Subsurface Conditions Foundation Recommendations Floor Slabs Variations From Wal-Mart Requirements

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Abraham Preston
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2 TABLE OF CONTENTS SUMMARY... 1 PURPOSE AND SCOPE OF WORK... 2 PROPOSED CONSTRUCTION... 2 SITE CONDITIONS... 3 FIELD EXPLORATION... 3 SUBSURFACE CONDITIONS... 4 LABORATORY TESTING... 5 GEOTECHNICAL ENGINEERING CONSIDERATIONS... 6 FOUNDATION RECOMMENDATIONS... 7 FOUNDATION WALLS AND RETAINING STRUCTURES...10 FLOOR SLABS...11 SITE SEISMIC CRITERIA...13 EXCAVATION CONSIDERATIONS...13 SITE GRADING...14 SURFACE DRAINAGE...17 UNDERDRAIN SYSTEM...18 PAVEMENT DESIGN...19 LIMITATIONS...22 FIG. 1 - LOCATIONS OF EXPLORATORY BORINGS FIG. 1 A APPROXIMATE BEDROCK SURFACE CONTOURS FIG. 2 through 4 LOGS OF EXPLORATORY BORINGS FIG. 5 LEGEND AND NOTES FIGS. 6 through 14 - SWELL-CONSOLIDATION TEST RESULTS FIGS. 15 and 17 GRADATION TEST RESULTS FIG. 18 HVEEM STABILOMETER TEST RESULTS FIG. 19 and 20 LABORATORY RESISTIVITY RESULTS TABLE I - SUMMARY OF LABORATORY TEST RESULTS APPENDIX A DARWIN PAVEMENT THICKNESS DESIGN OUTPUTS APPENDIX B WAL-MART SPECIFIC GEOTECHNICAL ENGINEERING FACT SHEET APPENDIX C WAL-MART SPECIFIC FOUNDATION DESIGN CRITERIA APPENDIX D WAL-MART SPECIFIC FOUNDATION SUBSURFACE PREPARATION APPENDIX E BORING COORDINATES

3 SUMMARY Subsurface Conditions: Subsurface conditions at the site were explored by drilling a total of 39 exploratory borings. The exploratory borings generally encountered 1.75 to 7.25 inches of asphalt pavement at the ground surface overlying nil to 8 inches of aggregate base course material. Boring 6 encountered inches of aggregate base course below the pavement, Boring P-9 encountered 15.5 inches of aggregate base course underlying the pavement surface and Boring P-15 encountered inches of aggregate base course underlying the asphalt pavement. The pavement section was underlain by 0.5 to 6 feet of man-placed fill material. The fill material was underlain by natural lean to fat clay with clayey sand interbeds. Granular soils were encountered below the clay soils in 14 borings. Interbedded clayey sand and sandy lean clay was encountered in two of the borings. Sandstone and claystone bedrock was encountered below the natural soils or fill in 14 of the exploratory borings at depths ranging from approximately 4.5 to 27 feet. The bedrock continued to the explored depths ranging from approximately 5 to 35 feet deep where encountered. The natural soils continued to the explored depths ranging from approximately 5 to 25 feet where bedrock was not encountered. Ground water was encountered in 9 of the borings at the time of drilling at depths ranging from approximately 5 to 11 feet. Ground water was encountered in 12 of the borings when measured 6 to 17 days after drilling at depths ranging between 4 and 11 feet. Subsequent ground water level measurements were only performed in the 12 building borings as the pavement borings were backfilled and patched immediately after drilling. The stabilized ground water surface within the building footprint correlates to elevations ranging from approximately to 5352 feet. In general, the ground water surface has a slight slope down towards the north and east. Foundation Recommendations: We recommend that straight shaft drilled piers be used to support the proposed building. Straight-shaft piers drilled into the bedrock used to support the proposed structure may be designed for allowable end-bearing soil pressures of 25,000 psf with allowable side shear equal to 10% of the end bearing pressure for the portion of the pier in bedrock. Piers should also be designed for a minimum dead load pressure of (applied dead load divided by pier cross-sectional area) 15,000 psf. Floor Slabs: We believe that a slab on grade floor system may be used for the proposed building. In order to reduce potential floor slab movement, floor slabs should be placed on at least 3-feet of relatively non-expansive fill. Variations From Wal-Mart Requirements: Wal-Mart requirements indicate that groundwater levels in the exploratory borings should be measured 24 hours after drilling. The water levels in this study were measured between 6 and 17 days after drilling due to the low permeability soils. Groundwater levels take longer to stabilize in clayey (low permeable) soils. The potential vertical rise (PVR) is not included in the report. The PVR is not part of the standard of practice for this region. We reviewed several documents and standards, including the Texas DOT standard for estimating PVR values as part of this study. Based on the information reviewed, we believe that the method of determining PVR values may not be applicable to the local soils. A formal slope stability analysis was not performed as part of this study. We are not aware of significant permanent cuts or fills requiring slope stability analysis on the site. Temporary excavations on the site may reach approximately 6 feet deep; however, we anticipate these excavations to be constructed in accordance with OSHA guidelines.

4 2 PURPOSE AND SCOPE OF WORK This report presents the results of a geotechnical engineering study and pavement thickness design for the proposed Wal-Mart facility to be constructed at the southeast corner of West 58 th Avenue and Independence Street in Arvada, Colorado. The project site is shown on Fig. 1. The study was conducted in accordance with the scope of work in our Proposal No. P to PACLAND dated October 19, This report has been prepared in general accordance with Wal-Mart s Geotechnical Investigation Specifications and Report Requirements dated September 25, A Phase I environmental site assessment (ESA) is also being performed by Kumar & Associates and will be presented under separate cover. A field exploration program consisting of exploratory borings was conducted to obtain information on subsurface conditions. Samples of the soils and bedrock obtained during the field exploration were tested in the laboratory to determine their classification and engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundations, floor slabs, and site pavements. The results of the field exploration and laboratory testing are presented herein. This report has been prepared to summarize the data obtained during this study and to present our conclusions and recommendations based on the proposed construction and the subsurface conditions encountered. Design parameters and a discussion of geotechnical engineering considerations related to construction of the proposed structures are included in the report. PROPOSED CONSTRUCTION The existing retail center buildings and pavement will be demolished to make way for the new construction. Based on the site plan provided, the proposed facility to be constructed on the acre site will have a building footprint of approximately 138,319 square feet. The building will be constructed on the southern portion of the site with exterior, at-grade parking lots constructed on the west, north and east sides of the site. A truck access and loading dock area will be constructed on the south side of the building with the trucks accessing from West 57 th Avenue. Kumar & Associates, Inc.

5 3 The finish floor elevation is proposed to be feet. Proposed elevations across the remainder of the site had not been established at the time of this report. If the proposed construction varies significantly from that described above or depicted in this report, we should be notified to reevaluate the recommendations provided in this report. SITE CONDITIONS The project site is currently occupied by an existing retail shopping center. The areas surrounding the existing buildings are paved with concrete sidewalks and asphalt drive and parking lanes. The site is bounded by Independence Street to the west and East 58 th Avenue to the north. The properties immediately adjacent to the existing buildings consisted of fast food restaurants and banks. The site has an overall gentle slope down to the north towards 58 th Avenue. The maximum elevation difference across the site was on the order of about 10 to 13 feet. FIELD EXPLORATION The field exploration for the project was conducted between December 19 and 31, Thirtynine (39) exploratory borings were drilled across the site as part of this study. Twelve (12) borings were drilled near or within the proposed building footprint and 27 borings were drilled in areas of proposed pavement. The borings were made to explore the subsurface conditions at the site at the general locations shown on Fig. 1. The boring locations were paced in based on features provided on the site plan. Elevations were estimated using the existing contour plan provided. The borings were drilled to depths ranging from 5 to 35 feet. The borings were advanced into the overburden soils and bedrock with 4-inch diameter continuous flight augers. The borings were logged by a representative of Kumar & Associates, Inc. Samples of the soils and bedrock materials were taken with a 2-inch I.D. California liner sampler. The sampler was driven into the various strata with blows from a 140-pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D Penetration resistance values, when properly evaluated, indicate the relative density or consistency of the soils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figs. 2 through 4. A legend and associated explanatory notes are also provided on Fig. 5. Measurements of the water levels were made in the borings by lowering a weighted tape measure into the open hole shortly after completion of drilling and 6 to 17 days later. Kumar & Associates, Inc.

6 4 SUBSURFACE CONDITIONS The exploratory borings generally encountered 1.75 to 7.25 inches of asphalt pavement at the ground surface overlying nil to 8 inches of aggregate base course material. Boring 6 encountered inches of aggregate base course below the pavement, Boring P-9 encountered 15.5 inches of aggregate base course underlying the pavement surface and Boring P-15 encountered inches of aggregate base course underlying the asphalt pavement. The pavement section was underlain by 0.5 to 6 feet of man-placed fill material. The fill material was underlain by natural lean to fat clay with clayey sand interbeds. Granular soils were encountered below the clay soils or fill in 14 borings. Interbedded clayey sand and sandy lean clay was encountered in two of the borings. Sandstone and claystone bedrock was encountered below the natural soils in 14 of the exploratory borings at depths ranging from approximately 4.5 to 27 feet. The bedrock continued to the explored depths ranging from approximately 5 to 35 feet deep where encountered. The natural soils continued to the explored depths ranging from approximately 5 to 25 feet where bedrock was not encountered. The fill material generally appeared to consist of material similar to the natural overburden clayey soils. The lateral and vertical extents and degree of compaction of the man-placed fill material were not determined as part of this study. The clayey soils were fine to coarse grained with occasional gravel, medium stiff to very stiff in consistency (based on blow count information) and were dark gray to brown. The clayey sands were fine to coarse grained with occasional gravel, varied from loose to very stiff and were brown. Layers of clayey gravel encountered in Borings 4, 7 and 8 were fine to coarse grained, medium dense to dense and brown. The sandstone bedrock was fine to medium grained, firm to very hard, blue to gray to brown and had nil to weak cementation. The claystone bedrock was firm to very hard and brown. The samples varied from moist to wet. Ground water was encountered in 9 of the borings at the time of drilling at depths ranging from approximately 5 to 11 feet. Ground water was encountered in 12 of the borings when measured 6 to 17 days after drilling at depths ranging between 4 and 11 feet. Subsequent ground water level measurements were performed in the 12 building borings. The pavement borings were backfilled and patched immediately after drilling. The stabilized ground water surface within the building footprint correlates to elevations ranging from approximately to 5352 feet. In general, the ground water surface has a slight slope down towards the north and east. Bedrock Topography: The competent bedrock surface ranged in elevation from 5326 to feet. The bedrock surface appeared to slope moderately to steeply down towards the west with Kumar & Associates, Inc.

7 5 a gentle trend down to the north. An approximate bedrock surface contour map is provided on Fig. 1A. LABORATORY TESTING The samples obtained from the exploratory borings were visually classified in the laboratory by the project engineer and samples were selected for laboratory testing. Laboratory testing included index property tests, such as moisture content (ASTM D 2216), dry unit weight, percent passing the No. 200 sieve (ASTM D 1140), liquid and plastic limits (ASTM D 4318), and percent water soluble sulfates. Soil corrosivity testing consisting of electrical resistivity, ph, and chloride content was also performed on selected samples. Swell-consolidation tests (ASTM D 4546, Method B) were conducted on samples of the soil and bedrock to determine the compressibility or swell characteristics under loading and when submerged in water. Results of the laboratory testing program are shown adjacent to the boring logs, Figs. 2 through 4, plotted graphically on Figs. 6 through 20 and are summarized in the attached Summary of Laboratory Test Results, Table I. Swell consolidation testing, presented on Figs. 6 through 14, indicate samples of the clayey overburden soils generally exhibit a low consolidation potential to low swell potential when tested under a constant surcharge pressure of 200 psf or 1,000 psf. The claystone bedrock exhibited moderate to high swell potential when wetted under similar loading conditions. Water Soluble Sulfates: The concentration of water soluble sulfates measured in samples obtained from the exploratory borings ranged from less than 0.02% to 1.58%. This concentration of water soluble sulfates represents a Class 0 through Class 2 level of severity for exposure in accordance with the guidelines presented in ACI 201. The guidelines have severity levels for potential exposure of Class 0 through Class 3. We recommend that all concrete on the site meet the criteria presented in ACI 201 for Class 2 sulfate resistance. Organics Content: Some of the borings encountered dark brown to black clayey material near the contact of the man-placed fill and the natural soils. The darker material also had indications of organics in the form of the root remnants. We were not able determine the extents of the darker soils. We performed a single organics content test on a sample obtained from the borings. The test results indicate an organics content of 1.7%. Kumar & Associates, Inc.

8 6 The contractor should be made aware that these materials may be encountered during the subexcavation process. These materials will likely be very wet, mucky and generally soft. Any soft or overly moist materials encountered in excavations should be removed prior to fill placement. Mucky material should not be considered acceptable for reuse elsewhere on the site and should be removed from the site. Mucky material should be classified as overly saturated material having an organics content in excess of 5% by dry weight using the ignition method. Materials that are overly saturated or wet but have little to no organics should not be considered muck and may be reused elsewhere on the site with proper conditioning. We believe that there will little to no materials on the site the will classify as mucky material. Buried Metal Corrosion: Laboratory resistivity testing was performed on selected samples from the exploratory borings. The testing was performed to evaluate the resistivity of the overburden soils at the in-situ moisture content as well as the minimum resistivity at elevated moisture contents. The test results from samples of the overburden clayey soils indicate a minimum resistivity ranging from 229 to 280 ohm-centimeters and resistivity values ranging from 380 to 950 ohm-cm at the in-situ moisture contents. The test results indicate that the on-site soils are potentially corrosive and require some form of protection. The test results should be reviewed by a qualified corrosion engineer. GEOTECHNICAL ENGINEERING CONSIDERATIONS Our knowledge of the general area surrounding the site along with the subsurface conditions encountered during drilling prompted us to perform a limited amount of background research on this specific site. USGS topographic maps from 1947 through 1994 that include the site were reviewed along with several aerial photographs of the area from about the same time period. We also interviewed select persons that have current and past working knowledge of the area. In general, up until about the early 1960 s the natural Van Bibber Creek drainage crossed the northern half of the site. The early 1960 s, we saw this site developed with many of the buildings that exist today and the Van Bibber Creek was piped underground in about the same alignment as the natural channel. The Van Bibber Creek flows were largely diverted in the mid 2000 s to flow in an underground channel to the north of 58 th Avenue. We have been informed that the buried channel on this site was not abandoned and that it still receives incidental flows from the creek as well as flows from some storm drainage systems in the area. The buried channel on this site did not appear during our utility locates and we are not aware of the exact alignment on the site. We believe that the alignment is outside of the proposed Wal-Mart building footprint, but we recommend that the buried channel be located prior to construction. Kumar & Associates, Inc.

9 7 We believe that ground water is shallow in the area as a result of the historic flows in the Van Bibber Creek drainage. Other documentation of ground water monitoring wells near the site indicated that the overall ground water level drops down to the north and east in the general direction of Ralston Creek, which is north and east of the site approximately 1 to 2 blocks. We also believe that the Van Bibber Creek drainage has historically varied in location and at some point in time was likely farther to the south near the proposed Wal-Mart building footprint. This would explain the significant variation in depth to bedrock encountered in the borings drilled within the proposed building footprint. FOUNDATION RECOMMENDATIONS Based on the data obtained during the field and laboratory studies and our experience with similar sites, we recommend straight-shaft piers drilled into the bedrock be used to support the proposed structure. We considered the use of shallow spread footings to support the proposed structure; however, we discounted this type of foundation as an economical alternative due to the relatively soft soil and shallow ground water conditions. The design and construction criteria presented below should be observed for a straight-shaft pier foundation system. The construction details should be considered when preparing project documents. 1. Piers should be designed for an allowable end bearing pressure of 25,000 psf and a skin friction of 2,500 psf for the portion of the pier in bedrock. Uplift due to structural loadings on the piers can be resisted by using 75% of the allowable skin friction value plus an allowance for pier weight. 2. Piers should also be designed for a minimum dead load pressure of 15,000 psf based on pier end area only. Application of dead load pressure is the most effective way to resist foundation movement due to swelling soils. However, if the minimum dead load requirement cannot be achieved and the piers are spaced as far apart as practical, the pier length should be extended beyond the minimum bedrock penetration and minimum length to mitigate the dead load deficit. This can be accomplished by assuming one-half of the skin friction given above acts in the direction to resist uplift caused by swelling rock near the top of the pier. The owner should be aware of an increased potential for foundation movement if the recommended minimum dead load pressure is not met. Kumar & Associates, Inc.

10 8 3. Piers should penetrate at least three pier diameters into the bedrock. A minimum penetration of 8 feet into the bedrock and a minimum pier length of 20 feet are recommended. Both criteria for minimum pier length and minimum bedrock penetration should be met. 4. Piers should be designed to resist lateral loads using a modulus of horizontal subgrade reaction in the clayey overburden soils of 20 tcf and a modulus of horizontal subgrade reaction of 200 tcf in the bedrock. Resistance to lateral loads should be neglected in the uppermost 5 feet of the pier. The modulus value given is for a long one-foot wide pier and must be corrected for pier size. If a computerized approach to the analysis is used, such as LPILE, we should be contacted to provide geotechnical design criteria for the lateral load analysis. 4. Piers should be reinforced their full length with at least one No. 5 reinforcing rod for each 18 inches of pier perimeter to resist tension created by the swelling overburden materials. 6. A 4-inch void should be provided beneath the grade beams to concentrate pier loadings and to separate the expansive soil from the grade beams. Absence of a void space will result in a reduction in dead load pressure which could result in upward movement of the foundation system. A void should also be provided beneath necessary pier caps. 7. Closely spaced piers may require appropriate reductions of the lateral and axial capacities. Reduction in lateral load capacity may be avoided by spacing the piers at least 6 pier diameters (center to center) in the direction parallel to pier loading, and 2.5 diameters in the direction perpendicular to loading. For axial loading, the piers should be spaced a minimum of 3 diameters center to center. More closely spaced piers should be studied on an individual basis to determine the appropriate reduction in axial and lateral load design parameters. 8. The pier length-to-diameter ratio should not exceed Concrete used in the piers should be a fluid mix with sufficient slump so it will fill the void between reinforcing steel and the pier hole. We recommend a concrete slump in the range of 5 to 8 inches be used. Kumar & Associates, Inc.

11 9 The specifications should allow the geotechnical engineer to eliminate the requirements for pier roughening or shear rings if it appears their installation is not beneficial. This could occur if a rough surface is provided by the drilling process or if the presence of water and/or weakly cemented materials results in a degradation of the pier hole during the roughening procedure or installation of shear rings. 10. Based on the results of our field exploration, laboratory testing, and our experience with similar, properly constructed drilled pier foundations, we estimate pier settlement will be low. Generally, we estimate the settlement of a pier will be less than 1-inch when designed according to the criteria presented herein. The settlement of closely spaced piers will be larger and should be studied on an individual basis. 11. Pier holes should be properly cleaned prior to the placement of concrete. 12. The presence of water and/or occasional granular soils in the exploratory borings indicates temporary casing and/or dewatering equipment will likely be required. In no case should concrete be placed in more than 3 inches of water unless the tremie method is used. If water cannot be removed or prevented with the use of temporary casing and/or dewatering equipment prior to placement of concrete, the tremie method should be used after the hole has been cleaned. 13. Casing procedures should be evaluated by the geotechnical engineer on piers which will be subjected to lateral loads. Oversizing the portion of the hole in the overburden to allow casing insertion can reduce the lateral pier capacity, particularly if the hole is processed with a dense, viscous mixture of water and soil. Depending on loading conditions and construction practices, densification of the materials around the pier top is sometimes required after construction. 14. When water and/or a drilling slurry is present outside the casing, care should be taken that concrete of sufficiently high slump is placed to a sufficiently high elevation inside the casing to prevent intrusion of the water and/or slurry into the concrete when the casing is withdrawn. 15. The drilled shaft contractor should mobilize equipment of sufficient size and operating condition to achieve the required bedrock penetration. Kumar & Associates, Inc.

12 Care should be taken that the pier shafts are not oversized at the top. Mushroomed pier tops can reduce the effective dead load pressure on the piers. 17. Concrete should be placed in piers the same day they are drilled. The presence of water or caving soils may require that concrete be placed immediately after the pier hole is completed. Failure to place concrete the day of drilling will normally result in a requirement for additional bedrock penetration. 18. The field exploration encountered several areas of weak to non-cemented sandstone below the bedrock surface. These materials may cave during the drilling process and casing in the bedrock may be required to complete the piers. Zones of caving material should not be included in the required length of penetration and the pier length should be increased an amount equal to the length of caving material. In general, no allowance for skin friction is given in cased portions of the bedrock. However, if a significant quantity of the bedrock is being cased, we can evaluate the possibility of reduced skin friction values in the cased bedrock. 19. Difficulty may be encountered in establishing a casing seat in the sandstone to achieve a positive cutoff of ground-water seepage into the hole. Additional bedrock penetration may be required to compensate for the side shear lost due to disturbance caused by installation of the casing. Skin friction should be neglected in the cased portion of the hole. The amount of additional penetration should be determined in the field at the time of construction. The contract documents should advise potential drilled shaft contractors of these subsurface conditions. In addition, careful consideration should be given to preparing bid items to avoid high costs for potential overruns. 20. A representative of the geotechnical engineer should observe pier drilling operations on a full-time basis to assist in identification of adequate bedrock strata and monitor pier construction procedures. FOUNDATION WALLS AND RETAINING STRUCTURES Structures which are laterally supported and can be expected to undergo only a moderate amount of deflection should be designed for an at-rest lateral earth pressure computed on the basis of an equivalent fluid unit weight of 65 pcf for backfill consisting of the on-site fine-grained soils and 55 pcf for backfill consisting of imported granular materials meeting CDOT Class I Structure Backfill criteria. Kumar & Associates, Inc.

13 11 Cantilevered retaining structures which can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of 45 pcf for backfill consisting of the on-site fine-grained soils and 36 pcf for backfill consisting of imported granular materials meeting CDOT Class I Structure Backfill criteria. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent buildings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. Compacted fill placed against the sides of the below grade structure to resist lateral loads should be a non-expansive, material. Fill should be placed and compacted to at least 95% of the standard Proctor maximum dry density at a moisture content as presented in the Site Grading section of this report. Care should be taken not to over-compact the backfill around below- grade structures since this could cause excessive lateral pressure on the walls. FLOOR SLABS Floor slabs present a problem where expansive soils and fill materials are present near floor slab elevation because sufficient dead load cannot be imposed on them to resist the uplift pressure generated when the materials are wetted and expand. Based on the low swelling characteristics of the materials encountered, we believe slab-on-ground construction may be used, provided the risk of distress resulting from slab movement is accepted by the owner. As indicated above, there is varying depths of man-placed fill across the site. Placing floor slabs on fills of unknown compactive history creates the potential risk for movements. These movements tend to be settlements of the floor slab; however, heaving movements may be possible depending on the properties of the fill materials. Based on this information, we have recommended that the floor slabs be underlain by a minimum of 3 feet of properly compacted structural fill material. This depth of subexcavation in the floor slab area will likely not remove all of the existing fill materials, but will provide a uniform depth of properly compacted fill material to help mitigate the potential for differential movements. The subexcavation and replacement will Kumar & Associates, Inc.

14 12 provide a subgrade surface capable of providing a vertical modulus of subgrade reaction of 150 psi/inch. The following measures should be taken to reduce damage which could result from movement should the underslab materials be subjected to moisture changes. 1. Floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. 2. Interior non-bearing partitions resting on floor slabs should be provided with slip joints so that, if the slabs move, the movement cannot be transmitted to the upper structure. This detail is also important for wallboards, stairways and door frames. Slip joints which will allow at least 2 inches of vertical movement are recommended. If wood or metal stud partition walls are used, the slip joints should preferably be placed at the bottoms of the walls so differential slab movement won t damage the partition wall. If slab bearing masonry block partitions are constructed, the slip joints will have to be placed at the tops of the walls. If slip joints are provided at the tops of walls and the floors move, it is likely the partition walls will show signs of distress, such as cracking. An alternative, if masonry block walls or other walls without slip joints at the bottoms are required, is to found them on grade beams and piers and to construct the slabs independently of the foundation. If slab bearing partition walls are required, distress may be reduced by connecting the partition walls to the exterior walls using slip channels. Floor slabs should not extend beneath exterior doors or over foundation grade beams, unless saw cut at the beam after construction. 3. Floor slab control joints should be used to reduce damage due to shrinkage cracking. Joint spacing is dependent on slab thickness, concrete aggregate size, and slump, and should be consistent with recognized guidelines such as those of the Portland Cement Association (PCA) or American Concrete Institute (ACI). We suggest joints be provided on the order of 12 to 15 feet apart in both directions. The requirements for slab reinforcement should be established by the designer based on experience and the intended slab use. 4. If moisture-sensitive floor coverings will be used, mitigation of moisture penetration into the slabs, such as by use of a vapor barrier, may be required. If an impervious vapor Kumar & Associates, Inc.

15 13 barrier membrane is used, special precautions will be required to prevent differential curing problems which could cause the slabs to warp. ACI 301.1R addresses this topic. 5. All fill materials for support of floor slabs should be placed and compacted according to the criteria presented in Site Grading. The suitability of the on-site soils for use as underslab fill is also discussed in Site Grading. 6. The geotechnical engineer should evaluate the suitability of proposed fill materials prior to use. In fill areas, natural soils should be scarified to a depth of 8 inches, adjusted to a moisture content near optimum, and recompacted to provide a uniform base for fill placement. 7. Some of the natural soil and bedrock encountered during this study may be suitable for use in compacted fills beneath floor slabs. 8. All plumbing lines should be tested before operation. Where plumbing lines enter through the floor, a positive bond break should be provided. Flexible connections should be provided for slab-bearing mechanical equipment. SITE SEISMIC CRITERIA The soil profile is expected to consist of compacted moisture conditioned fill and/or natural clay overlying claystone bedrock. The overburden materials will generally classify as International Building Code (IBC) Site Class D. The underlying bedrock generally classifies as IBC Site Class B or C. Based on our experience with similar subsurface profiles along the Front Range area, we recommend a design soil profile of IBC Site Class C. Based on the subsurface profile, and site seismicity, liquefaction is not a design consideration. EXCAVATION CONSIDERATIONS We assume that the site excavations will be constructed by generally over-excavating the side slopes to a stable configuration where enough space is available. All excavations should be constructed in accordance with OSHA requirements, as well as state, local and other applicable requirements. The claystone bedrock generally classify as OSHA Type A or B (depending upon the fracturing), and the natural overburden clay soils generally classify as OSHA Type B soils. The existing fill and natural granular soils encountered classify as OSHA Type C soil. Kumar & Associates, Inc.

16 14 In our opinion, excavation of the on-site materials should be possible with conventional excavation equipment. SITE GRADING Cut and Fill Slopes: We anticipate cut and fill slopes on the project as high as about 6 feet. Due to the relative flatness of ground surface slopes, no signs of major slope instability were noted in the nearby existing slopes during our field investigation. Major stability problems are not anticipated if site grading is carefully planned and cuts and fills do not exceed approximately 20 feet in height. Permanent unretained cuts in the overburden soils, above the ground water level and less than 15 feet in height may be constructed at 3 horizontal to 1 vertical. The risk of slope instability will be significantly increased if seepage is encountered in cuts. Based on the planned grading and ground water levels measured in the borings, we anticipate minor seepages will be encountered near the southern building line. If significant seepage flows are encountered, a stability investigation should be conducted to determine if the seepage will adversely affect the cut. Fills up to 15 feet in height can be constructed if the fill slopes do not exceed 3 horizontal to 1 vertical (3:1) and the fills are properly compacted and drained. The ground surface underlying all fills should be carefully prepared by removing all organic matter, scarification to a depth of 8 inches and compacting the surface to provide a uniform base for fill placement. Fill placed on slopes exceeding 4:1 should be benched into the slope. Good surface drainage should be provided around all permanent cuts and fills to direct surface runoff away from the slope faces. Fill slopes, cut slopes and other stripped areas should be protected against erosion by revegetation or other methods. No formal stability analyses were performed to evaluate the slopes recommended above. Published literature and our experience with similar cuts and fills indicate the recommended slopes should have adequate factors of safety. If a detailed stability analysis is required, we should be notified. Site Materials Recycling: Given the size of the project and the presence of the existing structures and pavement, we anticipate that some amount of recycling will occur. Recycled concrete materials may be used as structural fill or aggregate base course across the site. We Kumar & Associates, Inc.

17 15 recommend that recycled asphalt be blended with recycled concrete or a virgin crushed aggregate at a rate of at least 1 part virgin aggregate or recycled concrete to 1 part recycled asphalt. Recycled concrete and asphalt should be crushed to a consistency meeting CDOT Class 5 or 6 gradation or gradation which meets our approval. Recycled material used as structural fill on the site should be crushed to meet CDOT Class 1 Structure Backfill criteria. Material used as base course should meet CDOT Class 6 Base Course criteria. Fill Considerations: The on-site clay soils are suitable for reuse as fill under slabs and pavement subgrades. Fill placed for slab support should be placed with careful moisture control as discussed later in this section. Uniform moisture conditions in fill material obtained from onsite sources and placed for slab support will be important in reducing the swell potential of the compacted fill. In order to obtain uniform moisture in the fill, a moistening and mixing program will need to be developed during the initial stages of site grading. The existing moisture content of the some of the clayey soils appears to be well above the assumed optimum moisture content and some form of drying may be required prior to placement as embankment material. Recommendations are presented in the report regarding material properties, degree of compaction and moisture control. We recommend the on-site materials used as fill be mixed thoroughly with construction equipment, such as a mixer/reclaimer to break up clumps of soil and add water to obtain a homogeneous mixture. The use of a disc may be considered, but the effectiveness of this mixing process should be evaluated at the time of fill placement. Material Specifications: The following material specifications are presented for fills on the project site. The geotechnical engineer should evaluate the suitability of all proposed fill materials to be used on the site prior to placement. Fill Beneath Buildings and Parking Lots: The on-site overburden soils, exclusive of claystone bedrock, are suitable for re-use as structural fill below floor slabs and pavement structures. Imported structural fill, if required, for use under slabs should meet the following criteria: Percent Passing No. 200 Sieve Less than 60% Liquid Limit Less than 35 Plasticity Index Less than 20 Swell Potential < 2% at 200 psf surcharge at optimum moisture content Kumar & Associates, Inc.

18 16 Foundation Wall Backfill (Interior and Exterior Backfill): On-site soils or approved imported soils meeting the criteria presented above may be used for foundation wall backfill. Utility Trench Backfill: Material excavated from the utility trenches may be used for backfill provided it does not contain unsuitable material or particles larger than 4 inches. Other Fill Material: All fill material should be a non-expansive soil free of vegetation, brush, sod and other deleterious substances and should not contain rocks or particles having a diameter of more than 4 inches. If grading is performed during times of freezing weather, the fill should not contain frozen materials and if the subgrade is allowed to freeze, all frozen material should be removed prior to additional fill placement or footing, slab or pavement construction. Aggregate Base Course: Aggregate base course placed in conjunction with pavements should consist of material meeting the requirements of CDOT Class 5 or 6 base course. Compaction Specifications: Compaction of all on-site soil fill materials placed under building foundations and floor slabs should be placed at moisture contents between 0 and +3% of the optimum moisture content (ASTM D 698) for fine-grained fill. Any imported granular fill material should be placed within 2% of the optimum moisture content and cohesive fill placed within pavement or non-building areas should be placed within -1 to +3% of the optimum moisture content. Recommended compaction specifications for this project, based on percentage of maximum density are presented in the following table: Area Beneath Floor Slabs and Parking Lots Percentage of Standard Proctor Maximum Dry Density (ASTM D 698/ AASHTO T-99) Percentage of Modified Proctor Maximum Dry Density (ASTM D 1557, AASHTO T-180) 98 N/A Utility Trenches 98 N/A Parking Lots/Drives 98 N/A Aggregate Base Course N/A 95 Dewatering: Site grading required to prepare the structure foundations may require grading consisting of temporary cuts up to about 10 feet. Some excavations are expected to be Kumar & Associates, Inc.

19 17 impacted by the presence of ground water. Prior to excavation, we recommend a dewatering plan be developed and implemented by the contractor. An open cut interceptor drain outside the structures may be considered, but may require frequent maintenance during construction. Excavation below the ground water level should be avoided as practical to avoid caving of the side slopes and disturbance of the bearing surface may occur. We suggest the ground water level be lowered to at least 2 feet below the base of the required excavation prior to achieving the final grade. The fine grained soils are expected to be unstable under trafficking by construction equipment. It is likely that any wet clayey material in this area will require removal and replacement with a compacted granular fill prior to slab construction. We assume that the excavations will be constructed by overexcavating the slopes to a stable configuration rather than using a temporary retaining system. We recommend temporary excavation slopes in the soils be constructed no steeper than 2 horizontal to 1 vertical. Seepage of ground water in cut slopes may require that the slopes be flattened for safety purposes. Temporary shoring will most likely be required for excavations constructed below the ground water level. Pumps located within the excavation may still be required to provide sufficiently dewatered working conditions. SURFACE DRAINAGE Proper surface drainage is very important for acceptable performance of the structures during construction and after the construction has been completed. Drainage recommendations provided by local, state and national entities should be followed based on the intended use of the facility. The following recommendations should be used as guidelines and changes should be made only after consultation with the geotechnical engineer. 1. Excessive wetting or drying of the foundation and slab subgrade(s) should be avoided during construction. 2. Exterior backfill should be adjusted to near optimum moisture content (generally ±2% of optimum unless indicated otherwise in the report) and compacted to at least 95% of the ASTM D 698 (standard Proctor) maximum dry density. Kumar & Associates, Inc.

20 18 3. Care should be taken when compacting around the foundation walls and underground structures to avoid damage to the structure. Hand compaction procedures, if necessary, should be used to prevent lateral pressures from exceeding the design values. 4. The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas. Site drainage beyond the 10-foot zone should be designed to promote runoff and reduce infiltration. A minimum slope of 3 inches in the first 10 feet is recommended in the paved areas. These slopes may be changed as required for handicap access points in accordance with the Americans with Disabilities Act. 5. The upper 1 to 2 feet of the backfill should be relatively impervious material compacted as above to limit infiltration of surface runoff. 6. Ponding of water should not be allowed in backfill material or in a zone within 10 feet of the foundation walls whichever is greater. 7. Roof downspouts and drains should discharge well beyond the limits of all backfill. 8. Excessive landscape irrigation should be avoided within 10 feet of the foundation walls. As discussed under Floor Slabs, if slab-on-grade floors are used, the risk could be significantly reduced by eliminating landscape irrigation within about 15 feet of buildings and limiting irrigation elsewhere on side, provided good surface drainage is provided. 9. Plastic membranes should not be used to cover the ground surface adjacent to foundation walls. UNDERDRAIN SYSTEM The structures should be protected by an underdrain system. The drain system should be constructed with the high point at least 6 inches below the bottom of the floor slab sloping at least ½ percent to an outlet or sump. Lateral drains should be installed below the floor slab spaced on maximum 50-foot centers. The drain system should consist of 4-inch diameter rigid pipes. The pipes should be covered with at least 6 inches of CDOT #67 coarse aggregate which in turn are wrapped with filter fabric. Kumar & Associates, Inc.

21 19 The underdrain system should be sloped to a sump or multiple sumps where water can be removed by pumping or gravity drainage. Standby pump capacity should be provided in the event of pump failure. We also believe an overdesigned pump capacity is desirable in the event ground water conditions change. PAVEMENT DESIGN A pavement section is a layered system designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and traffic loadings. Soils are represented for pavement design purposes by means of a soil support value for flexible pavements and a modulus of subgrade reaction for rigid pavements. Both values are empirically related to strength. Subgrade Materials: Based on the results of the field and laboratory studies, the majority of the subgrade materials at the site classify between A-2-4 and A-7-6 with group indices between 0 and 27 in accordance with the American Association of State Highway and Transportation Officials (AASHTO) classification. We performed an Hveem R-value test on a composite sample of the subgrade material obtained from the borings. The Hveem test results, presented on Fig. 23, indicate that the material has an R-value of less than 5. In accordance with Colorado Department of Transportation (CDOT) correlation procedures, an R-value of 5 correlates to a subgrade resilient modulus (M R ) of 3,025 psi. We used this value in the pavement thickness design. A horizontal subgrade reaction of 25 pci was selected for rigid pavements. Design Traffic: The Wal-Mart site development standards identify a Standard Duty and a Heavy Duty pavement thickness requirement for projects constructed under their jurisdiction. The design standards indicate that a Standard Duty pavement section is to be designed using an 18-kip equivalent single axle loading (ESAL) value of 109,500. Heavy Duty pavement sections are to be designed using an ESAL of 335,800. The design standards indicate that full depth asphalt pavement is not allowed and that all pavement sections must consist of a base course layer and an asphalt or concrete layer. If estimated daily traffic volumes for the facility are known to be different from those assumed, we should be provided with this information in order to reevaluate the pavement sections provided below. Kumar & Associates, Inc.

22 20 Pavement Design: The following table presents the minimum pavement thickness recommendations for this facility. LOCATION Asphalt Over Base Course (inches) Concrete Thickness (inches) Standard Duty 5 over 9 6 Heavy Duty 5½ over 11 7 The asphalt thicknesses above should be placed in a minimum of two lifts. All paving lift thicknesses should be in accordance with current CDOT criteria. Truck loading dock areas and other areas where truck turning movements are concentrated should be paved with 7 inches of Portland cement concrete. The concrete pavement should contain sawed or formed joints to ¼ of the depth of the slab at a maximum distance of 12 to 15 feet on center. Concrete pavements may be a suitable alternative for parking lots, fuel center and delivery areas. The above Portland cement concrete pavement thicknesses are presented as un-reinforced slabs. Based on projects with similar heavy vehicular loading, we recommend that dowels be provided at transverse joints within the slabs located in the travel lanes of heavily loaded vehicles. Additionally, curbs and/or pans should be tied to the slabs. The dowels and tie bars will help minimize the risk for differential movements between slabs to assist in more uniformly transferring axle loads to the subgrade. The Colorado Department of Transportation (CDOT) provides some guidance on dowel and tie bar placement in the current Standard Specifications for Road and Bridge Construction as well as in the current Standard Plans: M&S Standards. It is critical to the performance of the concrete pavement that the joints are properly sealed and maintained to minimize the infiltration of surface water, especially if dowels and tie bars are not installed. The pavement thicknesses were calculated using design parameters as listed above input into the DARWin software program. Results of the output of the program are presented in the Appendix of this report. Subgrade Preparation: Prior to placing the pavement section, the entire subgrade area should be subexcavated, moisture conditioned and properly compacted to a depth of at least 2 feet below the proposed pavement subgrade elevation. The pavement subgrade should be proofrolled with a heavily loaded pneumatic-tired vehicle. Pavement design procedures assume a stable subgrade. Areas which deform excessively under heavy wheel loads are not stable Kumar & Associates, Inc.

23 21 and should be removed and replaced to achieve a stable subgrade prior to paving. On-site materials meeting Structural Fill criteria are suitable for use in replacing soft areas. Subgrade Stabilization: If soft areas are encountered during subgrade subexcavation and placement, stabilization should be performed prior to placing additional fill or the pavement section. Stabilization may be achieved by excavating and replacing the soft soils to a maximum depth of 3 feet. An alternative to replacing the soft soils would be to subexcavate 1 to 2 feet of the soft materials and placing a biaxial geogrid such as a Tensar Type 2 Geogrid in the base of the excavation. The geogrid should be covered with a minimum of 12 inches of crushed aggregate base course. Soft areas that are relatively large or that occur within Heavy Duty pavement areas may require an additional thickness of base course material. Chemical stabilization is also a subgrade stabilization alternative. Chemical stabilization, if necessary, should consist of mixing cement, fly ash, or lime (if the soils are clayey), into the upper 12 inches of the pavement subgrade. Unlike a designed stabilized subbase layer, which requires mix design and careful control of strength, the performance requirements of the stabilized layer is only to provide a sufficiently stable subgrade to perform acceptably under proofrolling and paving. Therefore, the specification acceptance criteria should be based on proofrolling. Stabilization should consist of mixing the stabilizing agent thoroughly into the upper 12 inches of the subgrade using a stabilizer mixer type of equipment and then to compact the mixture with a large vibratory sheepsfoot type compactor. Adequate moisture should be added to the mixture, as necessary, to allow the required chemical reaction to occur. The final surface should be reasonably hard; treated soil will typically be expected to achieve an unconfined compressive strength on the order of 150 to 200 psi or more. All subgrade fill materials should be compacted according to the criteria presented in the Site Grading section of this report. In fill areas, imported fill should have classification properties similar to the on-site soils, with M R values equivalent to or higher than the values used for design. Drainage: The collection and diversion of surface drainage away from paved areas is extremely important to the satisfactory performance of pavement. Drainage design should provide for the removal of water from paved areas and prevent the wetting of the subgrade soils. DESIGN AND CONSTRUCTION SUPPORT SERVICES Kumar & Associates, Inc. should be retained to review the project plans and specifications for conformance with the recommendations provided in our report. We are also available to assist Kumar & Associates, Inc.

24 22 the design team in preparing specifications for geotechnical aspects of the project, and performing additional studies if necessary to accommodate possible changes in the proposed construction. We recommend that Kumar & Associates, Inc. be retained to provide observation and testing services to document that the intent of this report and the requirements of the plans and specifications are being followed during construction, and to identify possible variations in subsurface conditions from those encountered in this study so that we can re-evaluate our recommendations, if needed. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering practices in this area for exclusive use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory borings at the locations indicated on Fig. 1, and the proposed type of construction. This report may not reflect subsurface variations that occur between the exploratory borings, and the nature and extent of variations across the site may not become evident until site grading and excavations are performed. If during construction, fill, soil, rock or water conditions appear to be different from those described herein, Kumar & Associates, Inc. should be advised at once so that a re-evaluation of the recommendations presented in this report can be made. Kumar & Associates, Inc. is not responsible for liability associated with interpretation of subsurface data by others. JLB/jw cc: book, file Kumar & Associates, Inc.