Thanks Bill. The Corps approved the use of RCP and even CMU blocks, so the crisis is adverted. Clay Barnett, P.E. Town Engineer Town of Addison 16801 Westgrove Drive Addison, TX 75001-2818 Office: (972) 450-2857 From: Bill Campbell [mailto:OWCampbell@kleinfelder.com] Sent: Wednesday, January 26, 2011 1:39 PM To: Clay Barnett Subject: rock from the DFW area Clay- Thanks for your question earlier today concerning using rock excavated from the project site as an architectural element on the project. Unfortunately, the Austin Chalk limestone that we have here in the DFW area is not a hard limestone. If you were to use it as an architectural element that is exposed to the environment, it would erode relatively quickly. The hardest material that we find in the DFW area is some of the cemented sandstone boulders that are part of the Woodbine formation. This formation stretches from Frisco down to Mansfield in a north-south orientation. These boulders are infrequent and I am not aware of a ready source of them. The hard limestone in this area comes from the Chico/Bridgeport area north and west of the DFW metroplex. This is evidenced by the fact that most of the crushed limestone base material and aggregate for pipe bedding, concrete aggregate and asphalt aggregate come from that area. There are no pits in the DFW area that mine the Austin Chalk limestone for those purposes, because it is not of sufficient quality to meet the requirements of those materials. Those same requirements (strength, abrasion resistance, soundness, density, etc.) are the types of characteristics that you would want for your architectural element boulders. Please let me know if you have any other questions.