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Home My WebLink AboutSoils Report 12.18.2018H-P�KUMAR 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 December 18, 2018 Brian and Jennifer Eades 810 Riley Lane Delta, Colorado 81416 clrr+ri anc:adesIgor' ail. corn Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado Project No. 18-7-691 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 20, Filing 9, Elk Springs Subdivision, Kingbird Drive, Garfield County, Colorado Dear Mr. and Mrs. Eades: 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 November 13, 2018. 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 over a crawlspace with an attached garage on the main level located on the site as shown on Figure 1. The garage floor will be slab -on -grade. Cut depths are expected to range between about 4 to 10 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 subject site is currently vacant. Topography is moderately to strongly sloping terrain down to the south at grades of around 20 percent in the building area and around 10 to 15 percent to the north of the building area. There is around 14 feet of elevation difference over the proposed building area. Vegetation at the site consists of native grass, sagebrush, and juniper trees. There is a dry drainage to the south of the lot. 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 presented on Figure 2. The subsoils encountered, below about 1 foot of topsoil, consist of basalt cobbles and boulders in a cemented sandy silty gravel matrix down to the maximum depth explored of 3 feet. A 11/2 foot thick layer of sandy silt and clay was encountered in Pit 2 -2 - overlying the basalt cobbles and boulders. Digging in the dense basalt gravel cobble and boulder material was difficult and refusal was encountered in the deposit. Results of a gradation analysis performed on a sample of slightly silty sandy gravel (minus 5 inch fraction) obtained from the site are presented on Figure 3. 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 granular soils designed for an allowable soil bearing pressure of 2,000 psf for support of the proposed residence. The sandy silty gravel matrix soils tends to compress after wetting and there could be some post -construction foundation settlement. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils and all upper clay and silt soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural granular basalt rock soils. Voids created from boulder removal at footing grade should be backfilled with concrete or a structural material such as road base compacted to at least 98 percent standard Proctor density at a moisture content near optimum. 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 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 be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill. Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly to moderately 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 free -draining gravel should be placed beneath basement level 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. H-P*KUMAR Project No. 18-'7-691 Underdrain System: -3- Although free water was not encountered during our exploration, it has been our experience in mountainous areas that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. 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. 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 and to at least 90% of the maximum standard Proctor density in landscape areas. Free -draining wall backfill should be 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 12 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. A swale may be needed uphill to direct surface runoff around the residence. 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 H-P-KUMAR Project No. 18-7-691 -4 - 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 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 KUMAR Povie44 Robert L. Duran, €I. Reviewed by: • vr��^u ;a 24443 z1 Daniel E. Hardin, P. 4-0% +y,7. u/ � ; RLD/kac (1.°A" -- `�• � attachments Figure 1 — L6 1..:&dattosvetxploratory Pits Figure 2 — Logs of Exploratory Pits Figure 3 — Gradation Test Results Table 1 — Summary of Laboratory Test Results cc: Patrick W. Stuckey Architects — Patrick Stuckey (stucarch(u.comcast.nct) H-PIKUMAR Project No. 18-7-691 Ji til:4_'f til 1 II... , PIT 2 20 APPROXIMATE SCALE 40' 18-7-691 H -P - KU MAR Geotechnical Engineering 1 Englneonng Geology Melerials Tesllno 1 Environmental LOCATION OF EXPLORATORY PITS Figure 1 La w H La — 0 PIT 1 EL. 989.5' N. •t. .ti 1' PIT 2 EL. 996' PIT 3 EL. 985' -I WC=4.9 +4=74 -200=6 0- -- 5 5 LEGEND TOPSOIL, SAND AND SILT, CLAYEY, LOOSE, MOIST, BROWN, ORGANIC. i BASALT COBBLES AND BOULDERS (GM); IN A LIGHTLY CEMENTED SANDY SILTY GRAVEL MATRIX, DENSE, SLIGHTLY MOIST, WHITE, CALCAREOUS. CLAY AND SILT (CL -ML); SANDY, SCATTERED GRAVEL, MEDIUM STIFF, MOIST, BROWN. SI HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE. PRACTICAL DIGGING REFUSAL. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON NOVEMBER 19, 2018. 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 OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS 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. 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); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422); -200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). 1- w w Lt I a w 18-7-691 H-P--14KUMAR LOGS OF EXPLORATORY PITS Fig. 2 0 e 100 e0 BO 70 00 50 40 30 20 10 HYDROMETER ANALYSIS SIEVE ANALYSIS 34 HRS 47 MIH 7 NRS 1006H 4' TIME READINGS N 'tole_ SII! .1111N an. !lq4 U.I. -iRl42414 SI NOARO SERIES /.8 lir PA 04 _ � 3 CLEAR P" 3L+ _ ,._ SQUARE 1.112' OPENINGS �. Y -'6' B'a to - - - — - � - -- T --- _i... _ . – -- -- – — - – — — - ---- .J. 30 L. _1_ sG ---1- -- I _} -1-- i- BO eG — 1 0 1 1 1 1 1 x.037 I l l r 1 1 1.07201 1 1 10 - 1) 1 1 T . 1 1 14.16 Ll l a 1 .1F 1 1541-. F- I T.1 ': 1 GI .002 dddbbbSS5 b6n .all .073 .100 DIAMETER OF PARTICLES .425.103* s. IN MILLIMETERS B O3.se 4.72 a a 1e 35.1 s.7 14; 132 SAND GRAVE L COBBLES CLAY TO SILT FINE MEDIUM COARSE- FINE I COARSE GRAVEL 74 % SAND 20 X LIQUID LIMIT PLASTICITY INDEX SAMPLE OF: Slightly Silty Sandy Grovel Matrix SILT AND CLAY 6 X FROM: PO 3 0 2'-3' Thews feel remade apply only to the romplee which wore fooled. The lerllnp report shall not hs reproduced, except 1n Tull, WUHloul the wrHHen approval af Kumar & Areeelolse, Inc. Mews anolyerr feeling Isperformed In accordance with ASTM 0422, ASTM C136 and/or ASPM 01140. 18-7-691 H-P45KUMAR GRADATION TEST RESULTS Fig. 3 H-PKUMAR TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 18-7-691 SAMPLE LOCATION NATURAL MOISTURE CONTENT (%) GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH (Psf) SOIL TYPE PIT DEPTH (ft) NATURAL DRY DENSITY (Pco GRAVEL (%) SAND (%) UQUID LIMIT (°/u) PLASTIC INDEX (%) 74 20 6 Slightly Silty Sandy Gravel Matrix 3 2-3 4.9