6.3. SR 02-07-2005 - Laserfiche WebLink

Home Browse Search

I City of Elk River Project BN-04-06875 December 8, 2004 Page 4 I :1 the ADT and the percent trucks (any vehicle not a car or pickup). It is Oill understanding that there are likely no semi-trailers within the truck counts and that the trucks are likely comprised of a mixture of busses, delivery trucks and garbage trucks. Therefore, we have assumed that the distribution of vehicles using the streets will have a 20 year design equivalent single axle load (EASL) value on the order of 100,000. I II I It should be noted that utility reconstruction may be necessary prior to reconstructing the streets. Our borings were relatively shallow and not completed with the intent to explore soils at a depth sufficient to comment on that work; as such this report does not address utility construction. I If the proposed construction changes or if the proposed grades change, we should be informed. Additional analysis and revised recommendations may be necessary. I C.2. Evaluation of the Boring Data Based on the borings the soils encountered (both fill and natural) are considered generally suitable for subgrade soils, however, they are generally loose. To further eIihance subgrade strength and uniformity, we recommend surface compacting the exposed subgrade soils prior to placing any additional fill, or the new pavement section. We recommend buried organic soils, such as those encountered in Borings ST -8 and ST -9, be removed to at least 3 feet below the aggregate base of the new pavement. I 1 I 1 D. Recommendations I 'I D.l. Roadway Construction D.l.a. Subgrade Preparation. We recommend organic soils (having organic contents over 5 percent by weight) be removed to a depth of at least 3 feet below the bottom of aggregate base. Borings ST-8 and ST-9 contained soil that appeared to be organic. Since the sandy subgrade soils are typically loose, we also recommend that the upper 6 to 8 inches of the resulting subgrade be scarified, moisture-conditioned to a moisture content near optimum and recompacted to a minimum of 100 percent of its standard Proctor maximum dry density. If there are areas which cannot be compacted, we recommend that the unstable materials be subexcavated to a depth of2 feet and be replaced by materials which can be compacted. Where fill is required, we recommend that it also be moisture-conditioned and compacted to a minimum of 100 percent. I II I I I