10632 7TH AVE SE 2025-07-28 - Laserfiche WebLink

OFF-SITE ANALYSIS I UPSTREAM ANALYSIS Based on a site visit and survey data there appears to be offsite flow onto the site from the northern offsite extension of North Creek. Water enters the site near the northwest corner of the site via the creek bed and exits at the southwestern corner of the site via the same stream bed.No water leaves the banks of the stream under ordinary flow conditions. There are no other offsite areas tributary to the project site's drainage with the exception of Iapproximately 0.11 acres of existing half street right-of-way. The proposed development will not change any upstream drainage course or pattern and no impact on upstream drainage is anticipated. DOWNSTREAM ANALYSIS The downstream for Basin 1 relative to this project is to the east of the project site and consists of runoff that is collected in drainage system within 7th Ave. SE and flows south within the 7th Ave. SE right-of-way before entering a grass swale located on the southern side of l 10th Place SE and drains to the east. Compared to the existing stormwater from Existing Basin 1, the developed Basin 1 includes approximately a 1/3rd smaller amount of impervious area with very little change to the downstream drainage courses or patterns; therefore no impact is anticipated to the downstream drainage. The downstream for Basin 2 relative to this project is to the west of the project site and consists of runoff that is collected in a wetland that flows to an onsite portion of North Creek near the sites west boundary.North Creek flows south until it reaches the Sammamish River. Stormwater from Basin 2 will be infiltrated and there will be no change to the downstream drainage courses or patterns,therefore no impact is anticipated to the downstream drainage. The wetland on the west side of the site is fed by North Creek, with a small amount of storm drainage infiltration water from our site. 1 I 1 6 1