10415 EVERGREEN WAY 2018-01-01 MF Import

08/19/7084 11:44 4253556809 JIEE FLOORS INC PAGE 02 Memorandum RE: Supplemental Drainege Information ragsrding Dwaync Lane's Everett 5uzuki Project - Flooding caused by the b�cking up of the detention pond for the euisting dcalesship. Reccipt of tha 1 etter f ram t he C iry d ated A uguat 4, 2004 is h ercby a clmowledged. Y ou h ave asked our office ro respond to thc questions raisai in the�etter. Thote could be several mitigating mattecs affecting the backup of watn• onto che pro{xrties on 105°1 and Olivia. This officc has lnvestigatcd several potential factas, but cannot defini!e1y statc that ane or the other is the cause of the backups. 71ust items wili be diacussed in detail in this Ictta, but most impo�tantly, the Lane Properties, LLC, has coopetated fully in the swdies and agteed ta install a parallel pipe sysoem fram Olivia weslward throuph their property a��d connect to an existing 18 inah pipe. This proposal will incrcase tht capacity by ]00-150%. Dway�e I,ane's h:5 gane to great lengths to cantrol the ntn-off on Oli.�a. Thc below statementt a*e some backgrounds on the project ns we currently lanow it: t. Thc purported 8-inch pipe is actuatly a l2-inch pipe and tuns from the end stall north of the service bays dimctly nprth to two [8-i�tch pipes md two catch basins. Both basins we�e buried and brought up to grade. 2, The l2-inch pips from 105'h and Olivia connected to the l2-inch pipe and was in placc whrn Olivia had several residences on the west side. This o:fice does not lrnow when this drain pipe was connected and when the service bay project wa; constructed, this offiee did not change any of the c�eisAng pipes. 3. 105° has wdagonr. a mejor transition from when the original pipes wete corestructed. Scversl developments were conshucted that conRibute volumes of water to IOS'" and Olivi�. Each of tkiose developmeuts were required ta conduct downstream analysi� as part of the draiaage reriew on thc projecfs and if problems, they wcTe requircd to fix them. 4. Tho areas that were flooded appcar to be on lhc low side of th�lou. With increased flow from the new curbs and gutters on 105"'onto thc storat rn: Oliv�a, it is entirely possible (though not proven•as menuoncd above)tfx pipes from Olivis onW the Lane property arc too under eapacity. Agein,the paratlel pipc sF.ould all�w+ate this situatian. 5. 'The on-sitc drainagc travels southerly into e wetpondlwater quality pond where the discha•ge drains north and eonnects to the existin$ 12-inch pipe from Olivia. The distancc is approximeuly 11� fcet v�esurly before the waur again tiuns noRh for about 100 [eet and wnnects t o the s ubje:t [8-inch p ipe which takes the w ater t o Evargreen Way. 6. This water r.iay contzibute to the :�ater problem an I05'" and Olivia. The parallel pipe from Olivia to the l8•inch should solve the problems noted,but caution is urged sintc the available headwatcr depths Aro lower than optimum. Sinccttly, Ted Trepar.ier Civil Engineer