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HomeMy WebLinkAboutSoils Report 08.08.20165020 Road 154 Glenwood Springs, CO 81601 Geotechnical Engineering I Engineering Geology Phone: (970) 945-7988 Materials Testing 1 Environmental Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 26, SUN MEADOW ESTATES SOUTH MEADOW DRIVE GARFIELD COUNTY, COLORADO PROJECT NO. 16-7-272 AUGUST 8, 2016 PREPARED FOR: BRAD AND CARRIE CHURCH do A-1 HEATING & COOLING, INC. 2342 AIRPORT ROAD RIFLE, COLORADO 81650 cchurch@alheatinginc.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 2 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 2 - DESIGN RECOMMENDATIONS - 3 - FOUNDATIONS - 3 - FLOOR SLABS - 4 - UNDERDRAIN SYSTEM - 5 - SURFACE DRAINAGE - 5 - LIMITATIONS - 6 - FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 3 - SWELL -CONSOLIDATION TEST RESULTS TABLE 1 - SUMMARY OF LABOROATRY TEST RESULTS PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 26, Sun Meadow Estates, South Meadow Drive, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Brad and Carrie Church dated July 28, 2016. Hepworth-Pawlak Geotechnical, Inc. (now H -P/ Kumar), previously performed a preliminary geotechnical study for Sun Meadow Estates (formerly Mamms View) and presented our findings, in a report, dated March 28, 2000, Job No. 100 169. A field exploration program consisting of one exploratory boring located in the designated building area was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed residence will be single story wood frame construction above a crawlspace in the living area and have an attached garage with slab -on -grade floor. There will also be a separate shop building with a slab -on -grade floor. Grading for the structure is assumed to be relatively minor with cut depths between about 3 to 5 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recommendations contained in this report. 2 SITE CONDITIONS Lot 26 is located on the southeast corner of South Meadow Drive and Antonelli Lane and was vacant at the time of our field visit. The lot is bordered to the east and south by Lots 26 and 33, respectively. The building area designated to us by the client is located in the middle of the lot. Vegetation consists of grass and weeds. The ground surface in the building area is small hilltop, sloping away in all directions. Predominantly the ground surface is moderately sloping down to the south. FIELD EXPLORATION The field exploration for the project was conducted on July 28, 2016. One exploratory boring was drilled in the designated building area at the approximate location shown on Figure 1. The exploratory boring was advanced with 4 -inch diameter continuous flight augers powered by a truck -mounted CME -45B drill rig. The boring was logged by a representative of H-P/Kumar. Samples of the subsoils were taken with I3i inch and 2 inch I.D. spoon samplers. The samplers were driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered a the site is shown on Figure 2. The subsoils, below about a half to one foot of topsoil, consist of very stiff to hard sandy silt and clay down to about 151 feet overlying medium dense to dense, silty to clayey -3 - sand with scattered cobbles and relatively dense gravel and sand lenses to the depth explored of 36 feet. Laboratory testing performed on samples obtained from the boring included natural moisture content and density and finer than sand size gradation. Results of swell - consolidation testing performed on relatively undisturbed drive samples of the silt and day soils, presented on Figure 3, indicate low compressibility under conditions of light loading and existing moisture conditions with one sample showing a minor swell potential when wetted and the other showing a minor collapse potential (settlement under constant load) when wetted. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist to moist. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring, the nature of the proposed construction and the soils typical of this area, the building can be designed with spread footings bearing on the natural soils with a risk of movement mainly from wetting of the bearing soils. The settlement/heave potential of the bearing soils should be further evaluated at the time of construction. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural soils should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect initial settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. There could be additional differential movement of if the bearing soils become wetted. The amount of settlement would be related to the depth and extent of wetting. Care -4 - should be taken to reduce the risk of wetting as discussed in the Surface Drainage section. 2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 36 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 55 pcf. 5) The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the undisturbed natural soils. The exposed footing subgrade soils should be further evaluated at the time of construction. 6) A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FLOOR SLABS The natural silt and clay soils have variable settlement/heave characteristics. 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. 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 should consist of imported granular soils devoid of vegetation and topsoil. -5 UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of 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 and crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. An underdrain should not be needed around the crawlspace provided the crawlspace is less than 3 feet deep and exterior foundation wall backfill is well compacted and the surface has a positive slope away from the building as described below in the Surface Drainage section. If drains are installed, they 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 I% 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 1'h feet deep. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: I) 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 -6 - 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 paved 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 10 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irrigation. 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 boring drilled at the location indicated on Figure 1, 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 boring 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 so that 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 -7 - bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, H-P%KUMAR Nkm -filtaz Shane M. Mello Reviewed by: Daniel E. Hardin, P.E. S MM/ksw 1 3 RE I1 I. •�{'�ifL lrt C L l-L�—•lr1— ill I * ; LOT 1 a II. aCIt AIL lil WLlII% Efl� lfl •jt 1y,�riJ 9L rt ii r r I 1 r Septic Tek 0 BORING 1 • r i v1.4 l� • Shop LT 30 0 30 60 APPROXIMATE SCALE -FEET LEGEND O BORING PREVIOUSLY DRILLED BY HEPWORTH PAWLAK GEOTECHNICAL, INC. UNDER JOB NO. 100-169 • BORING DRILLED FOR THIS PROJECT 16-7-272 H-PKUMAR LOCATION OF EXPLORATORY BORING Fig. 1 DEPTH-FEET V 1 1 1 q 1 0 5 10 15 BORING 1 LEGEND / 21/12 WC=7.8 1 J D0=112 ///313/12 WC=5.3 / 013=101 -200=87 42/12 WC=4.7 / 00=115 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 21 BLOWS OF A r 21/12 140 -POUND HAMMER FALIJNG 30 INCHES WERE REQUIRED TO DRIVE THE CAUFORNIA OR SPT SAMPLER 12 INCHES. 7 7 • -r TOPSOIL; ORGANIC SILTY SANDY CLAY WITH GRAVEL, FIRM, SLIGHTLY MOIST, DARK BROWN. SILT AND CUY (ML -CL); SANDY STIFF TO HARD, SLIGHTLY MOIST, REDDISH BROWN. SAND (SII -SC); SILTY TO CLAYEY, WITH SCATTERED COBBLES, WITH LENSES OF SILTY SAND AND GRAVEL, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST TO MOIST, BROWN. RELATIVELY UNDISTURBED DRIVE SAMPLE; 2 -INCH I.D. CAUFORNIA UNER SAMPLE. DRIVE SAMPLE; STANDARD PENETRATION TEST (SPT), 1 3/8 INCH I.D. SPUT SPOON SAMPLE, ASTM 13-1586. J� 20 16/12 2 46/12 WC=5.1 00=114 -200=54 25 f . 30 16/12 44/12 NOTES I. THE EXPLORATORY BORINGS WERE DRILLED ON JULY 28, 2016 WITH A 4 -INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5, THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (X) (ASTM D 2216); • DD = DRY DENSITY (pci) (ASTM D 2216); -200 = PERCENTAGE PASSING 140. 200 SIEVE (ASTM D 1140). 35 . � 19/12 40 16-7-272 H -P KUMAR LOG OF EXPLORATORY BORING Fig. 2 n X 1 d 111 O I§ 4 -1 a 0 M 0 N —2 z 0 C] i CONSOLIDATION - SWELL — 3 1 0 —1 — 2 — 3 SAMPLE OF: Sandy Silt and Clay FROM: Baring 1 0 2.5' WC = 7.8 X, DD = 112 pcf ADDITIONAL COIAPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING .I 1.0 APPUEO PRESSURE - KSF 10 100 SAMPLE OF: Sandy Silt and Clay FROM: Baring 1 0 10' WC = 4.7 X, DD » 115 pcf .1 Th_. ,... .y .. a. .": wK� `r at in 14. siert lbs rIllui ibbrovel 10 . Ww .fir �{Ii "o-1$ L " EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1.0 APPLIED PRESSURE - KSF 10 100 16-7-272 H-P� KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 3 Job No. 16-7-272 SOIL OR BEDROCK TYPE Sandy Silt and Clay Sandy Silt and Clay Sandy Silt and Clay Sandy Silt with Gravel UNCONFINED COMPRESSIVE STRENGTH (PSF) 0a X 5 -- b ATTER@EI si a� IT 7 PERCENT PASSING NO. 200 SIEVE 87 54 1 z 0 Q 0 re w 0 _ a a. u) GRAVEL (%) NATURAL DRY DENSITY (pcQ N•1- .- - Q Sll —CC NATURAL MOISTURE CONTENT (%) rel 4.7 .—. LOCATION d 0 z 0 cm