6.9. - 6.12. SR 09-17-2001 - Laserfiche WebLink

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opposite the main access to Elk River Crossing off of Tyler Street. In fact, at this location the median is not only broken but a left turn lane into the Trott Brook Farms South property is already constructed. The internal road system provides two access points to the property immediately to the south. One is approximately 200 feet off the east boundary, and the other is approximately 450 feet away from Tyler Street. These should provide adequate road access for an intemal circulation as the property to the south develops. The Grading, Drainage, and Erosion Control Plan submitted is at a scale of 1"=100'. It is very difficult to do a detailed review on a project this size at that scale. We would recommend that the Developer submit a 50-scale grading plan. Generally, the items we noted in the review of the small scale Grading Plan is additional elevations need to be added to indicate the tops of ponds and overflow elevations to determine that storm drainage will not endanger any of the buildings. There are also significant areas where the yard drainage does not follow rear lot lines. In these areas additional easements will need to be granted on the final plat. There is also a significant amount of storm sewer piping along rear lot lines. In some instances, simply regarding the area could eliminate this pipe. In other areas, the main line storm sewer should follow the street rights-of-way with catch basins and leads into the rear yard areas. A more detailed drainage review will be possible when a larger scale Grading Plan is submitted. There is a faidy sizable wetland located in the north central portion of the site. Portions of the wetland are proposed to be filled for construction of roads and other grading on the site. No wetland delineation was provided with the submittal package. However, it does' appear that a delineation has been done. This project will need to go through a Technical Evaluation Panel. The wetland process will need to be concluded prior to any final approvals for this project. o Review of the drainage calculations indicates that in concept the design is reasonable. However, there are a number of significant issues that will require the storm sewer design to be redone and possibly the ponding areas enlarged. Specifically, the calculations allow 12.9 cubic feet per second to discharge from the site after development. In reviewing the storm drainage calculations for the Tyler Street trunk system, there is only 4.9 cubic feet per second allowable from this site. There are also some minor issues with the tops of the ponds versus the high water elevation of the ponds. The storm sewer model does not indicate enough freeboard between the high water elevation and the top of the pond. We will work with the Developer's engineer to revise the storm sewer calculations. The sanitary sewer system to serve the proposed development consists of an extension from the trunk line in Tyler Street at the southwest comer and laterally sized sewer lines throughout the development. Water service for the proposed development will consist of a connection to a stub constructed by the Elk River Municipal Utilities near the northwest comer of the development, off of the high pressure portion of the water system. The water lines are looped through the development. The second connection will be further east along CSAH 12 near the main entrance to Trott Brook Farms. The Utility Plan for Trott Brook Farms South shows the watermain terminating at their east boundary near CSAH 12. In fact, the extension over to the stub across CSAH 12 will need to be made at this Howard R, Green Company CONSULTING ENGINEERS Ltr 822-01 McPherson.rev Page 2