Agenda - Council - 11/27/1990 - Laserfiche WebLink

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CASE REQUEST TO DRAW ON NORTH FORTY 3RD ADDITION ESCROW ACCOUNT TO CONSTRUCT STORM RETENTION POND By: Steve Jankowski, City Engineer Background: The North Forty 3rd Addition subdivision lies adjacent to the Whispering Pines subdivision. When Whispering Pines was developed in the early 1970's, drainage easements were not taken, and an area of approximately 20 acres within this subdivision drains into the lot owned by Mr. and Mrs. Bustrom located at 8341 - 154th Lane N.W. As a result, water ponds in the Bustrom's back yard and an area immediately north of their property in the North Forty 3rd Addition subdivision. The impact of this ponding is greatly compounded by the fact that the Bustroms have a finished walk-out basement which, they have reported, has had standing water as close as ten feet in the past. Although the developer of North Forty 3rd Addition subdivision is not responsible for providing drainage storage for the Whispering Pines subdivision, the approved drainage and grading plan called for the construction of a 100 x 230 foot drainage retention pond enlarging the natural low area behind the Bustrom's property. The dimensions of this proposed pond would provide several times the pre-development ponding volume. During the fall of 1990, the developer graded streets and ponding areas within the subdivision, however, he did not grade the ponding area behind the Bustroms to the dimensions shown on the plans, and because of grading for a roadway, portions of the previous low area available for ponding was filled. The two foot contour intervals available do not allow for a very precise measurement of the pre-existing and current storage conditions, but based upon field observations and measurements, there may be less ponding volume available than originally existed. This deficiency was pointed out to the developer in a November 7, 1990 letter by Mr. Pete Raatikka which requested that the approved grading be in place by November 21, 1990. As of the date of this writing, this grading has not taken place. Recommendations: Although the development agreement allows the developer until June, 1991 to complete Phase I improvements, I believe the following facts justify the recommendations that the City Council authorize the use of the developers escrow account to grade this pond to the required dimensions immediately. 1) The grading done to date has likely caused a net decrease in the ponding volume available to store storm run-off. 2) The developer had graded other ponding areas in the subdivision and had an opportunity to construct this particular ponding area according to plans. 3) The developer was notified in writing that the existing grading was not acceptable and was given a reasonable amount of time (two weeks) to correct the grading. 4) That failure to grade the ponds this fall will present a substantial risk of flooding of the Bustroms walk-out basement during the critical melt period next spring. 5) That to allow the developer additional time this fall to correct the situation is no longer practical since impending frost conditions will make the grading more expensive or impossible.