,,,cw; re,V'I\ em\.-. ().,\oQ../v '"'" J 2501 State Street • Carlsbad, CA 92808 • P: (760) 966-6090 • F: (760) 966-6099 • www.sollratentlon.com I I I I I I I I I I I I I I I I I I I Vcrdura• Rctainlns Wall Design -Rancho Costcra (Walls 24 & 30) SRD Project No. 1303--006 September 14,201S / .l ~\n:r11 Design Summary Table f f\{1,·· ' -tJ\\ ,:, t i "' Design No. I Vffef ,,\.\l Wall No. 24 (Lower) .. . . '" r,JJ,, 11., ,._.,, !:re/ ... ~ Structure Geometry I ·-( L, Total Heleht 14.67' (10.67' Ex~-~~ W.:th 4' Embedment) \. ,:~,, Tiered Condition {N/A J I ;) Crest Condition -.... -·· .-; ...... PAtl h.E.V1?::I- 'J'oe Condition 2:1 Slope Minimum Leneth/Heb?ht Ratio 0.81 (12'/14.67') Geofochnical Parameters Reinforced Retained Foundation Friction anele, •• deerees 30 30 30 Dn Unit Wei2ht, Yd. pcf 125 120 120 Cohesion, c. osf o• o• 50 Seismic acceleration, I! SO% of 0.4532. Global Stability Per Geotechnical En2ineer of Record * Note: Cohesion within the reinforced and retained soil zones is conservatively ignored within the analysis. Minimum Factor of Safety FS, Static FS, Seismic External Stability ActualFS TargetFS Actual FS TargetFS Slldine 3.381 >1.5 1.460 ~l.l Overturnine 8.21 ~.o. 2.78 >l .• S Bearine Caoacitv/Settlement 4.60 ~.o 2.48 >LS Internal Stability Actual FS Target FS Actual FS TargetFS Slidine 3.407 ~1.5 1.472 ~1,.1 Pullout 7.503 >l.5 2.912 >I.I Geoerid Streneth 3.177 >1.5 2.622 ~1.1 Local Stability Actual FS TargetFS Actual FS TargetFS Geoerid to Block Connection 2.49 ~l.5 1.49 >I.I 2501 State Street• Carlsbad, CA 92008 • P: (760) 966-6090 • F: (760) 966-6099 • www.sollretentlon.com Attachment No. 2 Geotechnical Review of Mechanically Stabilized Retaining Walls No. 24 and 30, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, dated October 8, 2015 by LGC Valley, Inc. Project No. 133023-03 Attachment No. 2 November 9, 2015 October 8, 2015 Mr. Kevin Brickley Toll Brothers LGC Valley, Inc. Geotechnical Consulting 725 Town and Country Road, Suite 500 Orange, California 92868 Project No. 133023-03 Subject: Geotechnical Review of Mechanically Stabilized Retaining Walls No. 24 and 30, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California References: LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014 Introduction Soil Retention Designs, Inc., 2015a, Verdura Segmental Wall Plans, Wall No. 24 and 30, Rancho Castera, 5 Sheets, dated September 11, 2015 Soil Retention Designs, Inc., 2015b, Verdura Retaining Wall Design, Rancho Castera Walls 24 & 30, Project Number 1303-006, dated September 14, 2015 In accordance with your request and authorization, LGC Valley, Inc. (LGC) has performed a geotechnical evaluation of the proposed Verdura mechanically-stabilized Retaining Walls Numbers 24 and 30 within the Robertson Ranch/Rancho Costera project located in the City of Carlsbad, California. The Verdura Segmental Wall Plans, dated September 11, 2015, and the Wall Design Summary dated September 14, 2015 were prepared by Soil Retention Design, Inc. (SRD). The purpose of our evaluation was to review the plans and geotechnical soil parameters utilized in the design for conformance with the recommendations provided in the referenced geotechnical documents (LGC, 2014 ). Geotechnical review of the Verdura Retaining Wall design methodology was not performed as part of our review. However, global stability analysis of the slope containing the proposed Verdura 40 Retaining Walls was performed. Existing Geologic Conditions and Proposed Design Review of the geologic conditions in the general vicinity of Wall No. 24 indicates the west-facing slope along the east side of Robertson Road is a replacement fill soil consisting of compacted sandy soils. Review of the geologic conditions in the general vicinity of Wall No. 30 indicates the east-facing slope east of Lots 239 through 243 is a fill slope also comprised of sandy fill soils. Review of the retaining wall plans indicates Wall No. 24 consists of two retaining walls with the lower wall approximately 5 to 14 feet in height and the upper wall approximately 2 to 5 feet in height. The two walls are located approximately 20 feet apart. Wall No. 30 is approximately 5 to 10 feet in height. The face of the segmental retaining walls will have an inclination of 1 :4 (horizontal to vertical). 2420 Grand Avenue, Suite F2 •Vista• CA 92081 • (760) 599-7000 • Fax (760) 599-7007 . ' ' . The Verdura walls will be constructed with Verdura 40 blocks and Miragrid 8XT or 5XT geosynthetic reinforcement geogrids at approximate 24-inch vertical intervals. The length of the geogrids varies from 5 to 12 feet behind the walls and the geogrids will not be placed within the upper 24 to 40 inches of the walls. Back-drains will be installed behind each of the retaining walls and outletted to a suitable location in front of the walls. Conclusions and Recommendations Based on the current design of the Verdura Segmental Retaining Walls Number 24 and 30 (Soil Retention Design, 2015b) and the anticipated geotechnical conditions, it is our professional opinion that the proposed slope in the vicinity of the proposed retaining walls will have a static and pseudostatic factor-of-safety of 1.5 and 1.1 or greater, respectively, following the completion of the project provided the site is graded and constructed in accordance with the project geotechnical recommendations and that unforeseen geotechnical conditions are not encountered. LGC should provide observation and testing during preparation of the foundation soils and reinforced backfill as well as observation during the installation of the back-drains. If unforeseen geotechnical conditions are encountered, the project geotechnical consultant should evaluate the conditions and provide appropriate recommendations to ensure that the global stability of the slope and retaining wall have adequate static and pseudostatic factors-of-safety of at least 1.5 and 1.1, respectively. Closure This letter is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the design engineer and the necessary steps are taken to see that the information is implemented in the design and construction, as necessary. If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at (661) 702-8474. Respectfully submitted, LGC Valley, Inc. Randall Wagner, CEG 1612 Senior Project Geologist Distribution: ( 4) Addressee Project No. 133023-03 Basil Hattar, GE 2734 Principal Engineer Page2 October 8, 2015