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Home My WebLink AboutObservation of Excavation 07.25.18Geotechnlcal Engineering I Englneering Geology Materiala TEsting I Environmental H.PVKUMAR 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (920) 94S-798S Far (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Denver (HQ), Parke¡ Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado July 25,2018 Mike Brown I262Caunty Road 112 Carbondale, Colorado 81623 Downtown.brown @ mac.com Project No. l8-7-141 Subject:Observation of Excavated Pits, Proposed Shop, 1262County Road 112, Garfield County, Colorado Dear Mike: As requested, a representative of H-P/Kumar observed the excavation at the subject site on July 18, 2018 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 services were performed in accordance with our agreement for professional engineering services to you, dated February 2,2018. The proposed shop will be a metal frame/metal skin building with spread footing foundation and slab-on-grade floor. At the time of our visit to the site, four exploratory pits had been excavated near the four corners of the proposed shop location from 6 to \Vz feet below the adjacent ground surface. The soils exposedinthebottomof theexcavation,belowabout l footof topsoil,consistof 3to íVzfeetof sandy clay overlying sand and gravel with cobbles. Results of swell-consolidation testing performed on samples taken from the site, shown on Figures 2 ro 4, indicate the clay soils have low to moderate compressibility under conditions of loading and wetting. The results of a gradation analysis performed on a sample of sand and gravel (minus 3 inch fraction) obtained from the site is presented on Figure 5. No free water was sncountered in the excavation and the soils were slightly moist to moist. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 2,000 psf should be adequate for support of the proposed shop. The exposed soils tend to compress when wetted and there could be some post-construction settlement of the foundation if the bearing soils become wet. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be removed and the bearing level extended down to the undisturbed naturâl soils. Exterior footings should be provided with adequate soil cover above their bearing elevations for frost protection. 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. Mike Brown July 25, 2018 Page2 Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site soil as backfill. A perimeter foundation drain should be provided to prevent temporary buildup of hydrostatic pressure behind retaining walls but should not be needed for the proposed slab-on-grade floor level near exterior grade. Structural fill placed within floor slab areas can consist of the on-site soils or a suitable imported gravel compacted to at least 95Vo of standard Proctor density at a rnoisture content near optimum. Backfill placed around the structure should be compacted and the surface graded to prevent ponding within at least l0 feet of the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads should not be located within 10 feet of the foundation. The recommendations submitted in this letter are based on our observation of the soils exposed within the excavated pits. This study is based on the assumption that soils beneath the foıtings have equal or better support than those exposed. The risk of foundation movement may be greater than indicated in this report because ofpossible variations in the suhsurface conditions. 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 James H. Parsons, E.I. Reviewed by: Daniel E. Hardin, JHPlkac attachments Figure - Logs of Exploratory Pits Figure 2to 4 - Swell-Consolirlation Test Results Figure 5 - Gradation Test Results Table 1 - Summary of Laboratory Test Results Project No. 18-7-141 e t E PIT 1 11.100' PIT 2 81.94.5' PII 3 EL. 97.5 Prï 4 EL. 1 00' 0 0 FLJ Lrll,! I-Fo- LTJâ WC=8.8 DD=89 WC=1 1.3 DD=BZ Þ-r¡JtJ l! IIF o_ LIô 5 -l WC= 1 2.5 -r *4=65 _1nn-tr NP 5 WC= 13.5 DD=82 I0 10 LEGEND TOPS0IL; SANDY cLAY, ORGANIcS (ROOTS), ME0IUM STIFF, SLIGHTLY MOtST, BROWN. CLAY (CL); SANDY TO VERY SANÐY, MEDIUM STIFF, SLIGHTLY MOIST, CALCAREOUS WITH DEPÏH, BROWN 10 TAN. GRAVEL AND SAND (CT-SN); COBSLES, SCAITERED BOULDERS, CALCAREoUS, SASALT GRAVEL, WHITE TAN, SLIGHTLY MOIST. F HAND DRIVEN LINER SAMPLE l.' D¡STURBED BULK SAMPLE NOTES .I. THE EXPLORATORY PITS WERE EXCAVATEÐ WITH A BACKHOE ON JULY 15,2018 2. THE EXPLORATORY P|TS WERT LOCATED BY THE CLIENT. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE ESTIMATED AND REFER TO THE PIT 1 AS A IOO, BËNCHMARK. 4. ÏHE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDEREO ACCURA]E ONLY TO THE DEGREI IMPLIED BY THE METHOD UsEO. 5. THE LINES BETWEEN MATER'ALS SHOWN ON THT EXPLORÄTORY P LOGS REPRËSTNT THE APPROXIMATE BOUNDARIES BETWEEN MAIERIAL TYPES AND THE TRANSITIONS MAY gE CRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTTRED IN THE PITS AT THE TIME OF DIGGING. PITS WERE BACKFILLEÐ SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); f]D = DRY I];NSITY (PCT) (ASTM D ?216); +4 = PËRCENTAGE RETAINEO ON NO. 4 SIEVE (ASTM D _ZOQ = PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D NP = NON-PLÀSTIC (ASTM Ð 4518). a22); 1 1 a0); 18-7 -1 41 H-PryKUMAR LOGS OF TXPLORATORY PITS Fí9. 1 SAMPLE OF: Scndy Cloy FROM:8oring2u^7.5' WC = 13.5 %, D0 = 82 pc{ ADDITIONAL COMPRISSION UNDIR CCINSTANT PRESSURT DUE TO WETTING I | -"/ \ I ) S*.Ìl JJ L¡l U1 I zotr ff: tnz.a 0 _t -2 _Ì *4 -J -6 ÂPPL'€D PRISS - KSF 10 100 18-7 -1 41 H.PVKUMAR SWELL-CONSOLIDATION TTST RTSULTS Tí9. 2 ¡ 6 :I Ê E SÀMPLE OF: tloyey Scnd FROM:Boring3@3.5' WC = 8.8 %, ÐD = 89 pcf AÛDITIONAL COMPRESSIÕN UNDTR CONSTANT PRTSSURT DUT TO WËTTINö ) \ I \ \) lhcs. t¿¡l r.r¡¡t! ûqpìy a¡ly lE t¡! !!nrp¡c! lé!t¡d. th. t!!!ùq .troi .hall ro! !! rêpmdlcld, ar.lpl in l!,1, rilhou! lhc dllen opp'ð!01 ot(!no¡ ¡nd &3ocìol.s, l¡c- slcli :oôloi;úolio¡ llii.g pcd.m.d in cccôrdô¡.. sÌlh ASru 0-4548. iljl il )J ttJ3 ¡ z"(}ç : v7z. (-) at *2 -4 -6 *8 *10 'tz 1.û - Ksf 10 100 18-7 -1 41 H.PryKUMAR SWTLL-CONSOLIDATION TEST RTSULTS Fig. 3 SAMPLE 0F: Sondy Ölny ËROM: Boring4@5' WC = 11.3 %, DD = BZ pcf lj t; ADDITIONAL COMPRESSION UNDER CONS'ANI PRESSURT ÞU[ TO WHTTING I (\ ) ftr!. ilel tclull! oppç o¡ly t th..ompl!! t..ld. lñ! l.rt'¡q rqd lhorl not b! r.rroouc¿d,6ic¿ir iñf!ll, iilfoll th. rdtl.n opp,oror or Kum¿r o¡d &rociot.3. r¡c. St.ll Con.olìdotan 1rdì¡9 r4¿snd íô oicôrdô¡c€ yith ÀS* 0-.51ô. APPLIEO _ KSF 10 t0û 0 ñ JJ L¡l3tn I zotr c: tnz(f (J -1 -2 -1 -4 -6 -8 18-7 -1 41 H-PryKUMAR SWELL_CONSOLIDATION TEST RTSULTS Fig. 4 ¡ t SIEV' ANÁLYSIS u,s. gÄtÐâRo CLÊÂR SOUAi€ OP€I¡NCS 3l¿" t/a' 1 t/.â -+ HYDROM€IER ANÂLYS'S a ro0 90 80 70 60 50 40 l0 20 fo o o to 20 !o 40 60 70 a0 90 too a Ê .a2s PARTICLES IN M'LLIM CLAY TO S¡LT COBBLES GRÂVEL 65 % SAND 30 % LIQUID LIMIT PLASTICITY INOCX SAMPLE 0F: Sqndy Grov€l snd Coþblss SIL1 AND CLAY NP 3% FRoM: Borlng 1 O 4.5'-5,5' lha¡c l¡rl rcsults opply on¡y lo lhrsomp¡.! wh;ch w€re lo9l6d. Íh6ksling rcport sholl nol ba r.producrd,.rc.pt In lull. wllhoul lh. wrlfl.n opp.oyol of l(lmor & Aelocioks, lnc.SLvc onolysfr lasl¡ng Is prrtorñad ln occordoñc. wllh ÀSlM 0422, ASTM C136andlor ÂSTM 0t t40. SAND GRAVEL FINE MEDTUM lCOlnSe flNf coARsr 18-7 -1 41 H-PryKUMAR GRADATION TIST RTSULTS Fig. 5 H.PIKUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No. 18-7-141SOILTYPESandy Gravel and CobblesSandy ClayClayey SandSandy Clay12.56s305NPUNCONFINEDCOMPRESSIVESTRENGlH(psfìiRG L¡MITSPLASTICINDEX(%lATTERBLIQUIDLIMIT(%lPERCENTPASSINGNO.200SIEVEGRADATIONSAND%lGRAVELØlNATURALDRYDENSITY(ocf)828982NATURALilOISruRECONTENTlo/"113.58.811.3SATIPLE LOCATIONDEPTHtfrt4Vz-sYz7Y23Vz3PITI234