8615 7TH AVE SE 2021-02-26 - Laserfiche WebLink

B. DOWNSTREAM ANALYSIS Runoff from the proposed disturbance area of the existing site drains to the north or south of the existing church. The runoff is collected by yard drains or CBs and then conveyed via a piped system to the north or east. Runoff that drains south of the church is conveyed east and appears to leave the site through the existing drive/access that connects to 9th Ave SE. The runoff that drains to the north is collected by yard drains or CBs but the off- site discharge point from this system could not be located in the field. However, the downstream connection point for this project will not change as a result of this project since the runoff from the new impervious surfaces will connect to the existing collection/conveyance system on-site. Based on a review of the available conveyance as-built information on the City of Everett Web-site it appears that all runoff from the buildings and pavement around the existing church is collected and conveyed to the east where it leaves the site drains to the east and is collected on-site and leaves over the eastern property line. Depending on which off-site conveyance system the runoff is connected to all runoff combines approximately 500-feet after leaving the site within the 9th Ave SE R/W. The runoff from there flows east through RNV and private property within a piped conveyance system and eventually to E Xavier Way and ultimately to a stream channel located between West Dr and E.Xavier Way that flows north and under SR 526. Since the new impervious surfaces total only 2,245 sf there is no expected impacts to the on-site or downstream drainage systems. During the site visit and review of the identified downstream system, no portion of the system appeared to be inadequate. • • Zillah 2-Lot SFR's 18-0605 June 2018 Page 6