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� �� � <br /> D � � _ <br /> c � �� �: �,_ � <br /> � U <br /> March 8. 1991 / A�Q�B�yRpq � , ; �:.., P.S. <br /> TJy I <br /> / i c � ( ....,.. ...._............... ....... . <br /> , '1 � ' CITY OF EVERETT <br /> ��.� � ��• � BfdR. Permi�Counter <br /> Ms. Jane 2immerman � � <br /> City of Everett <br /> Public Works Department 1 �� I ( <br /> 3200 Cedar Street i �! . <br /> Everett, WA " `� <br /> Dear Ms. 2lmmerman: <br /> We are submitti. � the revised storm retention system and <br /> calculations for your review. We have modified the system <br /> rate 9forelAlder oodns soils f af p 15 minutes9 pererinchtiin <br /> accordance with your requirements. The calculations are <br /> orqanized ae follows: <br /> Time of concentration. <br /> Hydroqraph, 25 year. <br /> Storm retention system data. <br /> Routing data: 25 year intensity, 24 hour storm through <br /> the system: base elevation = 662.50; top elevation = <br /> 665.50 maximum elevation of water with 25 year storm <br /> is 665.12. Size of system is 11 ft wide by 16Cif long <br /> by 3 ' deep. porosity of the gravel is 0.30. No <br /> storage is considered for the pipe. <br /> We have also added the vault and oil separator as requested. <br /> Maximum ponding time is 8.7 hours (see print outl . <br /> City notes have been added to the plans for the infiltration <br /> s�!stem. <br /> The other items in your letter have been resolved by phone. <br /> Please feel free to call if we may answer any additional <br /> questions you may have. <br /> Sincere . <br /> � <br /> Donald K. Scarb ry, P.E. . <br /> Manaqer Civil gineerinq <br /> Nelson-Bourd es Inc. , P.S. <br /> 90145C <br /> NELSON-BOURDAGES, INC.. P.S. <br /> Com.ulting F.ntiin��en • I IAI I �1�: 174�1� StrecL Suite 230 • Kvkland. WA 9P034 • 7061873��5M�7 <br /> PAX 12WI H�f1-i1D�7 <br />