Res. #15-036 - Approving Plans & Specs. & Ordering Ad. For Bids

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City of Centerville Project SP-07-03738 November 29,2007 Page 10 We recommend that material selected for granular subbase conform to Mn/DOT Specification 3149.2B2 for Select Granular Borrow,sand having no more than 12 percent of the particles by weight passing the ##200 sieve D.3. Placement and Compaction of Backfill and Fill We recommend spreading backfill and fill in 4-to 8-inch lifts,depending on the composition of the material and the type of compactor(s)used. The relative compaction of the backfill and fill should meet or exceed the recommended values presented below in Table 4. The recommended values are percentages of the materials' standard Proctor dry density(ASTM D 698). Table 4. Compaction Recommendations Summary Moisture Content Variance from Optimum, percentage points Relative Compaction, percent Soil containing no Soil containing more (ASTM D 698— more than 12 percent than 12 percent Reference standard Proctor) passing the#200 sieve passing the#200 sieve Below pavements,within 3 feet of subgrade elevations 100 -3 to+3 -1 to+3 Below pavements,more than 3 feet below subgrade elevations 95 -3 to+3 -I to+3 Below landscaped surfaces 90 NA NA D.4. Pavements DA.a. Subgrade Proofroll After the subgrade has been prepared as previously recommended,we recommend test-rolling it to check for localized soft areas,. Loose,soft or unstable areas observed will require additional stabilization, compaction and/or subexcavation of those materials. We recommend that the gest-rolling procedure be observed by a geotechnical engineer to assist in evaluating the suitability of'the pavement subgrade. A proofroll should be performed just prior to placement of the geotextile and again just prior to placement of the pavement. DA.b. Geotextile We recommend installing geotextile in accordance with Mn/DOT Specification 3733B Type V-