The URL can be used to link to this page

Home My WebLink AboutCT 14-06; AFTON WAY; GEOTECHNICAL UPDATE LETTER PROPOSED AFTON WAY RESIDENTIAL DEVELOPMENT CARLSBAD, CALIFORNIA; PUD 14-09, HDP 14-05, DWG 495-9, DWG 495-9A, GR2016-0050, ROW 2016-0061, SWMP 16-26; 2016-11-18'• .. \/l-o .!11 ' ~li Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY November 18, 2016 Project No. 11436.001 Pebble Creek Companies. 301 W. 28th Street, Suite A National City, CA. 91950 Attention: Subject: Mr. Gary Arnold Geotechnical Review of Grading Plans with Retaining Walls Proposed Afton Way Residential Development Carlsbad, California References BHA, Inc, 2016, Grading Plans for Afton Way, Sheets 1 through 14, Drawing Number 495-9A, received November 18, 2016 Leighton and Associates, Inc., 2016a, Geotechnical Update Letter, Proposed Afton Way Residential Development, Carlsbad, California, Project Number · 11436.001, dated October 5, 2016 Leighton and Associates, Inc., 2016b, Addendum 1 -Clarified Geotechnical Recommendations, Proposed Afton Way Residential Development, Carlsbad, California, Project Number 11436.001, dated November 14, 2016 In accordance with your request, we have performed a geotechnical review of the referenced grading plans with retaining walls (BHA, Inc, 2016) for the subject project. Our review was performed to identify potential conflicts with the intent of the referenced geotechnical document. The retaining walls included proposed CMU retaining walls associated with the Biofiltration Basin designed by Swanson & Associates Engineering, and twelve mechanically stabilized earth (MSE) retaining walls designed by Red One 3934 Murphy Canyon Road, Suite B205 111 San Diego, CA 92123-4425 858.292.8030 111 Fax 858.292.0771 111 www.leightongroup.com 11436.001 Engineering, Inc. Based on our review of the plans and provide calculations, they appear to be in general conformance with our recommendations (Leighton and Associates, 2016a and 2016b). In addition, we performed global slope stability analyses on three selected MSE wall sections: 1. Wall #1 (Sta 2+45); 2. Tiered Walls #2 (Sta 2+30) and #3 (Sta 1 +90); and 3. Wall #12 (Sta 2+00) Our global slope stability analyses of the wall and the slope sections were performed with the computer program Slide Version 7 .014. The analyses were performed on a typical cross section, which included 2 to 1 fill and or cut slopes and the MSE wall. A pseudo- static analysis was also performed using total stress procedures and a pseudo-static seismic coefficient (kh) of 0.15. The results of our analysis indicate that the slope with the wall has a global stability factor of safety greater than 1.5 for a static condition and a factor of safety greater than 1.15 for a pseudo-static condition. Plots of the analyses are provided as an attachment. If unforeseen geotechnical conditions are encountered during grading, 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 a factor-of-safety of at least 1.50. The conclusions and recommendations presented in this review are based in part upon data that were obtained from a limited number of observations, site visits, excavations, samples, and tests. Such information is by necessity incomplete. The nature of many sites is such that differing geotechnical or geological conditions can and do occur. Therefore, the findings, conclusions, and recommendations presented in this report can be relied upon only if Leighton has the opportunity to observe the subsurface conditions during grading and construction of the project. Only with these observations are we able to confirm that our preliminary findings are representative for this site. -2- 11436.001 If you hpve any questions regarding our letter, please do not hesitate to contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. William D. Olson, RCE 45283 Associate Engineer Attachments: Plots of Global Slope Stability Analyses Distribution: (1) Addressee, via email (1) Swanson & Associates Engineering, Attn: Mr. Mark Swanson, via email -3- 0 a> N j re-1 0 I'-N 0 (0 N 0 IO N j 10 UDEINTE]lPRET 7.014 Leiahton ,-------- Results Method of Analysis: spencer Factor of Safety: 2.526 ~ ~ I 30 40 50 Project !Analysis Description Drawn By SMM Scale Date 9/20/2016 Condition Afu I 110 I Mohr-Coulomb I 150 I 30 Qvop • 120 Mohr-Coulomb 100 38 1,-- Tsa D 120 Mohr-Coulomb 400 28 - Af I.I 120 I Mohr-Coulomb I 100 I 30 - Qc 1•1 120 I Mohr-Coulomb I 200 I 28 ~ 60 70 80 90 Afton Way RW# 1 STA 2+45 1:100 Company Leighton File Name RW 1 STA 2+45.slim -l 0 a> N ~ ~ 0 r-N 0 (0 N 0 U> N j i i \ ~-----___ \ 10 L1DEINTERPRET7.014 Leia ,-, Yes I 5 ,------------ Results Method of Analysis: spencer Factor of Safety: 1.845 '- "-I 30 40 50 Projeet !Analysis Description Drawn By SMM Seate Date 9/20/2016 Condition Afu I 110 I Mohr-Coulomb I 150 I 30 Qvop .I 120 I Mohr-Coulomb I 100 I 38 Tsa DI 120 I Mohr-Coulomb I 400 I 28 I I''--_ _/ Af 120 Mohr-Coulomb 100 30 Qc 120 Mohr-Coulomb 200 28 / ,,1' ~ 60 70 80 90 Afton Way RW# 1 STA 2+45 1:100 Company Leighton File Name RW 1 STA 2+45 -pseudo static.slim g N Support 1 I • I GeoTextile I Passive (Method B) I Yes I 5 I 30 I Linear I :arallel to I Slope Face I Reinforcement 100 I 1654 Support 2 I • I GeoTextile I Passive (Method B) I Yes I 5 I 30 I Linear I :arallel to I Slope Face I Reinforcement 100 I 3497 0 r-N Results Method of Analysis: spencer j\,_j 01 FactorofSafety: 1.817 Qvop • 120 Mohr-Coulomb 100 38 • Tsa I 120 I Mohr-Coulomb I 400 I 28 Af .I 120 I Mohr-Coulomb I 100 I 30 - Qc I I 120 I Mohr-Coulomb I 200 I 28 -20 -10 0 10 20 30 40 50 60 Project Afton Way 11436.001 !Analysis Description RW# 2 STA 2+30 and RW# 3 STA 1+90 Drawn By SMM Scale 1:100 Company Leighton LIDEINTERPRET 7.014 hton Date 11/14/16 Condition File Name RW 2 STA 2+30 and RW 3 STA 1+90.slim g N Support 1 I • I GeoTextile I Passive (Method B) I Yes I 5 I 30 I Linear I Parallel to Reinforcement Slope Face 100 1654 ~015 Support 2 I • I GeoTextile I Passive (Method B) I Yes I 5 I 30 I Linear I Parallel to Slope Face 100 3497 Reinforcement " 0 I'-N Results Afu I 110 I Mohr-Coulomb I 150 I 30 Method of Analysis: spencer Factor of Safety: 1.405 Qvop .I 120 I Mohr-Coulomb I 100 I 38 • Tsa D1 120 I Mohr-Coulomb I 400 I 28 - Af I.I 120 I Mohr-Coulomb I 100 I 30 - Qc I I 120 I Mohr-Coulomb I 200 I 28 N -20 -10 0 10 20 30 40 50 60 Project Afton Way 11436.001 !Analysis Description RW# 2 STA 2+30 and RW# 3 STA 1+90 Drawn By SMM Scale l: lOO ICom~ny Leighton LIDEINTERPRET 7.014 Date 11/14/16 Condition FiteNameRW 2 STA 2+30 and RW 3 STA 1+90 -pseudo static.slim 0 0 (") ~ 0 (0 C\I Support 1 0 10 LIDEINTERPRET 7.014 Leighton • I GeoTextile I Passive (Method B) I Results Method of Analysis: spencer I Factor of Safety: 2.192 20 Project !Analysis Description Drawn By SMM Date 11/15/2013 Yes I Qvop Tsa Af Qc Afu 30 40 Scale Condition 1·1 I Mohr-Coulomb I 100 I 38 I None 120 D1 120 I Mohr-Coulomb I 400 I 28 I None - I. 120 Mohr-Coulomb I 100 I 30 I None • 120 Mohr-Coulomb I 200 I 28 I None 110 Mohr-Coulomb I 150 I 30 I None 50 60 70 80 Afton Way 11436.001 RW# 12 STA 2+00 1:100 Company Leighton File Name RW 12 STA 2+00.slim 0 0 (') Support 1 • I GeoTextile I Passive (Method B) Yes ~ I Results Method of Analysis: spencer Factor of Safety: 1. 728 I 0 10 20 Project !Analysis Description Drawn By SMM UDE1NTERPRET7.014 hton Date 11/15/2013 5 30 I Qvop 30 40 Scale Condition r·,, 1654 1•1 120 I Mohr-Coulomb I 100 I 38 I None -D1 120 I Mohr-Coulomb I 400 I 28 I None -• 120 Mohr-Coulomb I 100 I 30 I None • 120 Mohr-Coulomb 200 28 None 110 Mohr-Coulomb 150 30 None '(11""' .;:.~" 50 60 70 80 Afton Way 11436.001 RW# 12 STA 2+00 1:100 Company Leighton File Name RW 12 STA 2+00 -pseudo static.slim