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December 23, 2004 Memo to: File From: Scott Spisak Re: Dust Prevention and Control for Pavement Recycling and Concrete Batching Staging Areas For more than 15 years Shafer Contracting Co., Inc. has performed Recycle Pavement Crushing and Concrete Batching Operations throughout the urban, metropolitan Twin Cities area. We take seriously the matter of dust prevention and control and use several different methods to achieve it. Dust results from handling or operating on materials that have a high percentage of their content passing a #200 (200 openings per square inch) sieve (ASTM C 136). Particularly troublesome materials on construction sites are silts and clays that consist of 50% or more material passing the #200 sieve, Sand (select granular material) has less that 12% material passing the #200 sieve and is typically less troublesome. Neither of these materials are involved in the production of recycle aggregate base or concrete paving materials. Recycled aggregate base material has a content passing the #200 sieve ranging from 3 to 7%. In addition, the fractured concrete particles tend to form a crust once they are stockpiled. This crust minimizes the amount of dust that would typically be generated on a similar pile of non-recycled aggregate base. Aggregates used in batching concrete pavement are all washed during their production and contain less than 1 % of material passing the #200 sieve. They typically do not generate dust. Both operations employ the use of truck applied water in areas of vehicular traffic to control and prevent fugitive dust. In addition, commercially available dust palliatives are applied on some occasions to supplement the use of water.