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7.1.H. - Page 35 Exhibit C <br /> 1 l €, <br /> I <br /> - - .., 44,3 €1 0 . ,1 i . <br /> a <br /> Figure 6.Mechanical sweeper bristle penetration of larger gaps associated with CGP filled with sand(left)is possible,but <br /> pavement types with small gaps(such as PICP)is not(right,courtesy of Elgin Street Sweepers). <br /> ALL n sediment at their sidered insufficient for this restorative measure. <br /> . ' surface.The thin Clogging depth of pervious asphalt and pervious <br /> "r4.., .< clogged zone is concrete depends upon the contributing sediment load. <br /> � � .° " - named'`schmutz- Research has shown that sand collected on a pervious <br /> _ri`-i. ''.°� decke"from the concrete pavement will not penetrate the pavement more <br /> .f, '. , '. -, ; German word for than an inch deep.Although pervious asphalt was not <br /> "` `" '',.,On Nk .x:; dirt cover or ceiling. tested, it is assumed it would function similarly. How- <br /> The thickness of the ever,when a fine fraction of soil (silts or clays)was a <br /> .. schmutzdecke for part of the clogging sediment, the clogged zone was <br /> CGP ranges from much deeper, often at or near the bottom of the pervious <br /> • -`- 0.25 to 0.50 inches concrete section (Mata 2005). Restorative maintenance <br /> (James and Gen-its of a PA or PC system clogged by fines has not yet been <br /> r o. 2003, Bean et al. deemed possible. However, preventative maintenance, <br /> m r .4 2007).As the gaps by way of a regenerative air street sweeper, has proven <br /> - ._ , w•6 ) gp Y Y g p <br /> ,, � associated with CGP to be an adequate measure and keeps PA and PC slai- <br /> n are the largest of all faces infiltrating rainfall and run-on. <br /> ' ,1:. permeable pavement Table 1 summarizes the clogging depth of vari- <br /> Figure 7.The clogged zone of PICP is types, CGP is the ous types of permeable pavements and the appropriate <br /> evident toward the top portion of the easiest to maintain vehicle for prevention or restoration. Obviously,the <br /> interlocking paver.The depth of clog- with a mechanical simplest pavement type to either maintain or restore <br /> ging at this location outside Chicago, sweeper. By basic is concrete grid pavers filled with sand.All pave- <br /> IL,after 6 years of neglect was 1.5 geometry,the ability ment types can remain clog-free if preventive sweeper <br /> inches(40mm). <br /> of bristles to pen- maintenance is reliably provided. If pavements are <br /> etrate a large gap to a deeper depth benefits CGP(Figure neglected and allowed to clog to sometimes substantial <br /> 6). Research has shown that a standard mechanical depths, it is uncertain whether all pavements'neces- <br /> street sweeper can sufficiently penetrate the sand-filled sary surface infiltration rates can be restored.Also <br /> gaps of CGP to break apart the schmutzdecke. important to note, other than for CGP filled with sand, <br /> Dust and sediment will penetrate PICP filled with different street sweeper types are used for either pre- <br /> gravel to a much deeper level than that of CGP filled with ventive or restorative maintenance. <br /> sand. Field observation at a lot outside Chicago found Importance of Underlying Soil Type <br /> that a 6-year-old PICP lot that had never been main- <br /> tained had become clogged to a depth of 1.5 to 2.0 inches Bean et aI.(2007)showed that even when maintenance <br /> (Figure 7). Removing a schmutzdecke of this thickness (street sweeping)has been neglected for up to 20 years, <br /> is clearly beyond the ability of a standard mechanical permeable pavements can still be permeable,provided the <br /> sweeper. In fact,regenerative air street sweepers are con- underlying soils are permeable. Several tests of rela- <br /> Maintaining Permeable Pavements 5 <br />