6400 MERRILL CREEK PKY 2018-01-01 MF Import

nGW[JP�� G�i � C'c �H C.� �yc�+�tCy! �}� 'il�v f,�l}aM cr '�'LLQ �c��.� r�.0 cY'1- 'i L�( _ • �---'� .Sc.,Hnwts}- r�=rn�� c.F �f"�.c S�!-c m�� la.c arcz� l-� �,Ic -1cc. . prwr�l.�d �l-t-,a�� , �_-- . "{w .¢I�m..�raFe Wa:, a.pp,-�prial-t �nol i-L,.c zpPlrcdnd� c�. �cl 5b.ow -f-L, Trf" . .. ._ �rc.5ion Wc.,lol n��f-cCct+� Infiltration baaini ,�C k��ec'^ 't�`�' cliscl-�S.c� it seems that designing a small infiltration basin, to be �,,.,� ;,,,cl located i.mmediately west of the parking area, miqht ba �_� m� „ better suited to maintaining the hydrology in the nativa/� (� M o� grnwth areas than a direct discharqe of stormwater✓ ncwder M; II cr.e.c �. The difficulty comes in sizing the basin. It would ba as a ;es..� •�- satisfactory to the City if the applicant followed the �F -� i.�,c followinq procedure: (u� ��m� �n -� �n^ F�m e o w��.r nu+r-,<-� ) . �,s`��^ `, �a��' ancl r�n��F � 'n� •{6+A � � 1) Estimate the volume of infiltration, durinq the 6 S r,r•� ��, month, 24-hour storm, for that portion of the eite Sl,�r" �„-n�' � draining west that will be altered by development -I��l 01� �`r fil�-' u �I� P� � a) usinq the SBUH or similar method, determine 5�^�' �F as � �drA�' the volume of runoff from the area of �f ru'v �o/��^F �„M interest using the existing vegetation type ��u�^! �� and aat.i.ua SO11S. iak� 'f�h�s �wrnher �s 'f'1tiE �ol�rnc o� �lu " '�e .}ypc p r��oFf ancl ;� 1=.t }-rai-io� on -Ihe s.t2. ��„�d � �---deter-mine—the volume—of—r-ur�of-f—€r-e�--tha—same J`caJ�,�, a��Sinq-the-same-vege�ation-type;bu�-tYPe C�SIIbtT'a�-c—v@- ••� h frnm �tdllt�_3,—Take-th-i�s numbe�-as-�he-fn€i�btr-�t�:on-volume. � 2) Determine the area of paved surface that would generate a volume of runoff equivalent to the r�no� F '� infiltration volume. Hydrologically isolate this amount of area and route it to the infiltration basin. x 3) Size the basin to completely infiltrate the 6 month, 24-hour storm volume from the paved surface xouted to the infiltration basin. �. 4) Provide an overflow at the peak storage elevation ��'�� that would route greater volumes to the nain G .r��tl, , 24 hr treatment system. �,}�,.�, ) . When calculating the discharge from the pond, the City asks � that the discharge be based on the plan area of the pond only. City standards call for at least 3 feet of relatively permeable soil to be present between the bottom of the �" infiltration system and the seasonal high groundwater elevation, bedrock, hardpan or any impervious layer such as clay. Any soil logs that have been taken on the site should be submitted to demonstrate that this requirement is beinq met. �