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2006 PMP Update . 1/18/2007 Page 2 becoming brittle and cracking, and also helps keep the water from seeping through the pavement and causing prohkms to the base material. Mill and Overlay There are several maintenance practices that imoh'c milling. :\n edge mill typically consists of grinding the old bituminous surl:lce along the ollter X fed (If the street. This helps establish a unifcmn cross-section, especially in instances where the crown in the street is relatively flat. A .Iidl u.idth mill. or resurt:lcing. is necessary when the upper surt:lce layer of a pavement has deteriorated considerably. Significant surbce pan:ment distresses and more extensive "thenllal"' cracking need to be removed and/or repaired with a full width and unitl:mn depth milling process. Both edge mills and full-width mills arc typically 1.5 to :2 inches thick. hut can vary on a project by project basis. Milling neates an even surface to ensure a llnitl.lrm ()\'erall thickness hI the new overlay. An asphalt overlay of 1.5 to :2 inches over the l'ntire paveml~nt width t(mllS a smooth crown. renews the street surf:Jce. restores structural capacity and proper drain;lge, and extends the lite cycle of the original pavement. Afitll depth mill can be llsed on a street that has already been reconstructed with a good base . section, but the pavement has deteriorated to a point where seal coating or a standard mill and overlay is not effective. A pavement section with significant nacking will end up reflecting through the new pavement. The full depth of the pavement is ground up and removed. This process may also involve some subgradt: soj] corrections and some removal of aggregate base. jf it has been contaminated or is sub-standan1. The strecl is paved with the same thickness of new asphalt. Pavement can also be reclaimed, \\lherc approximately ~ to I () inchcs ofthc existing asphalt and hase are ground up in place. This 1()fIns a ne\\! more stabk hasc without adding new material. Thc road is then paved with new asphalt. This is only n:commcndcd whcre thcre is no curb and gutter on the road, since the existing materials stay in placc and a higher road elevation is created oncc the new pavement thickness is added. Reconstruction When a strcct is fully rcconstructed. the cxisting asphalt and base arc completely removed and replaced. Reconstmction may also involve subgrade soil corrections. For streets that do not meet currcnt design standards for wiLlth, curn and gutter. and drainage. an upgrade may also be incorporated. .