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• Ms. McPherson June 19, 2000 Page 2 B. Preliminary Grading Plan 1. Lot 1 Block 1 has relatively steep access off 173rd Avenue, is only one acre in size, and a portion of the southeast corner of the lot is occupied by an existing gas line easement. We question whether or not this lot is buildable. 2. In the Phase I condition, a large retention pond is proposed to hold the storm water runoff. This pond has no outlet and will operate through infiltration. No drainage calculations have been provided at this time. The side slopes on this pond must be 4:1 or flatter or the pond needs to be fenced. In the Ultimate scenario, the pond is reduced substantially in size and an outlet is shown under the railroad tracks to the City ditch on the east side of the tracks. It is acceptable to provide an outlet under the tracks; however, a pond must be provided prior to outletting that handles both the sediment control for the entire area plus restricts the discharge under the railroad tracks to the pre-existing conditions for the property. The City ditch on the east side of the railroad tracks flows ultimately to a large pond constructed with the East Elk River improvements. This pond has not been sized to accept unrestricted flow from the K&L Addition. Storm drainage calculations will be needed also for the Ultimate condition. We would recommend that these calculations be done with • Phase I so an adequately-sized area can be set aside for ponding in the future. 3. An emergency overflow location and elevation should be shown near the catch basins in Vance Street, such that in a case where the catch basins are plugged, water will overtop the curb and flow into the pond. 4. The typical street section on the preliminary grading plan should have B618 concrete curb and gutter instead of B612. The bituminous base course should be two inches in thickness rather than an inch and a half. 5. In most other commercial/industrial areas, concrete sidewalk is a part of the street section. We question whether or not concrete sidewalk should be included in this addition. C. Preliminary utility plan 1. The Phase I preliminary utility plan shows water main looped through from 173rd Avenue to the frontage of road of TH 10. Easement will be needed for this looping outside of the proposed Phase I plat. The water main should be a minimum eight inches in diameter with six-inch pipe used for hydrant leads. 2. Hydrant spacing in commercial/industrial areas is required to not exceed three hundred feet. There will be additional hydrants needed to maintain this three hundred-foot maximum spacing. 3. The sanitary sewer is shown in the Phase I preliminary plat to be extended from 173rd Avenue up Vance Street just beyond the plat boundary. In the Ultimate scenario it continues around Vance Street to the TH 10 frontage road. In the Phase I scenario, sanitary sewer should be added to provide service to Lot 3 Block 2. In the Ultimate scenario, sanitary sewer needs to be added to provide • service to Lots 12 and 13, Block 1. O:\PROJ\809020J\Ltr-061900-McPherson.doc Howarc R. Green Company CONSULTING ENGINEERS