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Home My WebLink AboutSubsoils Report for Foundation Designl(+A K*mar & Sssc*iat*s* {nc"i' Geot*cl:nicel *nc l\4alerialg Enltiric*ts anrl Inyitirnmeniel $cienli,tle &n Ertzglayes 0wn*d **mpar*y 5020 County Roacl 15.1 Clenwood Sprirrgs, CO 81601 phone: (970) 945-'1988 fax: (970) 945-8454 errrai I : lcaglenlvood(?kumar-tlsa.com u,wlt'. kutrtatusut. co m Office Locations: Denvcr (HQ). Pall<cr', Colc.rratlo Splings. Irort Llollins, (ilenrvood Sqrrings, attd Sunrmit County, Colorado January 2,2025 Ram Development Attn: Bobby Almazan P.O. Box 1387 Carbondale, Colorado 81 623 bobbv@ranrdev.builcl Project No.24-7-675 Subject: Observation of Pit Excavations, Ptoposed Residence, l2 Weeping Willow Lane, Lot 8, Roaring Fork Preserve, East of Carbondale, Garfield County, Colorado Gentlemen: As requested, a representative of Kumar & Associates, Inc. observed the excavation of 3 pits at the subject site on December 4,2024 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 observation was periormed in accordance with our agreement for professional services with Ram Development dated November 25,2024. The development area is relatively flat, open irrigated field with a slight slope down to the west- northwest. Vegetation consists of field grass in the proposed development area. At the time of our visit to the site, three pits were excavated about 3% to 6 feet below the adjacent ground surface. The soils exposed in the pits consisted ofabout I foot oforganic topsoif and I to 1/' feet of sandy silty clay overlying relatively dense, slightly silty sandy gravel with cobbles down to the maximum depth explored of 6 feet. The results of a gradation analysis performed on a sample of the sandy gravel soils (minus 6-inch fraction) obtained from the site are presented on Figure 3. No free water was encountered in the pit excavations and the soils were slightly moist. Our experience in this area is that groundwater can rise to within 4 feet of the ground surface. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the expected construction, we recommend spread footings placed on the dense gravel soil designed for an allowable soil bearing pressure of 3,000 psf for support of the proposed residence. Footings should be a minimum width of l6 I loI continuous walls and 2 feet for columns. Loose and disturbed soils and existing topsoil and clay encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural gra vel soils. If needed, structural fill placed below footings should consist of rffipactedtoatr the on-site granular soils or a suitable soll east 98% of the maximum standard Proctor density at a moisture content near optimum. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches Ram Development January 2,2025 Page 2 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 length of at least l0 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 45 pcf for the on-site gravel soil as backfill. Floor Slabs: The natural on-site soils, exclusive of topsoil and any disturbed soils from previous excavation on the site, 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 controljoints 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 basement level slabs to facilitate drainage. This material should consist of minus 2-tnch aggregate with less than 50%o passing the No. 4 sieve and less than2o/o passing the No. 200 sieve. Atj!th@supportoffloorslabsshouldbe-9ompactedto3tleast.95%oofmaximum stai?Iffil-Proctor density at a moisture content near optimum. Required fill can consist of the on-site gravel soils devoid of vegetation, topsoil and oversized rock or an imported gravel soil, such as t/+-inch road base. Underdrain System: Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. A previous pit dug on this site in 2000 showed groundwater at 4 feet deep. We recommend below-grade construction, such as retaining walls or deep crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. Slab at grade construction and shallow crawlspaces should not require a perimeter drain. If installed, 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 I foot below lowest adjacent finish grade and sloped at a minimum 1%o to a suitable gravity outlet or sump and pump. Free-draining granular material used in the underdrain system should contain less than 2Yo passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum stze of 2 inches. The drain gravel backfill should be at least 1% feet deep. Due to the relatively flat temain, if installed, the perimeter drain system will need to be pumped to a ground surface outlet. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: Kumar & Associates, lnc. @ Project No. 24-7-675 Ram Devsiopm*nt Janua:'y 2,2{}25 Fage 3 1)lnundatic* of tha: fbundati*n exoavatielr'ls and underslab areas should be avoirled during eoi:structi*n. Exterior haekfill sh*uld be adjusted to trear *ptin:r.im moisture and ccn:pacted tir at least 957i' *f the maximsm s*indarei Pr*ctor d*nsity in paveinent and slab areas and tc at least 909/<r of the ntaximum stanelard Froct*r dearsity in landseape areas. Free-draining wall hackfill should b* eapped with ab*ut 2 fect of the on*site, tiner graded soils t* reduce s*rface water infiltrati**" Th* ground surf"a*e s*n"*unding the exteri*r *f the building shauld b* sloped to elrain away fi"arn the f**ndation in altr rlirecti*trs" We r*e*fixitsnd a miniffium strop* of $ inches i* th* {irst } * lbet in unpav*d areas and a minimum slope of 3 inehes in th* first l* feet in pavem*nt anc{ walkway er"eas. Itoaf"downspcuts and clrains should diseh*rg* lr'eil beycnd the iimits of all backfill" 4j The re*a:nmq:ndati*:rs subr*itted in this l*its:r are bas*d *l: sur o?rservation of th* soils exposed within th* ;:it exeav*tion$ et thc site" Variations it: tl:c] s*bsrrrihee eon*liti*ns b*lcw the sxeavatian eclul{i in*rease the risk s}f f$undaticil tnovcret*nt. We shqruld be advised *f any variations ene*unterecl in th* sxcava?i*rl e*nditi*ns for p*ssibl* *h*a:ges to reeomrnendatia:rs ecxg*.;nsd in this letter. Our s*rviess d* not include dstennining tho presenec, prevention or passibility of rnrild or other bioltlgiea} eontami*ants {I\4OEC} d*ve}*:ping in tla* future. If the elient is ccfl*eril*d ai:*ut M{}BC. then a professianal in this sp**iai Seld *f Braetiee should be cansulted. If you have any qu*stions *r ir*ed firther assistane*. please eall aur otfice^ Sineerely, Wummr & {qxn**E:*t*s 2) 3) Daniel E. Hardi*, Rev. by: SLP DflF{lkae attaehme:?ts Figure I *-Loeati+n of Hxpl*ratory Fits F'ig*re 2 - Logs cf Expl*rai*ry Fits Figure 3 -- Gr:adaiian'tr'*st Results F,.vm p,t &" fa*t;i*ti&l*r;, 4**, e Fruja:9 ffier.24"?"S?S 150 0 APPROXIMATE SCALE-FEET 0 24-7 -675 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1 tl -\- A PIT 1 PIT 2 PtT 3/SEPT|C PROFTLE PrT 0 0 Ft!t!tL IIF TL trJo q I ++=os- -200=5 5 Ftrl Lrl LL I-F o_ Lrlo 10 10 LEGEND TOPSOIL. ORGANIC SANDY CLAY WITH ROOTS, SOFT, MOIST, DARK BROWN CLAY (cL); SILTY, SANDY, MEDIUM STIFF To STIFF, MolST, DARK BRoWN GRAVEL (GM_CP); AND COBBLES, SANDY, MEDIUM DENSE TO DENSE, MOIST, BROWN Ir DISTURBED BULK SAMPLE NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON DECEMBER 4, 2024 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3, THE ELEVATIONS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY PITS ARE PLOTTED TO DEPTH 4. THE EXPLORATORY PIT LOCATIONS 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 THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFITTED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (nSfV O +ZZ); -2oo= PERCENTAGE PASSING No. 200 SIEVE (ASTM D 1 1 40). --}- 24-7 -675 Kumar & Associates LOGS OF TXPLORATORY PITS Fi1. 2 .}; HYDROMETER ANALYSIS U.S. STANDARD SERIES CLEARTIME READINGS 1.9tr.l!L.M!tl 24 HRS 7 HRS ,l too 90 ao 70 60 50 10 50 20 to o 10 20 30 40 50 6o 70 ao 90 r00 z I i lr 1 .14 o .oor I llrl ......]r.. r ,r t r.oo9 .ot 9 .o37 .075 : .l 150 DIAMETER OF -125 PARTICLES INM ERS CLAY TO SILT COBBLES GRAVEL 6A % SAND LIQUID LIMIT SAMPLE OF: Sondy Groval with Cobbles 29%SILT AND CLAY 3% PLASTICITY INDEX FROM:Piil@3'-3.5 Thsso tsst resulls opply only to tho sompl€s which w€r6 l€sl€d. Tho lostlhg reporl sholl nol be r€produced, exc€pl in full, wilhoul the wriltsn opprovol ol Kumor & Associolos, lnc. Slev€ onolysls lesllng ls performed ln occordonce with ASTM 06913, ASTM 07928, ASTM Cl36 qnd/or ASTM Dl'140. GRAVELSAND FI NE MEDIUM COARSE FINE COARSE 24-7 -675 Kumar & Associates GRADATION TEST RTSULTS Fis.3