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Home My WebLink AboutCT 2019-0006; 2690 ROOSEVELT; UPDATED GEOTECHNICAL RECOMMENDATIONS - DECEMBER 18, 2019; 2019-12-18GEOCON INCORPORATED GEOTECHNICAL ■ ENVIRONMENTAL. MATE RI ALSO Project No. G2245-52-0 I December 18, 2019 Kitchell Development Company 1555 Camino Del Mar, Suite 307 Del Mar, California 92014 Attention: Subject: Mr. Mame Bouillon UPDATE GEOTECHNICAL RECOMMENDATIONS 2690 ROOSEVELT STREET CARLSBAD, CALIFORNIA ~~ity of Carlsbad MAR 02 2020 ~_anning Division References: 1. Geotechnical Investigation, 2690 Roosevelt Street, Carlsbad, California, prepared by Geocon Incorporated, dated April 8, 2019 (Project No. G2245-52-0l). 2. [Architectural Plans for} 2690 Roosevelt Street, Carlsbad, California, prepared by Starck Architecture and Planning, dated November 22, 2019 (Project No. G2068- l l 04). Dear Mr. Bouillon: In accordance with the request of Damien Leyva of Starck Architecture and Planning, we prepared this letter to provide updated recommendations for the 2690 Roosevelt Street residential project located in the City of Carlsbad, California. Specifically, have included 2019 California Building Code seismic design criteria. The remainder of the recommendations presents in the referenced geotechnical investigation report remain applicable to the design and construction of the proposed project. PROJECT DESCRIPTION The subject site is located north of the intersection of Roosevelt Street and Beech Avenue m a residential area in the City of Carlsbad, California. The site currently consists of a single-family residence that has been modified to commercial space. The site is accessed from Roosevelt Street by a concrete drive to north and a gravel driveway to the south of the structure with parking available to the east of the building. The property slopes gently to the northwest with elevations ranging from about 41 to 47 feet above Mean Sea Level (MSL). Overhead utility lines exist fronting Roosevelt Street. We understand proposed development will consist of demolishing the existing structure and constructing three, 3-story, residential buildings (Buildings A through C) consisting of 9 units with 6960 Flanders Drive ■ San Diego, California 92121 -2974 ■ Telephone 858.558.6900 ■ Fax 858.558.6159 accommodating garages, driveways, utilities, landscaping and hardscape. We expect cuts and fills less than approximately 3 feet will be required to achieve planned grades, and we expect the planned structures will be supported on shallow foundations with a concrete-slab-on-grade. We previously performed the referenced geotechnical investigation report and encountered approximately 1 to 3 feet of undocumented fill (Qudf) overlying Old Paralic Deposits (Qop). SEISMIC DESIGN CRITERIA-2019 CALIFORNIA BUILDING CODE We understand the plans will be submitted using the 2019 California Building Code (CBC). Table 1 summarizes site-specific design criteria obtained from the 2019 California Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7-16), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the computer program Seismic Design Maps, provided by the Structural Engineers Association (SEA) to calculate the seismic design parameters. The short spectral response uses a period of 0.2 second. We evaluated the Site Class based on the discussion in Section 1613.2.2 of the 20 19 CBC and Table 20.3-1 of ASCE 7-16. The values presented herein are for the risk-targeted maximum considered earthquake (MCfa). Sites designated as Site Class D, E and F may require additional analyses if requested by the project structural engineer and client. TABLE 1 2019 CBC SEISMIC DESIGN PARAMETERS I Parameter I Value I 2019 CBC Reference Site Class C Section 1613 .2.2 MCER Ground Motion Spectral Response Acceleration -1.077g Figure 161 3.2.1(1) Class B (short), Ss MCER Ground Motion Spectral Response Acceleration -0.390g Figure 1613.2.1(2) Class B (I sec), S, Site Coefficient, FA 1.200 Table 1613.2.3(1) Site Coefficient, Fv 1.500* Table 1613.2 .3(2) Site Class Modified MCER Spectral Response 1.292g Section 1613.2.3 (Eqn Acceleration (short), SMs 16-36) Site Class Modified MCER Spectral Response 0.5 84g* Section 1613.2.3 (Eqn Acceleration -(I sec), SM1 16-37) 5% Damped Design 0.861g Section 161 3.2.4 (Eqn Spectral Response Acceleration (short), Sos 16-38) 5% Damped Design 0.390g* Section 1613.2.4 (Eqn Spectral Response Acceleration (1 sec), So, 16-39) * Using the code-based values presented in this table, in lieu of a performing a ground motion hazard analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed by the project structural engineer. Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis should be performed for projects for Site Class "E" sites with Ss greater than or equal to I .0g and for Site Class "D" and "E" sites with SI greater than 0.2g. Section 11.4.8 also provides exceptions which indicates that the ground motion hazard analysis may be waived provided the exceptions are followed. Geocon Project 1\/o. G22➔5-52-0 I -2 -December 18. 2019 Table 2 presents the mapped maximum considered geometric mean (MCE0) se1sm1c design parameters for projects located in Seismic Design Categories of D through F in accordance with ASCE 7-16. TABLE 2 ASCE 7-16 PEAK GROUND ACCELERATION I Parameter Value I ASCE 7-16 Reference I Site Class C Section 161 3.2.2 (2019 CBC) Mapped MCEa Peak Ground Acceleration, 0.475g Figure 22-7 PGA Site Coefficient, FraA l.200 Table 11.8-l Site Class Modified MCEa Peak Ground 0.570g Section l l.8.3 (Eqn l l.8-1) Acceleration, PGAM Conformance to the criteria in Tables l and 2 for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur if a large earthquake occurs. The primary goal of seismic design is to protect life, not to avoid all damage, since such design may be economically prohibitive. The project structural engineer and architect should evaluate the appropriate Risk Category and Seismic Design Category for the planned structures. The values presented herein assume a Risk Category of II and resulting in a Seismic Design Category D. Table 3 presents a summary of the risk categories. TABLE 3 ASCE 7-16 RISK CATEGORIES I Risk I Building Use I Examples Category I Low risk to Human Life at Failure Barn, Storage Shelter II Nominal Risk to Human Life at Failure Residential, Commercial and Industrial Buildings (Bui ldings Not Designated as I, III or IV) Theaters, Lecture Halls, Dining Halls, Schools, III Substantial Risk to Human Life at Failure Prisons, Small Healthcare Facilities, Infrastructure Plants, Storage for Explosives/Toxins Hazardous Material Facilities, Hospitals, Fire and IV Essential Facilities Rescue, Emergency Shelters, Police Stations, Power Stations, Aviation Control Facilities, National Defense, Water Storage Geocon Project 1\/o. G:22➔5-52-0 I -3 -December 18, 20 19 J • I - Should you have any questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON IN CORPORA TED ~~z ,,::!::;;;~ A~don RCE 83227 ---:.::.-,,,,;;. GE 2714 LER:SFW:am _ ( e-mail) Addressee Geocon Project No. G2245-52-0 I -4 -December 18, 20 19