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Home My WebLink About; Stagecoach Park Stability Analysis and Addl Recs; Stagecoach Park Stability Analysis and Addl Recommendations; 1986-05-15.-J/f/ GEOCON I N C O R P O R A T E i> ENGINEERS AND GEOLOGISTS • CONSULTANTS IN THE APPLIED EARTH SCIENCES File No. D-3480-J02 May 15, 1986 City of Carlsbad, Engineering Department 1200 Elm Avenue ' Carlsbad, California 92008 Attention: . Mr. Donald E. "Gene" Donovan 'Subject: STAGECOACH PARK CARLSBAD, CALIFORNIA STABILITY ANALYSES AND ADDITIONAL RECOMMENDATIONS Gentlemen: In response to your request, we. have performed additional engineering services on the subject project. These services included reviewing our files pertaining to the project, performing additional stability analyses and providing recommendations based on the stability analyses. We have reviewed the following reports and plans: • "Supplemental Geotechnical Investigation, Stagecoach Park, Carlsbad, California" prepared by Geocon, Incorporated and dated April 18, 1986. « "Final Report of Testing and Observation Services During Grading Operations for Stagecoach Park, Carlsbad, California" prepared ' by Geocon, Incorporated and dated December 5, 1985. • "Geotechnical Investigation for Stagecoach Park, Carlsbad, Califor- nia" prepared by Geocon, Incorporated, dated July 5, 1985. • Boring Logs entitled "Stagecoach Park" prepared by Woodward Clyde Consultants, dated April 25, 1986. 9530 DOWDY.DRIVE • SAN DIEGO, CALIFORNIA 92126 •. PHONE (619) 695-2880 File No. D-3480-J02 May 15, 1986 • The purpose of our additional work was to provide stability analyses of the approximately 20 foot high 2.0 to 1.0 (horizontal to vertical) inclined cut'slope at the northeastern corner of the site. Several studies have been performed which indicate the presence of sheared claystones. and siltstones within the Tertiary Age Del Mar Formation materials which comprise the slope and are the: predominant soil materials in the general site area. The later studies indicated that no deep seated landslide or continuous shear zones were present within the slope or the area immediately east and southeast' of the slope extending across Mision Estancia. There were, however, many shears and fractures characteristic of this particular formation. The shears and fractures were generally oriented toward the south and southeast which; is considered a favorable orientation in regard.to slope stability for the on-site cut slope. Stability analyses utilizing both assumed shear strength parameters and parameters based on slow direct shear tests were performed to analyze both the deep seated and shallow stability of the slope. The analyses, utilizing a computer program entitled STABL4 developed at the University of Indiana, indicates a calculated factor of safety of 1.5 against deep-seated instability such as from a landslide. However,• the analysis does indicate a calculated factor of safety of less than 1.5 against shallow slope instability as a result of the sheared and fractured claystones. Although,, in our opinion, the potential for shallow slope instability is considered to be low there is a potential for sloughing failure or small block failure of the cut slope. A failure could extend into the northern portions of Mision Estancia, but the potential for extending to the east bound lanes is considered very low. To reduce the potential for shallow slope instability it is recommended that a "Stability Fill" be constructed within the cut slope. The stability fill would consist of excavating the outer face of the slope for a horizontal distance of at least 15 feet (approximately one "equipments width"). The excavation should be extended for approximately 700 feet of the cut slope. The. excavated material should ;then be properly compacted in accordance with project specifications. All earthwork should be observed by and all compacted fill tested by representatives of Ge9con, Incorporated. Figure 1 indicates the approximate limits of the recommended stability fill, and Figure 2 indicates a cross- section of the stability fill. GEXXXJN INCORPORATED File No. D-3480-J02 May 15, 1986 . It is recommended that a subdrain be installed at the rear of the excavation and dutletted to a controlled drainage system. The subdrain would consist of • a 4-inch diameter perforated ABS or PVC pipe surrounded by Class II filter material extending at least 4 feet, up the back slope of the excavation. As an' alternate to .the . filter gravel a drainage board such as "Miradrain" could be used. If you have any questions please contact the undersigned. Very truly yours, GliOC^N, INCORPORATED Ja RC rs E. Likins 17030 MRR:JEL:mr (4) addressee (1) Recreation Systems, Inc. Attn: Mr. Steven Lang GECXm INCORPORATED INCORPORATED ENGINEERS AND GEOLOGISTS • CONSULTANTS IN THE APPLIED EARTH SCIENCES File No. D-3480-JO2 April 22, 1986 City of Carlsbad Engineering Department 1200 Elm Avenue CarisWd, California ,92008 Attention: Mr. D.E. "Gene" Donovan Subject: STAGECOACH PARK CARLSBAD, ^CALIFORNIA CONSULTATION Gentlemen: In response to your request we are' providing additional information in regard to the grading operations for the subject project'. Prior to the start of the grading operations it was agreed that Geocon, Incorporated would not be involved in evaluation of quantities of remedial grading. Those quantity determinations would be perform.ed by the Grading Contractor and representatives of the City of Carlsbad. However, during grading our Field Techinician obtained "spot" elevations at the bottom of the buttress and bedrock creep cleanout areas and recorded these elevations on his set of gradingiplans. In addition, the technician recorded the ap- proximate limits of the remedial grading areas. Copies of the Technicla-iis grading plans with the indicated information were sent to Mr. Ray Lewis on March 27, 1986 at his request to aid in his estimation of the remedial grading quantities. We have not performed any grading quantitj' estimates. Additional photocopies of the grading plans with the spot elevations can be prepared if requested. The elevations and limits of remedial grading indicated on the plans by our Technician are approximate and were prepared for information only. They-were not intended to be used for volume calculations. . If you. have any questions or if we may be of further service, please contact the unersigned. . ; Very truly yours, GEOCON,•INCORPORATED James E. Likins RCE 17030 Michael R. Rahilly RCE 28i88 m §M)=§9W0Y DRIVE • SAN DIEGO, CALIFO^f'I'Ii^^^Ig§s%e pHONE (619) 695-2880 GEOCON INCORPORATED ENGINEERS AND GEOLOGISTS • CONSULTANTS IN THE APPLIED EARTH SCIENCES File No. D-3480-J02 April 22, 1986 city of Carlsbad Engineering Department 1200 Elm Avenue Carlsbad, California 92008 Attention: Mr. D.E. "Gene" Donovan Subject: STAGECOACH PARK CARLSBAD, ;CALIFORNIA CONSULTATION Gentlemen: In response to your request we are providing additional information in regard to the grading operations for the subject project. Prior to the start of the grading operations it was agreed that Geocon, Incorporated would not be involved in evaluation of quantities of remedial grading. Those quantity determinations would be performed by the Grading Contractor and representatives of the City of Carlsbad. However, during grading our Field Techinician obtained "spot" lelevations at the bottom of the buttress and bedrock creep cleanout areas and recorded these elevations on his set of grading plans. In addition, the technician recorded the ap- proximate limits of the remedial grading areas:. Copies of the Technicians grading plans with the indicated information were sent to Mr. Ray Lewis on March 27, 1986 at his request to aid in his estimation of the remedial grading quantities. We have not performed any grading quantity estimates. Additional photocopies of the grading plans with the spot elevations can be prepared if requested. The elevations and limits of remedial grading indicated on the plans by our Technician are approximate- and were prepared for information only. They were not intended to be used for volume calculations. , If you.have any questions or if we may be of further service, please contact the unersigned. Very truly yours, : GEOCON, INCORPORATED James E. Likins RCE 17030 Michael R. Rahilly RCE 28188 =5!hv¥yV DRIVE • SAN DIEGO, CALIFoO^X^^im^''*^ PHONE (619) 695-2880 ENGINEERS AND GEOLOGISTS • CONSULTANTS IN THE APPLIED EARTH SCIENCES File No. D-3480-JO2 April 22, 1986 City of Carlsbad Engineering Department 1200 Elm Avenue Carlsbad, California 92008 Attention: Mr. D.E. "Gene" Donovan Subject: ' STAGECOACH PARK CARLSBAD, ^CALIFORNIA CONSULTATION Gentlemen: In response to your request we are providing additional information in regard to the grading operations for the subject project. Prior to the start of the grading operations it was agreed that Geocon, Incorporated would not be involved in evaluation of quantities of remedial grading. Those quantity determinations would be performed by the Grading Contractor and representatives of the City of Carlsbad. However, during grading our Field Techinician obtained' "spot" elevations at the bottom of the buttress and bedrock creep cleanout areas and recorded these elevations on his set of grading plans. In addition, the technician recorded the ap- proximate limits of the remedial grading areas. Copies of the Technicians grading plans with the indicated information were sent to Mr. Ray Lewis on March 27, 1986 at his request to aid in his estimation of the remedial grading quantities. We have not performed any grading quantity estimates. Additional photocopies of the grading plans with the spot: elevations can be prepared if requested. The elevations and limits of remedial grading indicated on the plans by our Technician are approximate and were prepared for information only. They were not intended to be used for volume calculations. If you. have any questions or if we may be of further service; please contact the unersigned. Very truly yours, GEOCON, INCORPORATED James E. Likins RCE 17030 Michael R. Rahilly RCE 28188 • Si iJ&M5Y DRIVE . SAN DIEGO, CALIFOM^M^tBse^ PHONE (619) 695-2880 File No.. •D-3480-J02. ORIGINAL GROUND SURFACE NOTE I NOTE S • NOTE 4' NO SCALE NOTES . : 1.. Excavate backslope at 2.0 to 1.0 inclination beginning 15 feet horizontally (minimum) from top of slope 2. Base of Stability fill to be 5 feet below pad grade. 3. Stability fill to be composed of properly compacted material excavated from slope. •.... • 4. Collector pipe to be 4-inch minimum diameter, perforated, thick-walled PVC or BS sloped to drain and connected to storm drain or canyon subdrain. 5. Filter material to be either Class II permeable material in accordance with State of California Standard Specifications Sections 68-1.025 or 1-inch open-graded crushed rock enclosed in filter fabric. As an alternate Miradrain drainage board, or equivalent, may be used in lieu of the filter gravel. TYPICAL STABILITY FILL STAGECOACH PARK CARLSBAD, CALIFORNIA: Figure 2 GEOCON INCORPORATED