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HomeMy WebLinkAboutRIGDEN FARM, 8TH FILING, LOT 5, GREASE MONKEY/CARWASH - PDP - 56-98AI - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGeotechnical Engineering Report Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 lferratan This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. 18 Geotechnical Engineering Report Terracon ' Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 imported material approved by the geotechnical engineer. The pipe backfill should be compacted to a minimum of 95 percent of Standard Proctor Density ASTM D698. • Surface Drainage '. Positive drainage should be provided during construction and maintained throughout the life of the proposed project. Infiltration of water into utility or foundation excavations must be prevented during construction. Planters and other surface features, which could retain water in areas adjacent to the building or pavements, should be sealed or eliminated. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of approximately 5 percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of all construction debris to reduce the possibility of moisture infiltration. Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when the ground surface beneath such features is not protected by exterior slabs or paving. Sprinkler systems should not be installed within 10-feet of foundation walls. ' Landscaped irrigation adjacent to the foundation system should be minimized or eliminated. GENERAL COMMENTS Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide testing and observation during excavation, grading, foundation and construction phases of the project. IThe analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of weather. The nature and extent of such variations may not ' become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. 17 fl r I I 1' 1' i r I Geotechnical Engineering Report Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 lrerramn encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions. As a safety measure, it is recommended that all vehicles and soil piles be kept to a minimum lateral distance from the crest of the slope equal to no less than the slope height. The exposed slope face should be protected against the elements. Additional Design and Construction Considerations Exterior Slab Design and Construction Compacted subgrade or existing clay soils may expand with increasing moisture content; therefore, exterior concrete grade slabs may heave, resulting in cracking or vertical offsets. The potential for damage would be greatest where exterior slabs are constructed adjacent to the building or other structural elements. To reduce the potential for damage, we recommend: • exterior slabs be supported on fill with no, or very low expansion potential • strict moisture -density control during placement of subgrade fills • placement of effective control joints on relatively close centers and isolation joints between slabs and other structural elements • provision for adequate drainage in areas adjoining the slabs • use of designs which allow vertical movement between the exterior slabs and adjoining structural elements In those locations where movement of exterior slabs cannot be tolerated or must be reduced, consideration should be given to: • Constructing slabs with a stem or key -edge, a minimum of 6 inches in width and at least 12 inches below grade; • supporting keys or stems on drilled piers; or • providing structural exterior slabs supported on foundations similar to the building. Underground Utility Systems All piping should be adequately bedded for proper load distribution. It is suggested that clean, graded gravel compacted to 75 percent of Relative Density ASTM D4253 be used as bedding. Utility trenches should be excavated on safe and stable slopes in accordance with OSHA regulations as discussed above. Backfill should consist of the on -site soils or 16 I. Geotechnical Engineering Report lferracan Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 Fill Materials and Placement Approved imported materials may be used as fill material and are suitable for use as compacted fill beneath interior or exterior floor slabs. ' Imported soils (if required) should conform to the following: Percent finer by weight Gradation (ASTM C136) 3"......................................................................................................... 100 No. 4 Sieve..................................................................................... 50-100 No. 200 Sieve.............................................................................. 35 (max) • Liquid Limit.................................................................................. 30 (max) �. Plasticity Index............................................................................. 15 (max) • Group Index................................................................................. 10 (max) Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. It is recommended all fill material to placed on the site be compacted to at least 95 percent of Standard Proctor Density ASTM D698. ' On -site clay soils should be compacted within a moisture content range of 1 percent below, to 3 percent above optimum. Imported granular soils should be compacted within a moisture range of 3 percent below to 3 percent above optimum unless modified by the �s project geotechnical engineer. Excavation and Trench Construction Excavations into the on -site soils will encounter a variety of conditions. Caving soils and groundwater may also be encountered. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottom. All excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. The soils to be penetrated by the proposed excavations may vary significantly across the site. The preliminary soil classifications are based solely on the materials encountered in widely spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are 1 15 Geotechnical Engineering Report lferracon Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 • Site Preparation Strip and remove any existing fill or debris or other deleterious materials from proposed building and pavement areas. All exposed surfaces should be free of mounds and ' depressions that could prevent uniform compaction. After the required overexcavation is performed, the site should be initially graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed building addition. Exposed areas, which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 12-inches, conditioned to near optimum moisture content, and compacted. It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Based upon the subsurface conditions determined from the geotechnical exploration, the majority of the underlying subgrade soils exposed during construction are anticipated to be relatively stable after removing topsoil material from building and pavement areas. Soft compressible and/or unstable areas may be encountered during construction especially in areas of subgrade that contains high moisture contents, or in close proximity to groundwater. The stability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unstable conditions develop, workability may be improved by scarifying and drying. Overexcavation of wet zones and replacement with granular materials may be necessary. Use of lime, fly ash, kiln dust, cement or geotextiles could also be considered as a stabilization technique. Laboratory evaluation is recommended to determine the effect of chemical stabilization on subgrade soils prior to construction. Lightweight excavation equipment may be required to reduce subgrade pumping. • Subgrade Preparation ' Subgrade soils beneath interior and exterior slabs, and beneath pavements should be scarified; moisture conditioned and compacted to a minimum depth of 12-inches below proposed controlled fill material. The moisture content and compaction of subgrade soils should be maintained until slab or pavement construction. 1 14 I Geotechnical Engineering Report 1rerracan ' Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 • Placing compacted, low permeability backfill against the exterior side of curb and gutter; ' and, • Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of base course materials. Preventive maintenance should be planned and provided for through an on -going pavement management program. Preventive maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment. Preventive maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventive maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Prior to implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventive maintenance. Site grading is generally accomplished early in the construction phase. However as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or rainfall. As a result, the pavement subgrade may not be suitable for pavement construction and corrective action will be required. The subgrade should be carefully evaluated at the time of pavement construction for signs of disturbance or excessive rutting. If disturbance has occurred, pavement subgrade areas should be reworked, moisture conditioned, and properly compacted to the recommendations in this report immediately prior to paving. Please note that if during or after placement of the stabilization or initial lift of pavement, the area is observed to be yielding under vehicle traffic or construction equipment, it is recommended that Terracon be contacted for additional alternative methods of stabilization, or a change in the pavement section. Earthwork General Considerations The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project. All earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project. 13 r. I I I I I 1, I I I I I I I Geotechnical Engineering Report Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 1liEramn Due to the properties of the existing cohesive on -site soils, full depth asphalt pavement is not recommended. Each alternative should be investigated with respect to current material availability and economic conditions. Aggregate base course (if used on the site) should consist of a blend of sand and gravel, which meets strict specifications for quality and gradation. Use of materials meeting Colorado Department of Transportation (CDOT) Class 5 or 6 specifications is recommended for base course. Aggregate base course should be placed in lifts not exceeding six inches and should be compacted to a minimum of 95% Standard Proctor Density (ASTM D698). Asphalt concrete pavement should be composed of a mixture of aggregate, filler, binders, and additives, if required, and approved bituminous material in accordance with the LCUASS Pavement Design Criteria. The asphalt concrete should conform to an approved mix design stating the Hveem and/or Superpave properties, optimum asphalt content, job mix formula and recommended mixing and placing temperatures. Aggregate used in the asphalt concrete should meet particular gradations, such as the Colorado Department of Transportation Grading S, SX or SG specifications. Mix designs should be submitted prior to construction to verify their adequacy. Asphalt material should be placed in maximum 3-inch lifts and should be compacted to a within a range of 92 to 96 % of Maximum Theoretical Density. For areas subject to concentrated and repetitive loading conditions such as dumpster pads, truck delivery docks and ingress/egress aprons, we recommend using a Portland cement concrete pavement with a thickness of at least 7 inches underlain by at least 4 inches of aggregate road base material. Prior to placement of the aggregate road base material, the areas should be thoroughly proofrolled. For dumpster pads, the concrete pavement area should be large enough to support the container and tipping axle of the refuse truck. Long-term pavement performance will be dependent upon several factors, including maintaining subgrade moisture levels and providing for preventive maintenance. The following recommendations should be considered the minimum: • Site grading at a minimum 2% grade away from the pavements; • The subgrade and the pavement surface have a minimum % inch per foot slope to promote proper surface drainage. • Consider appropriate edge drainage and pavement under drain systems, • Install pavement drainage surrounding areas anticipated for frequent wetting (e.g. garden centers, wash racks) • Install joint sealant and seal cracks immediately, I• Seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture migration to subgrade soils; I12 I I I I I I 11 I 11 I I Geotechnical Engineering Report 1reracon Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 ESAL/day, environmental criteria and other factors, the structural numbers (SN) of the pavement sections were determined on the basis of the 1993 AASHTO design equation. In addition to the flexible pavement design analyses, a rigid pavement design analysis was completed, based upon AASHTO design procedures. Rigid pavement design is based on an evaluation of the Modulus of Subgrade Reaction of the soils (K-value), the Modulus of Rupture of the concrete, and other factors previously outlined. The design K-value of 100 for the subgrade soil was determined by correlation to the laboratory tests results. A modulus of rupture of 650 psi (working stress 488 psi) was used for pavement concrete. The rigid pavement thicknesses for each traffic category were determined on the basis of the AASHTO design equation. Recommended alternatives for flexible and rigid pavements, summarized for each traffic area, are as follows: GE DIED, ItI 1ETU FHICKN SE SANG E raifi' ernatrves 11- plta[ " Eonc7ef Surface pha t Eon re e pA98 gat B e �uurse El�ss F As seated �s.�- Portlan Cement Tnta Grade gSS m �cs " or 6� Sub. Concrete - (3)A 3.5 6.0 9.5 Automobile B 3.0 6.0 12.0 21.0 Parking Areas C -1 6.0 6.0 C - 2 12.0 5.5 17.5 (3) A 1.5 2.5 6.0 10.0 Heavy B 3.0 6.0 12.0 21.0 Duty/Truck Traffic Areas C -1 7.0 7.0 C-2 12.0 6.0 18.0 (1) If the asphalt surface course is to consist of Grading S, then the required minimum lift/thickness placed should be 2-inches. If the asphalt surface course is to consist of Grading SX, the required minimum lift/thickness placed should be 1-1/2-inches. ' (2) If fly ash is utilized for the on -site pavement improvement areas to mitigate the soft subgrade materials, it is recommended that at least the upper 12-inches of the prepared subgrade be treated with fly ash. Terracon is available to provide the required laboratory soil and fly ash mix design as well as placement recommendations upon request. (3) Alternative A assumes an approved moisture conditioned subgrade material is obtained beneath the planned paved sections, after an approved proof -roll has been completed 1 11 IJ Geotechnical Engineering Report 1<erraaan Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the aggregate road base section. Soft or weak areas delineated by the proofrolling operations should be undercut or stabilized in -place to achieve the appropriate subgrade support. If the fly ash section is selected, Terracon recommends incorporating approximately 12 percent by weight, Class C fly ash, into the upper 12 to 18-inches of subgrade. Asphalt concrete underlain by crushed aggregate base course with or without a fly ash treated subgrade, and non -reinforced concrete pavement are feasible alternatives for the proposed on -site paved sections. Based on the subsurface conditions encountered at the site, and the laboratory test results, it is recommended the on -site private drives and parking areas be designed using a minimum R-value of 10. ' Pavement design methods are intended to provide structural sections with adequate thickness over a particular subgrade such that wheel loads are reduced to a level the subgrade can support. The support characteristics of the subgrade for pavement design do not account for shrink/swell movements of an expansive clay subgrade such as the soils encountered on this project. Thus, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade. It is, therefore, important to minimize moisture changes in the subgrade to reduce shrink/swell movements. Design of pavements for the project have been based on the procedures outlined in the 1993 Guideline for Design of Pavement Structures by the American Association of State Highway and Transportation Officials (AASHTO). Areas within proposed pavements on the site will be divided into two categories based upon anticipated traffic and usage. Because traffic data is not available, Terracon assumes 18-kip equivalent single axle loads (ESAL's) of 51,100 for automobile parking, and 73,000 for heavy volume and/or truck access areas. When traffic data becomes available, Terracon should be notified so our assumptions can be verified. Local drainage characteristics of proposed pavement areas are considered to vary from fair to good depending upon location on the site. For purposes of this design analysis, fair drainage characteristics are considered to control the design. These characteristics, coupled with the approximate duration of saturated subgrade conditions, result in a design drainage coefficient of ' 1.0 when applying the AASHTO criteria for design. For flexible pavement design, terminal serviceability indexes of 2.0 and 2.5 were utilized along with an inherent reliability of 70%, and 75%, along with a design life of 20 years. Using an estimated design R-value estimated at 10 based on the laboratory test results, appropriate 10 Geotechnical Engineering Report lferracon Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 • Control joints should be provided in slabs to control the location and extent of cracking. • Interior trench backfill placed beneath slabs should be compacted in accordance with recommended specifications outlined below. • In areas subjected to normal loading, a minimum 4-inch layer of clean -graded ' gravel or aggregate base course should be placed beneath upper level interior slabs. In areas of heavier floor loading conditions, consideration should be given to increasing the amount of underslab gravel to a minimum of 6-inches. • Floor slabs should not be constructed on frozen subgrade. ' Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1 R are recommended. Pavement Design and Construction ' Based on the subsurface conditions encountered during the site exploration, it is our opinion the proposed on -site pavement areas are feasible from a geotechnical-engineering point of view, provided the following recommendations are implemented. The subsoils encountered throughout the site are slightly plastic/cohesive soils exhibiting low subgrade strength characteristics and low swell/expansive potential. For determining the required pavement thicknesses, we are using a ' design R-Value of 10 for the on -site subgrade materials. The swell potential of the subgrade soils, based on the LCUASS Pavement Design laboratory testing procedures conducted on a ' sample obtained near the 1-foot level below existing site grades, resulted in swell index values of approximately (-) 0.0 to (+) 0.8%. These values do not exceed the maximum 2 percent criteria established for determining swell -mitigation process in the pavement design procedures. ' Therefore, it is not necessary to mitigate the pavement subgrade to reduce the expansive potential. However, based on our experience with similar soil conditions and our knowledge of the surrounding areas, it is our opinion subgrade stabilization may be required to mitigate soft, unreliable soil. Stabilization may include incorporation of a chemical treatment such as kiln dust, and/or fly ash to ' mitigate soft soil. An alternate would be to over -excavate and replace with approved materials or provide 2-feet of non -expansive granular soils. Depending upon final subgrade elevations for the proposed pavement areas, consideration could be given to placement of 3-inch minus pit run material or 1-1/2-inch clean grade aggregate, embedded into the underlying saturated soils, as a stabilization mechanism. 9 I I I I I [J I I I I Geotechnical Engineering Report Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 lferracon in wall movement. For walls exceeding 8-feet in height, Terracon should be notified so additional recommendations can be provided, if necessary. Seismic Considerations The project site is located in Seismic Risk Zone I of the Seismic Zone Map of the United States as indicated by the 1997 Uniform Building Code. Based upon the nature of the subsurface materials, Soil Profile Type "Sc" should be used for the design of structures for the proposed project (1997 Uniform Building Code, Table No. 16-J). A site classification "C" should be used for the design of structures for the proposed project (2000 International Building Code, Table No. 1615.1.1). Floor Slab Design and Construction Some differential movement of a slab -on -grade floor system is possible should the subgrade soils become elevated in moisture content. To reduce potential slab movements, the subgrade soils should be prepared as outlined in the earthwork section of this report. For structural design of concrete slabs -on -grade, a modulus of subgrade reaction of 100 pounds per cubic inch (pci) may be used for floors supported on existing soils. A modulus of 200 pci may be used for floors supported on non -expansive re -compacted fill or imported structural fill material approved by the geotechnical engineer. As presented on the enclosed boring logs and swell -consolidation test results, low expansive soils are present on this site. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and at least minor cracking in the structure's foundation system and floor slab should be anticipated. The severity of cracking and other cosmetic damage such as uneven floor slabs will probably increase if any modification of the site results in excessive wetting or drying of the expansive materials. Eliminating the risk of movement and cosmetic distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. Some of these options, such as the use of structural floors or overexcavating and replacing expansive materials are discussed in this report. We would be pleased to discuss other construction altematives with you upon request. Additional floor slab design and construction recommendations for floor slabs are as follow: • Remove and re -work approved existing "uncontrolled" fill material from below proposed slabs or replace with approved engineered fill material. • Positive separations and/or isolation joints should be provided between slabs and all foundations, columns or utility lines to allow independent movement. 8 Geotechnical Engineering Report lrerracon ' Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 To reduce the potential for surface water infiltration from impacting the foundation bearing soils ' and/or entering the grease pits, installation of an interior dewatering system is recommended. The interior dewatering system should, at a minimum, include an underslab gravel drainage layer sloped to an interior perimeter drainage system. The interior drainage system should consist of a properly sized perforated pipe, embedded in free - draining gravel, and placed in a trench at least 12 inches in width. The trench should be inset from the interior edge of the nearest foundation a minimum of 12 inches. In addition, the trench should be located such that an imaginary line extending downward at a 45-degree angle from the foundation does not intersect the nearest edge of the trench. Gravel should extend a minimum of I3 inches beneath the bottom of the pipe. The drainage system should be sloped at a minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system. It is suggested that an approximate 15 to 25-gallon per minute pump be installed in the pit to discharge the collection of surface water from the underdrain system. Lateral Earth Pressures For soils above any free water surface, recommended equivalent fluid pressures for unrestrained foundation elements are: • Active: Cohesive soil backfill.....................................................................50 psf/ft Cohesionless soil backfill (granular material).................................35 psf/ft ' Passive: Cohesive soil backfill..................................................................250 psf/ft ' Cohesionless soil backfill (granular material)...............................350 psf/ft Where the design includes restrained elements, the following equivalent fluid pressures are recommended: • At rest: ' Cohesive soil backfill (cohesive soils)............................................65 psf/ft Cohesionless soil backfill (granular material).................................50 psf/ft ' The lateral earth pressures presented above do not include any factor of safety and are not applicable for submerged soils/hydrostatic loading. Fill against grade beams and retaining ' walls should be compacted to densities specified in Earthwork. Compaction of each lift adjacent to walls should be accomplished with hand -operated tampers or other lightweight compactors. Overcompaction may cause excessive lateral earth pressures, which could result 7 Geotechnical Engineering Report lferramn Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 Foundation Systems - Conventional Type Spread Footings ' Based on the anticipated maximum wall and column loads for the project and the low swelling soils encountered during the subsurface exploration, it is our opinion the use of a spread footing ' foundation system bearing upon the native undisturbed subsoils or approved fill material may be utilized to support the proposed buildings. Lower level footings for the grease traps/pits within the Grease Monkey facility should be placed a minimum of 3-feet above the groundwater level. tAll footings for the building should be design using a maximum net allowable bearing pressure of 1,500 psf. In additional all footings should be designed to maintain a minimum dead load ' pressure of 500 psf. Footings should be proportioned to reduce differential foundation movement. Proportioning on the basis of equal total movement is recommended; however, proportioning to relative constant dead -load pressure will also reduce differential settlement between adjacent footings. Total movement resulting from the assumed structural loads is estimated to be on the order of 1-inch. Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, it is imperative proper drainage should be provided in the final design and during ' construction for the structure. Exterior footings should be placed a minimum of 30 inches below finished grade for frost ' protection and to provide confinement for the bearing soils. Finished grade is the lowest adjacent grade for perimeter footings. Footing foundations and masonry walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in masonry walls is recommended. The geotechnical engineer should observe foundation excavations. If the soil conditions encountered differ significantly from those presented in this report, supplemental ' recommendations will be required. ' Lower Level/Grease Pit Construction Groundwater was encountered in the Test Boring No. 1 at an approximate depth of 17-feet below ' existing grades. Therefore, the lower level/grease pits are considered acceptable on the site. However, it is recommended to install a perimeter drainage system around the pits to intercept the potential for surface water infiltration from impacting the foundation bearing stratum and/or enter the pits. 1 6 FLJ I k I I I I I Geotechnical Engineering Report 1rerracon Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 and inundated with water at approximately 500 psf, while samples obtained at the 7 to 9-foot intervals are pre -loaded and inundated with water at approximately 1000 psf to simulate the overburden soil pressure. For this project we performed three (3) swell -consolidation tests, four (4) at an inundation load of 500 psf and three (3) at an inundation load of 150 psf, and the swell index values for the soil samples tested at 500 psf to 1000 psf inundation pressures, varied between approximately (-) 0.0% to (+) 0.8%. Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide uniformity in terminology between geotechnical engineers to provide a relative correlation of slab performance risk to measured swell. "The representative percent swell values are not necessarily measured values; rather, they are a judgment of the swell of the soil and/or bedrock profile likely to influence slab performance." Geotechnical engineers use this information to also evaluate the swell potential risks for foundation and pavement performance based on the risk categories. Recommended Representative Swell Potential Descriptions and Corresponding Slab Performance Risk Categories Rntaire"�cen . I Re eniajiv erdetvel ` . �S ab .eriorniance ' Gategdr z (500 paf$Surc arge �1 00urcha gel �. n,r, Low Otoa3 0<2 Moderate 3 to < 5 2 to < 4 High 5to<8 4to<6 Very High > 8 > 6 The low range for percent swell was used for this project to further evaluate the recommender foundation and pavement design criteria for the site. ENGINEERING ANALYSES AND RECOMMENDATIONS Geotechnical Considerations Based on our review of the subsurface exploration field and laboratory test results, and our understanding of the proposed development, it is our opinion the site is feasible for construction, based on a geotechnical engineering point of view. Based on the maximum anticipated wall and columns loads on the order of 1 to 4 klf and up to 75 kips respectively, the recommended foundation system for supporting the proposed buildings is a conventional type spread footing system bearing on the native, undisturbed subsoils or on approved engineered fill material. 5 PF Geotechnical Engineering Report 1lierramn Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr, and Illinois Dr. Fort Collins, Larimer County, Colorado Project No. 20055122 was encountered at approximate depths 17-feet below existing site grades in Boring No. 2 and extended to the depths explored. The stratification boundaries shown on the enclosed boring logs represent the approximate locations of changes in soil types; in -situ, the transition of materials may be gradual. eGroundwater Conditions ' Groundwater was encountered in Test Boring No. 1 during the initial drilling operations conducted on July 12, 2005 at approximate depths of 17-feet below site grades. These observations represent groundwater conditions at the time of the field exploration, and may not be indicative of other times, or at other locations. Groundwater levels can be expected to fluctuate with varying seasonal and weather conditions as well as irrigation demands on or adjacent to the site. ' Field and Laboratory Test Results Field and laboratory test results indicate the cohesive clay soils are soft to stiff in consistency, exhibit low swell potential, and low bearing characteristics. The fine to coarse granular strata are non -expansive, loose to medium dense in relative density, and exhibit low bearing capacity Lcharacteristics. It is not known whether the fill material encountered on -site, (i.e. the approximate 1-foot of ' material encountered in the general vicinity of Boring Nos. 1 and 2) during the subsurface exploration was properly placed, and/or uniformly compacted; therefore the on -site fill in its in -situ condition is not suitable of supporting foundations, floor slab and/or as a pavement subgrade section without over excavating and replacing. The fill material should be over excavated to the native subsoils below, stockpile for reuse as on -site fill material, then if approved be moisture conditioned to near optimum moisture content and mechanically compacted to 95 percent of ' Standard Proctor Density ASTM D698 in areas where fill is required. Swell — Consolidation Test Results ' The swell -consolidation test is commonly performed to evaluate the swell and/or collapse potential ' of soils for determining foundation, floor slab and pavement design criteria. In this test, relatively undisturbed samples obtained directly from the Dames and Moore ring barrel, (RS) sampling device are placed in a laboratory apparatus and inundated with water under a predetermined load. ' The swell -index is the resulting amount of swell as a percent of the sample's thickness after the inundation period. Samples obtained near the '/ to 2-foot intervals are inundated with water at approximately 150 pounds per square foot (PSF) to simulate the loading conditions of a pavement ' section in general accordance with the Larimer County Urban Area Street Standards (LCUASS) Pavement Design Criteria. Samples collected at the 3 to 4-foot intervals are generally pre -loaded 4 Geotechnical Engineering Report lferramn Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 Penetration resistance measurements were obtained by driving the split -spoon and ring barrel sampler into the subsurface materials with a 140-pound hammer falling 30 inches. The penetration resistance value is a useful index in estimating the consistency, relative density or hardness of the materials encountered. ' Laboratory Testing ' All samples retrieved during the field exploration were returned to the laboratory for observation by the project geotechnical engineer and were classified in general accordance with the Unified Soil Classification System described in Appendix C. At that time, the field descriptions were confirmed ' or modified as necessary and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials. Boring logs were prepared and are presented in Appendix A. ' Laboratory tests were conducted on selected soil samples and are presented in Appendix B. The ' test results were used for the geotechnical engineering analyses, and the development of foundation and earthwork recommendations. All laboratory tests were performed in general accordance with the applicable local or other accepted standards. Selected soil samples were ' tested for the following engineering properties: • Water Content • Swell — Consolidation ' • Dry Density . Atterberg Limits/Soil Classification ' SITE CONDITIONS The site is located at the northwest comer of Custer Drive and Illinois Drive within the Rigden Farms subdivision in Fort Collins, Larimer County, Colorado. The site is generally flat and devoid of vegetation with positive drainage to the south. The site is bordered on the south and east by existing paved roads Custer Drive and Illinois Drive respectively. Commercial/retail type structures are under construction to the north and west of the subject site. SUBSURFACE CONDITIONS ' Soil Conditions ' The subsurface soil conditions encountered in the vicinity of Boring Nos. 1 and 2 generally consisted of approximate 1-foot sandy lean clay overlot grading fill material underlain by native sandy lean clay, which extended to the coarse granular silty sand with gravel strata. The coarse ' granular strata was encountered at approximate depths of 12 to 14-feet below site grades and extended to the depths explored, or to the bedrock below. Weathered siltstone/claystone bedrock 3 I� Geotechnical Engineering Report lferracan ' Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. Fort Collins, Larimer County, Colorado ' Project No. 20055122 • earthwork ' • drainage The recommendations contained in this report are based upon the results of field and laboratory testing, engineering analyses, and experience with similar soil conditions, structures and our understanding of the proposed project. ' PROPOSED CONSTRUCTION The project as we understand it is to construct 2 structures, an approximate 1,279 square foot, ' single story slab on grade car wash structure and an approximate 2,107 square foot, single story with below grade "grease pits" slab on grade Grease Monkey facility, along with associated parking and drive areas. The site is located at the northeast corner of Illinois Drive and Custer ' Drive within the Rigden Farms Development is east Fort Collins, Colorado. Maximum anticipated wall and column loads are assumed to be on the order of 1 to 4 klf, and 10 to 75 kips, respectively. Final grading plans were not provided prior to the subsurface exploration activities, ' however, it is anticipated the finished floor elevations will be at or slightly above existing site grades. ' SITE EXPLORATION The scope of the services performed for this project included a site reconnaissance by an ' engineering geologist, a subsurface exploration program, laboratory testing and engineering analyses. SField Exploration ' As previously stated, Terracon conducted the field exploration activities for the site by drilling two (2) test borings at the locations as shown on the enclosed Test Boring Location Plan, Figure No. 1 included in Appendix A. The field exploration activities were completed on July 12, 2005. Test ' Boring Nos. 1 and 2 were located within the proposed car wash building footprint and were extended to approximate depths of 15 to 25-feet below site grades. The borings were advanced with a truck -mounted drilling rig, utilizing 4-inch diameter solid stem augers. The borings were located in the field by pacing from existing site features and by using a hand held GPS unit. The accuracy of boring locations should only be assumed to the level implied by ' the methods used. Lithologic logs of each boring were recorded by the engineering geologist during the drilling operations. At selected intervals, samples of the subsurface materials were taken by driving a split -spoon (SS) and a Dames and Moore ring barrel, (RS) sampling device. 2 GEOTECHNICAL ENGINEERING REPORT ' PROPOSED CARWASH and GREASE MONKEY FACILITIES NORTHWEST CORNER OF CUSTER DRIVE AND ILLINOIS DRIVE ' RIGDEN FARMS FORT COLLINS, LARIMER COUNTY, COLORADO ' TERRACON PROJECT NO.20055122 AUGUST 4, 2005 INTRODUCTION This report contains the results of our geotechnical engineering exploration for the proposed ' Carwash and Grease Monkey buildings to be located at the northwest corner of Custer Drive and Illinois Drive within the Rigden Farms Subdivision in east Fort Collins, Larimer County, Colorado. The site is located in the Northwest % of Section 29, Township 7 North, Range 68 West of the 6th ' Principal Meridian, Larimer County, Colorado. A Phase I Environmental Site Assessment (Phase I ESA) was conducted by Terracon for the ' proposed TDS development property in conjunction with our geotechnical engineering exploration. For further information and findings thereof, please refer to Terracon's Phase I ESA Report dated July 20, 2005, Project No. 20057720. ' Terracon's initial scope of services for conducting the geotechnical engineering exploration was to drill two test borings per building footprint and provide recommendations based on the findings ' from these four (4) borings. However, during the construction stages for the nearby retail development, the general contractor had recently asphalt paved the area for the proposed Grease Monkey building. Therefore only the two (2) test borings for the proposed car wash facility were drilled at this time. However, based on our experience with the surrounding development as well as the consistency of the subsurface conditions encountered in Boring Nos. 1 and 2 we are providing design criteria for the Grease Monkey building realizing that during construction phases a comprehensive foundation excavation observation will be required. ' The purpose of these services is to provide information and geotechnical engineering recommendations relative to: ' subsurface soil conditions • groundwater conditions ' foundation design and construction • floor slab design and construction ' lateral earth pressures • pavement design and construction ' TABLE OF CONTENTS ' l Letter of TransmittalPage No. INTRODUCTION..................................................................................................................1 PROPOSED CONSTRUCTION............................................................................................2 ' SITE EXPLORATION........................................................................................................... 2 FieldExploration.......................................................................................................... 2 ' Laboratory Testing...................................................................................................... 3 SITECONDITIONS..............................................................................................................3 ' SUBSURFACE CONDITIONS ..............................................................................................3 SoilConditions............................................................................................................ 3 GroundwaterConditions..............................................................................................4 Field and Laboratory Test Results...............................................................................4 Swell -Consolidation Test Results................................................................................ 5 ENGINEERING ANALYSES AND RECOMMENDATIONS.................................................. 5 Geotechnical Considerations.......................................................................................5 ' Foundation Systems - Conventional Type Spread Footings ........................................ 6 LateralEarth Pressures...............................................................................................7 Seismic Considerations............................................................................................... 8 ' Floor Slab Design and Construction............................................................................ 8 Pavement Design and Construction............................................................................ 9 Earthwork..................................................................................................................13 General Considerations....................................................................................13 SitePreparation...............................................................................................14 Subgrade Preparation......................................................................................14 Fill Materials and Placement............................................................................15 ' Excavation and Trench Construction...............................................................15 Additional Design and Construction Considerations.........................................16 Exterior Slab Design and Construction.............................................................16 Underground Utility Systems............................................................................16 SurfaceDrainage.............................................................................................17 ' GENERAL COMMENTS.....................................................................................................17 APPENDIX A Test Boring Location Plan — Figure No. 1 Logs of Borings ' APPENDIX B Laboratory Test Results APPENDIX C General Notes ' Geotechnical Engineering Report Terramn Proposed Automatic Carwash and Grease Monkey Northwest Corner of Custer Dr. and Illinois Dr. ' Fort Collins, Larimer County, Colorado Project No. 20055122 ' explored. Groundwater was encountered in test boring No. 1 during the initial drilling operations conducted on July 12, 2005 at approximate depths of 17 feet below site grades. We anticipate wall and column loads for both buildings to be on the order of 1 to 4 kips per linear foot, and 10 to 75 kips respectively and we assume the finished floor elevations will be at or near existing site grades. Therefore, with the anticipated wall and column loads and the subsurface conditions ' encountered, a conventional type spread footing foundation may be utilized to support the proposed structures. Conventional slab on grade is feasible for the site provided the subgrade preparation and the recommendations included herein are followed. Other design and construction recommendations, based upon geotechnical conditions, are presented in the report. ' We appreciate being of service to you in the geotechnical engineering phase of this project, and are ' prepared to assist you during the construction phases as well. If you have any questions concerning this report or any of our testing, inspection, design and consulting services please feel free to contact US. ' Sincerely, TERRACON C riK stophe"'r Gempedine Engineering Geologist ' Copies to: Addressee (4) nager August4, 2005 Irerracon Consulting Engineers & Scientists Terracon Consultants, Inc. Automotive Development Group, Inc. 301 North Howes 5340 South Quebec Street- Suite 330 S Fort Collins, Colorado 8Phone 970.484.0359359 ' Englewood, Colorado 80111 Fax 970.484.0454 www.terracon.com Attn: Jody Newton ' Re: Geotechnical Engineering Report Proposed Carwash and Grease Monkey Facilities Northwest Corner of Custer Drive and Illinois Drive- Rigden Farms Fort Collins, Larimer County, Colorado Terracon Project No. 20055122 ' Terracon has completed a geotechnical engineering exploration for the proposed Carwash and Grease Monkey buildings to be located at the northwest comer of Custer Drive and Illinois Drive within the ' Rigden Farms Subdivision in east Fort Collins, Larimer County, Colorado. This study was performed in general accordance with our Proposal No. D2005261-GEO, dated June 29, 2005. ' A Phase I Environmental Site Assessment (Phase I ESA) was conducted by Terracon for the proposed TDS development property in conjunction with our geotechnical engineering exploration. For further information and findings thereof, please refer to Terracon's Phase I ESA Report dated July 20, 2005, ' Project No. 20057720. Terracon's initial scope of services for conducting the geotechnical engineering exploration was to drill two test borings per building footprint and provide recommendations based on the findings from these four (4) borings. However, during the construction stages for the nearby retail development, the general contractor had recently asphalt paved the area for the proposed Grease Monkey building. Therefore ' only the two (2) test borings for the proposed car wash facility were drilled at this time. However, based on our experience with the surrounding development as well as the consistency of the subsurface ' conditions encountered in Boring Nos. 1 and 2 we are providing design criteria for the Grease Monkey building realizing that during construction phases a comprehensive foundation excavation observation will be required. ' The results of our engineering study, including the boring location diagram, laboratory test results, test boring records, and geotechnical recommendations needed to aid in the design and construction of ' foundations, pavements and other earth connected phases of this project are attached. The subsurface soil conditions encountered in the vicinity of Boring Nos. 1 and 2 generally consisted of ' approximate 1-foot sandy lean clay overlot grading fill material underlain by native sandy lean clay, which extended to the coarse granular silty sand with gravel strata. The coarse granular strata was ' encountered at approximate depths of 12 to 14-feet below site grades and extended to the depths explored, or to the bedrock below. Weathered siltstone/claystone bedrock was encountered at approximate depths 17-feet below existing site grades in Boring No. 2 and extended to the depths 1 Delivering Success for Clients and Employees Since 1965 More Than 70 Offices Nationwide GEOTECHNICAL ENGINEERING REPORT PROPOSED CARWASH and GREASE MONKEY FACILITIES NORTHWEST CORNER OF CUSTER DRIVE AND ILLINOIS DRIVE RIGDEN FARMS DEVELOPMENT FORT COLLINS, LARIMER COUNTY, COLORADO TERRACON PROJECT NO.20055122 AUGUST 4, 2005 Prepared for. AUTOMOTIVE DEVELOPMENT GROUP, INC 5340 SOUTH QUEBEC STREET- SUITE 330 S ENGLEWOOD, COLORADO 80111 ATTN: JODY NEWTON Prepared by. Terracon 301 North Howes Street Fort Collins, Colorado 80521 1rerraco