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HomeMy WebLinkAboutSoils ReportHEPWORTH-PAWLAK GEOTECHNICAL March 6, 2015 Crawford Design Build, LLC Attn: Brad Crawford P.O. Box 1236 Carbondale, Colorado 81623 (craw rorI(IesiI)Clllciul c41nicast.net) Elc:p v rth-I':nrlak Cotec nical, Inc. 5020 County IL I:n.1 154 C�Irn+nin�f Sr s Colibrido 81601 Phone: 970-945-7965 Fax: 970-945-8454 etu;ii l: lirgeu+�hpgcu»ech.c4E» Job No.115 035A Subject: Subsoil Study for Foundation Design and Percolation Test, Proposed Residence, Lot 18, Callicotte Ranch, 0110 Sopris Lane, Garfield County, Colorado Dear Mr. Crawford: As requested, Hepworth-Pawlak Geotechnical, Inc. performed a subsoil study and percolation test for foundation and septic disposal designs at the subject site. The study was conducted in accordance with our professional services agreement for geotechnical engineering services to you dated February 4, 2015. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Hepworth-Pawlak Geotechnical, Inc. previously performed a preliminary geotechnical study for Callicotte Ranch and reported our findings April 19, 2002, Job Number 101 821. Proposed Construction: The proposed residence will be one story wood frame construction above a crawlspace and with an attached garage. The residence will located in the area of the center post shown on Figure 1. Garage floor will be slab -on -grade. Cut depths are expected to range between about 3 to 4 feet. Foundation loadings for this type of construction are assumed to be relatively light and typical of the proposed type of construction. The septic disposal system is proposed to be located downhill and south of the residence. If building conditions or foundation Ioadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The vacant lot was covered in patchy snow. Vegetation consists of grass and weeds in the building area with a pinion and juniper forest east and north of the Parker 303-841-7119 e Colorado Springs 719-633-5562 • Silveratorne 970-4681989 building area. The ground surface is relatively flat with a slight slope down to the southwest. A shallow abandoned irrigation ditch crosses the upper part of the building area. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits in the building area and one profile pit in the septic disposal area at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about one foot of topsoil, consist of 2 feet of stiff sandy clay overlying basalt gravel with cobbles and silty sandy clay. Results of swell -consolidation testing performed on relatively undisturbed samples of the sandy clay, presented on Figures 3 and 4, indicate low compressibility under existing moisture conditions and light loading and a moderate collapse potential (settlement under constant load) when wetted. The samples were highly compressible under additional load after wetting. Results of a gradation analysis performed on samples of gravel and clay (minus 5 inch fraction) obtained from the site are presented on Figure 5. The laboratory test results are summarized in Table I. No free water was observed in the pits at the time of excavation and the soils were slightly moist to moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psf for support of the proposed residence. The soils tend to compress after wetting and there could be some post -construction foundation settlement if the bearing soils become wet. Care should be taken to reduce the risk of wetting as described in the Surface Drainage section of this report. Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns. Loose and disturbed soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported Iength of at least 12 feet. Foundation walls acting as retaining structures should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill. 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, 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 Job No.l 15 035A -3 - 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 basement level slabs to facilitate drainage. This material should consist of minus 2 inch aggregate with less than 50% passing 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 or a suitable imported granular material devoid of vegetation, topsoil and oversized rock. Underdrain System: Although free water was not encountered during our exploration, it has been our experience in mountainous areas 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 crawlspace 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 1% to a suitable gravity outlet. Free -draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, Iess 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. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence 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. Free -draining wall backfill should be capped with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. 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 pavement and Job No. ! I5 035A -4 - walkway areas. A swale may be needed uphill to direct surface runoff around the residence. 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 10 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the building caused by irrigation. Percolation Testing: A profile pit and three percolation test holes were excavated on January 12, 2015 at the locations shown on Figure 1. The subsoils exposed in the Profile Pit below about 1 /2 feet of topsoil consist 1 feet of stiff sandy clay overlying sandy gravel and clay with cobbles to the bottom pit depth of 8'/2 feet. The results of a gradation analysis performed on a sample of clayey sand and silt (minus 3/8 inch fraction) obtained from the site are presented on Figure 6. The sample tested has an USDA Soil Texture Classification of Loam. No free water or evidence of a seasonal perched water table was observed in the pit and the soils were slightly moist to moist. Percolation test holes were hand dug and soaked with water on January 12, 2015. Percolation testing was conducted on January 13, 2015, by a representative of Hepworth - Pawlak Geotechnical, Inc. The percolation rates varied from 20 minutes per inch to 30 minutes per inch with an average of 27 minutes per inch. The percolation test results are summarized on Table 1. Based on the subsurface conditions encountered and the percolation test results, the tested area should be suitable for an on-site infiltration waste disposal system. 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 pits excavated 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 pits 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 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 Job No.115 035A -5 - 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. If you have any questions or if we may be of further assistance, please let us know. Respectfully Submitted, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Louis E. Eller Reviewed by: Daniel E. Hardin, P.E.I LEE/ksw ' "p' JNAL - ,� rtayou►A attachments Figure I — Location of Exploratory Pits and Percolation Test Holes Figure 2 — Logs of Exploratory Pits Figures 3 and 4 - Swell -Consolidation Test Results Figure 5 — Gradation Test Results Figure 6 - USDA Gradation Test Results Table 1 — Summary of Laboratory Testing Table 2 — Percolation Test Results Job No.115 035A APPROXIMATE SCALE 1"=60' 115 035A GP i LP A li• • P p ■PIT PIT 2 P1p PROFILE •2 \ P3• o CENTER POST • • • • \ LOT 18 • • PIT 1 • • • \ / \ / \\ / • \ / • \ / / LOT 17 \ / / \ \ / *� \ ,/ Ni • H Hepworth—Pawlok Geotechnleal LOCATION OF EXPLORATORY PITS AND PERCOLATION TEST HOLES Figure 1 0 5 10 LEGEND: b1 NOTES: PIT 1 • WC=8 7 DD -80 -200=87 PIT 2 /9 ,44 WC -9,9 DD -86 - +4=54 - -200=40 TOPSOIL; organic sandy silt and clay, firm, moist, dark brown. PROFILE PIT ASO ;.:07 GRAVEL=4 — — SAND=31 SILT=47 CLAY=18 — +4=26 — -200=56 0 5 10 CLAY (CL); silty, sandy, slightly gravelly, stiff, moist, reddish brown to brown, porous, medium plasticity. BASALT GRAVEL AND CLAY (GC -CL); silty, sandy, scattered cobbles, very stiff/medium dense, moist, brown to light brown, calcareous with depth. 2" Diameter hand driven liner sample. Disturbed bulk sample. 1. Exploratory pits were excavated on January 12, 2015 with a backhoe. 2. Locations of exploratory pits were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory pits were not measured and the logs of exploratory pits are drawn to depth. 4. The exploratory pit 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 pit logs represent the approximate boundaries between material types and transitions may be gradual. 6. No free water was encountered in the pits at the time of excavating. Fluctuation in water level may occur with time. 7. Laboratory Testing Results: WC = Water Content (%) DO = Dry Density (pcf) +4 = Percent retained on the No. 4 sieve -200 = Percent passing No. 200 sieve 115 035A H Hepworth—Pawiak Geotechnical Gravel = Percent retained on No. 10 Sieve Sand = Percent passing No. 10 sieve and retained on No. 325 sieve Silt = Percent passing No. 325 sieve to particle size .002mm Clay = Percent smaller then particle size .002mm LOGS OF EXPLORATORY PITS Figure 2 Compression 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Moisture Content = 8.7 percent Dry Density = 80 pcf Sample of: Sandy Silty Clay From: Pit 1 at 1 1/2 Feet 0.1 115 035A 1.0 IH Hepworth—Pawlok Geotechnlcal 10 APPUED PRESSURE - Icsf Compression upon wetting SWELL -CONSOLIDATION TEST RESULTS 100 Figure 3 Compression % 10 11 12 13 14 15 Moisture Content = 9.9 percent Dry Density = 86 pcf Sample of: Sandy Silty Clay From: Pit 2 at 3 1/2 Feet 0 Compression upon ,_ 0.1 1.0 115 035A H Hepworth -1'0140k Geotechnical 10 APPLIED PRESSURE - kst SWELL -CONSOLIDATION TEST RESULTS 100 Figure 4 a a►Ii:Mr_rrZI:. 24 HR 7NA 45 MIN 15 MIN. 60MIN19MIN 4 MIN 1 MIN 0 HYDROMETER ANALYSIS TIME READINGS I 10 20 30 40 50 60 70 80 90 100 al Ma all Al•a a llia; aar i aaara� 1 Ila rear, •ria aa= aaa_ arm aaaara rrrl raa_ aa= NiNa l _l SIEVE ANALYSIS U.S STANDARD SERIES 1 CLEAR SQUARE OPENINGS #200 #100 #50 #30 #16 #8 #4 3/8' 3/4' 1 1/2' 3' 5'6' 8' NMI alar. •w_ Mary a� warm -=ter I=� as _ rr_ a_a _ l r r_ aa_ # a_a aaa 1=arra as NMIaa� a_ira11 aallasalla — ra_i iaa a=anal as =a III _aa era 1•11 ar amara —real aw•a i _rraa�_ ear ararra i aai as=— i aaaaa=wi i r_. aaaara. agar aaa•rr rr. Mot a_. alrr raaaaraar r ar w ear = a =arra a_#—aaa=aaa= a _ raa=#a IN a==— aa_rr_ia— =rill aaaa—i•aw=aar 1_arr= __—i al==raa a_ �aar� Ma a mall err, aarar = ear #aa _INNLear =arra _r;1aa_ aa_ a. _ all Il w aa. mar a arra Man rare, _l Nal arra_ ear INNaaaa raa rarer rarer=ate armor_ S —aaaa1aa= i asaaa anal" IN as_i iaaawlar_ aara=aa_i r-^ aa_aaa�aaaMI ear a •r_ err �__. arab i—ar -- •aa_# war a= as raraa_i arae I =arae P•l_aa_a # r aa_—#=ar=aalal aar=aa� =ala .001 .002 005 009 CLAY 70 SLT 019 037 071 150 300 000 1 10 236 DIAMETER OF PARTICLES IN MILLIMETERS FINE SAM MEOW ICOAHSE �_ wrr= =awr w agar 1.75 9.51? 19.0 37.5 762 152 203 GRAVEL FINE I COARSE 127 COBBLES GRAVEL 54 % LIQUID LIMIT % SAMPLE OF: Slightly Sandy Gravel and Clay SAND 6 % SILT AND CLAY 40 % PLASTICITY INDEX % FROM: Pit 2 at 4 to 5 Feet HYDROMETER ANALYSIS E 24 R 7 HR TIME READINGS 405 IN. 15 MIN. 60MIN19MIN.4 MIN 1 MIN. #200 10 20 30 40 50 60 70 80 90 aa_lasiaawr 1•1111 aaaa�r r� ear aaaa•a aaa=�aar aa_„a_ arra aa_ �lrr SIEVE ANALYSIS U.S STANDARD SERIES 1 CLEAR SQUARE OPENINGS #100 #50 #30 #16 #B #4 3/8' 3/4' 11/2' 3' 5'6' 8' #ir��iar� ear aaa� ear_ ate■ aa_r=a_ raa r—aaa�r� rear /arra Mat ar= aataal /=1111 aa_ r+rear rear raa .=INN =la _r. aa_ia awIMM aINN MM. ls aElla aa_iwar waw �lri—__�a�> �w� p_ -- - _ •aa • .rarer ear a ^a= as _ ate. air - I= Mara # ear 1.I_. ate_ __ MI •a_ aaa•w ear w — __ri.#_ =-1 . •-ear=•te MI M,-• a�aa_#11=� ,arra_PE aa•r.=� as_ —_Mail ria—ar_aMa. r<alll= aa_ p r_ a _l rarer rte_-__ err MINIM aa� arra #aarw— aaa_lli -- rw MEE_ a._ •_=raw= rarer ear w- _ war MI— _ a r, aa�=real waalll 1== =MN alar. # i a MN r._M• aar=aa� /ta=re= err—a_ _-- =a_ aa_aaa�l ear w- 100-� .001 002 rr_i a_i aa�=aarr aa_ala =raa arr—i wr_ IN w— ai arafln alii=�=MINIM aa� 100 90 B0 U 70 r�r^ CO 60 eL so Z W U /Q a_ 30 20 10 0 100 90 80 70 Z co in 60 Q � 1-- 50ZU U 40 W rZ 30 20 10 0 005 009 019 037 .074 150 300 .600 1.18 2 36 4 75 9 512,519 0 37 5 76.2 12]752 203 DIAMETER OF PARTICLES IN MILLIMETERS CLAY TO 50.7 GRAVEL 26 % LIQUID LIMIT % SAMPLE OF: Sandy Clay with Gravel SAi0 GRAVEL j FINE I MEONM I COARSE FINE 1 COARSE ] COBBLES SAND 18 % SILT AND CLAY 56 % PLASTICITY INDEX % FROM: Profile Pit at 5 to 5 y Feet 115 035A 1"1 Hepworth—Pawlak Gaotechn1cal GRADATION TEST RESULTS I Figure 5 CENT RETAIN_ i, I HYDROMETER ANALYSIS $LEVE ANALYSIS I 24 7HR TIME READINGS 1 MINU 5 STANDARD SERIES ICLEAR SQUARE OPENINGS 0 45 MIN 15 MIN. 60MIN19MIN.4 MiN. #325 #140 #60 #35 #18 #10 #4 318' 314' 1 112' 3' 5'6' 8' 100 Mintnngliii ii iifai aai♦ iii i! ri EMI iiWin i•i iirIn!..---.11 it --baa lin i i.1 i•li i aaaaa_ii iiiaii' :i r iil--iia- i ii iiii iil lI l tea—f iii i it ii ce—iia-ate — Iiii Mi -ii f if_ A in i♦ii Mini Inim a ai i inn a a a a aiiila-� i��iaa�-. �— — i aaii i—i-- = lilt 10 20 30 40 50 60 70 80 90 100 i i aaYWni — i i -� aaa�— a i_ i--- - ii—Inn �-it - ii-ils—a inn mai a-- ii EMI iii -- Ann i iiii It In aaaa--ii! iii IM /1i —iii -aa -i — --i —i i i-- — i —ii-aai.ii ii—iisil — i — 'ii ia-aaaa- aaaA-i —i il i-aai... i -1ME!ir—i i t,-. iii iiia-•-M`iiii -1' mil lii —ii - ai i - ii -,li•�i ii -Iiti i_- 1ii1ii ii -Ii naafi X1111 11ia -i• i li Ml •—i il•/ -fir —iaai• ani ii —i--a-1 -i!a— i• — — it ifails �a i iiil PIN ii - lint la--fi iii ME i tea-- — a-ni isi —i — I MIN `i—aa iWNW -i in ia--i P= MOW i— —ice a -a-i nit __., 1i -iai a—aa ii--- ia-ate—i MIM iMit ia— i�— n. - M ,A M•111=Mi.Millt AM V.= —iii in—Mr �-�--nl iii —I as NI ill •Int • i i i-i•_.ai i -- i-rjii— i ar,- lar as ii♦•aii— i—.— i a air ii An iiiila i---ill-iii iii inn i —Mai irim iiMil Al it+i• ii ■=P" M -fiiil !�l—iiii ill-l--i--i1 iii — il-- aaf i aaaa� ria�l— i aa --- ii ii ail ii ii M� �i illi ii a -=it i• i i W= itis Em s i lir Min —iiMM. i —ii-- iiii d--ii-- -iia- —aa—aalY-i --aa-- ii--- ii--i ii =WI -- i--- i i --- i--- ii--- --- -- --- i--- ii-- `--- i--- i--i ii-iW i--- iii— ii--- ii-- ii --i iii -- ii --i iii— iiMMI 1IMI ii --i int ii--- iiii-- -�-iii—-i iaaar ii i a— i-- Mil iiiill --- ii•iiii--i i i ii--- iAMnt-- ---i p lii-- Mai — -i ii--- iiii--- =in iiii--- li iai--ate ii -i i --Mi---` i�if i in i--- ia—i-- i anal• i a— i li[--- i� ii a—i--- iiii—ai ii—s— iiia---- �-iii^---- #ia..1—ire --- m,.= N. ---- -- --ii ii i--- iiii--- -iiii-- iiiii-- iiaaa-i-1— IlMinniiia—i-i i iii MIME -i -i ai i -----anal — iiiMaim -- ia---- iriia—ii-- iiii--- litniiiiii-- iiain-- iiii--- iil-i-- ii--- ii--ate ii—a— i i--- iiii--i iii--- iii--i iii—ai -i iii--- ii --- iii—a-M n iii— iii—a— iii—ai ill iiia— i--- -- i -i i--- il--Si— In i-- i--- i--- i--- i--- ii--- ii �in it in ii�ai-� iiii iini- ail ii a—i 001 .002 005 009 019 ai ani i illr i is Ii1 --i a—ii ani 045 106 025 500 1.00 2 00 DIAMETER OF PARTICLES IN MI:,LiMETERS i 90 80 70 60 50 40 30 20 10 0 4 75 9 5 19 0 37.5 76 2 152 203 ISAND GRAVEL v. FLNE 1 FINE r MEOW (COARSE 11 COARSE1 SMALL 1 MEOnJA 1 LARGE GRAVEL 4 SAND 31 ':•a USDA SOIL TYPE Loam SILT 47 % CLAY 18 % FROM: Profile Pit at 2 to 2 y Feet `` RCENT PASS r, 115 035A M Hepworth—Pay/10k Geotechnicol USDA GRADATION TEST RESULTS Figure 6 Job No. 115 035A Ci VI z J Q W _V a: 2 1 w u1— w >- 1- 0c 00 Lu 1- 0 < cc 3m5 1— O F 0= cc O < a 2 W = = V1 W yd _ 0 N • W W _ Z1D Z O z O a u, j 0i'n F zW tam cc u- gip+ w a Q N a N 00 0 In 1/40 1/40 1/40 00 J w _ w 0 00 00 r 00 W 0 0 1- a 111 47 0 a HOLE NO. P1 P2 P3 HOLE DEPTH (INCHES) 32 33 36 HEPWORTH-PAWLAK GEOTECHNICAL, INC. TABLE 2 PERCOLATION TEST RESULTS LENGTH OF INTERVAL (MIN) 15 Water added Water added 15 Water added Water added 15 Water added WATER DEPTH AT START OF INTERVAL (INCHES) WATER DEPTH AT END OF INTERVAL (INCHES) DROP IN WATER LEVEL (INCHES) 6 1/2 5 1 1/2 6 1/2 5 1 1/2 6 4 3/4 11/4 4 3/4 3 1/2 1 1/4 3 1/2 2 3/4 3/4 2 3/4 2 3/4 5 1/2 4 11/2 5 4 1/4 3/4 5 1/4 4 1 1/4 4 3 1/2 1/2 3 1/2 3 1/2 3 2 1/2 1/2 5 1/2 4 3/4 3/4 5 1/2 5 1/2 5 4 1/4 3/4 4 1/4 3 3/4 1/2 3 3/4 31/4 1/2 3 1/4 2 3/4 1/2 JOB NO. 115 035A AVERAGE PERCOLATION RATE (MIN./INCH) 20/1 30/1 30/1 Note: Percolation test holes were hand dug in the bottom of backhoe pits and soaked on February 4, 2015. Percolation tests were conducted on February 5, 2015. The average percolation rates were based on the last two readings of each test. The test holes were protected from freezing with foam insulation.