Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
1999-5818 G
Street Address 35 35" Category Serial # Name Description Plan ck. # Year O 1045 Linda Vista Drive, Suite 108 Geotechnical 1 San Marcos, California 92069 (760) 471 -9505 • Fax (760) 471 -9074 Environmental 1 K INC. Materials 1 a 1 1 GEOTECHNICAL EVALUATION 1 SLOPE FAILURE I 1 y 1 1 For Ms. Anne Daigle & Mr. Rich Heyman 1 2825 Crystal Ridge Encinitas, California 1 1 1 1 ' November 6, 1998 1 C -1039 1 1 A California Corporation ' TABLE OF CONTENTS Intent .................................................................................................. ............................... 2 ' SCOPE OF WORK .......................................................................... ............................... 3 SITE DESCRIPTION AND BACKGROUND ............................... ..............................3 SiteDescription ............................................................................... ............................... 3 ' Background ..................................................................................... ............................... 3 SUBSURFACEEXPLORATION .................................................. ............................... 4 LABORATORYTESTING ............................................................ ............................... 4 ' Moisture - Density ............................................................................. ............................... 4 LaboratoryStandard ........................................................................ ............................... 4 ' Shear Testing ................................................................................... ............................... 4 SUMMARY OF GEOTECHNICAL CONDITIONS. . 5 Site Geology and Earth Materials ................................................... ............................... 5 ' Slide Materials (Slope Failure) ....................................................... ............................... 5 DelMar Formation .......................................................................... ............................... 5 Surfaceand Ground Water .............................................................. ............................... 5 ' Failure Area ..................................................................................... ............................... 6 DISCUSSION.................................................................................... ............................... 6 ' RECOMMENDATIONS ..::.............................................. ................. 8 Slope Reconstruction. .... . ..... ..... ........... ...8 GradingGuidelines ......................................................................... ............................... 9 ' Landscape Maintenance and Planting ............................................ ............................... 9 Drainage........................................................................................ ............................... 10 LIMITATIONS................................................................................ .............................10 1 1 1 1045 Linda Vista Drive, Suite 108 Geotechnlcal s San Marcos, California 92069 (760) 471 -9505 • Fax (760) 471 -9074 Environmental 1 K I . Materials November 6, 1998 1 Project: C1039 1 Ms. Anne Daigle & Mr. Rich Heyman 2825 Crystal Ridge 1 Encinitas, CA 92049 Subject: Geotechnical Evaluation 1 Slope Failure 2825 Crystal Ridge 1 Encinitas, California 1 In accordance with your request and authorization, GeoTek Insite, Inc. has performed preliminary geotechnical studies for the Slope Failure on the rear slope at 2825 Crystal Ridge, Encinitas, California. 1 This report presents the results of our geotechnical study to evaluate surface and subsurface conditions related to the recent slope failure. This report summarizes our 1 findings and includes recommendations for slope repair. 1 Recommendations offered will most likely be subject to modification and refinement during actual earthwork construction for the slope repair, as additional information is obtained from field observation. 1 Intent 1 It is the intent of this report to aid in the design and completion of the described project. Implementation of the advice presented in the "Recommendations" section of this report is intended to reduce risk associated with construction projects. The professional 1 opinions and geotechnical advice contained in this report are not intended to imply total performance of the project or guarantee that unusual conditions will not be discovered ' during or after construction. The scope of our investigation is limited to the area explored which is shown on the site 1 plan. The scope is based on the proposed repair work and standards normally used on similar projects in similar areas. ' A California Corporation ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 3 ' SCOPE OF WORK The following tasks were completed during our study: ♦ visual site reconnaissance; ' ♦ review of aerial photographs: 1953,1967,1973 & 1978; ♦ review of published geologic maps and available geotechnical documents pertaining ' to the site; ♦ geotechnical field evaluation consisting of a limited subsurface exploration to assess general conditions of earth 39materials within the slope area, and to obtain ' representative soil samples for laboratory testing; ♦ laboratory review and testing of the samples obtained; ♦ analysis of the data gathered; ' ♦ compilation of a preliminary geotechnical report, summarizing our findings and regarding the slope failure and recommendations for slope repair. ' SITE DESCRIPTION AND BACKGROUND ' Site Description The site is currently occupied by a residence, with landscaping and other improvements. ' The rear slope is basically a west facing graded slope constructed in conjunction with development of the subdivision. The slope appears to vary in gradient from slightly ' flatter than 1.5:1 to 2:1, and is about 30 feet high. The slope was constructed as a cut slope and is common to adjacent properties. The slope failed in February of this year. We observed the slope soon after failure. The failed area involves most of the southerly ' portion of the slope area within the subject property. This failed portion of the slope previously extended off site to the south, which has had remedial work performed. ' Background The subject site was graded in approximately 1988 -1989 as part of Crystal Ridge Estates, and identified as Parcel 2, of PM 10045. We reviewed some available previous geotechnical reports. Efforts to obtain the file from the city were not successful, as the file was temporarily unavailable. Neither the original as- graded tract information nor ' data for the site to the south have been reviewed. One of our staff members reviewed this information previously as a part of another study. ' K IRE. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 4 ' SUBSURFACE EXPLORATION Our limited subsurface evaluation consisted of the excavation, logging, and sampling of three (3) exploratory trenches, excavated with a backhoe. Our fieldwork was conducted ' on August 28, 1998. The approximate locations of the excavations are shown on Plate 1, Site Plan. The depths of the excavations varied from approximately six (6) to nine (9) ' feet below existing slope face grades. The excavations are summarized in Table 1. The purpose of these excavations was to evaluate the earth materials underlying the slope ' area, ascertain their engineering properties as they impact slope repair, and collect samples for laboratory testing. Representative bulk samples were collected from the excavations. In -situ density and moisture content information was also collected. All samples were transported to the laboratory for classification and possible testing. LABORATORY TESTING Moisture - Density The field moisture content and dry unit weight were determined for an undisturbed ' sample of the slide materials encountered in trench T -2. The dry weight was determined in pounds per cubic foot, and the field moisture content was determined as a percentage of the dry unit weight. The results of these tests are shown on the test pit logs, at the ' corresponding sample depths. ' Laboratory Standard The maximum dry density and optimum moisture content was determined for a representative soil type encountered in the trenches. The laboratory standard used was ASTM D1557. The moisture - density relationship obtained for these soils are shown below: ' Soil Type Description ' I Maximum D Density Optimum Moisture Content A Dark green silty clay 108.5 20.0 Shear Testing ' Shear testing was performed in a direct shear machine of the strain - control type. The rate of deformation is approximately 0.05 inches per minute. The samples were sheared under varying confining loads in order to determine the coulomb shear strength parameters, angle of internal friction and cohesion. The tests were performed on an undisturbed sample of near - surface soil. The shear test results indicated the angle of internal friction at 22 degrees and cohesion of 200 psf for the particular soil type. 10; K IRE. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 5 ' SUMMARY OF GEOTECHNICAL CONDITIONS ' Site Geology and Earth Materials Based on our site reconnaissance, mapping, subsurface excavations, and review of ' published geologic maps, the site is underlain by sedimentary units of the Del Mar Formation. The failed portion of the slope is comprised of recent slide deposits derived from the sedimentary formational units. The slide materials overly the sedimentary ' formational materials at depths of one (1) to in excess of fifteen (15) feet below the existing slope grades. Slide Materials (Slope Failure) The failed slope area consists of dark green to olive -gray, fractured to highly fractured ' and broken claystone and siltstone units that comprise the slide materials and overly the formational materials. The base of the slide materials is defined by a basal slide surface on which the recent slope failure occurred. The slide surface consists of a dark gray- , green to dark orange- brown, remolded clay seam that varies between 1 /4 inch up to 2 inches thick. A well - developed root/root hair mat was observed on the slide surface in Trench T -2. The slide surface dips approximately 9 to 10 degrees to the southeast (into ' slope). Del Mar Formation The Del Mar Formation underlies the slide materials and as observed consists of light olive -gray to dark green thin - bedded silty claystone that although highly fractured, is less ' fractured than the slide materials, with random - oriented shearing. Bedding dips about 8 degrees to the southeast (into slope). Both low and high angle joints and fractures were observed. The high angle joints predominate and are oriented subparallel to the slope and ' dip steeply to the north and south. Underlying the claystone is dense to very dense, massive - bedded, slightly fractured and jointed, gray, mottled red - maroon, clayey, fine ' grained sandstone. Surface and Ground Water Surface water: The site is on a graded lot and appears to have reasonably good drainage control. No ' surface water or ponding was observed at the time of our investigation. Seepage was not noted on the slope surface at the time of our subsurface exploration. Any surface water accumulation on the site should mainly be the result of incident precipitation and irrigation. There is a rather wide flat area at the top of the slope where water may collect. There was standing water in the rear yard of the house to the south in February. ' At that time, seepage from that slope was also noted. I ; ' K I9E. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 6 ' Ground water: Slight seepage was noted in the form of beading along the slide surface during our ' subsurface exploration. Significant ground water was not encountered in our excavations at the time of our study to the depths excavated. Ground water is not anticipated to impact repair work. Minor perched water conditions may occur in the future as a result ' of irrigation or increased rainfall. However, it should be noted that fluctuations in the level of groundwater can occur due to variations in rainfall, temperature, and other factors not evident at the time measurements were made and reported herein. Failure Area ' The failure area on site is about 50 feet wide at the maximum, and at it's highest point, extends from approximately five feet below the top of slope near the southern property line to just above the toe of slope (about 25 feet vertically), where the slide "toes out." ' The majority of the slide was on the site to the south. The depth of the slide is anticipated to be at least fifteen (15) feet deep vertically. The slide may be about 30 feet thick from the face of the slope horizontally in the center portion. Refer to Plate 1, Site Plan and ' Plate 2, Schematic Cross Section. The failure buckled portions of the existing wood fence that defines the southern property line along the slope. The failed portion is ' estimated to be approximately 30 to 35 percent on the slope at 2825 Crystal Ridge with the balance previously on the adjacent residence's slope prior to their repair work. ' DISCUSSION In our opinion, repair of the subject slope failure should be performed to minimize the potential for problems to occur as the result of additional or further failure. We also feel that due to the relatively weak and potentially unstable nature of the existing materials on the unfailed portion of the slope, that it would be prudent to include the whole slope area ' in the repair work. The most reasonable method with which to repair the slope area should be determined based on several considerations with a level of assurance against future failure and cost being primary factors. Ideally, it would be desired to develop factors of safety and slope configurations ' conforming to current standards or code. This may not be a practical solution, as it would necessitate extensive regrading /reconstruction of adjacent property slopes that were a part of the originally graded subdivision, possibly extensive construction of retaining wall ' devices, and special construction considerations. Even with this type of approach, there would still be some potential for erosion and future failures to occur. ' Unfortunately, weathering is a natural process that will, over the course of time, decrease the stability of all slopes. As such, any slope may be subject to future failure. Typically, ' the length of time that can be expected before any further problems would occur is ' K IRE. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 7 influenced by a variety of factors and can be accelerated by poor maintenance procedures ' (overwatering, lack of rodent control, etc.). Therefore, future slope maintenance should be viewed as critical to performance. ' Assuming that complete conformance with current codes is neither desired nor warranted, then, several options could be undertaken to improve conditions. We offer some ' guidelines for the time that might be expected before problems are likely to occur on a repaired area. These time lines are relative, and, offered only to help assess the relative ' benefits of the options presented, they are not in any way a guarantee of performance. The following levels of repair have been considered for the slope area: 1 1) Obviously, the least expensive option would be to do nothing. Inaction, however, would likely lead to damage that might otherwise be prevented and increase ' ultimate costs. Annual on going problems should be anticipated. The extent would depend largely on the weather conditions. The failure will likely increase in size over time. 1 2) Continue annual protective procedures. Perhaps cost effective in the short ' term but costs would be cumulative. In addition, it is likely that the residence may experience various problems (e.g. flooding) particularly during wet years. Annual on going problems should be anticipated. The extent would depend on the level of effort ' expended. The failure will likely increase in size over time. 3) Reconstruct the entire slope (failed and unaffected portions) using native ' materials. This is the minimal effort we feel is prudent to consider. It is the least costly of any possible repair but provides little reassurance of long term stability. A three (3) to five (5) year reasonably trouble free period is likely, shallow slumps are likely within five ' (5) to ten (10) years. ' 4) Reconstruct the entire slope using select import materials. This may offer a significant improvement in the area repaired but provides little reassurance of long term stability for the slope. A three (3) to five (5) year reasonably trouble free period is likely, ' shallow slumps are likely within seven (7) to ten (10) years. ' 5) Reconstruct the entire slope using native materials reinforced with geotextiles. This should provide a significant increase in the stability of the areas repaired. We are not aware of any case where this type of repair has experience failure ' when properly constructed. A 10 to 15 year reasonably trouble free period is likely, indications are that long term, 20 to 30 years, satisfactory performance may be achieved. K ITT. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 8 ' 6) Reconstruct the slope using select import materials reinforced with geotextiles. This should provide an even greater increase in the stability of the areas repaired than item 4 but may be much more costly. A 10 to 20 year reasonably trouble ' free period is likely, indications are that long term, 20 to 40 years, satisfactory performance may be achieved. ' 7) Reconstruct the slope with native or import materials using retaining walls to decrease slope gradients to 2:1 or flatter. Reinforcing with geotextiles could be incorporated into the construction. A 15 to 25 year reasonably trouble free period is ' likely, indications are that long term, 20 to 40 years, satisfactory performance may be achieved. ' Items for repair alternatives would need to be discussed with the City. It is likely the City would not accept Items 1 through 4 due to concerns regarding the limited life span. Items ' 5 through 7 would probably be acceptable methods of repair. Our experience with similar projects indicates that Item 5 often proves to have the highest level of cost benefit ratio. Slope reconstruction is realistically the minimal effort that can be taken and the costs for reinforcing are generally worthwhile. ' RECOMMENDATIONS Below are recommendations that could be used to reconstruct the failures on the slope. ' The procedures for slope reconstruction would be essentially the same for Items 3 through 7 above. Costs for any of the above could, therefore, be obtained by modifying the extent, adding walls, using import, etc. to the guidelines below. ' Slope Reconstruction ' 1) Excavate a keyway along the toe of the existing slope. All keyways should be observed by our representatives. Approximate widths and depths are as ' follows: Key width 10 feet, base of key 2 feet below toe of slope. ' The base of each key should slant slightly back into the slope. 2) Construct a backdrain at the rear of the key so that the drain is at the ' interface of the bedrock and the new fill. Note that some compacted fill may need to be placed in the key prior to installation of the subdrain to achieve flow and outletting. Subdrain system should be as follows: 4 inch diameter perforated pipe (Schedule 40 PVC or equivalent) embedded in a ' minimum of two (2) cubic feet per lineal feet of 3/8" to 1" clean gravel wrapped in I ; ' K IRE. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 9 suitable filter fabric with at least two (2) outlet pipes provided at approximately 25 feet (on center) intervals. 3) Place and compact fill material in 6 -inch lifts, with geotextile reinforcing grid (MIRAFI Miragrid 2T+ or equivalent) placed in accordance with manufacturers specifications. While the specific design will depend on the materials selected, a vertical ' spacing of 24 inches can be assumed for estimating purposes. The grid should extend from approximately 24 inches behind the interface of the existing slide materials or bedrock and the new fill to within approximately 6 to 12 inches of the slope face. 4) Vertical and horizontal benches into competent material should be ' maintained as fill is being placed. The intent is to construct a stepped configuration as indicated on Plate 2. ' 5) Construct a second backdrain at approximately half the vertical height of the slope and provide outlets as above for the bottom key subdrain. ' Grading Guidelines Grading should be performed in accordance with the requirements of the City of t Encinitas; Chapters 18 & 32 of the Uniform Building Code and the Guidelines presented in Appendix A. ' Landscape Maintenance and Planting Water has been shown to weaken the inherent strength of soil, and slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from ' graded slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Overwatering should be avoided. ' Care should be taken when adding soil amendments to avoid excessive watering. Leaching as a method of soil preparation prior to planting is not recommended. Graded slopes constructed within and utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Plants selected for landscaping should be lightweight, deep - rooted types which require little water and are capable of surviving the prevailing climate. Compaction to the face of fill slopes would ' tend to minimize short-term erosion until vegetation is established. ' An abatement program to control ground - burrowing rodents should be implemented and maintained. This is critical as burrowing rodents can decreased the long -term performance of slopes. K INF. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 10 ' Drainage The need to maintain proper surface drainage and subsurface systems can not be overly emphasized. Positive site drainage should be maintained at all times. Drainage should ' not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond or seep into the ground. Pad drainage should be directed toward approved area(s). ' Positive drainage should not be blocked by homeowner improvements. Homeowners should be aware of potential problems that could develop when drainage is altered through construction of retaining walls, pools, spas, flatwork or other improvements. ' It is the homeowners's responsibility to maintain and clean drainage devices on or contiguous to their lot. In order to be effective, maintenance should be conducted on a regular and routine schedule and necessary corrections made prior to each rainy season. LIMITATIONS ' The materials observed on the project site and indicated in the referenced reports appear to be representative of the area; however, soil and bedrock materials vary in character ' between excavations and natural outcrops or conditions exposed during site construction. Site conditions may vary due to seasonal changes or other factors. GeoTek Insite, Inc. assumes no responsibility or liability for work, testing or recommendations performed or ' provided by others. Since our recommendations are based our visual observations, our conclusion and recommendations are professional opinions which are limited to the extent of the available data. Observations during construction are important to allow for any change in recommendations found to be warranted. These opinions have been derived in ' accordance with current standards of practice and no warranty is expressed or implied. Standards of practice are subject to change with time. It is important to point out that our recommendations address the area specific to the subject slope. This is not to be taken to mean that other areas of the slope common to ' adjacent properties are free from the potential for future failure. Failures could occur at any location on the slope. If one were to occur adjacent to an area of repair then the repair might also fail. ' K I98. ' Ms. Anne Daigle & Mr. Rich Heyman November 6, 1998 Geotechnical Evaluation Project: C1039 2825 Crystal Ridge Page 11 We look forward to working with you toward the successful completion of this project. If you have any questions concerning this report or if we may be of further assistance, please do not hesitate to contact either of the undersigned. Respectfully submitted, ' GeoTek Insite, Inc. t e P. Blake Project Geologist Qp4QFE3S,,o,,,4 �`�o�CS�'vNE ti E T'' c, LU ` ��G'. h� � C9 �T C <O p G� No. 35007 �1 4 N E "P . Exv. D'D C 1 ac 3 clv;� p imot al EG 1142 `�9t CA � � Project Engineer OP CALIF Princ pal Geologi t F of �� fi. Distribution: (4) Addressee ' Enclosure: Plate 1 -Site Plan Plate 2- Schematic Cross Section Table 1- Summary of Trench Excavations Appendix A- Grading Guidelines K Imo. 1 1 1 9 /f',r t'ki.r/N 7*�f� cis .S.(oPt' 1 1 1 1 1 1 FE 1 1 X'0 of S)JVX Wane)" 1 O 1 Site Plan Daigle - Heyman Proi: C1039 PLATE 1 K 19'8. 2825 Crystal Ridge 1 1 N W W 1 W� w a Q H�Q d 1 , N 1 ¢ a A U C7xE � 1 C�� = Z " cn O :3 Z Z w �00 \ \ O W w � u. O w W = W 1 0 xw� A �o �N W \ �ZJ_ C7 F- X wd AW W v�Ow,a \ w 1 WUOa. ; W aUJ O 1 \ CO \ \ \ z z a z F �� o 1 ` u u _ y .........\ ZU¢a "A \ .`..... " \ ......� ............. \ " O OWaO ,7 c A W W r + OGGWUW`n \ a vex �O x U � z H 1 U 0 0 0 wa p• U \ \ \ WUw paa �U HO� W q ¢ I�1 NC7wa wW >xw U O 4. 0W W Wv� O O �aAA Wa �a� UWO � O�W � w��7rxQ3 4\ aww W O aQR; t O W QC7C7QCGA E-- O .. Nw z.<=UAW w Daigle - Heyman TABLE 1 Project: C1039 ' SUMMARY OF TRENCH EXCAVATIONS ' TRENCH DEPTH DESCRIPTION REMARKS T -1 0 -4' Slide Debris Dark green, damp, soft,silty claystone, fractured to highly fractured & broken, f: N -S/84 E ' crumbly, close- spaced, open fractures; iron oxide staining; rootlets f: N -S/36 NW 4' Basal Slide Surface 1/4 " -1" thick, remolded clay seam; dark gray - green, wet, soft, silty clay; root s: N85W/38 SW hairs @4':Rs: N65E /10SE ' 4.5' Del Mar Formation Lt. Olive -Gray, moist, very stiff, clayey siltstone; fractured & sheared 4.5 -6' Tan -Gray, mottled red - maroon, moist, very dense, clayey fine grained @5': A N40W /86SE sandstone; moderately fractured and jointed; joint spacing 6 -10 "; closed; Locally a sandy clayey siltstone; appears massive - bedded ' T.D. =6' ' T -2 0 -5' Slide Debris Dark green, damp, soft, silty claystone, highly fractured, broken and sheared; @5': Jt/f: N15E/82S open fractures, crumbly 5 -6' Dark green, maroon mottling, moisture increase, highly polished shear surfaces ' 9' Basal Slide Surface Dark - Orange- brown, saturated, soft, remolded clay seam; 1 -2.5" thick; gypsum @ Rs:N40E /9 SE crystals; root hairs; well developed root mat development, slight seepage along surface (beading) ' 9 -95 Del Mar Formation Tan -Gray, mottled red - maroon, moist, very dense, clayey fine grained sandstone; moderately fractured and jointed; joint spacing 6 -10 "; closed; Locally a sandy clayey siltstone; appears massive - bedded T.D. =9.5' T -3 0 -2.7' Del Mar Formation Green, damp, stiff, silty claystone; highly fractured, crumbly @2': f /Jt: N25E /70N ' 2.7' Clay seam: Thin 1/16" thick, gray clay @27: cs: N65E /10SE 2.7 -4 Dark green claystone, less fractured; closed fractures; random - oriented, thin, @4': c: N30E /8SE discontinuous clay seams ' 4 -6.5' Gray, moist, very dense, clayey fine sandstone; oxide staining T.D. =6.5' 1 1 1 1 1 1 1 APPENDIX A cxnmrvc GUID ELINES ' STANDARD GRADING GUIDELINES FOR MINOR EARTH WORK ' Site grading should be performed to at least the minimum requirements of the governing agencies, the Uniform Building Code and the guidelines presented below. ' SITE CLEARING Trees, dense vegetation, and other deleterious materials should be removed from the site. ' Non organic debris or concrete may be placed in deeper fill areas under direction of the Soils Engineer. ' Prudent efforts should be made by the contractor to remove all organic or other deleterious material from the fill. This is especially important when grading is occurring ' near the natural grade. All operators should be aware of these efforts. Even the most diligent efforts may result in the incorporation of some materials. Laborers may be required as root pickers. SUBDRAINAGE ' Subdrains are not anticipated in conjunction with the proposed grading. Should conditions be encountered warranting subdrain placement, specific recommendations will be offered. TREATMENT OF EXISTING GROUND ' 1. All heavy vegetation, rubbish and other deleterious materials should be disposed of off site. ' 2. All loose and compressible materials (including weathered rock, deposits of alluvium and colluvium, poorly compacted or weathered fill, etc.) should be removed unless t otherwise indicated in the text of this report. Deeper removals than indicated in the text of the report may be necessary due to saturation during winter months, as the result of changes over time or due to variations in the subsurface. ' 3. Subsequent to removals, the ground surface should be processed to a depth of six inches, moistened to near optimum moisture conditions and compacted to fill standards. ' 4. Exploratory test excavations (backhoe or dozer trenches) still remaining after completion of basic removals should be excavated and filled with compacted fill if they can be located. 1 1 FILL PLACEMENT ' It should be realized that proper fill compaction is largely procedural and is the responsibility of the grading contractor. Testing and observation by the Soil Engineer, ' while helpful to evaluate the efforts of the contractor, should not be considered as a substitute for proper and consistent procedures. Compaction testing is specific to the test location; variable test results could be obtained in other locations. Technicians typically ' do not see all that occurs during construction. Deviation from the procedures found to produce adequate test results might result in inadequate compactive efforts. The need for properly maintained equipment and trained personnel operating it, cannot be over ' emphasized. ' I) On site soil and bedrock may typically be used for compacted fill; however, some special processing, placement or handling may be required (see report). 2) Material used in the compacting process should be evenly spread, moisture ' conditioned, processed, and compacted in thin lifts not to exceed six (6) inches in thickness to obtain a uniformly dense layer. The fill should be placed and compacted ' in nearly horizontal layers, unless otherwise found acceptable by the Soils Engineer. 3) If the moisture content or relative density varies from that acceptable to the Soils Engineer, the Contractor should rework the fill until it is in accordance with the ' following: a) Moisture content of the fill should typically be at or above optimum moisture. ' Moisture should be evenly distributed without wet and dry pockets. Pre - watering of cut or removal areas should be considered in addition to watering during fill placement, particularly in clay or dry surficial soils. b) Each six -inch layer should be compacted to at least 90 percent of the maximum density in compliance with the testing method specified by the controlling ' governmental agency. In this case, the testing method is ASTM Test Designation D- 1557 -91. ' 4) Side -hill fills should have an equipment -width key at their toe excavated through all surficial soil and into competent material and tilted back into the hill. As the fill is elevated, it should be benched through surficial soil and slopewash and into competent bedrock or other material deemed suitable by the Soils Engineer. 5) Rock fragments less than eight inches in diameter may be utilized in the fill, provided: ' a) They are not placed in concentrated pockets; b) There is a sufficient percentage of fine- grained material to surround the rocks; ' c) The distribution of the rocks is observed by and acceptable to the Soils Engineer. 6) Rocks greater than eight inches in diameter should be taken off site, or placed in ' accordance with the recommendations of the Soils Engineer in areas designated as suitable for rock disposal. 1 1 7) In clay soil large chunks or blocks are common; if in excess of eight (8) inches ' minimum dimension then they are considered as oversized. Sheepsfoot compactors or other suitable methods should be used to break the up blocks. ' 8) The Contractor should be required to obtain a minimum relative compaction of 90 percent out to the finished slope face of fill slopes. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct ' compaction of the slope face with suitable equipment. Given the low height of slopes on this project overbuilding the slope and cutting back to the compacted core is recommended. Other methods should be discussed with and accepted by this firm ' prior to implementing. 9) Fill over cut slopes should be constructed in the following manner: ' a) All surficial soils and weathered rock materials should be removed at the cut -fill interface. This will generally result in the cut -fill catch point or daylight line ' being at least several feet lower than the elevation indicated on the plans. b) A key at least one (1) equipment width wide and wide enough to accommodate the ' method of compaction used should be excavated into competent materials and observed by the soils engineer or his representative. The key should be tilted at least 1 foot into slope. ' c) The cut portion of the slope should be roughed out leaving the slope about three (3) feet "fat ", to evaluate if stabilization of the cut section is necessary. If the ' contractor decides to place the fill prior to cut excavation, then he should be responsible for any additional earthwork created by the fill placement and due to the need to stabilize the cut portion of the slope. ' 10)Transition lots (cut and fill) and lots above stabilization fills should be capped with a minimum three foot thick compacted fill blanket. Deeper overexcavation may be ' recommended in some cases. 11) Cut pads should be observed by the Engineering Geologist to evaluate the need for overexcavation and replacement with fill. This may be necessary to reduce water ' infiltration into highly fractured bedrock or other permeable zones, and/or due to differing expansive potential of materials beneath a structure. The overexcavation should be at least three feet. Deeper overexcavation may be recommended in some cases. 12)In cut areas exploratory test excavations (backhoe or dozer trenches) remaining after ' completion of cut excavation and removal of all surficial soils and weathered rock materials should be excavated and filled with compacted fill if they can be located. Treatment of borings can be determined during construction. GRADING OBSER VA TION AND TESTING ' 1) Observation of the fill placement should be provided by the Soils Engineer during the progress of grading. 2) In general, density tests would be made at intervals not exceeding two feet of fill ' height or every 1,000 cubic yards of fill placed. These criteria will vary depending on soil conditions and the size of the fill. ' a) In any event, an adequate number of field density tests should be made to evaluate if the compactive efforts used by the contractor are such that the required compaction and moisture content is generally being obtained. b) As proper fill compaction is largely procedural, adequate test results should not be considered as a substitute for proper procedures. This testing is, by its nature, ' specific to the test location. Variable test results could be obtained in other locations. ' 3) Density tests may be made on the surface material to receive fill, as required by the Soils Engineer. 4) Cleanouts, processed ground to receive fill, key excavations, subdrains and rock ' disposal should be observed by the Soils Engineer prior to placing any fill. It will be the Contractor's responsibility to notify the Soils Engineer when such areas are ready ' for observation. 5) An Engineering Geologist should observe subdrain construction. ' 6) An Engineering Geologist should observe benching prior to and during placement of fill. ' JOB SAFETY General: ' Job safety is of primary concern. The following outlines safety considerations for use by all employees on multi- employer construction sites. On ground personnel are at highest risk of injury and possible fatality on grading construction projects. The company ' recognizes that construction activities will vary on each site and that job site safety is the contractor's responsibility. However, it is imperative that all personnel be safety ' conscious to avoid accidents and potential injury. In an effort to minimize risks associated with geotechnical testing and observation, the ' following precautions are to be implemented for the safety of our field personnel on grading and construction projects. 1) Safety Meetings: Our field personnel are directed to attend the contractor's regularly scheduled safety meetings. ' 2) Safety Vests: Safety vests are provided for and are to be worn by our personnel where warranted. ' 3) Safety Flags: Two safety flags are provided to our field technician; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits. In the event that our personnel do not follow the above, we request that the contractor ' contact our office. Test Pits Location, Orientation and Clearance: ' The technician is responsible for selecting test pit locations. The primary concern is the technician's safety. However, it is necessary to take sufficient tests at various locations to ' obtain a representative sampling of the fill. As such, efforts will be made to coordinate locations with the grading contractors' authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.), and to select locations following or behind the ' established traffic pattern, preferable outside of current traffic. The contractors authorized representative should direct excavation of the pit and safety during the test period. Again, safety is the paramount concern. Test its should be excavated so that the spoil pile is laced away from oncoming traffic. P P P P Y g ' The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that the fill be maintained in a driveable condition. Alternatively, the contractor may opt to park a piece of equipment in front of the test pits, particularly in ' small fill areas or those with limited access. When taking slope tests, the technician should park their vehicle directly above or below the test location on the slope. The contractor's representative should effectively keep all equipment at a safe operation distance (e.g. 50 feet) away from the slope during testing. The technician is directed to withdraw from the active portion of the fill as soon as ' possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location. ' In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is directed to inform both the developer's and contractor's representatives in writing. If the condition is not rectified, the technician is required, by company policy, to immediately withdraw and notify their supervisor. The grading contractor representative will then be contacted in an ' effort to effect a solution. No further testing will be performed until the situation is rectified. Any fill placed in the interim can be considered unacceptable and subject to ' reprocessing, recompaction or removal. In the event that the soil technician does not comply with the above or other established ' safety guidelines, or if the contractor feels the technician, in any way, acts in an unsafe manner, we request that the contractor bring this to the technicians attention and if not rectified, notify the project manager or our office. ' Effective communication and coordination between the contractors' representative and ' the field technician(s) is strongly encouraged in order to implement the above safety program and safety in general. The safety procedures outlined above should be discussed at the contractor's safety meetings. This will serve to inform and remind the equipment operators of these safety procedures particularly the zone of non - encroachment. ' Trench Safety: It is the contractor's responsibility to provide safe access into trenches where compaction ' testing is needed. Our personnel are directed not to enter any excavation which: 1) is 5 feet or deeper unless shored or laid back, ' 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench, or ' 3) displays any other evidence of any unsafe conditions regardless of depth. ' All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid back. Trench access should be provided in accordance with OSHA standards. Our personnel are directed not to enter any trench by being lowered or "riding ' down" on the equipment. If the contractor fails to provide safe access to trenches for compaction testing, our ' company policy requires that the soil technician withdraw and notify their supervisor. The contractors' representative will then be contacted in an effort to effect a solution. All ' backfill not tested due to safety concerns or other reasons could be subject to reprocessing and/or removal. 1 0 1045 Linda Vista Drive, Suite 108 Ge oteC h n i ca l . San Marcos, California 92069 (760) 471 -9505 Fax (760) 471 -9074 Environmenta 'n NSITE K INC. Materials 1 �¢ 1 Report of Earthwork Construction ' Slope Restoration Encinitas, California t For Mr. Rich Heyman and Ms. Anne Daigle 1 Project: C1039 ' February 2, 1999 1 t A California Corporation 1 1045 Linda Vista Drive, Suite 108 eote C h n I ca 1 San Marcos, California 92069 (760) 471 -9505 Fax (760) 471 -9074 Environmenta �- NSITE 1 K Materials 1 - i February 2, 1999 1 Project: C1039 Mr. Rich Heyman and Ms. Anne Daigle 2825 Crystal Ridge 1 Encinitas, California 92024 1 Subject: Report of Earthwork Construction Slope Restoration 2825 Crystal Ridge 1 Encinitas, California GeoTek Insite, Inc. is pleased to present the results of our testing and observation 1 during earthwork construction associated with the subject site slope restoration in Encinitas, California. 1 This report summarizes results of our testing during site grading, a brief summary of overall site conditions observed, and recommendations for post repair maintenance. 1 GENERAL SITE GEOLOGY 1 Earth materials on the site consist of fill soils and sedimenta ry bedrock units. 1 The fill soils placed and compacted for the slope repair were derived from on site materials and consist of silty and sandy clays, clayey and sandy silts and clayey fine 1 sands. Bedrock consists of weathered Del Mar Formation. These sedimentary materials are generally highly fractured and consist of thin - bedded silty claystones with some minor clayey sand and fossiliferous beds. 1 1 ' A California Corporation ' Heyman and Daigle February 2 1999 Y g rY Slope Restoration Project: C1039 ' Report of Earthwork Construction PAGE 2 ' SITE GRADING AND TESTING ' Summary of Slope Reconstruction The rear slope within the property was reconstructed in accordance with our recommendations and restored to its approximate pre - failure configuration. A representative from our office provided part-time observation and field density testing ' services during earthwork operations. Geologic conditions, keyway excavations, removals and general grading procedures were observed by a geologist from our office on a periodic basis during the earthwork. The following is a general summary. ' 1. Prior to grading, the slope was brushed and trees and irrigation lines removed. ' 2. A key was excavated at the toe of slope a minimum of two (2) feet below the toe grade into competent bedrock materials, approximately ten (10) to twelve (12) feet ' wide. 3. Approximately two (2) to three (3) feet of compacted fill was placed in the keyway ' to achieve flowline and outlet gradient for the lowermost subdrain system. 4. A subdrain system was installed above the rear of the key and at approximately the ' mid - height of the slope, at the bedrock/fill interface. The backdrains consisted of 4 inch diameter perforated pipe (Schedule 40 PVC or equivalent) embedded in a ' minimum of two (2) cubic feet per lineal feet of 3/8" to 1" clean gravel wrapped in suitable filter fabric with solid pipe outlets. ' 5. The outer eight feet to fifteen feet of the slope was reconstructed with reinforced geotextiles and compacted fill derived from onsite materials. The existing slide materials associated with the recent slope failure were removed and recompacted ' during benching and filling. Reinforced geotextiles (Miragrid 5T and 5XT) were placed at approximately 24 -inch vertical intervals within the compacted fill. Some additional geogrid was placed at approximately 12 -inch vertical intervals near the ' south property line, until the fill height was above the former limits of the slide. ' 6. Fill consisted of onsite soils. Soils were placed in thin lifts, approximately six inches in thickness, brought to near optimum moisture content and compacted to a minimum relative compaction of 90% of the laboratory standard. K Ili. ' Heyman and Daigle February 2, 1999 Slope Restoration Project: C1039 ' Report of Earthwork Construction PAGE 3 Field Testing 1. Field density tests were performed using a sand cone (ASTM D -1556) or a nuclear gauge (ASTM D- 2922). Approximate locations of tests are plotted on the enclosed Plate 1 — Test Location Map. Test results are presented in Table 1 — Field Density Test Results. 2. Field density tests were taken at periodic intervals and random locations to check ' the compaction efforts by the contractor. Testing procedures are, by their nature, specific to the location of the tests taken; variable results could be obtained in other ' locations. Based on the grading operations observed, the test results presented herein are considered representative of the overall level of compactive efforts used during grading. ' 3. Visual classification of the soils in the field, compared to soil descriptions from laboratory testing was the basis for determining the maximum dry density value ' and optimum moisture content applied to each density test. ' Moisture - Density Relations The laboratory maximum dry density and optimum moisture content for representative soil types were determined in general accordance with test method ASTM D -1557. Test ' results are presented in the following table. ' Maximum Opt. Soil type Description Density Moisture C ' A Dark green, silty CLAY 108.5 20.0 B Gray, mottled gm. & red, sandy, 117.0 14.0 CLAY -SILT ' C Tan - green, sandy CLAY 110.5 19.0 D Lt. Yellow -gray to green -gray, 115.3 15.0 clayey, fine SAND 1 ' K III. ' Heyman and Daigle February 2, 1999 Slope Restoration Project: C1039 ' Report of Earthwork Construction PAGE 4 ' POST GRADING CRITERIA Landscape Maintenance and Planting Water has been shown to weaken the inherent strength of soil, and slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from graded slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Overwatering should be avoided. ' Care should be taken when adding oil amendments to avoid excessive watering. . g ' Leaching as a method of soil preparation prior to planting is not recommended. The slope reconstructed within and utilizing onsite materials is considered moderately ' erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Plants selected for landscaping should be lightweight, deep - rooted types, which require little ' water and are capable of surviving the prevailing climate. An abatement program to control ground- burrowing rodents should be implemented and ' maintained. This is critical as burrowing rodents can decrease the long -term performance of slopes. Drainage The need to maintain proper surface drainage and subsurface systems can not be overly ' emphasized. Positive site drainage should be maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond or seep into the ground. Pad drainage should be ' directed toward approved area(s). REGULATORY COMPLIANCE Grading associated with the subject slope repair, under the purview of this report, has been completed under the observation of, and with selective testing by, GeoTek Insite, Inc. and is found to be in compliance with the Grading Ordinance of the City of Encinitas, California. Our findings were made, and recommendations prepared in conformance with generally accepted professional engineering practices and no further warranty is implied nor made. This report is subject to review by the controlling authorities for this project. GeoTek Insite, Inc. accepts neither responsibility nor liability for work, testing or recommendations performed or provided by others. ' K I98. ' Heyman and Daigle February 2, 1999 Slope Restoration Project: C1039 ' Report of Earthwork Construction PAGE 5 The opportunity to be of service is greatly appreciated. If you have any questions concerning this report or if we may be of further assistance, please do not hesitate to ' contact any of the undersigned. Respectfully Submitted, GeoTek Insite Inc. ' Je Blake Project Geologist ��6lNEER�NG . MfTC c Qoe aoFEss/o,�� cr V F 1U0. 142 * No. 3 007� � fxP• i W ac;RCE N� Exp. W `I A imot G 1 TF �, s 500 ��O iv14`�p��' Prince ologist' Project Engineer GA� ' Enclosures: Plate 1 — Test Location Map Table 1 — Compaction Test Results ' Distribution: (4) Addressee 1 K If8. 1�'�i /.rxiM9rf .c...ivs a� RE,+�yi� 7 � 1 I 1 1 ® 1 I ® © l 21 13 2 r a l 1 � Q Ilo 1 �r to 1 1 O O p Q 1 I ' 1 E �M/cNl� /A, SudA�it/ w� .D /�Ecr/a✓oF F.c on/ F t X/S ZXIV,C— / �iv�wfl r Compaction Test Location Map ' Daigle & Heyman K I NC. Proj: C1039 PLATE 1 Daigle Heyman COMPACTION TEST RESULTS Project: C1039 Crystal Ridge ' Test Moisture Dry Soil Maximum Test Relative Date Location Elev. Content Density Density Compaction No. ( %) (pcf) Type (pcf) Type ( %) 01/07/99 1 Southern End of Slope 116.5 19.9 106.1 B 117.0 N 90.7 2 Middle Section 117.5 19.6 108.3 B 117.0 N 92.6 3 Northern End of Slope 117.5 17.6 104.9 B 117.0 N 90.0 01/08/99 4 Middle Section 119.5 14.5 103.8 A 108.5 SC 95.7 01/11/99 5 Southern End of Slope 121.0 23.0 98.3 A 108.5 SC 90.6 6 Northern End of Slope 122.0 20.5 100.4 A 108.5 SC 92.5 ' 7 Southern End of Slope 124.0 17.6 101.6 A 108.5 SC 93.6 8 Middle Section 124.0 17.6 101.4 A 108.5 SC 93.5 01/12/99 9 North Mid Section 126.0 17.6 104.1 C 110.0 SC 94.6 10 South Mid Section 126.0 19.0 102.7 A 108.5 SC 94.7 ' 01/13/99 11 Middle Section 128.0 15.6 106.6 B 117.0 SC 91.1 12 North Slope 130.0 17.0 108.7 B 117.0 SC 92.9 13 South Slope 130.0 17.0 100.3 C 110.0 SC 91.2 01/14/99 14 North Mid Section 132.0 14.6 105.1 D 114.0 SC 92.2 ' 15 South Mid Section 130.0 16.3 103.1 D 114.0 SC 90.4 16 South Slope 132.0 25.4 93.1 A 108.5 SC 85.8 16a Retest of #16 132.0 18.0 105.2 D 114.0 SC 92.3 01/15/99 17 North Mid Section 134.0 20.5 97.8 A 108.5 SC 90.1 ' 18 South Mid Section 134.0 16.6 100.5 C 110.0 SC 91.4 19 North Mid Section 136.0 19.7 99.4 A 108.5 SC 91.6 20 South Mid Section 136.0 18.3 101.8 C 110.0 SC 92.5 01/19/99 21 North Slope 138.0 18.7 101.9 C 110.0 SC 92.6 ' 22 South Slope 138.0 24.2 92.6 C 110.0 SC 84.2 23 Retest of #22 138.0 17.3 99.0 C 110.0 SC 90.0 24 North Mid Slope 140.0 20.1 97.8 A 108.5 SC 90.1 25 South Mid Slope 140.0 18.0 101.0 C 110.0 SC 91.8 ' 01/20/99 26 Middle Slope 142.0 22.0 101.0 C 110.0 SC 91.8 01/22/99 27 Middle Slope - Slope Face 126.0 15.4 111.7 D 115.3 SC 97.0 28 Middle Section -Upper Slope 145.0 18.3 102.1 C 110.0 SC 93.0 1 1 ' Note: All Elevations Are Approximate N= Nuclear Density ' SC =Sand Cone