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HomeMy WebLinkAboutSoils Report 04.05.2017H-PKUMAR Geotechnical Engineering 1 Engineering Geology Materials Testing t Environmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 80, IRONBRIDGE 1102 RIVER BEND WAY GARFIELD COUNTY, COLORADO PROJECT NO. 17-7-236 APRIL 5, 2017 PREPARED FOR: RICK SAGESER 15878 WEST ELLSWORTH DRIVE GOLDEN, COLORADO 80401 ricksageser@comcast.net TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS .... 1 GEOLOGY -2- FIELD EXPLORATION - 3 - SUBSURFACE CONDITIONS - 3 - FOUNDATION BEARING CONDITIONS - 4 - DESIGN RECOMMENDATIONS .., - 4 - DRILLED PIERS - 4 - FOUNDATION ALTERNATIVE - 5 - FOUNDATION AND RETAINING WALLS - 6 - FLOOR SLABS (NON-STRUCTURAL) - 7 - UNDERDRAIN SYSTEM - 8 - SURFACE DRAINAGE - 9 - LIMITATIONS - 9 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 and 5 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS H -P KUMAR Project No. 17-7-236 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 80, Ironbridge, 1102 River Bend Way, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Rick Sageser, dated March 16, 2017. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsoil conditions encountered. PROPOSED CONSTRUCTION The proposed residence will be located in the building envelope of the lot as shown on Figure 1 and consist of a single -story structure above a walkout basement with slab -on -grade floors. Grading for the structure will be relatively minor with minimal cut depths up to about 3 feet for the basement level and fill depth of about 6 to 7 feet for the garage level. We assume relatively light foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The lot was vacant at the time of our field exploration and is located on a gently sloping alluvial fan along the downhill, eastern side of River Bend Way. Elevation difference across the building footprint is about 2 feet. A dry detention basin fed by runoff from River Bend Way and a dry H-PkKUMAR Project No. 17-7-236 -2 - drainage channel are located immediately north of and parallel to the lot. The ground surface of the building area appears to have been cleared of brush. Vegetation consists of grass and weeds with sage brush in the downhill, east part of the lot. The Roaring Fork River level is about 20 to 25 feet below the lot. GEOLOGY The geologic conditions were described in the previous report conducted for planning and preliminary design of the overall subdivision development by Hepworth-Pawlak Geotechnical (now HP/Kumar) dated October 29, 1997, Job No. 197 327. The surficial soils on the lot mainly consist of sandy silt and clay alluvial fan deposits with interbedded sandy and gravelly layers overlying gravel terrace alluvium of the Roaring Fork River. The river alluvium is mainly a clast-supported deposit of rounded gravel, cobbles and boulders typically up to about 2 to 3 feet in size in a silty sand matrix which extends down to depths on the order of 35 feet in the Lot 80 area and overlies siltstone/claystone bedrock. Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the Ironbridge subdivision. These rocks are a sequence of gypsiferous shale, fine-grained sandstone and siltstone with some massive beds of gypsum and limestone. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. An apparent sinkhole was observed about 300 feet south of Lot 80 along the south side of River Bend Way and River Bank Lane intersection during the roadway construction. The sinkhole was excavated and backfilled during construction of the roadway. A sinkhole occurred in the parking lot adjoining the golf cart storage tent in 2005 located about 1/4 mile to the northwest of Lot 80 which was backfilled and compaction grouted. Both sinkholes have not shown signs of reactivation such as ground subsidence since the remediation, to our knowledge. Sinkholes possibly related to the Evaporite were not observed in the immediate area of the subject lot. An apparent soil piping cavity was observed in the bottom of the detention basin close to the northwest corner of the lot which appears to outlet in the adjacent drainage channel. Based on our present knowledge of the subsurface conditions at the site, it cannot be said for certain that sinkholes related to the underlying Evaporite will not develop. The risk of future ground subsidence on Lot 80 throughout the service life of the proposed building, in our opinion, is low; however, the owner H-PttNMAR Project No. 17-7-236 -3 - should be made aware of the potential for sinkhole development. If further investigation of possible cavities in the bedrock below the site is desired, we should be contacted. FIELD EXPLORATION The field exploration for the project was conducted on March 23, 2017. Four exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. The borings were advanced with 4 -inch diameter continuous flight augers powered by a truck- mounted CME -45B drill rig. The borings were logged by a representative of H-P/Kumar. Samples of the subsurface materials were taken with 1% inch and 2 inch I.D. spoon samplers. The samplers were driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils consist of about 91/2 to 131/2 feet of stiff to very stiff, sandy silt and clay overlying dense, silty sandy gravel and cobbles with boulders. Drilling in the dense gravel with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and finer than sand size gradation analyses. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the sandy silt and clay soils, presented on Figures 4 and 5, indicate low to moderate compressibility under relatively Tight loading and natural low moisture conditions. A low collapse potential (settlement under constant Toad) and moderate to high compressibility were typically observed when the samples were wetted and additionally loaded. The laboratory testing is summarized in Table 1. H -P KUMAR Project No. 17-7-236 -4 - Free water was not encountered in the borings at the time of drilling and the soils were slightly moist. FOUNDATION BEARING CONDITIONS The subsoils encountered to a depth of about 10 to 13 feet typically consist of low density and compressible silt and clay. These soils are typically hydrocompressive and tend to settle under Toad when wetted. The expansion potential measured on the samples is not considered significant and the overall alluvial fan soils will tend to settle when wetted under load. The proposed fill below the garage area will add to the variability of a shallow supported foundation. In residential areas there are several sources of potential wetting such as landscape irrigation, surface water runoff and utility line leaks. A relatively low risk foundation system with respect to variable subsurface conditions and potential settlement caused by wetting of the upper compressible soils is straight -shaft drilled piers that extend down into the dense gravel and cobble soils. In addition to their ability to reduce settlements, the piers have the advantage of providing moderate load capacity with a relatively small settlement potential. DESIGN RECOMMENDATIONS DRILLED PIERS Considering the subsoil conditions encountered in the exploratory borings and the nature of the proposed development plan, we recommend straight shaft piers drilled into the underlying gravel and cobble soils for building support. The design and construction criteria presented below should be observed for a straight -shaft drilled pier foundation system. 1) The piers should be designed for an allowable end bearing pressure of 12,000 psf and a skin friction of 1,000 psf for that portion of the pier embedded in gravel. Pier penetration through fill soils and the upper, natural silt and clay soils should be neglected in the skin friction calculations. 2) All piers should have a minimum total embedment length of 10 feet and a minimum penetration into the gravel of 1 foot. The gravel and cobble soils will tend to cave and penetration into the bearing soils should be limited to about 2 feet. H-PtKUMAR Project No. 17-7-236 -5- 3) The pier holes should be properly cleaned prior to placement of concrete. The natural silt and clay soils are stiff which indicates that casing of the holes should not be required. Some caving and difficult drilling may be experienced in the bearing soils due to cobbles and possible boulders. Placing concrete in the pier hole the same day as drilling is recommended. 4) The pier drilling contractor should mobilize equipment of sufficient size to achieve the design pier sizes and depths. We recommend a minimum pier diameter of 12 inches. 5) Grade beams and pier caps should have a minimum depth of 3 feet for frost cover and void form below them is not needed. 6) Free water was not encountered in the borings made at the site where the dense gravel and cobble soil was encountered and it appears that dewatering should not be needed. 7) A representative of the geotechnical engineer should observe pier drilling operations on a full-time basis. FOUNDATION ALTERNATIVE As an alternative with an increased risk of differential settlement and distress, the residence could be supported by a heavily reinforced structural mat or post -tensioned slab foundation bearing on at least 5 feet of compacted structural fill. The design and construction criteria presented below should be observed for a structural slab foundation system. I) A structural slab or post -tensioned slab placed on a minimum 5 feet of compacted structural fill can be designed for an allowable bearing pressure of 1,000 psf. A post -tensioned slab should also be designed for a wetted distance of 10 feet but at least half of the slab width whichever is greater. Based an experience, we expect initial settlement to be about I inch or less. Additional differential settlement of about 1 to 2 inches is estimated if deep wetting of the alluvial fan soils were to occur. 2) Prior to placing structural fill for the foundation support, the area should be stripped of the vegetation and topsoil. Structural fill should be placed in uniform lifts not to exceed 8 inches and compacted to at least 98% of the maximum H-P't KUMAR Project No. 17-7-236 -6 - standard Proctor density at a moisture content within 2% of optimum. Fill should extend laterally beyond the edges of the foundation slab a distance at least equal to the depth of fill below the slab. The structural fill should have sufficient fines content to restrict subsurface water flow such as the on-site silt and clay soils. 3) The thickened sections of the slab for support of concentrated loading should have a minimum width of 20 inches for continuous walls and 2 feet for isolated columns. 4) The perimeter turn -down grade beams should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 36 inches below exterior grade is typically used in this area. 5) A representative of the geotechnical engineer should evaluate fill placement for compaction and observe the completed excavation prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 55 pcf for backfill consisting of the on-site soils. Cantilevered retaining structures which are separate from the residence and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at near optimum moisture content. Backfill placed in pavement and H-P*KUMAR Projecl No. 17.7-236 FLOOR SLABS I -7 - walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected even if the material is placed correctly and could result in distress to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.35. Passive pressure of compacted backfill against the sides of the footings or drilled piers can be calculated using an equivalent fluid unit weight of 300 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safely should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be compacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. NON-STRUCTURAL) The upper fine-grained soils encountered in the borings possess variable compressibility potential and slab settlement could occur if the subgrade soils were to become wet. Slab -on - grade construction can be used provided precautions are taken to limit potential settlement and the risk of distress to the building is acceptable to the owner. Removal and replacement of the natural soils to provide at least 2 feet of compacted structural fill below slabs should be done to reduce the risk of slab settlement. The structural fill should be constructed similar to that described above in "Foundation Alternative" recommendations. To reduce the effects of some differential settlement, nonstructural floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage H-PkKUMAR Project No. 17.7-236 -8 - cracking. Slab reinforcement and control joints should be established by the designer based on experience and the intended slab use. A minimum 4 -inch layer of base course gravel should be placed immediately beneath slabs -on - grade. This material should consist of minus 2 -inch aggregate with less than 50% passing the No. 4 sieve and less than 12% passing the No. 200 sieve. The gravel will provide slab support and help break capillary moisture rise. Required fill placed beneath slabs can consist of the on-site soils, excluding topsoil or a suitable imported granular material such as road base. The fill should be spread in thin horizontal lifts, adjusted to near optimum moisture content, and compacted to at least 95% of the maximum standard Proctor density. All topsoil and loose or disturbed soil should be removed and the subgrade moistened and compacted prior to fill placement. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below -grade construction, such as retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free -draining granular material. The drain should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum I% to a suitable gravity outlet. Free -draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, Tess than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep. An impervious membrane such as 20 mil PVC should be placed beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing soils. The foundation drain should not be placed around the uphill side of the garage nor the downhill H -P kUMAR Project No. 17-7-236 -9 - side of the basement level since the finished floor elevation at the respective level will be at or above the adjacent surrounding finish grade. SURFACE DRAINAGE Providing proper perimeter surface grading and drainage will be critical to the satisfactory performance of the building. The following drainage precautions should be observed during construction and maintained at all times after the building has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill and preferably into subsurface solid drain pipe to gravity discharge. Surface swales should have a minimum grade of 3% and preferably 4%. 5) Landscaping which requires regular heavy irrigation should be located at least 10 feet from foundation walls. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the building caused by irrigation. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at the time of this study. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in Fi-P3 KUMAR Project No. 17-7-286 -10 - this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear to be different from those described in this report, we should be notified at once so re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications of the recommendations presented herein. We recommend on-site observation of pier drilling, excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, H -P KUMAR Steven L. Pawlak, P Reviewed by: 15222 ;* Daniel E. Hardin, P.E. SLP/ksw cc: David Berton (david@realarchitecture.com) H-P3EKUMAR Prosect No. 17.7-236 1 •6u SONIIO8 AdOlVdOldX3 JO NOI1V001 &VW K -d -H 9TZ—L—LI 133J-1VZ S 3 VW XOdddd OT Si 0 SI BORING 1 EL, 5942.5' BORING 2 EL. 5943' BORING 3 EL. 5941.5' BORING 4 EL. 5941' 5950 5950 -- GARAGE FLOOR LEVEL = 5949' - 5945 5940 -- 5935 r- - 5930 5925 19/12 WC=4.7 00=104 29/12 WC=7.3 D0=116 -200=90 21/12 42/5,50/3 BASEMENT FLOOR LEVEL = 5942' 20/12 20/12 WC=8.1 00=107 -200=94 10/12 WC=11.9 00=112 50/5 14/12 WC=3.2 DD=98 18/12 WC=8.4 00=109 -200=91 15/12 WC=5.3 00=104 -200=58 17/12 12/12 WC=9.7 DD=110 80/12 5945 --y 5940 -- 5935 - 5930 -- 5925 5920 5920 17-7-236 H-P�KUMAR LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND 7 F CLAY AND SILT (CL—ML); SLIGHTLY SANDY TO SANDY, SILTY SAND LAYER BELOW 10' IN BORING 3, STIFF TO VERY STIFF, SLIGHTLY MOIST, LIGHT BRAWN TO BROWN, SLIGHTLY POROUS. GRAVEL AND COBBLES (GM—GP); SILTY TO SLIGHTLY SILTY, SANDY, BOULDERS, DENSE, SLIGHTLY MOIST, BROWN, ROUNDED ROCK. RELATIVELY UNDISTURBED DRIVE SAMPLE; 2—INCH I.D. CALIFORNIA LINER SAMPLE. DRIVE SAMPLE; STANDARD PENETRATION TEST (SPT), 1 3/19 INCH I.D. SPLIT SPOON SAMPLE, ASTM 0-1566. 19/12 DRIVE SAMPLE OLOW COUNT. INDICATES THAT 19 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE CALIFORNIA OR SPT SAMPLER 12 INCHES. I PRACTICAL AUGER REFUSAL. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON MARCH 23, 2017 WITH A 4—INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROX MATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); OD = DRY DENSITY (pct) (ASTM D 2216); —200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM 0 1140). 17-7-236 H -P- KUMAR LEGEND AND NOTES Fig. 3 CONSOLIDATION - SWELL CONSOLIDATION 1 —1 —2 —3 —4 SAMPLE OF: Sandy Sill and Clay FROM: Boring 1 CO 2.5' WC = 4.7 %, 0D = 104 pcl ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING I,0 4 PIIi[1 PRESSL'Rt I{SF SAMPLE OF: Sandy Silly Clay FROM: Boring 2 ® 10' WC = 11.9 %, DD = 112 pcl m... 4,11 r..jnr 40.1 mr tS w Mrphr 1.164. R. 411r, mind I4004.4M.....a1 n 10..+f..I 1M •Man .pro' -0 Rwna rn. 41......r. +1t- &..n esv4...0 *Pu o -fl EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 17-7-236 1.0 APPC'ER PRESS':RE KSF I 100 H-P�KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 4 CONSOLIDATION - SWELL CONSOLIDATION - SWELL SAMPLE OF: Sandy Sill and Clay FROM: Boring 3 0 2.5' WC = 3.2 %, DD = 98 loaf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 114.7 lid .yu UN! M6k W I.mptil 1.r.111 Il.. IdI4 $ 1. I vN M M npnMa.f. 1,4 .imvt 1M Sl.. **Iwo! le Na.r. IK M..pl...lr, 5.0 Cnr.14d.w1 kltn /1+rrmM wM. tql WW 11.171t 1.11 APPLICD PRESSURE — xsr fR tC] SAMPLE OF: Sandy Silly Clay FROM: Goring 4 0 5' WC = 9.7 %, DD = 110 pef 1.4 APPLIED PRESSJRE - K5F EXPANS'ON UNDER CONSTANT PRESSURE UPON WETTING lo. ! 17-7-236 H-P--15KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 5 H-FKUMAR TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No.17-7-236 SAMPLE LOCATION GRADATION 1 ATTERBERG LIMITS UNCONFINED NATURAL MOISTURE CONTENT (%) i NATURAL DRY DENSITY( (pcf) GRAVEL "o) E SAND (%1 PERCENT PASSING N0.2d0 SIEVE LIQUID LIMIT (%) PLASTIC INDEX (%) COMPRESSIVE STRENGTH (PSF) SOIL TYPE BORING DEPTH (ft) 1 ? % 4.7 104 Sandy Silt and Clay 5 7.3 116 90 Sandy Silt and Clay 1 l (l7 g4 Slightly Sandy Silt and Clay 10 11.9 112 Sandy Silty Clay 2'> 3.1 98 Sandy Silt and CIay 5Clay 4 109 9l Slightly Sandy Silt and 10 5.3 104 58 Very Sandy Silt L 4 5 9.7 110 Sandy Silty CIay 1- _