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� �- <br /> 2717 Rockei�ll�r Av�nu� <br /> p O M E GA Ev�ntt, WA 95201 <br /> � ENGINEERING, IN�. azs.ss�.sszo <br /> tax 425.259.1858 <br /> February 2, 2010 p w ���3 —U � a� <br /> City of Everett <br /> 3200 Cedar Street <br /> Everett,WA 98201 <br /> RE: Drainage Letter for PSKC Medical Office Building. <br /> Dear Staff, <br /> This letter is intended to provide the necessary information to support the engineering plans submitted for <br /> this project. This site is located northwest of the intersection of Nassau Street and Pacific Avenue in <br /> Everett. The site had previously contained a structure which as already been demolished and the current <br /> site is cieared and covered with grass and brush. The site slopes from the southeast to the northwest <br /> and all runoff from this site is directed to the combined stormisewer system within the existing alley along <br /> the west side of this project. <br /> This project proposes to construct a new medicai office building with underground and surface parking. <br /> The roof area totals 5,945 sf with approximately 2,548 sf of new impervious surfaces for parking, drive <br /> lane, walks and the garbage enclosure. The runoff from the roof will be collected and tighlined to the <br /> combined storm/sewer system within the existing alley. Since the new surface parking and drive area is <br /> so small the drainage design for this project proposes to allow the runoff from these areas to sheet flow <br /> west and into the existing alley. The runoff will then flow north and will be collected approximately 100- <br /> feet in an existing catch basin which is connected to the existing stormisewer system within the alley. <br /> As noted above the roof area wili be collected and tightlined to the storm/sewer system. The runoff from <br /> the roof and footing drain system will be directed through a catch basin with a tee installed on the outfall <br /> to prohibit any vapors from the combined storm/sewer system from backing up into the new drainage <br /> system. A detail has been provided on sheet C3 of the engineering plans submitted for this project. <br /> Since this is such a small project and the existing site currentiy drains to the combined stormisewer <br /> system, no further water quatity or fiow control design is necessary for this project. The existing system <br /> will provide the required treatment downstream and no flow control is required wnen connecting to the <br /> combined system for a project this size. <br /> Thank you for takinq the time to review this project. Please feel iree to contact me with any questions you <br /> may have. N.�;^`;-'L4-u„��'',� / <br /> Sincerely���'.j���:"�::Ls,�'�rf`� <br /> +y l.'I\v ' `? �f <br /> :�I ~�`^ i•�gr}�:':�c:; J� � <br /> i � i <br /> �� /��� `� �' <br /> ,� .�� z : <br /> t.:. <br /> � � �'r��i.,. :��z�s ��' C <br /> Jo�eph�;5ltteU�rti'�:`:;:i.= y� <br /> Project En��r,�i���.��� <br /> :;- , <br /> ��-1�-:'!� c_ . ,�.c,» <br /> 1' _.. __... _�_'�-_.� <br /> I <br />