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Home My WebLink AboutSoils Report for Foundation Design 11.07.2007GeoteCh HEPWORTH - PAWLAK GEOTECHNICAL 1I(ru mh I'i„1.31, him +I. Ing i0200 iirirti F:,,.t,1 154 ltit .,1,,ri,l, Flo, nr 070 04i 70,ti F• '470 nut] hi- SUBSOIL o1 SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED SCHNEIDER RESIDENCE LOT E-52, ASPEN GLEN SUBDIVISION KINGFISHER LANE GARFIELD COUNTY, COLORADO JOB NO. 107 0760 NOVEMBER 7, 2007 PREPARED FOR: JORDAN ARCHITECTURE ATTN: BRAD JORDAN P.O. BOX 1031 GLENWOOD SPRINGS, COLORADO 81602 I),Iri:cr ilk;- 4I -i1 IQ • t.,rirlroJ,+ ',prin., 71y.r„;-7)0= • 'Il1trill. nl. '410 4' 1 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - I - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS _ _ SUBSIDENCE POTENTIAL FIELD EXPLORATION -3 - SUBSURFACE CONDITIONS -3 - DESIGN RECOMMENDATIONS - 4 - FOUNDATIONS - 4 - FLOOR SLABS - 5 - SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - REFERENCES - 7 - FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2- LOGS OF EXPLORATORY BORINGS FIGURE 3- LEGEND AND NOTES FIGURE 4- GRADATION TEST RESULTS PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for the proposed Schneider residence to be located on Lot E-52, Aspen Glen Subdivision, Kingfisher Lane, 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 Jordan Architecture dated October 3, 2007. Chen-Northem, Inc. (1991 and 1993) previously conducted preliminary geotechnical engineering studies for the development and preliminary plat design. 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 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 residence will be a two story wood frame structure with an attached garage. Ground floor will be structural over a crawlspace for the living areas and slab -on -grade in the garage. There will be a second story of living space above the garage. Grading for the structure is assumed to be relatively minor with cut depths between about 3 to 4 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. Job No. 107 0760 G ech -2 - If building loadings, Iocation 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 site was vacant at the time of our field exploration. There is an existing pond to the east of the lot. The ground surface is relatively flat with a gentle slope down to the northwest at grades up to about 6% and about 2 feet of elevation difference. Vegetation consists of grass and weeds. Scattered cobbles were exposed on the ground surface. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the Aspen Glen development. These rocks are a sequence of gypsiferous shale, fine-grained sandstone:isiltstone and limestone with some massive beds of gypsum. There is a possibility that massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. During previous studies in the area, several broad subsidence areas and smaller size sinkhole areas were observed scattered throughout the Aspen Glen development, predominantly on the east side of the Roaring Fork River (Chen -Northern, Inc., 1993). The nearest sinkhole was mapped about 450 feet to the southwest of Lot E-52 and a broad subsidence area was mapped just to the north of the lot. These sinkholes appear similar to others associated with the Eagle Valley Evaporite in areas of the Roaring Fork River valley. Sinkholes were not observed in the immediate area of the subject lot. No evidence of cavities was encountered in the subsurface materials; however, the exploratory borings were relatively shallow, for foundation design only. Based on our present knowledge of the subsurface conditions at the site, it cannot be said for certain that sinkholes will not develop. The risk of future ground subsidence on Lot E-52 throughout the service life of the proposed residence, in our opinion, is low; however, the owner should be made aware Job No I07 0760 GecPtech -3 - 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 October 30, 2007. 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 Hepworth-Pawlak Geotechnical, Inc. Samples of the subsoils were taken with a I% inch I.D. spoon sampler. The sampler was 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 1 foot of topsoil overlying relatively dense, slightly silty sandy gravel with cobbles and boulders to the drilled depths of 11 and 141/.. feet. Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of gradation analyses performed on small diameter drive samples (minus 11:2 inch fraction) of the coarse granular subsoils are shown on Figure 4. Job No. 107 0760 Gtech -4 - No free water was encountered in the borings at the time of drilling and the subsoils 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 on the natural granular subsoils. The design and construction criteria presented below should be observed for a spread footing foundation system. I) Footings placed on the undisturbed natural granular subsoils 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 about 1 inch or less. 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 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 should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 50 pcf. 5) The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the natural granular soils. The exposed soils in footing area should then be moistened and compacted. Job No. 107 0710 -5- 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, are suitable to support lightly loaded slab - on -grade construction. To reduce the effects of some differential movement, 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 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 free -draining gravel should be placed beneath interior slabs -on -grade 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 2% passing the No. 200 sieve. 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 soils devoid of vegetation, topsoil and oversized rock. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: I) 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° o of the maximum standard Proctor density in pavement and slab areas and to at Ieast 90% of the maximum standard Proctor density in landscape areas. lob No. 107 0760 Ga tech -b- 3) The ground surface surrounding the exterior of the building should be sloped to dram 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) Roofdownspouts and drains should discharge well beyond the limits of al backfill. 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 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. 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 Joh No. 107 0760 Ge gtech -7 - bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Jordy Z. Adamson, Jr., P.E. Reviewed by: Steven L. Pawlak, P.E. JZAJvad REFERENCES Chen -Northern, Inc., 1991, Preliminary Geotechnical Engineering Study, Proposed Aspen Glen Development, Garfield County, Colorado, prepared for Aspen Glen Company, dated December 20, 1991, Job No. 4 112 92. Chen -Northern, Inc., 1993, Geotechnical Engineering Study for Preliminary Plat Design, Aspen Glen Development, Garfield County, Colorado, prepared for Aspen Glen Company, dated May 28, 1993, Job No. 4 112 92. Job No. 107 0760 APPROXIMATE SCALE 1"=30' LOT E-51 107 0760 1000 \ \ 1001 LOT E-52 • BORING 2 r PROPOSED RESIDENCE BORING 1 • HEPWORTH.PAWLAK GEOTECHNICAL. 1000 KINGFISHER DRIVE 1001 1002 1 1 - 1 --� 1 \ 1002 LOCATION OF EXPLORATORY BORINGS LOT E-53 Figure 1 1005 1000 995 990 985 BORING 1 ELEV.= 1002' 20/6,18/3 4' 45/12 WC=1.7 s a +4=48 -200=9 BORING 2 ELEV.= 1000' Q .e. So' • �S sa 47/12 28/6,23/3 WC- 1 7 +4=61 -200=8 60/12 31/6,19/3 d1 Note: Explanation of symbols is shown on Figure 3. 1005 1000 995 990 985 Elevation - Feet 107 0760 H Hepworth—Pawlak Geotechnical LOGS OF EXPLORATORY BORINGS Figure 2 LEGEND_ r TOPSOIL; sandy silt and clay, organics, roots, firm, slightly moist, brown GRAVEL (GP -GM); sandy, slightly silty, with cobbles and boulders, dense, slightly moist, brown. Drive sample; standard penetration test (SPT), 1 3/8 inch LD. split spoon sample, ASTM D-1586. 45/12 Drive sample blow count: indicates that 45 blows of a 140 pound hammer falling 30 inches were required to drive the SPT sampler 12 inches. NOTES: 1. Exploratory borings were drilled on October 30, 2007 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 obtained by interpolation between contours shown on the site plan provided and checked by instrument level. 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 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 a Water Content (%) +4 = Percent retained on the No. 4 sieve -200 Percent passing No 200 sieve 107 0760 HEPWOmi+PAWLAK GEOTECHNICAL LEGEND AND NOTES Figure 3 'CENT RETAIN BA ENT RETAIN It HYDROMETER ANALYSIS I SIEVE ANALYSIS I TIME READINGS f U.S. STANDARD SERIES 1 CLEAR SQUARE OPENINGS 4411N.175MIN. 60MIN19MIN.4 MIN. 1 MIN. #200 *100 4150 #30 #16 #8 #4 3/8' 314' 1 112' 3' 5'6' 8' 0 ---'—tea--a— too MI SSA Si MS i SI MI MS IMI SO =e—I—eSIS- 10 20 30 40 50 60 70 80 90 100 MISSES e S SEM AMPS SAS S SIIsm same alleS SWAIM — �P —1 —r -r SI a I' =ISSN SS =MS —r_ a -- ---� --a- -� IS_eller-� —�.-------SIE �. — S. s- is s ill— IM is—r a SIMSWS - --SI --- --a— .�Sa—rISl--a— a ----.-- MS it ea ------ 1 s Sim US is r_---t—a-- —et--- PSIS MS —.— —I -rte ---- PSIS SI SI a s —�� ate— -- SAMillS--------1-- ae'S a a— 'sa ire-- SAMS SA • S —a a— ^— MIS Slem- —�- pie— �l SWIMS Was Was —ea— a_MIS ate- — — ae-- eals a� -I-•— SI ES S MIS SI SEr AOt .002 .005 .009 019 A37 .071 150 333 .&C ite 136 DIAMETER OF PARTICLES IN MILOMETERS ar---- --- SIM - r --- a�Sr —SS AMISS --- —mss —--I- —I— ----- --- -r- Sa- S SI a, �-ENE SISSSIMISI— r--_ 4.75 9.512.5 19.0 37.5 712 152 203 127 MAY TO STET NNE SAND 1.E04A 1 came (comae NNE 1 COARSE COBBLES GRAVEL 48 % LIQUID LIMIT % SAMPLE OF: Slightly Silty Sand and Gravel SAND 43 % SILT AND CLAY 9 % PLASTICITY INDEX % FROM: Boring 1 at 5 Feet HYDROMETER ANALYSIS U.S.SIEVE ANALYSIS 1 TIME READINGS STANDARD SERIES 1 CLEAR SQUARE OPENINGS I 45 IN. 15 MIN 60MIN19MIN 4 MIN. 1 MIN. #200 #100 #50 #30 #16 #8 #4 318' 3/4' 1 112' 3' 5'6' 8' —�, 100 10 20 30 40 50 60 70 80 90 100 001 002 005 009 019 037 074 150 300 .600 1 18 2.36 DIAMETER OF PARTICLES IN MILLIMETERS EMS Se — SIWYSMIS SI ISM SI WIla—� 90 00 70 w 50 10 30 20 10 0 MISS MIS SE Sal e� alga- s SW I— P11S1— Mast S ellMESS SI s —SSE SS SE WM= • I I I MaNII S SeS EP EIS MS SS a-A—S-e Wes gra— ale EMS — �- - —Seaga ----- — Sa—Iiinn SI MB -- SS. _ a Ms —e— —a -a- —a— —a•a_StsllaMS SI S i_ -� VAS ---e-- -a— — a- alp — Is g— —I—lag ISI El a'S SI __-SI WS SI S—S ea PS a S SI a IS —n—se- sal MI— --- WAS S Ise -,e1 MI Ws El S EA -aa m-----lr_ SES —r—a-- es -rte ;fie SSW= —„-tea---M r gra--e------- tea_ J� SIAM r--elISaII Pa -- — - �r swim! SI AEI --rrr ANS ---- --- —I - —armEst — VMS S SI MI - SI saws SI lei CLAY 70 SILT FINE Sino GRAVEL 61 % LIQUID LIMIT % SAMPLE OF: Slightly Silty Sandy Gravel 107 0760 H Hepworth—Pawlak Geatechnieol MEDIUM 1 COARSE s -ems —ems-- a----� -- 90 80 70 so 50 40 30 20 10 0 4 75 9.512 519 0 37 5 76.2 12152 203 FOIE I comsE comas SAND 31 % SILT AND CLAY 8 % PLASTICITY INDEX % FROM: Boring 2 at 5 and 10 Feet, Combined GRADATION TEST RESULTS `CENT PA kC Figure 4