2014-10-08 CC Packet - Laserfiche WebLink

Home Browse Search

Stantec Consulting Services Inc. } Stantec 2335 Highway 36 West,St.Paul MN 55113-3819 October 1, 2014 File: 193801639 Attention: Dallas Larson 1880 Main Street Centerville, MN 55038 Dear Dallas, Reference: Centerville Road (CSAH 21) Forcemain/Storm Sewer Conflict During the design of the trunk storm sewer for the proposed improvements on Centerville Road (CSAH 21), it was noted that two Met Council Environmental Services (MCES) forcemains cross Centerville Road,just south of Meadow Lane. The elevation of these forcemains, according to MCES Record Plans,showed that there would be a conflict between the two utilities (trunk storm sewer and forcemain). Therefore,a provision was made, in the contract, to have the forcemains lowered, under the new storm sewer. This appeared to be the most direct and efficient way of resolving the conflict. This was based on the idea that the forcemains could be simply "offset" with a few bends, down and under the storm sewer, and then back up. We have successfully used this method on many previous projects involving sanitary sewer forcemains and county engineering staff had discussed this method with MCES staff. Recently, as the contractor applied for a permit to work on the forcemains, MCES informed them that this design would not meet their requirements. MCES will require a set of air release manholes and clean out manholes; one of each on each forcemain. The contractor has provided a quote for the new structures and equipment at a total additional cost of$91,000. Given this cost, other options have been reviewed. The option which appears to be the most cost effective is to redesign the storm sewer to go under the existing forcemains, leaving them unaffected by the project. The cost for this alternative option is approximately$42,000. This cost is a "net" cost,after factoring in the savings realized by eliminating the original forcemain offset work from the contract. The City is splitting storm sewer related costs for the project with the County at a rate of 75%City to 25%County. Therefore,the total additional cost to the City would be approximately$31,500. The option of lowering the storm sewer is significantly less expensive than the modifications to the forcemains. It also has the added benefit of cleaning an additional 230 feet of City-owned ditch along the south side of Laurie LaMotte Park. This option will also provide an opportunity to have a Design with communfly in mind 74