Loading...
HomeMy WebLinkAboutCSU LAKE AND PROSPECT PARKING LOT - FDP190018 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGeotechnical Subsurface Exploration Program Colorado State University Lake Street Surface Parking Lot South of Canvas Stadium Fort Collins, Colorado Prepared For: Colorado State University 251 Edison Drive Fort Collins, CO 80521 Attn: Shelly Carroll Job Number: 18-0057 January 14th, 2019 TABLE OF CONTENTS Page Purpose and Scope of Study ....................................................................................... 1 Site Conditions ............................................................................................................ 2 Subsurface Exploration and Laboratory Testing .......................................................... 4 Subsurface Conditions ................................................................................................ 5 Pavement Sections ..................................................................................................... 6 Water-Soluble Sulfate .............................................................................................. 11 Project Earthwork ..................................................................................................... 12 Surface Drainage .................................................................................................... 14 Closure...................................................................................................................... 15 Locations of Test Holes ................................................................................... Figure 1 Logs of Test Holes ............................................................................. Figures 2 and 3 Legend and Notes ........................................................................................... Figure 4 Summary of Laboratory Test Results .............................................................. Table 1 Pavement Thickness Calculations ............................................................. Appendix A CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 1 of 18 PURPOSE AND SCOPE OF STUDY This report presents the results of a geotechnical evaluation performed by GROUND Engineering Consultants, Inc. (GROUND) for the Colorado State University in support of design of the proposed CSU: Lake Street Surface Parking Lot in Fort Collins, Colorado. Our study was conducted in general accordance with GROUND’s Proposal No. 1812- 2193, dated December 18th, 2018. A field exploration program was conducted to obtain information on the subsurface conditions. Material samples obtained during the subsurface exploration were tested in the laboratory to provide data on the engineering characteristics of the on-site soils. The results of the field exploration and laboratory testing are presented herein. This report has been prepared to summarize the data obtained and to present our findings and conclusions based on the proposed development/improvements and the subsurface conditions encountered. Design parameters and a discussion of engineering considerations related to the proposed improvements are included herein. This report should be understood and utilized in its entirety; specific sections of the text, drawings, graphs, tables, and other information contained within this report are intended to be understood in the context of the entire report. This includes the Closure section of the report which outlines important limitations on the information contained herein. This report was prepared for design purposes of the Colorado State University based on our understanding of the proposed project at the time of preparation of this report. The data, conclusions, opinions, and geotechnical parameters provided herein should not be construed to be sufficient for other purposes, including the use by contractors, or any other parties for any reason not specifically related to the design of the project. Furthermore, the information provided in this report was based on the exploration and testing methods described below. Deviations between what was reported herein and the actual surface and/or subsurface conditions may exist, and in some cases those deviations may be significant. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 2 of 18 The proposed construction included site improvements, primarily including new pavement for the proposed Lake Street Surface Parking Lot. In addition to the new pavement, GROUND understands there will be associated sidewalk, curb and gutter, bus drop off, detention pond, and landscaping. If the proposed construction differs from those described above, or changes subsequently, GROUND should be notified to re-evaluate the parameters provided in this report. SITE CONDITIONS At the time of our exploration, the project site exists as a vacant lot situated between Prospect Road on the south, Lake Street on the north, and residential housing located east and west of the lot. Based on our surface and subsurface observations and reviewing Google Earth historical view from August of 2012, it appears that the site was occupied by 4 residential type structures as well as deciduous trees and landscaping. It appears that the previous structures were demolished and any foundations backfilled. Remnant concrete flatwork was observed CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 3 of 18 on the south half of the site as well as some existing sod grass observed on the north half of the site. The topography across the site was generally flat with no appreciable slopes. A shallow layer of man-made fill materials were observed in the test holes and existing man-made fill materials should be expected in the areas of the previously backfilled foundations associated with the previous existing structures. The subgrade below the fill layer primarily consisted of red sandy clay to sandy silt materials. The exact extents, limits, and composition of any man-made fill were not determined as part of the scope of work addressed by this study, and should be expected to exist at varying depths and locations across the site. GROUND should be retained to observe the subgrade materials after construction stripping of topsoil materials. Several test pits should be excavated within the footprints of the previous structures to determine the extents of any man made fill. Existing man-made fills should be verified for proper compaction / density. At that time it may be required to perform shallow localized overexcavations to remove any fills that have not been properly placed and compacted. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 4 of 18 SUBSURFACE EXPLORATION AND LABORATORY TESTING The subsurface exploration for the project was conducted on January 4th and January 14th, 2019 (separate visits due to a break down during drilling of the last two holes on January 4th, 2019). A total of eight (8) test holes were drilled within the parking lot. The test holes were drilled with a trailer-mounted, continuous flight power auger rig to evaluate the subsurface conditions as well as to retrieve soil samples for laboratory testing and analysis. The test holes were drilled to depths ranging from approximately 5 to 8 feet below existing grades. A representative of GROUND directed the subsurface exploration, logged the test holes in the field, and prepared the soil and bedrock samples for transport to our laboratory. Samples of the subsurface materials were retrieved with a 2-inch I.D. California liner sampler. The sampler was driven into the substrata with blows from a 140-pound hammer falling 30-inches. This procedure is similar to the Standard Penetration Test described by ASTM Method D1586. Penetration resistance values, when properly evaluated, indicate the relative density or consistency of soils. Depths at which the samples were obtained and associated penetration resistance values are shown on the test hole logs. The approximate locations of the test holes are shown in Figure 1. Logs of the exploratory test holes are presented in Figure 2. Explanatory notes and a legend are provided in Figure 3. Samples retrieved from our test holes were examined and visually classified in the laboratory by the project engineer. Laboratory testing of soil samples obtained from the subject site included standard property tests, such as natural moisture contents, grain size analyses and swell-consolidation tests. Laboratory tests were performed in general accordance with applicable ASTM protocols. Results of the laboratory testing program are summarized on Table 1. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 5 of 18 SUBSURFACE CONDITIONS The subsurface conditions encountered in the test hole are described in the table below. Approximate Depth range below existing grade (feet) Material Type Material Description Start End 0 3” to 6” Topsoil Topsoil was generally sparse on the southern half of the lot and more predominant on the north side of the site associated with the sod grass 0 6” Gravel / Landscape Gravel Localized landscape gravels were observed on portions of the north half of the site 3” to 6” *1 *Man-made Fill Sandy clay to clayey sand, fine to medium grained with some gravel, medium plastic, moist, and brown in color. 3 8 Sandy Clay Sandy clay to clayey sand, fine to medium grained, medium plastic, stiff, moist to wet, brown to red-brown in color. *Note: as indicated previously, manmade fill materials are anticipated to exist across the site at greater depths associated with the previous existing residential structure foundations. The exact extents, limits, and composition of any man- made fill were not determined as part of the scope of work addressed by this study, and should be expected to exist at varying depths and locations across the site. Swell-Consolidation Testing yielded a result of 0.1 percent consolidation at a surcharge pressure of 200 psf. Groundwater was not encountered in the test holes advanced at the site to the depth explored up to approximately 8 feet below existing grade at the time of drilling. However, groundwater levels can be expected to fluctuate, however, in response to annual and longer-term cycles of precipitation, irrigation, surface drainage, nearby rivers and creeks, land use, and the development of transient, perched water conditions. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 6 of 18 PAVEMENT SECTIONS A pavement section is a layered system intended 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. Standard practice in pavement design describes a typical flexible pavement section as a “20-year” design pavement. However, most pavements will not remain in satisfactory condition without routine maintenance and rehabilitation procedures performed throughout the life of the pavement. For this project, private roadway design methods will be utilized. Subgrade Materials: Based on the results of our field and laboratory studies, the subgrade materials below the project pavements consisted largely of sandy clay to sandy silt with some granular fill. A shallow layer of man-made fill material was observed in the test holes and existing man-made fill materials should be expected in the areas of the previously backfilled foundations associated with the previous existing structures. It is standard care of practice to remove undocumented fill materials and replace them in a properly moisture conditioned and compacted state with associated quality control / compaction testing for documentation. GROUND should be retained to observe the subgrade materials after removal of topsoil materials and abandonment of any onsite utilities. Several test pits should be excavated within the approximate footprints of the previously existing structures to determine the extents of man-made fill. Existing man-made fills should be verified for proper compaction / density. Any fills suspect of not being properly compacted shall be locally over-excavated and replaced with properly placed and compacted site soils. However it is recommended in any instance that the upper 12 inches of subgrade materials across the site be moisture conditioned and compacted below the proposed pavement section. All fill materials should be placed and compacted per the criteria set forth in the Project Earthwork section of this report. Based on our experience with the site soils and similar materials, an R-value of 10 was estimated for the on-site materials. This value converts to a resilient modulus value of 3,562 psi based on CDOT correlation tables. It is important to note that significant decreases in soil support as quantified by the resilient modulus have been observed as the moisture content increases above the optimum. Therefore, pavements that are not CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 7 of 18 properly drained may experience a loss of the soil support and subsequent reduction in pavement life. Anticipated Traffic: Based on our experience with similar projects, a moderate/conservative equivalent 18-kip daily load application (EDLA) value of 15 was assumed for the general parking lot and drive lanes servicing the parking lot. The EDLA value of 15 was converted to an equivalent 18-kip single axle load (ESAL) value of 109,500 for a 20-year design life. If anticipated traffic loadings differ significantly from this assumed value, GROUND should be notified to re-evaluate the pavement thicknesses provided below. Pavement Sections The soil resilient modulus and the ESAL values were used to determine the required design structural number for the project pavements. The required structural number was then used to develop the pavement sections. Pavement designs were based on the DARWin™ computer program that solves the 1993 AASHTO pavement design equations. A Reliability Level of 80 percent was utilized to develop the pavement sections, together with a Serviceability index loss of 2.5. An overall standard of deviation of 0.44 also was used for the flexible sections. A structural coefficient of 0.44 and 0.11 was used for hot bituminous asphalt and CDOT Class 5/6 aggregate base course (ABC) materials respectively. The resultant minimum pavement sections that should be used at the facility are tabulated below. Minimum Pavement Sections Location Composite Pavement Section Rigid Section (Inches Asphalt over Inches ABC) (inches Concrete / inches ABC) Parking Lot Asphalt (Stalls and Drives) 4.5 / 8 - Heavy Vehicle or High Turning Stress Pavement Bus Drop Off - 6.5 / 6 Heavy vehicle and high turning stress traffic serving the parking lot impose high stress on the pavement such as bus stop locations, trash collection areas and trash truck turn arounds should be provided with rigid pavements consisting of 6.5 or more inches of portland cement concrete underlain by 6 or more inches of properly compacted CDOT Class 5 or 6 Aggregate Base Course. (An equivalent flexible section for these areas would not perform as well as the concrete section where heavy vehicles are parked, stop suddenly, turn repeatedly, etc.) CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 8 of 18 Pavement Materials: Asphalt pavement should consist of a bituminous plant mix composed of a mixture of aggregate and bituminous material. Asphalt mixture(s) should meet the requirements of a job-mix formula established by a qualified engineer as well as applicable local municipality design requirements. GROUND suggests utilizing a ¾” S PG(58-28) type mix for the lower lifts and a ½” SX PG(64-22) type mix for the top mat. Aggregate base material should meet the criteria of CDOT Class 5 or 6 aggregate base course. We encourage the use of recycled concrete materials that meet the CDOT Class 5 or 6 aggregate base course grading requirements. Base course should be placed in and compacted in accordance with the criteria in the Project Earthwork section of this report. Where rigid (concrete) pavements are placed, the concrete should consist of a plant mix composed of a mixture of aggregate, portland cement and appropriate admixtures meeting the requirements of a job-mix formula established by a qualified engineer as well as applicable local municipality design requirements. Concrete should have a minimum modulus of rupture of third point loading of 650 psi. Normally, concrete with a 28-day compressive strength of 4,500 psi should develop this modulus of rupture value. The concrete should be air-entrained with approximately 6 percent air and should have a minimum cement content of 6 sacks per cubic yard. Maximum allowable slump should be 4 inches. These concrete mix design criteria should be coordinated with other project requirements including any criteria for sulfate resistance. To reduce surficial spalling resulting from freeze-thaw cycling, we suggest that pavement concrete meet the requirements of CDOT Class P concrete. In addition, the use of de-icing salts on concrete pavements during the first winter after construction will increase the likelihood of the development of scaling. Placement of flatwork concrete during cold weather so that it is exposed to freeze-thaw cycling before it is fully cured also increases its vulnerability to scaling. Concrete placed during cold weather conditions should be blanketed or tented to allow full curing. Depending on the weather conditions, this may result in 3 to 4 weeks of curing, or more. Concrete pavements should contain sawed or formed joints. CDOT and various industry groups provide guidelines for proper design and concrete construction and associated jointing. In areas of repeated turning stresses, including the bus and firetruck lanes, the concrete pavement joints should be fully tied and doweled. Example layouts for joints, CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 9 of 18 as well as ties and dowels, that may be applicable can be found in CDOT’s M standards, found at the CDOT website: http://www.dot.state.co.us/DesignSupport/. PCA, ACI, and ACPA publications also provide useful guidance in these regards. Subgrade Preparation: It should be expected that the subgrade soils below the proposed pavement section will likely be several percentage points below the optimum moisture content (dry and hard). This is likely due to the regions lack of moisture during the last 4 months. Note: We anticipate that unstable conditions may be encountered locally and a geotechnical engineer should be retained to provide direction for the specific conditions encountered at the time of construction. The contractor should be prepared to scarify, mix, moisture-condition, and re-compact the existing subgrade materials to a minimum depth of 12 inches. Although subgrade preparation to a depth of 12 inches is typical in the project area, pavement performance commonly can be improved by a greater depth of moisture-density conditioning of the soils. Over-excavation to greater depths may need to be performed on localized areas depending on the conditions exposed during construction. Subgrade preparation should extend the full width of the pavement. The subgrade for sidewalks and other project hardscaping also should be prepared in the same manner (moisture density treatment to a depth of 12-inches). Criteria and standards for fill placement and compaction are provided in the Project Earthwork section of this report. The contractor should be prepared either dry the subgrade materials or moisten them, as needed, prior to compaction. Proof Rolling Immediately prior to paving, the subgrade should be proof rolled with a heavily loaded, pneumatic tired vehicle. Areas that show excessive deflection during proof rolling should be excavated and replaced and/or stabilized. Areas allowed to pond prior to paving will require significant re-working prior to proof-rolling. Establishment of a firm paving platform (as indicated by proof rolling) is an additional requirement beyond proper fill placement and compaction. It is possible for soils to be compacted within the limits indicated in the Project Earthwork section of this report and fail proof rolling, particularly in the upper range of specified moisture contents. Additional Considerations: The collection and diversion of surface drainage away from paved areas is extremely important to satisfactory performance of the pavements. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 10 of 18 The subsurface and surface drainage systems should be carefully designed to ensure removal of the water from paved areas and subgrade soils. Allowing surface waters to pond on pavements will cause premature pavement deterioration. Where topography, site constraints or other factors limit or preclude adequate surface drainage, pavements should be provided with edge drains to reduce loss of subgrade support. The long-term performance of the pavement also can be improved greatly by proper backfilling and compaction behind curbs, gutters, and sidewalks so that ponding is not permitted and water infiltration is reduced. Landscape irrigation in planters adjacent to pavements and in “island” planters within paved areas should be carefully controlled or differential heave and/or rutting of the nearby pavements will result. Drip irrigation systems should be used for such planters to reduce over-spray and water infiltration beyond the planters. Enclosing the soil in the planters with plastic liners and providing them with positive drainage also will reduce differential moisture increases in the surrounding subgrade soils. In our experience, infiltration from planters adjacent to pavements is a principal source of moisture increase beneath those pavements. This wetting of the subgrade soils from infiltrating irrigation commonly leads to loss of subgrade support for the pavement with resultant accelerating distress, loss of pavement life and increased maintenance costs. This is particularly the case in the later stages of project construction after landscaping has been emplaced but heavy construction traffic has not ended. Heavy vehicle traffic over wetted subgrade commonly results in rutting and pushing of flexible pavements, and cracking of rigid pavements. Where the subgrade soils are expansive, wetting also typically results in increased pavement heave. In relatively flat areas where design drainage gradients necessarily are small, subgrade settlement or heave can obstruct proper drainage and yield increased infiltration, exaggerated distress, etc. (These considerations apply to project flatwork, as well.) Also, GROUND’s experience indicates that longitudinal cracking is common in asphalt- pavements generally parallel to the interface between the asphalt and concrete structures such as curbs, gutters or drain pans. Distress of this type is likely to occur even where the subgrade has been prepared properly and the asphalt has been compacted properly. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 11 of 18 The anticipated traffic loadings do not include excess loading conditions imposed by heavy construction vehicles. Consequently, heavily loaded concrete, lumber, and building material trucks can have a detrimental effect on the pavement. Most pavements will not remain in satisfactory condition without regular maintenance and rehabilitation procedures performed throughout the life of the pavement. Maintenance and rehabilitation measures preserve, rather than improve, the structural capacity of the pavement structure. Therefore, an effective program of regular maintenance should be developed and implemented to seal cracks, repair distressed areas, and perform thin overlays throughout the lives of the pavements. The greatest benefit of pavement overlaying will be achieved by overlaying sound pavements that exhibit little or no distress. Crack sealing should be performed at least annually and a fog seal/chip seal program should be performed on the pavements every 3 to 5 years. After approximately 8 to 10 years after construction, patching, additional crack sealing, and asphalt overlay may be required. Prior to overlays, it is important that all cracks be sealed with a flexible, rubberized crack sealant in order to reduce the potential for propagation of the crack through the overlay. If actual traffic loadings exceed the values used for development of the pavement sections, however, pavement maintenance measures will be needed on an accelerated schedule. WATER-SOLUBLE SULFATES The concentrations of water-soluble sulfates measured in a selected sample retrieved from the test holes was approximately 0.03 percent by weight. (See Table 1.) Such concentrations of water-soluble sulfates represent a negligible degree of sulfate attack on concrete exposed to these materials. Degrees of attack are based on the scale of 'negligible,' 'moderate,' 'severe' and 'very severe' as described in the “Design and Control of Concrete Mixtures,” published by the Portland Cement Association (PCA). The Colorado Department of Transportation (CDOT) utilizes a corresponding scale with 4 classes of severity of sulfate exposure (Class 0 to Class 3) as described in the published table below. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 12 of 18 REQUIREMENTS TO PROTECT AGAINST DAMAGE TO CONCRETE BY SULFATE ATTACK FROM EXTERNAL SOURCES OF SULFATE Severity of Sulfate Exposure Water-Soluble Sulfate (SO4) In Dry Soil (%) Sulfate (SO4) In Water (ppm) Water Cementitious Ratio (maximum) Cementitious Material Requirements Class 0 0.00 to 0.10 0 to 150 0.45 Class 0 Class 1 0.11 to 0.20 151 to 1500 0.45 Class 1 Class 2 0.21 to 2.00 1501 to 10,000 0.45 Class 2 Class 3 2.01 or greater 10,001 or greater 0.40 Class 3 Based on this datum use of a special, sulfate-resistant cement in project concrete appears necessary. PROJECT EARTHWORK The earthwork criteria below are based on our interpretation of the geotechnical conditions encountered in the test holes. Where these criteria differ from applicable municipal specifications, e.g., for trench backfill compaction along a public utility line, the latter should be considered to take precedence. General Considerations: Prior to earthwork construction, existing concrete, asphalt, vegetation, and other deleterious materials should be removed and disposed of off-site. Relic underground utilities should be abandoned in accordance with applicable regulations, removed as necessary, and properly capped. Topsoil present on-site should not be incorporated into ordinary fills. Instead, topsoil should be stockpiled during initial grading operations for placement in areas to be landscaped or for other approved uses. Use of Existing Native Soils: Overburden soils that are free of trash, organic material, construction debris, and other deleterious materials are suitable, in general, for placement as compacted fill. Organic materials should not be incorporated into project fills. Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) larger than 3 inches in maximum dimension will require special handling and/or placement to be incorporated into project fills. In general, such materials should be CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 13 of 18 placed as deeply as possible in the project fills. A Geotechnical Engineer should be consulted regarding appropriate direction for usage of such materials on a case-by-case basis when such materials have been identified during earthwork. Standard recommendations that likely will be generally applicable can be found in Section 203 of the current CDOT Standard Specifications for Road and Bridge Construction. Imported Fill Materials: If it is necessary to import material to the site, the imported soils should be free of organic material, and other deleterious materials. Imported material should consist of soils that have less than 50 percent passing the No. 200 Sieve and should have a plasticity index of less than 15. Representative samples of the materials proposed for import should be tested and approved prior to transport to the site. Fill Platform Preparation: Prior to filling, the top 8 to 12 inches of in-place materials on which fill soils will be placed should be scarified, moisture conditioned and properly compacted in accordance with the parameters below to provide a uniform base for fill placement. If over-excavation is to be performed, then these parameters for subgrade preparation are for the subgrade below the bottom of the specified over-excavation depth. If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material, additional material should be excavated, or other measures taken to establish a firm platform for filling. The surfaces to receive fill must be effectively stable prior to placement of fill. General Considerations for Fill Placement: Fill soils should be thoroughly mixed to achieve a uniform moisture content, placed in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted. No fill materials should be placed, worked, rolled while they are frozen, thawing, or during poor/inclement weather conditions. Care should be taken with regard to achieving and maintaining proper moisture contents during placement and compaction. Materials that are not properly moisture conditioned may exhibit significant pumping, rutting, and deflection at moisture contents near optimum and above. The contractor should be prepared to handle soils of this type, including the use of chemical stabilization, if necessary. Compaction areas should be kept separate, and no lift should be covered by another until relative compaction and moisture content within the specified ranges are obtained. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 14 of 18 Soils that classify as GP, GW, GM, GC, SP, SW, SM, or SC in accordance with the USCS classification system (granular materials) should be compacted to 95 or more percent of the maximum modified Proctor dry density at moisture contents within 2 percent of optimum moisture content as determined by ASTM D1557. Soils that classify as ML or CL should be compacted to 95 percent of the maximum standard Proctor density at moisture contents from 2 percent below to 2 percent above the optimum moisture content as determined by ASTM D698. SURFACE DRAINAGE The site soils are relatively stable with regard to moisture content – volume relationships at their existing moisture contents. Other than the anticipated, post-placement settlement of fills, post-construction soil movements will result primarily from the introduction of water into the soils underlying the proposed hardscaping and pavements. Based on the site surface and subsurface conditions encountered in this study, we do not anticipate a rise in the local water table sufficient to approach hardscaping or pavement elevations. Therefore, wetting of the soils likely will result from infiltrating surface waters (precipitation, irrigation, etc.), and water flowing along constructed pathways such as bedding in utility pipe trenches. The following drainage measures should be followed both during construction and as part of project design. The facility should be observed periodically to evaluate the surface drainage and identify areas where drainage is ineffective. Routine maintenance of site drainage should be undertaken throughout the design life of the proposed improvements. It is important to note that significant decreases in soil support as quantified by the resilient modulus have been observed as the moisture content increases above the optimum. Therefore, pavements that are not properly drained may experience a loss of the soil support and subsequent reduction in pavement life. 1) Wetting or drying of the subgrade areas should be avoided during and after construction. Permitting increases/variations in moisture to the adjacent or supporting soils may result in increased total and/or differential movements. 2) Drainage also should be established to direct water into a detention area or offsite. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 15 of 18 3) In GROUND’s experience, it is common during construction that in areas of partially completed paving or hardscaping, bare soil behind curbs and gutters, and utility trenches, water is allowed to pond after rain or snow-melt events. Wetting of the subgrade can result in loss of subgrade support and increased settlements / increase heave. By the time final grading has been completed, significant volumes of water can already have entered the subgrade, leading to subsequent distress and failures. The contractor should maintain effective site drainage throughout construction so that water is directed into appropriate drainage structures. In no case should water be permitted to pond adjacent to or on sidewalks, hardscaping, or other improvements as well as utility trench alignments, which are likely to be adversely affected by moisture-volume changes in the underlying soils or flow of infiltrating water. 4) Irrigation water – both that applied to landscaped areas and over-spray – commonly is a significant cause of distress to improvements. Where (near-) saturated soil conditions are sustained, distress to nearby improvements should be anticipated. Irrigation sprinkler heads should be deployed so that applied water is not introduced near or into subgrade soils. Landscape irrigation should be limited to the minimum quantities necessary to sustain healthy plant growth. Use of drip irrigation systems can be beneficial for reducing over-spray beyond planters. Controlling rates of moisture increase beneath improvements should take higher priority than minimizing landscape plant losses. CLOSURE Geotechnical Review The author of this report or a GROUND principal should be retained to review project plans and specifications to evaluate whether they comply with the intent of the measures discussed in this report. The review should be requested in writing. The geotechnical conclusions and parameters presented in this report are contingent upon observation and testing of project earthwork by representatives of GROUND. If another geotechnical consultant is selected to provide materials testing, then that CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 16 of 18 consultant must assume all responsibility for the geotechnical aspects of the project by concurring in writing with the parameters in this report, or by providing alternative parameters. Materials Testing Colorado State University should consider retaining a geotechnical engineer to perform materials testing during construction. The performance of such testing or lack thereof, however, in no way alleviates the burden of the contractor or subcontractor from constructing in a manner that conforms to applicable project documents and industry standards. The contractor or pertinent subcontractor is ultimately responsible for managing the quality of their work; furthermore, testing by the geotechnical engineer does not preclude the contractor from obtaining or providing whatever services that he deems necessary to complete the project in accordance with applicable documents. Limitations This report has been prepared for Colorado State University as it pertains to design of the proposed CSU: Lake Street Surface Parking Lot as described herein. It should not be assumed to contain sufficient information for other parties or other purposes. The Client has agreed to the terms, conditions, and liability limitations outlined in our agreement between the Colorado State University and GROUND. Reliance upon our report is not granted to any other potential owner, contractor, or lender. Requests for third-party reliance should be directed to GROUND in writing; granting reliance by GROUND is not guaranteed. In addition, GROUND has assumed that project construction will commence by summer 2019. Any changes in project plans or schedule should be brought to the attention of a geotechnical engineer, in order that the geotechnical conclusions in this report may be re-evaluated and, as necessary, modified. The geotechnical conclusions in this report were based on subsurface information from a limited number of exploration points, as shown in Figure 1, as well as the means and methods described herein. Subsurface conditions were interpolated between and extrapolated beyond these locations. It is not possible to guarantee the subsurface conditions are as indicated in this report. Actual conditions exposed during construction may differ from those encountered during site exploration. In addition, a contractor who obtains information from this report for development of his scope of work or cost estimates does so solely at their own risk and may find the geotechnical information in this report to be inadequate for their purposes or find the geotechnical conditions CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 17 of 18 described herein to be at variance with their experience in the greater project area. The contractor should obtain the additional geotechnical information that is necessary to develop their workscope and cost estimates with sufficient precision. This includes, but is not limited to, information regarding excavation conditions, earth material usage, current depths to groundwater, etc. Because of the necessarily limited nature of the subsurface exploration performed for this study, the contractor should be allowed to evaluate the site using test pits or other means to obtain additional subsurface information to prepare their bid. If during construction, surface, soil, or groundwater conditions appear to be at variance with those described herein, a geotechnical engineer should be retained at once, so that our conclusions for this site may be re-evaluated in a timely manner and dependent aspects of project design can be modified, as necessary. The materials present on-site are stable at their natural moisture content, but may change volume or lose bearing capacity or stability with changes in moisture content. Performance of the proposed pavement will depend on implementation of the conclusions and information in this report and on proper maintenance after construction is completed. Because water is a significant cause of volume change in soils and rock, allowing moisture infiltration may result in movements, some of which will exceed estimates provided herein and should therefore be expected by Colorado State University. ALL DEVELOPMENT CONTAINS INHERENT RISKS. It is important that ALL aspects of this report, as well as the estimated performance (and limitations with any such estimations) of proposed improvements are understood by Colorado State University. Utilizing the geotechnical parameters and measures herein for planning, design, and/or construction constitutes understanding and acceptance of the conclusions with regard to risk and other information provided herein, associated improvement performance, as well as the limitations inherent within such estimates. Ensuring correct interpretation of the contents of this report by others is not the responsibility of GROUND. If any information referred to herein is not well understood, it is imperative that Colorado State University contact the author or a GROUND principal immediately. We will be available to meet to discuss the risks and remedial approaches presented in this report, as well as other potential approaches, upon request. CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Job No. 18-0057 Ground Engineering Consultants, Inc. Page 18 of 18 This report was prepared in accordance with generally accepted soil and foundation engineering practice in the project area at the date of preparation. Current applicable codes may contain criteria regarding performance of site improvements which may differ from those provided herein. Our office should be contacted regarding any apparent disparity. GROUND makes no warranties, either expressed or implied, as to the professional data, opinions or conclusions contained herein. Because of numerous considerations that are beyond GROUND’s control, the economic or technical performance of the project cannot be guaranteed in any respect. This document, together with the concepts and conclusions presented herein, as an instrument of service, is intended only for the specific purpose and client for which it was prepared. Re-use of, or improper reliance on this document without written authorization and adaption by GROUND Engineering Consultants, Inc., shall be without liability to GROUND Engineering Consultants, Inc. GROUND appreciates the opportunity to complete this portion of the project and welcomes the opportunity to provide Colorado State University with a proposal for construction observation and materials testing. Sincerely, GROUND Engineering Consultants, Inc. Joseph Zorack, P.E. Reviewed By Kelsey Van Bemmel, P.E. JOB NO.: CADFILE NAME: FIGURE: LEGEND AND NOTES 18-0057 0057LEG.DWG 4 LEGEND: Topsoil Sand and Clay: Sandy clay to clayey sand, fine to medium grained, medium plastic, stiff, moist to wet, brown to red-brown in color. Drive sample, 2-inch I.D. California liner sample Drive sample blow count, indicates 23 blows of a 140-pound hammer falling 30 inches were required to drive the sampler 12 inches. 23/12 Small disturbed sample NOTES: 1) Test holes were drilled on 1/4/19 and 1/14/19 with 4-inch diameter continuous flight augers. 2) Locations of the test holes were measured approximately by pacing from features shown on the site plan provided. 3) Elevations of the test holes were not measured and the logs of the test holes are drawn to depth. 4) The test hole locations and elevations should be considered accurate only to the degree implied by the method used. 5) The lines between materials shown on the test hole logs represent the approximate boundaries between material types and the transitions may be gradual. 6) Groundwater was not encountered during drilling. Ground water levels can fluctuate seasonally and in response to landscape irrigation. 7) The material descriptions on this legend are for general classification purposes only. See the full text of this report for descriptions of the site materials and related information. 8) All test holes were immediately backfilled upon completion of drilling, unless otherwise specified in this report. Fill:Sandy clay to clayey sand, fine to medium grained with some gravel, medium plastic, moist, and brown in color. Sample Location Natural Natural Percent Atterberg Limits Percent Water USCS AASHTO Test Moisture Dry Passing Liquid Plasticity Swell Soluble Classifi- Classifi- Soil or Hole Depth Content Density No. 200 Limit Index (Surcharge Sulfates cation cation Bedrock Type No. (feet) (%) (pcf) Sieve Pressure) (%) (GI) 2 3 12.4 112.4 35 25 14 (SC) A-2-4(1) Clayey Sand with gravel 4 5 6.7 114.2 76 26 7 (CL-ML)s A-4(4) Sandy Silt and Clay 6 5 19.6 107.0 80 37 20 0.1(200 psf) (CL)s A-6(13) Sandy Clay 8 3 15.4 108.2 75 27 15 0.03 (CL)s A-6(8) Sandy Clay SD = Sample Disturbed, NV = Non-Viscous, NP = Non-Plastic Job No. 18-0057 SUMMARY OF LABORATORY TEST RESULTS TABLE 1 Appendix A Pavement Thickness Calculations Page 1 1993 AASHTO Pavement Design DARWin Pavement Design and Analysis System A Proprietary AASHTOWare Computer Software Product Network Administrator Flexible Structural Design Module Lake Street Surface Parking Fort Collins, Colorado Moderate Duty Parking Lot EDLA 15 Flexible Structural Design 18-kip ESALs Over Initial Performance Period 109,500 Initial Serviceability 4.5 Terminal Serviceability 2 Reliability Level 80 % Overall Standard Deviation 0.44 Roadbed Soil Resilient Modulus 3,562 psi Stage Construction 1 Calculated Design Structural Number 2.83 in Specified Layer Design Layer Material Description Struct Coef. (Ai) Drain Coef. (Mi) Thickness (Di)(in) Width (ft) Calculated SN (in) 1 Hot Mix Asphalt 0.44 1 4.5 - 1.98 2 Aggregate Base Course 0.11 1 8 - 0.88 Total - - - 12.50 - 2.86 Page 1 1993 AASHTO Pavement Design DARWin Pavement Design and Analysis System A Proprietary AASHTOWare Computer Software Product Network Administrator Rigid Structural Design Module CSU: Lake Street Surface Parking Lot Fort Collins, Colorado Heavy Vehicle / Bus Drop Off Rigid Structural Design Pavement Type JPCP 18-kip ESALs Over Initial Performance Period 365,000 Initial Serviceability 4.5 Terminal Serviceability 2 28-day Mean PCC Modulus of Rupture 650 psi 28-day Mean Elastic Modulus of Slab 3,400,000 psi Mean Effective k-value 10 psi/in Reliability Level 80 % Overall Standard Deviation 0.34 Load Transfer Coefficient, J 3.4 Overall Drainage Coefficient, Cd 1 Calculated Design Thickness 6.26 in