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rd.), • Howarc R. Green Conoany July 19, 2001 File: 815030)-0240 Mr. Scott Harlicker Senior Planner City of Elk River 13065 Orono Parkway P.O. Box 490 Elk River, Minnesota 55330-0490 RE: HILLTOP WOODS ESTATE-2ND ADDITION Dear Mr. Harlicker: As requested, we have reviewed the submittal for the Hilltop Woods Estate-2nd Addition. The submittal package consisted of a preliminary grading plan, preliminary plat, and preliminary on-site wastewater treatment plan, all prepared by John Oliver and Associates. Also submitted was a Preliminary Evaluation for the On-site Sewage System dated June 2001, also prepared by John Oliver and Associates. Based on our • review and comments heard at the staff review meeting, we would offer the following comments: 1. No storm drainage calculations were submitted. The concept shown on the preliminary grading plan shows storm water being conveyed to catch basins and then to two holding ponds located in Outlot B. Flow arrows indicate that the southerly pond will overflow to the northerly pond, which will ultimately overflow to the land to the north. Drainage calculations will have to insure that water does not discharge from the site at a greater rate than before development. It is also questionable whether or not the storm water discharging from the site to the north can be at a concentrated location if the existing condition is spread out along the northern perimeter. 2. The on-site treatment design that was submitted was very general in nature and did not include any soil borings. Therefore, it did not include a detailed final design on the system. A final design will have to be done after soil borings are taken and submitted for review and approval. It should be noted that the proposed on-site sewage treatment facility is located in Outlot B along with the storm water detention ponds. Care will have to be taken to insure that there is no possibility of the ponds overtopping into the treatment facility area. Total flow expected in the treatment system is well below the 10,000 gallons per day requiring a Minnesota Pollution Control permit. 3. The grading plan indicates that several of the lots have very flat driveways. There are even a couple of lots, Lots 5 and 6, Block 1, where the house pad is below the street elevation. We would recommend that the grading plan be • adjusted to raise these two sites so that the house pad is above the street elevation and to verify the driveway grade on each of the remaining lots. O:\P ROJ\815030j\0240\Ltr-071901-Harlicker.doc 1326 Energy Park Drive • St. Paul, MN 55108 • 651/644-4389 fax 651/644-9446 toll free 888/368-4389