Laserfiche WebLink
Planning Commission <br />June 26, 2008 <br />Page Three <br />4. For the existing Subcatchment, soils information and a more detailed <br />description of the curve number proposed should be provided. The time of <br />concentration used should also be reviewed and more detailed information <br />provided. The time used appears to be low compared with the time used for <br />the smaller individual Subcatchments in the proposed conditions. <br />5. For the proposed Subcatchments it appears that some have a composite <br />curve number. A breakout of the areas within the Subcatchment and <br />corresponding curve numbers should be provided. In addition, the time of <br />concentration used for the proposed Subcatchments should be reviewed and <br />more detailed information provided. The areas vary in size considerably and <br />it appears that the numbers should vary in time. <br />6. For Pond DS15 the primary outlet noted on the plans is a 15-inch pipe with <br />an elevation of 948.91. The secondary outlet elevation noted on the plans is <br />also 948.91. The discrepancy with the plans and the calculations should be <br />resolved. <br />7. For the Stormtech ponds documentation should be provided for the <br />exfiltration rate that was used. Proposed calculations should also be <br />provided that do not account for any exfiltration. The comparison of existing <br />and proposed rate of discharge will be compared using the calculations that <br />do not account for exfiltration. <br />8. Storm pipe calculations will be required to be submitted for review and <br />approval. <br />9. A maintenance schedule will need to be provided for the Stormtech ponds. <br />General Comments <br />1. There is over one acre of disturbance for the redevelopment and therefore a <br />Ramsey Washington Metro Watershed District and National Pollution <br />Discharge Elimination System (NPDES) permit will need to be obtained. <br />Documentation of the permit approvals will be required prior to any work. <br />Please contact me if you have any questions regarding the above information at (763) <br />780-0450 ext. 13. <br />Sincerely, <br />ELFERING & ASSOCIATES <br />~_ ~~ <br />Lee Elfering, P.E. <br />City Engineer <br />cc: Bill Dircks, Public Works Director <br />Ltb062608-PC <br />10062 Flanders Court NE, Blaine, MN 55449 -Phone: (763) 780-0450 -Fax: (763) 780-0452 <br />