Agenda - Council - 11/12/2013 - Laserfiche WebLink

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Notification: None required. Observations/Alternatives: Staff also evaluated the cost to install a new lining in the existing culvert, rather than replacing it, which would provide needed structural support. However, the cost for materials alone would exceed $20,000, and when factoring in labor the costs to line the culvert would exceed the cost of the lowest quote received for installing a new CMP culvert, even with the needed road repairs. As such, staff does not recommend this option be considered. Staff also evaluated costs to replace the 48" CMP with 48" Reinforced Concrete Pipe (RCP) and 48" High Density Polyethylene (HDPE) Pipe. The life expectancy of CMP has proven to be about 30 to 40 years, whereas the life -expectancy of RCP has proven to exceed 50 years. The life expectancy of HDPE is estimated to be more than 50 years too, but since HDPE has not been in use this long this has yet to be proven. However, based on the condition of HDPE pipe that has been installed for 20 years or so, the general consensus is that the life expectancy of HDPE pipe will be at least 50 years. Below is a table outlining the estimated costs for replacing the 48" CMP culvert with 48" CMP, 48" HDPE, or 48" RCP pipe. Even though the drainage capacity of HDPE and RCP pipes are greater than CMP pipe due to their smooth inside walls, staff does not recommend reducing the pipe diameter because the culvert immediately upstream is a 48" culvert and it is generally not an accepted practice to reduce pipe sizes downstream. The project cost for each pipe type in the last column includes costs for the two flared end sections. And if RCP pipe were to be used, there would be an additional project cost of about $5,000 for additional grading and traffic control requirements due to the shorter pipe lengths. Pipe Size & Estimated Furnish & Install Estimated Furnish & Install Cost for Material Cost per Lineal Foot Project (includes 2 FES's) 48" CMP $185 $14,200 48" HDPE $160 $12,500 48" RCP $325 $26,200 Per the estimated costs above, HDPE pipe appears to be the most economical to install while CMP pipe is not far behind. RCP is by far the most expensive. Funding Source: The replacement of this 48" CMP culvert is not identified in the 5-year CIP, and no money was budgeted for this work in 2013, or in 2014. This work is therefore proposed to be paid for through the Stormwater Fund. Recommendation: Staff recommends replacing the existing culvert with 48" CMP pipe as soon as possible. Since County Ditch #14 is currently dry and the residential neighborhood north of this culvert crossing has no other access, one lane of traffic must be maintained at all times during the work. If this work is delayed until next spring/summer, the ditch will likely be conveying storm water runoff which would require the water to be pumped through a hose across Vanadium Street, thereby prohibiting or even preventing one lane of traffic from being maintained at all times. Also, considering the small cost savings that could be realized by switching from CMP to HDPE pipe, this savings may not justify the delays associated with switching to HDPE pipe due to completing the required storm water modeling and the potential cost increase associated with ripping through frost if the delays are substantial and/or the weather turns cold quickly. Bituminous plants will be closing soon so the sooner this work can be completed the better the chance is that the