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RCNI) Permit INit.vnber 116 116
<br />iDescri2ti on — 'rhie- pirpir,:,cl lr.�ropcoses to oonsTruct a inew bid�U! rig aparkling 1r:xt on I xit �2 Biir,.)ck I of
<br />Clearwater Business Pairk in Centerville, KIM. It he ix-oposed proilect area i!s curreinlity i,ugwriied by
<br />the City of Centerdfle. 11he pirpJ1r,,,ct willi create- 2.6!ff, acires of lirinpeirvious surfaces and dhiiIurb
<br />3.410± acres ovendNll I he prr4ect discheirges,:saiah tolUll'ie,110 3 Main ll"irunll�,, and dUrnately to I alke
<br />1:31610eirthe ll',Psource �of Concern (lk(Z)% i he applicant Ihas sdtxnlltled a total ir.A $3,,750 ifcn,1the
<br />correspoirids to 2.5-5 acmm of nPwhredev6li:)peid irnlPeNiOUS SLIIIIM., and
<br />2.6-10 scres of land dlstt.,urb,,�ince.
<br />2.
<br />........................................
<br />Solis on site are primarily organic clays (HSG D) soils. Thus, infiltration is not considered feasible
<br />and the proposed BMPs are acceptable to meet the water quality requirement. The BMPs were
<br />constructed under permit 05-110 to treat storm ter run-off from the site, as indicated in the table
<br />below. The City is both the applicant and owner of the pond. As -built records of the stormwater
<br />pond were submitted for the NURP pond in 2008 verifying that the pond was constructed to plan,
<br />however applicant must submit evidence of maintenance or arrange to maintain the pond during
<br />the construction process. Based on District LIDAR, the blo-filtration basins were constructed,
<br />however as-builts must be provided to confirm the size. An acceptable maintenance obligation
<br />must be submitted (see Finding 7 for additional details).
<br />During a 2.54nch rain -fall event, the stormwater pond requires a dead storage volume of 75,490±
<br />cubic feet. The pond provides a total storage volume of 89,600± cubic feet thus providing
<br />sufficient storage. The stormwater pond has been designed to NURP standards and has
<br />remaining volume for future development. Outlet control structures from the pond have skimming
<br />devices capable of preventing oil and debris for the 1 -year event and controlling the 2 -year, 10 -
<br />year, and 100 -year event.. The pond has a riprap stabilized EOF at elevation 901 on the west
<br />side. The entire site drains to the NURP pond. The bio -filtration basins have been designed for
<br />to control only. The applicant has met all the Water Quality requirements of Rule C.6 and the
<br />design criteria of Rule C.g(d).
<br />The previously approved calculations used the NU RP pond, blofiltration basins and the approved
<br />impeMous area listed above to show compliance with District Rule C.7, These BMPs were,
<br />developed under prior District Rules which used TP 40 precipitation values in modeling. Current
<br />District Rules now requires applicants to submit modeling using Atlas 14 precipitation values.
<br />The existing regional star water BMPs have been constructed for the overall commercial
<br />development. The current project site is only a portion of the drainage area of the overall rate
<br />control calculations for the development. Modeling of the entire drainage area with Atlas 14
<br />values would be considered an unreasonable burden for the applicant. Analysis conducted by the
<br />....................................................... . ........ ........ . ................................ .. . ............. . . . . ............................................................................................ ... . ....................... . . . ...... . ................... . .. . .................................. ... . ... . ............................ . .............. . ...................................... .... . . ..... . . ......................................... . ...................................... ................................
<br />11--iloustoiri Engllirieering Il,inc P'alge 3 cU4 218/20V
<br />Off-site - South of
<br />Commercial Driver
<br />et
<br />Bia-filtration Basin B
<br />On-site — East property line
<br />NA - Rate Control Only
<br />...............
<br />..............
<br />Solis on site are primarily organic clays (HSG D) soils. Thus, infiltration is not considered feasible
<br />and the proposed BMPs are acceptable to meet the water quality requirement. The BMPs were
<br />constructed under permit 05-110 to treat storm ter run-off from the site, as indicated in the table
<br />below. The City is both the applicant and owner of the pond. As -built records of the stormwater
<br />pond were submitted for the NURP pond in 2008 verifying that the pond was constructed to plan,
<br />however applicant must submit evidence of maintenance or arrange to maintain the pond during
<br />the construction process. Based on District LIDAR, the blo-filtration basins were constructed,
<br />however as-builts must be provided to confirm the size. An acceptable maintenance obligation
<br />must be submitted (see Finding 7 for additional details).
<br />During a 2.54nch rain -fall event, the stormwater pond requires a dead storage volume of 75,490±
<br />cubic feet. The pond provides a total storage volume of 89,600± cubic feet thus providing
<br />sufficient storage. The stormwater pond has been designed to NURP standards and has
<br />remaining volume for future development. Outlet control structures from the pond have skimming
<br />devices capable of preventing oil and debris for the 1 -year event and controlling the 2 -year, 10 -
<br />year, and 100 -year event.. The pond has a riprap stabilized EOF at elevation 901 on the west
<br />side. The entire site drains to the NURP pond. The bio -filtration basins have been designed for
<br />to control only. The applicant has met all the Water Quality requirements of Rule C.6 and the
<br />design criteria of Rule C.g(d).
<br />The previously approved calculations used the NU RP pond, blofiltration basins and the approved
<br />impeMous area listed above to show compliance with District Rule C.7, These BMPs were,
<br />developed under prior District Rules which used TP 40 precipitation values in modeling. Current
<br />District Rules now requires applicants to submit modeling using Atlas 14 precipitation values.
<br />The existing regional star water BMPs have been constructed for the overall commercial
<br />development. The current project site is only a portion of the drainage area of the overall rate
<br />control calculations for the development. Modeling of the entire drainage area with Atlas 14
<br />values would be considered an unreasonable burden for the applicant. Analysis conducted by the
<br />....................................................... . ........ ........ . ................................ .. . ............. . . . . ............................................................................................ ... . ....................... . . . ...... . ................... . .. . .................................. ... . ... . ............................ . .............. . ...................................... .... . . ..... . . ......................................... . ...................................... ................................
<br />11--iloustoiri Engllirieering Il,inc P'alge 3 cU4 218/20V
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