05/08/1995 Council Packet - Laserfiche WebLink

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Ms. Mary Kay Wyland April 20, 1995 Page 4 Page 2, Paragraph 2 On the north side of Holly Drive West, the 0.37 acre wetland identified as Basin B is saturated at a depth of 12 inches. Pond #3, a small holding pond which directly abuts Basin B, has a gradient of 906 feet at its lowest point, with a culvert draining into it, from the southern portion of Road j. The property owner's 8 -acre parcel adjacent to this southeast quadrant of the project, has a gradient of 909-910 feet near this pond, allowing 3-4 feet capacity, before overflozving --- should the outgoing culvert from Basin B, be unable to adequately handle any excess water problems. According to the P8 model, under normal conditions, the maximum water elevation in Pond 3 will be 909.1. The water will have to be at least this high to discharge into the adjacent wetland. Under the conditions of five 100 -year storms in sequence, the maximum elevation of the pond is predicted to be 909.4, still below the maximum elevation of the pond. Page 2, Paragraph 3 From Basin B, this outgoing culvert is run beneath Holly Drive West and drains into the wetland identified as Basin C on the south side of the street. Basin C is a Large wetland, about .3,57 acres in size. Its gradient is 908 feet near the roadway and decreases to 906 feet at its southern end where there is an outgoing culvert beneath Road A --- which drains into Pond #5, a small holding pond with a gradient of 904 feet directly adjoined to the wetland identified as Basin E. Basin E is about 1.53 acres in size with a gradient of 907 feet. There is some mitigation, which divides Basin E in half, to allow for the construction of Road B --- but a culvert beneath this road provides excess water movement south. The adjacent property owner's 10 -acre parcel on the southern boundary of the project is 906 feet, allowing for no flooding capacity on-site. The other adjacent property owner's 11.5 -acre parcel (1101 Holly Court East) on this same boundary has a gradient of 909 feet, which allows only 3 feet of water before it potentially floods onto lois land also. The proposed culvert under Holly Drive will drain water from Basin B on the north side of the road to Basin C on the south. The elevation of Basin C is 908 feet near the roadway and increases to 914 on the southern end. Water from Basin C will north into Pond 4 and eventually into Basin A as it currently does. (The culvert referenced in the above paragraph will carry runoff from Road A into Pond 5.) Page 2, Paragraph 4 To summarize: The culvert from Basin 13, on the north side of Holly Drive West, interconnects the wetlands, composed of Basins C and E -- and the holding ponds, throughout the western half of this project --- to eventually drain excess water onto the adjacent southern properties, along with any potential residential contaminants. The culvert from Basin B to Basin C will not facilitate the drainage of water from the northern portion of the site to adjacent southern properties. Basins B and C naturally drain to Basin A and will continue to do so under developed conditions.