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Geotechnical Engineering and Geological Hazard Studv Lincoln Elementary School Modemization Project Manteca, Cali£omia Page 15 Pa`v'%aaaeaat sect: tiffs untreated subgrade soils are presented below based on the Caltrans minimum R -value of 50, current Caltrans design procedures, and four traffic index (T.1.) values for traffic loading (T.I. = 4.0, 5.0, 6.0 and 7.0). The traffic index (TI) is a measure of traffic wheel loading frequency and intensity of anticipated traffic. For comparison, Ti's of between 4 and 5 are often suitable for design of automobile parking areas, whereas TI's of between 5 and 6 are commonly used for design of fire truck access lanes and areas subject to channelized flow with light delivery trucks. Traffic lanes that regularly carry bus traffic and fire lanes should be designed for higher TI values based on specific conditions. Traffic indices assumed above should be reviewed by the project Owner, Architect, and/or Civil Engineer to evaluate their suitability for this project. Pavement sections for other traffic loading should be designed on a case-by-case basis. The use of rigid concrete pavement is favored where trash pick-up or truck traffic necessitates short radius maneuvering and/or heavy metal bin movement on rollers. RECOMMENDED UNTREATED SUBGIIADE PAVEMENT SECTIONS The above sections have been developed based on an R -value of 50 for untreated subgrade. The pavement sections provided above are contingent on the following recommendations being implemented during and following construction. • The subgrade soils in the upper 12 inches below the finished subgrade elevation should be compacted native subgrade soil compacted to achieve a minimum relative compaction of 95 percent of the CAL 216 maximum wet density. • All trench backfill for culverts, utilities and pipes underlying paved areas should be properly placed and compacted to at least 90 percent relative compaction (ASTM D i 557) within I foot of finished subgrade elevation. The upper 12 inches of trench backfill should be compacted to at least 95 percent relative compaction (CAL 216). • The subgrade soils should be in a stable, non -pumping condition at the time the aggregate base material is placed and compacted. • Aggregate base and aggregate subbase materials should conform to the specifications stated in Section 25 and 26 of the current Caltrans specifications and be compacted as engineered fill to at least 95 percent relative compaction. • AsphaIt paving materials and placement methods should meet current Caltrans specifications for asphalt concrete. • Adequate drainage (both surface and subsurface) should be provided such that the subgrade soils and aggregate base materials are not allowed to become continuously wet. Caltrans design procedures for asphalt concrete pavements provide sections in units of inches, rounded up to the nearest 1,2 -inch. Sections provided above include no Gravel Equivalent Safety Factor (per County Engineers Association and the League of California Cities criteria). If required a Gravel Equivalent Safety Factor is required, the pavement sections should be reevaluated W i CONDOR