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HomeMy WebLinkAboutINTERSTATE LAND PUD FIRST FILING HARLEY DAVIDSON - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -June 25, 1996 R. C. Heath Construction Company P. O. Drawer H Fort Collins, Colorado 80522 Attn: Mr. Randy DeMario lrerrac®n CONSULTANTS WESTERN, INC. EMPIRE DIVISION P.O. Box 503 • 301 N. Howes Fort Collins, Colorado 80522 970) 484-0359 Fax (970) 484-0454 Larry G. O'Dell, P.E. Neil R. Sherrod, C.P.G. Re Addendum to Geotechnical Engineering Report - Pavement Design Recommendations Proposed Harley Davidson Dealership 1-25 Frontage Road North of Prospect Road East Fort Collins, Colorado Project No. 20955168 Gentlemen: This letter serves as an addendum to our geotechnical engineering report for the referenced project dated October 11, 1995. The purpose of this addendum is to provide recommended pavement types and thicknesses for overlaying and widening the frontage road at the proposed Harley Davidson dealership. Our recommendations are based on recently received traffic data from the City of Fort Collins. The project as we understand it is to overlay and widen approximately 1,000 linear feet of the existing frontage road along the south and east sides of the proposed Harley Davidson dealership. The roadway will be widened approximately 10 feet. Three test borings were drilled on June 6, 1996 to depths of 10 feet at the locations shown on the Site Plan, Figure 1. The borings were drilled approximately 5 to 8 feet off the existing pavement and were advanced with a truck -mounted drilling rig utilizing a 4-inch diameter solid stem auger. The borings were located in the field by pacing from the Harley Davidson property. The borings were checked for groundwater at the time of the site exploration and 7 days after drilling. Boring logs were prepared and are presented with this addendum. Selected soil samples were tested for moisture content, Atterberg limits and Hveem stabilometer characteristics. Laboratory test results are presented with this addendum and were used for the geotechnical engineering analyses and the development of pavement recommendations. All laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards. The existing 1-25 frontage road extends around the south and east sides of the proposed Harley Davidson property. The pavement is in good condition. The road exhibits fair surface drainage toward ditches on both sides of the pavement. The areas of proposed widening are vegetated with dense grass and weeds. The following describes the characteristics of the primary soil strata encountered in the test borings in order of increasing depths. Offices of The Terracon Companies, Inc. Geotachnical, Environmental and Materials Engineers Arizona Arkansas Colorado Idaho Illinois Iowa E Kansas 9 Minnesota Missouri Montana Nebraska Nevada M Oklahoma Texas Utah ® Wyoming QUALITY ENGINEERING SINCE 1965 Terracon R. C. Heath Construction Project No. 20965168 M: Fill was encountered at the surface of the test borings and extends to depths of 1 to 3 feet. The fill consists of moist sandy lean clay, silty sand and/or clayey sand with varying quantities of gravel. It is not known whether the fill has been uniformly or properly compacted. Sandy Lean Clay: Natural sandy lean clay was encountered below the fill and extends to any underlying granular stratum or to the depths explored. The lean clay is moist and contains substantial quantities of sand. e Silty Sand with Gravel: The granular stratum was encountered in Boring 3P at a depth of 9 feet and extends to the depth explored. The sand is wet and contains substantial quantities of silt and moderate quantities of gravel. Field test results indicate the natural clay soil is generally soft but varies from very soft to medium stiff in consistency. The sand encountered in Boring 3P is medium dense in relative density. Laboratory test results indicate the upper clay soils are moderately plastic. Groundwater was encountered in Boring 3P at depths of 9.1 and 9.3 feet at the time of the site exploration and 7 days after drilling, respectively. Groundwater was not encountered in Borings 1 P and 2 at these times. Pavement Design and Construction Design of pavements for the project have been based on the procedures outlined in the 1986 Guideline for Design of Pavement Structures by the American Association of State Highway and Transportation Officials (AASHTO). Traffic criteria provided by the City of Fort Collins for pavement thickness designs include an equivalent 18-kip single axle load (ESAL) of 120. According to RBD, Inc., 2 feet of subbase directly below the existing pavement has an R-value of 74. For flexible pavement design, a terminal serviceability index of 2.5 was utilized along with an inherent reliability of 90%, a design life of 20 years and a design drainage coefficient of 1.0. Design R values of 74 and 7 were used for overlay and widening pavement section designs, respectively. The structural numbers (SN) of the pavement sections were determined on the basis of the aforementioned. values and the 1986 AASHTO design equation. In addition to the flexible pavement design analyses, a rigid pavement design analysis was completed for the proposed widened sections, 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 2 Terracon R. C. Heath Construction Project No. 20965168 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 thickness for the proposed widened section was determined on the basis of the AASHTO design equation. Recommended alternatives for flexible and rigid pavements, summarized for each traffic area, are as follows: 1"rst'iiC1a`:: tea Retrltn+lel Pav an er tBrfCtion ttt kt es (trhee) natlVe Asphalt r 1e Meet I t ced POrtlan(i i'otal Co rete Subbase Biftrmincwus Gerneant 6urtce Goiate Sass 'acrete Proposed A 6 12 18 Widened Sections B 4 6% 101/ C 8 8 Overlay A 2 2 Additional recommendations for pavement subgrade preparation and pavement construction are included in the "Pavement" and "Earthwork" sections of the geotechnical engineering report. If you have any questions concerning this addendum or if we can be of further service to you on this or future projects, please contact us. Sincerely, TERRACON CONSULTANTS Empire Division QlslaR. Schoenfeld, P.E. Geotechnical Engineer Copies to: SCHoFiy','P 23702 ? Q : .° S N A// J/111111.1tU Haaressee li RBD, Inc. - Mr. Bill Taylor (1) City of Fort Collins (2) CityScape Urban Design Inc. - Mr 0G o Reviewed by: rM f? n i illiam J. Attw00% P Office Manager 0 o -4 4,4S,' Yyy yry pn •R y 9 Terence Hoaglund (1)