Agenda - Council - 06/23/1981 - Laserfiche WebLink

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Honorable Mayor and City Council City of Ramsey June 18, 1981 Page Three Generally, the bedrock formations in the northern suburbs slope gently to the south. For example, the Mt. Simon sandstone occurs at an elevation of approxi- mately 700 feet above sea level in Elk River, while it is found at a lower elevation of approximately 370 feet above sea level in Anoka. Superimposed on this general slope are various faults, buried valleys, etc., which make it diffi- cult to predict the exact depth and thickness of various formations at a given location. Although there is little information available on bedrock formations in Ramsey, it is possible to estimate what the formations are like by examining logs of .deep wells located in surrounding communities. We have looked at logs from deep- wells in Elk River, Andover, and Anoka and combined that information with the data on shallower residential wells in Ramsey. The result is the geologic cross- section shown on the accompanying exhibit. The cross-section is an estimate of bedrock depths and thicknesses for the southeast corner of the City, in Section 25. It should be emphasized that this exhibit is approximate and is intended merely to illustrate the general arrangement of the formations.. Specific depths and thicknesses will vary at different locations due to faulting, erosion, sur- face elevation, etc. Because of these factors, it is impossible to predict precisely how a well log at a given location will look. The first water-bearing formations which exist in Ramsey are the Franconia and the Ironton-Galesville, as shown on the exhibit. The Ironton-Galesville generally has the higher hydraulic conductivity of these two formations. It is considered the first formation in which water is likely to be found in municipal-supply quantities. The quantity of water available in the Franconia and Ironton-Galesville formations can vary considerably from place to place, and the yield at a given location'can- not be predicted accurately without test drilling and pumping. However, a small 'diameter well at the Anoka High School, developed in the Franconia and Ironton- Galesville, produced over 200 gpm with a drawdown of only ? feet during its test pumping. We estimate that a larger diameter well (12 inches or more) located in the southeast corner of Ramsey could be reasonably expected to produce 400 to 500 gallons per minute, with'a possibility of even greater yield. The next formation, the Eau Claire, consists of shale and sandstone. It is con- sidered a confining layer and is not a good source of water. The Mt. Simon formation is the next major source of water. It is sandstone, with small amounts of shale. It is estimated to be approximately 130 feet thick in southeast Ramsey although, again, this is variable. Most of the municipal wells in the area immediately surrounding Ramsey which were examined for this study draw water from the Mt. Simon formation. This includes an Elk River well completed