2017-03-22 CC & WS Packet - Laserfiche WebLink

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RCWD Permit Number 16-116 1. Descridon —The project proposes to construct a new building and parking lot on Lot 2 Block 1 of Clearwater Business Park in Centerville, MN. The proposed project area is currently owned by the City of Cen%rvMe. The project will create 2.65± acres of Impervious surfaces and disturb 3.401 acres overall. The project discharges south to the JO 3 Main Trunk and ultimately to Lake Peltier the Resource of Concern (ROC). The applicant has submitted a fatal of $3,750 for the application fee, which corresponds to 2.5-5 acres of nowiredeveloped Impervious surface and 2.5.10 acres of land disturbance. 2. Stormwater — The applicant is proposing the BMPs as described below fur the project • ,N1 Impervious Ares 1.94 11.88 11.94 10.00 19.09 7.$5 is 1 1, �Y. � � .a.'i`,R . - 24"." Y,.� r F' �Y �`Y� NURP Pond Olf4ft - South of 75,490 8916001 901 Commercial Drive cubic feet Bio -filtration Basin B On4ft — Fast property One NA - Rate Control Only 94.3 Blo41ttra8on Basin C On -s ie —West property One NA - Rate Control Only 904.3 Solis on site are primarily organic days (HSG D) sobs. Thus, Infiltration Is not considered feasdble and the proposed BMPs are acceptable to meet tine water quality requirement. The BMPa were constructed under permit 05-110 to treat story water runoff from the site, as Indicated in the table below. The City Is both the applicant and owner of the pond. AB -b R records of the atormwafer, pond were submitted for the NURP pond in 2008 verifying that the pond was constructed to plan, however applicant must submit evidence of maintenance or arrange 110 maintain the paced during the construction process. Based on District LIDAR, the bio4ifthion basins were 0 r1GtruCted, however as-bullts must be provided to confirm the size. An moble maintenance obligation must be submitted (see Finding 7 for additional details). During a 2.54nch rainfati event, the stormwater pond requires a dead storage volume of 75.4901 cubic feet The pond provides a total storage volume of 89,6001 cubic feet thus providing suMcient storage. The stormwater pond Inas been designed to NURP standards and has remaining volume for future development Outletcontrol structures from the pond have skimming devices capable of preventing oil and debris for the 1 -year event and controlling the 2-yesA 10 - year, and 100 -year event. The pond has a riprap stabilized EOF at elevation 901 on the west side. The entire site drains to the NURP pond. The bio4 thatlon basins have been designed for rale control only. The applicant has met all the Water Quality requkanments of Rule CA and the design whate of Rule C.9(d). The previously approved calculations used the NURP pond, biofiltration beams and the approved Impervious area listed above to show compliance with District Rule C.7. These BMPs were developed under prior District Rules which used TP 40 precipitation values in modeling. Current District Rules now requires applicants to submit modeling using Atlas 14 precipitation values, The existing regional stormwater BMPs have been constructed fior the overall commercial developrnenL The current project site is only a portion of the drainage area of the overall rate cor" calculations far the development. Modeling of the entire drainage area with Atlas 14 values would be c onsWered an unreasonable burden for the applicant. Analysis oordnrated by the Houston Engineering Inc Page 3 of 4 2/8/2017 21 Impervious Ares 1.94 11.88 11.94 10.00 19.09 7.$5 The previously approved calculations used the NURP pond, biofiltration beams and the approved Impervious area listed above to show compliance with District Rule C.7. These BMPs were developed under prior District Rules which used TP 40 precipitation values in modeling. Current District Rules now requires applicants to submit modeling using Atlas 14 precipitation values, The existing regional stormwater BMPs have been constructed fior the overall commercial developrnenL The current project site is only a portion of the drainage area of the overall rate cor" calculations far the development. Modeling of the entire drainage area with Atlas 14 values would be c onsWered an unreasonable burden for the applicant. Analysis oordnrated by the Houston Engineering Inc Page 3 of 4 2/8/2017 21