9227 4TH AVE W 2024-08-12 - Laserfiche WebLink

Upstream Analysis From field observation and review of the available aerial topography, it appears that the site have no offsite flow. This project will not collect any offsite runoff. The site will be graded to direct runoff away from the structures and toward the east as in the existing condition. Refer to figure 4 for map of the surrounding area. There is no likelihood that the proposed project activities could impact upstream area with backwater conditions. Downstream Analysis The project site is within North Creek basin. From a field investigation and from field topographic mapping it was determined that in the existing condition the slopes on the site generally slope from west to southeast and stormwater currently sheet flows southeast towards an existing storm drainage system on Holly Drive. Runoff from the frontage of the project site drains south along the east curb line of 4t"Ave W until reaching a catch basin about 100 feet south of the project site. Flows continue in the drainage system in a series of 12in pipes and catch basins along 4t"Ave. W toward the south until merging with the drainage system along Holly Drive. Flows then drains toward the east to a drainage system along Holly Drive and continue until reaching Evergreen Way then crosses Evergreen Way through an 18" pipe and the system continues along the south side of Holly Drive. Flows then turn south along the west side of Dorn Ave. and continue through an enclosed system through a storage facility and then discharges into North Creek. MINIMUM REQUIREMENT NO. 2 - CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN Below is a summary of the applicable elements of the construction stormwater pollution prevention plan. A full detailed plan is prepared and attached a separate report. 1 : Mark Clearing Limits The first step in the "Construction Sequence" included on the clearing and grading plan sheets is for a surveyor to stake the limits of clearing and to have construction or silt fencing placed along the limits prior to any other construction activity. 2: Establish Construction Access The SWPPP calls for the proposed construction entrance to be installed as the second step after the staking of clearing limits. A detail is provided on the plans. 3: Control Flow Rates This project will retain as much existing vegetation as possible. In addition, Flow rates will be controlled by using SWPPP Element#4, sediment controls. 4: Install Sediment Controls This site and SWPPP proposes to construct a construction entrance and retain existing vegetation and install CB inlet protection to collect and contain the sediment on this site. Drainage Report—9227 4t"Ave W Everett,WA 98204 Nov. 10,2022 Page 11