10-20-1997 Planning Packet - Laserfiche WebLink

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r Zoning File #2294 October 17, 1997 Page 6 of 9 9. :cuJ to the road, and applicant has been requested by the City Engineer to provide drainage calculations defining the 'before' and 'after' flow rates tlirough both northerly and southerly ravines. Applicant proposes sanitary sewer extension to the propert} approximately 300' north of an existing manhole on Wildhurst Trail, then e.xtendir.g westward up the slope between Lots 3 and 4. The City Engineer has suggested that the section of sewer paralleling Wildhurst Trail will be difllcult to construct due to adjacent slopes, and that an alternative is construction of that segment underneath the travelled portion of Wildhurst Trail. Due to the narrow design of Wildhurst Trail and the fact that it has no alternative ingress/egress. City staff will further recommend a condition that this segment of sewer be directionally bored tq. avoid traffic disruption on Wildhurst Trail. Further, staff will recormnend that the segment between Wildhurst Trail and the easterly cul-de-sac be directionally bored to avoid disruption of the 17% slope between Lots 3 and 4. 10.A drainage and utility easement 20' in width is proposed over the southerly ravine, a portion of the acreage of which has been subtracted from the area of Lot 4 because it is not strictly a perimeter easement. Note that perimeter easements abutting properties outside the plat should be increased from 5' to 10', similar to those shown adjacent to streets, and interior lot boundaries should be provided with a drainage and utility easement 5' either side of said boundaries. Stormwater Planning In the context of protential stormwater impacts to the surrounding neighborhood, this subdivision is situated and has been designed to provide certain stormwater benefits which have not been available via the hitherto sjxiradic development of individual building sites in the neighborhood. Surrounding property owners located downstream from the drainageways at the north and south end of this site have indicated their serious concerns about adding new roads and homesites to what currently is an undeveloped, and mostly uncontrolled, upland watershed. In response to these concerns which are shared by the Ci^, the City has required, and the applicant has responded, with the following stormwater management systems and techniques: 1.All drainage from the entire length of proposed new roads will be directed northward to a storage and retention pond located above the head of the northerly ravine. 2.Likewise, virtually all drainage from Lot 1, Block 1 and Lot 2, Block 2 will ultimately be directed to that stormwater pond. 3.The driveway drainage and a portion of the roof drainage from Lots 3, 4 and 5, Block 2, will be directed to that stormw'ater pond. J