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HomeMy WebLinkAbout15_Master Site Plan - Geotech_Addendum.pdf RIMROCK ENGINEERING, INC. Phone 406.294.8400 5440 Holiday Avenue • Billings, MT 59101 Fax 406.294,8405 July 7, 2010 Big Sky Land Consulting. PLLC 5530 Burnt Road Belgrade, MT 59714 Attentions Mr Tom Henesh SUBJECT: Addendum to the Geotechnical Investigation Report Billion Auto Plaza Three Auto Dealerships Bozeman, Montana Dear Mr. Henesh. On July 1. 2010, Rimrock Engineering completed the geotechnical investigation for the Billion Auto Plaza. At the time we were not aware that a traffic study for the J&D Family Subdivision had been completed by Abelin Traffic Services This addendum is to update the pavement sections to comply with the traffic study and the City of Bozeman minimum requirements. The pavement sections shown below replace the sections in our report The recommended pavement structural sections for the project presented in Table 2 were calculated using the AASHTO pavement design procedure. We are providing a heavy duty pavement section for Automotive Avenue and areas which will have heavy truck traffic and a light duty section for parking areas. In our analysis for the heavy duty pavement section. we used an ADT of 3814 vehicles per day with 2% truck traffic for the heavy duty section which results in a traffic loading condition of 502.485 18-kip equivalent single axle load (18-kip ESAL). For the light duty pavement section we assumed a loading of 75,000 ESAL's for the 20 design lifetime of the pavement. A CBR value of 5 7 was used for design of the pavement sections. Due to the high groundwater elevations. we have adjusted the drainage -factors on the base course and subbase layers. Rimrock Engineering was also requested to provide a concrete pavement section for some areas which may have automobiles parked for significant time periods This section is also shown in Table 2 and should be incorporated into our original report 07-115-03 Page 1 of 2 July 7, 2010 Rimrock Engineering, Inc TABLE 2 PAVEMENT STRUCTURAL SECTIONS Traffic Condition Recommended Minimum Structural Section* Light Duty Pavement Section 3 inches Asphaltic Concrete, 6-inches of 1-1/2 inch Crushed Base Course and 8 inches of 6" minus subbase Heavy Duty Pavement Section 4 inches of Asphaltic Concrete, 6-inches of Crushed Base Course and 10 inches of 6" minus subbase Light Duty Portland Cement 5 inches of Portland Cement Concrete, 4 inches of 1-1/2 inch Concrete Section Crushed Base Course and 8 inches of 6" Minus Subbase Aggregate base course thickness may be reduced in each pavement structural section by approximately 20% with the use of a recommended geotextile fabric This addendum and other conclusions and recommendations, along with restrictions and limitations in the original report should be followed We appreciate this opportunity to be of service to you, and look forward to future endeavors. If you have any questions regarding this report or need additional information or services, please feel free to call the undersigned. Sincerely. RIMROCK ENGINEERING, INC. Robert W. Kukes, P.E. Principal 07-115-03 Page 1 of 2 July 7, 2010 Rimrock Engineering, Inc