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HomeMy WebLinkAboutSoils Report 10.19.2017H-PKUMAR Geotechnical Engineering 1 Engineering Geology Materials Testing 1 Environmental RECEIVEP DEC 202017 GARFIELD COUNTY )MMUNITY DEVELOPMENT 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs, and Summit County, Colorado October 19, 2017 Uriel Mellin 144 Cliffrose Way Glenwood Springs, Colorado 81601 uriel.mellin@hotmail.com Project No.17-7-695 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 2, Callicotte Ranch, 62 Meadow Point, Garfield County, Colorado Dear Uriel: 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 proposal for geotechnical engineering services to you dated September 14, 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 residence will be about 5,000 square feet, one story wood frame structure over a crawlspace located on the site as shown on Figure 1. Ground floor in the attached garage will be slab -on -grade. Cut depths are expected to range between about 3 to 9 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 site is currently vacant, gently rolling pastureland with pinon/juniper forest on the south side of the lot and sagebrush on the northern fence line. The lot slopes moderately down to the east at grades of 5 to 10 percent. An active irrigation ditch crosses the site above and west of the building area. A rough graded driveway accesses the lower part of the lot. -2 - Subsurface Conditions: The subsurface conditions in the building area 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 6 to 8 inches of topsoil, consist of 3 to 7 feet of stiff, sandy silty clay overlying basalt rocks in a sandy clayey silt matrix at 31/2 to 7 feet deep. Refusal to digging with the backhoe was encountered in all three pits at depths of 5 to 81 feet. Results of swell -consolidation testing performed on relatively undisturbed samples of the sandy silty clay, presented on Figures 4 & 5, indicate low to moderate compressibility under existing moisture conditions and light loading and a low collapse potential (settlement under constant load) when wetted. The clays were moderately compressible under increased loading after wetting. 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 clay soils designed for an allowable soil bearing pressure of 1,200 psf and footings placed on the basalt rock soils designed for an allowable soil bearing pressure pf 2,000 psf for support of the proposed residence. The clay soils tend to compress after wetting and there could be 1/2 to 11/2 inches of post -construction foundation settlement. Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns. Loose and disturbed soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. The exposed soils should then be 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 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 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 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 established by the designer based on experience and the intended slab use. A minimum 4 inch H-P�KUMAR Project No. 17-7-695 -3 - layer of free -draining gravel should be placed beneath 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. Underdrain System: Although free water was not encountered during our exploration, it has been our experience 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. 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 Ievel 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. An impervious membrane such as 20 mil PVC should be placed beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing soils. 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 H-P45KUMAR Project No. 17-7-695 -4 - inches in the first 10 feet in pavement and walkway areas. A swale may be needed uphill to direct surface runoff and possible irrigation ditch overflow away and 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 10 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the foundation caused by irrigation. Percolation Testing: Percolation tests were conducted on September 16, 2017 to evaluate the feasibility of an infiltration septic disposal system at the site. Two profile pits and three percolation holes were dug at the locations shown on Figure 1. The test holes (nominal 12 inch diameter by 12 inch deep) were hand dug at the bottom of shallow backhoe pits and were soaked with water one day prior to testing. The soils exposed in the percolation holes are similar to those exposed in the Profile Pits shown on Figure 2 and consist of silt loam. USDA gradation test results are shown on Figure 6. The percolation test results are presented in Table 2. Based on the subsurface conditions encountered and the percolation test results, the tested area should be suitable for a conventional infiltration septic disposal system. A civil engineer should design the infiltration septic disposal system. 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 H-P%KUMAR Project No. 17-7-695 -5 - 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 Daniel E. Hardin, P.. 24443/obo` Reviewed by: Steven L. Pawlak, P.E. DEH/kac attachments Figure 1 — Location of Exploratory Pits Figure 2 — Logs of Exploratory Pits Figures 3 — Legend and Notes Figures 4 and 5 — Swell -Consolidation Test Results Figure 6 — USDA Gradation Test Results Table 1 — Summary of Laboratory Test Results Table 2 — Percolation Test Results cc: Patrick Stuckey Architect stuarchC comcast.net H-PitKUMAR ProJect No. 17-7-695 FUME OLD Dara, 'ENrERLINE -"k7s OrT ON 0. '59313 No N84°40'35"E 289.32' (N84°40'12"E 289,30') N83653'29"E 255.72' ilialriNS INNIaswerir► .1azussai (N83°52'16"E 255.651 �•� • . 111//�><llltl� 1� y1lvolllcatRurriOlbiave ° riffr 7L grailb 1 0410M-11-4 it (L-;,-�. �►�r,:fit .�r�r ifirionkgs;ifr.-,;..-7.1,--lag it itAi Illitifrifr / 10' .�. : Edi:. -____,nt 'ittv.inrd$ii1IJ r�' LIQ '47�:>fil'i�''' g ON"Ftilil 4 '';;'iii ; — r� i=;, �pii .its �' r ►,,41,,+4,.griw ! pY Pyr 3 jfr��jj' ‘ ,,e,r 'Far P-*IP'w Nilifir 111 i l arrrMrielirrirrwnmis � � srttr� AF�� r3OMa 30 0 30 60 APPROXIMATE SCALE -FEET LOT 17-7-695 H-PvKUMAR LOCATION OF EXPLORATORY PITS Fig. 1 4 3 -.2 A e9 ELEVATION -FEET 1- LJ w z 0 > J H PIT 1 EL. 6837' PIT 2 EL. 6835' PIT 3 EL. 6823' 6840 6840 — 6835 6830 - 6825 WC=5.5 DD=100 WC=7.1 -200=91 WC=9.1 DD=96 -200=91 6835 6830 ----' 6825 — 6820 6820 -- - 6820 — 6815 6810 PROFILE PIT 1 EL. 6820' f PROFILE PIT 2 EL. 6816' H GRAVEL=4 _-1 SAND=21 SILT=63 CLAY=12 6820 6815 6810- - 6805 6805 17-7-695 H-PWUMAR LOGS OF EXPLORATORY PITS Fig. 2 LEGEND TOPSOIL; ORGANIC SANDY SILTY CLAY, FIRM, MOIST, DARK BROWN. CLAY (CL); SILTY, SANDY, STIFF, SLIGHTLY MOIST, BROWN. POROUS. BASALT ROCKS; FROM GRAVEL TO SMALL BOULDER SIZE, IN A SANDY CLAYEY SILT MATRIX, SLIGHTLY MOIST, WHITISH BROWN, CALCAREOUS. Sl HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE. _1 t PRACTICAL DIGGING REFUSAL. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON SEPTEMBER 15, 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 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 DIGGING. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcf) (ASTM D 2216); —200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140); GRAVEL = PERCENT RETAINED ON NO. 10 SIEVE SAND = PERCENT PASSING NO. 10 SIEVE AND RETAINED ON NO. 325 SIEVE SILT = PERCENT PASSING NO. 325 SIEVE TO PARTICLE SIZE .002mm CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002mm 17-7-695 H-PtiKUMAR LEGEND AND NOTES Fig. 3 J J — W tnz 0 0 o J 0 (/) z O U SAMPLE OF: Sandy Silty Clay FROM: Pit 1 0 4' WC = 5.5 %. DD = 100 pcf Thar falx ran . op* mei to lM OM*. lu 4 f1 l I'. fapaal ahpa nal he r,pmduma0. Osaka! fa, rIlneut ths rrglaa ayDroval wi Kumar men nrx7Msit Ina- 5.11 �nadrdalIen Ivenpp paHmewd wdm.as with A fl O'4 IL NO MOVEMENT UPON WETTING 17-7-695 1.6 APPLIED PRESSURE - KSF 1Q i H-P"-t-KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 4 CONSOLIDATION - SWELL — 2 — 3 — 4 Muss toot mole a w// to thm motet". lata/ IIu tioilroa nowt .fiw tint t. .p e/yc./, ..c.pt In !W, nNpyl YI. .011.1 epprcrpr ar K.rnt, aro Awoc:ofati 1nF $..11 Come•follan tooling. Wormy/ In accarde.c..ith ASU 0.046 SAMPLE OF: Slightly Sandy Silty Clay FROM: Pit 3 ® 3' WC = 9.1 %, DD = 96 pcf —200 = 91 % ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE - }(SF 10 100 17-7-695 H-P45KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 5 HYDROMETER ANALYSIS 1 SIEVE ANALYSIS f 24F1. n45MIN. TIME READINGS il-H 1MM1 15 W1. OW 1Sr@i IW1 #325 U.5. STANDARD SERIES 1 CLEAR SQUARE #140 #60 #35 # 8 # 0 OA 318' 3/4 1 OPENINGS /2' 3' S'$' 6' .__ PERCENT RETAINED 3 $ o o g S o' 8 8 o I V . A Cn 0) v m �p O O O O E S PERCENT PASSING 1 . _x2 i V.001 .002 .005 .009 ,019 045 106 .025 .500 1.00 2.00 4.75 95 ?9.0 3.5 762 152 203 6 DIAMETER OF PARTICLES IN MILLIMETERS CLAY SIL' COBBLES 51_'_,/,T FF1/WE6'.ii,.' OARSI; .Lf WA:ft ME01WS GRAVEL 4 % SAND 21 % SILT 63 % CLAY 12 % USDA SOIL TYPE: Silt Loam FROM: Profile Pit 2 @ 3-4' 17-7-695 H-P--KLJMAR USDA GRADATION TEST RESULTS Fig, 6 H-PKUMAR TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 17-7-695 SAMPLE LOCATION NATURAL NATURAL GRADATION PERCENT USDA SOIL TEXTURE PIT MOISTURE DEPTH CONTENT (n) (%) DRY DENSITY (PO i PASSING GRAVEL SAND NO. 200 SIEVE 1 (%) (%) GRAVEL SAND (%) (%) SILT CLAY (%) (%) SOIL TYPE 1 4 5.5 100 Sandy Silty Clay 2 3 7.1 91 Slightly Sandy Silty I Clay 3 3 9.1 96 91 Slightly Sandy Silty 1 Clay F Profile Pit 2 3_4 4 21 63 12 Silt Loam HOLE DEPTH (INCHES) 43 44 40 H-PKUMAR TABLE 2 PERCOLATION TEST RESULTS LENGTH OF INTERVAL (MIN) Water Added WATER WATER DEPTH AT DEPTH AT START OF END OF INTERVAL INTERVAL (INCHES) (INCHES) 53/4 43/4 43/4 41/4 PROJECT NO, 17-7-695 DROP IN WATER LEVEL (INCHES) 1 1/2 4'/4 4 1/4 4 33/4 1/4 61/2 51/2 1 51/2 5 1/2 AVERAGE PERCOLATION RATE (MIN./INCH) 5 4'/2 1/2 41/2 4 1/2 4 33/4 1/4 Water Added Water Added 5% 43/4 1 43/4 4'/4 2 4'/4 41/4 4'/4 4 t/4 61/2 6 1/2 6 5% 1/4 53/4 5'/2 1/4 51/2 5 1/2 5 41/2 1/2 24 24 51/2 5 1/2 5 41/2 1/2 41/2 4 4 31/2 1/2 1/2 5% 53/4 5'/4 4% 43/4 41/4 4'/4 —4 1/2 1/2 4 1/4 31/2 1/2 24 Note: Percolation test holes were hand dug in the bottom of backhoe pits and soaked on September 15, 2017. Percolation tests were conducted on September 16, 2017. The average percolation rates were based on the last three readings of each test.