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HomeMy WebLinkAbout10C - C.R. 21 Watermain Replacement Project MEETING DATE: AGENDA #: PREPARED BY: AGENDA ITEM: DISCUSSION: 4646 Dakota Street S.E. Prior Lake, MN 55372-1714 CITY COUNCIL AGENDA REPORT APRIL 20, 2009 10C STEVE ALBRECHT, DIRECTOR OF PUBLIC WORKS CONSIDER APPROVAL OF A RESOLUTION ACCEPTING A REPORT AND AUTHORIZING STAFF TO COMPLETE A FEASIBLlTY REPORT FOR THE CR 21 WATERMAIN REPLACEMENT PROJECT I ntrod uction The purpose of this agenda item is for the City Council to accept a report and authorize completion of a feasibility study for the CR 21 Watermain Replacement Project between Eau Claire Trail and Quincy Street. Historv As the City Council is aware during the week of February 1 st the City shut down CR 21 for a period of 3 days to complete repairs to the 24-inch diameter watermain located in CR 21 between Eau Claire Trail and Wagon Bridge Circle. In 2007 the City completed a large repair to this watermain just east of the Wagon Bridge. The total cost of repairs for these two events will most likely exceed $100,000. The 24-inch main is the City's largest watermain and provides one of three east west connections from the east to west side of Prior Lake. The watermain is ductile iron and was constructed in the late 70's. Under normal conditions this main would be expected to have a 50+ year life. It is currently about 30 years old. This main is especially important during high water use periods and large fire events. During the 2007 incident it was determined that a large rock placed during construction of the bridge or roadway most likely created the hole in the main. Over time the vibration of this rock against the pipe created a weak spot that eventually failed. However an inspection of the pipe during the repair did not indicate any other unusual wear on the pipe. In 2009 the repairs revealed that the bottom side of the watermain was corroded and failed due to vibration of small rocks near corroded areas. The corrosion was most likely due to acidic soils in the area that over time reacted with the ductile pipe and decayed the underside. In 2007 part of CR 21 was reconstructed over a portion of the watermain. The pipe was insulated during that project and no corrosion was noted on the top side of the pipe. This is consistent with the repair findings. It appears that the cold winter with deep frost conditions of over five feet in the roadway based on City observation during construction may have also contributed. While the pipe did not freeze, the frost reached to the insulation layer and created a connection transferring vibrations from the roadway to the pipe and causing small stones to penetrate the corroded sections of pipe. A total of three areas were repaired during this latest episode. www.cityofpriorlake.com Phone 952.447.9~00 / Fax 952.447.4245 Current Circumstances City Staff believes that if not replaced the watermain will continue to fail with the next event most likely occurring next winter. The costs from a financial, traffic, utility and employee safety perspective would be significant. Because of the valving on the watermain certain neighborhoods have to be shut off each time the break occurs. Also depending on the location of the breaks the watermain can substantially impact traffic (up to 12,000 trips per day). In addition to those impacts a major Integra fiber optic conduit is located on top of the pipe for a significant segment of the area. This fiber optic makes repairs difficult and time consuming. Based on the above Staff has identified four potential repair options: 1) Completely replace the watermain in shoulder of CR 21 with a new watermain (PVC & HOPE) directionally drilled under the bridge channel. The shoulder construction would be done utilizing traditional construction open-cut methods. 2) Completely replace the watermain (HOPE) by directionally drilling new watermain under channel and under road shoulder. 3) Slip line the existing 24" watermain (PE Liner) 4) Pull a new smaller diameter HOPE watermain through existing 24" pipe. Based on a preliminary analysis staff believes that options 1 and 2 are the best long term solutions. These options are permanent and move the watermain to location where the City can access it in the future for any needed repairs. These options also minimize the disturbance to CR 21 during construction. ISSUES: Before staff can make a final recommendation to the City Council a survey of the existing right-of-way corridor and soil borings need to be completed. A survey is necessary to locate existing utilities and property lines to complete the evaluation of this option. All options would involve the directional drilling of a new segment of watermain under the lake as the existing watermain has sharp bends that will be very difficult to line. In order to directionally drill watermain soil borings are needed in the lake bottom (taken from a barge) and in the shoulder. The directional drilling of pipe requires soils that can both be bored and that will support the pipe. FINANCIAL IMPACT: In order to complete a feasibility study for the City Council staff is requesting that the Council authorize expenditures of up to $6,400 for additional survey work and up to $9,550 for the required soil borings and analysis. The funding for this work is available in the Water and Sewer Fund. 1. Approve a resolution accepting the report and authorizing staff to complete a feasibility study for CR 21 Watermain Replacement. 2. Table the Resolution for a specific reason. 3. Deny the Resolution. ALTERNATIVES: RECOMMENDED Alternative # 1 MOTION: Reviewetffh,_ Frank Boy16s, CIty Manager 4646 Dakota Street S.E. Prior Lake, MN 55372-1714 RESOLUTION 09-XXX RESOLUTION ACCEPTING A REPORT AND AUTHORIZING STAFF TO COMPLETE FEASIBLlTY REPORT FOR THE CR 21 WATERMAIN REPLACEMENT PROJECT Motion By: Second By: WHEREAS, The CR 21 watermain between Eau Claire Trail and Quincy Street is an important piece of the City's water infrastructure; and, WHEREAS, Breaks occurring this past winter revealed that if left un-repaired the watermain will most likely continue to fail annually at considerable cost to the City; and, WHEREAS, A feasibility report is required to identify the most cost effective options for the repair; and WHEREAS, In order to complete the report the City will need to complete a survey of the CR 21 Corridor and have soil borings taken. NOW THEREFORE, BE IT HEREBY RESOLVED BY THE CITY COUNCIL OF PRIOR LAKE, MINNESOTA as follows: 1. The recitals set forth above are incorporated herein. 2. City Staff is authorized to complete a feasibility study for the CR 21 Watermain. 3. City Staff is authorized to have a survey and soils borings completed for costs not to exceed $6,400 and $9,550 respectively. 4. Funding for these services shall come from account # 601-49400. PASSED AND ADOPTED THIS 20th DAY OF APRIL 2009. YES NO Haugen Erickson Hedberg LeMair Millar Haugen Erickson Hedberg LeMair Millar Frank Boyles, City Manager www.cityofpriorlake.com Phone 952.447.9800 / Fax 952.447.4245