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Home My WebLink About20221327.tiffJanuary 7, 2021 Angela Knopf(angknopf(1gm all 35093 County Road 25 Eaton, Colorado 80615 Re: Geotechnical Subsurface Exploration Proposed Detached Steel Building 3 093 County Road 25 Weld County, Colorado EEC Project No. 20-01-216 Ms. Knopf: C EARTH ENGINEERING COMPANY, INC. Earth Engineering Company, Inc. (EEC) personnel have completed the geotechnical subsurface exploration you requested for the proposed detached building to be constructed at35093 Weld County Road 25 southeast of Severance in Weld County, Colorado. Results of that subsurface exploration are provided with this report. We understand the proposed detached building will be a one or two-story steel frame structure supported over a slab -on -grade type foundation. We expect foundation loads for the proposed structure will be light with continuous wall loads less than 3 kips per lineal foot and individual column loads less than 50 kips. Small grade changes are expected to develop final site grades for the structures. The purpose of this report is to describe the subsurface conditions encountered in the test boring completed within the identified building envelope and provide geotechnical recommendations for design and construction of foundations and support of floor slabs. The building site is located at 35093 Weld County Road 25 southeast of Severance in Weld County, Colorado. The property is presently developed with existing residence located to the southwest of the building envelope and was relatively flat along with vegetation. To develop information on existing subsurface conditions in the area of the proposed detached building, one (1) soil boring was advanced to a depth of approximately 25 feet below site grades at the identified building envelope. The boring was completed using a truck -mounted 1' -55 drill rig equipped with a hydraulic head employed in drilling and sampling operations. The borehole was advanced using 4 -inch nominal P.O. Box 271428, Fort Collins, CO 80527 ,aline phonE: 970.775.2004 fax: 970.663.02 82 Earth Engineering Company, Inc. EEC Project No. 20-01-216 January 7, 2021 Page 2 diameter continuous flight augers and samples of the subsurface materials encountered were obtained using split -barrel and California barrel sampling procedures in general accordance with ASTM Specification D-1586. In the split -barrel and California barrel sampling procedures, standard sampling spoons are driven into the ground using a 140 -pound hammer falling a distance of 30 inches. The number of blows required to advance the samplers is recorded and is used to estimate the in -situ relative density of cohesionless materials and, to a lesser degree of accuracy, the consistency of cohesive soils. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. EEC field personnel were on -site during drilling to evaluate the subsurface conditions encountered and direct the drilling activities. A field log was prepared based on observation of disturbed samples and auger cuttings. Based on results of the field boring and laboratory testing, subsurface conditions in the area of the residence can be summarized as follows. Brown sandy lean clay soils were encountered at the surface at the boring location. The sandy lean clay soils were medium dense in consistency and exhibited a low potential for swelling with variation in moisture content at current moisture/density conditions. The moderately plastic sandy lean clay soils were underlain by brow tan and rust sandstone bedrock at a depth of approximately 7 feet below present site grades. The sandstone bedrock encountered in the boring was poorly cemented in consistency and exhibited a low potential for swelling with variation in moisture content at current moisture/density conditions. The sandstone bedrock extended to the bottom of the boring at a depth of approximately 25 feet below present site grades where the boring was terminated. Observations were made at the time of drilling and approximately 24 hours after drilling to evaluate the presence and depth to free water at the test boring locations. At the time of drilling, free water was observed at a depth of approximately 12 feet below present site grades. Approximately 24 hours after drilling, free water was observed at a depth of approximately 7 feet below present site grades in the completed site boring. Longer term observations in holes that are cased and sealed from the influence of surface water would be required to more accurately determine fluctuations in groundwater levels over time. Fluctuations in groundwater levels can occur based on hydrologic conditions and other conditions not apparent at the time of this report. Zones of perched and/or trapped water may also be encountered in more permeable zones within the subgrade soils at times throughout the year. EEC Project No. 20-01-216 January 7, 2021 Page 3 Earth Engineering Company, Inc The stratification boundaries indicated on the boring tog represent the approximate locations of changes in soil types; in -situ, the transition of materials may be gradual and indistinct. Bedrock classification was based on visual and tactual observations of disturbed samples and auger cuttings; coring and/or petrographic analysis may reveal other rock types. In addition, the test boring provides an indication of subsurface conditions at the test location; however, subsurface conditions may vary in relatively short distances away from that location. Potential variations in subsurface conditions can best be evaluated by close observation and testing of the subgrade materials during construction. If significant variations from the conditions anticipated from the test boring appear evident at that time, it may be necessary to re-evaluate the recommendations provided in this report. ANALYSIS .R.ECOMMENDATIONS Foundations Based on the materials observed in the test boring, it is our opinion the proposed lightly loaded detached steel building structure could be supported on conventional footing foundations bearing in the medium stiff sandy lean clay soils. For design of footing foundations supported on the medium stiff sandy lean clay soils, we recommend using a net allowable total load soil bearing pressure not to exceed 1,000 psi The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load includes full dead and live loads. We recommend the foundation footing design loads be balanced to promote relatively uniform settlement, thereby reducing the potential for differential settlement. As an alternative to balancing the design loads solely on settlement, designing the foundation such that the dead -load pressure is balanced throughout the foundations could be considered. Balancing the dead -load pressure would also reduce the potential for differential settlement between adjacent footings. We estimate the long- term settlement of footing foundations designed and constructed as recommended above would be less than 1 inch. While near surface site cohesive soils did not exhibit appreciable swell potential with variation in moisture content, some consolidation was observed in the near surface samples tested. Close observation and testing will be needed to evaluate the volume change characteristics of the in -situ soils at the time of foundation excavation. If soft or highly compressible soils are observed at that time, reworking of the subgrade or removal and replacement may be necessary to develop suitable foundation bearing. Earth Engineering Company, Inc. EEC Project No. 20-01-216 January 7, 2021 Page 4 No unusual problems are anticipated in the construction of the footing foundations. Care should be taken to avoid disturbing the bearing soils. The natural site soils may be easily disturbed by construction activities. Soils which are disturbed by the construction activities or materials which have become dry and desiccated or wet and softened should be reworked or removed from the foundation excavation prior to the placement of foundation concrete. Floor Slab and Exterior Slab -on -Grade Subgrades In any slab -on -grade areas, those slabs may be supported on existing site soils or newly placed and compacted fill. All existing vegetation and/or topsoil should be removed from the floor or flatwork areas. After stripping and completing all cuts and prior to placement of any fill, floor slabs or other flatwork, we recommend the in -place soils be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the material's maximum dry density as determined in accordance with ASTM Specification D-698, the standard proctor procedure. The moisture content of the scarified soils should be adjusted to be within the range of +% of standard proctor optimum moisture at the time of compaction. Fill soils required to develop the floor slab subgrades shouldconsist of approved, low -volume change materials which are free from organic matter and debris. It is our opinion the on -site sandy lean clay soils could be used as low-evolume change fill in the floor areas. Those fill materials should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content as recommended for the scarified soils and compacted to at least 95% of standard Proctor maximum dry density. After preparation of the subgrades, care should be taken to avoid disturbing the in -place materials. Subgrade materials loosened or disturbed by the construction activities or materials which become dry and desiccated or wet and softened should be removed and replaced or reworked in place prior to placement of the floor slab concrete. As a precaution, the floor slabs should be isolated from structural portions of the building to prevent differential movement to those elements causing distress to the structure. That isolation is typically developed through the use of a voided wall which is suspended from the overhead first floor joist Care should be taken in door framing, drywalling and finishing to maintain a voided space which will allow for movement of the floor slab without transmission of stresses to the overlying structure. EEC Project No. 20-01-216 January 7, 2021 Page 5 Earth Engineering Company,1nc While laboratory testing completed for this report indicated the site soils sampled exhibited relatively low swell potential, floor slab and exterior flatwork movement could occur and should be expected. Slab movement is common in Colorado even in areas with relatively low -swelling soils. Mitigation techniques to reduce the potential for post -construction movement, such as overexcavation, moisture conditioning and replacement could be considered; however, the risk for stab movement cannot be eliminated, Qtiier Considerations Positive drainage should be developed away from the structure with a minimum slope of 1 inch per foot for the first 10 feet away from the building. Care should be taken in planning of landscaping adjacent to the structure to avoid features which would pond water adjacent to the foundations or basement walls. Placement of plants which require irrigation systems or could result in fluctuations of the moisture content of the subgrade materials should be avoided adjacent to the structure. Lawn watering systems should not be placed within 5 feet of the perimeter of the building and spray heads should be designed not to spray water on or immediately adjacent to the structure. Roof drains should be designed to discharge at least 5 feet away from the structure and away from the pavement areas. GENERAL COUNTS The analysis and recommendations presented in this report are based upon the data obtained from the soil boring performed at the indicated location and from any other information discussed in this report. This report does not reflect any variations which may occur across the site. The nature and extent of such variations may not become evident until construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. It is recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. It is further recommended that the geotechnical engineer be retained for testing and observations during earthwork and foundation construction phases to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of Angela Knopf for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranty, express or implied, is made. In the event that any changes in the Earth Engineering Company, Inc. EEC Project No. 20-01-216 January 7, 2021 Page nature, design or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing by the geotechnical engineer. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we can be of further service to you in any other way, please do not hesitate to contact us. Very truly yours, Earth Engineering Company, Inc. iJ A :t0 rri r Michael J. Coley, P.E. Principal Engineer cc: Dan Griffith Qian(�&tccontractin'.com J li XPL + . I l • O1- LDRU R' NG & SAMPLING SYMBOLS: SS: Split Spoon - 1318" I.D., 2" J.D., unless otherwise noted ST: Thin -Walled Tube - 2" D.D,, unless otherwise noted R: Ring Barrel Sampler - 2.42" I.D., 3" 0.D. D. unless otherwise noted PA: Power Auger HA: Hand Auger DB: Diamond Bit = 4", N, B AS: Auger Sample HS: Hollow Stem Auger PS: Piston Sample WS: Wash Sample FT: Fish Tail Bit RB: Rock Bit BS: Bulk Sample PM: Pressure Meter WB: Wash Bore Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30,arches on a 2 -inch 0,D, split spoon, except where noted. WATER LEVEL MEASUREMENT SYMBOLS: WL : Water Level WC!: Wet Cave in DCI: Dry Cave in AB : After Boring WS : While Sampling WD : White Drilling BCR: Before Casing Removal ACR: After Casting Removal Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not possible with only short term observations. DESCRIPTIVE SOIL CLASSIFICATION Soil Classification is based on the Unified Soil Classification system and the ASTM Designations D-2488. Coarse Grained Soils have move than 50% of their dry weight retained on a #200 sieve; they are described as: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are described as : clays, if they are plastic, and silts if they are slightly plastic or non -plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse grained soils are defined on the basis of their relative in - place density and fine grained soils on the basis of their consistency. Example: Lean clay with sand, trace gravel, stiff (CL); silty sand, trace gravel, medium dense (SM). CONSISTENCY OF FINE-GRAINED SOILS Unconfined Compressive Strength, Qu, psf Consistency < 500 500 - 1,000 1,001 - 2,000 2,001 - 4,000 4,001 - 8,000 8,001 - 16,000 Very Soft Soft Medium Stiff Very Stiff Very Hard RELATIVE DENSITY OF COARSE -GRAINED SOILS: N-Blows/ft 0-3 4-9 10-29 30-49 50-80 80+ Relative Density Very Loose Loose Medium Dense Dense Very Dense Extremely Dense PHYSICAL PROPERTIES OF BEDROCK DEGREE OF WEATHERING: Slight Slight decomposition of parent material on joints. May be color change. Moderate Some decomposition and color change throughout. High Rock highly decomposed, may be extremely broken. HARDNESS AND DEGREE OF CEMENTATION: Limestone and Dolomite: Hard Difficult to scratch with knife. Moderately Can be scratched easily with knife. Hard Cannot be scratched with fingernail. Soft Can be scratched with fingernail. ShaleR SiFtstone and Claystone: Hard Can be scratched easily with knife, cannot be scratched with fingernail. Moderately Can be scratched with fingernail. Hard Soft Can be easily dented but not molded with fingers. Sandstone and Conglomerate: Well Capable of scratching a knife blade, Cemented Cemented Can be scratched with knife. Poorly Can be broken apart easily with fingers. Cemented EAPTH TH ENGINEEPING COMPANY, INC, Earth Engineering Company UNEFEE SOIL CLASSITIC A H_ N SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Coarse - Grained Soils more than 50% retained on No. 200 sieve Gravels more than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less Cu≥4 and l<Cc≤3E than 5% fines Soil Classification Group Symbol Group Name GW Well -graded gravel F Cu<4 and/or 1>Cc)3E GP Poorly -graded gravel F Gravels with Fines more than 12% fines Fines classify as ML or MH GM Silty gravel G,H Fines Classify as CL or 01 GC Clayey Gravel F,G,H Sands 50% or more coarsefraction passes No. 4 sieve Fine -Grained Soils 50% or more passes the No, 200 sieve Silts and Clays Liquid Limit less than 50 Clean Sands Less than 5% fines Cu≥6 and 1cCc≤3E SW Well -graded sand I Cu<6 and/or 1>Cc>3E SP Poorly -graded sand I Sands with Fines more than 12% fines inorganic Fines classify as ML or MH SM Silty sand c`"r` Fines classify as CL or CH P+'7 and plots on or above "A" Line Sc Clayey sand GMAT CL Lean clay KL,M organic PIk4 or plots below "Al. Line Uquid Limit - oven dried ML Silt KILN Liquid Limit - not dried <0.75 OL Organic clay CJLM.N Organic silt i't'M'c Silts and Clays Liquid Limit 50 or more Highly organic soils °`Based on the material passing the 3 -in. 135 -mm) sieve @if field sample contained cobbles or boulders, or both, add 'with cobbles or boulders, or both" to group name. CG ravels with 5 to 12% fines required dual symbols: GW-GIMM well graded gravel with silt GW-GC well -graded gravel with clay GP -GM poorly -graded gravel with slit GP -GC poorly -graded gravel with clay °Sands with 5 to 12% fines require dual symbols: SW-SM well -graded sand with silt SW -SC well -graded sand with clay SP-SM poorly graded sand with silt SP -SC poorly graded sand with clay 6O inorganic PI plots on or above "A" Line CH Fat clay ► t,,tit organic PI plots below "A" Line Liquid Limit - oven dried lH Elastic Silt i'i,"+` Uquid Limit - not dried Primarily organic matter, dark in color, and organic odor (DJar ECU—DJDlo Cc= Dig x D60 Flf soil contains ≥154 sand, add "with sand" to Gil fines classify as CL -ML, use dual symbol GC - CM, or SC-SM. "if fines are organic, add "with organic fines" to group name 'If soil contains >15% gravel, add "with gravel" to group name 'I f Atterberg limits plots shaded area, soil is a CL - ML, Silty clay For Classification of fine-gralned soils and fine-grained fraction of coarse -grained 50 soils. E 40 w z 3O u zo 10 EARTH D ENGINEERING COMPANY, INC, Equation of "R" -line Horizontal at PI=4 to LL 25.5 then PI -0.73 (11-20) Equation of "U" -line Vertical at LL=16 to PI -7, then P1=0.9 (LL -S) 10 It I '� 0 r ef r iL OR OL <0.75 OH Organic clay KILIM'F Organic silt ICt'I"rc PT Peat Kif soil contains 15 to 29% plus No. 200, add "with sand" or "with gravel", whichever is predominant. `If soil contains ≥ 30% plus No. 2OO predominantly sand, add "sandy" to group name. "'If soil contains ≥30% plus No. 200 predominantly gravel, add"gravelly" to group name. "PI>4 and plots on or above "Al' line. °P154 or plots below "A" line. PPI plots on or above "A" line. °Pl plots below "A" line. t a al er New It O Fec". re +'R, MH OR OH 20 30 40 5O 60 70 LIQUID LIMIT (LL) 90 1OO 11O • a i a. I. • • r.,........ 7 ' — ■ MIS n a. nos al,l•n -ate • e ziih • ;gar tits' dinsallar. a. sr 1 I. a 35093 llJP I N t V I.L_Li (Sr , rte. 1 - I LOC.A f OTOI I F Its 1 t • . 1 I r# i I a . t • .- 1 WELD COUNTY, rr ri n I I"' r-' PiI I I A r) c-i . a I rt m -. Om*. . rw I Os- O - % • - '- . - . t 1 . t •r L l II a, • .. F . 6 • I +re i w rl •L BORING LOCATION i"�1 nee A7 t1►.Thr. -, . • L 1. in 4 rn_ i _ e r n n Tr. C'ECP= M(f1 B ER 2020 x .. s t I ..� �i . a] .� ■ 71:417,71.1 ENGINEERING COMPANY I —•; tit ��_ a*ra _-_$- -aiegivinmemailiamen rat .�wa•liia•a� _ •-!!T_- I Ma • n • ' -or i� i • *'� Y's -1 - a� a '.8 1L= fiia•"�+s_. y '�! IJ"r!'�R'-_�'R^`�a- -� aal p *. p FS —a --_I_- -r- s r air w,_ -V - -'�—r r +a.* - - we}...a Mir - ad. : -r}t r. L•--as-..a-sa.rarr 1a --_ — •� _ - ..-a- s r-i . emao ti • as saa4 I E • •••• f TY s.44sir�•a•4 a -r'1 -a .-f aria -. G 1 a -=a. --_-_ ai. an - re' [l 2 a sa . -r es- Ariaamaa -44.4t. -44irlarkS 4i IP Lime 'animal '4 - a.a .. c u S} .. -e 6 • - - - -a--- a ye_ nap= •- - a -iia C tea--Zr- ar -alma- -sae Lra-r _ P'I'TT -1 Tom' — a I 35093 WeR 25 z "'Mr WELD COUNT j, Y, CO EEC PROJECT No. 20-01-216 ors —r a r t' 11 i-a = a a I- -- a • - M r hi nr .l -p 'i r, r+. - � Vbr tm P p %-• SOIL DESCRIPTION PROJECT NO: 20-01-216 RIG TYPE: CMES5 35093 WELD COUNTY ROAD 25 WELD COUNTY, COLORADO DATE: DECEMBER 202 LOG OF SORItIG B-1 FOREMAN: SM START DATE AUGER TYPE: 4" CFA FINISH DATE SPT HAMMER: AUTO SANDY LEAN CLAY (CL) brawn medium stiff silty SANDSTONE trown/tanfrust pcoriy cemented TYPE. SHEET 1 OF 1 i WATER DEPTH SURFACE ELE") 15 5016" 9000+ CS _ 20 501'0„ 25' BOTTOM OF BORING ,ACS Earth Engineering Company 1a rYIIslft90 W RJL.E DRILLING 12 1212242020 AFTER DRILLING MC DD _4! (PCF1 24 DOUR 12' -200 SWILL �L P1 % PRESSURE %IC PSR c 500 Rsf None <600 psi None lc 500 Qsf None None SWELL / CONSOLIDATION TEST RESULTS Material Brown Sandy Lean Clay Description: Sample B-1, -1 @ 2' Location. I Plasticity Index: 18 [ % Passing #200: 70.2 Liquid � Limit: 29 16.3% Dry Density: 103.6 pcf jEnding Moisture: 20.9% Beginning Moisture: Swell Pressure: < 500 psf % Swell @500 psf: None Percent Movement 10 8 4 2 0 -2 c -4 0 ITS t. -6 O a -8 -10 0.01 Project: Project No_'. Date: - 1 ■IIN I I I tigirT I : added I I I 0.1 Load (T F) I 35093 WCR 25 - Detached Building Weld County, Colorado 2.0-01-216 December 2020 10 EARTH ENGINEERING COMPANY, INC. SWELL I CONSOLIDATION TEST RESULTS Material Description: Brown Sandy Lean Clay Sample Location: B-1, S-2 @ 4' Liquid Limit: -- Plasticity Index: -- ll % Passing #200: -- Beginning Moisture: 11.8% Dr Density: 97.6 pcf Ending Moisture: 18.1% Swell Pressure: < 500 psf ° Swell @ 500 pst None rcent Movement 0. 10 c -' a 03 13 v C-6 0 C -10 0.01 0.1 Load (TSF) 10 Project: Project No: Date: 35093 WCR 25 - Detached Building Weld County, Colorado 20-01-216 December 2020 C EARTH ENGI NCEPING COMPANY, INC. SWELL /CONSOLIDATION TEST RESULTS F1aterial Description: Brown/Tan/Rust Sandstone Sample Location: B-1, S-3 @ 9' Liquid Limit: -- Plasticity Index: -- % Passing #200: -- Dry Density: 102.6 pet Ending Moisture: 26.7% Beginning Moisture: 22.8% % Swell @ 500 psf: None Swell Pressure: < 500 psf Percent Movement 10 co 0 r�- C 0 O 10 0.01 0.1 I Load (TSF ) Project: 35093 WCR 25 - Detached Building Weld. County, Colorado Project No.: 20-01e216 Date: December 2020 10 S I TH ENGINEERING COMPANY, INC. SWELL I CONSOLIDATION TEST RESULTS Material Description: Brown/Tan/Rust Sandstone Sample Location: B-1, S-4 @ 14' Liquid Limit: --IPIastiEitsf Index: -- 1 % Passing #200: __ Beginning Moisture: 25.0% Dry Density 94.1 pcf 'Ending Moisture: 27.0% Swell Pressure: < 1000 psf % Swell © 1000 psf: None 10 1 II i 6 lovement } a I •1 1 ( I IIa_ l Water ater ddeM t 0 i� I G -7 0 o a AO 0.01 0.1 1 Load (TSF) 10 Project: Project No: Date: 35093 R 25 - Detached Building Weld County, Colorado 20-01-216 December 2020 EARTH EN INEEPINt COMPANY, INC. SWELL I CONSOLIDATION TEST RESULTS Material Description: Brown/Tan/Rust sandstone Sample Location: B-1, S-5 la 19' Liquid Limit: -.: Plasticity Index: -- Passing #200: -- Dry Density: 99.1 pef 'Ending Moisture: 27.9% Beginning Moisture: 26.3% ,I Swell Pressure: < 1000 psf r% Swell C 1000 psi: None Percent Movement 10 16 4 2 0 -2 O 2-6 C O -8 -10 0.01 II Ii 1 II ' Water •dtle■II, • � 1 I 1 I I II I nu M_II ' 0.1 Load (TSF) 1 10 Project: 35093 WOR 25 - Detached Building Weld County, Colorado Project No,; 20-01-216 Date: December 2020 EARTH ENGINEERING COMPANY, INC. Hello