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Home My WebLink AboutSoils ReportHEPWORTH-PAWLAK GEOTECHNICAL 1Ivhuurrh 1'.I 11i (k F1e ltrl> ,1I, Iu4. 5020 r't Ru.1,1 15-1 I i1vrn1 kI Brun: t:u1,•r.nf,i tilfl�l r11ori, 970-'14i 0:,!..1 11 -"Ax q70 -94-1-84i 1 i' n III #y _rnirltl' rri1k..0111 SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED MCLELLAND RESIDENCE LOT 50, FIRST EAGLES POINT 79 EAGLE RIDGE DRIVE BATTLEMENT MESA, COLORADO JOB NO. 114 526A DECEMBER 22, 2014 PREPARED FOR: GIARD HOMES ATTN: ROGER GIARD 1431 AIRPORT ROAD RIFLE, COLORADO 81650 (retard n rof.net) .-irk r 303-,M41-7119 • l=.t}It,r,k111Springs 71t)-633.-55(2 * Sil‘crrhtirn 97(46.S -19S9 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY ............. ........ .... ............ ..... ....................... .....,, - 1 - PROPOSED CONSTRUCTION -1 - SITECONDITIONS............. .. ... ............. ........ .................. .............. ....,........................ - 2 - } IF,LD EXPLORATION - 2 - SUBSURFACE CONDITIONS ..�„ - 2 - FOUNDATION BEARING CONDITIONS •*.,,.,.m - 3 - DESIGN RECOMMENDATIONS - 4 - FOUNDATIONS - 4 FLOOR SLABS ,................ ........ -5- SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 - LEGEND AND NOTES FIGURE 4 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Job No. 114 526A Ggstech PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 50, First Eagles Point Subdivision, with a physical address of 79 Eagle Ridge Drive, Battlement Mesa, 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 Giard Homes, dated November 26, 2014. A field exploration program consisting of an exploratory boring 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 1 story structure with a structural floor over a crawlspace in the living areas and an attached garage with a slab -on -grade floor. Grading for the structure is assumed to be relatively minor with cut and fill depths between about 2 to 4 feet. 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. Job No. 114 526A -2 - SITE CONDITIONS The site is currently an undeveloped residential lot on the northwest corner of Eagle Ridge Drive and Eagle Court in the First Eagles Point Subdivision. The lot had been graded relatively flat and currently has a sparse coverage of grass and weeds. A mix of undeveloped and developed lots surrounded the subject property with moderately sized wood framed residential structures on the developed lots. Numerous medium to large basalt boulders were observed to have been used as landscape material on the developed lots. FIELD EXPLORATION The field exploration for the project was conducted on December 8, 2014. One exploratory boring was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by a truck -mounted CME -45B drill rig. The boring was logged by a representative of Hepworth-Pawlak Geotechnical, Inc. 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 Log of Exploratory Boring, Figure 2. A disturbed sample of the near surface soils was obtained from a depth of about 1 foot below the surface. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about 2 feet of sandy silt and clay overlying clayey gravel and Job No. 114 526A -3 - basalt cobbles and boulders with a fine-grained soil matrix. 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. The boring location was moved four times in an attempt to achieve penetration of the basalt cobble and boulder stratum without success. Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of gradation analyses performed on a small diameter drive sample (minus 11/4 inch fraction) of the coarse granular subsoils are shown on Figure 4. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist to moist. FOUNDATION BEARING CONDITIONS The natural basalt cobble/boulder soils encountered below a depth of about 2 feet in our exploratory boring should be suitable for support of the proposed residence on shallow spread footings with some risk of movement. The depth and consistency of the basalt cobble/boulder layer may vary across the building footprint. Areas of fine-grained soils may be encountered during foundation excavation and should be evaluated by the geotechnical engineer for bearing suitability at the time of construction. Boulder removal during foundation excavation may leave substantial voids in foundation areas. Voids created by boulder removal may be filled with lean mix "flow fill" concrete, properly compacted structural backfill or structural concrete. Structural backfill in foundation areas should consist of an imported granular material such as CDOT Class 6 base course, placed in maximum 8 inch loose lifts and compacted to 98 percent of the standard Proctor value for the material at a moisture content near optimum. Prior to placement of structural fill the subgrade soils in foundation areas should be moisture conditioned and compacted. A representative of the geotechnical engineer should observe the foundation excavation for bearing conditions prior to the placement of structural fill or concrete. Job No. 114 526A eggetech -4 - DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural cobble/boulder soils. The design and construction criteria presented below should be observed for a spread footing foundation system. I) Footings placed on the undisturbed natural basalt cobble/boulder soils should be designed for an allowable bearing pressure of 2,500 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 12 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. Foundation wall backfill can consist of the on-site soils or imported granular soil and should be placed in maximum 8 inch loose lifts and be compacted to a minimum of 95 percent of the standard Proctor value for the material at a moisture content near optimum. An underdrain should not be needed around foundation walls if Job No. 114 526A Gatech -5 - foundation wall backfill is properly compacted and the recommendations in the Surface Drainage section of this report are %fowed. 5) The upper silt and clay soils and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural cobble/boulder soils. The exposed soils in footing area should then be moistened and compacted. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to assess the bearing conditions. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded garage slab -on -grade construction. 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. 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: 3) 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 Job No. 114 526A -6 - 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 m 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. 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 boring drilled at the location 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 boring 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 ofour 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 Job No. 114 526A "` Giggled, -7 - 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 ofstructural fill by a representative ofthe geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLAK GEOTECHNICAL, INC. James A. Parker, P.E., P.G. Reviewed by: Steven L. Pawlak, P.E. JAPrIjf cc: Westar Engineering - Stephen Kesler (westar a,ro£net) Job No. 114 526A Gegtech APPROXIMATE SCALE 1"=30' LOT 49 LOT 51 A / \ / \ // LOT 50 L EAGLE COURT • s. EAGLE RIDGE DRIVE J 114 526A HtchHC,o uKeC►L LOCATION OF EXPLORATORY BORING FIGURE 1 I- LL.. G a co in 0 5 BORING 1 -, WC=13.5 .J ' -200=92 W125 12 l�;d, C�• 27/6,20/1 {' �■ WC=9.3 +4=20 -200=57 0 5 10 10 114 526A NOTE: Explanation of symbols is shown on Figure 3. HLPWORTH•PAWLAK GEOTECHNICAL LOG OF EXPLORATORY BORING FIGURE 2 LEGEND: 1 L b SILT AND CLAY (ML -CL); sandy, with gravel and occasional cobbles, soft to stiff, slightly moist to moist, brown. COBBLES AND BOULDERS (GC); with gravel and sandy clay matrix, medium dense to dense, slightly moist to moist, brown, basalt 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 -1586. Drive sample blow count; indicates that 25 blows of a 140 pound hammer falling 30 inches were 25/2 required to drive the California or SPT sampler 2 inches. T Practical drilling refusal. NOTES: 1 The exploratory boring was drilled on December 8, 2014 with a 4 -inch diameter continuous flight power auger. 2. Location of the exploratory boring was measured approximately by pacing from features shown on the site plan provided. 3. The exploratory boring elevation was not measured and the log of exploratory boring is drawn to depth. 4. The exploratory boring location and elevation should be considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the exploratory boring log represent the approximate boundaries between material types and transitions may be gradual. 6. No free water was encountered in the boring at the time of drilling. Fluctuation in water level may occur with time. 7. Laboratory Testing Results: WC = Water Content (%) +4 = Percent retained on the No. 4 sieve -200 = Percent passing No. 200 sieve 114 526A H HEPWORTH-PAwwc GEO1ECHN11cA1. LEGEND AND NOTES FIGURE 3 1, HYDROMETER ANALYSIS+ SIEVE ANALYSIS I 2pqq wp TIME READINGS U.S. STANDARD SERIES 1 CLEAR SQUARE OPENINGS 0 45 a.15 MIN. 60MINI9MIN.4 MIN. 1 MIN. #200 #100 #50 #30 #16 #8 #4 3/8' 3/4' 1 1/2' 3' 56' 8` 100 =a�.l..—aalaaaa aaaaila-iia 10 20 30 40 50 6o 70 80 90 100 .001 .002 .005 .009 .019 .037 .074 .150 .300 .600 1.18 2.36 -ami—i anal= �a-M-arm-a a�a-mama a- �a'aaa�a— a= Maa�ailaaa -i i`ill gamma a�-Mamma aaaal�=a--a--mama-a--aaaal___ as a+ Mamma i a /aaalaaa — aa.aM a-- arai —aaaa a�aa, _Ja-aMaa —Mama —mama �Mal MI Mai -+mar-"F �r �aaal �— aa/a. a .mai ami —aaa— wawa alaimalala �� Tama maia—a aaa aaa=a— aaa�_aaaa-= mama �laai rsaaa as=lama—aas� a halal a—aa allai �-a�� a�—a-�aaaMaaMat= as aaa�aa`i aWAI.—aaaa��aaMalla Mr-ammo—�aaaa-aala- MaawAMma a-aaaas aaMMama=�Waallr l =alaa- ir��-waa as a-arae-iaa-=Ma a_aaMaa-aaa a=Mamma:_Mama a ma aaa mama• -,a ms aa� Maia ■iia aaaRaRaal lm lama =Ma ala. Mama^aaa@aa m Mama Mai Mama.—.Ra aaaa�r aa�l�llla>•aaa'� a� Mama `a' —alaraaaa�iaaalaaaaalaaaal Mama aaam. aaa ai am Mama—Mama—Maas aa-aaaaaeai aa-aaalA[ma: ll -aa lMama a --ll aaaa11aaa-as—aiaaa alM'Alalll aaalaai a—aa—aaM Ma- a— _a-llaal,-r iaaal tam —r _•—Mlalla—Mai —Waal aaa�aa—yam—i alaraaa` aaaa---- ----aaalll-a-ia a— a---- m aa-amara-aa iimaamial. Mama =�aaaaMlraa�a Para a--a�aia��aaa•IMIaa—ai ila ami aaaaa1aal Mama Mamma— +aa saaaa fi > r— aaaaaai ar as-im aaaaNa a"rmpaIN a=Mama aeras—aa i a in saw lama.-Illliaai -- --a__-- Mamma ams a--- illi —aaa� a ____Mama =lam -aa� a a-aaaa a aaaaiaaa -a—aa-- =iaa---aa aala-- a=�aa-aaaaa Mamma -aa aaaaaaa —mama a aaarrla--a Mama -a aalala� Cama—_a— as -moi sera -aha -a ami --mom aa—aaaaa -aa am. CaCC a -ma aa -ii �aaa-ala aa. aa, a•a-allaalai — Mama 1= aa-.IY.�as Mamma aaai err --Mamma laaaaala M�� alamma Baa -aa Mama aaa-,Mamma aaaaarsa_ aai. a =allp a ---aa aaa-m aaasaa—aa as -rams i alma alma aa- alma aaa a=aaa--=aa-aa 1.1 aa—wla a— Mama --aa as a aaa a=aaaasr��a .111 ma- Mala = aallaaaa.a— alaa Mamma a—mi i �aaa� i Mama Mali as --Ills Mala. amara-aaaaaaa— a Ma+a� Mai as arm Mia Mama--Illlaai�aiaia=aa-, Mai s M a.= Mai DIAMETER OF PARTICLES IN MILLIMETERS Mara aa aIm a_a aaa alaaa�alaa-- 4.75 9.5 19.0 37.5 12.5 76.2 152 203 CCAYTO SO GRAVEL 20 % Flt+E 1 Mid I COARSE 1 Fig C 1 Olga I mean LIQUID LIMIT % SAND 23 % SILT AND CLAY 57 % PLASTICITY INDEX % SAMPLE OF: Gravelly Sandy Clay (Matrix) PROM: Boring 1 at 5 Feet 90 60 70 60 50 40 30 20 10 0 114 526A HEPWORTFFPAWf..AK GBOTECHNICAL GRADATION TEST RESULTS FIGURE 4 Job No. 114 526A { Z a w c� IX co r w v a re w 0 5w -1O m a~J = o } rto a w g Z N UNCONFINED COMPRESSIVE STRENGTH SOIL TYPE (PSF) Slightly Sandy Clay Gravelly Sandy Clay (Matrix) it RG LIMB'S PLASTIC INDEX w a O F- 3 • PERCENT PASSING NO. 200 SIEVE N I o a a z .� a o N NATURAL DRY DENSITY ipcfl 1 F 5- zz0 � Mt-1V7E a; 11 SAMPLE LOCATION Z z E 0 I 1.4 I