01-23-1978 Council Minutes - Laserfiche WebLink

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REGULAR 24EETING OF TFiE OROi10 COUPICIL, JANUARY 23, 1978 Page 36 TANAGER LAKE CHANNEL (Continued) 1. Reliability of Proposed Construction The �lans indicate two 18 inch ball joint river crossing pipes for the channel crossing, bedded in 3/4" to 1'�" 100% crushed rock and covered with 2" to 4" screened rock to elevation 920.5. Ball joint pipe is the strongest, most fail-safe product available for this type of work. The ball joint allows for maximum deflection at the pipe joint without leak- ing or without the pipe joint being pulled apart under differential settlement. A channel crossing cleanout manhole is located on either side of the channel. Each manhole is 10 feet in diameter and represents a very heavy, concentrated load on the underlying soils. The City of Orono should insist on evidence that these two manholes are adequately sup- ported to prevent settlements which could shear or break the force main pipe and thereby result in a possible direct discharge of raw sewage into the lake. (The Hennepin County Bridge plans required piling for the retaining walls located 25 feet east of the channei crossing.) 2. Restoration of Banks The specifications and the permit should include provisions to restore the banks and the rip-rap to prevent bank erosion, together with mainten- aace of suitable ground cover immediately after construction. 3. Channel Erosion The Storm Water Management Plan indicates a maximum storm water flow of 152.5 cubic feet per second (cfs) entering Tanager Lake and a flow of 92.2 cfs leaving Tanager Lake through the channel into Browns Bay, Provisions should be included in the permit to prevent channel excava- tions at such times as there are currents in the channel which could wash sediment and debris into Browns Bay. 4. Maintenance of Boat Traffic Provisions should be included in the per*'Ait to ensure the maintenance of boat traffic on either a continual basis or on at least an inter- mittant basis during construction. There is a place to enter these concerns on Section II of the application form and we recommend that the above item be so included. If we �y be of further assistance in this matter, please contact us at your earliest convenience. Under separate cover, we are returning the permit application information submitted to us by your office. (Continued)