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HomeMy WebLinkAboutCDP 09-11; GOETZ EMERGENCY SEAWALL; THIRD PARTY GEOTECHNICAL REVIEW OF PROPOSED RESTORATION COASTAL BLUFF FAILURE AT 5323 AND 5327 CARLSBAD BOULEVARD CARLSBAD, CALIFORNIA; 2009-03-24( March 24, 2009 Project No. 106560001 Mr. Glen K. Van Peski, P.E. Senior Civil Engineer -Development Services City of Carlsbad 1635 Faraday Avenue Carlsbad, California 92008 Subject: Third Party Geotechnical Review of Proposed Restoration Coastal Bluff Failure at ~323 and 5327 Carlsbad Boulevard Carlsbad, California Dear Mr. Van Peski: ·RECEIVED MAR 3 o 2009 ENGINEERING DEPARTMENT At your request and the authorization of the City of Carlsbad (the City), we have performed a third party (or peer) review of the project documents submitted to the City for the referenced bluff restoration project. Failure of the coastal bluffs at 5323 and 5327 Carlsbad Boulevard occurred in December 2008. Following that occurrence GeoSoils, Inc. (GSI) and Charles J. Randle were retained by the property owners to provide assistance in designing an emergency repair to the bluffs. From the reviewed documents, it is our understanding that GSI is the soils engineer of record for the project and Charles J. Randle is the engineer of work for the project. A list of the documents submitted to Ninyo & Moore by the City for our review is at- tached. Our general scope of services was to review geotechnical reports and construction drawings prepared by the above named entities and check them for compliance with minimum code standards, completeness, factual errors, consistency of data with the conclusions offered, and conformance to the standards of geotechnical practice. SCOPE OF SERVICES Our specific scope of services included the following: • Review of project documents prepared by GSI and Charles J. Randle submitted to the City. 571 O Ruffin Road • San Diego, California 921 23 • Phone (858) 57 6-1 000 • Fax (858) 57 6-9600 San Diego • Irvine • Rancho Cucamonga • Los Angeles • Oakland • Las Vegas • Phoenix • Denver • El Paso • Tucson \ . Coastal Bluff Failure at 5323 and 5327 Carlsbad Boulevard Carlsbad, California ( March 24, 2009 ProjectNo. 106560001 • Review of available published geologic and geotechnical maps and reports pertinent to the site area. • Reconnaissance of the site by a Certified Engineering Geologist from our offices. • Preparation of this letter report documenting the results of our field and engineering review of the provided reports and plans. COMMENTS REGARDING THE REVIEWED DOCUMENTS Based on our background review and field observations the geologic conditions at the project site appear to be as described in the referenced documents. However, none of the documents in the submittal are signed or sealed by a California Certified Engineering Geologist (CEG). Documen- tation, that is signed and sealed by a CEG, should be provided by the Consultant indicating that the geologic conditions are those that are assumed in the proposed bluff repair. A geotechnical evaluation report for the project indicating the subsurface exploration locations, boring and/or test pit logs, sampling locations and procedures, and laboratory testing was not in- cluded in the referenced documents. The submittal for the bluff repair should include a formal, comprehensive geotechnical evaluation report for the project. Based on our review of the Structural Calculations for Bluff Repair prepared by Randle (2009), the calculations were prepared in conformance with the results of the direct shear test data sub- mitted by GSI (2009b ). However, the basis for applying an adhesion value of 1.66 ksf for tieback capacity and the Factor of Safety used in the calculations was not included. In addition, the sub- mittal should be based on slope stability analyses and indicate the Factor of Safety under the improved conditions for the project. We suggest that the results of the slope stability analysis be included in the geotechnical evaluation report, requested above. A letter should be provided by GSI indicating that they have reviewed the structural calculations and plans for the bluff repair and that their geotechnical recommendations and design parameters have been properly incorporated into the design. Further, GSI should comment on type of back- drain(s) recommended for the wall. The reviewed plans indicate that a five foot excavation should 106560001 L.doc 2 1(in90&1ftoore ( . . Coastal Bluff Failure at 5323 and 5327 Carlsbad Boulevard Carlsbad, California March 24, 2009 Project No. 106560001 occur behind the wall. However, without supporting geotechnical data the recommended five foot excavation may not be adequate to remove the landslide materials behind the wall. The plans also indicate that gravel or slurry may be used for backfill behind the wall but no specifications for these materials are presented. Slurry backfill may not be compatible with the proposed drainage system. We appreciate the opportunity to be of service on this project. Respectfully submitted, NINYO & MOORE Andres Bernal, G.E. Senior Project Engineer Rl/AB/gg Attachment: References Distribution: (1) Addressee 106560001 L.doc R~~~ Chief Engineering Geologist 3 1(in90&1(toore ,,· C ,l ' ( ' ' Coastal Bluff Failure at 5323 and 5327 Carlsbad Boulevard March 24, 2009 Project No. 106560001 Carlsbad, California REFERENCES GeoSoils, Inc., 2008, Bluff Collapse Inspection 5323 and 5327 Carlsbad Boulevard, Carlsbad: dated December 24. GeoSoils, Inc., 2009a, Application for an Emergency Coastal Development Permit for Proposed Bluff Restoration of Recent Coastal Bluff Failure at 5323 and 5327 Carlsbad Boulevard, Carlsbad, San Diego County, California: dated January 20. GeoSoils, Inc., 2009b, Memorandum; Summary of Soil Strength Testing, Emergency Bluff Re- sto-ration, 5323 and 5327 Carlsbad Boulevard, San Diego County, California: dated February 19. GeoSoils, Inc., 2009c, Emergency Update, Geotechnical Design Parameters and Plans for Emergency Coastal Development Permit, Proposed Bluff Restoration of Recent and On- going Coastal Bluff Failure at 5323 and 5327 Carlsbad Boulevard, Carlsbad, San Diego County, California: dated February 27. Randle, Charles, J. (PE), 2009, Preliminary Plans and Structural Calculations for Bluff Repair, 5327 & 5323 Carlsbad Blvd., Carlsbad, California: dated 1-10-09 (Last revision 2-23-09). 106560001 L.doc I of I