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Home My WebLink AboutCT 82-24; Sea Gate Village; Soils Report; 1991-03-12- - - - - .- - - - - - - - .- - .- - - ENGINEERING DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive Carlsbad, CA92009-4859 c.l -P.cz.?J. 26 SURFICIAL SLOPE FAILURE Slope Adjacent to Building No. 27 North End of Sea Cliff Drive Sea Gate Village Carlsbad, California 3- r2--'iI CUk 325-T ii HRHERINGTON ENGINEERING, INC. - - - - - - ,- - - - - HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS March 12, 1991 Project No. 384.3 Grupe Management Company 2291 W. March Lane, Suite 200B P.O. Box 7576 Stockton, CA 95207 Attention: Ms. Diana Santiago Subject: SURFICIAL SLOPE FAILURE Slope Adjacent to Building No. 27 North End of Sea Cliff Drive Sea Gate Village Carlsbad, California Dear Ms. Santiago: In accordance with your request, we have performed a reconnaissance of a slope failure at the subject site. The purpose of the reconnaissance was to determine and map the lateral extent and depth of the slope failure and to provide recommendations for slope repair. SITE DESCRIPTION The subject slope failure is located within a portion of the slope that extends along the northwest side of Lot 11 at the north end of Sea Cliff Drive in the Sea Gate Village apartment complex, Carlsbad, California (see Geotechnical Map, Figure 1). The failure has occurred within the upper portion of the approximately 50 feet high, approximately 2-l/2:1 to 2:1 (horizontal to vertical), northwest facing slope that lies adjacent to the northwest corner of Building No. 27. The observed failure consists of an area approximately 75 feet (parallel to the slope) by approximately 30 feet to 50 feet (perpendicular to the slope). The limits of the slope failure are shown on the attached Geotechnical Map, Figure 1. We understand that the slope failure occurred as the consequence of broken irrigation line which saturated the area. 5245 AVENIDA ENCINAS . SUITE G l CARLSBAD, CALIFORNIA 92006 l (619) 931.1917 - - - SURFICIAL SLOPE FAILURE Project No. 384.3 March 12, 1991 Page 2 - - - - - - - - - - - - - - - GEOMGIC CONDITIONS Review of the "Project Grading Report...," and site "Grading Plans...," (see References) indicates that the slope northwest of and adjacent to Building No. 27 is apparently a fill over natural slope. Review of the References also indicates that, within the vicinity of the slope failure, the upper approximately 10 to 20 feet of the slope is comprised of compacted fill soils. The fill soils are reportedly underlain by sedimentary bedrock deposits of the Santiago Formation. Based on our reconnaissance and field mapping, the subject slope af%%ed"pi~ar& “earthflow”. to be relatively shallow in depth and can best be It is also apparent that failure is confined generally to the fill portion of the slope. The head scarp of the flow coincides basically with the top of slope and berm. Debris from the flow appears to extend down as much as approximately 50 feet from the head scarp. The depth of the failure, measured from the previously existing slope face, is approximately 3-l/2 feet. The attached Cross Section A-A', Figure 2, depicts existing and pre-failure conditions. CONCLUSIONS Our reconnaissance and field mapping suggests that the subject slope failure is a shallow earthflow and is confined primarily to the compacted fill portion, or uppermost portion, of the slope. The cause of this failure is most likely the reported broken irrigation line, which caused saturated soil conditions and eventual slope instability. REPAIR RECOMMENDATIONS Repair and reconstruction of the subject slope failure should essentially consist of removing the existing failure debris and replacing the material as compacted fill in order to achieve pre- failure grades and a slope ratio no steeper than 2:l (horizontal to vertical). The existing failure debris is presently wet to saturated and thus unsuitable for use as compacted fill at this time. This soil should be removed or spread out to aerate and dry so that it may be used as compacted fill at a later time. Prior to re-building the slope, a fill key should be excavated at the toe of slope to be repaired. The key should extend at least 2 feet into competent, undisturbed soils, and have a width of at HETHERINGTON ENGINEERING, INC. - .- ,- - - - - ,>’ - - - - - - - - - SURFICIAL SLOPE FAILURE Project No. 384.3 March 12, 1991 Page 3 least 10 feet. During the subsequent filling and rebuilding of the slope, continuous benching should be performed into competent soils of the existing slope in order to remove any failure debris and to provide a suitable surface for fill placement. Fill soils should be placed in 6 to 8-inch lifts, moisture conditioned and compacted to at least 90 percent relative compaction. All removals of the existing slope failure and subsequent earthwork should be inspected and tested as necessary by the Geotechnical Consultant. This opportunity to be of service is appreciated. If you have any questions, please call. Sincerely, HETHERINGTON EN]GINEERING, INC. /' // / ,,/ DANNY COHEN c-' Civil Engineer 41937 (expires 3/31/92) HETHERINGTON ENGINEERING, INC. - - - .- - - - - - - ,- - - - REFERENCES Land Space Engineering Co., Grading Plans For: Carlsbad Tract No. 82-24, Sea Gate Village, dated July 3, 1985. Pacific Soils Engineering, Inc., Project Grading Report for Sea Gate Village, Carlsbad Tract No. 82-24 in the City of Carlsbad, California, dated November 27, 1985. HETHERINGTON ENGINEERING, INC. - - - - - .- .- - .- - .- - - - - - .- SCALE: 1’:30’ GEOTECHNICAL MAP HETHERINCTON ENGINEERING SLOPE FAILURE. SEA GATE VILLAGE GEOTECHNICAL CONSULTANTS PROJECT NO. 384.2 I FIGURE NO. i ! ii : > : . , n > D n : J 120 00 60 30 SEA CLkF DRIVE, I I I I I I I I I I I I I I I I I GARAQE AREAS LIMITS OF SLOQ. 27/ 1 + ]r / J GROUND SURFACE PRIOR TO F’AILuRE \,;r , //’ - L/ APPROXIMATE FAILURE SURFACE A 1 TRENd ‘N40 W A’ HORIZONTAL AND VERTICAL SCALE: 1’.30’ eo 60 30 I