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Home My WebLink AboutSoils Report 06.30.2017H -PKU MAR Geotechnical Engineering 1 Engineering Geology Materials Testing 1 Environmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com June 30, 2017 Bill Holland 0348 Shoshoni Silt, Colorado 81652 (brholl and @ p eoplepc.com ) Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado Project No. 17-7-440 Subject: Subsoil Study for Foundation Design, Proposed Shop Building, Lot 19A, Mineota Estates, 0348 Shoshoni, Garfield County, Colorado Dear Mr. Holland: As requested, H-P/Kumar performed a subsoil study for design of foundations at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to you dated June 8, 2017. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed shop building will be a single story steel frame and metal structure with a slab -on grade floor at a finish elevation at to slightly above the existing ground surface. The shop building will be located on the lot as shown on Figure 1 and the 0348 Shoshoni residence is at the adjacent lot to the north. Cut depths are expected to range between about 2 to 3 feet. Foundation loading for this type of construction is assumed to be relatively light to moderate and typical of the proposed type of construction. If building conditions or foundation loadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The property is vacant and vegetated with juniper trees, sage brush and grass and weeds. The ground surface is relatively flat with a slight slope down to the north. The building area has been cleared of vegetation and cut up to 4 feet below the surrounding grade. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, consisted of medium dense to dense, silty sand and gravel with cobbles. Stiff, sandy silty clay was encountered below the sand and gravel soils in Pit 1 at a depth of 6 feet. Results of swell -consolidation testing performed on a relatively undisturbed sample of the sandy silty clay, presented on Figure 3, indicate low compressibility under existing moisture conditions and light loading, and a low expansion potential when wetted under a constant light surcharge. Results of a gradation analysis performed on a sample of the -2 - silty sandy gravel with cobble soils (minus 5 inch fraction) obtained from Pit 2 are presented on Figure 4. No free water was observed in the pits at the time of excavation and the soils were slightly moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings placed on the undisturbed natural granular soils designed for an allowable bearing pressure of 2,000 psf for support of the proposed shop building. The excavation for the foundation should be kept as shallow as possible due to the underlying clay soils that possess a low expansion potential when wetted. A minimum 3 feet of the sand and gravel soils should be maintained below the footings and over the clay soils. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Prior to the footing construction, all existing fill and any loose disturbed soils should be removed and the footing bearing level extended down to the undisturbed natural granular soils, and the subgrade moistened and compacted. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be well reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. 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 50 pcf for the on-site granular soils, excluding topsoil and oversized rocks, as backfill. A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. Floor Slabs: The natural on-site granular soils, exclusive of any topsoil, 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 control joints 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 road base should be placed beneath the floor slab for support and to facilitate drainage. If the slab will be moderately loaded, the base course thickness should be increased to 6 inches. This material should consist of minus 2 inch aggregate with less than 50% passing the No. 4 sieve and less than 12% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site granular soils devoid of topsoil and oversized (plus 6 inch) rocks. Underdrain System: It is our understanding the finished floor elevation at the lowest level is at or above the surrounding grade. Therefore, a foundation drain system is not required. It has been our experience in the area that local perched groundwater can develop during times of H-P%KUMAR Project No. 17-7-440 -3 - heavy precipitation or seasonal runoff. Frozen ground during spring runoff can also create a perched condition. We recommend below -grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain system. If the finished floor elevation of the proposed structure has a floor level below the surrounding grade, we should be contacted to provide recommendations for an underdrain system. All earth retaining structures should be properly drained. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the shop building has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in pavement and walkway areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1 and to the depths shown on Figure 2, the proposed type of construction, and our experience in the area. 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. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified at once so re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation H-Pk-KUMAR Project No. 17-7-440 -4 - of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. If you have any questions or if we may be of further assistance, please let us know. Respectfully Submitted, H -P KI. MAR Louis E. Eller Reviewed by: �r :.v q c ,, David A. Young,P.E. �° �" "s' , •;1 8 �s1fi ex �a, ►7 7-3 /7 LEE/ksw attachments Figure 1— Locatiari of Exploratory Pits Figure 2 — Logs of Exploratory Pits Figure 3 - Swell -Consolidation Test Results Figure 4 — Gradation test Results cc: Pattillo Associates — Bob Pattillo (bob@paengineers.com) H -P; KUMAR Project No. 17-7-440 EXISTING RESIDENCE 348 SHOSHONI PROPOSED SHOP BUILDING 150 0 150 300 APPROXIMATE SCALE—FEET PIT 1 PIT 2 PARCEL 19-A FILING 1 MINEOTA ESTATES SENECA DRIVE LOT 10 17-7-440 H-P--A5KUMAR LOCATION OF EXPLORATORY PITS Fig. 1 LJ w x �- a w 0 LEGEND — 0 r- - — 5 -- 10 PIT 1 WC=5.3 DD=117 –200=76 PIT 2 i +4=b3 _i –200=18 ECLAY (CL); SILTY, SANDY, VERY STIFF, MIXED BROWN, BLOCKY. 0- 5 — 5 10- 1- 0_ 0- 1— a w 0 SAND AND GRAVEL (SM–GM) WITH COBBLES, SILTY, MEDIUM DENSE, SLIGHTLY MOIST, LIGHT BROWN. GRAVEL (GM); WITH COBBLES, SANDY, SILTY, DENSE, SLIGHTLY MOIST, LIGHT BROWN. HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON JUNE 6, 2017. 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 8E GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcf) (ASTM D 2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422); –200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 17-7-440 H -PKU MAR LOGS OF EXPLORATORY PITS Fig. 2 CONSOLIDATION - SWELL 1 0 —1 — 2 — 3 — 4 17-7-440 1 U AFPLFED PRESSURE - KSF H-P---KUMAR 10 SWELL -CONSOLIDATION TEST RESULT 100 Fig. 3 SAMPLE OF; Sandy Silty Clay FROM: Plt 1 CP 7' WC = 5.3 %, DD = 117 pcf 1 .__..L._ ... ___ ___—.—_— • EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1 f 1� - 1 i_.. { 11 1 t j u,.i tf1,7 kktrk net e elptothicwiNOj,n M.wilhenl IM 11H14. el I[wr+ and Atleclplq, Incc Sre4 Concn endccs ft p.Kan5ASTAI46 in 17-7-440 1 U AFPLFED PRESSURE - KSF H-P---KUMAR 10 SWELL -CONSOLIDATION TEST RESULT 100 Fig. 3 HYDROMETER ANALYSIS SIEVE ANALYSIS 100 24 HRS 7 11115 N S_ A6 141AU4 TIME READINGS - _, 41414 1 1280 U.S. 0I�pD 1 STANDARD Q t f SERIES D 1r¢ ri3.411"3N P 6 14 CLEAR 3" SQUARE UfRM1IRS " 1 1/2" 1" a_ 1 111'0 r _ U.— 0 � T --I—+--- 1 1G eD _r 200 —1 1 I v0 30 1 1 I Sy 60 �1 40 8 ... _ Y. t & RC 8 50 1 I — 50 0. 40 i 60 W �7y 30 I I. I 70 —} 20 411 t J 80 1 10 - 1 1 1� .. _. Imo_ 0 81111 1 r 1 1 1 fr77—"--1 ZIT 1 L 1 L-1--`1-1. Y r 1 .rl 1 I.r 11 1 100 .001 .002 .888 .003 _014 .037 .075 ,160 .300 41 :WO 1. DIAMETER OF PARTICLES IN a 21 .36 4,75 9"-- 9 11 38.1 76.3 127 MILLIMETERS 200 ` SAND GRAVEL CLAY TO SILT FINE MEDIUM COARSE FINE COARSE COBBLES GRAVEL 63 % SAND 19 % SILT AND CLAY 18 LIQUID LIMIT PLASTICITY INDEX SAMPLE OF: Silty Sandy Gravel with Cobbles FROM: Pit 2 ® 4'-5' These test results apply only 10 the samples which were tested. The testing report shall not be reproduced, except In lull, without the written approval of Rumor & Associates, Inc. Steve analysts lading 13 portorrnad In ocoordortca with A53le 0422. ASTM CI 36 and/or ASTM 31140. 17-7-440 H -P- KUMAR GRADATION TEST RESULTS Fig. 4