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HomeMy WebLinkAboutSoils Report 03.18.2005CTLITHOMPSON Hifi ISEKIEEEE SOILS AND FOUNDATION INVESTIGATION SINGLE-FAMILY RESIDENCE LOT 52, FOUR MILE RANCH GARFIELD COUNTY, COLORADO Prepared For: HAGEMANN BUILDERS P.O. Box 1692 Glenwood Springs, CO 81602 Attention: Mr. Frank Hagemann Project No. GS04451-D-120 March 18, 2005 234 Center Drive I Glenwood Springs, Colorado 81601 Telephone: 970-945-2809 Fax: 970-945-7411 TABLE OF CONTENTS SCOPE 1 SUMMARY OF CONCLUSIONS 1 SITE CONDITIONS 2 PROPOSED CONSTRUCTION 2 SUBSURFACE CONDITIONS 2 EARTHWORK 3 FOUNDATION 4 FLOOR SYSTEM AND SLABS -ON -GRADE 5 BELOW -GRADE CONSTRUCTION 6 SURFACE DRAINAGE 7 LIMITATIONS 8 FIGURE 1 -APPROXIMATE LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 - SUMMARY LOGS OF EXPLORATORY BORINGS FIGURE 3 - SWELL -CONSOLIDATION TEST RESULTS FIGURES 4 AND 5 - EXTERIOR FOUNDATION WALL DRAINS TABLE I - SUMMARY OF LABORATORY TEST RESULTS HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 SCOPE This report presents the results of our soils and foundation investigation for the single-family residence proposed on Lot 52, Four Mile Ranch in Garfield County, Colorado. We conducted this investigation to evaluate subsurface conditions at the site and provide foundation recommendations for the proposed construction. Our report was prepared from data developed from exploratory borings, laboratory testing, engineering analysis and our experience with similar conditions and construction. This report includes a description of the subsurface conditions at the site, and presents recommendations for design and construction of foundations, floor systems, and criteria for details influenced by the subsoils. Construction plans were not developed at the time of our investigation. If actual building plans differ significantly from the descriptions contained in the report, we should be informed so that we can check that our recommendations and design criteria are appropriate. SUMMARY OF CONCLUSIONS 1. Subsurface conditions encountered in our exploratory borings consisted of about 0.5 feet of sandy clay "topsoil" and 18.5 feet of silty sandy clay underlain by clayey silty gravel with cobbles and lenses of sand and clay. Practical auger refusal occurred on cobbles in our boring at a depth of 24 feet. Free ground water was not observed in the exploratory boring at the time of drilling. 2. We recommend constructing the residence on footing foundations that are supported by the undisturbed, natural soils. Care should be taken to prevent significant wetting of the soils below the building. Design and construction criteria for footings are presented in the report. r 3. We judge potential for differential undisturbed, ent natull ralesoils.o Additional s -on - grade supported by the discussion is in the report. 4. Surface drainage should be designed to provide for rapid removal of surface water away from the residence. A foundation drain should be installed around below -grade areas in the building. HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 SITE CONDITIONS Four Mile Ranch is located east of County Road 117 (Four Mile Road) in Garfield County, Colorado. Lot 52 is northwest of the intersection of Red Cliff Circle and Four Mile Boulevard. Ground surface on the lot generally slopes gently down to the west at grades Tess than 5 percent. Vegetation on the lot consists of sparse grasses and weeds. PROPOSED CONSTRUCTION Building plans for the residence were not developed at the time of our investigation. If construction will differ significantly from the descriptions below, we should be informed so that we can adjust our recommendations and design criteria as necessary. We expect the proposed residence will be a two-story, wood -frame building with an attached garage. A basement and/or crawl space may be constructed below the building. Similar residences in the area are typically constructed with slab -on -grade floors in basement and garage areas. Maximum foundation excavation depths will likely be on the order of 7 to 9 feet if a basement is constructed. Foundation loads are expected to vary between 1,000 and 3,000 pounds per lineal foot of foundation wall with maximum interior column Toads of 30 kips. Completed wall backfill depth may be slightly more than excavation depth as final grades are adjusted for drainage. SUBSURFACE CONDITIONS Subsurface conditions at the site were investigated by drilling one exploratory boring (TH-1) in the building envelope. The approximate location of the exploratory boring is shown on Figure 1. Exploratory drilling operations were directed by our staff engineer who logged subsurface conditions encountered in the boring and obtained samples of the soils. Graphic Togs of the soils encountered in our exploratory boring are shown on Figure 2. HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 Subsurface conditions encountered in our exploratory boring consisted of about 0.5 feet of sandy clay "topsoil" and 18.5 feet of silty sandy clay underlain by clayey silty gravel with cobbles and lenses of sand and clay. Practical auger refusal occurred on cobbles in our exploratory boring at a depth of 24 feet. Observations during drilling operations and results of field penetration resistance tests indicated the clay was stiff and the gravel was dense. Free ground water was not observed in the exploratory boring at the time of drilling. The exploratory boring was backfilled immediately after our field investigation was completed. Samples of the soils obtained from our exploratory boring were selected for laboratory testing. One sample of clay selected for one-dimensional, swell - consolidation testing exhibited no movement when wetted under an applied pressure of 1,000 psf. Swell -consolidation test results are shown Figure 3 and laboratory test results are summarized on Table I. EARTHWORK We anticipate excavations for the building foundation and utilities can be accomplished using conventional, heavy-duty excavation equipment. Excavation sides will need to be sloped or braced to meet local, state and federal safety regulations. We believe the soils at this site will generally classify as Type B and Type C soils based on OSHA standards governing excavations. Temporary slopes deeper than 5 feet should be no steeper than 1 to 1 (horizontal to vertical) in Type B soils and 1.5 to 1 in Type C soils. Contractors should identify the soils encountered in the excavations and refer to OSHA standards to determine appropriate slopes. We do not anticipate excavations for foundations or utilities will encounter significant amounts of ground water. However, excavations should be sloped to a gravity discharge or to a temporary sump where water can be removed by pumping. The ground surrounding the excavations should be sloped as much as practical to direct runoff away from the excavations. HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 Fill may be required to obtain subgrade elevations for the garage floor and exterior concrete flatwork. Areas which will receive fill should be stripped of vegetation, organic soils and debris. The on-site soils free of rocks larger than 6 inches in diameter, organic matter, and debris are suitable for use as fill. Fill should be placed in loose lifts of 10 inches thick or less, moisture conditioned to within 2 percent of optimum moisture content, and compacted to at least 95 percent of standard Proctor (ASTM D 698) maximum dry density. Moisture content and density of fill should be checked by a representative of our firm during placement. Properly placed backfill adjacent to foundation wall exteriors is important to reduce infiltration of surface water and subsequent consolidation. Backfill placed adjacent to foundation wall exteriors should be free of organic matter, debris and rocks larger than 6 inches in diameter. Backfill should be moisture conditioned to within 2 percent of optimum moisture content and compacted to at least 95 percent of standard Proctor (ASTM D 698) maximum dry density. FOUNDATION We recommend constructing the residence on footing foundations supported by the undisturbed, natural soils. Care should be taken to prevent significant wetting of the soils below the building. Our representative should be called to observe conditions exposed in the completed foundation excavation to check that the exposed soils are suitable for support of the designed footings. Recommended design and construction criteria for footings are presented below. 1. Footings supported by the natural soils should be designed for a maximum allowable soil bearing pressure of 3,000 psf. Soils loosened during excavation or the forming process for the footings should be removed or re -compacted prior to placing concrete. 2. Continuous wall footings should have a minimum width of at least 16 inches. Foundations for isolated columns should have minimum dimensions of 24 inches by 24 inches. Larger sizes may be required, depending upon foundation loads. HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 3. Grade beams and foundation walls should be well reinforced, top and bottom, to span undisclosed loose or soft soil pockets. We recommend reinforcement sufficient to span an unsupported distance of at least 12 feet. Reinforcement should be designed by the structural engineer. 4. The soils beneath exterior footings should be protected from freezing. We recommend the bottom of footings be constructed at a depth of at least 36 inches below finished exterior grades for frost protection. FLOOR SYSTEM AND SLABS -ON -GRADE Similar residences in the area are typically constructed with slab -on -grade floors in garage and basement areas. Based on our laboratory test data and experience, we judge slab -on -grade construction can be supported by the undisturbed, natural soils with low risk of differential movement and associated damage. Some fill may be required below the garage floor slab and exterior concrete flatwork. Fill should be in accordance with the recommendations outlined in the EARTHWORK section. We recommend the following precautions for slab -on -grade construction at this site. 1. We recommend against placing a gravel or sand layer below slabs because it increases the potential for wetting of the soils below the slabs. 2. Slabs should be separated from exterior walls and interior bearing members with slip joints which allow free vertical movement of the slabs. 3. Underslab plumbing should be pressure tested for leaks before the slabs are constructed. Plumbing and utilities which pass through slabs should be isolated from the slabs with sleeves and provided with flexible couplings to slab supported appliances. 4. Exterior patio and porch slabs should be isolated from the residence. These slabs should be well -reinforced to function as independent units. 5. Frequent control joints should be provided, in accordance with American Concrete Institute (ACI) recommendations, to reduce problems associated with shrinkage and curling. Our experience HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 5 indicates panels which are approximately square generally perform better than rectangular areas. BELOW -GRADE CONSTRUCTION Foundation walls which extend below -grade should be designed for lateral earth pressures where backfill is not present to about the same extent on both sides of the wall. Many factors affect the values of the design lateral earth pressure. These factors include, but are not limited to, the type, compaction, slope and drainage of the backfill, and the rigidity of the wall against rotation and deflection. For a very rigid wall where negligible or very little deflection will occur, an "at -rest" lateral earth pressure should be used in design. For walls which can deflect or rotate 0.5 to 1 percent of wall height (depending upon the backfill types), lower "active" lateral earth pressures are appropriate. Our experience indicates that typical basement walls can deflect or rotate slightly under normal design Toads, and that this deflection results in satisfactory wall performance. Thus, the earth pressures on the walls will likely be between the "active" and "at -rest" conditions. If the on-site soils are used as backfill, we recommend design of below -grade walls using an equivalent fluid density of at least 45 pcf for this site. This equivalent density does not include allowances for sloping backfill, surcharges or hydrostatic pressures. The recommended equivalent density assumes deflection; some minor cracking of walls may occur. If very little wall deflection is desired, a higher equivalent fluid density may be appropriate for design. Our recent experience indicates most basement and below -grade walls designed with 45 pcf to 50 pcf equivalent fluid density have performed satisfactorily. Backfill should be placed and compacted in accordance with the recommendations outlined in the EARTHWORK section Water from rain, snow melt and surface irrigation of lawns and landscaping frequently flows through relatively permeable backfill placed adjacent to a residence and collects on the surface of relatively impermeable soils occurring at the bottom of the excavation. This can cause wetting of the soils below the building and wet or moist conditions in basement and crawl space areas after construction. We HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 recommend provision of a foundation drain around below -grade areas in the building. The drain should consist of a 4 -inch diameter, slotted PVC pipe encased in free draining gravel. The drain should lead to a positive gravity outfall, or to a sump pit where water can be removed by pumping. Typical foundation drain details are presented on Figures 4 and 5. Ventilation is important to maintain acceptable humidity levels in crawl spaces. The mechanical systems designer should consider the humidity and temperature of air, and airflow volumes, during design of crawl space ventilation systems. It may be appropriate to install a ventilation system that is controlled by a humidistat. SURFACE DRAINAGE Surface drainage is critical to the performance of foundations, floor slabs and concrete flatwork. We recommend the following precautions be observed during construction and maintained at all times after the residence is completed: 1. The ground surface surrounding the exterior of the residence should be sloped to drain away from the residence in all directions. We recommend providing a slope of at least 12 inches in the first 10 feet around the residence, where possible. In no case should the slope be less than 6 inches in the first 5 feet. 2. Backfill around the exterior of foundation walls should be placed in maximum 10 inch thick loose lifts, moisture conditioned to within 2 percent of optimum moisture content and compacted to at least 95 percent of standard Proctor (ASTM D 698) maximum dry density. 3. The residence should be provided with roof gutters and downspouts. Roof downspouts and drains should discharge well beyond the limits of all backfill. Splash blocks and downspout extensions should be provided at all discharge points. 4. Landscaping should be carefully designed to minimize irrigation. Plants used near foundation walls should be limited to those with low moisture requirements; irrigated grass should not be located within 5 feet of the foundation. Sprinklers should not discharge within 5 feet of the foundation and should be directed away from the building. 5. Impervious plastic membranes should not be used to cover the ground surface immediately surrounding the residence. These membranes HAGEMANN BUILDERS % LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 tend to trap moisture and prevent normal evaporation from occurring. Geotextile fabrics can be used to control weed growth and allow some evaporation to occur. LIMITATIONS The exploratory borings drilled at the site provide a reasonably accurate picture of subsurface conditions. Variations in the subsurface conditions not indicated by the borings will occur. A representative of our firm should be called to observe subsoils exposed in the completed foundation excavation to check that the soil are as anticipated and suitable for support of the footings as designed. This investigation was conducted in a manner consistent with that level of care and skill ordinarily exercised by engineering geologists and geotechnical engineers currently practicing under similar conditions in the locality of this project. No other warranty, express or implied, is made. If we can be of further service in discussing the contents of this report or in the analysis of the influence of the subsoil conditions on the design of the structure, please call. CTL 1 THOMPSON, INC. Edward R. White, E.I. Staff Engineer ERW:JDK:cd (5 copies sent) HAGEMANN BUILDERS LOT 52, FOUR MILE RANCH CTLIT PROJECT NO. GS04451-D-120 Reviewed by: 1_ V eE. R . J mes D. KeIIO. s, P.E . Project Engineer n, 3 (15( 8 GS04451-D_F1 03/16/05 fjir Scale V=100` LI21 \r- 14 LOT 1 C0,714 5rt 2.03? A I \\ ;fix^ � \J�� ,6,1 _ �\ \ \ \- -a-11 1.1 Hageman Builders Lot 52, Four Mile Ranch Project No. GS04451-D-120 I 1. M89'0{.39 Approximate Locations of Exploratory Borings Fig. 1 0 0 IL C r n. 0 0 Project No. GS04451-120—D 0 5 10 15 20 25 TH-1 8/12 50/5 0 5 10 15 20 25 30 30 OEM somil MEOW MIMI v 0 v 3- 5 5 0 0 SUMMARY LOG LEGEND: El Sandy clay "topsoil", organics, very moist, brown. ©Clay, silty, sandy, scattered gravel, stiff, moist, rust, brown. (CL, CL—ML, ML) ID li NOTES: Gravel, clayey, silty, cobbles, lenses of sand and clay, dense, moist, rust, brown. (GC—GM, GM, SC—SM, SM, CL—ML) Drive sample. The symbol 8/12 indicates that 8 blows of a 140 pound hammer falling 30 inches were required to drive a 2.5 inch O.D. California sampler 12 inches. Drive sample. The symbol 50/5 indicates that 50 blows of a 140 pound hammer falling 30 inches were required to drive a 2.0 inch O.D. standard split—spoon sampler 5 inches. Indicates practical solid—stem auger refusal. 1. Exploratory boring was drilled on February 22, 2005 with 4—inch diameter, solid—stem auger and a track—mounted drill rig. The boring was backfilled immediately after exploratory drilling operations were completed. 2. No free ground water was found in our exploratory boring at the time of drilling. 3. Location of exploratory boring is approximate. 4. This exploratory boring is subject to the explanations, limitations and conclusions as contained in this report. EXPLORATORY BORING Fig. : 7 6 5 4 3 2 0 -1 —2 —3 -4 —5 —6 -7 COMPRESSION % EXPANSION -4 } } t • t i i } I } e i i 1 I 1 • I t r- { -lr--'__-F- IJO MOVEI�+IEAITADUE t } i i I i._..--- .-... Q WETTING f 1 I -8 0.1 Sample of CLAY, SANDY (CL) From TH-1 AT 9 FEET PROJECT NO. GS04451-D-120 1.0 10 APPLIED PRESSURE - KSF 1.00 NATURAL DRY UNIT WEIGHT= 104 PCF NATURAL MOISTURE CONTENT= 21.9 % Swell Consolidation Test Results FIG. 3 Pram 1 — CO SLOPE PER OSHA SLOPE PER REPORT I _ BACKFILL (COMPOSmON AND COMPACTION PER REPORT) BELOW GRADE WALL NOTE: DRAIN SHOULD BE AT LEAST 2 INCHES BELOW BOTTOM OF FOOTING AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVITY OUTLET OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING. ENCASE PIPE PIPE IN WASHED CONCRETE AGGREGATE (ASTM C33, NO. 57 OR NO. 67) EXTEND GRAVEL TO AT LEAST 1/2 HEIGHT OF FOOTING. COVER GRAVEL WITH - FILTER FABRIC. REINFORCING STEEL PER STRUCTURAL DRAWINGS SLOPE TO once+ 2" MINIMUM 8" MINIMUM OR BEYOND 1:1 SLOPE FROM BOTTOM OF FOOTING. (WHICHEVER IS GREATER) 4 -INCH DIAMETER PERFORATED DRAIN PIPE. THE PIPE SHOULD BE LAID IN A TRENCH WITH A MINIMUM SLOPE OF 0.5 PERCENT. Project No. GS04451-D-120 PROVIDE POSITIVE SLIP JOINT BETWEEN SLAB AND WALL. FLOOR SLAB FOOTING OR PAD PROVIDE PVC SHEETING GLUED TO FOUNDATION WALL TO REDUCE MOISTURE PENETRATION Exterior Foundation Wall Drain Fig. 4 SLOPE PER REPORT SLOPE PER OSHA ENCASE PIPE IN WASHED CONCRETE AGGREGATE (ASTM C33, NO. 57 OR NO. 67) EXTEND GRAVE TO AT LEAST 1/2 HEIGHT OF FOOTING. BELOW GRADE WALL -\ BACKFILL -� (COMPOSMON AND COMPACTION PER REPORT) COVER GRAVEL WITH FILTER FABRIC SUPPORTED ................. ................. N SLOPE TO DRAIN • • • 2" MINIMUM t 8" MINIMUM OR BEYOND 1:1 SLOPE FROM BOTTOM OF FOOTING. (WHICHEVER IS GREATER) 4 -INCH DIAMETER PERFORATED DRAIN PIPE. THE PIPE SHOULD BE PLACED IN A TRENCH WITH A SLOPE RANGE BETWEEN 1/8 INCH AND 1/4 INCH DROP PER FOOT OF DRAIN. v I Project No. GS04451-D-120 PROVIDE PVC SHEETING GLUED TO FOUNDATION WALL TO REDUCE MOISTURE PENETRATION. REINFORCED STEEL PER STRUCTURAL DRAWINGS CRAWL SPACE - FOOTING OR PAD BOTTOM OF EXCAVATION NOTE: DRAIN SHOULD BE AT LEAST 2 INCHES BELOW BOTTOM OF FOOTING AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVITY OUTLET OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING. Exterior Foundation Wail Drain Fig. 5 PROJECT NO. GS04451-D-120 W —J Ca F— SUMMARY OF LABORATORY TEST RESULTS SOIL CLASSIFICATION CLAY, SANDY (CL) CLAY, SANDY (CL) PASSING NO. 200 SIEVE (%) co SOLUBLE SULFATES (%) UNCONFINED COMPRESSIVE STRENGTH (PSF) 3ERG LIMITS PLASTICITY INDEX (%) Eo1_ W Q - 2 C'J-- J J a)r0 N J J ^ j - (n O O NATURAL DRY DENSITY (PCF) 104 LC) O NATURAL MOISTURE (%) O N O O N D W W CI O W r BORING ± H ± H 0 m rn m d *Note: Swell due to wetting under an applied load of 1,000 psf. Negative values indicate consolidation.