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HomeMy WebLinkAboutSoils Report 02.26.2020I (+A Kumar & Associates, Inc. Geotechnical and Materials Engineers and Environmental Scientists 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com An Employee Owned Company www.kuntarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado February 26, 2020 Peak 3 Construction + Development Attn: Jeff Claflin 601 East Hopkins Avenue, Suite 202 Aspen, Colorado 81611 jeff@peak3aspen.com CEIVE t 1h fm Project No.19-7-706 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot E-14, Aspen Equestrian Estates, 43 Equestrian Way, Garfield County, Colorado Gentlemen: As requested, Kumar & Associates, Inc. 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 Peak 3 Construction + Development dated November 29, 2019. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed residence will be a two-story structure with an attached garage and configuration as shown on Figure 1. Ground floor will be structural over crawlspace in the residence area and slab -on -grade in the garage area. Cut depths are expected to range between about 3 to 4 feet. Foundation loadings for this type of construction are assumed to be relatively light 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 lot was vacant at the time of our site visit. The lot is flat, slopes slightly down to the south and is vegetated with grass and weeds. Eagle Valley Evaporite bedrock is exposed on the valley hillsides to the north and south. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating three exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are -2 presented on Figure 2. The subsoils encountered, below about 2 feet of topsoil, consist of sandy silty clay to depths between 4 and 6 feet. Relatively dense, slightly silty sandy gravel and cobbles was encountered below the clay typically to the maximum explored depths of 8 feet. Pit 1 encountered a layer of silty sandy clay from 6 to 7 feet. Results of swell -consolidation testing performed on a relatively undisturbed sample of sandy silty clay, presented on Figure 3, indicate low compressibility under existing moisture conditions and light loading and moderate compressibility when wetted and subjected to increased loading. Results of a gradation analysis performed on a sample of sandy gravel are shown on Figure 4. Free water was not observed in the pits at the time of excavation and the soils were moist to very moist with depth. It has been our experience in this area that groundwater commonly develops at around 4 feet below ground surface during the summer to fall irrigation season. Foundation Recommendations: Considering the subsoil conditions encountered in the , we recommend spread footings exploratory pits and the nature of the proposed construction placed on the undisturbed natural soil below the topsoil designed for an allowable soil bearing pressure of 1,500 psf for support of the proposed residence. The clay soils tend to compress when loaded and there could be post -construction foundation settlement of around 1 inch. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. The topsoil and loose disturbed soil encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. 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 heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 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 55 pcf for the on-site soil as backfill excluding organics and rock larger than 6 inches. Floor Slabs: The natural on-site soils, exclusive of 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 Kumar & Associates, Inc. Project No. 19.7.706 3 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 interior slabs to facilitate drainage. This material should consist of minus 2 -inch aggregate with less than 50% passing the No. 4 sieve and less than 2% 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 soils devoid of vegetation, topsoil and oversized rock. We recommend vapor retarders conform to at least the minimum requirements of ASTM E1745 Class C material. Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM E1745 Class A material. The vapor retarder should be installed in accordance with the manufacturers' recommendations and ASTM E1643. Underdrain System: Free water was not encountered during our exploration but it has been our experience in the area that groundwater can rise during irrigation season. We recommend below -grade construction, such as retaining walls and crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. 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 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet or sump and pump. Free -draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 11/2 feet deep. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence 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 Kumar & Associates, Inc. Project No. 19-7.706 -4 - and to at least 90% of the maximum standard Proctor density in landscape areas. Free -draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. 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 21/2 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. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. 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 Kumar & Associates, Inc. Project No. 19.7.706 -5 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, Kumar & Associates, Inc Steven L. Pawlak, P Reviewed by: Daniel E. Hardin, P.E. SLP/kac Attachments: Figure 1 — Location of Exploratory Pits Figure 2 — Logs of Exploratory Pits Figure 3 — Swell -Consolidation Test Results Figure 4 — Gradation Test Results Table 1 — Summary of Laboratory Test Results cc: Peak 3 Construction + Development — Bryant Ragan (hrvant(2 peak3aspen.com) Kumar & Associates, Inc. Project No. 19.7.706 507 505 506 503 502 501 NOT TO SCALE 19-7-706 508 515 553 554 555 510 511 512 509 513 552 504 551 550 526 500 Kumar & Associates 524 525 520 • • 523 522 521 557 556 516 518 517 LOCATION OF EXPLORATORY PITS Fig. 1 a G t el 1- w x 1- a w 0 0 5 PIT 1 WC=20.7 DD=103 PIT 2 WC=15.8 DD=100 —200=37 PIT 3 1 +4=65 —1 —200=8 0 5 — - 10 10— LEGEND ElTOPSOIL, ORGANIC SANDY SILT AND CLAY, DARK BROWN. CLAY (CL); SILTY, SANDY TO VERY SANDY WITH DEPTH, STIFF, MOIST, BROWN, LOW PLASTICITY. GRAVEL AND COBBLES (GM—GP); SLIGHTLY SILTY, SANDY, DENSE, MOIST, BROWN, ROUNDED ROCK. HAND DRIVEN 2—INCH DIAMETER LINER SAMPLE. � DISTURBED BULK SAMPLE. J NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON FEBRUARY 24, 2020. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING AT THE CLIENT DESIGNATED LOCATIONS. 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. GROUND WATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF DIGGING. 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); 19-7-706 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2 .. 0 CONSOLIDATION - SWELL 2 3 4 5 10 APPLIED PRESSURE - KSF 10 100 19-7-706 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 3 SAMPLE OF: Sandy Silty Clay FROM: Pit 1 © 2' WC = 20.7 %, DD = 103 pcf I T i r NO MOVEMENT UPON WETTING 1 1 These test results apply only to the samples tested. The testing apart shall not be reproduced, ext pt in full, without the written approval of (Kumar and Associates, Inc Swell ICansolldotion testing performed in accordance with ASTM 0-4546 10 APPLIED PRESSURE - KSF 10 100 19-7-706 Kumar & Associates SWELL—CONSOLIDATION TEST RESULTS Fig. 3 HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS '14 HRS 7 HRS 45 YIN JS WN �IIN 191119 4141N 1 IN Yk00 U.S. STANDARD •100 1 . 140 2 SERIES !_ 6 2 IS CLEAR SOUARE OPENINGS 3 3 0 1 1/7." S"Ik {I " a 100 F sssssssssAl 1 90 ME =El 10 t ■�Mf BO I-- 20 r ME W t s0 70 r I { 60 r I- I 40 V IINF' J B 1 1 50 r r 1 50 1 8 fdl �a 60 40 ! Wif � se 30_ p 70 20 _ - 80 ---! II 7 t 10 90 — – PW 0 1 1 1 1 1 F 1 -_ 100 .001 .002 .003 .904 .016 .037 .075 .150 .50o DIAMETER OF PARTICLES f .600 .423 1. IN MILLIMETERS 3 1 2.36 4.75 2 2:0 3 19 36.1 76.2 127 152 200 SAND GRAVEL CLAY TO SILT FINE MEDIUM COARSE FINE I COARSE COBBLES GRAVEL 65 % SAND 27 % SILT AND CLAY 8 LIQUID LIMIT PLASTICITY INDEX SAMPLE OF: Slightly Silty Sandy Gravel FROM: Pit 3 ® 5'-6' These test results apply only to the samples which were tested. The tesling report shall not be reproduced, except In full, without the written approval of Kumar & Associates, Inc. Sts9. anatysls tebHti IsI pert2rmed In accerdana4 wlth ASTM D0913, ASTM 07928, ASTM C136 and/or ASTM D1140. 19-7-706 Kumar & Associates GRADATION TEST RESULTS Fig. 4 K+A Kumar & Associates. Inc. Geotechnical and Materials Engineers and Emmonmanlal Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Pro ea No. 19.7.706 SAMPLE LOCATION NATURAL MOISTURE CONTENT ('X) NATURAL DRY DENSITY had) GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS PLASTIC (i) UNCONFINED COMPRESSIVE STRENGTH (Psi) SOIL TYPE PIT DEPTH (ft) GRAVEL (%) SAND (,') LIQUID LIMIT ll 1 2 20.7 103 Sandy Silty Clay 2 53/4 15.8 100 37 Very Silty Clayey Sand 3 5-6 65 27 8 Slightly Silty Sandy Gravel