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HomeMy WebLinkAboutSoils Report for Foundation Design & Perc Testing 07.13.2018H-PIKUMAR 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 Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado July 13, 2018 Jose Olivas 27653 Highway 6, #2209 Rifle, Colorado 81650 i_veonstruetion@ hotmail.com Project No.18-7-371 Subject: Subsoil Study for Foundation Design and Percolation Testing, Proposed Residence, Lot 5, Native Springs, 18 Native Springs Drive, Garfield County, Colorado Dear Mr. Olivas: 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 Jose Olivas, dated May 22, 2018. 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 3 feet below existing ground surface. 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 southeast 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 horse pasture. A metal -framed shop is located on the east side of the lot. A well is located in the northwest corner of the building envelope. The ground surface is relatively flat, sloping down to the southwest at a grade of 1 to 2%. Vegetation consists of grass and weeds. -2 - 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 in the building area, below about 1/2 to 1 foot of topsoil, consist of stiff, sandy to very sandy silt and clay to the pit depths of 8 to 81/ feet. Results of swell -consolidation testing performed on relatively undisturbed samples of the silt and clay soils, presented on Figures 4 through 6, indicate low compressibility under existing moisture conditions and light loading and a low collapse potential (settlement with no load increase) when wetted. The samples were moderately compressible under additional loading after wetting. Results of gradation analyses performed on samples of soils obtained from the septic disposal area pits are presented on Figure 7. 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 very 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 particularly when wetted and there could be foundation settlements of around 1 to 1 inch. 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 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. 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 H-P�KUMAR Project No. 18-7-371 -3 - 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. Underdrain System: It is our understanding the proposed finished floor elevation at the lowest level is at or above the surrounding grade. Therefore, a foundation drain system is not required. 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, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain system. If the finished floor elevation of the proposed structure is revised to have a floor level below the surrounding grade, we should be contacted to provide recommendations for an underdrain system. All earth retaining structures should be properly drained. 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. H-PKUMAR Project No. 18-7-371 -4- 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 3 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. Percolation Testing: Percolation tests were conducted on May 31, 2018 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 nil to 2 feet of sandy clay loam overlying sandy loam. In Profile Pit 1, a 1 foot layer of gravelly sand was encountered at 4 feet in depth. The percolation test results are presented in Table 2. Percolation Test Hole 3 would not hold water due to a "critter hole". 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 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 H-P-:KUMAR Project No. 18-7-371 -5 - 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, I -N KUMAR Atiov Shane M. Mello, Staff Engineer Reviewed by: Daniel E. Hardin. P. SMM/kac Attachments: Figure 1 — Location of Exploratory Pits Figure 2 — Logs of Exploratory Pits Figure 3 — Legend and Notes Figures 4, 5 & 6 — Swell -Consolidation Test Results Figure 7 — USDA Gradation Test Results Table 1 — Summary of Laboratory Test Results Table 2 — Percolation Test Results cc: Stephen Kesler (stephen C westar-inc.co) H-P%KUMAR Project No. 18-7-371 NATIVE SPRINGS DRIVE J LOT 6 70 0 70 140 APPROXIMATE SCALE -FEET 0 WELL BUILDING ENVELOPE ■ PIT 2 LOT 5 EXISTING SHOP PIT 1 P-1 P-3 A n 1 PROFILE 1 o • PROFILE PIT 1P-2 PIT 2 LOT 4 J LEGEND: • EXPLORATORY PIT A PERCOLATION TEST HOLE 18-7-371 H -P- I<UMAR LOCATION OF EXPLORATORY PITS Fig. 1 1- w w a w — 0 5 PIT 1 WC=6.4 DD=89 WC=19.0 DD=104 PIT 2 WC=1 2.6 DD=102 WC=8.7 —200=16 PROFILE PIT 1 PROFILE PIT 2 WC=4.7 7--'—; 0 GRAVEL=0 SAND=56 —1 SILT=32 / __1 ._I CLAY=12 / _e r 5 10 10 uJ w w w 18-7-371 H-P-� KUMAR LOGS OF EXPLORATORY PITS Fig. 2 LEGEND 0 L TOPSOIL, SANDY SILT AND CLAY, ORGANIC, STIFF, SLIGHTLY MOIST, BROWN. CLAY (CL): SANDY, SILTY, STIFF, SLIGHTLY MOIST, BROWN. PROFILE PIT 2 ONLY. CLAY AND SILT (CL—ML): SANDY TO VERY SANDY, STIFF, SLIGHTLY MOIST TO MOIST, BROWN. SAND AND CLAY (SC—CL): SILTY, LOOSE, MOIST TO VERY MOIST, BROWN. PROFILE PIT 1 ONLY. SAND AND GRAVEL (SM—GM): SILTY, MEDIUM DENSE, MOIST, BROWN. PROFILE PIT 1 ONLY. HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON MAY 31, 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 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 EXCAVATION. 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. 18-7-371 H - PtiKU MAR LEGEND AND NOTES Fig. 3 2 0 —2 3W —4 z O 1- 6— — O z O —i0 — 12 — 14 — 16 Ther less nemoll• .00 an,y to the samples failed. the leilinq repel Oen nol 4c nproduaed. ncsyl in Cum, ..thou. Vic .ntlan appro.pl or xymor and N,DNolci Inc. S.sp Cpnfd�da4an tnbnp performed .$ occo.donce an w4 0-4546. SAMPLE OF: Sandy Clay and Silt FROM: Pit 1 2.5' WC = 6.4 %, DD = 89 pcf L ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING a 1.0 APPLIED PRESSURE — KSF 10 100 18-7-371 H-P4=-KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 4 1 nr-s, 0 ZSZ z 0 o —4 — 5 — 6 their teal reseal doper antd la the samples 1101400. the 4HUnq repdet rasa not be reproduced, except nt fur, -U,oul U,e .niten open:Pot of good, onC Madddtea, Inc Seed Comoodoft perld.nud 10 accordance mad ASL 0-4018. SAMPLE OF: Sandy Clay and Silt FROM: Pit 1 c 7' WC = 19.0 %, DD = 104 pcf NO MOVEMENT UPON WETTING 1 1.0 APPLIED PRESSURE - KSF 10 100 18-7-371 H-P%KUMAR SWELL -CONSOLIDATION TEST RESULTS Fig. 5 CONSOLIDATION - SWELL 1 0 —2 SAMPLE OF: Sandy Clay and Silt FROM: Pit 2 © 4' WC = 12.6 %, DD = 102 pcf them left resod Waal posy (0 the w mphs teeled. The lest.; ream! P han nal he repeedaCed, e+Cept M fun, without the written approval of %wmae and Associates, Inc Swell Conealidatian teaIno peffan'fSd in Inca/Mance with T D-ISel. ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE - KSF 10 100 18-7-371 H -P KUli AR SWELL -CONSOLIDATION TEST RESULTS Fig. 6 PERCENT RETAINED 8 0 0 0 8 0 0 0 0 0 0 N 0 0 0 0 0 0 0 0 0 8 PERCENT PASSING HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS 7HR 15/AN. HOMLN 1BMRL 1 1MIN. M #325 U.S. STANDARD SERIES I CLEAR SQUARE OPENINGS #140 #60 #35 #18 #10 #4 3/8° 3/4' 1107 3' 5'5' 7:------- „........../ 203 .002 .005 CLAY GRAVEL USDA .009 .019 .045 .106 .025 .500 1.00 2.00 4.75 9 5 19.0 37.5 76.2 DIAMETER OF PARTICLES IN MILLIMETERS 152 SILT SAND h.COAFISE GRAVEL COBBLES % V. FINE I FINE MEDIUM I COARSE SMALL 1 MEDIUM LARGE L 12 @ 2'-3' 0 % SAND 56 % SILT 32 % CLAY SOIL TYPE: Sandy Loam FROM: Profile Pit 1 18-7-371 H-PtiKLJMAR USDA GRADATION TEST RESULTS Fig. 7 H-PKUMAR TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 18-7-371 SAMPLE L PIT 1 °CATION DEPTH (ft) 2% 7 NATURAL MOISTURE CONTENT (%) 6.4 19.0 2 4 NATURAL DRY DENSITY (pcf) 89 104 GRAD ATION GRAVEL (%) SAND (%) PERCENT PASSING 1 NO. 200 SIEVE USDA SOIL TEXTURE GRAVEL SAND SILT CLAY (%) (%) 12.6 102 SOIL TYPE Sandy Clay and Silt Sandy Clay and Silt Sandy Clay and Silt 6 8.7 16 Silty Sand PP -1 2-3 4.7 0 56 32 12 Sandy Loam HOLE NO. P-1 HOLE DEPTH (INCHES) 36 H-P�KUMAR TABLE 2 PERCOLATION TEST RESULTS LENGTH OF INTERVAL (MIN) 10 WATER DEPTH AT START OF INTERVAL (INCHES) PROJECT NO. 18-7-371 WATER DROP IN DEPTH AT WATER END OF LEVEL INTERVAL (INCHES) (INCHES) Water Added 73/4 7 3A AVERAGE PERCOLATION RATE (MIN./INCH) 7 63/4 1/4 6% 61/4 1/2 91/2 91/4 1/4 91/4 8% 1/2 8% 83/ 3/8 83 8 3/8 27 P-2 35 10 91/8 8% 3/8 8% 81/2 1/4 81/2 83/ 1 8% 81/4 1/8 81/4 8%3 1�8 8% 8 1h 8 7'/3 'A P-3 36 1 12 0 12 80 N/A Note: Percolation test holes were hand dug in the bottom of backhoe pits on May 31, 2018. Percolation tests were conducted on May 31, 2018. The average percolation rates were based on the last readings of each test. Percolation test hole P-3 appeared to have encountered a `critter hole' through which the water ran out.