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HomeMy WebLinkAboutSoil's Report 07.26.2006ir CTLITHOMPSON SOILS AND FOUNDATION INVESTIGATION TUTTLE RESIDENCE LOT 48, FIRST EAGLES POINTS GARFIELD COUNTY, COLORADO Prepared For: MR. STEVE TUTTLE P. O. Box 232 New Castle, CO 81647 Project No. GS04799-120 July 26, 2006 234 Center Drive 1 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 SITE EARTHWORK 3 Excavations 3 Structural Fill 4 Backfill 4 FOUNDATIONS 5 SLAB -ON -GRADE CONSTRUCTION 6 BELOW -GRADE CONSTRUCTION 6 SUBSURFACE DRAINAGE 7 SURFACE DRAINAGE 8 LIMITATIONS 9 FIGURE 1 - APPROXIMATE LOCATIONS OF EXPLORATORY PITS FIGURE 2 — SUMMARY LOGS OF EXPLORATORY PITS FIGURE 3 — GRADATION TEST RESULTS FIGURE 4— SWELL CONSOLIDATION TEST RESULTS FIGURE 5 — EXTERIOR FOUNDATION WALL DRAIN MR. STEVE TUTTLE TUTTLE RESIDENCE PROJECT NO. GS04799-120 S:IGSO4799.000\120\2. Reporis\GS04799 120 R1Aac SCOPE This report presents the results of our soils and foundation investigation for the Tuttle Residence proposed on Lot 48, First Eagles Point, Battlement Mesa in Garfield County, Colorado. We conducted this investigation to evaluate the subsurface conditions at the site and provide geotechnical engineering recommendations for the planned construction. Our report was prepared from data developed from our field exploration, laboratory testing, engineering analysis, and our experience with similar conditions. This report includes a description of the subsurface conditions found in our exploratory pits and our opinions and recommendations for design and construction of foundations, floor systems, below - grade walls, subsurface drain systems, and details influenced by the subsoils. The recommendations contained in the report were developed based on the currently planned construction. We should be informed if actual construction will differ significantly from the descriptions herein. A summary of our conclusions is presented below. SUMMARY OF CONCLUSIONS 1. Subsurface conditions encountered in our exploratory pits consisted of sandy clay with cobbles and boulders to the maximum explored depth of 12 feet below existing ground surface. A thickness of about 1 foot of sandy clay fill was encountered in TP -2 over about 0.5 feet of sandy clay "topsoil". Free ground water was not observed in the exploratory pits. 2. Our subsurface information and experience in the area indicate that the sandy clay soil possesses low potential for movement under typical residential foundation loads. We recommend constructing the Tuttle Residence on footing foundations that are supported by the undisturbed sandy clay. Design and construction criteria for footings are presented in the report. 3. We judge potential differential movement of slab -on -grade floors supported by the undisturbed sandy clay or densely compacted structural fill will be low. Fill and "topsoil" should be removed from below areas of slab -on -grade. Additional discussion is in the report. TUTTLE RESIDENCE 1 PROJECT NO. G504799-120 S:\GS04799.000\12012. Reports\GSD4799 120 R1.doc 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. SITE CONDITIONS First Eagles Point is a residential development located in Battlement Mesa in Garfield County, Colorado. Lot 48 is located at the east side of the intersection of Talon Trail and Eagle Ridge Drive. Residential development surrounds the lot. The lot is relatively flat with grades of less than 5 percent down to the northwest. Overlot grading was performed on the lot. Based on our exploratory pits, maximum fill depths appear to be about 1 foot on the south and east portions of the lot. The site was covered with sparse weeds at the time of our exploration. PROPOSED CONSTRUCTION The Tuttle Residence is planned at the location shown on Figure 1. We understand that the Tuttle Residence will be a two-story, wood -frame building. Crawl space areas are planned below the main level of the building. The garage floor will be constructed as a slab -on -grade. Maximum foundation excavation depths of about 4 feet are anticipated. We expect the building will have maximum continuous wall loads between 1,000 and 3,000 pounds per lineal foot and maximum column loads of 30 kips. If actual construction will differ significantly from the descriptions above, we should be informed so that we can adjust our recommendations and design criteria, if necessary. SUBSURFACE CONDITIONS Subsurface conditions at the site were investigated by excavating two exploratory pits (TP -1 and TP -2) at the approximate locations shown on Figure 1. Pits TUTTLE RESIDENCE PROJECT NO. GS04799-120 SAGS04799.0001120\2. Reports 1GS04799 120 R1.doc 2 were excavated with a trackhoe. Exploratory operations were directed by our project engineer who logged the soils encountered in the pits and obtained samples for testing in our laboratory. Graphic logs of the soils found in our exploratory pits are shown on Figure 2. Subsurface conditions encountered in our exploratory pits consisted of sandy clay with cobbles and boulders to the maximum explored depth of 12 feet below existing ground surface. A thickness of about 1 foot of sandy clay fill was encountered in TP -2 over about 0.5 feet of "topsoil". Free ground water was not observed in the exploratory pits. Our observations during excavation indicated that the sandy clay was stiff. An increasing percentage of cobbles was encountered as excavation depths increased. Boulders up to 2 feet in diameter were encountered in TP -2. The pits were backfilled immediately after exploratory drilling operations were completed. Samples of the soils obtained from our exploratory pits were returned to our laboratory for pertinent testing. A sample of the sandy clay selected for gradation analysis contained 16 percent gravel, 33 percent sand, and 51 percent silt and clay size particles (passing the No. 200 sieve). Results of the gradation analysis are shown on Figure 3. One sample of clay was selected for one-dimensional, swell - consolidation testing. During the test procedure the sample was loaded with 1,000 psf and then flooded. The resulting volume change (i.e. swell or consolidation) was then measured. The sample tested exhibited 0.9 percent compression. Results of swell -consolidation testing are shown on Figure 4. EARTHWORK Excavations We expect that maximum foundation excavations will be about 4 feet. Excavations to the anticipated depths can be accomplished using conventional, TUTTLE RESIDENCE 3 PROJECT NO. GS04799-120 S:\GS04799.000\120\2. Reports \GS04799 120 R1.Goc heavy-duty excavation equipment. Excavation sides will need to be sloped or braced to meet local, state and federal safety regulations. The natural sandy clay will classify as a Type B soil based on OSHA standards governing excavations. Temporary slopes deeper than 4 feet should be no steeper than 1 to 1 (horizontal to vertical) in Type B soils. Contractors should identify the soils encountered in excavations and refer to OSHA standards to determine appropriate slopes. Free ground water was not encountered in our exploratory pits. We do not anticipate excavations for foundations or utilities will penetrate the ground water table. Excavations should be sloped to a positive gravity outfall or to a temporary sump where runoff water can be removed by pumping. Structural Fill We anticipate minor fill thicknesses may be required to achieve slab -on -grade subgrade in the garage. Our investigation identified areas of fill on the lot. Existing fill should be removed from below the building footprint and replaced with structural fill. Areas which will receive fill should be stripped of vegetation, organic soils, and debris. A CDOT Class 6 aggregate base course or the on-site soils free of organic matter, debris, and rocks larger than 4 inches in diameter can be used as structural fill. Structural fill should be placed in loose lifts of 10 inches thick or less, moisture - treated to within 2 percent of optimum moisture content, and compacted to at least 98 percent of standard Proctor (ASTM D 698) maximum dry density. Our representative should be called to check the density and moisture content of structural fill. Backfill Proper placement and compaction of backfill adjacent to the building is important to reduce infiltration of surface water and settlement. Backfill placed adjacent to foundation wall exteriors can consist of the on-site soil, provided it is free of organic matter, debris and rocks larger than 6 inches in diameter. Backfill should TUTTLE RESIDENCE PROJECT NO. GS04799-120 S1GS04799.000112012. Reports1GS04799 120 1,11.Eoc 4 be placed in loose lifts of 10 inches thick or less, moisture -treated to within 2 percent of optimum moisture content and compacted to at least 95 percent of standard Proctor (ASTM D 698) maximum dry density. We recommend that density and moisture content of backfill be checked during placement. FOUNDATIONS Our subsurface information at the site and experience in the area indicate that the natural sandy clay soil possesses low potential for movement under typical residential foundation loads. We recommend constructing the residence on footing foundations that are supported by the undisturbed, natural clay. Our representative should observe the completed foundation excavation to confirm that the exposed soils are as anticipated and suitable for support of the footings as designed. We expect that footings designed and constructed as recommended will experience maximum total settlement of about 1 inch. Recommended design and construction criteria for footings are presented below. 1. Footing foundations should be supported by the undisturbed natural clay. Soils loosened during excavation or the forming process for the footings should be removed or re -compacted prior to placing concrete. 2. Footings supported by the clay can be designed for a maximum allowable soil bearing pressure of 3,000 psf. 3. 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. 4. 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 10 feet. Reinforcement should be designed by the structural engineer. 5. The soils under 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. The Garfield County building TUTTLE RESIDENCE PROJECT NO. GS04799-120 S:\GS04799.0001120k2. Reporis\GSO4799120 R1.Eoc 5 department should be consulted to verify the required frost protection depth. SLAB -ON -GRADE CONSTRUCTION The garage floor is planned as a slab -on -grade. Based on our field and laboratory test data and our experience, we judge that slab -on -grade construction can be supported by the undisturbed, natural clay or densely compacted structural fill with low risk of differential movement and associated damage. Structural fill that is required to raise subgrade elevations below slabs should be placed and compacted as outlined in the Structural Fill section. We recommend the following precautions for slab -on -grade construction at this site. 1. Slabs should be separated from footings and column pads with slip joints which allow free vertical movement of the slabs. 2. 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. 3. Exterior patio and porch slabs should be isolated from the residence. These slabs should be well reinforced to function as independent units. 4. Frequent control joints should be provided, in accordance with American Concrete Institute (ACI) recommendations, to reduce problems associated with shrinkage and curling. 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 TUTTLE RESIDENCE PROJECT NO. G504799-120 S:1GS04799.000112012. Reports1GS04799 120 R1.doc 6 foundation wall where negligible or very little deflection will occur, an "at -rest" lateral earth pressure should be used in design. We recommend design of below -grade walls using an equivalent fluid density of at least 45 pcffor 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 walis may occur. If very little wall deflection is desired, a higher equivalent fluid density may be appropriate for design. Backfill placed adjacent to foundation wall exteriors should be placed and compacted in accordance with the recommendations in the Backfill section. SUBSURFACE DRAINAGE Water from precipitation, snow melt and surface irrigation of landscaping frequently flows through relatively permeable backfill placed adjacent to a residence and collects on the surface of relatively undisturbed soils at the bottom of the excavation. This can cause wetting of foundation soils, hydrostatic pressures on below -grade walls, and wet or moist conditions in below -grade areas after construction. To mitigate these concerns, we recommend provision of a foundation drain around below -grade (i.e., crawl space) areas in the building. The drain should consist of a 4 -inch diameter, perforated or 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. A typical foundation drain detail is shown on Figure 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 air flow volume, during design of crawl space ventilation systems. We believe it is appropriate to install a ventilation system that is controlled by a humidistat. TUTTLE RESIDENCE PROJECT NO. GS04799-120 SAG504799.0001120\2. Reports \GS04799120 121.010c 7 SURFACE DRAINAGE Surface drainage is critical to the performance of foundations, floor slabs, pavements, 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 convey surface water away from the building. In landscaped areas, we recommend providing a slope of at least 6 inches in the first 5 feet away from the building. 2. Backfill adjacent to foundation wall exteriors should be placed and compacted as described in the Backfill section. 3. The residence should be provided with 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. Water from roof and surface runoff should not be introduced to the foundation drain system. 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 or other landscaping requiring comparatively large amounts of irrigation should not be located within 5 feet of the foundation. Sprinklers should be at least 5 feet from building foundations and directed away from the building. Irrigation should be limited to the minimum amount sufficient to maintain vegetation; the application of additional water will increase the likelihood of slab and foundation movements. 5. Impervious plastic membranes should not be used to cover the ground surface immediately surrounding the buildings. These membranes 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. TUTTLE RESIDENCE PROJECT NO. GS04799-120 S:1GS04799.000\12012. Reports1GS04799 120 RI.tloc 8 LIMITATIONS Our exploratory pits were located to provide a reasonably accurate picture of subsurface conditions at the site. Variations in the subsurface conditions not indicated by our exploratory pits will occur. A representative of our firm should be called to observe the completed foundation excavations to confirm that the exposed soils are as anticipated and suitable for support of the footing as designed. This investigation was conducted in a manner consistent with that level of care and skill ordinarily exercised by geotechnical engineers currently practicing under similar conditions in the locality of this project. No warranty, express or implied, is made. If we can be of further service in discussing the contents of this report, please call. Very Truly Yours CAB:JM:cd (5 copies sent) TUTTLE RESIDENCE PROJECT NO. GS04799-120 S:1GSO4799.000112012. Reports\GS04799 120 R1.doc Re by n Mechling, P.E. anch Manager 9 Soale:l' = 20' / J 7 6 10.0 72.5.3 / it vel 7 7 J 7 9g J TP -1 G ca Lot 48 o- o' L 1] Mr. Steve Tuttle Tuttle Residence Project No. GS04799-120 • 04 W 1”Ur".,...ty ,� 72861 -- WFQ. est 116 7] '0 Eagle Ridge Drive �ve Depth In Feet LEGEND: 0 5 10 TP -1 TP -2 / / / • / / • / / / / / / • / 0 5 10 15 15 ®Fill, sandy clay, cobbles, slightly moist, tan, white. ® Clay, sandy "topsoil", roots, moist, brown. © Clay, sandy, cobbles, boulders, moist to slightly moist, stiff, tan, white. (CL) I]] Indicates hand drive. Indicates bulk sample. NOTES: MIN 409A ul y}dea 1. Exploratory pits were excavated with a backhoe on July 12, 2006. Pits were backfilled immediately after excavation operations were completed. 2. No free ground water was observed in the exploratory pits at the time of excavation. 3. Locations of exploratory pits are approximate. 4. These exploratory pits are subject to the explanations, limitations and conclusions as contained in this report. SUMMARY LOGS OF EXPLORATORY PITS Project No. GS04799-120 IF Fig. 2 % Sample of CLAY, SANDY (CL) From TP -2 AT 8-10 FEET GRAVEL 16 % SAND 33 SILT & CLAY 51 % LIQUID LIMIT - PLASTICITY INDEX - % z _ F re w n 10 50 60 90 inn w ij HYDROMETER ANALYSIS 1 SIEVE ANALYSIS 7 FIR. TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 15 MIN. 60 MIN. 19 MIN. 4 MIN. 1 MIN. '200 '100 '50 '40 '30 16 10 8 '4 3/8" 3/4' VA' 3 5'6" 8" 25 45 100 90 iLi 50 640 30C______Z__�_____ 20 10 0 .001 HR. 7 HR. TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS MIN. 15 MIN. 60 MIN. 19 MIN. 4 MIN. 1 MIN. '200 '100 '50 MO '30 16 10 '8 1 3/8" 3/4" 1'G' 3" 5'6" 8"0 J ___ ____ D __ t _______ L __ __=r k= :I_____ �____ ___ ____ _____ ____ _ _a_____ _=_a_____ ________ ________ _ _ __-`}= ___C - 1 r _ __�___ ____ _ _ _________ __j_____ _____ _______ j ________ = {_- ___ k= _ E 7,_________�___ _______ + _ _ _________r________ C___________ j________ ___ ___.1k_ ---- ____ ---- ____ -__- ____ ____ ____ __L _ i --- ---- _-_- _- ---- ===80 -k=== - ------- - ---- --- -- -------- ----- - — --1 1 I t =__- ---_�___ --- -- -�-- --- k F-� r--.T--F _-___,� �'----`----- =_=== __-rrti.- •.� ------- ======== . -__- =__-- -� -- ==='`- , � 0.002 .005 .009 .0 9 .037 .074 .149 .297 0.42 590 1.19 2.0 2.38 4.76 9.52 19.1 36.1 76.2 1215220U CLAY (PLASTIC) TO SILT NON -PLASTIC) SANDS SANDS GRAVEL FINE 1 COARSE I COBBLES FINE 1 MEDIUM 1 COARSE FINE 1 COARSE 1 COBBLES % Sample of CLAY, SANDY (CL) From TP -2 AT 8-10 FEET GRAVEL 16 % SAND 33 SILT & CLAY 51 % LIQUID LIMIT - PLASTICITY INDEX - % Sample of From PROJECT NO. GS04799-120 GRAVEL % SAND SILT & CLAY % LIQUID LIMIT PLASTICITY INDEX Gradation Test Results FIG. 3 z _ F re w n HYDROMETER ANALYSIS 1 SIEVE ANALYSIS 25 45 MIN. 100 90 80 070 z_]_________]_____ _ o 50 rc 6 40 30 20 10 0 .001 HR. 7 FIR. TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 15 MIN. 60 MIN. 19 MIN. 4 MIN. 1 MIN. '200 '100 '50 '40 '30 16 10 8 '4 3/8" 3/4' VA' 3 5'6" 8" 0 70 20 30 40 50 60 70 90 100 ___ _________ D _______ -C -r- :I_____ �____ ___ ____ _____ ____ _ _a_____ _=_a_____ ________ ________ __-`}= ___C - 1 r _ __�___ ____ _ _ _________ __j_____ _____ ________ ___ ___ _ __ 7,_________�___ ---- ____ ---- ____ -__- ____ ____ ________ --- ---- _-_- ===80 -k=== - ------- _J__===�__ ---- --- -------- --- - — --1 1 I t =__- ---_�___ --- -- -�-- --- -77-==_-- ---------- _-___,� -___ -------_------r__ _______ r -__- =__-- -� -_ - �-------- 0.002 .005 .009 .019 .037 .074 .149 .297 042590 1.19 2.0 2.38 4.76 9.52 19.1 36.1 76.2 12752 200 DIAMETER OF PARTICLE IN MILLIMETERS CLAY (PLASTIC) TO SILT (NDN -PLASTIC) SANDS GRAVEL FINE 1 MEDIUM 1 COARSE FINE 1 COARSE I COBBLES Sample of From PROJECT NO. GS04799-120 GRAVEL % SAND SILT & CLAY % LIQUID LIMIT PLASTICITY INDEX Gradation Test Results FIG. 3 COMPRESSION % EXPANSION 7 6 5 4 3 2 0 -2 -3 -4 -5 -6 -7 -8 J. 1 J J 1 ✓ 1 T 1 r L J 1 J 1 ✓ -1 T L L 1 L J r r r T r 1 T 1 {4DDITIONA4 COMPRESSION NDER CONSTANT PRESSURE DUE TO WETTING L L 1 L 1 L J 1 J T1 - r -r- - r_______ T____r _T_1r_ 0.1 Sample of CLAY, SANDY (CL) 1.0 10 APPLIED PRESSURE - KSF From TP -2 AT 5 FEET PROJECT NO. GS04799-120 100 NATURAL DRY UNIT WEIGHT= 81 PCF NATURAL MOISTURE CONTENT= 19.2 Swell Consolidation Test Results FIG.4 SLOPE PER OSHA SLOPE PER REPORT BACKFILL (COMPOSITION AND COMPACTION PER REPORT) ................. BELOW GRADE WALL —f— PROVIDE PVC SHEETING GLUED TO FOUNDATION WALL TO REDUCE MOISTURE PENETRATION COVER GRAVEL WITH FILTER FABRIC ENCASE PIPE IN WASHED CONCRETE AGGREGATE (ASTM C33, NO. 57 OR NO. 67). EXTEND GRAVEL TO AT LEAST 1/2 HEIGHT OF FOOTING. 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. STRUCTURALLY SUPPORTEDJr FLOOR SYSTEM wwnw CRAWL SPACE —f PER STRUCTURAL FOOTING OR PAD SLOPE 10 OR/JN 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 LAID IN A TRENCH WITH A SLOPE RANGE BETWEEN 1/8 INCH AND 1/4 INCH DROP PER FOOT OF DRAIN. Protect No. GS04799-120 BOTTOM OF EXCAVATION Exterior Foundation Wall Drain Flg. 5