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HomeMy WebLinkAboutNEWTON SINGLE-FAMILY DETACHED - BASIC DEVELOPMENT REVIEW - BDR180019 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT400 North Link Lane | Fort Collins, Colorado 80524 Telephone: 970-206-9455 Fax: 970-206-9441 SOIL AND FOUNDATION INVESTIGATION SINGLE-FAMILY RESIDENCE 1516 WEST VINE DRIVE FORT COLLINS, COLORADO Prepared For: ADI CUSTOM, LLC 6547 Nile Circle Arvada, Colorado 80007 Attention: Jordan Ishii Project No. FC07933-120 July 31, 2017 HOME BUYER ADVISORY Although some expansive soils may be present at this site, which could be a geologic hazard, the soils found in our investigation were predominantly non- expansive. The prospective home buyer is strongly advised to read this report and the referenced documents. If you do not understand the important role you must accept to maintain the structure and mitigate risk of excessive wetting, we recommend you contact a competent geotechnical (soils) engineer for advice. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 TABLE OF CONTENTS SCOPE 1 SUMMARY OF CONCLUSIONS 1 SITE CONDITIONS 2 PROPOSED CONSTRUCTION 3 INVESTIGATION 3 SUBSURFACE CONDITIONS 4 Groundwater 4 GEOLOGIC HAZARDS 4 FOUNDATIONS 6 Footings 6 FLOOR SYSTEMS AND SLAB-ON-GRADE FLOORS 7 Slab Performance Risk 7 Structurally Supported Floors 8 Porches, Decks and Patios 9 Garage Slabs and Exterior Flatwork 10 BELOW-GRADE WALLS 10 BACKFILL COMPACTION 11 SUBSURFACE DRAINS AND SURFACE DRAINAGE 12 EXCAVATIONS 14 CONSTRUCTION OBSERVATIONS 14 GEOTECHNICAL RISK 14 LIMITATIONS 15 FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 – SUMMARY LOG OF EXPLORATORY BORINGS FIGURES 3 AND 4 – FOUNDATION WALL DRAIN DETAILS FIGURES 5 AND 6 – RESULTS OF LABORATORY TESTS TABLE I – SUMMARY OF LABORATORY TESTING EXHIBIT A – SLAB PERFORMANCE RISK EVALUATION, INSTALLATION AND MAINTENANCE EXHIBIT B – SURFACE DRAINAGE, IRRIGATION AND MAINTENANCE EXHIBIT C – EXAMPLE BACKFILL COMPACTION ALTERNATIVES ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 1 SCOPE This report presents results of our Soil and Foundation Investigation for the proposed residence at 1516 West Vine Drive in Fort Collins, Colorado. The investigation was conducted to evaluate the subsurface conditions in order to provide geotechnical design and construction recommendations for the residence. The scope was described in our Service Agreement (Proposal No. FC-17-0239, dated June 7, 2017). This report was prepared from data developed during field exploration, laboratory testing, engineering analysis, and experience with similar conditions. It includes our opinions and recommendations for design criteria and construction details for foundations and floor systems, slabs-on-grade, lateral earth loads, and drainage precautions. The report was prepared for the exclusive use of ADI Custom, LLC in design and construction of the single-family residence. Other types of construction may require revision of this report and the recommended design criteria. A brief summary of our conclusions and recommendations follows. Detailed design criteria are presented within the report. SUMMARY OF CONCLUSIONS 1. Soils encountered in our borings consisted of 8 feet of sandy clay over sand and gravel. Claystone bedrock was encountered at 21 feet in one boring to the depth explored. 2. Groundwater was measured during drilling at a depth of 7 to 8 feet and 5 to 8 feet when measured several days later. Existing groundwater levels may limit below grade construction. We recommend a minimum 3-foot separation from foundations and floor systems to groundwater. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 2 3. The presence of expansive soils and bedrock, and possibly collapsing soils, constitutes a geologic hazard. There is risk that slabs-on-grade and foundations will heave or settle and be damaged. We judge the risk is low. We believe the recommendations presented in this report will help to control risk of damage; they will not eliminate that risk. Slabs-on-grade and, in some instances, foundations may be damaged. 4. Footing foundations placed on natural, undisturbed soil and/or properly compacted fill are considered appropriate for this lot. Foundation design and construction recommendations are presented in this report. 5. Soft soils were encountered in our borings. If soft soils are encountered at the bottom of the foundation excavation, stabilization can likely be achieved by crowding 1½ to 3-inch nominal size crushed rock into the subsoils until the base of the excavation does not deform by more than about ½-inch when compactive effort is applied. 6. There is a low risk of poor basement floor slab performance. A slab- on-grade floor can be used for the bottom level. Driveways and other exterior flatwork will be slabs-on-grade and may heave or settle and crack. 7. Surface drainage should be designed, constructed and maintained to provide rapid removal of surface runoff away from the proposed residence. Conservative irrigation practices should be followed to avoid excessive wetting. 8. The design and construction criteria for foundations and floor system alternatives in this report were compiled with the expectation that all other recommendations presented related to surface and subsurface drainage, landscaping irrigation, backfill compaction, etc. will be incorporated into the project and that the owner will maintain the structure, use prudent irrigation practices and maintain surface drainage. It is critical that all recommendations in this report are followed. SITE CONDITIONS The lot is located at 1516 West Vine Drive in Fort Collins, Colorado (Figure 1). During the time of our investigation, overlot grading and installation of buried utilities were not complete. An access drive for other existing structures is already ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 3 in place. The lot slopes down gradually to the south. An existing residence is located to the northeast of the proposed construction. The Cache La Poudre River is located a half mile to the northeast. In the same area, a system of ponds and an irrigation ditch are present. Ground cover consisted of natural grasses, weeds and some trees. PROPOSED CONSTRUCTION The proposed residence is anticipated to be a wood-framed, two-story structure with an attached garage. The residence may have partial brick or stone exterior veneer. Foundation loads are expected to vary between 1,000 and 3,000 pounds per lineal foot of foundation wall, with individual column loads of 25 kips or less. Excavations for below grade areas will be limited by the depth of groundwater. INVESTIGATION The field investigation included drilling two exploratory borings at the approximate locations presented on Figure 1. The borings were drilled to depths of approximately 20 feet and 30 feet using 4-inch diameter, continuous-flight augers and a truck-mounted drill. Drilling was observed by our field representative who logged the soils and bedrock. Summary logs of the borings, including results of field penetration resistance tests, are presented on Figure 2. Soil and bedrock samples obtained during drilling were returned to our laboratory and visually examined by our geotechnical engineer. Laboratory testing was assigned and included moisture content, dry density, swell-consolidation, particle-size analysis and soluble sulfate concentration. Swell-consolidation tests were wetted at a confining pressure which approximated the weight of overlying soils (overburden pressures). Results of the laboratory tests are presented on Figures 6 through 8 and summarized in Table I. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 4 SUBSURFACE CONDITIONS Subsurface conditions encountered in our borings consisted of 8 feet of sandy clay over sand and gravel. Claystone bedrock was encountered in one boring at 21 feet to the depth explored. Samples of the clay soils tested indicated 0.1 percent compression to 0.5 percent swell. Further descriptions of the subsurface conditions are presented on our boring logs and in our laboratory test results. Groundwater Groundwater was measured during drilling at depths of 7 to 8 feet. When measured several days later, groundwater was encountered at depths of 5 to 8 feet. Groundwater may develop on or near low permeable soil when a source of water not presently contributing becomes available. Groundwater levels are expected to fluctuate seasonally and with water levels in the nearby river and pond complex. Groundwater is expected to affect below-grade construction at the site. We recommend a minimum 3-foot separation from groundwater to foundations and floor systems. GEOLOGIC HAZARDS Colorado is a challenging location to practice geotechnical engineering. The climate is relatively dry and the near-surface soils are typically dry and relatively stiff. These soils and related sedimentary bedrock formations tend to react to changes in moisture conditions. Some of the soils and bedrock swell as they increase in moisture and are called expansive soils. Other soils can settle significantly upon wetting and are referred to as collapsing soils. Most of the land available for development east of the Front Range is underlain by expansive clay or claystone bedrock near the surface. The soils that exhibit collapse are more likely west of the continental divide; however, both types of soils occur all over the state. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 5 Covering the ground with houses, streets, driveways, patios, etc., coupled with lawn irrigation and changing drainage patterns, leads to an increase in subsurface moisture conditions. As a result, some soil movement is inevitable. It is critical that all recommendations in this report are followed to increase the chances that the foundations and slabs-on-grade will perform satisfactorily. After construction, home owners must assume responsibility for maintaining the structure and use appropriate practices regarding drainage and landscaping. Expansive soils and bedrock are present at this site. The presence of expansive soils and bedrock, collectively referred to as expansive or swelling soils, constitutes a geologic hazard. Some near-surface soils may also compress, or collapse, when wetted. There is risk that ground heave or settlement will damage slabs-on-grade and foundations. The risks associated with swelling and compressible soils can be mitigated, but not eliminated by careful design, construction and maintenance procedures. We believe the recommendations in this report will help control risk of foundation and/or slab damage; they will not eliminate that risk. The builder and homebuyer should understand that slabs-on-grade and, in some instances, foundations may be affected. Homeowner maintenance will be required to control risk. We recommend the builder provide a booklet to the homebuyer that describes swelling soils and includes recommendations for care and maintenance of homes constructed on expansive soils. Colorado Geological Survey Special Publication 431 was designed to provide this information. 1“A Guide to Swelling Soils for Colorado Homebuyers and Homeowners,” Second Edition Revised and Updated by David C. Noe, Colorado Geological Survey, Department of Natural Resources, Denver, Colorado, 2007. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 6 FOUNDATIONS Our investigation indicates low-swelling soils were encountered at depths where they are likely to affect foundation performance. Footing foundations are considered appropriate for the proposed construction. Design criteria for footing foundations developed from analysis of field and laboratory data and our experience are presented below. The builder and structural engineer should also consider design and construction details established by the structural warrantor (if any) that may impose additional design and installation requirements. Footings 1. The footing foundation should bear on undisturbed natural soils and/or on properly compacted fill. Where soils are loosened during excavation or in the footing forming process, the soils should be removed or compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99) between optimum and 3 percent above optimum moisture content, prior to placing concrete. Excavation backfill placed below foundations should be compacted using the same specifications. 2. Soft soils were encountered in our borings. If soft soils are encountered at the bottom of the foundation excavation, stabilization can likely be achieved by crowding 1½ to 3-inch nominal size crushed rock into the subsoils until the base of the excavation does not deform by more than about ½-inch when compactive effort is applied. Soft soil may be displaced if wheeled equipment is used in the excavations. We recommend wheeled excavators not be allowed in the excavations. 3. Footings should be designed for a net allowable soil pressure of 1,500 pounds per square foot (psf). The structural engineer should vary the width of the footings so as to balance the dead load pressure on the soil. There shall be a minimum 3-foot separation from the footings to groundwater. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 7 4. We anticipate footings designed using the soil pressure recommended above could experience 1-inch of movement. Differential movements of ½-inch should be considered in the design. 5. Footings should have a minimum width of 16 inches. Foundations for isolated columns should have minimum dimensions of 20 inches by 20 inches. Larger sizes may be required depending upon the loads and structural system used. 6. Foundation walls should be well reinforced, top and bottom. We recommend reinforcement sufficient to span an unsupported distance of at least 10 feet or the distance between pads whichever is greater. Reinforcement should be designed by the structural engineer considering the effects of large openings and lateral loads on wall performance. 7. The soil below exterior footings must be protected from frost action. Normally, 30 inches of cover over footings is assumed in the area for frost protection. 8. The completed foundation excavation should be observed by a representative of our firm prior to placing the forms to verify subsurface conditions are as anticipated from our borings. Our representative should also observe the placement and test compaction of new fill placed for foundation subgrade (if merited). FLOOR SYSTEMS AND SLAB-ON-GRADE FLOORS Slab Performance Risk We conducted swell-consolidation testing to provide a basis for calculating potential soil heave at this site. We estimate potential heave of 1 inch or less for the lots included. A depth of wetting of 24 feet was considered for our heave evaluation. Recent research (Walsh, Colby, Houston and Houston, ASCE, 2009) indicates there is a 90 percent probability that the wetting depth will not exceed 24 feet in this region, suggesting that the risk of ground heave exceeding the estimated values is low. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 8 Based on our heave calculations, the subsurface conditions found in our borings, and our experience with residence construction and performance, we judge that the risk of poor slab-on-grade performance at this site is low. Our experience indicates that basement slab performance is generally satisfactory on low risk sites. Slab heave of 1 to 2 inches is considered “normal” for these sites; more or less heave can occur. If floor movements cannot be tolerated, home buyers should select a lot where a structurally supported floor system is constructed or request that one be installed. A more detailed discussion of slab- on-grade performance risk and construction recommendations is provided in Exhibit A. Structurally Supported Floors Structural floors should be used in non-basement, finished living areas and in the basement if floor movement and cracking are unacceptable. A structural floor is supported by the foundation system. There are design and construction issues associated with structural floors that must be considered, such as ventilation and lateral loads. Where structurally supported floors are installed, the required air space depends on the materials used to construct the floor and the expansion potential of the underlying soils. Building codes require a clear space of 18 inches above exposed earth if untreated wood floor components are used. Where other floor support materials are used, a minimum clear space of 8 inches should be maintained. This minimum clear space should be maintained between any point on the underside of the floor system (including beams and floor drain traps) and the surface of the exposed earth. Where structurally supported floors are used, utility connections, including water, gas, air duct and exhaust stack connections to floor supported appliances, should be capable of absorbing some deflection of the floor. Plumbing that passes through the floor should ideally be hung from the underside of the structural floor ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 9 and not lain on the bottom of the excavation. This configuration may not be achievable for some parts of the installation. It is prudent to maintain the minimum clear space below all plumbing lines. If trenching below the lines is necessary, we recommend sloping these trenches so they discharge to the foundation drains. Control of humidity in crawl spaces is important for indoor air quality and performance of wood floor systems. We believe the best current practices to control humidity involve the use of a vapor retarder (10-mil minimum), placed on the exposed soils below accessible sub-floor areas. The vapor retarder should be sealed at joints and attached to concrete foundation elements. If desired, we can provide designs for ventilation systems that can be installed in association with a vapor retarder, to improve control of humidity in crawl space areas. The Moisture Management Task Force of Metro Denver2 has compiled additional discussion and recommendations regarding best practices for the control of humidity in below- grade, under-floor spaces. Porches, Decks and Patios Porches or decks with overhanging roofs that are integral with the residence such that excessive foundation movement cannot be tolerated, should be constructed with the same foundation type as the house. Simple decks, that are not integral with the residence and can tolerate foundation movement, can be constructed with less substantial foundations. A short pier or footing bottomed at least 3 feet below grade can be used if movement is acceptable. Use of 8-foot to 10-foot piers can reduce potential movement. Footings or short piers should not be bottomed in wall backfill due to risk of settlement. The inner edge of the deck may be constructed on haunches or steel angles bolted to the foundation walls and detailed such that movement of the deck foundation will not cause distress to 2 “Guidelines for Design and Construction of New Homes with Below-Grade Under-Floor Spaces,” Moisture Management Task Force, October 30, 2003. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 10 the residence. We suggest use of adjustable bracket-type connections or other details between foundations and deck posts so the posts can be trimmed or adjusted if movement occurs. Porches, patio slabs and other exterior flatwork should be isolated from the structures. Porch slabs can be constructed to reduce the likelihood that settlement or heave will affect the slabs. One approach (for smaller porches located over basement backfill zones) is to place loose backfill under a structurally supported slab. This fill will more likely settle than swell, and can thus accommodate some heave of the underlying soils. A lower risk approach is to construct the porch slab over void-forming materials. Conditions should allow the void-forming materials to soften quickly after construction to reduce the risk of transmitting ground heave to the porch slab. Wax or plastic-coated void boxes should not be used unless provisions are made to allow water to penetrate into the boxes. Garage Slabs and Exterior Flatwork Garage floor slabs, driveways and sidewalks are normally constructed as slabs-on-grade. Various properties of the soils and environmental conditions influence magnitude of movement and other performance characteristics of slabs underlain by expansive soils. Increases in the moisture content of expansive soils will cause heaving and may result in cracking of slabs-on-grade. Backfill below slabs should be moisture conditioned and compacted to reduce settlement, as discussed in BACKFILL COMPACTION. Driveways and exterior slabs founded on the backfill may settle and crack if the backfill is not properly moisture treated and compacted BELOW-GRADE WALLS Basement and/or foundation walls and grade beams that extend below grade should be designed for lateral earth pressures where backfill is not present ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 11 to about the same extent on both sides of the wall. Many factors affect the value 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 that can deflect or rotate 0.5 to 1 percent of the wall height (depending upon the backfill types), lower "active" lateral earth pressures are appropriate. Our experience indicates basement walls can deflect or rotate slightly under normal design loads and that this deflection results in satisfactory wall performance. Thus, the earth pressure on the walls will likely be between the "active" and "at-rest" conditions. If on-site soils are used as backfill and the backfill is not saturated, we recommend design of basement walls at this site using an equivalent fluid density of at least 55 pounds per cubic foot (pcf). This value assumes deflection; some minor cracking of walls may occur. If very little wall deflection is desired, higher design density may be appropriate. The structural engineer should also consider site-specific grade restrictions and the effects of large openings on the behavior of the walls. BACKFILL COMPACTION Settlement of foundation wall and utility trench backfill can cause damage to concrete flatwork and/or result in poor drainage conditions. Compaction of backfill can reduce settlement. Attempts to compact backfill near foundations to a high degree can damage foundation walls and window wells and may increase lateral pressures on the foundation walls. The potential for cracking of a foundation wall can vary widely based on many factors including the degree of compaction achieved, the weight and type of compaction equipment utilized, the structural design of the wall, the strength of the concrete at the time of backfill compaction, and the presence of temporary or permanent bracing. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 12 Proper moisture conditioning of backfill is as important as compaction, because settlement commonly occurs in response to wetting. The addition of water complicates the backfill process, especially during cold weather. Frozen soils are not considered suitable for use as backfill because excessive settlement can result when the frozen materials thaw. Exhibit C describes four alternative methods to place, moisture condition, and compact backfill along with a range of possible settlements, and advantages and disadvantages of each approach, all based upon our experience. These are just a few of the possible techniques, and represent a range for your evaluation. We recommend Alternatives C or D if you wish to control potential settlement. Precautions should be taken when backfilling against a basement wall. Temporary bracing of comparatively long, straight sections of foundation walls should be used to limit damage to walls during the compaction process. Waiting at least seven days after the walls are placed to allow the concrete to gain strength can also reduce the risk of damage. Compaction of fill placed beneath and next to window wells, counterforts, and grade beams may be difficult to achieve without damaging these building elements. Proper moisture conditioning of the fill prior to placement in these areas will help reduce potential settlement. Ideally, drainage swales should not be located over the backfill zone (including excavation ramps), as this can increase the amount of water infiltration into the backfill and cause excessive settlement. Swales should be designed to be a minimum of at least 5 feet from the foundation to help reduce water infiltration. Irrigated vegetation, sump pump discharge pipes, sprinkler valve boxes, and roof downspout terminations should also be at least 5 feet from the foundation. SUBSURFACE DRAINS AND SURFACE DRAINAGE Water from surface irrigation of lawns and landscaping frequently flows through relatively permeable backfill placed adjacent to a residence and collects ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 13 on the surface of less permeable soils occurring at the bottom of basement or foundation excavations. This process can cause wet or moist conditions in below grade areas after construction. To reduce the likelihood water pressure will develop outside foundation walls and the risk of accumulation of water in below grade areas, we recommend provision of an exterior foundation drain around the perimeter of the foundation excavation. In addition, crawl spaces should be well ventilated per building code. The provision of a drain will not eliminate slab movement or prevent moist conditions in crawl spaces. The exterior drain should consist of a 4-inch diameter open joint or slotted pipe encased in free draining gravel. The drain should lead to a positive gravity outlet, such as a sub-drain located beneath the sewer, or to a sump where water can be removed by pumping. If the drain discharges to the ground surface, the outlet should be a permanent fixture that provides protection from blockage from vegetation or other sources. Typical foundation drain details are presented on Figures 3 and 4. Our experience indicates moist conditions can develop in non-basement crawl space areas resulting in isolated instances of damp soils, musty smells and, in rare cases, standing water. Crawl space areas should be well ventilated, depending on the use of a vapor retarder on the exposed soils and the floor material selected. Some builders install drain systems around non-basement crawl space areas as a precaution; we regard these installations as optional. Drains can be added after construction if unusually moist conditions develop. Proper design, construction and maintenance of surface drainage are critical to the satisfactory performance of foundations, slabs-on-grade and other improvements. Landscaping and irrigation practices will also affect performance. Exhibit B contains our recommendations for surface drainage, irrigation and maintenance. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 14 EXCAVATIONS Excavations made at this site, including those for the foundation and utilities, may be governed by local, state, or federal guidelines or regulations. Subcontractors should be familiar with these regulations and take whatever precautions they deem necessary to comply with the requirements and thereby protect the safety of their employees and that of the general public. Some of the soils are soft and will be displaced if wheeled equipment is used in the excavations. We recommend wheeled traffic not be allowed in the excavations. CONSTRUCTION OBSERVATIONS We recommend that CTL | Thompson, Inc. provide construction observation services to allow us the opportunity to verify whether soil conditions are consistent with those found during this investigation. Other observations are recommended to review general conformance with design plans. If others perform these observations, they must accept responsibility to judge whether the recommendations in this report remain appropriate. GEOTECHNICAL RISK The concept of risk is an important aspect with any geotechnical evaluation primarily because the methods used to develop geotechnical recommendations do not comprise an exact science. We never have complete knowledge of subsurface conditions. Our analysis must be tempered with engineering judgment and experience. Therefore, the recommendations presented in any geotechnical evaluation should not be considered risk-free. Our recommendations represent our judgment of those measures that are necessary to increase the chances that the structure will perform satisfactorily. It is critical that all recommendations in this report are followed during construction. Home owners must assume responsibility for maintaining the structure and use appropriate practices regarding drainage and ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 15 landscaping. Improvements performed by home owners after construction, such as finishing a basement or construction of additions, retaining walls, decks, patios, landscaping and exterior flatwork, should be completed in accordance with recommendations in this report. LIMITATIONS This report has been prepared for the exclusive use by ADI Custom, LLC for the purpose of providing geotechnical design and construction criteria for the proposed project. The information, conclusions, and recommendations presented herein are based upon consideration of many factors including, but not limited to, the type of structure proposed, the geologic setting, and the subsurface conditions encountered. The conclusions and recommendations contained in the report are not valid for use by others. Standards of practice evolve in the area of geotechnical engineering. The recommendations provided are appropriate for about three years. If the proposed residence is not constructed within about three years, we should be contacted to determine if we should update this report. Two borings were drilled during this investigation to obtain a reasonably accurate picture of the subsurface conditions. Variations in the subsurface conditions not indicated by our borings are possible. A representative of our firm should observe the foundation excavation to confirm the exposed materials are as anticipated from our borings. We should also test compaction of fill if over- excavation is used. We believe this investigation was conducted with that level of skill and care ordinarily used by geotechnical engineers practicing in this area at this time. No warranty, express or implied, is made. TH-1 TH-2 VINE DR. AZTEC DR. SHIELDS ST. LYON ST. LANCER DR. SITE LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING TH-1 ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL I T PROJECT NO. FC07933-120 FIGURE 1 Locations of Exploratory Borings VICINITY MAP (FORT COLLINS, COLORADO) NOT TO SCALE 100' APPROXIMATE SCALE: 1" = 100' 4,980 4,985 4,990 4,995 5,000 5,005 5,010 5,015 5,020 5,025 4,980 4,985 4,990 4,995 5,000 5,005 5,010 5,015 5,020 5,025 6/12 WC=21.4 DD=107 SW=0.5 34/12 WC=6.0 -200=5 TH-1 El. 5024.0 4/12 WC=22.1 DD=104 SW=-0.1 SS=0.010 20/12 WC=9.5 -200=7 TH-2 El. 5024.0 CLAY, SANDY, MOIST TO WET, MEDIUM STIFF, DARK BROWN (CL) LEGEND: THE BORINGS WERE DRILLED ON JUNE 29, 2017, USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. BULK SAMPLE FROM AUGER CUTTINGS. WATER LEVEL MEASURED AT TIME OF DRILLING. WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING. 1. DRIVE SAMPLE. THE SYMBOL 6/12 INDICATES 6 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. Borings Summary Logs of Exploratory ELEVATION - FEET ELEVATION - FEET NOTES: FIGURE 2 ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL|T PROJECT NO. FC07933-120 FIGURE 3 ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL|T PROJECT NO. FC07933-120 FIGURE 4 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT= 107 PCF From TH - 1 AT 2 FEET MOISTURE CONTENT= 21.4 % Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT= 104 PCF From TH - 2 AT 4 FEET MOISTURE CONTENT= 22.1 % ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL | T PROJECT NO. FC07933-120 APPLIED PRESSURE - KSF APPLIED PRESSURE - KSF COMPRESSION % EXPANSION Swell Consolidation FIGURE 5 COMPRESSION % EXPANSION -4 -3 -2 -1 0 1 2 3 EXPNSUND AC ION ER ONS TA N T PREDUE SSU RE TO W ETT IN G -4 -3 -2 -1 0 1 2 3 A D D IT I O NAL CO MPRE SSI ON U ND E R C O N S T ANTSSURD PRE E UE T O WE T T I NG 0.1 1.0 10 100 0.1 1.0 10 100 Sample of GRAVEL, SANDY (GW) GRAVEL 53 % SAND 42 % From TH - 1 AT 9 FEET SILT & CLAY 5 % LIQUID LIMIT % PLASTICITY INDEX % Sample of GRAVEL % SAND % From SILT & CLAY % LIQUID LIMIT % PLASTICITY INDEX % ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL | T PROJECT NO. FC07933-120 Gradation Test Results FIGURE 6 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 PASSING WATER- MOISTURE DRY APPLIED NO. 200 SOLUBLE DEPTH CONTENT DENSITY SWELL* PRESSURE SIEVE SULFATES BORING (FEET) (%) (PCF) (%) (PSF) (%) (%) DESCRIPTION TH-1 2 21.4 107 0.5 200 CLAY, SANDY (CL) TH-1 9 6.0 5 GRAVEL, SANDY (GW) TH-2 4 22.1 104 -0.1 500 0.01 CLAY, SANDY (CL) TH-2 9 9.5 7 SAND, SLIGHTLY SILTY (SP-SM) SWELL TEST RESULTS* TABLE I SUMMARY OF LABORATORY TESTING Page 1 of 1 * NEGATIVE VALUE INDICATES COMPRESSION. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL|T PROJECT NO. FC07933-120 ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT A-1 EXHIBIT A SLAB PERFORMANCE RISK EVALUATION, INSTALLATION AND MAINTENANCE As part of our evaluation of the subsurface soils and bedrock, samples were tested in the laboratory using a swell test. In the test procedure, a relatively undisturbed sample obtained during drilling is first loaded and then flooded with water and allowed to swell. The pressure applied prior to wetting can approximate the weight of soil above the sample depth or be some standard load. The measured percent swell is not the sole criteria in assessing potential movement of slabs-on-grade and the risk of poor slab performance. The results of a swell test on an individual lot are tempered with data from surrounding lots, depth of tests, depth of excavation, soil profile, and other tests. This judgment has been described by the Colorado Association of Geotechnical Engineers3 (CAGE, 1996) as it relates to basement slab-on-grade floors. It can also be used to help judge performance risk for other slabs-on-grade such as garage floors, driveways, and sidewalks. The risk evaluation is considered when we evaluate appropriate foundation systems for a given site. In general, more conservative foundation designs are used for higher risk sites to control the likelihood of excessive foundation movement. As a result of the Slab Performance Risk Evaluation, sites are categorized as low, moderate, high, or very high risk. This is a judgment of the swelling characteristics of the soils and bedrock likely to influence slab performance. REPRESENTATIVE MEASURED SWELL AND CORRESPONDING SLAB PERFORMANCE RISK CATEGORIES Slab Performance Risk Category Representative Percent Swell* (500 psf Surcharge) Representative Percent Swell* (1000 psf Surcharge) Low 0 to <3 0 to <2 Moderate 3 to <5 2 to <4 High 5 to <8 4 to <6 Very High > 8 > 6 *Note: The representative percent swell values presented are not necessarily measured values; rather, they are a judgment of the swelling characteristics of the soil and bedrock likely to influence slab performance. 3”Guideline for Slab Performance Risk Evaluation and Residential Basement Floor System Recommendations”, Colorado Association of Geotechnical Engineers, December 1996. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT A-2 The rating of slab performance risk on a site as low or high is not absolute. Rather, this rating represents a judgment. Movement of slabs may occur with time in low, moderate, high, and very high risk areas as the expansive soils respond to increases in moisture content. Overall, the severity and frequency of slab damage usually is greater in high and very high rated areas. Heave of slabs-on-grade of 3 to 5 inches is not uncommon in areas rated as high or very high risk. On low and moderate risk sites, slab heave of 1 to 2 inches is considered normal and we believe in the majority of instances, movements of this magnitude constitute reasonable slab performance; more heave can occur. Slabs can be affected on all sites. The home buyer should be advised the floor slab in the basement may move and crack due to heave or settlement and that there may be maintenance costs associated during and after the builder warranty period. A buyer who chooses to finish a basement area must accept the risk of slab heave, cracking and consequential damages. Heave or settlement may require maintenance of finish details to control damage. Our experience suggests that soil moisture increases below residence sites due to covering the ground with the house and exterior flatwork, coupled with the introduction of landscape irrigation. In most cases, slab movements (if any) resulting from this change occur within three to five years. We suggest delaying finish in basements with slab-on-grade floors until at least three years after start of irrigation. It is possible basement floor slab and finish work performance will be satisfactory if a basement is finished earlier, particularly on low risk sites. For portions of the houses where conventional slabs-on-grade are used, we recommend the following precautions. These measures will not keep slabs-on- grade from heaving; they tend to mitigate damages due to slab heave. 1. Slab-on-grade floor construction should be limited to areas such as garages and basements where slab movement and cracking are acceptable to the builder and home buyer. 2. The 2015 International Residential Code (IRC R506) states that a 4- inch base course layer consisting of clean graded sand, gravel, crushed stone or crushed blast furnace slag shall be placed beneath below grade floors (unless the underlying soils are free-draining), along with a vapor retarder. Installation of the base course and vapor retarder is not common in this area. Historically, there has been some concern that installation of clean base course could allow wetting of expansive soils to spread from an isolated source. IRC states that the vapor retarder can be omitted where approved by the building official. The merits of installation of a vapor retarder below floor slabs depend on the sensitivity of floor coverings and ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT A-3 building use to moisture. A properly installed vapor retarder is more beneficial below concrete slab-on-grade floors where floor coverings, painted floor surfaces, or products stored on the floor will be sensitive to moisture. The vapor retarder is most effective when concrete is placed directly on top of it, rather than placing a sand or gravel leveling course between the vapor retarder and the floor slab. Placement of concrete on the vapor retarder may increase the risk of shrinkage cracking and curling. Use of concrete with reduced shrinkage characteristics including minimized water content, maximized coarse aggregate content, and reasonably low slump will reduce the risk of shrinkage cracking and curling. Considerations and recommendations for the installation of vapor retarders below concrete slabs are outlined in Section 3.2.3 of the 2006 American Concrete Institute (ACI) Committee 302, “Guide for Concrete Floor and Slab Construction (ACI 302.R-96)”. 3. Conventional slabs should be separated from exterior walls and interior bearing members with a slip joint that allows free vertical movement of the slabs. These joints must be maintained by the home buyer to avoid transfer of movement. 4. Underslab plumbing should be thoroughly pressure tested during construction for leaks and be provided with flexible couplings. Gas and waterlines leading to slab-supported appliances should be constructed with flexibility. The homebuyer must maintain these connections. 5. Use of slab bearing partitions should be minimized. Where such partitions are necessary, a slip joint (or float) allowing at least 3 inches of free vertical slab movement should be used. Doorways should also be designed to allow vertical movement of slabs. To limit damage in the event of movement, sheetrock should not extend to the floor. The home buyer should monitor partition voids and other connections and re-establish the voids before they close to less than 1/2-inch. 6. Plumbing and utilities that pass through slabs should be isolated from the slabs. Heating and air conditioning systems constructed on slabs should be provided with flexible connections capable of at least 3 inches of vertical movement so slab movement is not transmitted to the ductwork. These connections must be maintained by the home buyer. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT A-4 7. Roofs that overhang a patio or porch should be constructed on the same foundation as the residence. Isolated piers or pads may be installed beneath a roof overhang provided the slab is independent of the foundation elements. Patio or porch roof columns may be positioned on the slab, directly above the foundation system, provided the slab is structural and supported by the foundation system. Structural porch or patio slabs should be constructed to reduce the likelihood that settlement or heave will affect the slab by placing loose backfill under the structurally supported slab or constructing the slab over void-forming materials. 8. Patio and porch slabs without roofs and other exterior flatwork should be isolated from the foundation. Movements of slabs should not be transmitted to the foundation. Decks are more flexible and more easily adjusted in the event of movement. 9. Frequent control joints should be provided in conventional slabs-on- grade to reduce problems associated with shrinkage cracking and curling. Panels that are approximately square generally perform better than rectangular areas. We suggest an additional joint about 3 feet away from and parallel to foundation walls. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT B-1 EXHIBIT B SURFACE DRAINAGE, IRRIGATION AND MAINTENANCE Performance of foundations and concrete flatwork is influenced by the moisture conditions existing within the foundation soils. Surface drainage should be designed to provide rapid runoff of surface water away from proposed residences. Proper surface drainage and irrigation practices can help control the amount of surface water that penetrates to foundation levels and contributes to settlement or heave of soils and bedrock that support foundations and slabs-on- grade. Positive drainage away from the foundation and avoidance of irrigation near the foundation also help to avoid excessive wetting of backfill soils, which can lead to increased backfill settlement and possibly to higher lateral earth pressures, due to increased weight and reduced strength of the backfill. CTL | Thompson, Inc. recommends the following precautions. The homebuyer should maintain surface drainage and, if an irrigation system is installed, it should substantially conform to these recommendations. 1. Wetting or drying of the open foundation excavations should be avoided. 2. Excessive wetting of foundation soils before, during and after construction can cause heave or softening of foundation soils and result in foundation and slab movements. Proper surface drainage around the residence and between lots is critical to control wetting. 3. The ground surface surrounding the exterior of each residence should be sloped to drain away from the building in all directions. We recommend a minimum constructed slope of at least 12 inches in the first 10 feet (10 percent) in landscaped areas around each residence, where practical. The recommended slope is for the soil surface slope, not surface of landscaping rock. 4. We do not view the recommendation to provide a 10 percent slope away from the foundation as an absolute. It is desirable to create this slope where practical, because we know that backfill will likely settle to some degree. By starting with sufficient slope, positive drainage can be maintained for most settlement conditions. There are many situations around a residence where a 10 percent slope cannot be achieved practically, such as around patios, at inside foundation corners, and between a house and nearby sidewalk. In these areas, we believe it is desirable to establish as much slope as practical and to avoid irrigation. We believe it is acceptable to use a slope on the order of 5 percent perpendicular to the foundation in these limited areas. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT B-2 5. For lots graded to direct drainage from the rear yard to the front, it is difficult to achieve 10 percent slope at the high point behind the house. We believe it is acceptable to use a slope of about 6 inches in the first 10 feet (5 percent) at this location. 6. Between houses that are separated by a distance of less than 20 feet, the constructed slope should generally be at least 10 percent to the swale used to convey water out of this area. For lots that are graded to drain to the front and back, we believe it is acceptable to install a slope of 5 to 8 percent at the high point (aka “break point”) between houses. 7. Construction of retaining walls and decks adjacent to the residence should not alter the recommended slopes and surface drainage around the residence. The ground surface under decks should be compacted and slope away from the residence. 10-mil plastic sheeting and landscaping rock may be placed under decks to soil erosion and/or formation of depressions under the deck. The plastic sheeting should direct water away from the residence. Retaining walls should not flatten the surface drainage around the residence or impede surface runoff. 8. Swales used to convey water across yards and between houses should be sloped so that water moves quickly and does not pond for extended periods of time. We suggest minimum slopes of about 2 to 2.5 percent in grassed areas and about 2 percent where landscaping rock or other materials are present. If slopes less than about 2 percent are necessary, concrete-lined channels or plastic pipe should be used. Fence posts, trees, and retaining walls should not impede runoff in the swales. 9. Backfill around the foundation walls should be moistened and compacted. 10. Roof downspouts and drains should discharge well beyond the limits of all backfill. Splash blocks and/or extensions should be provided at all downspouts so water discharges onto the ground beyond the backfill. We generally recommend against burial of downspout discharge. Where it is necessary to bury downspout discharge, solid, rigid pipe should be used and it should slope to an open gravity outlet. Downspout extensions, splash blocks and buried outlets must be maintained by the home owner. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT B-3 11. The importance of proper irrigation and drainage practices and maintenance cannot be over-emphasized. Irrigation should be limited to the minimum amount sufficient to maintain vegetation; application of more water will increase likelihood of slab and foundation movements. Landscaping should be carefully designed and maintained to minimize irrigation. Plants placed close to foundations, particularly within 5 feet of the foundation, should be limited to those with low moisture requirements and utilize only sub- surface irrigation such as standard low volume drip emitters or in-line drip irrigation. Irrigated grass, irrigation mainlines, above-surface spray heads, rotors, and other above-surface irrigation spray devices should not be located or discharge above the ground surface within 5 feet of the foundation Home owners should periodically check and maintain landscaping and irrigation systems to control introduction of surface water. This maintenance should include, but not be limited to:  Assure proper ground surface slope (not landscape rock) away from the house (yearly)  Orient downspout extensions and splash blocks away from the foundation (monthly). Keep downspout tip-ups in the down position where splash blocks are not present.  Clean roof gutters (yearly)  Check and, if necessary, repair the irrigation system (backflow preventer, sprinkler heads, drip system heads and pipe) to assure the system components are intact, do not leak, and that spray is directed away from foundations (twice a year). 12. Plastic sheeting should not be placed beneath landscaped areas adjacent to foundation walls or grade beams. Geotextile fabric will inhibit weed growth yet still allow natural evaporation to occur. ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTLT PROJECT NO. FC07933-120 EXHIBIT C-1 EXHIBIT C EXAMPLE BACKFILL COMPACTION ALTERNATIVES Alt. Description Possible Settlement Pros (+) / Cons (-) A Place in 18 to 24-inch lifts, without moisture conditioning. Compact lift surface to about 85 percent of maximum standard Proctor (ASTM D698) dry density. (not recommended) 5 to 15 percent of depth (for 8 feet of backfill, 5 to 15 inches) + Fast + Water not required - Excessive Settlement - Highest water penetration - Highest probability of warranty repair B Moisture condition within 2 percent of optimum, place in 12 to 18-inch lifts. Compact lift surface to about 85 to 90 percent. 5 to 10 percent of depth + Relatively Fast - Moderate water penetration - Excessive settlement - Need for water - Warranty repairs probable C Moisture condition to within 2 percent of optimum and place in 8 to 12-inch lifts. Compact lift surface to 90 to 95 percent. 2 to 5 percent of depth + Reduced warranty + Reduced water infiltration + Reduced settlement - Possible higher lateral pressure - Slower - Need for water - Potential damage to walls D Moisture condition and place as in C. Compact lift surface to at least 95 percent 1 to 2 percent of depth + Reduced warranty + Reduced water infiltration + Lowest comparative settlement - Possible higher lateral pressure - Slower - Need for water - Potential damage to walls 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC) SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR. 7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSING 0 10 20 30 50 60 70 80 90 100 PERCENT RETAINED 40 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC) SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR. 7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSING PERCENT RETAINED 0 10 20 30 40 50 60 70 80 90 100 CLAYSTONE, SANDY, MOIST, GRAY SAND AND GRAVEL, WET, MEDIUM DENSE TO DENSE, BROWN (SP, GP, GW, SP-SM) 2. BORING ELEVATIONS ARE BASED ON TOPOGRAPHY PROVIDED BY JR ENGINEERING. THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. 4. 3. WC DD SW -200 LL PI UC SS - - - - - - - - INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER APPROXIMATE OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES UNCONFINED COMPRESSIVE STRENGTH (psf). INDICATES SOLUBLE SULFATE CONTENT (%). ADI CUSTOM, LLC 1516 WEST VINE DRIVE CTL | T PROJECT NO. FC07933-120