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HomeMy WebLinkAboutObservation of Pit Excavation 12.09.2016H-P�INMAR Geotechnical Engineering ( Engineering Geology Materials Testing I Environmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwood®kumarusa.com December 9, 2016 RM Construction Attn: Eric Lintjer 5030 County Road 154 Glenwood Springs, Colorado 81601 eric@buildwithrm.com Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado Project No. 16-7-570 Subject: Observation of Pit Excavation, Proposed Residence, Lot 30, Heron Crossing at Ironbridge, River Bend Way, Garfield County, Colorado Gentlemen: As requested, a representative of H-P/Kumar observed the pit excavation at the subject site on November 8, 2016 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. The observation was conducted in accordance with our agreement for professional services with RM Construction dated November 2, 2016. Hepworth-Pawlak Geotechnical (now H-P/Kumar) previously conducted a subsoil study for preliminary design of foundations at the site and presented the findings in a report dated February 8, 2016, Job No. 116 014A. The residence is proposed to be single -story above crawlspace with slab -on -grade garage and located in the lower, front part of the lot. Shallow spread footings placed on the natural soils with precautions for limiting settlement potential and sized for an allowable bearing pressure of 1,500 psf were designed for the building support. Other settlement mitigation methods presented in the previous report include a structural slab foundation and a deep foundation to dense gravel. The recommended settlement precaution with spread footings was to deepen the bearing level to have no more than 6 feet of compressible, fine-grained soils below the footings. Since the previous boring on the lot encountered about 15 feet of the fine-grained soils, deepening the footing bearing level or replacing the fine-grained soils compacted would be needed. To further evaluate this settlement mitigation recommendation, an exploratory pit was dug on the lot which we sampled on November 8 for additional laboratory testing. The results of the testing, presented on Figures 1 and 2, indicate the soil compressibility is consistent with the previous report findings and settlement mitigation should be used below the proposed footings. The previous boring on the lot indicates the settlement potentia! is less below about 10 feet. Considering these findings, the recommended minimum depth of compacted soil below the proposed footings is 4 feet. We should further evaluate the soils exposed at the sub -excavated depth for bearing condition prior to backfill placement. Other recommendations presented in our previous report which are applicable should also be observed. RM Construction December 9, 2016 Page 2 The recommendations submitted in this letter are based on our observation of the soils exposed within the pit excavation and the previous limited subsurface exploration at the site. Variations in the subsurface conditions below the excavation could increase the risk of foundation movement. We should be advised of any variations encountered in the excavation conditions for possible changes to recommendations contained in this letter. 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 this special field of practice should be consulted. If you have any questions or need further assistance, please call our office. Sincerely, H -P , KUMAR Steven L. Pawlak, P.E. Rev. by: DEH SLP/ksw Attachments: Figures 1 and 2 — Swell -Consolidation Test Results H -P k Kt1MAR Project No. 16-7-570 r Moisture Content 5.8 percent 7 Dry Density = 83 pcf -200 = 83 percent Sample of: Sandy Silt From: Footing Grade in Pit Excavation Compression upon wetting ,,'- O N t0 % uoissojdwO0 CO O N r CO CO T N N O O APPLIED PRESSURE - ks1 T O ti i 0 3 4 5 6 7 8 9 10 11 Moisture Content 7.5 percent Dry Density 90 pcf -200 = 89 percent Sample of: Sandy Silt From: Pit Excavation, 3` Below Footing Grade Compression ,upon wetting 01 1.0 APPUED PRESSURE - ksf 10 100 16-7-570 H—P et KU MAR SWELL -CONSOLIDATION TEST RESULTS Figure 2 HEPWORTH-PAWLAK GEOTECHNICAL Hi pworth-PawI4. G4Aotetlmical, Inc 5020 County Road 154 GIonwooJ Springi, Colurrdo 81601 Phonc 970.945.7988 Fax• 970-945-8454 email: hp eo@hpgeotech.corn SUBSOIL STUDY FOR PRELIMINARY FOUNDATION DESIGN PROPOSED RESIDENCES LOTS 22, 30, 39 AND 52 HERON CROSSING AT IRONBRIDGE GARFIELD COUNTY, COLORADO JOB NO. 116 014A FEBRUARY 8, 2016 PREPARED FOR: BLUE HERON PROPERTIES, LLC ATTN: JIM LIGHT 430 IRONBRIDGE DRIVE GLENWOOD SPRINGS, COLORADO 81601 ht@chaffinlight.com Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 2 - SUBSIDENCE POTENTIAL - 2 - FIELD EXPLORATION - 3 - SUBSURFACE CONDITIONS - 4 - FOUNDATION BEARING CONDITIONS - 4 - PRELIMINARY DESIGN RECOMMENDATIONS - 5 - FOUNDATIONS - 5 - FLOOR SLABS - 6 - UNDERDRAIN SYSTEM - 7 - SURFACE DRAINAGE - 7 - LIMITATIONS 8 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 THROUGH 7 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 8 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for proposed residences to be located on Lots 22, 30, 39 and 52, Heron Crossing at Ironbridge, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop preliminary recommendations for foundation design. The study was conducted in general accordance with our proposal for geotechnical engineering services to Blue Heron Properties dated January 7, 2016 which included a scope of 8 exploratory borings. The proposal was modified by an email message from Eric Foerster dated January 25, 2016 to only include an exploratory boring on the four lots listed above. We previously conducted a preliminary subsoil study in the Heron Crossing at Ironbridge development area which included 4 exploratory borings and presented our findings in a report dated February 28, 2014, Job No. 113 471A. 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 preliminary foundation types, depths and allowable pressures of a building on each lot. This report summarizes the data obtained during this study and presents our conclusions, recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed residence construction had not been determined at this time and we understand the findings of this study will be considered in the purchase of the lots. For the purpose of our study, we assume the residences will be a one or two story, wood frame structure with or without basement level and located in the building envelope of each lot as shown on Figure 1. Ground floor could be structural over crawlspace or slab - Job No. 116 014A -2 - on -grade. Grading for the structures is assumed to be relatively minor with cut depths between about 3 to 8 feet. We assume relatively light foundation loadings, typical of the assumed type of construction. When building loadings; location and grading plans have been determined on a lot by lot basis, additional geotechnical evaluation, including additional subsurface exploration and analysis should be performed to develop design level recommendations. SITE CONDITIONS The lots were vacant at the time of our field exploration and covered with about 1 to 11/2 feet of snow. The ground surface had generally been rough graded with shallow cuts and fills up to about 3 to 5 feet deep based on the grading plan for the development. River Bend Way is asphalt paved and Blue Heron Drive appeared to have been graded to subgrade level. The natural ground surface generally slopes gently down to the northeast with on the order of 5 feet or less elevation difference across each building footprint. Lots 30 and 52 appeared to have been cut up to on the order of 3 to 4 feet below original ground surface and Lots 22 and 39 appeared to have been filled up to on the order of 3 to 4 feet above original ground surface. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the Ironbridge development. These rocks are a sequence of gypsiferous shale, fine-grained sandstone and siltstone with some massive beds of gypsum and limestone. There is a possibility that massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lots. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. Several sinkholes were observed during geologic assessments conducted for the Ironbridge development. These sinkholes appeared similar to others associated with the Eagle Valley Evaporite in areas of the Roaring Fork River valley. A sinkhole opened in the cart storage parking lot Job No. 116 014A Gtech -3 - in January 2005 and irregular bedrock conditions have been identified in the affordable housing site located roughly 500 to 1,000 feet south of the current development area. Sinkholes have not been identified in the immediate area of the subject lots. No evidence of cavities was encountered in the subsurface materials in the boring on each lot; however, the exploratory borings were relatively shallow, for foundation design only. Based on our present knowledge of the subsurface conditions at each lot, it cannot be said for certain that sinkholes will not develop. The risk of future ground subsidence on Lots 22, 30, 39 and 52 throughout the service life of the proposed residences, in our opinion, is low; however, the owner of each lot 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 January 27 and 29, 2016. 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 Hepworth-Pawlak Geotechnical, Inc. The snow had been plowed to each boring location to allow the truck rig access. Samples of the subsoils 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 retumed to our laboratory for review by the project engineer and testing. Job No. 116 014A G tech -4 - SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils typically consist of about 6 to 13 feet of sandy silt and clay overlying dense, slightly silty sandy gravel and cobbles with boulders. Drilling in the coarse granular soils with auger equipment was difficult due to the cobbles and boulders and drilling refusal was encountered in the deposit. Borings 1, 2 and 4 appear to be native soils and Boring 3 appears to be recently placed fill soils. Borings drilled for our previous study in this area and their location shown on Figure 1 encountered between about 1 to 16 feet of silt and clay soil above the dense gravel alluvium. Laboratory testing performed on samples obtained from the borings included natural moisture content and density and gradation analyses. Results of swell -consolidation testing performed on relatively undisturbed drive samples of the silt and clay soils, presented on Figures 4 through 7, indicate low to moderate compressibility under conditions of light loading and wetting. The samples typically showed a low collapse when wetted under constant light loading and moderate to high compressibility under additional Ioading after wetting. The two samples taken from a depth of 10 feet at Borings 2 and 4 (Lots 30 and 52) showed a minor expansion potential when wetted. The laboratory testing is summarized in Table 1. No free water was encountered in the borings at the time of drilling and the subsoils were slightly moist. FOUNDATION BEARING CONDITIONS The upper silt and clay soils have low bearing capacity and low to moderate mainly when wetted. Shallow spread footings placed on the natural silt and clay soils can be used with a risk of settlement as described below. The footing bearing level on Lots 22, 30 and 52 should be deepened below existing ground surface so there is no more than 6 feet of silt and clay soils below the bearing level as a compressibility potential Job No. 116 014A Ggstech foundation settlement mitigation measure, -- 5 - In sub -excavated areas to below design footing bearing level, and on Lot 39 where existing fill is removed, the onsite soils could be replaced compacted. Extending footing bearing level down or use of a deep foundation placed on the underlying dense gravel and cobbles soils could be used to achieve a low settlement risk. The building settlement and distress can also be limited by use of a structural slab/mat or post tensioned slab foundation. PRELIMINARY DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, the buildings be founded with spread footings bearing on the natural silt and clay soils or on compacted structural fill with a settlement risk. If a deep foundation or structural slab/mat foundation is desired, we should be contacted for supplemental recommendations. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on a limited depth of the undisturbed natural soils or on compacted structural fill should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect initial settlement of footings designed and constructed as discussed in this section will be about 1/2 tO 1 inch or less. Additional differential settlement up to about 1 inch could occur if the bearing soils are wetted. 2) The footings should have a minimum width of 20 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas 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. Job No. 116 0I4A Gmech -6- 4) Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at Ieast 55 pcf for the onsite silt and clay soil as backfill. 5) The existing fill, topsoil and loose or disturbed soils should be removed in the footing areas. The exposed soils in footing area should then be moistened to near optimum and compacted. Structural fill should extend laterally beyond the footing edges at least 1 the fill depth below the footing and be compacted to at least 98% of standard Proctor density at near optimum moisture content. The soils should be protected from frost and concrete should not be placed on frozen soils. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FLOOR SLABS The natural on-site soils, exclusive of topsoil, can be used to support lightly loaded slab - on -grade construction with a settlement risk if the bearing soils are wetted. Structural fill about 2 feet deep consisting of the onsite soils can be used to limit the settlement risk. To reduce the effects of some differential movement, non-structural 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 cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site silt and clay soils devoid of vegetation and topsoil. Job No. 116 014A H�h 7 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 site retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. An underdrain should not be used where there is shallow crawlspace (usually about 4 feet or less in height) and where slab -on -grade is near surrounding exterior grade, such as garages because the drain could result in wetting of shallow footing bearing level. Where provided, 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 1% to a suitable gravity outlet or sump. Free - draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 1'h feet deep. An impervious membrane such as a 20 mil PVC Iiner 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. SURFACE DRAINAGE Providing proper surface grading and drainage is very important to the satisfactory performance of the building. The following drainage precautions should be observed during construction and maintained at all times after each residence has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. Job No. 116 014A ditstech -8- 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maxirnurn 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. Soil lined drainage swales should have a minimum slope of 3 to 4%. 4) Roof gutters should be provided with downspouts and drains that discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation such as sod should be located at least 10 feet from foundations. Consideration should be given to use of xeriscape to reduce the potential for 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 this time. 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 Iocations 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 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 different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made. Job No, 116 014A G1 R9 This report has been prepared for the exclusive use by our client for planning and preliminary design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should conduct additional subsurface exploration and 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 to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK GE ■ . NICAL, INC. Steven L. Pawlak, P.E. Reviewed by: Daniel E. Hardin, P.E. SLP/ksw Job No, 116014A GVErtech RO4R/NG o RkR�I,FR APPROXIMATE SACLE: 1" = 120' • BORING FOR CURRENT STUDY O BORING FOR PREVIOUS STUDY (JOB NO. 113 471A, FEB. 28, 2014) DEPTH IN FEET TO TOP OF GRAVEL ALLUVIUM (8) 116 014A HEpwn rt-FPAWUIK GEOTECHNIc,ti NOTE: CONTOURS SHOWN ARE PRE -DEVELOPMENT LOCATION OF EXPLORATORY BORINGS Figure 1 Ui 0 5 10 15 20 25 BORING 1 LOT 22 15/12 WC=9.1 DD=101 -200=87 12/12 WC=5.9 DD=95 -200=71 13/12 WC=3 2 +4=3 -200=22 BORING 2 LOT 30 14/12 WC=5.3 DD=94 ://j 20/12 WC=6.6 DD=110 -200=88 :// 21/12 WC=8.8 DD=103 9/6,50/3 BORING 3 LOT 39 19/12 WC=83 DD=102 -200=76 20/12 WC=3 5 DD=115 -200=47 50/3 Note: Explanation of symbols is shown on Figure 3. 116 014A BORING 4 LOT 52 12/12 WC=8.3 DD=107 11/12 WC=72 DD=103 -200=85 0 5 13/12 10 WC=8.7 DD=109 Li a) 50/5 LOGS OF EXPLORATORY BORINGS 15 20 25 —I a Figure 2 LEGEND: 15/12 T SILT AND CLAY (ML -CL); sandy, scattered gravel (possible fill) in Boring 3 (Lot 39), very stiff, slightly moist, brown, low plasticity, slightly porous. SAND, GRAVEL AND COBBLES (GM -GP); silty to very silty, boulders, sand layer at Boring 1 (Lot 22), dense, slightly moist, brown, rounded rock. Relatively undisturbed drive sample; 2 -inch I.D. California liner sample, Drive sample; standard penetration test (SPT), 1 3/8 inch I.D. split spoon sample, ASTM 0-1586. Drive sample blow count; indicates that 15 blows of a 140 pound hammer falling 30 inches were required to drive the California or SPT sampler 12 inches. Practical drilling refusal. NOTES: 1. Exploratory borings were drilled on January 27 and 29, 2016 with 4 -inch diameter continuous flight power auger. 2. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory borings were not measured and the Togs of exploratory borings are drawn to depth. 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 approximate boundaries between material types and transitions may be gradual. 6. No free water was encountered in the borings at the time of drilling. Fluctuation in water level may occur with time. 7. Laboratory Testing Results: WC = Water Content (%) DD = Dry Density (pcf) +4 = Percent retained on the No. 4 sieve -200 = Percent passing No, 200 sieve 116 014A HE_P WD RTH•PAWLAK GCOTECH NJ AL LEGEND AND NOTES Figure 3 f 0 c 1 0 iv _ 0 E 2 0 0 Compression - Expansion % 3 1 0 1 2 Moisture Content = 8.3 percent Dry Density = 107 pcf Sample of: Sandy Silt and Clay From: Boring 4 at 2 Y Feet Compression upon wetting 0.1 1.0 10 APPLIED PRESSURE - ksf 100 Moisture Content = 8.7 Dry Density = 109 Sample of: Sandy Silty Clay From: Boring 4 at 10 Feet percent pcf Expansion upon wetting mar 0.1 1.0 10 APPLIED PRESSURE - ksf 100 Compression 0 1 2 3 4 5 Moisture Content = 5.9 percent Dry Density = 95 pcf Sample of: Sandy Silt and Clay From: Boring 1 at 4 Feet eN\ Compression upon wetting 0,1 116 014A 1.0 APPLIED PRESSURE - kst Hepwatth—Powick Gaotethnlcol 10 100 SWELL -CONSOLIDATION TEST RESULTS Figure 4 Compression % 0 1 2 3 4 5 6 7 8 9 10 Moisture Content = 5.3 percent Dry Density = 94 pcf Sample of: Sandy Sift and Clay From: Boring 2 at 2 Y Feet "'''''..,...„...„, -7 Compression upon wetting a, L 0.1 1.0 10 100 APPLIED PRESSURE = kst 116014A SWELL -CONSOLIDATION TEST RESULTS Figure 5 Compression % 0 1 2 3 4 5 6 n Moisture Content = 8.8 percent Dry Density — 103 pcf Sample of: Sandy Silty Clay From: Boring 2 at 10 Feet Expansion upon wetting 0.1 1.0 10 APPLIED PRESSURE - ksf Moisture Content = 8.3 percent Dry Density = 102 pcf Sample of: Sandy Silt and Clay From: Boring 3 at 2 Y Feet \, Compression � upon wetting 100 0.1 1.0 10 APPLIED PRESSURE - ksf 100 116014A SWELL -CONSOLIDATION TEST RESULTS Figure 6 14:121Zi.14*01Z121C MYt7HOME1 H ANALYSIS SIEVE ANALYSIS yy�� TIME READINGS U.S. STANDARD SERIES 1 CLEAR SQUARE OPENINGS --I{ 0 45 MlN 15 MIN 60MIN19MIN 4 MIN 1 MIN. #200 #100 #50 #30 #16 #8 10 20 30 40 50 60 70 80 90 100 #4 3/8' 3/4" 11/2' 3' 5' 6' 8' 100 1. i -4 1 r 'l- 001 ,002 005 009 019 037 .074 150 300 600 1-18 2.36 4.75 9 5 19-0 37.5 76.2 152 203 12 5 127 DIAMETER OF PARTICLES IN MILLIMETERS CIAY IO SLS GRAVEL 3 % LIQUID LIMIT % SAMPLE OF: Silty Sand with Gravel FeNE mu um f CUM1RSE. SAND 75 % GRAVEI. FPNE 1 cosASE COBBLES SILT AND CLAY 22 % PLASTICITY INDEX % FROM: Baring 1 at 9 Feet 90 80 70 60 40 30 20 10 0 HEPWORTH-PAWLA, .COTECHNICAL, INC. TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Job No. 116 014A SAMPLE LOCATION NATURAL MOISTURE CONTENT (%) NATURAL DRY DENSITY (pci) GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH (PSF) SOIL OR BEDROCK TYPE BORING/LOT DEPTH (ft) GRAVEL (%) SAND (%) LIQUID LIMIT (%) PLASTIC INDEX (%1 1/22 21 9.1 101 87 i Sandy Silt and Clay 4 5.9 95 71 Sandy Silt and Clay 9 3.2 3 75 22 Silty Sand with Gravel 2/30 21 5.3 94 Sandy Silt and Clay 5 6.6 110 88 Sandy Silt and Clay 10 8.8 103 Sandy Silty Clay 3/39 21 8.3 102 76 Sandy Silt and CIay I 41/2 3.5 115 47 Very Sandy Silt and CIay with Gravel 4/52 21 8.3 107 Sandy Silt and Clay 5 7.2 103 85 Sandy Silt and Clay 10 8.7 109 Sandy Silty Clay J