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HomeMy WebLinkAboutGeotechnical Investigation Report 07.17.2015Huddleston -Berry 1 ngineering, & Testing, 1,1.0 RM Construction 151 Clubhouse Drive New Castle, Colorado 81647 Attention: Mr. Bob Gibson Subject: Geotechnical Investigation Lot 287 Ironbridge Glenwood Springs, Colorado Dear Mr. Gibson, 640 White Avenue, Unit B Grand Junction, Colorado 81501 Phone: 970-255-8005 Fax: 970-255-6818 Info mhuddlestonberry.com July 17, 2015 Project#01456-0001 This letter presents the results of a geotechnical investigation conducted by Huddleston -Berry Engineering & Testing, LLC (HBET) at Lot 287 of the Ironbridge subdivision near Glenwood Springs, Colorado. The site location is shown on Figure 1 — Site Location Map. The proposed construction is anticipated to consist of a single-family residence. The scope of our investigation included evaluating the subsurface conditions at the site to aid in developing foundation recommendations for the proposed construction. Site Conditions At the time of the investigation, the site was open. A large tiered modular block retaining wall ran along the eastern and southern edges of the property. The total height of the retaining walls was approximately ten feet. Vegetation at the site consisted primarily of weeds. The site was bordered to the north by an existing residence, to the east by a vacant lot and residence under construction, to the south by an existing residence, and to the west by Blue Heron Vista. Regional Geologic Hazards The Ironbridge subdivision is underlain by bedrock of the Eagle Valley Evaporite consisting of gypsiferous shale, sandstone, siltstone, limestone, and gypsum. The gypsum is susceptible to dissolution resulting in subsidence. In fact, several sinkholes were observed during the initial subdivision development. However, HBET did not observe any depressions, open fissures, or other surface expression of bedrock dissolution at the time of our investigation. Subsurface Investigation The subsurface investigation included three borings as shown on Figure 2 — Site Plan. The borings were drilled to depths of between 9.0 and 38.0 feet below the existing ground surface. Typed boring logs are included in Appendix A. Lot 287 Ironbridge #01456-0001 07/17/15 Huddleston -Berry fnGrxY��n:ST Wit. Let As indicated on the logs, the subsurface conditions at the site were slightly variable. However, the borings generally encountered 3.0 to 5.0 feet of red, dry to moist, very stiff lean clay with sand to sandy lean clay soils above red to brown, moist, medium dense to dense clayey gravel soils. The gravels extended to the bottom of B-3 where auger refusal was encountered. In B-1 and B-2, the gravels extended to a depth of 10.0 feet and was underlain by red to brown, moist, medium stiff to hard lean clay with sand to sandy lean clay soils. The clay soils extended to the bottom of B-1 at a depth of 28.5 feet. In B-2, the clay extended to a depth of 25.0 feet and was underlain by red to brown, moist, loose to medium dense silty sand with gravel soils to a depth of 36.0 feet. Below the sand, brown, moist, dense sandy gravel and cobbles extended to the bottom of the boring at 38.0 feet. Groundwater was not encountered in the borings at the time of the investigation. In addition, no voids or other evidence of solution activity was encountered in the borings. Laboratory Testing Laboratory testing was conducted on samples of the native soils collected from the borings. The testing included grain -size analysis, Atterberg limits determination, natural moisture and density determination, swell/consolidation testing, water soluble sulfates content determination, and maximum dry density/optimum moisture (Proctor) determination. The laboratory testing results are included in Appendix B. The laboratory testing results indicate that the native clay soils are slightly plastic. In addition, the clay soils were shown to tend to consolidate under loading. However, based upon our experience in the vicinity of the site and nature of the site soils, the native clay soils may actually have a slight potential for collapse. Water soluble sulfates were detected in the site soils in a concentration of 0.4%. Foundation Recommendations HBET understands that a basement is not proposed for the structure. In general, based upon the results of the subsurface investigation and nature of the proposed construction, shallow foundations are recommended. Spread footings and raft/mat structural slab foundations are both appropriate alternatives. However, as discussed previously, the native soils may have a slight collapse potential. Therefore, in order to reduce the risk of excessive differential settlements, it is recommended that the foundations be constructed above structural fill extending to the clayey gravel soils. However, a minimum of 24 -inches of structural fill is recommended below foundations. The native clay and gravel soils, exclusive of topsoil, are suitable for reuse as structural fill. Imported structural fill should consist of a granular, non -expansive, non -free draining material such as pit -run with high fines content, crusher fines, or CDOT Class 6 base course. However, if pit -run is used for structural fill, a minimum of six inches of crusher fines or Class 6 base course should be placed on top of the pit run to prevent large point stresses on the bottoms of the footings due to large particles in the pit -run. R.\2008 ALL PROJECTS \01456 - RM Construction \01456-0001 Lot 287 lronbridge\200 - Geo\01456-0001 LR071715.doc 2 Lot 287 Ironbridge #01456-0001 07/17/15 Huddleston -Berry feg3tca+n=k rrvoCI t Prior to placement of structural fill, it is recommended that the bottom of the foundation excavation be scarified to a depth of 6 to 8 inches, moisture conditioned, and compacted to a minimum of 95% of the standard Proctor maximum dry density, within ± 2% of the optimum moisture content as determined in accordance with ASTM D698. Structural fill should extend laterally beyond the edges of the foundation a distance equal to the thickness of structural fill. Structural fill should be moisture conditioned, placed in maximum 8 -inch loose lifts, and compacted to a minimum of 95% of the standard Proctor maximum dry density for fine grained soils and 90% of the modified Proctor maximum dry density for coarse grained soils, within ± 2% of the optimum moisture content as determined in accordance with ASTM D698 and DI557C, respectively For structural fill consisting of the native soils or imported granular materials, and foundation building pad preparation as recommended, a maximum allowable bearing capacity of 2,000 psf may be used. In addition a modulus of subgrade reaction of 150 pci may be used for structural fill consisting of the native soils and a modulus of 250 pci may be used for structural fill consisting of crusher fines, pit -run, or base course. Footings subject to frost should be at least 36 -inches below the finished grade. As discussed previously, water soluble sulfates were detected in the site soils in a concentration of 0.4%. This concentration represents a severe degree of potential sulfate attack on concrete exposed to the native soils. Type V cement is specified in accordance with the International Building Code (IBC) for this concentration of sulfates. However, Type V cement can be difficult to obtain in some areas. Where Type V cement is unavailable, Type 1 -II cement is recommended. Retaining Walls Any stemwalls or retaining walls should be designed to resist lateral earth pressures. For backfill consisting of the native soils or imported granular, non -free draining, non -expansive material, we recommend that the walls be designed for an equivalent fluid unit weight of 55 pcf in areas where no surcharge loads are present. Lateral earth pressures should be increased as necessary to reflect any surcharge loading behind the walls. As discussed previously, the site is located above large modular block retaining walls to the east and south. In general, these types of walls include geogrid reinforcement. However, HBET does not have wall details and does not know how far the reinforcement extends behind the wall. In general, cutting or otherwise impacting the geogrid reinforcement is not recommended. It may be necessary to move the structure foundations in order to avoid impacting the geogrid reinforcement. In addition to geogrid reinforcement considerations, HBET does not have any information regarding the wall design. It is likely that the wall design included a surcharge for structure construction above the wall; however, this information is unknown. It is recommended that the wall designer be contacted to verify that the wall is capable of supporting a surcharge equal to the allowable bearing capacity of 2,000 psf. X:\2008 ALL PROJECTS \01456. RM Construction\01456-0001 Lot 287 lronbridge\200 - Geo \01456-0001 LR071715.doc 3 Lot 287 Ironbridge #01456-0001 07/17/15 Huddleston -Berry rrpinax410 7c R. llt Floor Slab and Exterior Flatwork Recommendations In order to limit the potential for excessive differential movements of slabs -on -grade it is recommended that non-structural floor slabs be constructed above a minimum of 12 -inches of structural fill with subgrade preparation and fill placement in accordance with the Foundation Recommendations section of this report. It is recommended that exterior flatwork be constructed above the native soils, below the topsoil, that have been scarified to a depth of 12 -inches, moisture conditioned, and compacted to a minimum of 95% of the standard Proctor maximum dry density, within ± 2% of the optimum moisture content as determined in accordance with ASTM D698. Drainage Recommendations Grading around the structure should be designed to carry precipitation and runoff away from the structure. It is recommended that the finished ground surface drop at least twelve inches within the first ten feet away from the structure. Downspouts should empty beyond the backfill zone. It is also recommended that landscaping within five feet of the structure include primarily desert plants with low water requirements. In addition, it is recommended that irrigation within ten feet of foundations be minimized. As discussed previously, groundwater was not encountered at the time of the investigation. However, if a structural floor and crawlspace is proposed, a perimeter foundation drain is recommended. In general, the perimeter foundation drain should consist of prefabricated drain materials or perforated pipe and gravel systems with the flowline of the drain at least one foot below the bottom of the foundation (at the highest point). The perimeter drain should slope at a minimum of 1.5% to daylight or to a sump. General Notes The recommendations included above are based upon the results of the subsurface investigation and on our local experience. These conclusions and recommendations are valid only for the proposed construction. As discussed previously, the subsurface conditions at the site were slightly variable. However, the precise nature and extent of any subsurface variability may not become evident until construction. As a result, it is recommended that a representative of HBET observe the foundation excavation prior to structural fill placement to verify that the subsurface conditions are consistent with those described herein. In addition, it is recommended that a representative of HBET test compaction of structural fill materials. Also as discussed previously, the site lies in an area of previous sinkhole activity associated with the Eagle Valley Evaporite. While no surface or subsurface evidence of solution activity was observed at the site and HBET believes that the risk of sinkhole formation at this site is low, geotechnical borings only provide subsurface information at a point. HBET believes that the subsurface investigation was generally adequate and in accordance with the standard -of -practice in the area; however, a full risk assessment would require additional borings and 3D seismic tomography or other geophysical methods. . As a result, HBET makes no warranty, either expressed nor implied that solution activity associated with the Eagle Valley Evaporite will not adversely impact the site in the future. X:\2008 ALL PROJECTS\01456 - RM Construction\01456-0001 Lot 287 lronbridge\200 - Geo\01456-0001 LR071715.doc 4 Lot 287 Ironbridge #01456-0001 07/17/15 Huddleston -Bene ^.3S Tt•*.n;. tit We are pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report. Respectfully Submitted: Huddleston -Berry Engineering and Testing, LLC Michael A. Berry, P.E. Vice President of Engineering X:'\2008 ALL PROJECTS \01456 - RM Construction\ 01456-0001 Lot 287 lronbridge,200 - Geo 01456-0001 LR071715. doe 5 FIGURES E co a) 0 CD N CO APPENDIX A Typed Boring Logs yvr , CLIENT PROJECT En,n cox+' RM fb"litld) d�\lhn‘31c1nuueE, tnlknt ec3ring & e>tin,. 1 LC IGrandJunction, CO 81501 1970-255-81)05 970-255-6313 Construction PROJECT NAME LOCATION BORING N UMBER B-1 PAGE 1 OF 1 Lot 287 Ironbridge NUMBER 01456-0001 PROJECT Glenwood Springs, CO DATE DRILLING DRILLING LOGGED NOTES STARTED CONTRACTOR METHOD BY Gravel 6/23/15 COMPLETED 6/23/15 GROUND ELEVATION WATER TIME OF END OF DRILLING HOLE SIZE S. McKracken GROUND LEVELS: DRILLING DRILLING Dry Simco 2000 Truck Rig AT CM CHECKED BY MAB AT Dry at 5 Ft AFTER --- I -- 0 v Q O 0 MATERIAL DESCRIPTION SAMPLE TYPE NUMBER RECOVERY % (ROD) BLOW COUNTS (N VALUE) POCKET PEN. (tsf) DRY UNIT WT. (pcf) MOISTURE CONTENT (%) ATTERBERG LIMITS FINES CONTENT (%) o 1- — =! J PLASTIC LIMIT H p In Z Q a A Lean CLAY with Sand (CL), red, dry to moist, very stiff SS 78 10-214-8 2) 7 28 17 11 75 10 lifr� i; .f�� �g 4.42 Kew _ Clayey GRAVEL (gc), red, moist, medium dense SS 56 5-6-8 (14) 15 vLean _ CLAY with Sand and Gravel (CL), red to brown, medium stiff to hard x 3S 56 20-21 20 SS 4 100 12-7-12 (19) 25 A XS5 100 4(6)3 12 21 10 11 73 SS 6 67 15-15-23- (338 ) . Bottom of hole at 28.5 feet. r. 0 a Eq 1luddteston-Berry En•`ineCring& 7e ting, I.LC BORING NUMBER B-2. ' "\ 610 \\ bite Avenue. Unit B , (i u 1 d Junction. CO 81501 PAGE 1 OF 1 ,..„•: 970-255-8005 `ra s 970-255-6818 CLIENT RM Construction PROJECT NAME Lot 287 Ironbridge PROJECT NUMBER 01456-0001 PROJECT LOCATION Glenwood Springs, CO DATE STARTED 6/23/15 COMPLETED 6/23115 GROUND ELEVATION HOLE SIZE DRILLING CONTRACTOR S. McKracken GROUND WATER LEVELS: DRILLING METHOD Simco 2000 Truck Rig AT TIME OF DRILLING Dry LOGGED BY CM CHECKED BY MAB AT END OF DRILLING Dry NOTES Gravel at 3 Ft, Auger Refusal at 38 Ft AFTER DRILLING --- a a z W o ATTERBERG LIMITS F- w i ~"l O 0 U ap 7 MATERIAL DESCRIPTION }} F -w J2 az2 V7 cr >0 cc ~P On< o w d w . OL- ll. F_. - z o- 0 DF- tw 2O 0 gt- 2- _:i Fv—,t- _ tl tr_- U 9 a_ Z� Oo w L - very stiff %' Sandy Lean CLAY with Traces of Gravel (cl), red to brown, moist, MC 17-16-16 e(gc), red to brown, moist, dense '��6 Clayey GRAVEL Y� 1 89 (32) 106 5 E� 10 �`►� SS 89 5-19-24 Sandy Lean CLAY red to brown, moist, medium stiff to hard 1 (43) (cl), 15 2S 56 12-20 9 20 XS3 89 2-5-6 (11) L 9_ 1J- 25 z LI - Silty SAND with Gravel (sm), red to brown, moist, loose to medium dense SS X 4 22 8-6-4 (10) Y n D y 30 • o D of - 8_ Q O - z 35 . m or m- __ +. I. !' Sandy GRAVEL and COBBLES (gw), brown, moist, dense w a o o Bottom of hole at 38.0 feet. 1 z n. 0 0 0 0 --- CLIENT PROJECT (.1kilt‘I‘Ichsitirmi,-\1‘3ll'irEniiiiti.winit & firistin. 1 LC ,1, 1Cm itud Junction. CO 8150 I - 970-255-8005 co, 970-255-6818 RM Construction PROJECT NAME LOCATION BORING NUMBER B-3 PAGE 1 OF 1 Lot 287 Ironbridge NUMBER 01456-0001 PROJECT Glenwood Springs, CO DATE DRILLING DRILLING LOGGED NOTES STARTED CONTRACTOR METHOD BY Auger 6/23/15 COMPLETED 6/23/15 GROUND ELEVATION WATER LEVELS: TIME OF DRILLING END OF DRILLING DRILLING HOLE SIZE Dry S. McKracken GROUND Simco 2000 Truck Rig AT CM CHECKED BY MAB AT Dry Refusal at 9 ft AFTER --- 9 DEPTH (ft) GRAPHIC LOG MATERIAL DESCRIPTION SAMPLE TYPE NUMBER RECOVERY % (RQD) BLOW COUNTS (N VALUE) POCKET PEN. (tsf) — c -i z u cit 0 .-- >- 0 MOISTURE CONTENT (%) LIQUID > LIMIT PLASTIC 12 r7T3 LIMIT 1=1 w ,u) m PLASTICITY INDEX FINES CONTENT (%) _ I_ 2.5 / Lean CLAY with Sand (c1), red, dry, very stiff - 5.0 '44 jer G • 4, Ili; Clayey GRAVEL (gc), red, moist, dense - 7.5 pe4,P, ift,41% e"..; rfr itio 4. r + .e4i , 4" , o e, 0 . - re 444er i Bottom of hole at 9.0 feet, APPENDIX B Laboratory Testing Results • - 0 q 3 W 0 z 0 r CO N 0 s ti z I lnddli:iton•flarc 1 tvinixtiu , 611) 1t )rite .1Aenue, 1_.`nit 11 Orand Junction, CO 81501 9751-35-800 970-3)5-6818 CLIENT RM Construction PROJECT NUMBER 01456.0001 e,tinr�, 11.( AIN SIZE DISTRIBUTION PROJECT NAME': lot 2$7 Ironbridjo PROJECT LOCATION Glenwood Sprint s, CO PERCENT FINER BY WEIGHT 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 U S. SIEVE OPENING IN NC! ES 1 U.S. SIEVE NUN ©CRS 6 4 3 2 .5 1 3(4 11 2 3 4 6 810 14 16 20 30 40 50 60 100 140 200 HYDRO. IETER 100 10 GRAIN SIZE IN MILLIMETERS 01 0.01 0.001 COBBLES GRAVEL SAND SILT OR CLAY coarse fine coarse medium fine Specimen Identification Classification LL PL PI Cc Cu • B-1, SS1 6/2015 LEAN CLAY with SAND(CL) 28 17 11 1 B-1, SS5 6/2015 LEAN CLAY with SAND(CL) 21 10 11 • Composite 6/2015 SANDY LEAN CLAY(CL) 26 17 9 Specimen Identification D100 D60 D30 D10 %Gravel %Sand • B-1, SS1 6/2015 9.5 1.0 23.5 1 13-1, SS5 6.2015 9.5 0.8 25.8 A Composite 6/2015 12.5 7.4 28.7 %Silt %Clay 75.4 73.3 63.8 xGlY 0� CLIENT ER�f Huddleston -Bern Engineerin t & Testing. I.I,(' ATTERBERG LIMITS' RESULTS ---°: 6c4=1jiile ;\venue, Unit .: Junction, C(7 31>01 970-255-3005 •- 970-255-6313 RM Construction PROJECT NAME Lot 287 Ironbridge PROJECT NUMBER 01456-0001 PROJECT LOCATION Glenwood Springs, CO 60 CL CH 50 P L A s 40 T I C I T 30 Y I N 20 D E X X • 10 CL -ML 10 MH 0 0 20 40 60 80 100 LIQUID LIMIT Specimen Identification LL PL PI #200 Classification • B-1, SS1 6/2015 28 17 11 75 LEAN CLAY with SAND(CL) MI B-1, SS5 612015 21 10 11 73 LEAN CLAY with SAND(CL) A Composite 6/2015 26 17 9 64 SANDY LEAN CLAY(CL) i D 5 S 7 5 L I> e u 9 Y a L 7 e a N J .t 13 O O N (_ 2 PD Ill CO WrC a ��g�' CLIENT nmuiQ,wo*uouTimc,inm Toting., LTC ��Kl���.��} V\yK[|�1�! -[i�r` . ^|oxhi/e/v"m�0`ko ~~^'^^ ^ '^^' '^ `^'�'� Gland /uimim(n x|m| 970-255-805 970-7 55-6318 ��'� RM Cvn«tructiunPROJECT NAME id 28 Ironbridc __.... __ PROJECT NUMBER 014nO-oVn-1 PROJECT LOCATION Glenwood Sprinqs, CO OO 0.5 1.0 gsz 1.5 fx 2.0 2.5 3.0 100 1,000 10.000 STRESS, psf Specimen Identification Classification Y MC% • B-2 2.5 88 22 t : CLILNT 1loakileston-I3in\ In ui:_criu \' T,Nin!!. 11.C° Moiti .,:! H '1 a"d.)!, NSII A REI A 1 IONSHIP " )Grand Junction. CO 81501 f 970-)55-8005 _c� 97025 -6318 RM Construction PROJECT NAME Lot 287 Ironbridge PROJECT NUMBER 01458-0001 PROJECT LOCATION Glenwood Springs. CO 150 Sample Date: 6123/2015 Sample No.: Source of Material: Composite 145 SANDY LEAN CLAY(CL) Description of Material: Method: ASTM D698A Test 140 TEST RESULTS 135 Maximum Dry Density 119.0 PCF Water Content 12.5 % Optimum 130 \N RESULTS(% PASSING) NGRADATION #200 #4 3/4" Pk 64 93 100 125 3 0. LIMITS DRY DENSI N O ATTERBERG LL PL PI /.1'..—..\illi 26 17 9 115 Curves of 100% Saturation for Specific Gravity Equal to: 2.80 �� 110 2.70 iklinkI 2.60 105 d 0 LI 0 W liaK 100 m z 0 g m tvI- 0 95 \ ii iiiii \ z 0 90 T-- 0 0 5 10 15 20 25 30 a v WATER CONTENT, %