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LAKE FLMO CITY COUNCIL MBlw.PIIqGo OCTOBL'R 21, 1980 -8- LITTLE SUNFISH: Administrator Whittaker noted, besides the culvert, we would have to replace the driveway and would probably have easement costs. Engineer Bohrer noted this would not endanger any residents:or buildings, but it would take more property. Al Lehman, 3M , still has problem with some of the L'hgineer's numbers. Ile feels the problem is primarily due to the surface run—off, not the ground water. From 'their .records surface water had the most extreme change in the five ,years that they have kept records. For instance, in five days in late August, we had a, five inch rain., Little Sunfish rose 4.1 ft., Lake limo rose less 'than a foot, Horseshoe rose 1 ft. Then, after a period of time of little rainfall, Sunfish receded to a point that is just a little above Horseshoe Lake (a foot or so above). In the five years of records Little Sunfish has never been lower than Horseshoe Lake. Lhgineer Bohrer said that theiopographic map the City has the water elevation on Little Sunfish Lake was 864.5. Now, it is about 15 .ft. above that. He said this must be due to the water table as well as surface water. Horseshoe has been down in that period to time, also. The water table in the entire area is up. Mayor Armstrong asked if Sunfish and Horseshoe rise and fall together? Mr. Lehman replied no, Sunfish is alway a little higher than Horseshoe. Little Sunfish is more affected by a heavy rainfall than Horseshoe or Lake Elmo. Armstrong asked if Horseshoe would rise if Sunfish was 6 feet higher than Horseshoe? Mr. Lehman said yes, I think it would, over a period of several months. Sunfish does recede to an elevation somewhat above horseshoe„ so it -gets into the ground water area. that goes directly to Horseshoe. The reverse is a,1so truo. If you pump Sunfish down, it will rise to the level of Horseshoe Lake. Even if there is some sealing of -the lake and, although there may by a seal., due to the compaction of County Road 70, water may pass from the south side to the north side if the culvert is plugged and ,you pump from the south side to the north side of Sunfish Lake itself, we don't know that pumping from one side of the road to the other is going to to prevent it from coming back. Engineer Bohrer said the roadbed itself would act like a dike. It is quite wide; but, some seepage may occur, as with any dike. It is not something that would solve the -total problem. We would have to incorporate more of these alternates to gain a higher level of confidence. Mr. Lehman said the basic problem is from storm water, getting a fair amount of rainand having it rise. If you pump out Sunfish, it is going to rise back up to a level that won't handle the storm. Horseshoe is just 2 feet higher in elevation than Sunfish. If you pump it down, it is going to come back up to about the same elevation. - Larry Bohrer replied, that is assuming that the ground water table is the same elevation as the surface on Horseshoe Lake. Mr.. Lehman said their water table tends to slope from west to east so it appears to in in the neighborhood of 78% of Sunfish Lake. The Watershed's obser— vation well, across from Cimarron, just west of Sunfish, has an elevation of 817 for the ground water. Mayor Armstrong asked is pumping from the south to the north, using County 70 as a dike will solve half the problem? Engineer Bohrer explained the relative size of Sunfish is 13A on the north and 8 to 8 1/2 acres on the south. The rise of the land is fairly steep so you don't gain a great amount of area to raise the level a couple of feet. Armstrong said this south to north pumping be considered Alternative LF. Engineer Bohrer said there are a lot of different alternatives, if we are not allowed r to transfer water to Horseshoe, then the other alternatives not considered \, either because of high costs or they did not solve the total problem, now have more importance