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4.12. SR 10-25-1993 e 132& Energy Park Drile St Panl, UN 55108-52lt2 612.644-4389 e Fal: 612.644.9H& 9800 SbelanI Parkway, Ste.102 HinneaPillis, HN 55441.6451 612.54&-D432 Fat &12-544.6398 ITEM 4. 12 . October 21, 1993 File: 230-161-70 The Honorable Mayor and City Council City of Elk River 13065 Orono Parkway Elk River, MN 55330 RE: MnDOT Utility Coordination Dear Council Members: We have been working with MnDOT on an ongoing basis relative to sanitary sewer, water and most importantly storm drainage improvements crossing the intersection of Highway 169/101/10. We had hoped to have specific information relative to these improvements which could be provided in the Council packets. Unfortunately we are still waiting for information from MnDOT. Therefore, I will be prepared at Monday evening's meeting to verbally update you on the status of this coordination effort. I also hope to have some information available relative to the cost of storm sewer pipes through this interchange vs. the size of upstream ponding necessary. This whole issue will likely come down to an economic decision of whether it's more cost effective to build larger pipes through the highway interchange or commit more land upstream to future pond construction to minimize the size of the pipes. Sincerely, MSA, CONSULTING ENGINEERS ~~ T~aurer,~ TJM:ds 161.2111.oct !II "" s CONSULTING IlNGlNEERS _ 13'.!& Ener~ Park Drive St.1'IIII, M 551l18-m 612-&<<-4389 _hI: 6l~.s<<.S44S UlMnlParkway, Ste.1ft! lliDoeapelis, M 55441-5451 612.5(5-0432 hI: 612-5.14_ 1/~ --- October 25, 1993 File: 230-161-70 The Honorable Mayor and City Council City of Elk River 13065 Orono Parkway Elk River, MN 55330 RE: City/MnDOT Utility Coordination Dear Council Members: Over the. last several months, we have been working with MnDOT personnel to pursue any opportunity the City would have to install utilities in conjunction with the MnDOT upgrade of the TH 10/1011169 interchange. Our latest meeting was last Tuesday at MnDOT's Golden Valley office. We met with Mr. Tim Johnson, the TH 101 project manager, and several members of his support staff. IThe main issue we discussed was the final configuration and construction staging for the MnDDOT project relative to the City's desire to include conduits for future sanitary sewer and water facilities for East TH 10 and storm sewer from south of the railroad line to the Mississippi River. The following is a brief summary of the conclusions we reached on each of these issues. 1. Sanitary SewerlWater Conduits There is no opportunity for the City of Elk River to install conduits for future extension of sanitary sewer and watermain to the East IDghway 10 corridor in conjunction with MnDOT's project. The reason for this is MnDOT's policy does not allow conduits through the heart of the clover leaf exit and entrance ramps of any interchange. Utilities crossing the interchange must be routed around the exit and entrance ramps. The MnDOT plan for the trunk highway 10/1011169 interchange does not propose any open cutting of areas outside the immediate interchange. Therefore, if we were to include these conduits in this project, they would have to be jacked. This would not provide for any costs savings since in the future we will have the opportunity to install them by the same method. We are therefore recommending to the City of Elk River that the issue of conduits for future sanitary sewer and water extensions be dropped at this point in time. " e The Honorable Mayor and City Council October 25, 1993 Page Two 2. Storm Sewer As you are aware, the Comprehensive Drainage Plan calls for a 72-inch diameter storm sewer line from the railroad line through the MnDOT interchange to the Mississippi River. Unfortunately, MnDOT's final design of the TH 10/101/169 interchange does not provide enough elevation difference to install a 72-inch diameter culvert. In order to get comparable capacity in a smaller size culvert, three parallel 42" diameter culverts would need to be installed. The other concern with the MnDOT design is their traffic and construction staging plan does not allow for open cutting of the entire length. The total distance from the Mississippi River to the north end of the interchange project is approximately 850'. 350' of this length would require jacking in order to maintain the integrity of the MnDOT staging and traffic plan. The remaining 500' could be open cut. e Obviously, the installation of 3 parallel pipes is going to be much more costly than the installation of 1 larger diameter pipe. We have estimated that each 42" diameter pipe from the Mississippi River to the north end would cost approximately $175,000 to $200,000. Therefore, the installation of 3 parallel pipes would cost between $525,000 and $600,000. It should be noted that this work does not include crossing under the railroad tracks which would still require a 72" diameter culvert. If the City were to decide to not install 3 42" culverts but only one to save monies on the installation costs, the effect would be the requirement of more ponding to be constructed upstream. We have prepared a brief analysis of the increased ponding relative to the culvert capacity through the MnDOT interchange. These are listed in the following table: 140 CFS 220 CFS 300 CFS Ponding 180 AC-FI' 135 AC-FI' 110 AC-FT Pipes 1 - 42" 2 - 42" 3 - 42" Flow e It is unlikely that the DNR and the Army Corps of Engineers will allow this amount of ponding in wetlands upstream of the railroad tracks. Therefore, it should be assumed that ponding will utilize land which would otherwise be suitable for development. We would recommend at this point in time that the city proceed through MnDOT to include three 42" diameter pipes in the MnDOT project with the option to eliminate 1 or 2 of them depending on the construction costs. This approach would allow us to get an actual construction cost and do a much better cost-effective analysis of the cost of culverts vs. ponding after bids are open. . The Honorable Mayor and City Council October 25, 1993 Page Two I will be in attendance at Monday evening's City Council meeting to discuss this in further detail. I will be prepared to answer any questions you have at that time. Sincerely, MSA, CONSULTING ENGINEERS ~:MauuJ Terry J. Maurer, P .E. TJM:ds 161-2S02.OCT e .