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HomeMy WebLinkAboutGeotechnical Mass Grading, ~ RGS Engineering Geolo~y ' ~ ' 1 ' 8800 April 17, 2006 ~93~~ a ~~~~~~~D APR 1 9 2006 BY. (909) 945-2405 Avenue, Suite ll• Rancho Cucamonga, California 91730 '(9D~.~"9~5~AOi'Fhx - Darrin Gill Ashby USA, LLC 39252 Winchester Road No. 107-393 Murrieta, Califomia 92563-3509 SUBJECT: ENGINEERING GEOLOGIC REPORT OF MASS GRADING Neighborhood Park (PA-6), Roripaugh Ranch, Temecula, Cal'rfomia Project No. 614-04 , Reference: SID Geotechnical Inc., 2006, Results of Field Density Tests, Mass Grading, Neighborhood Park (PA-6), Roripaugh Ranch Panhandle, Temecu~a, Califomia, Project No. 990057-02, March 24, 2006 ~ Leighton & Associates, 2001, Preliminary Geotechnical Investigation, Portion of Roripaugh Ranch, Tentative Tract No. ' 29661, City of Temecula, Califomia, Project No. 11990013-001, February 28, 2001. , Mr. Gill: We have prepared this report summarizing our engineering geologic ' observations and inspections during rough grading of the subject neighborhood park site associated with the Roripaugh Ranch community development. Our findings and conclusions regarding the mass grading operation from an ~ engineering geologic standpoint are presented herein. We appreciate the opportunity to be of service on this project. Should you have ' any questions, or require additional information, please do not hesitate to contact our office. ' \ ~ Geologic Evaluattion • Fault/Seismic Studies • Environmental Assessments • Percolation testing , ' ' Engineering Geoingic Report ojRough Grading Ashby USA, LLC Neighborhond Par/, Roripaugh Ranch April l7, 2006 Temecula. Califnrnia Proiect 614-04 ACCOMPANYING MAPS. ILLUSTRATIONS. AND APPENDICES ' Figure 1 - Site Location Map Figure 2 - Geotechnical Map ' INTRODUCTION Site Location and Descriation ' The neighborhood Park site is ~ocated within the greater Roripaugh Ranch community development. More specifically, the park site is located just south of ' Murrieta Hot Springs Road and easteriy of the RCWD easement. The geographical relationship of the site and vicinity is shown on our Site Location Maq Figure 1. ' Site topography prior to grading consisted of rolling hilis with associated drainage ' swales and canyons. Accordingly, cut and fiil grading was accomplished to achieve the mass rade ad elevation of 1320 t 1325 f t g p o ee . , The subject park site is situated within the greater Roripaugh Ranch development which has undergone mass grading throughout. The property immediately south of the park site is not a part of the Roripaugh Ranch ' development and supports a single family ranch home. Proiect Descriution and Gradinq Although detailed park plans are not available at this time, we assume that the 5 acre project will include mainly open grass area and a play area with landscaping and associated trees. Mass grading has established a level pad across the park site sloping uniformly ' to the south. A south facing fill slope inclined at a ratio of 2:1 has been constructed along the south perimeter of the park and 2:1 cut slopes are present along the north end of the park. The mass grading condition is depicted on our ' ~ Geotechnical Maq Figure 2. Considering the natural topography of the area prior to grading, and the ' established mass grade elevation of 1320 to 1330 feet, as much as 40 feet of fill ~ has been placed in the southeastem comer of the park site. ' ~ '' RGS Engineering Geology Page 2 1 !, Engineering Geologic Report ojRough Grading Ashby USA, LLC Neighborhood Park, Roripaugh Ranch April l7, 2006 , Temecula California Proiect 674-04 ' Enaineerinq Geolopic Services Provided During the mass grading operations, RGS provided the following services: • Observation and inspection of alluvial (Qal) removals. • Observation and inspection of keyways and benching. • Observation and approval of cut siopes where necessary. ' • Recommendations for the placement of sub-drains and observation and inspection of sub~irain placement ' . Provide recommendations for earthwork and grading from an engineering geologic standpoint where necessary. ' SUMMARY OF GRADING OPERATIONS Rouah Gradina ' Rough grading operations were performed by Ashby USA, LLC of Corona, Califomia. RGS provided engineering geologic support and inspections of mass ' grading operations under contract with SID Geotechnical, Inc. Alluvial removals ' Alluvial removais were conducted in accordance with the recommendations set ' forth in the referenced preliminary geotechnical report. Alluvial removals were inspected to ensure unsuitable material was removed and bottoms exposed competent Pauba Formation bedrock. Within the subject park site, all alluvial ' soils within the drainage swales or canyons were completely removed to expose the underlying Pauba Formation bedrock prior to placement of embankment fill. ' Ailuvial removals were deepest in natural drainage swales (Figure 2) and extended to a maximum depth of approximately 12 feet below existing ground surFace. The limits of the alluvial removals were generally coincident with the ' previously mapped (L&A, 2001) trace of alluvium and the approximate limits are delineated on Figure 2. ' Kevwavs and Benchinq Where fill was placed in areas with a natural slope of 5:1 or greater, a keyway ' was placed along the toe of slope and benching maintained as the fill placed. ' RGS Engineering Geology Page 3 3 ' , EngineeringGeologicReportofRoughGrading AshbyUSA,LLC Neighborhood Pwrk, Roripaugh Ranch April l7, 2006 Temecula. Ca[ifornia Proiect 614-04 , I' Keyways were constructed a minimum 15 feet wide and extend at least 24 inches into competent Pauba Formation bedrock as exposed along the outside edge of the keyway. The keyways were "tipped" a minimum 2 percent into the '' natural hiliside. All keyways were located along the toe of slope, or on a 1:1 projection through any unsuitable material that was present. Depths were not excessive except where necessary for the travel of scrapers and to assure a ' minimum depth along the length of the keyway. Benching was conducted to remove all unsuitable alluvium/colluvium along the ' hillsides. Benching maintained a minimum 4 feet vertical exposure of competent earth material or as approved by the project Engineering Geologist during fill placement. I' Sub-drains I, Sub-drains were placed extending south-southeasteriy through the park site and encroaching the adjacent road to the east. The sub-drain consists of a 4 to 6 inch perforated pipe with 9 cu. ft. of 3/4-inch rock per linear foot, wrapped in filter , fabric. Solid pipe was used to cross the keyway fill at the toe. The surveyed sub- drain location with elevations is shown on Figure 2. ' Site Irriqation and Surface Draina4e Natural groundwater or seepage was not encountered during grading operations ' and is not expected to impact the development. However, site irrigation and insufficient surFace drainage can create problems which were unforeseen at this time and permanent drainage facilities must be maintained at all times. ' CONCLUSIONS ' • Development of the proposed neighborhood park is considered feasible from an engineering geologic point of view. ' • Grading operations were conducted in substantial compliance with the recommendations specified within the referenced Preliminary ' Geotechnical Report (L&A, 2001). • Grading was also conducted in general accordance with the Cal'rfomia ' Building Code (CBC, 2001 edition) and the provisions of the City of Temecula. , ' RGS Engineering Geology Page 4 ' ' Engineering Geologic Report ofRough Grading Ashby (ISA, LLC Neighborhood Park, Rorrpaugh Ranch Apri! 17, 2006 Temecula California Proiect 614-04 ' • Unsuitable alluvial material was removed and re-compacted in accordance ' with the specification of the referenced preliminary geotechnical investigation and our site observations and inspections. ' • Keyways were established into competent earth material along the toe of all slopes placed on ground sloping greater than 5 horizontal to 1 vertical. ' • A sub-drain was placed within the alluvial canyon clean along the eastem portion of the site following removal of the unsuitable alluvial sediment. ,' RECOMMENDATIONS Sub-drains '~I' Sub-drain outlets must be maintained and kept clear of debris or other obstructions to water flow. This can best be accomplished by plumbing the outlet ' into a designed detention basin or other permanent storm drain facility. Slopes , Slopes should be pianted as soon as possible to aid in mitigation of erosion during periods of rainfall. Jute netting should be considered to help control , erosion until landscaping matures. All drainage should be directed away from slopes. No over-the-slope drainages. , Site Irriqation 8 Surface Drainaqe SurFace drainage should be directed away from foundations of buildings or ' appurtenant structures. All drainage should be directed toward streets or approved permanent drainage devices. Where landscaping and piarrters are proposed ' adjacent to foundations, subsurtace drains should be provided to prevent standing water or saturation of foundations by landscape irrigation water. ' No over-the-slope drainage should be permitted. All drainage and site run-off should be directed across the slopes along permanent concrete v-ditches or other approved means. ' Buildinq Setbacks ' Building setbacks should be maintained in accordance with the Califomia Building Code (CBC) and local requirements of the City of Temecula, or as approved by the Engineering Geologist and/or Geotechnical Engineer. ' ' RGS Engineering Geology Page S ~ ' , Engineering Geo[ogic Report ojRough Grading Ashby USA, LLC Neighborhood Park, Roripaugh Ranch April l7, 2006 Temecula. California Proiect 614-04 I' ' CLOSURE Our investigation was perFormed using the degree of care and skill ordinarily ' exercised, under similar circumstances, by reputable geotechnical engineers and geologists practicing in this and other localities. No other warranty, expressed or ' implied, is made as to the conclusions and professionat advice included in this report. ' The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or the works of man on this or adjacent properties. In , addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside ' our control. . 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' RGS ~~~o~ .~.. _,~ . ~,~ ' y031a~'10 ~ 4.] OI y la // C PIPE 1`' ~ -- 8" PERFO D IPE °~ / I F " _~` ! ~ ry~~~ l ~ ~T ~ d ~ ~ F~'- J q ~ ~ / ~ _..~, M1 ~ C> ,~gd.o'h~ Z ~ ~~ ..;.. ~~`'~'~~- ry ~~.~ I ~~ n `'~' ~ GEOLOGIC MAP Neighborhood Park Site (PA~) Roripaugh Ranch Temecula, California A ril, 2006 Pro'ect 1 Scale 1" = 40' Fic ~