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HomeMy WebLinkAboutPVH HEALTH SYSTEM, HARMONY CAMPUS, 2ND FILING, INFRASTRUCTURE - FDP - 32-98D - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTmin MAINTENANCE We recommend a preventive maintenance program be developed and followed for all pavement systems to assure the design life can be realized. Choosing to defer maintenance usually results in accelerated deterioration leading to higher future maintenance costs, and/or repair. A recommended maintenance program is outlined in Appendix C. LIMITATIONS Our borings were drilled to provide a reasonable estimation of subsurface conditions. Variations in the subsoil condition not indicated by our borings are likely. Pavement sections are preliminary and should be revised after the City of Fort Collins provides design traffic values. A representative of our firm should observe subgrade preparation, fill placement and pavement construction. We believe the geotechnical services for this project were performed in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing under similar conditions in the locality of the project. No warranty, express or implied, is made. If we can be of further service in discussing the contents of this report, or in the analyses of the proposed pavement systems from a geotechnical point of view, please call. �p0 REG�S� °• CTL I THOMPSON INC. O ••' D• Ts F o o•m � • � 36292 �:o J/ • Adam D. Tschida, PE 0 �.� �/`T��7"•�•�� Project Engineer S•''••••''•G� S/ � 0 AL Thomas A. Chapel, CPG, PE Associate & Division Manager ADT:TAC/bly (6 copies sent) POUDRE VALLEY HEALTH SYSTEM 11 INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 2. Cohesive soils (A-6 to A-7-6) should be moisture conditioned between optimum to 2% above optimum moisture content and compacted to at least 95% of maximum standard Proctor dry density (ASTM D 698, AASHTO T 99). 3. Granular soils (A-1 to A-5) should be moisture conditioned between 2% below to 2% above optimum moisture content and compacted to at least 95% of maximum standard Proctor dry density (ASTM D 698, AASHTO T 99). 4. Final grading of the subgrade should be carefully controlled so the design cross -slope is maintained and low spots in the subgrade that could trap water are eliminated. 5. Once final subgrade elevation has been reached and the subgrade compacted and inspected, the area should be proof -rolled with a pneumatic tired vehicle loaded to at least 18 kips per axle. The proof -roll should be performed while moisture contents of the subgrade are still within the recommended limits. Drying of the subgrade prior to proof -roll or paving should be avoided. Areas of soft or wet subgrade should be remedied. CONSTRUCTION DETAILS The design of a pavement system is as much a function of the quality of the paving materials and construction as the support characteristics of the subgrade. The construction materials are assumed to possess sufficient quality as reflected by the strength coefficients used in the flexible pavement design calculations. These strength coefficients were developed through research and experience to simulate expected material of good quality, as explained herein. During construction careful attention should be paid to the following details: ► Placement and compaction of trench backfill. ► Compaction at curb lines and around manholes and water valves. ► Excavation of completed pavements for utility construction and repair. ► Moisture treating or stabilization of the subgrade to reduce swell potential. ► Design slopes of the adjacent ground and pavement to rapidly remove water from the pavement surface. 10 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 �r 2. High calcium quicklime should conform to the requirements of ASTM C 977 and ASTM C 110. Dolomitic quicklime, magnesia quicklime with magnesium oxide contents in excess of 4 percent or carbonated quicklime should not be used. 3. Fly ash should consist of Class C or Class F. Class F fly ash should only be allowed in conjunction with lime or other stabilizing agents. 4. All stabilizing agents should come from the same source as used in the mix design. If the source is changed, a new mix design should be performed. 5. The subgrade should be mixed to the specified depth and at the specified concentration until a uniform blend of soil, stabilizing agent and water is obtained and the moisture content is at least 3 percent above the optimum moisture content of the design mixture. 6. If lime is used, a mellowing period of up to 7 days may be required following initial mixing. Once the pH of the mixture is 12.3 or higher and the plasticity index is less than 10, the soils shall again be mixed and moisture conditioned to at least 3 percent over optimum moisture content and compacted to at least 95 percent of maximum standard Proctor dry density (ASTM D 698). Up to 7 additional days may be required for curing prior to paving. The treated surface shall be kept moist or sealed with emulsified asphalt. Traffic should not be allowed on the surface during the mellowing and curing periods. 7. If fly ash is used, the mixture should be moisture conditioned to at least 3 percent over optimum moisture content and compacted to at least 95 percent of maximum standard Proctor dry density (ASTM D 698) within 90 minutes from the time of initial fly ash mixing. 8. If a lime/fly ash combination is used, the lime should be mixed first and allowed to mellow as indicated above. Following the mellowing period, the fly ash should be added, moisture conditioned and compacted as indicated above within 90 minutes of initial fly ash mixing. 9. Mixing of the lime or lime/fly ash treated subgrade should not occur if the temperature of the soil mixture is below 40°F. 10. Placement, mixing and compaction of stabilized subgrade should be observed and tested by a representative of our firm. Prepared Subgrade 1. Subgrade should be stripped of organic matter, scarified, moisture treated and compacted. POUDRE VALLEY HEALTH SYSTEM 9 INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 IF containing polymer modified asphalt. The breakdown compaction should be completed before the mixture temperature drops 20°F. 9. The maximum compacted lift should be 3.0 inches and joints should be staggered. No joints should be placed within wheel paths. 10. Asphalt concrete should be compacted to between 92 and 96 percent of Maximum Theoretical Density. The surface shall be sealed with a finish roller prior to the mix cooling to 185°F. ' 11. Placement and compaction of hot mix asphalt should be observed and tested by a representative of our firm. Placement should not commence until the subgrade is properly prepared (or stabilized), observed, and proof -rolled. Aggregate Base Course (ABC) 1. A Class 5 or 6 Colorado Department of Transportation (CDOT) specified aggregate base course should be used. A recycled concrete alternative, which meets the Class 5 or 6 designations, is also acceptable. 2. Aggregate base course should have a minimum Hveem stabilometer value of 77. Aggregate base course or recycled concrete material must be moisture stable. The change in R-value from 300 psi to 100 psi exudation pressure should be 12 points or less. 3. If used, geotextile fabric (Mirafi 500x or equivalent) should be placed over the approved subgrade within 24 hours prior to placement of aggregate base course or recycled concrete. Fabric should be rolled out longitudinally with minimum overlapped seams of 2.5 feet. No wrinkles should be permitted. 4. Aggregate base course or recycled base course should be placed in thin lifts not to exceed 8 inches, moisture treated to within 2% of optimum moisture content, and compacted to at least 95% of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99). 5. Placement and compaction of aggregate base course or recycled concrete should be observed and tested by a representative of our firm. Placement should not commence until the underlying subgrade is properly prepared and observed. Stabilized Subgrade (SS) 1. The contractor should have a mix design performed using the actual site soils and the approved stabilizing agent (lime, fly ash or a combination of lime and fly ash). Scheduling should allow at least 2 weeks for the mix design to be completed prior to construction. 8 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS - CTL I T JOB NO. FC-3176 IF for construction should be submitted and the applicable laboratory tests performed to verify compliance with the specifications. Asphaltic Concrete (AC) 1. Hot mix asphalt should be composed of a mixture of aggregate, filler, hydrated lime and asphalt cement. Some mixes may require polymer modified asphalt cement, or make use of reclaimed asphalt pavement (RAP). A iob mix design is recommended and periodic checks on the iob site should be made to verify compliance with specifications. 2. Hot mix asphalt should be relatively impermeable to moisture and should be designed with crushed aggregates that have a minimum of 80% of the aggregate retained on the No. 4 sieve with two mechanically fractured faces. 3. Gradations that approach the maximum density line (within 5% between the No. 4 and 50 sieve) should be avoided. A gradation with a nominal maximum size of 3/4 or 1/2 inches developed on the fine side of the maximum density line should be used. 4. Total void content, voids in the mineral aggregate (VMA) and voids filled should be considered in the selection of the optimum asphalt cement content. The optimum asphalt content should be selected at a total air void content of approximately 4%. The mixture should have a minimum VMA of 14% and between 65% and 80% of voids filled. 5. Asphalt cement should meet the requirements of the Superpave Performance Graded Binders (PG). The minimum performing asphalt cement should be PG 64-22 for use along the Front Range. The use of PG 58-28 or PG 58-22 asphalt cement has been known to cause tenderness in pavements in the Front Range area and should be avoided. 6. If used, hydrated lime should be added at the rate of 1% by dry weight of the aggregate and should be included in the amount passing the No. 200 sieve. Hydrated lime for aggregate pretreatment should conform to the requirements of ASTM C 207, Type N. 7. We recommend paving only be performed when subgrade temperatures are above 40OF and air temperature is at least 40OF and rising. 8. Hot mix asphalt should not be placed at a temperature lower than 245OF for mixes containing PG 64-22 asphalt, and 290°F for mixes POUDRE VALLEY HEALTH SYSTEM 7 INTERIOR ROADS PVH HARMONY CAMPUS - CTL I T JOB NO. FC-3176 IF least 95 percent of maximum standard Proctor dry density (ASTM D 698). Sand fill should be moistened to within 2 percent of optimum moisture content. Clay fill should be moisture condition to between 1 and 3 nercent above optimum moisture content. A representative of our firm should observe placement and test compaction of fill. PRELIMINARY PAVEMENT DESIGN At this time, the City of Fort Collins Engineering Department has not recommended design traffic values for these roads. For preliminary design, we assumed Snow Mesa Drive would be classified as a Commercial Collector with an Equivalent Single Axle Load (ESAL) of 730,000 and the other streets as Major Collectors with ESAL's of 365,000. A design R-value of 15 was used for the existing subgrade soil, based on the results of the previous investigation. PRELIMINARY PAVEMENT THICKNESS ALTERNATIVES * Subgrade with high swell potential should be treated to a minimum depth of 3 feet. PAVEMENT MATERIALS Material properties and construction criteria for the pavement alternatives are provided below. These criteria were developed from analysis of the field and laboratory data, our experience and City of Fort Collins requirements. If the materials cannot meet these recommendations, then the pavement design should be reevaluated based upon available materials. All materials and construction requirements of the City of Fort Collins should be followed. All materials planned POUDRE VALLEY HEALTH SYSTEM 6 INTERIOR ROADS PVH HARMONY CAMPUS , CTL I T JOB NO. FC-3176 IF section, which may consist of; full depth asphalt concrete, a composite section of asphalt concrete and aggregate base course, or asphalt concrete over chemically stabilized subgrade. The thickness of aggregate base course or chemically stabilized subgrade should be counted as part of the moisture treated depth. Moisture treatment of the subgrade is also recommended beneath curb and gutter and attached sidewalks. Moisture treated subgrade should be placed and compacted to the specifications in FILL PLACEMENT, below. EXCAVATION Excavation may be required. We believe the site soils can be excavated with conventional heavy-duty equipment. Based on Occupational Safety and Health Administration (OSHA) Standards covering temporary excavations, we believe the clay soils likely classify as Type B and sand soils as Type C. Type B soils require a maximum slope inclination of 1:1 (horizontal:vertical) and Type C soils require a maximum slope inclination of 1.5:1. Stockpile and vehicles should be set back a minimum distance equal to one-half the height of the slope from the crest of the excavation. The contractor's "competent person" should identify the soils encountered and refer to OSHA standards to determine appropriate methods to protect individuals working in excavations. Excavations deeper than 20 feet should be shored or designed by a professional engineer. FILL PLACEMENT Areas to receive fill should be prepared by scarifying the surface to a depth of 8 inches, moisture conditioning to within 2 percent of optimum moisture content for sand subgrade (1 to 3 percent above optimum moisture content for clay subgrade) and compacting to at least 95 percent of maximum standard Proctor dry density (ASTM D 698). On -site soils substantially free of debris, organics or other deleterious materials are suitable for re -use as fill. Imported fill should consist of soils with properties similar or better than the on -site soils. A sample of import material should be submitted to our office for approval prior to importing to the site. Fill should be moisture conditioned, placed in thin, loose lifts, and compacted to at POUDRE VALLEY HEALTH SYSTEM 5 INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 Ground Water Ground water was not encountered during drilling of the test holes. When we returned several days after drilling, ground water was measured in one boring (S-6) at a depth of about 13 feet. The other seven borings had caved at depths of about 10 to 13 feet and the caving may have been due to ground water infiltration in the borings. Ground water levels will vary seasonally and with changes in precipitation and irrigation amounts in the surrounding area. EXPANSIVE SOIL MITIGATION Expansive soils are present in the subgrade at this site. We measured swells of 0.5 to 11.6 percent after wetting under 150 psf loads during laboratory testing. The presence of expansive soils implies that pavements may heave and be damaged. The risks associated with swelling soils cannot be eliminated, but may be mitigated by careful design, construction and maintenance procedures. Two methods of mitigation can be considered; they are 1) removal and replacement and 2) moisture treatment. Treatment of the subgrade should extend beneath curb, gutter and attached sidewalks. Removal and Replacement The expansive subgrade soils can be removed to a depth of 36 inches below proposed subgrade elevation and replaced with a low permeability silty to clayey sand, which exhibits swell of less than 2 percent (under a 150 psf confining pressure) when compacted within 1 percent of optimum moisture content to 94 to 97 percent of maximum standard Proctor dry density (ASTM D 698). Permeability should be low in order to reduce the probability of creating a `bathtub' and driving the swell deeper by providing a constant source of moisture. We recommend a minimum R-value of 19 for the imported sand, which should be confirmed prior to placement. Moisture Treatment Based on our experience and local practice, we recommend at least 36 inches of moisture treated, on -site soils be placed below the designed pavement 4 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS ' CTL I T JOB NO. FC-3176 IF particle size analysis tests were performed on four samples and indicated liquid limits of 39 to 48 percent, plasticity indices of 12 to 18 percent and 55 to 73 percent silt and clay fines (passing the No. 200 sieve). The samples classified as A-6 and A-7-6 soils, according to the AASHTO classification system. Swell -consolidation testing of fourteen samples indicated swell of 0.5 to 11.6 percent swell. Twelve of the fourteen samples tested showed swell greater than 2 percent. Swell potential in this range requires mitigation according to City of Fort Collins specifications. Our recommendations for mitigation of the swelling soils are presented below in the EXPANSIVE SOIL MITIGATION section of this report. A Hveem Stabilometer test (R-Value, ASTM 2844, AASHTO T190) was performed on a combined sample from the previous investigation. The results indicated an R-Value of 15. Four samples were tested for water-soluble sulfate content and indicated 0.002 to 0.012 percent water-soluble sulfates. These low values indicate the risk of heave due to chemical reaction between sulfate and a stabilizing agent is low. Sulfate concentrations above 0.5 percent can cause an adverse reaction between the sulfates and the stabilizing agent, resulting in heaving of the subgrade if lime or fly ash stabilization is performed. This result also indicates class 0 exposure to concrete in contact with site soils, according to the criteria of the American Concrete Institute (ACI). For this level of sulfate concentration, ACI indicates any type of cement can be used for concrete that comes into contact with the subsoils. In our experience, superficial damage may occur to the exposed surfaces of highly permeable concrete, even though sulfate levels are relatively low. To control this risk and to resist freeze -thaw deterioration, the water-to-cementitious material ratio should not exceed 0.50 for concrete in contact with soils that are likely to stay moist due to surface drainage or high water tables. Concrete should be air entrained. 3 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 PREVIOUS INVESTIGATION CTL I Thompson, Inc conducted an investigation for the Poudre Valley Health System, Harmony Campus Medical Center (Job No. FC-1116) that included field and laboratory testing along the alignment of the roads. Data and findings from the previous investigation were considered during preparation of this report. Summary logs of borings for the previous investigation are provided in Appendix B. FIELD AND LABORATORY INVESTIGATION Our field investigation consisted of drilling eight borings to a depth of 15 feet along the alignment of the roads. The boring locations were staked by Stantec. The approximate locations of our borings are shown on Figure 1. Our representative observed drilling operations, logged the soils encountered and obtained samples. Bulk samples were obtained from auger cuttings in the upper five feet of each boring. Relatively undisturbed samples were obtained at depths of 2, 4, 9, and 14 feet by driving a modified California sampler with a 140-pound hammer failing 30 inches. Summary logs of the borings are presented on Figure 2. Laboratory testing was performed in general accordance with AASHTO and ASTM methods to determine index properties of the soils sampled and subgrade support values for those soil types influencing the pavement design. To evaluate potential heave, swell -consolidation testing was performed on 14 samples of the clay under a pressure of 150 psf. Results of laboratory tests are presented in Appendix A and are summarized on Table A -I. SUBSURFACE CONDITIONS The soils encountered in our borings were predominately medium stiff to very stiff sandy clay. Clayey sand was encountered in three borings, at depths of 6 to 14 feet below the ground surface. We tested samples of the soils in the laboratory for density, moisture, swell/consolidation properties, water-soluble sulfate concentration, and subgrade support characteristics. Atterberg limits and 2 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC•3176 Rim SCOPE This report presents the results of our geotechnical investigation for the proposed interior roads within the Poudre Valley Health System, Harmony Campus, located southeast of the intersection of Timberline and Harmony Roads in Fort Collins, Colorado (Figure 1). The purpose of this investigation was to obtain information regarding subsurface conditions within the alignment of the proposed streets. The report presents geotechnical design and construction criteria for the roadways in general conformance with the Larimer County Urban Area Street Standards as adopted by the City of Fort Collins. Our report includes descriptions of the subsoils found in our exploratory borings, laboratory test results, preliminary pavement sections, and construction and materials guidelines. The recommendations contained herein are based upon laboratory test results, Larimer County Urban Area Street Standards, the AASHTO design method, and our experience. SITE CONDTIONS The site is located south and east of the Poudre Valley Health Center, located southeast of the intersection of Timberline and Harmony Roads in Fort Collins, Colorado (Figure 1). Currently, the site is a vacant field covered in grasses and vegetation. Underground sanitary sewer is installed along the alignment of the proposed unnamed road that loops around the south side of the hospital, and underground water and sewer are present along the alignment of Snow Mesa Road. PROJECT DESCRIPTION The project site consists of approximately 5200 feet of roadway to the south and east of the existing Poudre Valley Health System Facility (Figure 1). The streets consist of two unnamed roads, extension of Snow Mesa Drive from the south edge of the site to Harmony Road and extension of Timberwood Drive from the east edge of the property to proposed Snow Mesa Drive. Curb and gutter and a detached sidewalk are planned. 1 POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS CTL I T JOB NO. FC-3176 TABLE OF CONTENTS SCOPE 1 SITE 1 PROJECT DESCRIPTION 1 FIELD AND LABORATORY INVESTIGATION 1 PREVIOUS INVESTIGATION 2 FIELD AND LABORATORY INVESTIGATION 2 SUBSURFACE CONDITIONS 2 Groundwater 4 EXPANSIVE SOIL MITIGATION 4 Removal and Replacement 4 Moisture Treatment 4 EXCAVATION 5 FILL PLACEMENT 5 PRELIMINARY PAVEMENT DESIGN 6 PAVEMENT MATERIALS 6 Asphaltic Concrete 7 Aggregate Base Course 8 Stabilized Subgrade 6 Prepared Subgrade 9 CONSTRUCTION DETAILS 10 MAINTENANCE 11 LIMITATIONS 11 FIGURE 1 - LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 - SUMMARY LOGS OF EXPLORATORY BORINGS APPENDIX A - LABORATORY TEST RESULTS APPENDIX B — SUMMARY LOGS OF EXPLORATORY BORINGS - JOB NO. FC-1116 APPENDIX C - MATERIAL PROPERTIES AND CONSTRUCTION CHECKLIST POUDRE VALLEY HEALTH SYSTEM INTERIOR ROADS PVH HARMONY CAMPUS ' CTL I T JOB NO. FC-3176 IEEI I N C O R P O R A T E U SUBGRADE INVESTIGATION AND PRELIMINARY PAVEMENT DESIGN INTERIOR ROADS POUDRE VALLEY HEALTH SYSTEM HARMONY CAMPUS FORT COLLINS, COLORADO Prepared For: POUDRE VALLEY HEALTH SYSTEM SYSTEM DEVELOPMENT 2809 East Harmony Road Suite 200 Fort Collins, Colorado 80528 Attention: Ms. Arleen Richardson Job No. FC-3176 June 5, 2004 375 E. Horsetooth Road I The Shores Office Park I Building 3, Suite 100 1 Ft. Collins, Colorado 80525 Telephone:970-206-9455 Fax:970-206-9441