Agenda - Public Works Committee - 11/20/2001

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P.W. CASE Investigation of Dirty Water Complaint Expressed at the October 16, 2001 Public Works Committee Meeting By: Brian E. Olson, City Engineer Last month we received a letter regarding the clarity of municipal water in the Wood Pond Hills subdivision. The purpose of this case is to discuss the background of rusty water complaints, explain some of the causes, explain our current City processes to ensure clean water, and discuss alternatives that could curb the frequency of these types of complaints. Background: All of Ramsey's municipal wells have elevated levels of iron and manganese typical to the aquifers utilized for municipal water supply throughout the Twin City area. The combination of these high levels and operational changes result in rust or discolored water in the system. Throughout normal operation, the velocity of the water flowing through the pipes is relatively low and the longer the water remains in the pipes, the more chance the iron and manganese particles have to precipitate out. While the water towers provide storage to meet demand, it also provides water pressure so that water comes out of your faucet when you turn your water on. This pressure is directly relational to the elevation difference between the water in the tower and your house, and results in the iron and manganese particles being "pressed" to the inside of the pipes. Generally, the flow patterns are defined by the use and demand of the system. Put another way, the direction the water flows is established and altered by each new addition, change, or hookup to the system. In Ms. Hunter's case, the supply of water was most likely coming from Water Tower #1 during normal operation. As discussed at the last Public Works Committee, staff consulted with Bolten & Menk. They have a modeling software called Cybernet that models Ramsey's entire water distribution system. Attached to this case are some co_mments that they have regarding the discolored water that was presented last month. Causes of Discolored Water Complaints As mentioned in the above discussion, the velocity of the water in the pipes is relatively low and unidirectional during normal operation of the system. The main cause of discoloration to the municipal water customer is a significant increase to the velocity and/or change in direction of flow of water.