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Review File: Pearson Place <br />Preliminary Plat <br />Engineering Review <br />June 27, 2017 <br />Page 2 of 2 <br />9. Revise the table to show 2% minimum grades on all lots. <br />10. Provide a minimum of 3 deep borings in the area of the house pads. <br />11. Minimum basement elevation must be determined using the guidance prepared by Barr <br />Engineering. A copy will be provided with this review letter. <br />12. Show potential well locations on this plan. <br />13. Provide roadway ditch profile and cross sections for the east side of Bowers Drive. <br />14. All runoff from the houses and driveways must be directed to the infiltration basin. <br />15. Additional sheets will be required: Detail sheet, SWPPP sheets (must conform to the <br />Construction Stormwater Permit requirements including listing the designers training <br />information and erosion control material type and quantity to be used on the project. <br />Stormwater Summary: <br />1. The infiltration basin receives runoff from all storms. It must be designed to empty within <br />48 hours after the 100 year storm. Our calculations indicate the basin does not drain in 48 <br />hours. Revision is required. <br />2. The proposed drainage map must be revised to show the drainage area boundaries in a <br />different line style from the project boundaries. <br />3. Drainage area P2 should be revised to include the front and driveway of all houses. <br />4. The summary table states there is a reduction in flow to the south east. <br />5. This project is adjacent to a plat that was approved in 1949, prior to any stormwater <br />regulations. Runoff from the project must be attenuated prior to reaching the existing <br />street. This project will need to meet the Lower Rum River Watershed Management <br />Organization requirements for volume control, water quality and rate control. The volume <br />reduction requirement is infiltration of the first 1 inch of runoff from new impervious <br />surfaces. The infiltration basin must be enlarged to account for existing impervious areas <br />that drain to the new basin. Required rate control is limiting developed runoff rates to the <br />existing rates for the 2, 10 and 100 year storms. Water quality standards are met by <br />providing wet detention equal to the 2.5 inch storm and removing 60% total phosphorus <br />and 90% total suspended solids from the discharge. <br />