02-11-1991 Council Packet - Laserfiche WebLink

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January 3, 1991 FairHay Hills Add. Pags 3 of 3 /) 3. Surface Drainage airfaos Mater floe through the site appears to be intennittent. There is no clear established drainageNay through part of the wetland. Pasf»d cn the high eater infonnatiGn provided by the MCX7T TH 12 plans, we have ooepitted expected floes from a 100 year storm to be 19 cfs, and have provided teo 18” culverts under the driveway to accommodate this water. We suggest that these culverts be placed at a relatively flat grade and at an elevation which will pass the 100 year storm without an increase in hi^ water elevation. We also suggest that, to maintain the r-haract«»r of the wetland, no pacific channel be constructed connecting the existing culverts. Some annual maintenarce of this culvert may be required. 4. Storawater Detention The re^ilations of the watershed require on-site stormwater detention •dwre runoff flcwe are altered. Construction of two houses and the driveway ixxild cover about .55 acre with impervious surfacing or 9% of ths sits. In our preliminary conversations with Nr Ron Quanbeck from the Mstsrshsd, he indicated on-site detention may not be required for this devslopment. If it is determined that stomwater detention is southeast of the driveway in Lot 1 and north of the house be adequate for this purpose. SuDBiftry , the in Lot 2 would 8; This information is provided to assist the City in their review of the P<^joct. Qir primary focus was for the drainage/wetlaxxl considerations, taut we have also included a preliminary design for driveway and utility In cur opinion, the inprovements shorn will meet the requirements of the City end Mitershed regarding site drainage and wetland encroachment. ocntect me if you have any questions regarding this letter. Rogir A. Anderson, P.E. i. xns Lot Surveys