INFORMATION #2 10-04-2010 - Laserfiche WebLink

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INFORMATION E~ MEMORANDUM 1~" TO: Mayor and City Council FROM: Justin Femrite, P.E., City Engineer DATE: October 4, 2010 SUBJECT: 182"a Avenue Storm Sewer and Pond Level The storm sewer repairs have been completed at the intersection of 182na Avenue and 181St Lane. The repairs that were completed addressed the pipe heaving problem that developed across the street in the intersection. The work completed allowed for the removal of the pipe crossings and separation of the storm water systems on both sides of the street. The storm water draining from the north side of the intersection drains into the pond on the north and the water draining to the south side of the intersection drains to a pond further south. The project alone did not address the water level in the pond area north of 182na Avenue, which is still a concern as the water elevation is backing up into the storm sewer system on the north side of 182na Avenue. The water level of the pond, as shown in the attached figure, was originally designed and maintained at 895.10. This elevation was raised in 2005 as a reaction to the public support for maintaining a higher than designed water level in the pond. In 2005 the ponds outlet control structure was modified to raise the water level in the pond 2-feet to an elevation of 897.10. This higher water level is directly responsible for the heaving problems encountered in the intersection of 182na Avenue and 181St Lane. Currently the water elevation in the pond on the north side of the roadway is being maintained at 897.10. This water level is causing the remaining storm sewer system on the north side of 181St Avenue to sit full of water. The catch basin on the north side of 181St Avenue has 2.50 feet of water standing in it. If left uncorrected, the water in the catch basin may freeze solid this winter and prevent the north half of this intersection from draining. Phil Hals and I have reviewed the area and agree the water level in the pond north of 182"a Avenue must be drawn down to the designed elevation of 895.10 for the winter months to prevent the storm sewer system from freezing and causing additional damage. We are prepared to make modifications to the outlet control structure which will allow the pond be drawn down every fall to the originally designed elevation of 895.10. This will allow the storm sewer system at 182"a Avenue to function as designed through the winter months. While we would prefer to make this a permanent improvement, in order to maintain this lower elevation, we understand the public's concern for wanting to see water in the pond. As such we are proposing to make modifications to the outlet control structure that allows C:\Documents and Settings\XPMUser\Local Settings\Temporary Internet Files\OLK66\182nd Avenue Storm Sewer and Pond Level.doc