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Home My WebLink AboutSubsoil Study 05.11.2022GEOLOGIC REVIEW AND SOILS ENGINEERING REPORT O LAIRD COURT GLENWOOD SPRINGS, CO REcËr\i $llô,Y' ì 'i :t]l,t,? Prepared For: J. Galiber Construction GARFIËLD COUNTY GOMMU NITY DEVE LoPIIIENT Prepared By CAPSTO'VE WEST,ENTERPRISES LLC GEOTECHNICAL AND MINING ENGINEERING TESTING AND INSPECTION SERVICES óI8 PARTEE DRIVE GRAND JUNCTION, CO 81501* PHONE (e70) 2s0-5551 ma rt¡ n @ca psto newest. com July 1,2O21 Job 4640 \.@ WEST, .w LLC' GEOTECI.INICAL AND MINING ENGINEERING TESTING AND INSPECTION SERVICES óI8 PARTEE DRIVE GRAND JUNCTION, CO 81504 PHoNE (970) 250-5551 martin@capstonervest.com July 1 ,2021 JOB # 4640 Attention J. Caliber Construction jose@ca I i berconstruction. com Subject:Geologic Review and Soils Engineering Report 0 Laird Court Glenwood Springs, CO As per your request, Capstone Enterprises West, LLC performed a geotechnical investigation of the aforementioned parcel. The purpose of this work was to determine if the soils at the sites were suitable for housing construction. This repoft contains results of the subsurface investigations and foundation recommendations. SITE LOCATION The property is located near the center of section 3 Township 7 South Range 89 West. The following map shows the general location' CAPSTONE ENTERPRTSES 2CAPSTONE ENTBRPRISES 4640 ì\ t I Site LocationÆt \t ,^l '. I ,,Çrtt '- :':I $. "¿3r, 3l ,t i:a.i a; *Ft "l _r1 ,l gr (- I I1 i¿ è u, \ I '-/ 1. I t .ú''.*...,' ;J- ¿{t ,¡t ,.sitå \ I lr s + ¿rá ¡'l\i I ;i., :,4 {,t,, , .l /91 ll .!. Ir¡l.t, ','' I {,l't i,1t s 3 .) ,ı. q CAPSTONE ENTERPRISES 4640 SITE DESCRIPTION The property is generally flat, sloping at approximately 1o/o to the north. The lot and covered with wild grass. GEOLOGIC DESCRIPTION Bedrock at the site is Mancos Formation; however, at this site the bedrock has been blanketed by a several layers of colluvium (debris flows) from the flank of Grand Hogback to the west. The following geologic maps show the regional geology. t ¿¡å'ãE z aÍ¡tr) *:ÉlV{ CX rrOrtr{ rNË Site Geology ¡ À CATTLE CREEK QUADRANGLE GEOLOGIC MAP, GARFIELD COUNTY, COLORADO By Robert M. Kirkham, Randall K. Streufert, H. Thomas Hemborg, and Peter L. Stelling 2014 4CAPSTONE ENTERPRTSES 4640 s\o.nr(/)r'l(nHú0rú,t'lE-rt'lt'loEiU)ÊrOoE IE5 :Et 2ECI Èj99 oo ,p.095 o,ıo=>€Ë oor¿ÈeC)Eo ãıbà -g€Pç o 9.= c)Ë Ë 2 €:(J,=:C)I,ÞØ¡¿_o(¡)E-((,-CO_vtptr;oLØg)A E É Ë Ez,Øoo g = '=ı,ÉFÈÄx-có;gE ËËþEËË ÊH2aËËtrgEUJOØurt_L9? ã Ë qs Ë ËþıEå1ô:ı5E€€4=àËãËþ-esEd Ê,rÈö 2 Ë¿ì1 ..\¡f)',ÌÎt *,lIa?¿eIÈâ;::aizE-a9eS3:Ð?Ê"=9!-==:,c->iÊE¿,?=2.=';.=:z=3=!?-¿>2à-E:å=j:€a¿3dtLtt=â,-i!t-1 =ıOî2a9¿>.Àgås!gFIAAl¡¡lûll lzl"g"l lålrtottôt:i-.1119i': ^l t- 1 k¡'o(ot.lElo6ooE.Lr)ttJJð{loûFØr¡l¡¡L7,r¿¡¡¡bz;¡Io¿:nlqtt)ot¡êJJ4-t--:" þ'l!€,¡\.t¡i.¡ÈI.1-I5¡ TP.1 0 Topsoil Clay w/ Roots Reddish Brown Clay PI=21 Cobble and Boulders Mini-Ex Retusal TP-2 Topsoil Clay w/ Roots Reddish Brown Clay PI=16 Dry Density 105.8 Pcl Moisture 14.3olo Cobble and Boulders Mini-Ex Retusal Topsoil Clay w/ Roots Reddish Brown Clay Dry Density Moisture 10 98.1 pcf .4o/o TP-3 0 I 2 3 4 5 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6CAPSTONS E}ITEP.I'P,]SI! Á 1A I 10 I-ABORATORY RESULTS The suitability for foundation material is generally determined by two tests: the S',1'e!!/Cc;':ecltdation test and the Atterberg Limits test. The Swell/Consolidation tc=t :-"+':-:;i:î: ¡f ;!,:,-'11:; =ll '-::-:,-1::tr-:r'bed sample of material in a device that applies a load to the seil. Th: lp':':i:-,::,-' ::':::;'=:i: a',- "ú':'-:=iij:l::". /'ii:',- ti': i:-ritl:i i::'i stabilizes, thl spltinncl i: set'-lrltld, alj th: s¡l::=.:;. l:iil ¡;:-!::',':.-:!l c-r .-.-.:::.-.ii.ì=:= :::-r.::¡. ii:: ¡+:Ults 3!'9 pre:ented belOW and On the fOllOWing page. TP-2 at2ft 0.00o/o -1.00o/o -2.00o/o -3.00% 4.00o/o -5.00% -6.00% -7.00o/o -8.00% -9.00% -10.00% Lane Job Number Sample Source Sample Description Natural Dry Density Natural Moisture Content Saturated Moisture Content CONSOLIDATION TEST R=i:'=; APPLIED PRESSURE - psf Job No. 0 Laird Lane TP-2 at2ft Silty Clay 105.8 pcf 97% Relative ComPaction 14.3o/o -2.2o/o From OPtimum 20.1% = É.Þ an t-zu¡o É.t¡lo- 7 0ir0 \A/ATEF ADDI :-D' CAPSTONE BNTERPRISES 4640 GO NSOLIDATION TEST REPORT TP-3 at 4 ft 0.00% 1 za É.t-U't-z t¡J(J Éulo- -'l.0lo/o -2.00% -3.00% 4.00o/o -5.00% -6.00% -7.00% -8.00% -9.00% -10.00o/o APPLIED PRESSURE- Psf Job No- 0 Laird Lane l0 )¡ 0 )Et \WATI RAE \\ \ \ \ \ Job Number Sample Source Sample Description Natural Dry Density Mtural Moisture Content Saturated Moisture Content Job No. 0 Laird Lane TP-3 at 4 ft Silty Clay 98.1 pcf '1o.40/o 24.7o/o 90% Relative Compaction -6.1% From Optimum The Atterberg L¡mits Test gives an indication of the mechanical properties of fine- gra¡ned mater¡als. The first part of the test is to determine the Plastic Limit of the material. Then the Liquid Limit is determined. The diffe,-=-:= b=ï;==- tl= Liç'-:id ICAPSTONB ENTERPRTSES 4640 Plasticity lndex (Pl)Inherent Swelling Capacity 0-1 5 Low 10-35 Medium 20-55 High 35+Very High Limit and the Plastic Limit is defined as the Plasticity lndex. Swell potent¡al based on the plasticity limit (Pl) are shown below. (After Seed et al. 1962) The results of the tests performed on the native materials are presented below. A gradation test of the composite sample of TP-1 and 2 show 71% passing the 200 mesh sieve. The Atterberg Limits test indicates that all of the soils have swell potential. Generally, swelling soils exhibit swelling when dry and well compacted. This was confirmed by the Swell\Consolidation test. These tests indicate that while there ís some swelling it is a relatively small volume change (0.3%). This swelling would result in a displacement of O.22" for a 6' depth of wetting. To determine the relative compaction of the soils in their native state, a St:rCerd Proctor test was performed on a composite of TP-1 TP-z reddish brown clay. This test determines the maximum dry density a soil can be compacted to, for a given compactive effort. The results are presented on the following page. o Material Depth Liquid Limit Plastic Limit Plasticity lndex TP-1 Red Brown Clay 2to3ft 40 19 21 TP-2 Red Brown Clay 2to3ft 35 19 16 CAPSTONE ENTERPRISES 4640 MOISTURE-DENSITY RELAilON ßSÏì,1 D-698) J Caliber 0 Laird Lane Composite Red-Brown Silty Clay Job No" 108.7 pcf @ 16.50/0 MOISTURE 114.0 112.0 Êt¡ CL Ë{, =t¡¡ct Écr 11 0"0 1 08.0 106.0 104.0 102.0 100.0 10o/o 12o/o 14o/o 16o/0 180h 20Vo 22o/o MOISTURE CONTENT% , I / \ \ / / \ \ CAPSTONE ENTERPRISES 4640 10 DESIGN CONCERNS The soils at the site vary in the degree of compaction. This is typical for debris flow deposits; the material is placed in an uncontrolled manner. When moisture conditioned and compacted, they are suitable for foundation material. Care must be taken when excavating boulders at the subgrade elevation as the excavation my disturb soils below the desired depth, resulting in soft spots below the foundation. FOU N DATION RECOMMEN DATIONS We recommend this structure be constructed on a stemwall and footer system on a compacted fill mat. The mat should be 2 feet thick and the subgrade should be compacted before constructing the mat. A maximum bearing load of 1,500 psf should not be exceeded. The following are generalized sketches of the overall construction of the mat. ORGANICS TO BE REMOVED FROM FOUNDAfiON FOOTPRINT EXCAVATION The footprint of the foundation should be cleared of organic material then moisture conditioned and compacted. This subgrade prep should extend 3 feet beyond the perimeter of the structure. SUBGRADE PREPARATION Once the clearing has been completed, the subgrade should be moisture conditioned and compacted. The subgrade should be scarified to a depth of 6 to 8 Impart,+/-2o/oBackfìll +95olo MC Native Backfill +95olo Compaction at +/- 2olo Opt MC Subqrade Moisture Conditioned and Compactecl +95% compaction at +/- 2% oPt MC0 3 I 0 1 0 CAPSTONE ENTERPRISES 4640 11 inches then thoroughly soaked and compacted. Any soft spots noticed during compaction should be removed or reconditioned. Moisture conditioning may require drying. lf very soft spots are encountered geotextile reinforcement may be required, contact Capstone if these conditions are encountered. BACKFILL All structural f¡ll should consist of non-expansive, non-free-draining granular material with a Pl of 10 or less. The native soils don't meet these requirements. Capstone recommends that imported aggregate be used for the structural fill. All fill material should be moisture conditioned and placed in lifts compatible with the compaction equipment, and never exceed 12" in thickness. The structured fill should be compacted to at least 95 percent of the maximum standard Proctor density at a moisture content at or above optimum. The mat should be constructed with native materials that are free of organics with no cobbles larger than 6". The pad should be capped with a minimum of 12" of imported aggregate to insulate the native from surface water and prevent cobbles from being in contact with the concrete foundation. We recommend that Capstone staff be contracted to pedorm field moisture density testing to confirm compaction is being obtained. Tests should be performed on the subgrade, after the 1 foot of fill is compacted and at the final grade. SLAB CONSTRUCTION Slab-on-grade construction may be used if the same subgrade preparation as described earlier is used: o 1 foot imported structural fill mat below foundation. r 1 foot native soils moisture conditioned (above optimum) and compacted o Moisture condition bottom of excavation (preferably overnight) o Compact subgrade and backfill to greater than 95% of Standard Proctor at or above optimum moisture. CAPSTONE ENTERPRISES 4640 1) Slabs should be provided with control joints to reduce damage due to shrinkage cracking. lt is recommended controljoints be spaced atl2feet on centers or less. WATER SOLUBLE SULFATES Gypsum crystals were observed in the sediments. This indicates a sulfate content of in excess of 2000 ppm. This concentration of water soluble sulfates represents a severe degree of sulfate attack on concrete exposed to these mater¡als. Based on this observation, sulfate resistant cement (Type ll modified) should be used in all concrete exposed to the on-site soils. SURFACE DRAINAGE AND 1ANDSCAPING The success of shallow foundations and slab-on-grade systems is contingent upon keeping the subgrade soils at more or less constant moisture content, and by not allowing surface drainage a path to the subsurface. Positive surface drainage away from structures and exterior slabs must be maintained at all times. Landscaped areas should be designed and built such that irrigation and other surface water will be collected and carried away from foundation elements. The final grade of the foundations backfill and any overlying concrete slabs or sidewalks should have a positive slope away from foundation walls on all sides. We recommend a minimum slope of 12 inches in the first 10 feet; however, the slope can be decreased to 4 inches in 10 feet if the ground surface adjacent to foundations is covered with concrete slabs or sidewalks. Backfill material should consist of non-expansive, non-free draining granular material. Backfill material should be placed near optimum moisture content and compacted to at least 90% of maximum standard Proctor density in landscaped areas and to at least 95o/o mâximum standard Proctor density beneath structural areas (sidewalks, patios, driveways, etc.). All roof downspouts and faucets should discharge well beyond the limits of all backfill. lrrigation within ten (10) feet of foundations and driveway slabs should be carefully controlled and minimized. The collapsing soils are very sensitive to moisture changes. Thus, control of watering and downspouts next to foundation members is essential. CAPSTONB ENTERPRISES 4640 13 LIMITATIONS The analysis and recommendations submitted in this repoft are based in part upon the data obtained from the excavations and field observations. The nature and extent of variation may not become evident until construction. lf variations then appear, it will be necessary to reevaluate the recommendations in this report. It is recommended that the geotechnical engineer be provided the opportunity for general review of the final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and specifications. lt is also recommended that the geotechnical engineer, or a qualified geo{echnician under his supervision, be retained to provide continuous engineering services during construction of the foundation, excavations, and earthwork phases of the work. This is to observe compliance with the design concepts, specifications, or recommendations and to modify these recommendations in the event that subsufface conditions differ from those anticipated. This repoft does not constitute a warranty either expressed or implied, as no one can predict the long-tern changes in subsufface moisture conditions resulting from improper grading, excessive irrigation by the home owner or neighbors or other causes during and after construction. lf you have any questions, or if we may be of further assistance, please do not hesitate to contact us. Respectfully Submitted: CAPSTONE ENTERPRISES WEST, LLC Martin W. Chenoweth, PE Registered Professional Engineer MWC s7781 Rf CAPSTONE ENTERPRISES 4640 I4 SITE DESCRIPTION The property is generally flat, sloping at approximately 1o/o to the north. The lot and covered with wild grass. GEOLOGIC DESCRIPTION Bedrock at the site is Mancos Formation; however, at this site the bedrock has been blanketed by a several layers of colluvium (debris flows) from the flank of Grand Hogback to the west. The following geologic maps show the regional geology. ,.i*t/ ; .* I Êt Êå¡ È {wilcGßÂc{ (rofocrrNÊ Site Geology å CATTLE CREEK QUADRANGLE GEOLOGIC MAP, GARFIELD COIJNTY, COLORADO By Robert M. Kirkham, Randall K. Streufert, H. Thornas Hemborg, and Peter L. Stelling 2014 0Þ9t susrEduE'lN3 ãNOúSdV)uolle^ola leql o^oqe olqel lole/v\ 116¡r.l leuoseos e lo ocuapt^e Áue olaqtse/v\ loN 'laol 6 ¡o q¡dep e ol slld lsol aql ul pololunocuo sem lolem punolô o¡USIVAAGNNOUÐ'otorld aql Mollol s6o¡ cl6o¡oe6 eq1'uun sdÐ plotlpueq e Áq pe¡eco¡ s¡ld lsat lo uoltecol oql pue ous oql sMotls quefe¡$oog ruo.r¡ o¡oqd ¡eue ôurrvrollol or.[ 'olrs oq] le pole^ecxo olo/v\ stld ]sal oalLllSNOIIVÐIIS3ANI ]CVIH NSSNS,(¡lo uo¡t¡¡s ssru¡ üû u.rxl¡5-rlrodlp ¡c¡¡U¡nr pr¡a!¡üü¡J¡!PüIìosrtsodS0 0SrYlrNSugJJloNlì(ôu¡il¡tslnld .'.¡lpplu PüB rttl) rn¡o'lotÞsrtsodS0 Nvl'lo36crortpOE(iJß!u.ll ttnl ¡o ¡utrotf!¡ld ¡Fsi) lù.\srE r¡t¡rsrq ¡r.u¡t¡;1¡(¡u.rrolrtilJ) ¡¡liodt¡r $oU'sFq¡lì plo(¡urJo¡¡!¡ld) pJp!.tlpun run!rnllor llüa un!.rnllE irplo(iüorotrlrld J¡tr1 putr ¡urtoloH) ¡l!sodJp ¡rol¡-s!JqðP Ðltlp¡rü¡nlrl(Jutrolo¡l) pùpl.rtpun'un!.tnll{,) Prt lunl.rnllY(iuùoloH) $¡l$rd¡p nog'r¡rqr¡r nllno,lþ"13BÞ^,posrrso¿xo "lvl ^ f l'l'Io J\".x{.tI-¡t-;IFp,rtI'¡(ti;+¡Òr'Oj:.\::. . tl'o¡ie*à'¡d TP- 1 TP.2 TP.3 0 0 1 4 5 1 2 3 4 5 0 1 2 3 4 5 Topsoil Clay w/ Roots Redd¡sh Brown Clay Pl=21 Cobble and Boulders Mini-Ex Refusal Topsoil Clay w/ Roots Reddish Brown Clay Dry Density 98.1 pc{ Moisture 10.4olo Topsoil Clay w/ Roots Reddish Brown Clay PI=16 2 3 6 7 9 Dry Density 105.8 Pc1 Moisturc 14.3olo Cobble and Boulders Mini-Ex Refusal 6CAPSTONE ENTERPRISES 4640 10 I.ABORATORY RESULTS The suitability for foundation material is generally determined by two tests: the Swell/Consolidation test and the Atterberg Limits test. The Swell/Consolidation test consists of placing an undisturbed sample of material in a device that applies a load to the soil. The specimen compacts or "consolidates". After the in¡tial load stabilizes, the specimen is saturated, and the specimen will either swell or consolidate fufther. The results are presented below and on the following page. IP-2 at2ft CONSOLIDATION TEST REPORT 0.00% 1 z É.Fø Fzl¡¡o É.lrlG -1.00o/o -2.00"/r -3.00% 4.OO% -5.00% -6.00% -7.OÙYo -8.00% -9.00% -10.00% APPL¡ED PRESSURE - psf Job 1,,1o. 0 La¡rd Lane r0 A'ATtrE ^nnt :D- Job Number Sample Source Sample Description Natural Dry Density Natural Moisture Cor¡tent Saturated Moisture Content Job No. 0 Laird Lane TP-2 at2ft Silty Clay 105.8 pcf 97% Relative Compaction 14.3% -2.2o/o From Optimum 2O.1o/o 1CAPSTONE ENTERPR]SES 4640 CONSOLIDAf,ION TEST REPORTIP-3 at 4 ft 0.00% 1 z É.Þ(t, ¡-zl¡lo É. IJJo- -1.OOo/o -2.00o/o -3.00% 4.00% -5.00% -6.00% -7.00% -8.00% -9_00% -10.00% APPLIED PRESSURE - psf JobNo. 0 Låird Lane u0l0 ) ì. )Et \WATI ,RAX \\ \ \ \ Job Number Sample Source Sample Description Natural Dry Density Natural Moisture Content Saturated Moisture Conter¡t Job No. 0 Laird Lane TP-3 at 4 ft Silty Clay 98.1 pcf 't0.4% 24.7o/o 90% Relative Compaction -6.1% From Optimum The Atterberg Limits Test gives an ¡ndication of the mechanical properties of fine- gra¡ned materials. The first part of the test is to determ¡ne the Plastic Limit of the material. Then the Liquid Limit is determined. The difference between the Liquid ICAPSTONE ENTERPRISES 4640 Plasticity Index (Pl)lnherent Swelling Capacity 0-1 5 Low 10-35 Medium 20-55 High 35+Very High Limit and the Plastic Limit is defined as the Plasticity lndex. Swell potential based on the plasticity limit (Pl) are shown below. (After Seed et al. 1962) The results of the tests performed on the native materials are presented below A gradation test of the composite sample of TP-1 and 2 show 71% passing the 200 mesh sieve The Atterberg Limits test indicates that all of the soils have swell potential. Generally, swelling soils exhibit swelling when dry and well compacted. This was confirmed by the Swell\Consolidation test. These tests indicate that while there is some swelling it is a relatively small volume change (0.3%). This swelling would result in a displacement of 0.22" for a 6' depth of wetting. To determine the relative compaction of the soils in the¡r native state, a Standard Proctor test was performed on a composite of TP-1 -lP-2 reddish brown clay. This test determines the maximum dry density a soil can be compacted to, for a given compactive effort. The results are presented on the following page. 9 Material Depth Liquid Limit Plastic Limit Plasticity lndex TP-1 Red Brown Clay 2to3ft 40 19 21 TP-2 Red Brown Clay 2to3ft 35 19 16 CAPSTONE ENTERPRISES 4640 MOISTURE-DENSITY RELAflON (ASTïtl D-698) J Celiber 0 taird Lane Composite Red-Brown Silty Clay Job No. 108.7 pcf @ 16.50¿ MOISTURE 114.0 112.0 a,è È cl, =¡¡¡o É,ê 110.0 1 08 0 106.0 104.0 102.0 100.0 109o 12%14%164/0 18%ZÙo/o 22o/o MOISTURE CONTENT% I / / \ \ / / \ CAPSÎONE ENTERPRISES 4640 10 DESIGN CONCERNS The soils at the site vary in the degree of compaction. This is typical for debris flow deposits; the material is placed in an uncontrolled manner. When moisture conditioned and compacted, they are suitable for foundation material. Care must be taken when excavating boulders at the subgrade elevation as the excavation my disturb soils below the desired depth, resulting in soft spots below the foundation. FOU N DATION RECOMMEN DATIONS We recommend this structure be constructed on a stemwall and footer system on a compacted fill mat. The mat should be 2 feet thick and the subgrade should be compacted before constructing the mat. A maximum bearing load of 1,500 psf should not be exceeded. The following are generalized sketches of the overall construction of the mat. ORGANICS TO BE REMOVED FROM FOUNDATION FOOTPRINT EXCAVATION The footprint of the foundation should be cleared of organic material then moisture conditioned and compacted. This subgrade prep should extend 3 feet beyond the perimeter of the structure. SUBGRADE PREPARATION Once the clearing has been completed, the subgrade should be moisture conditioned and compacted. The subgrade should be scarified to a depth of 6 to 8 Import, Granular Non-Free-Lrmrnr ng d Backfìll +95o/o Compaction +/-2o/o Opt MC Native Backfill +95o/o Compaction at +/- 2olo Opt MC Subgrade Moisture Conditioned and Compacted +95oó Compaction at +/- 2olo Opt MC0 3 1 0 1 0 CAPSTONE ENTERPRISES 4640 11 inches then thoroughly soaked and compacted. Any soft spots noticed during compaction should be removed or reconditioned. Moisture conditioning may require drying. lf very soft spots are encountered geotextile reinforcement may be required, contact Capstone if these conditions are encountered. BACKFILL All structural fill should consist of non-expansive, non-free-draining granular material with a Pl of 10 or less. The native soils don't meet these requirements. Capstone recommends that imported aggregate be used for the structuralfill. Allfill material should be moisture conditioned and placed in lifts compatible with the compaction equipment, and never exceed 12" in thickness. The structured fill should be compacted to at least 95 percent of the maximum standard Proctor density at a moisture content at or above optimum. The mat should be constructed with native materials that are free of organics with no cobbles larger than 6". The pad should be capped with a minimum of 12" of imported aggregate to insulate the native from surface water and prevent cobbles from being in contact with the concrete foundation. We recommend that Capstone staff be contracted to perform field moisture density testing to confirm compaction is being obtained. Tests should be performed on the subgrade, after the 1 foot of fill is compacted and at the final grade. SI.AB CONSTRUCTION Slab-on-grade construction may be used if the same subgrade preparation as described earlier is used: o 1 foot imported structural fill mat below foundation. o 1 foot native soils moisture conditioned (above optimum) and compacted o Moisture condition bottom of excavation (preferably overnight) . Compact subgrade and backfill to greater than 95o/o of Standard Proctor at or above optimum moisture. CAPSTONE ENTERPRISES 4640 I2 Slabs should be provided with control joints to reduce damage due to shrinkage cracking. lt is recommended controljoints be spaced all2 feet on centers or less. WATER SOLUBLE SULFATES Gypsum crystals were observed in the sediments. This indicates a sulfate content of in excess of 2000 ppm. This concentration of water soluble sulfates represents a severe degree of sulfate attack on concrete exposed to these materials. Based on this observation, sulfate resistant cement (Type ll modified) should be used in all concrete exposed to the on-site soils. SURFACE DRAITIAGE AND I.ANDSCAPING The success of shallow foundations and slab-on-grade systems is contingent upon keeping the subgrade soils at more or less constant moisture content, and by not allowing surface drainage a path to the subsurface. Positive surface drainage away from structures and exterior slabs must be maintained at all times. Landscaped areas should be designed and built such that irrigation and other surface water will be collected and carried away from foundation elements. The final grade of the foundations backfill and any overlying concrete slabs or sidewalks should have a positive slope away from foundation walls on all sides. We recommend a minimum slope of 12 inches in the first 10 feet; however, the slope ç¿¡n be decreased to 4 inches in 10 feet if the ground surface adjacent to foundations is covered with concrete slabs or sidewalks. Backfill material should consist of non-expansive, non-free draining granular material. Backfill material should be placed near optimum moisture content and compacted to at least 90o/o of maximum standard Proctor density in landscaped areas and to at least 95% maximum standard Proctor density beneath structural areas (sidewalks, patios, driveways, etc.). All roof downspouts and faucets should discharge well beyond the limits of all backfill. lrrigation within ten (10) feet of foundations and driveway slabs should be carefully controlled and minimized. The collapsing soils are very sensitive to moisture changes. Thus, control of watering and downspouts next to foundation members is essential. CAPSTONE ENTERPRISES 4640 LJ LIMITATIONS The analysis and recommendations submitted in this report are based in part upon the data obtained from the excavations and field obseruations. The nature and extent of variation may not become evident until construction. lf variations then appear, it will be necessary to reevaluate the recommendations in this report. It is recommended that the geotechnical engineer be provided the opportunity for general review of the final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and specifications. lt is also recommended that the geotechnical engineer, or a qualified geotechnician under his supervision, be retained to provide continuous engineering services during construction of the foundation, excavations, and eafthwork phases of the work. This is to observe compliance with the design concepts, specifications, or recommendations and to modify these recommendations in the event that subsudace conditions differ from those anticipated. This repoft does not constitute a warranty either expressed or implied, as no one can predict the long-tern changes in subsu¡'face moisture conditions resulting from improper grading, excessive irrigation by the home owner or neighbors or other causes during and after construction. lf you have any questions, or if we may be of further assistance, please do not hesitate to contact us. Respectfully Submitted: CAPSTONE ENTERPRISES WEST, LLC Martin W. Chenoweth, PE Registered Professional Engineer MWC 37784 CAPSTONE BNTERPRISES 4640 I4