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� <br /> • • ORONO COUNCIL MEETING HELD JUNE l, 1976 Page 2 <br /> , In general, any development of the site which RYAN CONSTRUCTION <br /> requires the installation of hardcover, will Super Valu Store <br /> �increase the runoff to the Kelly Avenue area. (Continued) <br /> I'herefore, any measures that may be taken to <br /> a reduce the increase in runoff would be beneficial. <br /> We would therefore recommend that the building be <br /> • constructed such that rainfall onto the roof area <br /> • be retained to a depth of 3 to 4 inches on an <br /> average, and that this rain water be held and <br /> � normally be released by evaporation from the <br /> roof itself. A roof drain should be incorporated <br /> � into the design of the building, however, to release <br /> stored water in the fall of the year to prevent the <br /> � build up of extreme amounts of ice on the roof, and <br /> also to provide room for the storage of precipitation <br /> r during the winter months, thereby reducing the spring- <br /> S time runoff problem. <br /> � Temporary storage of water on the parking surface seems <br /> to be impractical due to the slopes encountered on the <br /> � site, and would at any rate, provide no positive benefit <br /> unless an outlet from the Kelly Avenue drainage area was <br /> � constructed. We would recommend however, that runoff be <br /> directed through storm sewer conduits from the parking area <br /> r to the low area to the south of the building, as an alternative <br /> • to overland drainage. 6Ve feel that the potential for erosion <br /> on the steep slopes proposed would be thereby decreased. <br /> � Any storm conduits should be designed and constructed in <br /> �ccordance with the P4innehaha Creek Watershed Districts' <br /> � requirements. <br /> � The grading plan calls for the seeding of the graded slope <br /> areas to the south and west of the proposed structure. <br /> � These areas as shown would be sloped to a maximum of 1 foot <br /> vertical to 2 feet horizontal. Due to the difficulty in <br /> � establishing ground cover on slopes of this steepness, <br /> we would recommend that all areas south and west of the <br /> � building which are distrubed should be restored by sodding <br /> • and staking of the sod. <br /> � The grading and construction of the parking areas will <br /> require modification of the existing sanitary sewer <br /> � and watermain presently in place on the site. The <br /> sanitary sewer manhole casting directly north of the <br /> � building will have to be adjusted to the finished parking <br /> lot elevation. In the area to the southeast of the <br /> � proposed structure, proposed grading will require <br /> • excavation above the existing watermain. It is our <br /> recommendation that the watermain be removed and <br /> � reinstalled with a minimum of 7 1/2 feet of cover over <br /> the pipe to prevent the freezing of the line. <br /> • End of letter (Continued) <br /> � <br /> f <br /> � <br /> � <br /> � <br />