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HomeMy WebLinkAboutSoils Report 11.28.2017H-PKUMAR Geotechnical Engineering I 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 Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado November 28, 2017 Mike Ruiz 775 Fir Avenue Rifle, Colorado 81650 mike.unicorp@gmail.com Subject: Gentlemen: Project No.17-7-798 Subsoil Study for Foundation Design and Percolation Test, Proposed Residence, Lot 7, Native Springs, 19 Native Springs Drive, Garfield County, Colorado As requested, H-P/Kumar performed a subsoil study for foundation design at the subject site. The study was conducted in general accordance with our agreement for geotechnical engineering services to Mike Ruiz, dated October 24, 2017. The agreement was changed to include a percolation test for septic disposal system design information. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Hepworth-Pawlak Geotechnical (now H-P/Kumar) previously conducted a preliminary geotechnical study for the subdivision development and presented the findings in a report dated January 16, 2001, Job No. 100 460. Proposed Construction: The proposed residence will be a single -story structure with slab -on - grade floor located on the site as shown on Figure 1. Cut depths are expected to range between about 2 to 6 feet below existing ground surface including about a 3 -foot deep cut into the slope behind the residence. Foundation loadings for this type of construction are assumed to be relatively light and typical of the proposed type of construction. The septic disposal system is proposed to be located southwest of the residence. 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 building site was vacant at the time of our study and consists of a fallow grass field. The ground surface slopes gently down to the southeast with about 3 to 4 feet of -2 - elevation difference across the building footprint. The grade steepens somewhat upslope to the northwest of the building site at a grade of about 10 to 15%. A dry irrigation ditch traverses the steep slope just above the lot. Vegetation consists of grass and weeds. Subsurface Conditions: The subsurface conditions at the site were evaluated by observing 2 exploratory pits in the building area and two profile pits in the septic disposal area at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about l to 1 foot of topsoil, consist of stiff, sandy silty clay to the pit depths of 7 to 8 feet. Results of swell -consolidation testing performed on relatively undisturbed samples of the clay soils, presented on Figures 3 and 4, indicate low compressibility under existing moisture conditions and light loading and a low to moderate compressibility under additional loading after wetting. Some of the soils are slightly porous and can have a collapse potential when wetted under load. Results of gradation analyses performed on samples of soils obtained from the septic disposal area pits are presented on Figures 5 & 6. The laboratory test results are summarized in Table 1. No free water was observed in the pits at the time of excavation and the soils were slightly moist to moist with depth. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, spread footings placed on the undisturbed natural soil and designed for an allowable bearing pressure of 1,500 psf can be used for support of the proposed residence with a settlement potential. The soils tend to compress under loading and after wetting and there could be foundation settlements of around 1 to 11 inches. Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns. The topsoil and loose disturbed soils encountered at foundation bearing level in the excavation should be removed. The exposed soils should then be moisture adjusted to near optimum 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 14 feet. Foundation walls acting as retaining structures (if any) 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. H-P-KUMAR Project No. 17-7-798 -3 - Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab -on -grade construction with low risk of slab movement. 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 relatively well graded sand and gravel such as road base should be placed beneath slabs for support. 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 soils devoid of vegetation and topsoil. Surface Drainage: Proper surface grading and drainage will be important to limit potential wetting of the bearing soils below the building. 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. 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 will be needed uphill to direct surface runoff around the residence. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. H-PKUMAR Project No. 17-7-798 -4- 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 building caused by irrigation. Percolation Testing: Percolation tests were conducted on November 2, 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 prior to testing. The soils exposed in the percolation holes are similar to those exposed in the profile pits shown on Figure 2 and below the topsoil consist of loam. 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. We recommend the infiltration area be oversized due to the relatively slow percolation rate. 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 expressed 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, 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 H -P- KUMAR Project No. 17-7-798 -5 - 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 ` KU MAR Steven L. Pawlak, P • 1en 2 // ff9 Reviewed by: Dance . Hardin. E. SLP/kac Attachments: Figure 1 — Location of Exploratory Pits Figure 2 — Logs of Exploratory Pits Figures 3 and 4 — Swell -Consolidation Test Results Figures 5 & 6 — USDA Gradation Test Results Table 1 — Summary of Laboratory Test Results Table 2 — Percolation Test Results cc: Westar, Inc — Stephen Kesler (westar@rof.net) H-P�KUMAR Project No. 17-7-798 / � Y - i l - 30_4 / ./5' -,1 PROFILE PIT 29� L - - / tea— .r_— //,/%/ , / //,//'/ /:/// / /// // t•"/ / / �/ // % // // V �i///�, / //iii/fir, /// // /�I / / / / / / / / / ;// /// t / 7/ . / / / / i / /` / / / ,1/////11/1/1/ ///// /. f / /1 r / / /, ///////1// -/ „ /. / / / / / / /I7,/////// / / / ,,17/ / / // // //,// / i /// / / / / / / / / / // / /// , // / / ///, / / / / / / // / ; /,' / //// / ! EXISTING' IRRIGATION/ DITCH / / / / // / / // // i // / / / / / // //77//,z///////'/ j/, /// /' //// / ;/ / // //(( �/ �//, / i ,/ // //% %/ / // // / /' // / / /I n 1 / / //j// / /� // / / i i / / j /'/%/// / / / // /'2'Sa 389.x'"S.F' / , r / ' % / ;,' /' , / 84 7 7-A - //.rte / ,/// / / / // / „„,,,i,,, / / / / , / / / / /' / / / S;�''l(N / / / / ' / / -,/`7 s / / // / / ;; / ,I •/- / / / ' i 1.754ez' ,7 / / /' / / / ///1' - = / /,./ / / ,[ ,-,G / 1463 / i / / ; T 1 • - PIT --r ,J I I I I 1 / 1. 1 — I - -_ -- 30 0 30 SCALE—FEET 60 �.\ NATIVE `1 ' SPRINGS DRIVE 17-7-798 H-PtiKUMAR LOCATION OF EXPLORATORY PITS Fig. 1 DEPTH-FEET TEST PIT 1 TEST PIT 2 0 5 // / / / WC=1 0.4 DD=105 WC=1 6.4 DD=104 UC=2,050 / / / WC=9.4 /\DD=104 —200=81 WC=17.2 DD=105 PROFILE PIT 1 PROFILE PIT 2 / / / GRAVEL=1 / SAND=43 SILT=36 / /\ CLAY=20 /- / 0 5 10 10 LEGEND TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM, BROWN. CLAY (CL); SILTY, SANDY, STIFF, SLIGHTLY MOIST TO MOIST WITH DEPTH, BROWN, LOW PLASTICITY, SLIGHTLY POROUS. HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE OBSERVED ON NOVEMBER 2 AND 15, 2017 AND HAD BEEN DUG WITH A BACKHOE. 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 BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF OBSERVATION. 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); UC = UNCONFINED COMPRESSIVE STRENGTH (psf) (ASTM D 2166); 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; SILT AND CLAY = PERCENT PASSING THE NO. 325 SIEVE. 17-7-798 H -P- KUMAR LOGS OF EXPLORATORY PITS Fig. 2 1 0 —5 6 - KSF 10 100 17-7-798 H -P- KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 3 SAMPLE OF: Sandy Silty Clay FROM: Pit 1 @ 4' WC = 10.4 %, DD = 105 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING These test results appy only to the maniples tested. The testing report shall not be reproduced. except In full. without the written approval of Kumar and Associates. Inc. Swell Consolidation testing performed in accordance with ASTM D-4546. - KSF 10 100 17-7-798 H -P- KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 3 CONSOLIDATION - SWELL 0 —2 — 3 —4 — 5 6 —7 D PRESSURE - KSF 10 100 17-7-798 H -P- KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 4 SAMPLE OF: Sandy Silty Clay FROM: Pit 2 CO 6' WC = 17.2 %, DD = 105 pcf —200 = x %, LL = x, PI = x NO MOVEMENT WETTING UPON These tut results appy only to the ample tasted. The testing report shall not be reproduced. except in lull, without the written approval of Kumar and Associates. Inc. Swell Consolidotion testing performed in accordance with ASTM 0-4545. D PRESSURE - KSF 10 100 17-7-798 H -P- KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 4 c.\Draftng\177798-08 to HYDROMETER ANALYSIS SIEVE ANALYSIS 24HR n45 TIME READINGS 7 H 1MIN. MIN 15 MIN. €OMIN. 19MIN. 4MIN. #325 U.S. STANDARD SERIES 1 CLEAR SQUARE OPENINGS #140 #60 #35 #18 #10 #4 3/8" 3/4" 11/2" 3" 5"6" 8" __ PERCENT RETAINED 3 0 0 0 0 0 0 0 b' o 0 0 0 oo 0 0 0 0 0 PERCENT PASSING '" 001 002 0 .005 009 .019 .045 .106 025 .500 1.00 2.00 4.75 95 19.0 37.5 762 152 203 DIAMETER OF PARTICLES IN MILLIMETERS CLAY SILT SAND GRAVEL V. FINE 1 FINE I MEDIUM 1 COARSE IV COARSE SMALL 1 MEDIUM 1 LARGE COBBLES GRAVEL 1 % SAND 34 % SILT 0 % CLAY 65 % USDA SOIL TYPE: Loam FROM: Profile Pit 2 @ 3-4' 17-7-798 H -P- KUMAR USDA GRADATION TEST RESULTS Fig. 5 HYDROMETER ANALYSIS SIEVE ANALYSIS 24 D45 TIME READINGS HR. 7 HR 1 MIN. MIN. 15 MIN. 60MIN. 19MIN 4 MIN. #325 U.S. STANDARD SERIES I CLEAR SQUARE OPENINGS #140 #60 #35 #18 # 10 #4 3/8" 3/4" 1 1/2" 3' 5° 6" 8" _ _ _ PERCENT RETAINED 0 0 0 0 0 0 0 PERCENT PASSING ' 001 .002 0 .005 .009 _019 .045 .106 .025 500 1.00 200 415 9 5 19.0 37.5 76.2 152 203 DIAMETER OF PARTICLES IN MILLIMETERS CLAY SILT SAND GRAVEL V_ FINE 1 FINE 1 MEDIUM 1 COARSE 1V. COARSE SMALL I MEDIUM 1 LARGE COBBLES GRAVEL 1 % SAND 34 % SILT 0 % CLAY 65 % USDA SOIL TYPE: Loam FROM: Profile Pit 2 @ 3-4' 17--7-798 H -P--- KUMAR USDA GRADATION TEST RESULTS Fig. 6 Project No. 17-7-798 I- -I M ce cn W co < i_ co 2 i_ W } 1-' ix W J H Co ix )) F_ CO Q 13— J LL thi 0 CCQ E 2 0 (1) SOIL TYPE Sandy Silty Clay Sandy Silty Clay II Sandy Silty Clay 11 Sandy Silty Clay ct ct 0 Loam 11 USDA SOIL TEXTURE 4 o 0 O N 36 39 24 1-- J c (7)M VD CI :::,C; 4 co0 Cr) d' GRAVEL (%) PERCENT PASSING NO. 200 SIEVE 81 GRADATION 4 o 0) GRAVEL (%) SO1 (tad) A1ISN30 AUG waniVN 104 104 1) O NATURAL MOISTURE CONTENT (%) 10.4 d. N t 11 SAMPLE LOCATION DEPTH (ft) M IPerc Pit 3 3-4 0 N a�" H-P1<UMAR TABLE 2 PERCOLATION TEST RESULTS PROJECT NO. 17-7-798 HOLE NO. HOLE DEPTH (INCHES) LENGTH OF INTERVAL (MIN) WATER DEPTH AT START OF INTERVAL (INCHES) WATER DEPTH AT END OF INTERVAL (INCHES) DROP IN WATER LEVEL (INCHES) AVERAGE PERCOLATION RATE (MIN./INCH) P-1 491/2 15 Water Added 7 6 1 60 6 51/4 3/4 71/2 7 1/2 7 63/4 1/4 63/4 61/2 1/4 61/2 61/4 '/4 61/4 6 '/a P-2 511/2 15 101/2 91/2 1 45 91/2 83/4 3/4 83/4 8 3/4 8 73/4 1/4 73/4 7' 1/2 71/4 7 % 7 61/2 1/2 61/2 61/4 1/4 P-3 48 15 101/4 93/4 1/2 60 93/4 91/2 1/4 91/2 91/4 % 9'/4 9 '/4 9 83/4 1/4 83/4 81/2 1/4 81/2 81/4 % 81/4 8 1/4 Note: Percolation test holes were hand dug in the bottom of backhoe pits and soaked on November 2, 2017. Percolation tests were conducted on November 2, 2017. The average percolation rates were based on the last three readings of each test.