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Earth Mechanics, Inc. <br />xWolmum awming <br />TECHNICAL MEMORANDUM <br />EMI PROJECT NO: 11 -123 <br />DATE: September 13, 2011 <br />PREPARED FOR: Mohan Char, Ph.D., P.B. / ABCOM <br />PREPARED BY: Ranjan Gunaranjan and Lino Cheang / Barth Mechanics, Inc. (EMI) <br />SUBJECT: Santa Ana Boulevard Grade Separation <br />City of Santa Ana, Orange County, California <br />Structure Preliminary Geotechnical Report (SPGR) <br />Introduction <br />This memorandum has been prepared to provide the necessary geotechnical information to assist <br />the structural designers in the type selection process for the Santa Ana Boulevard Grade <br />Separation (GS) at Santa Ana Boulevard and Metrolink Railroad intersection. The content of this <br />memorandum follows Caltrans Foundation Report Preparation for Bridge Foundations (Caltrans, <br />2009). It includes preliminary geotechnical, seismic, and foundation recommendations for the <br />subject GS and the adjoining retaining walls. The recommendations provided in this <br />memorandum are based on subsurface information contained on the as -built Log -of -Test- Borings <br />(LOTB) of three nearby structures: Grand Avenue Undercrossing (Bridge No. 55- 671L), Lincoln <br />Avenue Underpass (Bridge No. 55 -672), and Lincoln Avenue Overcrossing (Bridge No. 55 -675). <br />These nearby bridges are located less than 0.3 mile from the proposed GS. An additional <br />geotechnical investigation will need to be performed during the PS &E phase; therefore, the <br />following recommendations may change when additional information becomes available. <br />Project Description <br />As presented in the preliminary plan provided by the designers, the existing Santa Ana <br />Boulevard, which intersects at -grade with the existing Metrolink railroad tracks, will be lowered <br />under the railroad tracks to have a minimum vertical clearance of about 16.5 feet. The horizontal <br />alignment of Santa Ana Boulevard will also be shifted about 30 feet to the south due to the <br />presence of a utility corridor. Retaining walls will be constructed on the north side of the Santa <br />Ana Boulevard in -line with the bridge abutment (Abutment 5). A portion of the retaining wall <br />located at the depressed roadway is proposed to be a Type SW retaining wall and the remaining <br />portion is proposed to be Caltrans Standard Type 1 retaining wall. Based on the information <br />provided by the structural designers, Type SW retaining wall is a U -shape cantilever wall that <br />will support the sidewalk in the middle of the "U ". <br />17800 Newhope Street, Suite B, Fountain Valley i ia�220 Tel: (714) 751 -3826, Fax: (714) 751 -3928 <br />