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HomeMy WebLinkAboutPE 2.87.19; La Costa Vale Unit 3 Lot 379; Soils Report; 1986-09-03E#IWEERIH& /Q-J. g 7. /p D/h-d $Q-fd GZOTECBNICAL IXVXSTiGATI3N FOR PRG?3SXD SINGLE FAMILY RESIDZNCZ, LOT 37'3 TRACT 72-70, LA COSTA VALE S6BDIViSION UNIT #j, LA COSTA, CALIFORNIA PREPARED FOR: Joe aear 1387 Basswood Carlsbad, California 92008 PREPARED BY: KETCHUM ENGINEERING, INC. 7818 Quebrada Circle Carlsbad, California 92008 TABLE OF CONTENTS Page Number Introduction and Project Description Purpose and Scope of Project Field Investigation Laboratory Testing Findings Site Description Subsurface Soil Conditions Groundwater Seismic Survey and Rippability Characteristics Rippability Charts Rippability Characteristics Seismic Traverse - Summary of Results Seismic Traverse Limitations Conclusions Recommendations Site Preparation Selective Grading for Structures Cut and Fill Slopes Foundations and Concrete Slabs-On-Grade Pavement Drainage Earth Retaining Structures Limitations Plate 1 Vicinity Map Plate 2 Site Plan 2 2 4 4 6 6 6 6 7 a a 10 11 12 14 14 16 17 18 19 20 20 22 Plate 3 Plates 4 - 10 Plate 11 Plates 12 - 16 Plate 17 Appendix A Unified Soil Classification Trench Logs Maximum Density & Optimum Moisture Content/Direct Shear Test Results/ Expansion Test Results Seismic Traverses Recommendations for Filling on Sloping Ground Recommended Grading Specifications September 3, 1986 Joe Bear 1387 Basswood Carlsbad, California 92008 (619) 944-1036 CALIF.. KE S8691 Report No. 1 Subject: Geotechnical Investigation for a Proposed Single Family Residence, Lot 379, Tract 72-70, La Costa Vale Subdivision, Unit #3, La Costa, California. Gentlemen: We are pleased to present the results of our geotechnical invest- igations for the subject project. This study was performed in accordance with your request and our proposal dated August 11, 1986. The results of our field investigation and laboratory tests, as well as our conclusions and recommendations, are presented in the accompanying report. We appreciate this opportunity to be of professional service. If you have any questions, y ou are welcome to contact this office at your convenience. Respectfully submitted, KETCHUM ENGINEERING, INC. E. N. Ketchum, R.C.E. 26267 President ENK/ct (I) Submitted (5) RoY Blackford KE SB691 Page 2 CEOTECHNICAL INVESTIGATION FOR PROPOSED SINGLE FAMILY RESIDENCE, LOT 379 TRACT 72-70, LA COSTA VALE SUBDIVISION, UNIT #3 LA COSTA, CALIFORNIA INTRODUCTION This report presents the results of our geotechnical investi- gation for the subject site. The vicinity map for this project is presented on Plate Number 1. Plate Number 2 shows the site configuration and the locations of our subsurface explorations. To assist in the preparation of this report, we were provided with a county assessors map and preliminary topographic map. PROJECT DESCRIPTION This project is located in the La Costa area in the City of Carlsbad, County of San Diego, California. The legal descrip- tion of the site is Lot 379, Tract 72-70, La Costa ValeSubdivi- sion, Unit #3, La Costa, California. The site is presently undeveloped in its natural state with a moderate covering of grasses. Development of this site is proposed to consist of constructing a wood frame, single family residence with a proposed pool and possibly a tennis court. The actual design of the home and the site plan have not been developed. PURPOSE AND SCOPE OF PROJECT The purpose of this investigation is to develop information regarding the on-site soil conditions to determine their suit- KETCHUM ENGINEERING INC. KE S8691 ability to receive the proposed development. The scope of this study includes the following: a) b) cl d) e) f) g) h) Page 3 Explore the subsurface conditions to the depths influ- enced by the proposed construction. Evaluate, by laboratory tests, the pertinent engineer- ing properties of the various strata which will influ- ence the development, including their bearing capacities, expansive characteristics and settlement potential. Define the general geology at the site including pos- sible geologic hazards which could have an effect on the site development. Develop soil engineering criteria for site grading and provide design information regarding the stability of cut and fill slopes. Complete a seismic survey to determine the rippability characteristics of the dense on-site materials. Determine potential construction difficulties and pro- vide recommendations concerning these problems. Recommend an appropriate foundation system for the type of structures anticipated and develop soil engineering design criteria for the recommended foundation design. Prepare a report that presents our findings, conclusions and recommendations. KETCHUM ENGINEERING INC. KE S8691 Page 4 FIELD INVESTIGATION Our field investigation was conducted on August 20, 1986, and consisted of visual observations of the existing surface condi- tions and completion of seven subsurface excavations. These excavations were made by means of a backhoe under the observa- tion of our engineering personnel. All soils encountered were visually classified in accordance with Unified Soil Classifica- tion System that is presented on Plate No. 3. The representa- tive soil samples obtained were transported to the laboratory for testing. Please refer to Plates Numbers 4 through 10 for the field logs. The seismic survey for this study was performed on August 14, 1986 and included the performance of five shallow refraction engineering seismograph traverses using a Bison Instrument Signal Enhancement Seismograph Model 1570B. The locations of the tra- verses are shown on the attached Plate Number 2. Results of the seismic traverses are included herein on Plates 12 through 16. A summary of these traverses is presented on Page 18. LABORATORY TESTING Laboratory testing on selected soil samples were completed in conformance with the general practices and procedures as recom- mended by the American Society for Testing and Materials (A.s.T.M.). These tests are briefly outlined below: a. Soil Sample Classification: By visual examination, the sampled soil classifications made in the field were further evaluated in accordance with the Unified Soil Classification System. The final classifications are presented on the exploratory logs. KETCHUM ENGINEERING INC. KE S8691 Page 5 b. Field Moisture Content and Dry Soil Density: The moisture content in percent of the soils dry weight and the dry unit weight in pounds per cubic foot were determined for selected soil samples. Please refer to the exploration logs for the results of these tests. c. Maximum Dry Density and Optimum Moisture Content: In accordance with the A.S.T.M. Standard Test D-1557-70, Method A, the maximum dry density, (pounds per cubic foot), and the optimum moisture content, (percent of the dry density), were established on typical samples. Plate Number 11 presents the results of these tests. d. Direct Shear Test: Direct shear tests were performed to determine the failure envelope based on yield shear strength. The shear box was designed to accommodate a sample having diameters of 2.375 inches or 2.50 inches and a height of 1.0 inch. Samples were tested at dif- ferent vertical loads and at saturated moisture content. The shear stress was applied at a constant rate of strain of approximately 0.05 inches per minute. The results of these tests are presented on attached Plate Number 11. e. Expansion Tests: The expansive potential of clayey soils was determined in accordance with one of the following test procedures and the results of these tests appear on Plate Number 11. 1) Allow the trimmed, undisturbed or remolded sample to air dry to a constant moisture content, at a temperature of 100 degrees F. Place the dried sample in the consolidometer and allow to compress KETCHUM ENGINEERING INC. KE 58691 Page 6 under a load of 150 psf. Allow moisture to contact the sample and measure its expansion from an air dried to saturated condition. FINDINGS SITE DESCRIPTION The site is a flag shaped lot that gently slopes towards the west. Residential properties are present to the east, north, and west with vacant land present at the southern boundary. A rock cut slope is present paralled to the western property line that is about 12 to 15 feet in height. This slope was apparent- ly not blasted in order to complete the cut as evidenced from the lack of blasting holes. No man-made structures were appar- ent on-site. Vegetation consisted of the native grasses and a fen shrubs. SUBSURFACE SOIL CONDITIONS The site is capped with a reddish-brown, sandy silty clay that contains chunks or metavolcanic rocks. These soils are highly expansive and are defined as topsoil and weathered metavolcanics. The thickness of these dry, loose to medium stiff soils ranged from one point five (1.5) to three (3) feet. Some very minor amounts of end dumped soil, rock, and concrete chunks were en- countered on-site. Underlying these upper materials are meta- volcanic rocks that are somewhat fractured and very dense in consistency. GROUNDWATER Based on our investigation, we do not believe that a shallow groundwater table exists at the site. No water table was en- KETCHUM ENGINEERING INC. KE S8691 Page 7 countered in any of the test trenches. We do not, therefore, anticipate any major groundwater related problems, either during or after construction. However, it should be recognized that minor groundwater seepage problems may occur after development of a site even where none were present before development. These are usually minor phenomena and are often the result of an alteration of the permeability characteristics of the soil, an alteration in drainage patterns and an increase in irrigation water. Based on the permeability characteristics of the soil and the 'anticipated usage of the development, it is our opinion that minor seepage problems may occur at random locations. It is further our opinion that these problems can be most effect- ively corrected on an individual basis if and when they develop. SEISMIC SURVEY AND RIPPABILITY CHARACTERISTICS The intent of the seismic refraction survey performed at the site was specifically to facilitate the project planning by determining the variations in seismic velocity of the under- lying materials and to determine a reasonable approximation of the depth from the surface to the boundaries between rippable, marginally rippable, and non-rippable bedrock. Five refraction seismograph traverses were extended using a Bison Instrument Signal Enhancement Seismograph Model 1570B. The traverses were located in areas where buildings or road cuts are anticipated. The approximate location of each seismo- graph traverse is shown on the enclosed Geotechnical Map, Plate Number 2. The seismograph's depth of investigation is closely related to the length of the seismic traverse. For a particular length of traverse, e.g., 60 feet, using a ratio of 3:1 between length and depth, we conclude that this length of survey line will detect the boundaries between materials of varying density and velocity to a depth of approximately 20 feet. KETCHUM ENGINEERING INC. KE S8691 Page 8 RIPPABILITY CHARTS Due to the presence of rock-soil units, we are including three rippability charts which apply to the site conditions. Two of the charts have been developed by the Caterpillar Tractor Com- pany for use with the D-9 and D-8 Caterpillar Tractor with No. 9 Series D Ripper and No. 8 Series D Ripper, respectively ("Hand- book of Ripping", Caterpillar Tractor Company, Fourth Edition, April, 1972). The third chart is a modification of charts by the Caterpillar Company and an article in "Roads and Streets", September, 1967, which we feel approximately defines rippability with the D-9 using a conventional #9 Single Shank Ripper. RIPPABILITY CHARACTERISTICS Rippable Condition (0 - 4,500 Ft/Sec) This velocity range indicates rippable materials which may consist of topsoil and weathered or decomposed rocks which may possess random hardrock floaters. These materials typically will break down into slightly silty, well-graded sand. Materials within the velocity range of from 3,500 to 4,000 fps are rippable with difficulty by backhoes and other light trenching equipment. Marginally Rippable Condition (4,500 - 5,500 Ft/Sec) This range is rippable with effort by D-9 in only slightly weathered materials. This velocity range may also include numerous areas of very dense rock with the possibility of extensive areas of fractured material. Excavations may produce material that will partially break down into a gravelly, coarse sand containing a high percentage of cob- KETCHUM ENGINEERING INC. KE S8691 Page 9 ble or boulder-sized materials. Less fractured or weather- ed materials may be found in this velocity range that would require blasting to facilitate removal. Materials within this velocity range are beyond the capabil- ity of backhoes and lighter trenching equipment. Difficulty of excavation would also be realized by gradalls and other heavy trenching equipment. Nonrippable Condition (5,500 Ft/Sec and Greater) This velocity range includes nonrippable material consist- ing of primarily fractured materials at lower velocities with increasing hardness at higher velocities. In its na- tural state, it is not desirable for building pad subgrade. Blasting will most likely produce oversize material requir- ing disposal. The upper limits of rippability have been based on Rippability Chart No. 3 utilized for this report. However, as noted in the two Caterpillar charts (Nos. 1 and 2), the upper limits of ripp- ability may sometimes be increased. Chart No. 1 D9G Cat - No. 9 Series D Ripper Rippable 0 - 7,000 fps Marginally Rippable 7,000 - 8,000 fps Nonrippable 8,000 + fps Chart No. 2 D8H Cat - No. 8 Series D Ripper Rippable 0 - 5,800 fps Marginally Rippable 5,800 - 6,800 fps Nonrippable 6,800 + fps KETCHUM ENGINEERING INC. KE S8691 Page 10 Chart No. 3* D9 Cat - No. 9 Shingle Shank Ripper (Conventional) Rippable 0 - 4,500 fps Marginally Rippable 4,500 - 5,500 fps Nonrippable 5,500 + fps * This chart has been utilized for defining rippability character- istics of the subject site for this report. SEISMIC TRAVERSE - SUMMARY OF RESULTS ST-2 2,300 5,200 ST-3 2,000 16,000 ST-4 1,150 11,000 ST-5 1,800 20,000 + TRAVERSE VELOCITY NO. (FT/SEC) ST-l 1,400 7,000 TABLE I DEPTH (FT) 0 - 4' 4' + 0 - 3' 3' + 0 - 8.5' 8.5 + 0 - 4' 4' + 0 - 9.5' 9.5 + RIPPABILITY Rippable Nonrippable Rippable Marginally Rippable Rippable Nonrippable Rippable Nonrippable Rippable Nonrippable KETCHUM ENGINEERING INC. KE S8691 Page 11 Practical economical refusal in our test excavations with the backhoe used was encountered as follows: Trench No. Depth (Ft) 1 2.5 2 3 3 2 4 1.5 5 1.5 6 2 7 3 SEISMIC TRAVERSE LIMITATIONS The results of the seismic survey for this investigation reflect rippability conditions only for the areas of the traverses. However, the conditions of the various soil-rock units appear to be similar for the remainder of the site and may be assumed to possess similar characteristics. Our reporting is presently limited in that refraction seismic surveys do not allow for predicting a percentage of expectable oversize or hardrock floaters. Subsurface variations in the degree of weathered rock to fractured rock are not accurately predictable, but have been indicated where thought to possibly exist. The seismic refraction method requires that materials become increasingly dense with depth. In areas where denser, higher velocity materials are underlain by lower velocity materials, the lower velocity materials would not be indicated by our survey. KETCHUM ENGINEERING INC. KE S8691 Page 12 All of the velocities used as upper limits from Rippability Chart No. 3 are subject to fluctuation depending upon such local varia- tions in rock conditions are: a) Fractures, Faults and Planes of Weakness of Any Kind b) Weathering and Degree of Decomposition cl Brittleness and Crystalline Nature d) Grain Size Further,‘the range of rippability using Caterpillar equipment may be increased using the equipment listed in Charts 1 and 2. However, it should be noted that ripping of higher velocity ma- terials may become totally dependent on the time available and the economics of the project. Ripping of higher velocity materi- als can be achieved but it may become economically unfeasible. CONCLUSIONS Based on the findings of this study, we conclude that with respect to geotechnical aspects, the subject site is suitable for the proposed project provided the recommendations contained in this report are fully complied with. The on-site soils were determined to have a high expansive poten- tial and, therefore, will require special foundation design and site development considerations. Mitigating measures regarding this condition are presented as follows: 1. Extend all footings down through the expansive weathered metavolcanics and found them on the very dense metavol- canic rock at depths that would range from about 1.5 to 3 feet. A raised floor system could then be utilised. KETCHUM ENGINEERING INC. KE 58691 Page 13 Due to the natural slope of the site some foundations may have to be pinned to the underlying rock. Please refer to Plate Number18 for an appropriate detail. 2. The area beneath structures or slabs-on-grade could be capped with at least three (3) feet of imported, select, non-expansive fill soils. 3. If it is decided to place foundations or slabs-on-grade over the on-site expansive soils, it will be necessary to specially process this soil in terms of moisture content and compaction. Further, deepened, highly re- inforced foundations and reinforced slabs will be recom- mended. The upper topsoils fill and weathered metavolcanics are loose-dry and, therefore, not suitable to receive structural loads or fill. We, therefore, recommend that they be removed and replaced as an engineered fill. According to the seismic traverses, it appears that the metavol- canic rock that underlies the upper soil mantel is very dense and nonrippable at depths of about one point five (1.5) feet in the upper portions of the site and about four (4) to five (5) feet on the lower areas. If cuts are proposed below these depths, it will probably necessitate blasting to achieve the proposed grades. Considering the on-site conditions previously presented, we sub- mit the following suggestions: I. Any cuts proposed be made on the lower portions to maxi- mum heights of about four (4) to five (5) feet. KETCHUM ENGINEERING INC. KE S8691 Page 14 2. For level terraces on which pools, foundations, or slabs-on-grade shall be placed, we suggest that they be comprised of select imported soils. This condition allows for ease af trench excavation, utilities and landscaping. Further, this condition greatly reduces the potential for distress due to expansive soils. 3. It is suggested that the structures proposed be support- ed on foundations that are extended through the expan- sive upper soils and founded on the dense foundational rock. This recommendation is for areas where founda- tions are proposed on the naturally sloping terrain. Standard conventional spread footings may be utilised for areas that are capped with three (3) feet of select soil. 4. All areas to receive pavements should be capped with at least 12 inches of select soil. RECOMMENDATIONS SITE PREPARATION PRECONSTRUCTION CONFERENCE: We recommend that a preconstruction conference be held at the site with the developer, civil engi- neer, contractor, and geotechnical engineer in attendance. Special soil handling and the grading plans can be discussed at that time. SPECIFICATIONS: We recommend that all earthwork be done in accordance with the attached "Recommended Grading Specifications." Ketchum Engineering, Inc., should observe the grading and test compacted fills. KETCHUM ENGINEERING INC. KE S8691 Page 15 All special site preparation recommendations presented in this report will supercede those in the standard Recommended Grading Specifications. All embankments, structural fill and fill should be compacted to not less than 90 percent of the maximum laboratory density. Utility trench backfill within five (5) feet of the proposed structures and beneath asphalt pavements should be compacted to not less than 90 percent of its maximum dry density. The maximum dry density of each soil type should be determined in accordance with A.S.T.M. Test Method 1557-70. DEMOLITIONS, CLEARING AND GRUBBING: During site preparation, all debris and deleterious materials derived from demolition, clearing and grubbing operations should be legally disposed of off-site prior to grading. Any existing utilities that will not be utilized should be removed and properly capped at the proper- ty lines. The removal of trees should include the removal of their roots. The depressions resulting from the above operation should be backfilled with soil that has been compacted to at least 90 percent relative compaction. GENERAL: Beneath all areas to receive fill, structural loads, sidewalks, or pavements, we recommend that the materials, top- soils, and fill be removed to firm natural ground or metavolcanic rock and stockpiled for future use. Firm natural ground is de- fined as rock or soil that possesses an in-place density equal to or greater than 85% of its maximum dry density. The bottom of the excavation should be scarified to a depth of at least six (6) inches, watered as required, and densified to at least 90%. The stockpiled soils may then be replaced and compacted to at least 90X in six (6) to eight (8) inch lifts to desired grade. The lateral extent of the above recommendation should include the area within five (5) feet beyond the perimeter. KETCHUM ENGINEERING INC. KE S8691 Page 16 SELECTIVE GRADING FOR STRUCTURES We recommend that select, imported soils be placed below all structures or pool perimeter slabs and pools. TRANSITION AREAS: We recommend that the cut area beneath struc- tures be undercut to a minimum depth of one (I) foot below the base of the deepest footing. This recommendation is submitted in an attempt to reduce the potential distress that could arise from footings founded partially on cut and partially on fill. MOISTURE CONTENT OF FILL SOILS: All fill soils placed should have moisture contents of at least 2% over optimum moisture content. AREAS TO BE PAVED: All areas to be paved should have the sub- grade soils densified to at least 90% relative compaction to a minimum depth of 12 inches. It is suggested that the upper 12 inches of subgrade soils be comprised of granular select, non- expansive materials. IMPORT MATERIALS: Any fill material to be imported on-site should consist of granular, non-expansive soil that contains no organic or deleterious materials. It should have sufficient cohesion to hold a vertical or near vertical cut for footing excavations. It should have at least 85% of the material pass- ing the Number 4 sieve with no rocks or chunks larger than one and one-half (13) inches. The import fill should be approved by our office prior to on-site delivery. KETCHUM ENGINEERING INC. KE S8691 Page 17 CUT AND FILL SLOPES It is our opinion that cut slopes constructed from the native on-site materials will be stable with relation to deep-seated failures if constructed at or flatter than the following recom- mended slope ratios expressed in the horizontal or vertical units for the indicated heights: Cut Slopes to 15 Feet in Height 'Fill Slopes to 20 Feet in Height Using Select, Imported Soil 2:l 2:l The above maximum heights were determinedeby using a factor of safety of 1.5. It is also recommended that footings not be founded nearer than eight (8) feet measured horizontally inward from the face of the slopes. Slopes should be planted with erosion resisting plants and natural drainage should be directed away from the top of all slopes such that no water is allowed to flow over the top. TEMPORARY SLOPE STABILITY: The following table presents recom- mendations relative to temporary construction excavations. These slopes should be relatively stable against deep-seated failures but may experience localized sloughing. Slope Ratio Maximum Height of Temporary (Horizontal to Vertical) Excavation (Feet) 0.25 : 1 Vertical 12 5 It should be the contractor's responsibility to provide safe support for the excavation. No heavy equipment should be allow- ed adjacent to the top of the temporary cuts. KETCHUM ENGINEERING INC. KE S8691 FOUNDATIONS AND CONCRETE SLABS-ON-GRADE: Page 18 GENERAL: We recommend the structure proposed for this project be supported by a continuous spread footing foundation system as recommended below. The following recommendations are sub- mitted provided the soils within the upper three (3) feet from finish grade have a low expansive potential. a) All footings for one and two story structures should 'be founded a minimum of 12 and 18 inches respectively below adjacent finish grade. Footings should have a minimum width of 12 inches. b) Both exterior and interior continuous footings should be reinforced with two No. 4 bars positioned three (3) inches above the bottom of the footings and two No. .!+ bars positioned three (3) inches clear below finish floor or the top of stem walls. cl Interior slabs should be not less than three and one- half (34) inches in thickness, underlain by a four (4) inch blanket of clean sand or crushed rock, reinforced with 6"x6"-#lo/#10 welded wire mesh and completely surrounded with a continuous footing. d) Exterior slabs should be a minimum of three and one- half (3h) inches in thickness and should be reinforced with 6itx611-#1 O/#lO welded wire mesh. e) Surface drainage should be directed away from the pro- posed foundation. Planters should be constructed so that water is not allowed to seep beneath foundations or slabs. Over-irrigation of areas adjacent to founda- tions and slabs should be avoided. KETCHUM ENGINEERING INC. KE 58691 Page 19 f) Prior to placing concrete, the foundation excavations should be inspected by a representative of this office to insure that the above recommendations have been followed. FOUNDATION ON METAVOLCANIC ROCK: Please refer to Plate Number18 for a general detail for this condition. BEARING VALUE: An allowable soil bearing value of 2000 pounds per square foot for spread footing foundations may be used for design of the on-site structures. This bearing value should be verified for all soil conditions under all building pads. In our opinion this value can be increaseh by one-third for loads that include wind or seismic forces. SETTLEMENT CHARACTERISTICS: The anticipated total and/or differ- ential settlements for the proposed structure may be considered to be within tolerable limits provided the recommendations pre- sented in this report are followed. PAVEMENT The following recommendations are submitted as preliminary guide- lines for pavement construction. The subgrade soils to a depth of at least 12 inches should be densified to at least 90%. Paved areas should be protected from moisture migrating under the pave- ment from adjacent water sources such as planted or grass areas. Saturation of the subbase soils could result in pavement failures. Further, all paving materials and methods of construction should conform with good grading practices and with the minimum require- ments of the governing agency. KETCHUM ENGINEERING INC. KE S8691 Page 20 DRAINAGE We recommend that positive measures be taken to properly finish grade the pads once improvements and landscape are in place so that drainage waters are directed off the pads and away from possible foundations, floor slabs, and slope tops. No areas of ponded water should be allowed to exist. EARTH RETAINING STRUCTURES GENERAL: It is our understanding that the small retaining struc- tures that are proposed for this project will be of masonry con- struction. ULTIMATE ACTIVE PRESSURE: The ultimate soil pressure for the design of earth retaining structures with level backfills may be assumed to be equivalent to the pressure of fluid weighing 35 pounds per cubic foot for walls free to yield at the top (unrestrained walls). For walls restrained at the top, a fluid pressure of 45 p.c.f. may be used. These pressures do not con- sider any surcharge loading. If any surcharge loadings are anti- cipated, this office should be contacted for the necessary in- crease in soil pressure. All earth retaining structures should have adequate weep holes or a subdrain system to prevent the buildup of hydrostatic pressure behind the wall. ULTIMATE PASSIVE PRESSURE: The passive pressure for prevailing soil conditions may be considered to be 300 pounds per square foot per foot of depth. This pressure may be increased one- third for seismic loading. The coefficient of friction for concrete to soil may be assumed to be 0.37 for the resistance to lateral movement. When combining frictional and passive resistance, the latter should be reduced by one-third. KETCHUM ENGINEERING INC. KE 58691 Page 21 ALLOWABLE SOIL BEARING PRESSURE: The foundation for the pro- posed retaining structures should consist of spread footings founded in the firm native soils or compacted fill. Firm nat- ural ground is defined as soil having an in-situ density of at least 854: of its maximum dry density. Footings may be designed for an allowable bearing pressure of 2000 p.s.f. FACTOR OF SAFETY: The above values, with the exception of the allowable soil bearing pressure, do not include a factor of safety. Appropriate factors of safety should be incorporated into the design of all earth retaining structures to reduce the possibility of overturning and sliding. BACKFILL: All backfill soils should be compacted to at least 90% relative compaction. Expansive or clayey soils should not be used for backfill material within a distance of five (5) feet from the back of the wall. The retaining structure should not be backfilled until the materials in the wall have reached an adequate strength. KETCHUM ENGINEERING INC. KE 58691 LIMITATIONS Page 22 The recommendations presented in this report are contingent upon our review of final plans and specifications. The soil engineer should review and verify the compliance of the final grading plan with this report. It is recommended that Ketchum Engineering, Inc., be retained to provide continuous soil engineering services during the earth- work operations. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on an eval- uation of the subsurface soil conditions encountered at the sub- surface exploration locations and the assumption that the soil conditions do not deviate appreciably from those encountered. It should be recognised that the performance of the foundations may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unex- plored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the soil engineer so that he may make mod- ifications if necessary. This office should be advised of any changes in the project scope or proposed site grading so that it may be determined if the recommendations contained herein are appropriate. This should be verified in writing or modified by a written addendum. The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur with the passage of time, whether they be due to natural processes or the work of man on this or adjacent properties. In addition, changes KETCHUM ENGINEERING INC. KE St3691 Page 23 in the state-of-the-art and/or government codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control. Therefore, this report should not be relied upon after a period of two years without a review by us verifying the suitability, the con- elusions, and recommendations. In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface con- ditions may vary from those encountered at the locations where our borings, surveys, and explorations are made, and that our data, interpretations and recommendations are based solely on the information obtained by us. We will be responsible for those data, interpretations and recommendations, but shall not be res- ponsible for the interpretations by others of the information developed. Our services consist of professional consultation and observation only, and no warranty of any kind whatsoever, expressed or implied. is made or intended in connection with the work performed or to be performed by us, or by our proposal for consulting or other services, or by our furnishing of oral or written reports or findings. It is the responsibility of the owners, or their representative to ensure that the information and recommendations contained herein are brought to the attention of the engineer and arch- itect for the project and incorporated into the project’s plans and specifications. It is further their responsibility to take the necessary measures to ensure that the contractor and his subcontractors carry out such recommendations during construc- tion. Inspection services allow the testing of only a very small per- centage of the fill placed at the site. Contractural arrange- ments with the grading contractor should contain the provision KETCHUM ENGINEERING INC. KE S8691 Page 24 that he is responsible for excavating, placing and compaction of fill in accordance with the project specifications. In- spection by the geotechnical engineer during grading should not relieve the grading contractor of his primary responsibility to perform all work in accordance with the specifications. This firm does not practice nor consult in the field of safety engineering. We do not direct the contractor’s operations, and we cannot be responsible for the safety of other than our own personnel on the site; therefore, the safety of others is the responsibility of the contractor. The contractor should notify the owner if he considers any of the recommended actions presented herein to be unsafe. Even though our field investigation indicates that the existing fill placed on this site prior to our study is fairly well com- pacted, this firm makes no warranties or guarantees, either ex- pressed or implied, as to the competency or performance of this fill inasmuch as we made no on-site observations or did no com- paction testing during the fill placement or earthwork operations. KETCHUM ENGINEERING INC. SITE /’ VICINITY MAP “: ENK JOB NO. 8691 KETCHUM ENGINEERING INC.*m 7818 OIJEBRADA CIRCLE 3 C A RLSBAD (619) 944-1636 DATE: 913186 PLATE NO. 1 a TRENCH .F -y 7 Jic?o T2 /\ 0 / / ‘\ SITE PLAN BY: RS KETCHIIM FNGINFFRING INC R ’ JOB NO. 6691 QATE: S/27/86 I I-- I --.-.w. -.--..-I- . . . . WV 1--v. 7616 I~UE~RAOA CIRCLE s C A RLSBAD I (6191 944-1636 92ooac PLATE NO. 2 1 UNIFIED SOIL CLASSIFICATION MAJOR DIVISIONS GROUP SVMBU TYPICAL NAMES GRAVELS CLtAN GRAVELS =w I W;ll$,~ded Q’.veb pIwet-sand rnmtul~l. IlltIe 01 110 huaLTnANnALF (LESS 1MAN GP Pcdy laded pnvcb w puel-sand mirturrr. Iill* of OF COARSE 5% FINES1 fw Ima. r FRACTION IS 1 GRAVEL 1 GM 1 Silty piawA. pfrvtl-sand-sill mialwn. non-pl&C Iinn. 1 LARGER TWN WITH I NO. 4 SIEVE FINES GC 1 Claw wweI*. mrwel-sand-clav minurcr. d&tie liner. SANDS CLEAN SANDS SW Well graded smds. gravelly sands. little w no lines. MORE THAN HALF (LESS THAN OF COARSE 5% FINES) SP poorlv graded sands 01 prw+ undr. little or no km. CRACTION IS SAN05 SM Sill” und.,. sand-silt milltuns. nm-plsslic lim. SMALLER THAN WITH NO. 4 SIEVE FINES SC Cw undo. and-clay mialwn. plastic lines. SILTS AND CLAYS ML Inof ItiC Lilts and very fine ends. !oCk Now. silty, of &ev Im sands o( clryw wlls mlh slqhl PIJOICI~V. LIOUIO LIMIT IS c L -fpF w& ~f$y$~~Ng$~;~ wdv LESSTHAN 50% OL Owric *ctr and otwnic silty chyr d low plastic+. SILTS AND CLAYS cfdiul~limunbva UCIUIO LIMIT IS CH lm,pa,,ic clayr d high plndci~y. (4: cllyr. GREATER THIN 50% OH or@ cw 01 nu&un la high plasticity. clqpnic sills. 1 Pt 1 1 HIGHLY ORGANIC SOILS Pen and oub?t hiily orgmtc soil% J GRAIN SIZE U.S. ST@OARD SERIES SIEVE -I- CLEAFl SOUARE SIEVE OPENINGS - 200 40 m . .%A' ?M 17. [ SAND GRAVEL SILTS AND CLAYS I COBBLES 6oLJlDERs FINE MEDIUM COARSE FINE CMRSE RELATIVE DENSITY Cl ISISTENCY iANOS.GRAU ‘ELS AN) I KIN-PI *=II .NJ,t SILTS 6uVvS’FD0T CLAYS AND PLASTIC SILTS STRENGTH MziYi;E 1 ;; VERY SOFT 0 - v4 o-2 SOFT l/4 - vz 2 -4 FIRM ti - 1 4-6 STIFF 1 -2 8 - 16 VERY STIFF 2-4 16 -22 HARD OVER 4 OVER32 z Water level at ime of excavation or as indicated Undisturbed driven ring or chunk sample Disturbed bulk sample - 3 t 1 ": ENK 1 '08 No. 8691 K ETCHIJM ENGINEERING INC. 7818 OUE~RADA CIRCLE, C A RLSBAD (619) 944-1636 .F@ 92006& 1 =;; ~9;,‘!8; 1 r , 7 L I c & : 0’ 2 - 3 - I* a- 9. 10 * 11 - 12 - 13 - 14 - lj . E ; l 10 / y ’ ;i 2 : ;M - - - ‘RENCH NUMBER T-l ILEVATION OESCRIPTION FILL: Brown clayey silty fine coarse sand - WEATHERED METAVOLCANIC Reddish brown silty fi sandy clay METAVOLCANIC ROCK: Reddlsh brown rock Practical refusal @ 2. Dry Dry Moist Dry *> c 0 .rC, ;:= *w Fsn a 1 l og ” Loose Medium Stiff Very Dense . 0y' ENK JOB NO. 8691 K ETCHUM ENGINEERING OATE’ 8/20/86 7810 OUEBRADA CIRCLE, INC.‘= (6191 944-1836 C A RLSBAD PLATE NO.4 7 t t : ;I 0’ ,1 2 3 4 5 6 7 8 ij 10 11 12 I.3 14 1; :, c : ; i : i - :L RENCH NUMBER T-2 ,EVATION OESCRiPTlON hL : Reddish brown ilty clay w/rock to 8' EATHERED METAVOLCANIC: eddish Brown silty cl~ ,ETAVOLCANIC ROCK 'ractical refusal @ 3' Dry Dry ‘u* ;t!z “Ma c@-x *Ml :;a :gg 0 Mediun Stiff Very Dense I - . . - - By: ENK 1 JOB NO. 8691 I K ETCHUM ENGINEERING INC. 7816 OUEBAADA CIRCLE, C A RLSBAD (6191944-1636 DATE: a/20/86 PLATE NO. 5 3 f 4- 5- 6- 1- a- 9- 10 - 11 - 12 - 13 - 14 - 1; - TRENCH NUMBER T-3 ELEVATION n : u DESCRIPTION CL WEATHERED METAVOLCANICS Reddish brown silty cla; - - - Rock fragments METAVOLCANIC ROCK: Reddish brown Practical refusal @ 2' Dry Dry Medium Stiff Very Dense 1 By: ENK 1 JOa NO. 8691 K ETCHUM ENGINEERING INC? x 7818 QUEBR*D* CIRCLE, CARLSBAD (6191 944-1836 5- 6- 7- a- 9- 10 - 11 - 12 - L3 - 14 - lj - : DESCRIPTION :L WEATHERED METAVOLCANICS, Reddish brown silty cla: Dry METAVOLCANIC ROCK Dry 'racti .cal refusal @ 1.5 - Medium Stiff Very Dense BY: ENK JOB NO. 8691 I K ETCHUM ENGINEERING INC. 7818 OUEBRADA CIRCLE. C A RLSSAD (619) 944-1636 DATE: a/20/a PLATE NO. 7 5- 6- 7- a- 9- 10 - 11 - 12 - 13 - 14 - 15 - ‘RENCH NUMBER T-5 [LEVATION OESCAIPTION JEATHERED METAVOLCANICS leddish brown silty cla g/rock fragments IETAVOLCANIC ROCK ?ractical refusal @ 1.5 Dry ___ Dry Mediun Stiff Very Dense E a 2, x; t r* 0 I 0y' ENK I JOB NO. 8691 KETCHUM ENGINEERING INC. 7010 OUEBRADA (619) 944-1636 . ,, ‘RENCH NUMBER T-6 :LEVATION DESCRIPTION JEATHERED METAVOLCANICS Very ieddish brown silty cla Dry 2 4ETAVOLCANIC ROCK Dry Very Dense 3 Practical refusal @ 2' 4 +.:* *XL Y urn Sk3 2;;: :=s go Medium Stiff - : ii 2, g; 3 i 5 6 a 10 11 12 13 14 JOB NO. 8691 KETCHlJM ENGINEERING 7816 OUE~RADA CIRCLE, INC.“] DATE: 8/20/86 C ARLSBAD (619) 944-1636 PLATE NO. 9 ‘RENCH NUMBER ‘f-7 7 t t ELEVATION : : OESCRIPTION 0 WEATHERED METAVOLCANICS Dry Medium ReddIsh brown silty Stiff 1 clay 2 3 METAVOLCANIC ROCK Dry Very Dense 4 Practical refusal @ 3' 5 6 a 10 11 12 L3 14 BY: ENK KETCHUM ENGINEERING INC.“[ 7616 OUEBRADA CIRCLE I C A RLSBAD (619) 944-1636 JOB NO. 8691 DATE: g/20/86 PLATE NO. 10 ii 5 MO t: 2: i; ‘: MAXIMUM DENSITY & OPTIMUM MOlSTURE ~CONTENT ASTM : 1557 Reddish Brown Cla DIRECT SHEAR TEST RESULTS Sample Description Anglo of Internal Friction 1’11 ~prrr T-6 @ 1 Undisturbed 23 I 275 I EXPANSION TEST RESULTS BY: ENK JOB NO. 869, KETCHUM ENGINEERING INC.-x DATE: a/20/86 7818 OUEBRADA CIRCLE, C A RLSBAD I6191 946-1836 920OR PLATE NO. 1, ~T-:ii~r~iI~_~I.F:I!!,:i. 1. :: 1 ;“~. i ‘~; ; i~ ;r~ij i : 1 i, i : Y i 7 Y ~-: ! ‘:ili~~;!i::l~~::~iii’l-i’-, , ::i:!“~~il~Iii;i-~ I 1 I .-. . , . . . . ‘ i.., ..;i.~i.i I : : I : & ..I.. r ~1’:~~~ d , .~ __.. _-. . . . . I ‘::i”t; .-+ .,...,. ~.,;:, :"::"1'1. ..i _,._ _..:.. l....Lc Y ,. :.,,., ..i_..,. .I ;!::‘- ../I!, t... I..,, . . .‘1,15/.. ..i_~. ., ,_,... ~~ .:,.. ,, :; ~:.. ..,~.~,. ,, ..4;:: ., ,. .* :;. . .,. .I I ~;’ ...I I.‘~ ..,. : : ~:4 (1’ :._:_ L.. : : : : : liT : ::::.I iii:’ .+-. - .L , .,.,~ ,., 0:~. ‘. : ; ; : f ,., ..i.J ,a 1” . . I . /..t;: : j:i);;: .~. .I.. I ., . . ..a. I I. . . . . . . ..i .A . ..I ! .l...i ~. I I’ : I 1 in .,:. I I. ‘~ I “’ /----‘rrrrf ” :. ,I i : :~: r :‘:,:::I ,..;/,. ,~ ~,! , , ; j ~I. 8 ,.., ,. .~ ,I 90 66 261 I I I I I : 1 I I I .,,j !. ,,/, I I 1 .+5-i-j , :. 1 I, .,. I~ .,, ~. ..~;‘, ,/, 26 i!‘. 1 -t ,.,. II ! :, P , ” m ,.--. 1,. " 00 I/-- ,. \h old ', ' Lo- lo 20 20 40 w A0 70 w 90 lw iii too z l46 mo lw 206 120 I20 210 240 270 306 m Bear GEOLOGIST K ETCHUM ENGINEERING INC. looNo. 8691 ELEVATION 7810 OUEBRADA CIRCLE, C ARLSBAD ((II@) 044-1036 TRAVfRSE NO. ST-1 SIJRFKIAL MAT’L. TINEME TY?E ROCU TWE )y-:-: :;rrrrr;;i--;i;~r;~i-;~ii.[::.ir; :;I.~~:! ,YZrl:r~~~-;;:~I - ..; ;-‘, : : ;~; .: I” : : y-. + c. ,:ir. r: I. 1:: * :i ;.,I: .Ijfi:l:: I*.:” .,. ,.. .1. , I 4 . . ..,.. I :1 ;!:I:’ /. :,,,i;. ., .a~ ~, .:/ a . k’ i I .Ii :.:, ..,. MO loo so ;.!~.....‘:..,. ‘, .:t .~ : i,~~: t.. ,.i ,.i/;: ,~ i.~ ., .A ..,: : / . . . , :._:_ I... - 1 i:; (.I__ T1: m;,:j :,!rl.* 1. .?C .j. (6 / , -_. 8040 no ,. ,i,. 1 ‘i::::’ :Ll . ..i.., ” i;IY” , 4 , I , , t i ! I - _. .7&L-/ i 904030, ., I. ,.a. , I ,: . . I’ .,~ ,I, ., .., . ...’ 404020 ,I. ,I ,. ‘; :I / II ~~ no, *)~~.--.p A T 00 73 z ‘I ilr._ 0 L [,-,- ,--y 1 ,~ ,~I;1 M iii ¶o iii aI IO0 ii 40 ii 50 -_ a Iii 70 80 90 I40 m 200 -30 60 90 no % loo 2lo iii 270 300 DISTANCE - )os Bear CEOKXXT K ETCHUM ENGINEERING INC. mm. 8691 ELEVATKH 1616 aUE@RhD* CIRCLE, C ARLlbAD tsrmt 944-1036 OZOOI TRAVERSE No. ST-2 SURFKIAL MAT’L. TRlWaSl TYPE 6OCK TYPE i.. . --,iiz jJ-iiir;i;-7i;il;j. ..,;: 11.. =l2040 ii.. ._,. ,11 i k+ .~;’ ::!! y-’ 1; .;‘:I. .y i:;,.;ii:; : ;;i;ir’y ~~yv2~; ‘;~;;;~j-p (_ . , , . .ir,, /:,“‘:y ~i~~;l:~, ,, 1’ _ii ‘! :i:: G;m;~G,i~ ,,:,,; ~.,_..~~;:~j;,:,~,./:., ., :.,,.a ,. I ,__..... I it. ;!I;” .I/., 6 _.. . ..! 1 !.::I :.:!bf.!: :;~~~~~i~if .dL C,.. ,.,,i .~~ ../ . . , _. . . _ y l I., lsoloo50 ;~:...:..‘.,.. ‘~ ~~1:‘.:y .;.: i I I I I I ,,. ,.. I..Is’: ..,,, 1 . . . . . . . .,... ,., I,~. ,:- I .~, a:.. I. >... .,~.. ..I L ‘..’ : . IF- !.’ .‘~~I:?:- ~~. :I 1.:” :.” I j<i(::.. ,Y’:‘i:l’ “. ., , .I$ - : :..~l:: jj’.~I.~ ::::;i: * : I ,‘:;;-~:. i : ..:Il:= ” i :5-: EL ” . , ill.. .,., (.,, .t. ,_ ..it,.. ., ‘*:.‘- d l20 90 40 ./ ., maI I ,-;-:: 1,. ., ,, I “.li ;I. I ~’ I ‘i- .q - _- ,I~ ; 8 1, -T. ,, ,. .,/L ! , \, (..,~ ,. ,._. 1 .’ ::‘I. I ,, : ,I. ‘iii;;’ ~.. ,.~~ .,,. ‘,~,_.V IS I, -~%I K ETCHUM ENGINEERING INC. DISTANCE - (01,) 944-1836 lo6 Bear 7 KHJW. 8691 i 0200~~ TRAVERSENO. ST-3 TUB TWE GEOLOGIST ELEVATION SURFKIAL MAT’1 -K TY?f / I 1 y ::i I 1. : f-“-iyy; ,,C” f I$jJj $ , . . . I , :.‘!“,z’ . . L.~. i : L; [& .;. , .~._~. ._ . ./.. .‘( .,... ,,i.,, . .._...I. ..~ : ;;?li;i . . ..~.. :G$ . . ., I,~ -- : _. :Lii,t . : :,jii_r .~.. .: ..,! .j. .L i-r ;r.-T:. - 1’~ ,:‘(:’ ;!::..’ ,/:.;;;,. ,,_I... .-..: -’ ..I .I:’ * 1 ..~ ,. I : 4. ..I .- *f : I ~. . . I I ; ; I : ii: .: . ..,~ ..: ; ,.._. 1 : _. .I,. I./L: /I;:;:~ +. ,. I : :Ii:;iI 1 ..:. ./..., ! 4 ., , , I 4 *, .~ ,, ..., .~ t, I.. I ~. .~1 I ; I , I fg 4 , .I , 90 1 I no 1 D 270 3 ; ! ,. ,. I 70 l4c ma DISTANCE __, los Bear GEOLOGIST K ETCHUM ENGINEERING INC. jo8No. 869’ ELEVATtON 7018 OUEBIIAOA CIRCLE. c A llLS8 A0 tsle)Q44-183s e2008 TRAVERSE NO. ST-L SURFKIAL MAT’L. :.iy :, , ; rr.-.~‘ .,,” ,..T’. .~.,)Z. ,. ..I ---~.-I / 1 \.,,!. ---. . - i.. .il:: :‘. rr-:rrf 1 8 . ; i j ;J! l - . . . ..t.L ‘:.ll+ :ii?;i” : 4 _,_ t7. ,~.LT..” :i:;- ;;j;i;: + _i .)_ _,~ - i 1 -_ I b i ; Y: :l .._ij,, , 4 - - . / I .., . .~ :! : 4 . .!ir, ‘ , it. .;it.: . : i.:::.. ., . ,,I(, ,;/ ..:i, 1. . . ./.. 4 ..,I .., . . . i , .,:.* 1 i _.i.. . . . : , ‘I:::” !: ” S.//l<. .,_I..~ ,.I:.. ;::/;: j.j:;;:,, ,. ,. ,. ,. .a .>.. : 1 ..>. +. .I.,... .!~.... ~, .I. 4 : :!:i1: . ..I . , ,/ .~.I.. ,.~ ..:1 .~ ..< : I ,. ” :; 4 I .,. ,, ,.. : ; : 1: 1 ., 1 --yq : i!‘. 71 1 I iti 1 240 i DISTANCE ___, DJ Bear GEOLOGIST K ETCHUM ENGINEERING INC. loom. 8691 ELEVATKM ?818 OUEBI)AOA CIRCLE, C A RLSIAD (81*) 944-1836 TRAVERSE NO. ST-5 WRFKIAL MAT’L. TRM TWf KOCK TWE EXISTING GROUND SURFACE COMPACTED f ILL TOE KEY 2 FT. YIN. INTO FIRM GROUND HORIZONTAL BENCHES INTO FIRM GROUND, (I FT. YIN. ’ t ‘. TOE KEY WIDTH TO BE DETERMINED BY SOIL ENGINEER, BUT NOT LESS THAN IO FT. RECOMMENDATIONS FOR FILLING ON SLOPING GROUND Schematic Only net to scale PLATE NO. New Concrete Footing \ . . \WIfl * . Topsoil & Weathered : rlc‘ . Metavolcanics . ' . I Drill 1" $ hole into rock at 4' on center. Set #4 x 18" long with high strength expanding grout (Por Rot or equivalent). Footing Section By: ENK JOE NO. 8691 KETCHUM ENGINEERING INC.*= DATE: 9/3/86 7818 OUESRADA CIRCLE, C ARLSSAD ’ (619) 944-1836 PLATE NO. 18 APPENDIX A RECOMMENDED GRADING SPECIFICATIONS General Intent The intent of these specifications is to establish procedures for clearing, compacting natural ground, preparing areas to be filled and placing and compacting fill soil to the lines and grades shown on the accepted plans. The recommendations con- tained 'in the preliminary soil investigation report are a part of the recommended grading specifications and shall supersede the provisions contained hereinafter in the case of conflict. Inspection and Testing A qualified soil engineer shall be employed to observe and teat the earthwork in accordance with these specifications. It will be necessary that the soil engineer or his representative pro- vide adequate observations so that he may provide a memorandum that the work was or was not accomplished as specified. Deviations from these specifications will be permitted only upon written authorization from the soil engineer. It shall be the responsi- bility of the contractor to assist the soil engineer and to keep him appraised of work schedules, changes and new information and data so that he may provide the memorandum to the owner and govern- mental agency, as required. If in the opinion of the soil engineer, substandard conditions are encountered, such as questionable soil, poor moisture control, inadequate compaction, adverse weather, etc., the contractor shall stop construction until the conditions are remedied or corrected. Unless otherwise specified, fill material shall be compacted by the contractor while at a moisture content near the optimum . KETCHUY ENGINEERING INC’ moisture content to a density that is not less than 90% of the maximum dry density determined in accordance with A.S.T.M. Test No. D 1557-70, or other density test methods that will obtain equivalent results. Clearing and Preparation of Areas to Receive Fill All trees, brush, grass, and other objectionable material shall be collected, piled, and burned or otherwise disposed of by the contractor so as to leave the areas that have been cleared with a neat and finished appearance free from unsightly debris. All vegetable matter and objectionable material shall be removed by the contractor from the surface upon which the fill is to be placed, and any loose or porous soils shall be removed or com- pacted to the depth determined by the soil engineer. The surface shall than be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment to be used. When the slope of the natural ground receiving fill exceeds 20% (5 horizontal to 1 vertical), the original ground shall be stepped or benched as shown on the attached Plate A. Benches shall be cut to a firm competent soil condition. The lower bench shall be at least 10 feet wide and all other benches at least 6 feet wide. Ground slopes flatter than 20% shall be benched when considered necessary by the soil engineer. Fill Material Materials for compacted fill shall consist of any material import- ed or excavated from the cut areas that, in the opinion of the soil engineer, is suitable for use in constructing fills. The material shall conta,in no rocks or hard lumps greater than 12 inches in size KETCHUM ENGINEERING INC. and shall contain at least 40% of material smaller than l/4 inch in size. (Materials greater than 6 inches in size shall be placed by the contractor so that they are surrounded by compacted fines; no nesting of rocks shall be permitted.) No material of a perish- able, spongy p or otherwise improper nature shall be used in filling. Material placed within 36 inches of rough grade shall be select material that contains no rocks or hard lumps greater than 6 inches in size and that swells less than 3% when compacted as hereinafter specified for compacted fill and soaked under an axial pressure of 1.50'psf. Potentially expansive soils may be used in fills below a depth of 36 inches and shall be compacted at a moisture content greater than the optimum moisture content for the material. Placing Spreading and Compacting of Fill Approved material: shall be placed in areas prepared to receive fill in layers not to exceed six inches in compacted thickness. Each layer shall have a uniform moisture content in the range that will allow the compaction effort to be efficiently applied to achieve the specified degree of compaction to a minimum spec- ified density with adequately sized equipment, either specifically designed for soil compaction or of proven reliability. Compaction shall be continuous over the entire area, and the equipment shall make sufficient trips to insure that the desired density has been obtained throughout the entire fill. When the moisture content of the fill material is below that speci- fied by the soil engineer, the fill material shall be aerated by the contractor by blading, mixing, or other satisfactory methods until the moisture content is as specified. KETCHUM ENGINEERING INC. The surface of fill slopes shall be compacted and there shall be no excess loose soil on the slopes. Inspection Observation and compaction tests shall be made by the soil engin- eer during the filling and compacting operations so that ha can state his opinion that the fill was constructed in accordance with the specifications. The soil ‘engineer shall make field density tests in accordance with A.S.T.M. Test No. D1556-70. Density tests shall be made in the com- pacted materials below the surface where the surface is disturbed. When these tests indicate that the density of any layer of fill or portion thereof is below the specified density, the particular layer portion shall be reworked until the specified density has been obtained. The location and frequency of the tests shall be at the soil engin- eer's discretion. In general, the density tests will be made at an interval not exceeding two feet in vertical rise and/or 500 cubic yards of embankment. Protection of Work During construction, the contractor shall properly grade all exca- vated surfaces to provide positive drainage and prevent ponding of water. He shall control surface water to avoid damage to adjoin- ing properties or to finished work on the site. The contractor shall take remedial measures to prevent erosion of freshly graded areas and until such time as permanent drainage and erosion control features have bean installed. KETCHUM ENGINEERING INC. Unforeseen Condition In the event that conditions are encountered during the site pre- paration and construction that were not encountered during the pre- liminary soil investigation, Ketchum Engineering, Inc., assumes no responsibility for conditions encountered which differ from those conditions found and described in the preliminary soil investiga- tion report. KETCHUM ENGINEERING INC.