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HomeMy WebLinkAboutSoils Report 09.28.2016H-PvKUMAR Geotechnical Eng nearing j Engineering Geology Materials Testing 1 Environmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwoodOkumarusa.com Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado SUBSURFACE STUDY FOR FOUNDATION DESIGN PROPOSED SHOP BUILDING MYER PROPERTY 501 DAVIS POINT GARFIELD COUNTY, COLORADO PROJECT NO. 16-7-305 SEPTEMBER 28, 2016 PREPARED FOR: RANDO CONSTRUCTION ATTN: JOE RANDO P. O. BOX 1443 RIFLE, COLORADO 81650 d 1r4051 'msn.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS _ 2 - FIELD EXPLORATION _ 2 - SUBSURFACE CONDITIONS - 2 - DESIGN RECOMMENDATIONS _ 3 - FOUNDATIONS - 3 - FLOOR SLABS - 4 - SURFACE DRAINAGE _ g - LIMITATIONS - 5 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 LEGEND AND NOTES FIGURES 4 through 6 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS H -P - KUMAR Project No. 16-7-305 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed shop building to be located at the Myer Property, 501 Davis Point Road, northeast of Silt, 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 Rando Construction dated August 8, 2016. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsurface materials 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 subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed building will be a single story, steel frame and metal structure located on the site as shown on Figure 1. The floor will be slab -on -grade at an elevation slightly above the existing ground surface. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 4 feet. We assume moderate foundation loadings carried by column pads and connecting grade beam system, 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. H -P a KUMAR Project No. 16-7-305 -2 - SITE CONDITIONS The proposed building site is vacant and has undergone some previous grading. The grading included cuts up to about 10 feet high into the steep hillside to the west to level the site. The ground surface is gently sloping down to the east with an estimated 1 to 2 feet of elevation difference across the proposed building site. The site is currently used as a parking area. There are sandstone boulders on the hillside areas to the west up to about 4 feet in diameter. FIELD EXPLORATION The field exploration for the project was conducted on August 9, 2016. Two 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 subsoils and bedrock were taken with a 2 inch LD. California spoon sampler. The sampler was driven into the subsoils and bedrock at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration lest described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils and hardness of the bedrock. 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 encountered, below nil to a few inches of gravel surface for the parking area, consisted of about 1 foot of stiff, sandy clay and silt with shale fragments underlain by claystone/siltstone bedrock that extended down to depths drilled of 21 feet. The claystone/siltstone bedrock was weathered and medium hard becoming less weathered and hard to very hard with depth, and is of the Wasatch Formation. M -P k KUMAR Project No. 16.7.305 -3 - Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and swell -consolidation testing. The results of the swell -consolidation testing performed on relatively undisturbed drive samples of the claystone/siltstone, presented on Figures 4 through 6, indicate low to moderate compressibility under conditions of loading and wetting, with typically a minor hydro -compression potential. One sample (Boring 2 at 21/2 feet) showed a minor swell potential when wetted under a constant 1,000 psf surcharge. The samples that showed a hydro -compression potential may have been partly disturbed due to the sampling process in the hard bedrock. The laboratory testing is summarized in Table 1. No free water was encountered in the borings at the time of drilling or and the subsoils and bedrock were slightly moist. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing entirely on undisturbed bedrock materials. The minor swell potential encountered in one of the samples can be neglected in the foundation design. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed bedrock should be designed for an allowable bearing pressure of 3,000 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be up to about 1 inch depending on the foundation loading. There could be some additional settlement if the bearing materials were to become wetted and precautions should be taken to prevent wetting. 2) The footings should have a minimum width of 16 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 H -P t KUMAR Project No. 16-7-305 -4 - of foundations at least 36 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures, if any, should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 50 pcf. Any retaining walls should have a drain system to prevent build-up of hydro -static pressures behind the walls. 5) All existing fill, topsoil, clay and silt soils, and any loose disturbed materials should be removed and the footing bearing level extended down to the undisturbed bedrock materials. The exposed subgrade should then be moistened and compacted. 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 and bedrock, exclusive of topsoil, are suitable to support lightly loaded slab -on -grade construction. The bedrock could possess a low swell potential and should be further evaluated for expansion potential at the time of construction to determine if subexcavation of a shallow depth (possibly 1 to 2 feet) of the bedrock and replacement with imported road base is needed. To reduce the effects of some differential movement, 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. A minimum 4 inch layer of sand and gravel road base should be placed beneath the slab for support and to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve. H -P k KUMAR Project No. 16.7-305 -5 - Ali 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 soils and well broken bedrock, excluding topsoil and oversized rocks, or a road base material can be imported. SURFACE DRAINAGE A perimeter drain around the proposed building should not be needed due to the proposed floor "slab -at -grade" construction. 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 6 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. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. 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 locations indicated on Figure I, the proposed type of construction and our experience in the area. Our services do not include determining the H -P _ KUMAR Project No. 16-7-305 -6 - 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. 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 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, H-134- KU Ott David A. Young, P.E.3; Reviewed by: know Steven L. Pawlak, P.E. DAY/ksw cc: SGM - Jeff Simonson (jeffsm-inc.com) H -P t KUMAR Project No. 16-7-305 1 C 1 a Liar LQT1 t• MORE I. to smaterw —iLlr 1Nc,CVO sVIZUWi; task r 'rr a.�■�esr. rarrrrr,lJ i L � Ji retillartD ansrsour BORING 1 , r it BORING wirstr2 � r i + r r it f r rizt r aisrtrs r r 1 J 1 I •r ! r r :q i t ii j r r, gji • 0 i g jr 4 u rNsarir limb* i 1 ! ! Irawru1a Ii . I r 1 r 1 .r `"r r i/! 11 r 1 5,7 1 € i� o +r 1 ;e.;"l1 r r 4 r 501 DAVIS POINT ROAD `r_ r�rr� 30 0 30 60 APPROXIMATE SCALE—FEET r 1 1 1 1 a r 1 lPlr.rir/Npr•,mt !q r 1‹..----7- ! �‹ARw 7 ai fM 4:21,24:21,2• ! : 11 if 16-7-305 H-■ kKUMAR LOCATION OF EXPLORATORY BORINGS Fig. 1 11 aq sz� 16-7-305 0 - 5 - 10 - 15 Inm - 20 BORING 1 75/5 WC=6.4 D D=118 58/6 WC=4.8 DD=116 100/4 WC=4.8 O 0=93 100/1 100/4 BORING 2 1 1 1 1 1 82/5 WC=4.8 DD=125 100/6 100/4 50/0 50/2 0-1 5— gym, — 10--r 15 - 20- .m1 0- 25 25 - H—P-KUMAR LOGS OF EXPLORATORY BORINGS t I a Fig. 2 a a 1 1 ,h 1 RG i_ 4a LEGEND 7.7 7 FILL: GRAVEL FOR DRIVEWAY, ABOUT 3" THICK. ENCOUNTERED ONLY AT BORING 2. CLAY AND SILT (CL—ML); SANDY, GRAVELLY WITH SHALE FRAGMENTS, STIFF, SUGHTLY MOIST, BROWN. ICLAYSTONE/SILTSTONE BEDROCK; WEATHERED AND MEDIUM HARD BECOMING LESS WEATHERED AND HARD TO VERY HARD WITH DEPTH, SLIGHTLY MOIST, MIXED BROWN AND GRAY—BROWN. WASATCH FORMATION. I] RELATIVELY UNDISTURBED DRIVE SAMPLE; 2—INCH I.Q. CAUFORNIA LINER SAMPLE. 75/5 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 75 BLOWS OF A 140—POUND HAMMER FALLING 30 INCHES WERE REOUIRED TO DRIVE THE CAUFORNIA SAMPLER 5 INCHES. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON AUGUST 9, 2016 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 NOT MEASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPUED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE 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 (X) (ASTM 0 2216); DD = DRY DENSITY (pcf) (ASTM D 2216). 16-7-305 H -PN KUMAR LEGEND AND NOTES Fig. 3 11 1 0 —2 tlJ A —3 z 0 l= 2z—4 111 0 0 _5 SAMPLE OF: Weathered Clays1ane/SlItstane FROM: Oaring 1 0 2.5' WC = 6.4 X, DD = 116 pcf ILJJJr, I ' 1 I ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING boss UK ,i snip my is ma ealtpits *W. lie bail pawl Wail owl lir repos. ow. la VONA 11.• Brno 8080wel slow sal Amok,Us. 1.11 Coudimills lislarrzit .1 LA APPLIED PRESSURE - MSF 10 100 16-7-305 H-P-t-KUIVIAR SWELL -CONSOLIDATION TEST RESULT Fig. 4 1 nc 0 2 -1 x J —2 tat to —3 z 0 F= —4 0 (1) z 0 0 _r, —6 mlnipla, Wag. The bulk. nowt 114 Marl the mem soymel r.� idisw.,�++a rr swab .t SAMPLE OF: Weathered Ciaystane/S1ltstone FROM: Baring 1 0 5' WC = 4.8 X. DD = 116 pet ADDITIONAL COMPRESSION UNDE=R CONSTANT PRESSURE DUE TO WETTING 16-7-305 1.0 API'1JED PRESSURE — KSF 10 H -P k- KUMAR SWELL-CONSOLJDATION TEST RESULT 100 Fig. 5 Project No.18-7-305 CO F J CO w Ce Ce I- CO ID I- ,- 21- 0 H =ra J 0 CO m (r( 0 j Q 2 M to S01L OR BEDROCK TYPE Weathered Claystone/Siltstone Weathered Claystone/Siltstone II 1 Claystone/Siltstone 11 Weathered Claystone/Siltstone • UNCONFINED COMPRESSIVE STRENGTH (PSF) ATTERBERG LIMITS 0 53 x a at gM PERCENT PASSING NO. 200 SIEVE 0 Q 0 0 0 al - N re GRAVEL 1%) NATURAL DRY DENSITY (qcf} 00 —_ %0 u'1 N a NATURAL MOISTURE CONTENT (%) [r tD 00 4 00 4 00 4. _ _ LOCATION C N N 0 BORING N