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HomeMy WebLinkAboutSoil's Report 07.21.2006SOILS AND FOUNDATION INVESTIGATION PROPOSED RESIDENCE BUILDING 24, SUNFLOWER LOOP ROAD LOT 54, CERISE RANCH DEVELOPMENT GARFIELD COUNTY, COLORADO Prepared for: FRIEL CONSTRUCTION 275 DEERTRAIL AVENUE CARBONDALE, COLORADO 81623 JOB NO. C061088 InTEC Austin (512) 252-1218 fax (512) 252-1219 JULY 21, 2006 CHURCH and Associates Inc. a division of Integrated Testing and Engineering Company of Denver Metro, LLC 4501 Wadsworth Blvd. • Wheat Ridge, Colorado 80033 • (303) 463-9317 • fax (303) 463-9321 DFW Metro Houston San Antonio (817) 858-0890 (281) 371-3330 (210) 525-9033 fax (817) 858-0036 fax (281) 371-3334 fax (210) 525-9032 InTEC TABLE OF CONTENTS SCOPE 1 CONCLUSIONS 1 PROPOSED CONSTRUCTION 2 SITE CONDITIONS 2 INVESTIGATION 3 SUBSURFACE CONDITIONS 3 SITE PREPARATION 4 EXCAVATIONS 5 BUILDING FOUNDATIONS 6 SLAB -ON -GRADE CONSTRUCTION 7 LATERAL LOADS AND SUBSURFACE DRAINAGE 8 SURFACE DRAINAGE 9 LIMITATIONS 10 FIGURE 1 —SITE PLAN AND LOCATION OF TEST PITS FIGURE 2 TO 3 — LOG OF TEST PITS FIGURES 4 TO 6 — LABORATORY TEST RESULTS APPENDIX A — IMPORTANT INFORMATION ABOUT THE REPORT APPENDIX B — TYPICAL DRAIN DETAILS APPENDIX C — EARTHWORK SPECIFICATIONS Integrated Testing and Engineering Company IInTECI SCOPE This report presents the results of a soils and foundation investigation for the proposed residential building at the Cerise Ranch Development, in Garfield County, Colorado. The purpose of our investigation was to evaluate subsurface conditions and provide geotechnical recommendations for the proposed construction. The report presents a description of subsurface conditions encountered at the site, recommended foundation system, and design and construction criteria influenced by the conditions encountered. The report is based on data developed during the field and laboratory investigations and our experience. A summary of our findings and recommendations is presented below. CONCLUSIONS 1. Subsurface materials encountered in the first test pit (TP -1) consisted of 0.5 Ft. of organic topsoil, overlying silty gravel with cobbles and some small boulders to a depth of 3.5 feet. Underlying this cobbly gravel we encountered river lain clayey silts and very fine sands to the maximum explored depth of approximately 7 feet. Subsurface materials encountered in the second test pit (TP -2) consisted of 3 to 6 inches of organic topsoil with some cobble material and occasional boulders, overlying three (3) to four (4) feet of fine sand and silt with gravel, cobble lenses, and occasional boulders; and, beneath this silty gravel zone (from approximately 3.5 or 4.0 ft. to 10.5 ft. in depth) fine-grained river sands and floodplain clayey silts were encountered, for the full depth of the excavated Test Pit (#2). 2. Free water was not encountered during excavation and the test pits remained dry. 3. The structure can be constructed with a spread footing foundation system on the native silt and gravel soils or compacted structural fill within the river floodplain silt and fine sand found in the deeper portion of the test pit excavations. An expanded spread footing foundation Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. CO it►MEC Page 2 system will have a low risk of movement within the minimally collapsible soils found in the floodplain silt. Design and construction criteria are presented in the body of the report. 4. The building can be constructed with a crawl space or basement. Any new slab -on -grade construction on the native silty and sandy soils will have a low risk for movement due to expansive soils. For slab -on -grade construction, slabs should ideally be constructed as "floating" slabs. The slabs should be free to move in the vertical direction. 5. Positive drainage down and away from all foundation walls should be established and maintained at all times. Precautions to avoid surface water impacting the planned structure should be taken, as discussed in the report. PROPOSED CONSTRUCTION A residential building is proposed at the location presented on Figure 1. The building will be supported on a concrete footing foundation and slab -on -grade construction is assumed for the building walls and subfloor. Relatively light to moderate construction loads are anticipated. It is understood the first floor level will be above to the present ground surface. An approximate foundation depth of 6 to 8 feet below the existing ground surface elevation was assumed for this investigation. SITE CONDITIONS The site is located in a residential and agricultural area southeast of Carbondale in Garfield County, Colorado. The site had one and two-story homes, storage buildings, and grassed playground with small lakes nearby at the time of our site investigation. The ground surface of the property slopes gently to the south and southwest at approximately 2 to 5 percent in the vicinity of the proposed building pad area. The ground elevation within the building envelope is below and about 200 feet south of a steep escarpment of a juniper and pinyon forest terrace capped by lava (basalt) covered terrain which forms a Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. OliiiiSECI Pagel_ plateau bordering the Frying Pan Roaring Fork River valley. The building site is located within an Alfalfa planted pasture or hay meadow just south of what appears to be an old Narrow Gauge rail bed (judging by the gentle grade of the bed). This feature and the proposed building pad distance from the steep escarpment to the northeast should mitigate against any potential for slope failure and debris flow from impinging upon the building structure in the event of a high discharge rainfall event. INVESTIGATION Subsurface conditions were investigated on July 7, 2006 by excavating two exploratory test pits at the locations presented on Figure 1. The test pits were excavated with a tire mounted backhoe excavator. Bulk samples were obtained at selected intervals for laboratory testing. Penetration testing to determine the consistency or relative density of the soils was performed in Test Pit #2, but based on observations of the test pit excavations, the soils appear to be medium dense to hard where gravel and cobble was encountered and somewhat less dense where floodplain deposits were found. A log of the soils encountered is presented on the Log of Exploratory Test Pits, Figure 2 and 3. Samples were returned to the laboratory where they were visually classified and testing was assigned to evaluate the engineering properties of the material. Laboratory testing consisted of a gradation analysis, moisture and density determination, and swell -consolidation, and remolded strength tests. The results of the laboratory testing are presented on Figures 4 through 6. SUBSURFACE CONDITIONS Subsurface materials encountered in the first test pit (TP -1) consisted of topsoil overlying silt and fine sand with considerable gravel and cobble material with some small boulders to a depth of 3.5 feet. Underlying this soil zone, loose to medium stiff clayey river silt was encountered to the full depth of the test pit # 1. Free water was not encountered in the test pit during excavation, and the hole remained dry. Additional subsurface details are presented on Figure 2. Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. CCi4Iifl£C Page 4 Subsurface materials encountered in the second test pit (TP -2) consisted of 6 inches of topsoil with some cobble to boulder sized material exposed on the surface above a three to four foot layer of natural silt and fine sand with gravel and cobble lenses and occasional small boulders. From about 4.0 to 10.5 feet in depth, medium stiff clayey river silt derived from stream bank overflow was found in the remainder of the test pit excavation. Free water also was not encountered in this test pit, the pit remained dry for the duration of the exploration program. Additional details are shown in Figure 3. The geotechnical practice in Colorado uses a relative scale to evaluate swelling potentials. When the sample is wetted under a surcharge pressure of 1000 pounds per square foot (PSF), the measured swell is classified as low, moderate, high, or very high. It is important to note that measured swell is not the only criteria for slab -on -grade recommendations and additional factors are considered by the geotechnical engineer when evaluating the risk for slab -on -grade and foundation construction. Additional information regarding geotechnical risk is included as Appendix A. Risk Category Percent Swell Under A 1000 PSF Surcharge Pressure Low 0 — <2 Moderate 2 - <4 High 4 — <6 Very High 6 or Greater The collected samples were tested for their swelling capacity, little or no swell was indicated during the test. Due to the relatively low percentage of fine-grained clayey materials present, the soils are assumed to be non -expansive. However some tests did indicate the soils in the deepest portions of the test pits may have a small to moderate consolidation potential, as soils derived from alluvial floodplain deposits are known to sometimes be collapsible due to the high silt and void content. SITE PREPARATION Organic material such as topsoil and vegetative debris should be removed from the foundation area and wasted off site or used for non-structural purposes. Any required structural fill should be placed Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. CC 4tiCEEC Pale 5 in 8 -inch uncompacted thickness lifts and compacted to 95 percent of the standard Proctor maximum dry density (MPD) within 3 percent of the optimum moisture content. Structural fill is a non - expansive material that classifies as sand according to the Unified Soil Classification System possessing a liquid limit less than 40 and a plasticity index less than 20. The on site sand and gravel (rock size of 3 inches or less) soil is suitable for use as structural fill. Any soils loosened by the excavation or forming process should be removed from the footing areas prior to placing concrete or compacted as recommended above. A geotechnical engineer should review earthwork placement activities. EXCAVATIONS Excavations should not remain open for extended periods of time, permitting wetting or drying of the bearing materials. Moisture changes of the bearing materials may increase the risk for movement. The materials on site are categorized as Type C according the Occupational Safety and Health Administration (OSHA). Based on published OSHA guidelines, the temporary excavations in the Type C soils can have a maximum temporary slope of 1.5:1 horizontal to vertical (H:V). This inclination is reasonable for the conditions at the site. Exceeding this inclination will increase the chance of deformation, especially over a long time period. Some localized deformation of the bank may occur, especially during wet weather, freezing, loading or with vibrations. Care should be taken when working near the sides of the excavation at all times, and the slopes should be monitored by onsite personnel during construction for evidence of sloughing, bulging or toppling of the sidewalls or cracking at the ground surface. Surcharge loading at the top of the cut by equipment, materials, or vehicles must be avoided, since surcharge loading will increase the risk of caving. Spoils of the excavation must be placed a minimum of 2 horizontal feet from the edge of the excavation. A geotechnical engineer should observe the completed excavation prior to foundation installation. Integrated Testing and Engineering Company Soils and Foundation Invest'gation Job No. CM1prEC }'age 6 BUILDING FOUNDATIONS The soils at the anticipated foundation elevations of 8 to 10 feet below the ground surface consist of river silt and minor gravelly sands that are assumed to be non -expansive. The proposed building can be constructed with an expanded spread footing foundation system founded on the native silty and sandy soils of a competent nature. The footings should be designed for a maximum allowable soil bearing pressure of 1,000 PSF if founded upon silt soils of a light to moderate consolidation potential. A spread footing foundation system should be designed and constructed to meet the following criteria. Locations in the vicinity of the Cerise Ranch Development and probably on the ranch property often contain collapsible silt soils of the Frying Pan River Floodplain Alluvium formation. These potentially problematic soils are commonly inter -layered with the more competent silts and gravelly sands. If these soils are encountered in significant amounts anywhere below the building excavation footprint, it may be necessary to over -excavate and replace these soils with up to three or more feet of engineered structural fill, or where this is impractical due to excessive ground water flows or other factors, it is expedient to replace footings with drilled or helical piers and grade beams to bridge these problematic soils. 1. All footings must be supported by native silty and sandy soils if not in a degraded condition due to weathering or exposure to the elements. Soils loosened by the excavation or forming process should be removed from the footing areas prior to placing concrete. If structural fill is required below foundations, it should be placed as detailed above in the Site Preparation section of this report. The footing excavations should be observed by a geotechnical engineer to confirm footings are supported by suitable material. 2. Recommended minimum footing widths should be at least 24 inches for continuous footings, and 40 inches square for concrete pads, which support columns. Larger sized footings may be necessary depending on the load of the structure and soil types encountered. Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. altillinC Pace 7 3. Continuous foundation walls should be reinforced to span local anomalies in the subsoil. Walls should be reinforced to span an unsupported length of 10 feet. 4. Footings must be protected from frost action. Footings should be covered with a minimum of 3 feet of soil for frost protection. SLAB -ON -GRADE CONSTRUCTION We understand that the proposed building will have finished areas supported by slabs -on -grade. Some slabs will also be supported near the ground surface such as exterior flatwork. The native silty and sandy soil is suitable for slab -on -grade construction with a low risk of movement due to expansive soil with an estimated slab heave of less than 1 inch. A structural floor over a void space should be used where the risk for movement is not acceptable. The slabs should be constructed as "floating" slabs, which are free to move in the vertical direction. If fill soils are used, a non - expansive granular soil should be used as discussed in the 'Site Preparation' section such as those found in the upper 3 to 4 feet of the site. If needed, the following design and construction details for finished slab -on -grade construction are recommended. 1. Slabs should be separated from exterior walls and interior bearing members. Vertical movement of the slabs should not be restricted. Using brittle floor finishes, such as tile, on floors supported by expansive soil increases the risk for damage. 2. Slab bearing partitions should be minimized. Where such partitions are necessary, a slip joint should be constructed to allow free vertical movement of the partitions. Slip joints should allow at least 1.5 inches of vertical movement and should be monitored and maintained by the owner after construction. Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. COMCFEC Page 8 3. Underslab plumbing should be eliminated where feasible. Where such plutnbing is unavoidable it should be thoroughly pressure tested during construction and rocks larger than 3 inches in diameter should not be placed near these features so as to avoid "point loading". 4. Plumbing and utilities, which pass through the slab, should be isolated from the slab with expansion joint material. 5. If a forced air heating system is used and the furnace is located on the slab, we recommend provision of a 6 -inch collapsible connection between the furnace and the ductwork. The above design and construction criteria will not prevent movement, but will reduce damage if movement occurs. LATERAL LOADS AND SUBSURFACE DRAINAGE Below grade walls must be designed to resist lateral loads. We recommend designing the walls with an "active" equivalent fluid pressure of 45 pounds per cubic foot (PCF), an "at rest" equivalent fluid pressure of 55 PCF, and a "passive" equivalent fluid pressure of 400 PCF below a depth of 3 feet. A coefficient of friction of 0.35 should be used for sliding resistance at the base of the footings on the natural silt or fine granular soils for mass concrete; with somewhat higher values if the coarse, gravelly material is utilized for structural fill. Should the excavation process encounter problematic soils of the fine river alluvium these values may have to be adjusted to reflect the changed conditions. These pressures assume a level backfill surface, and do not include any surcharge loading or hydrostatic pressure. Soil backfill should consist of onsite granular materials. Materials coarser than 3 inches should be segregated from wall backfill prior to use to avoid "point loading". If exterior insulation or drainage boards are used on foundation walls, it may be necessary to use finer backfill soils, in accordance with the manufacturer recommendations. Integrated Testing and Engineering Company Soils and Foundation Investigation Job No. COM 1 C Page 9 In basement construction, an exterior foundation drain around the perimeter of the new structure should be installed. The foundation drain will reduce the risk of "wet basement" conditions and the buildup of hydrostatic pressures. The foundation drain should lead to a positive gravity outlet or a sump where water can be removed by pumping. The foundation drain should be installed similar to the details presented in Appendix B. SURFACE DRAINAGE Positive drainage away from the structure is recommended to reduce the risk for wet basement conditions and improve foundation performance. Use of surface swales or berms should also be considered to divert surface water away from the structure uphill and adjacent to the residence. Additionally, down spouts that discharge uphill of the structure should be redirected to discharge towards the side of the structure. The following precautions should be observed during construction and be maintained at all times after the structure is completed. 1. Excessive wetting or drying of open foundation excavations should be avoided as much as possible during construction. 2. Backfill at foundation walls should be moistened and compacted. Any settlement of backfill after completion of the structure should be immediately filled and positive drainage reestablished. 3. The ground surface surrounding the structures should be sloped to drain away from the structure in all directions. A minimum slope of 12 inches in the first 5 to 10 feet should be developed and maintained after construction. Irrigation should be avoided within 5 to 10 feet of the foundation walls. 4. Roof downspouts and drains should discharge to the surface well beyond the limits of all backfill. Integrated Testing and Engineering Company Soils and Foundation InvestFgation Job No. Ci JC e 1Q 5. Plastic membranes should not be used to cover the ground surface immediately surrounding the structure. These membranes can trap moisture and prevent normal evaporation from occurring. Geotextile fabrics are a suitable option to control weed growth and allow some evaporation. LIMITATIONS Although the test pits were located to obtain a reasonably accurate determination of foundation conditions, variations in the subsoil conditions are possible. Our firm should be contacted if conditions different from those described are encountered in the excavations. Excavations should always be observed by a geotechnical engineer in areas containing soils of the river alluvium silts. The cost of construction observations is not included in this investigation. An environmental assessment of the property is outside our scope of work for this project. If we can be of further service in discussing the contents of this report, or in the analysis of the influence of subsurface conditions on the design of the structures, please call. Respectfully submitted, InTEC of Denver Metro, LLC Reviewed by: �t)r� t'z -� r �. '.; 0 I -4:). c;. t:3 (r., 1. � a - lu e, P.G. Doug L. duse, P.E. Geotechnical Department Manager Denver Branch Manager Addressee: 3 copies sent T Integrated Testing and Englneering Company CERISE RANCH LOT 54 GARFIELD COUNTY, CO 5° GRADE 0° GRADE TP -I TP -2 SUNFLOWER LooP N CHURCH & Associates, Inc. adlvlelonof Integrated Testing and Engineering Comperry of Denver Metro, LLC Geotechnical & On -Site Wastewater Engineering - Environmental Geological Engineering Construction Services InTEC 4501 Wadsworth Boulevard Wheat Ridge, Colorado 80033 Phone:(303) 463-9317 SITE PLAN AND LOCATION OF EXPLORATORY TEST PITS PROJECT NO. C061088 FIGURE 1 Strata Log No. TP -1 Project: Residence Building Project No. C061088 Location: See Test Pit Location Plan Address: Lot 54 Cerise Rnch Carbondale, CO Date Sampled: 07/07/06 Device: Rubber Tire Backhoe Soil Descri stion Topsoil: silt & sand non plastic, dry, red brc Gravel/Cobble sand/silt, rd brn, dry, dense River clayey silts w/ fine sand, rd brn, sl moist, mod stiff (floodpin deposit) NS: Sample Not Recovered Grab Bag Sample (GB) 1 Shelby Tube Sample (ST) 11 California Tube Sample (CS) V- Water encountered during drilling 10 feet 15 20 feet 25 30 feet 35 11.4 LL PI PP -200 72.5 88.2 Refer to Appendix for Additional Information SN=Sample No. and Type CS= California Tube Sample WC=Water Content, LL=Liquid Limit, % NP=Non-Plastic PP=Pocket Penetrometer, tsf -200=% Pass # 200 Sieve DD=Dry Density, pcf GB=Grab Bag Sample PL=Plastic Limit, % P1=Plasticity Index N=SPT Blow Counts "=Blow Counts During Seating Penetration Uc=Unconfined Compression Test, tsf PROJECT NO. C061088 INTEC OF DENVER METRO, LLC. FIGURE 2 Strata Log No. TP -2 Project:Residence Building Project No. C061088 Location: See Test Pit Location Plan Address: Lt 54, Cerise Rnch, Carbndale, CO Date Sampled: 07/07/06 Device: Rubber Tire Backhoe Soil Descri •tion Topsoil fine sandy silt w/ sm cobble Silty/sandy gravel w/ cobble, rd brn, sl moist, occasnl boulders River floodplain clayey & sandy silts, rd brn, sl moist, med stiff Depth SN WC PL LL PI PP N -200 DD Uc 5 10 feet 15 20 feet 25 30 feet 35 NS: Sample Not Recovered Grab Bag Sample (GB) 1 Shelby Tube Sample (ST) California Tube Sample (CS) 0 Water encountered during drilling Refer to Appendix for Additional information SN=Sample No. and Type CS= Califomia Tube Sample WC=Water Content, % LL=Liquid Limit, % N P=Non-Plastic PP=Pocket Penetrometer, tsf -200=% Pass s 200 Sieve DD=Dry Density, pcf GB=Grab Bag Sample PL=Plastic Limit, % PI=Plasticity Index N=SPT Blow Counts ..=Blow Counts During Seating Penetration Uc=Unconfined Compression Test, tsf PROJECT NO. C061083 INTEL OFD ER METRO, LLC. FTGURE 3 1 0 -2 -3 -5 -6 ..4Initial Settlement■'Initial Consolidation •IrFinal Loading CONSOLIDATION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1 10 APPLIED PRESSURE - ksf Natural Dry Unit Weight = 88.2 PCF Natural Moisture Content = 11.4 % Percent Passing #200 Sieve = 72.5% PROJECT NO: C061088 CONSOLIDATION TEST RESULT 100 FIGURE 4 Percent Passing Integrated Testing and Engineering Company of Denver Metro, LLC Geotechnical & on -Site Wastewater Engineering - Environmental & Geological Engineering - Construction Services Phone: 303-463-9317 Fax: 303-463-9321 100.0 90.0 80.0 `r 70.0 60.0 50.0 40.0 C 30.0 20.0 10.0 #200 Gradation Test Results #100 #50 #30 #16 #8 #4 3/8" 3/4" 1 1/2" 3" 0 k- 10 0.0 0.01 0.1 1 Diameter of Particle in Millimeters 20 30 40 5 60 70 80 90 100 10 100 DESCRIPTION:Brown Clayey Silt with gravel GRAVEL 5% SAND 36% FINES 60% MOISTURE 3.1% DATE 7/26/2006 JOB NAME: JOB NUMBERC061088 HOLE / SAMPLE DEPT LIQUID LIMIT PLASTICITY INDEX DRY DENSITY N/A FIGURE 5 Percent Retained 11v 55 v 2 V REPORT OF MOISTURE -DENSITY RELATIONSHIP OF SOIL Tested for: Project: Date: July 26, 2006 Report No: C061088 Soil Description: Sample Location: Sample Preparation: 115.0 114.0 113.0 112.0 0 0 109.0 108.0 107.0 106.0 105.0 Dark Brown Clayey Silt w/ gravel Descritpion Method: 4 -inch mold Structural Fill Test Method: ASTM D 698 (Method A) Rammer Type: MANUAL Liquid Limit: NL Plastic Limit: NL Plasticity Index: NP Dry Method Maximum Dry Density (pcf) 113.9 Optimum Moisture Content (%) 13.3% 8 0 9.0 10.0 11.0 12.0 13.0 14.0 Moisture Content, % Note: v corresponds to the Penetrometer values at each point 15.0 16.0 17,0 18.0 6,c\OL Reviewed by: Dale Plume Geotechnical Department Manager Figure 6 Appendix A Important Information About The Report The data collected by InTEC of Denver Metro, LLC during this investigation was used to provide geotechnical information and recommendations regarding subsurface conditions on thf site investigated, the effect of those conditions on the proposed construction, and the foundation type for the named client. The stratification lines indicated on the boring log are approximate, and subsurface conditions encountered during construction may differ from those presented herein. This uncertainty cannot be eliminated because of the many variabilities associated with geology. For example, material and engineering characteristics of soil and bedrock may change more gradually or more quickly than indicated in this report, and the actual engineering properties of non -sampled soil or rock may differ from interpretations. Quantitative conclusions regarding the performance of geotechnical structures prior to construction are not possible because of the complexity of subsurface conditions. Rather, engineering judgments and experience are used to estimate likely geotechnical performance and provide the necessary recommendations. Put another way, we cannot be sure about what is not visible, so the collected data and our training and experience are used to develop predictions and recommendations. There are no guarantees or warranties implied or expressed. The owner and/or client must understand that uncertainties are associated with geotechnical engineering, and they, the owner and/or client, must determine the level of risk they are willing to accept for the proposed construction. The risks can be reduced, but not eliminated, through more detailed investigation, which costs more money and takes more time, and through any appropriate construction, which might be recommended as a result of . that, more detailed investigation. To reduce the level of uncertainty, this report was prepared only for the referenced client and for the proposed construction indicated in the report. Unless authorized by Church/InTEC in writing, the owner will assume additional geotechnical risk if this report is used for any construction that differs from that indicated in the report. Our firm should be consulted well before changes in the proposed construction occur, such as the nature, size, configuration, orientation, or location of any improvements. Additionally, the knowledge and experience of the local geotechnical practice is continually expanding and it must be understood the presented recommendations were made according to the standard of practice at the time of report issuance. If the construction occurs 1 or more years after issuance of the report, the owner and/or client should contact our firm to determine if additional investigation or revised recommendations would be advisable. The geotechnical practice in the Denver Region must consider the risk associated with expansive soils and bedrock. The geotechnical practice in the Denver area uses a relative scale to evaluate swelling potentials. When the sample is wetted under a surcharge pressure (loading) of 1000 pounds per square foot (PSF), the measured amount of swell is classified as low, moderate, high, or very high. Table 1 presents the relative classification criteria for the percentage of expansion based on initial sample height at the indicated surcharge pressure. Table 1 Risk Category Low Percent Swell Under a 1000 PSF Surcharge Pressure 0—<2 Moderate 2-<4 High 4—<6 Very High 6 or Greater Source: Colorado Association of Geotechnical Engineers, Guideline for Slab Performance Risk Evaluation and Residential Basement Floor System Recommendations (Denver Metropolitan Area), 1996 General Geotechnical Risk Discussion Page 2 The relative classification can be correlated to potential slab damage as follows: Low: slab cracking, differential movement, and heave; moderate: slab cracking and differential movement, partial framing void and furnace plenum closure; and high to very high: large slab cracking and differential movement, closed voids, closed furnace plenum, and possible pipe rupture. (These effects are based on monitoring and observations by several firms in the Denver metropolitan area and are not limited to the relative classification. More or less damage can occur in all classifications because of the uncertainty associated with subsurface conditions and geotechnical engineering.) It is important to note that measured swell or soil expansion is not the only geotechnical criteria for the type of floor and foundation recommendations. Additional criteria considered include: a. soil and bedrock type and variability, b. stratigraphy, c. ground water depth and anticipated post -construction moisture conditions, d. surface water drainage and features, e. post -construction landscaping and irrigation, f. construction details and proposed use, and g. local experience. Post -construction landscaping and owner maintenance will greatly affect structures on expansive soils and bedrock. Typically, irrigated landscaping increases the soil moisture content above the pre - construction water content. Slabs, pavements, and structures significantly reduce evaporation of soil moisture. Therefore, post -construction heave and resulting damage to buildings and other improvements are likely to occur on sites with expansive soils because of the high probability that subsurface moisture content will increase as the property and surrounding area is developed. Poor owner maintenance, such as negative slopes adjacent to foundation walls and irrigated landscaping adjacent to the foundation, also will significantly increase the risk of damage from expansive soil and bedrock. The property owner, and anyone he or she plans to sell the property to, must understand the risks associated with construction in an expansive soil area and also must assume responsibility for maintenance of the structure. The owner and prospective purchasers also should review "A Guide to Swelling Soils for Colorado Homebuyers and Homeowners," which is a special publication (SP 43) produced by the Colorado Geological Survey to assist homeowners in reducing damage caused by swelling soils. BACKFILL '/ SUB -FLOOR PIER f VOID 12" MIN. MIRAFI 140N OR EQUIVALENT GEOTEXTILE FABRIC 12" MIN. ti ti 6" TO 8" MIN. CLEAN, WASHED GRAVEL 4 -INCH DIAMETER PERFORATED PVC PIPE MINIMUM SLOPE OF 1/8" PER FOOT FOR RIGID PIPE MINIMUM SLOPE OF 1/4" PER FOOT FOR FLEXIBLE PIPE NOTES: I. DRAIN PIPE SHOULD LEAD TO SUMP OR POSITIVE GRAVITY DISCHARGE. 2. LINE DRAINAGE TRENCH WITH MIRAFI 140N OR EQUIVALENT GEOTEXTILE FABRIC IN SANDY OR SILTY SOILS. 3. BOTTOM OF DRAIN SHOULD BE A MINIMUM OF 12 INCHES BELOW TOP OF SLAB AT HIGH POINT. 4. GRAVEL SPECIFICATIONS: CLEAN WASHED GRAVEL, 100 % PASSING 1.5", 60-100% RETAINED #4, <3% PASSING #200 IInTECI CHURCH & Associates, Inc. a clMslon of Integrated Testing and Engineertrg Company or Denver Metro, LLC Geclechnical A. Cr 3de Wastewater Ergireerirg - Erwcnrrertat Geoicipcal Enganeerlrg Consbr.'vn SeMfes 4501 Wadsworth Boulevard Wheat Ridge, Colorado 80033 Phone:(303) 463-9317 TYPICAL INTERIOR CRAWL SPACE DRAIN MIRAFI I40N OR EQUIVALENT GEOTEXTILE FABRIC BACKFILL ,•p•(:)04D0� 0 ° 0 °00 o ao 0 ° • WALL SUB FLOOR 4 -INCH DIAMETER PERFORATED PVC PIPE!MINIMUM SLOPE OF 1/8" PER FOOT FOR RIGID PIPE MINIMUM SLOPE OF I/4" PER FOOT AOR FLEXIBLE PIPE 6"-8" MIN. CLEAN WASHED GRAVEL POLYETHYLENE SHEETING 12" MIN 12'• MIN -� \/ PIER FOUNDATION NOTES: I. DRAIN PIPE SHOULD LEAD TO SUMP OR POSITIVE GRAVITY DISCHARGE. 2. COVER GRAVEL COMPLETELY WITH GEOTEXTILE IN SANDY OR SILTY SOILS. 3. BOTTOM OF DRAIN SHOULD BE A MINIMUM OF 12 INCHES BELOW TOP OF SLAB AT HIGH POINT. 4. GRAVEL SPECIFICATIONS: CLEAN WASHED GRAVEL, 100 % PASSING 1.5", 60-100% RETAINED #4, <3% PASSING #200 * MINIMUM SEPARATION PER UBC CODE InTECCHURCH &Associates, Inc..dMslonar Integrated Testing and Engineering Company of Denver Metro, LLC Geciecrncal& On -Ste Wastewater Erg ree„rg . Ervrtcnrrenlai Geological Erg:neer,ng G:rlslricl,Cn aeNCes 4501 Wadsworth Boulevard Wheat Ridge, Colorado 80033 Phone:(303) 463-9317 TYPICAL EXTERIOR BASEMENT WALL DRAIN SPECIFICATIONS FOR EARTHWORK 1.0 SCOPE Page 1 Includes all clearing and grubbing, removal of obstructions, general excavating, grading and filling, and any related items necessary to complete the grading for the entire project in accordance with these specifications. 2.0 SUBSURFACE SOIL DATA Subsurface soil investigations have been made, and the results are available for examination by the contractor. The contractor is expected to examine the site and determine for himself the character of materials to be encountered. No additional allowance will be made for rock removal, site clearing and grading, filling, compaction, disposal, or removal of any unclassified materials. 3.0 CLEARING & GRUBBING A. General: Clearing and grubbing will be required for all areas shown on the plans to be excavated or on which fill is to be constructed. B. Clearing: Clearing shall consist of removal and disposal of trees and other vegetation as well as down timber, snags, brush, existing foundations, slabs, utilities, and rubbish within the areas to be cleared. C. Grubbing: Stumps, matted roots, and roots larger than 2 inches in diameter shall be removed from within 6 inches of the surface of areas on which fills are to be constructed. D. Grass & Topsoil: Grass, grass roots, and incidental topsoil shall not be left beneath a fill area, nor shall this material be used as fill material. Grass, grass roots, and topsoil may be stockpiled and later used in the top 6 inches of fills outside roadways and building pads. 4.0 EARTH EXCAVATION A. Earth excavation shall consist of the excavation and removal of suitable soils for use as embankment or structural fill, as well as the satisfactory disposal of all vegetation, Page 2 existing man-made fill, debris, and deleterious materials encountered within the area to be graded and/or in a borrow area. B. Excavated areas shall be continuously maintained such that the surface shall be smooth and have sufficient slope to allow water to drain from the surface. C. See OSHA safety guidelines for excavation (Title 29 of the Code of Federal Regulation (CFR) Part 1926.650). Contractor shall be responsible for fully complying with this any all other applicable federal and state regulations. 5.0 STRUCTURAL FILL & EMBANKMENT A. General: Embankments shall consist of a controlled fill constructed in areas indicated on the grading plans. B. Materials: (1) Physical Characteristics: Structural fill material shall consist of soils that conform to the minimum following physical characteristics: Maximum size of particles - 11/2" inches; Maximum retained on 3/e inch sieve — 30 percent; Maximum passing No. 100 sieve - 45 percent; Maximum passing No. 200 sieve — 25 percent. The subgrade to receive the fill shall be stripped of all organic growth, rubbish and debris. Controlled fill shall be placed and compacted at a moisture content approximately 2 percent from optimum moisture content. It shall be placed in uniform layers not more than 12 inches thick. Each layer shall be compacted to not less than 95 percent of Standard Proctor density determined in accordance with ASTM standard D698. Fill shall not be placed when frozen, or placed on frozen or wet subgrade. The plasticity index of the material, as determined in accordance with ASTM D4318, shall not exceed 15. Results of our investigation indicate that most of the near surface on-site soils will meet these requirements. Some importation of fill or blending of materials may be required to meet specifications. The fill materials shall be free from roots, grass, other vegetable matter, clay lumps, rocks larger than 6 inches, or other deleterious materials. The existing site soils will be suitable for fill around the exterior of the building and are recommended for this use. Page 3 (2) Borrow: When the quantity of suitable material required for all excavation and grading activities is not available within the limits of the jobsite, the contractor shall provide sufficient materials to construct the grading requirements to the lines, elevations, and cross sections shown on the drawings from borrow areas. The contractor shall obtain from owners of said borrow areas the right to excavate material, shall pay all royalties and other charges involved, and shall pay all expenses in developing the source, including the cost of right-of-way required for hauling the material. C. Construction: (1) Building Area Treatment: Any existing man-made fill, clay or other deleterious material encountered shall be removed in its entirety and replaced with structural fill. Prior to placement of slabs or fill; the building area shall be carefully inspected by a representative of the geotechnical engineer to verify bearing stratum and insure satisfac- tory removal of native soils and the removal of any deleterious material or existing man-made fill. Structural fill should extend a minimum of five feet beyond the perimeter of the structures. Subgrade soils shall be protected during installation of foundations, fill or slabs to minimize moisture loss. The exposed cut surfaces in soil, as well as surfaces to receive fill, shall be scarified to a minimum depth of 10 inches and moisture conditioned as necessary to bring the upper 10 inches to optimum moisture content or above. Where specified in the body of this report, cuts shall be scarified as to the full depth specified. The upper 10 inches of the native soils shall then be compacted to a minimum of 95 percent of maximum dry density as determined in accordance with ASTM D698. Where soft, wet soils are encountered at the bottom of cut surfaces, the surface may be stabilized by working large rock into the subgrade or utilization of lime stabilization or biaxial geogrid reinforcement layer placed on the subgrade. This shall be done only at the discretion of the geotechnical engineer. Where vibratory compaction equipment is used, it shall be the contractor's responsibility to insure that the vibrations do not damage nearby buildings or other adjacent property. (2) Compaction: Fill shall be spread in layers not exceeding 8 inches, watered as necessary, and compacted. Moisture content at the time of compaction shall be 1 percent below optimum moisture or higher. A density of not less than 95 percent of maximum dry density within the building pad shall be obtained for the backfill around the footings and stem walls. A density of not less than 95 percent of maximum dry density within the building pad shall be obtained for structural fill. Structural fill, as well as the native Page 4 soils, outside the building pad area shall be compacted to a minimum 90 percent of maximum dry density. Prior to backfilling and compaction around the foundation wall, the first floor should be installed, and it is recommended that additional lateral support be in place; it is recommended that no backfill should be placed until poured concrete has cured for a minimum of 28 days. Optimum moisture content and maximum dry density for each soil type used shall be determined in accordance with ASTM D698 for native soils and for structural fill. Compaction tests on exposed surfaces should only remain valid for 48 hours if there is no drastic change in existing weather conditions. (3) Weather Limitations: Controlled fill shall not be constructed when the atmospheric temperature is below 35 degrees F. When the temperature falls below 35 degrees, it shall be the responsibility of the contractor to protect all areas of completed work against any detrimental effects of ground freezing by methods approved by the geotechnical engineer. Any areas that are damaged by freezing shall be reconditioned, reshaped, and compacted by the contractor in conformance with the requirements of this specification without additional cost to the owner. D. Slope Protection & Drainage: The edges of the controlled fill embankments shall be graded to the contours shown on the drawings and compacted to the density required in paragraph 5.0 (2). Slopes steeper than 1 vertical to 3 horizontal shall be protected from erosion. 6. INSPECTION & TESTS A. Field Inspection & Testing: The owner shall employ the services of a registered, licensed geotechnical engineer to observe foundation excavations and verify the bearing stratum. The geotechnical engineer shall provide continuous on-site observation by experienced personnel during construction of controlled earthwork. The on-site observer shall maintain a daily field log of all operations, observations, and test results. The contractor shall notify the engineer at least two working days in advance of any field operations of controlled earthwork, or of any resumption of operations after stoppages. Tests of fill materials and subgrade will be made at the following suggested minimum rates: (1) Daily written field observations of construction activities, not limited to, but including: weather conditions, equipment used by the contractor, moisture conditions of on-site soil, soils encountered during excavation or drilling, '1 i Page 5 processes used by the contractor, daily progress, and deviations from specifications. (2) One field density test for each 500 square yards of original ground surface prior to placing fill or constructing floor slabs. (3) One field density test for each 500 cubic yards of fill placed or each layer of fill for each work area, whichever is the greater number of tests. (4) One moisture -density curve for each type of material used, as indicated by sieve analysis and plasticity index. B. Report of Field Density Tests and Construction Observations: The representative of the geotechnical engineer shall submit, daily, the results of field density tests and construction observations required by these specifications to the geotechnical engineer of record, structural engineer, civil engineer and owner, within 48 -hours of tests or observations. C. Costs of Tests & Inspection: The costs of tests, inspection and engineering, as specified in this section of the specifications, shall be borne by the owner. D. Scheduling of Tests & Inspection: The contractor or subcontractor whose work will be monitored shall provide the representative of the geotechnical engineer a minimum of 48 hours notice before commencement of earthwork activities, and 24 hours notice of cancellation of earthwork activities.