Agenda - Council - 07/28/2009 - Laserfiche WebLink

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CASE # q ADOPT RESOLUTION 09 -07 -XXX RATIFYING CHANGE ORDER NO 1 FOR IMPROVEMENT PROJECT #08-27, WATER TOWER #3 By: Tim Himmer, City Engineer Background: On June 23, 2009 the City Council awarded the contract for construction of water tower #3 at 16600 St. Francis Boulevard. During site grading and excavations for the tower footings additional clay material was discovered in the area below the proposed foundation. Staff and our geotechnical consultant evaluated 3 boring locations, prior to project initiation, around the perimeter of the proposed tower footings and only minor clay lenses were found and identified for removal. Unfortunately soil borings only provide information for the area directly under the location which they are taken and they did not provide an accurate description of all the underlying material. Continuing work in this location would add significant unknown costs to the project, as the contractor and geotechnical consultant would need to continue with corrections until such time that good supporting soils are encountered. As you may recall, multiple locations in close proximity to one another were investigated during the site selection process. The ultimate location chosen was in the southeast corner of the site, adjacent to Highway 47, so as to keep open as much usable space as possible for future use of the remaining land that was acquired as part of this project. A decision has been made to limit our exposure at this time and relocate the tower approximately 150' to the west on the site. This area was also investigated previously with prior soil borings, and test pits are underway to determine corrections. This area was already being impacted by the relocation of on-site soils to increase the elevation of the approved tower site thereby limiting the ultimate size of the tower. Preliminary results are favorable for minor soil corrections (sand compaction), as no clay soils have been encountered. Observations: Following is a list of items that need to be investigated and evaluated for a more definitive accounting of financial impacts: Additions • Grading (cuts, fills, and compaction) of the old and new locations. • Consultant time for plan revisions and additional inspections. Deductions • Less watermain as the tower will be located closer to the existing pipes. • Less steel as the tower will be located at a higher elevation. Mayor Ramsey and Councilmember Elvig have reviewed these changes with staff on site, as staff wanted to keep Council in the loop on these proposed changes. Timing for this decision is critical as construction crews are already mobilized on the site, and the contractor is being held to strict performance standards for project completion.