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<br />I . <br /> <br />'. <br /> <br />2335 Highway 36 W <br />5t. Paul. MN 55113 <br /> <br />Tel 651-636-4600 <br />Fax 651-636-1311 <br /> <br />www.bonestroo.com <br /> <br />May 27, 2009 <br /> <br />#' Bonestroo <br /> <br />Mr. Dallas Larson <br />City Administrator <br />City of CentelVille <br />1880 Main Street <br />CentelVille, MN 55038 <br /> <br />Re: Peltier Lake Drive Area Street & Utility Improvements <br />City of CentelVille <br />Client Project No.: 2009.001 <br />8onestroo File No.: 000616-09169-0 <br /> <br />Dear Dallas: <br /> <br />The letter summarizes the circumstances surrounding proposed Change Order #3. <br /> <br />There are three subparts to Change Order #3. They are all related to subsurface conditions <br />encountered near the DNR wetland along the south side of Peltier Lake Drive. These conditions <br />were not Identified by the soil boring taken In this area. While the boring did Indicate the <br />presence of some organic material, It was only Identified in the top four feet of the existing <br />ground. <br /> <br />SU~Dart 1 - Muck Ey~vatlon and Liahtweiaht Badcfill <br />Unsuitable material (peat) has been discovered during the excavation for the water main <br />installation. In some areas, this material is only a few feet deep, but In other areas, it runs <br />deeper than the excavation necessary for the water main installation with no apparent bottom. <br />Aft:er consulting with American Engineering Testing, your solis engineer on the project, we have <br />come to a recommended course of action. This involves removal of all peat down to the top of <br />the new water main pipe. Normally, we would backfill with sand, but given the fact that the peat <br />continues, in some areas lower than the pipe, we need to backfill with lightweight material (wood <br />chips) to mimic the weight of the peat removed. Backfilling with sand could cause consolidation <br />(settling) of the peat below. This would cause problems for both the water and sewer mains as <br />well as the roadway. <br /> <br />We have attached a sketch of a two typical cross sections showing the plan of action. The cost <br />estimate attached to this letter assumes the worst case scenario of up to four feet of wood chip <br />fill. A letter from the contractor Is also attached detailing his pricing of the work. <br /> <br />SubDart 2 - Production Delavs Due to Unforsef!!n Soil Conditions <br />In this same area, the muck encountered caused the contractor delays In the installation of the <br />water main. The unsuitable materials necessitated the use of trench boxes, additional excavation <br />below the pipe to provide a stable base and the construction of a temporary by-pass road to <br />keep traffic from sinking in the muck. The attached estimate, along with the contractor's letter, <br />documents the cost of this work. <br /> <br />St. Paul <br />5t. Cloud <br />Rochester <br />Milwaukee <br />Chicago <br /> <br />Enqlnccfln9 <br />Pli-Hlnmg <br />Innovation <br />