Analyses were completed for only the flexible (AC) and rigid (PCC) pavement <br />sections. We have assumed analyses for the Grasscrete will be completed by <br />others. The pavement analyses were completed based on design recommendations <br />provided in the City of Eugene Public Improvements Design Standards Manual <br />(November 2011). The exception is the design life for the parking areas is <br />20 years. The ODOT Pavement Design Manual (2011) was also used. <br />An estimate of daily traffic was not available. However, the available site plan <br />shows the proposed parking area location and 38 new parking stalls. For <br />pavement design, we assumed a daily turnover rate of 5 vehicles per stall <br />(equivalent to a daily traffic of 190 cars and light pickup trucks, and 4 trucks (2 to <br />3-axle vehicles)). Truck traffic includes daily or weekly trips by delivery trucks, <br />moving vans/trucks and garbage trucks. Using this assumed traffic data and <br />ODOT (2011) Equivalent Single Axle Load (ESAL) conversion factors, we estimated <br />± 10,730 ESALs for a 20-year design life. <br />The pavement subgrade is expected to consist primarily of medium plasticity silty <br />clay. A subgrade Mr value of 3,250 Ib/in2 (psi) was assumed for design based on <br />the average DCP test results. Using the assumed traffic, City design criteria and <br />the subgrade modulus, we calculated a flexible pavement section consisting of <br />3 inches of AC over 12 inches of base rock underlain by a separation geotextile. <br />The base rock thickness should be increased to 24 inches if the subgrade cannot be <br />compacted or if the pavement base is to support construction traffic during wet <br />weather. <br />The City minimum PCC thickness of 6 inches is recommended for the PCC sections <br />as described above. The PCC should be supported on a minimum of 6 inches of <br />base rock underlain by a separation geotextile. Provide an additional subbase of <br />12 inches of Granular Site Fill or Select Fill if the subgrade cannot be compacted or <br />if the pavement is to support construction traffic during wet weather. <br />The recommended flexible and rigid pavement sections are for the assumed <br />build-out traffic and do not include construction traffic. Refinement of the traffic <br />estimates and other design assumptions may be required following design 'team <br />review of this report. A Separation Geotextile is recommended beneath the base <br />rock regardless of the time of year the pavement areas are built. <br />RECOMMENDATIONS <br />We understand the earthwork will begin in the spring of 2014. Therefore, <br />recommendations are provided for wet weather construction. Compaction of the <br />subgrade under the building pads or pavement areas will not be practical when the <br />soils are wet. Therefore, construction during wet weather will require the use of <br />granular site-fill and will require site preparation techniques that reduce the risk of <br />subgrade pumping (e.g., increased granular fill and base rock thickness). The <br />contractor may still experience pumping problems in the summer if the surf icial soils <br />have not adequately dried. Therefore, we recommend an on-site conference with <br />the contractor prior to the grading work to review site conditions. <br />Oakleigh Meadows Cohousing February 12, 2013 <br />Geotechnical Investigation Project 2131004 1451 <br />Eugene, Oregon 6. Willard C. Dixon Architect, LLC <br />