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� �d.. �dk <br />December 23,2004 <br />Memo to: File <br />From: Scott Spisak <br />Re: Dust Prevention and Control for Pavement Recycling <br />and Concrete Batching Staging Areas <br />For more than 15 years Shafer Contracting Co., Inc. has performed Recycle Pavement <br />Crushing and Concrete Batching Operations throughout the urban, metropolitan Twin <br />Cities area. <br />We take seriously the matter of dust prevention and control and use several different <br />methods to achieve it. <br />Dust results from handling or operating on materials that have a high percentage of their <br />contentpassing a#20� (200 openingsper square inch) sieve (ASTM C 13�. <br />Particularly troublesome materials on construction sites are silts and clays that consist of <br />50°/o or more material passing the #200 sieve. Sand (select granular material) has less <br />that 12°/o material passing the #204 sieve and is typically less troublesome. Neither of <br />these materials are involved in the production of recycle aggregate base or concrete <br />paving materials. <br />Recycled aggregate base material has a content passing the #20� sieve ranging from 3 to <br />7%. In addition, the frac#ured concrete particles tend to F�tm a ctust once they are <br />stockpiled. This crust minimizes the amount of dust that would typically be generated on <br />a similar pile of non-recycled aggregate base. <br />Aggregates used in batching concrete pavement are all washed during their production <br />and contain less than 1°/o of material passing the #�UO sieve. They typically do not <br />generate dust. <br />Both operations employ the use of truck applied water in areas of vehiculartraffic to <br />control and prevent fugitive dust. In addition, commercially available dust palliatives are <br />applied on some occasions to supplementthe use ofwater. <br />