4th St NW Storm System Upgrade

PROJECT BACKGROUND

This project will install a new large-diameter (36"-42") stormwater main, rerouting and connecting the downtown drainage basin to the existing outfall to the Puyallup River at 4th St. NW (North of River Rd).  The existing downtown drainage basin drains to 4th Ave SW and out to the 15th St. Outfall to the Puyallup River.  The existing conveyance is shallow and lacks capacity and water quality treatment features. 

This project addresses a few major issues:

     (1)  Flooding.  The current lack of capacity causes flooding in several locations throughout the 4th Ave SW tributaries of the downtown area, during moderate and large rain storm events. 

     (2)  Water Quality:  Much of the downtown area was developed prior to water quality standards.  Currently stormwater from large areas of the downtown area, are discharged into the storm system and then ultimately to the Puyallup River.  This project will facilitate redevelopment of the downtown area, by providing a "Direct Discharge" to the Puyallup River.  Developers will not have to provide for very costly and prohibitive flow control requirements, which will make redevelopment feasible, in more cases.  The redevelopment will trigger Water Quality requirements, which would address the current lack of water quality features.

     (3)  Downtown Economic Development:  As stated above, current flow control requirements are a barrier to downtown redevelopment.  Flow control facilities (i.e. ponds, vaults, etc.) are very costly in an urban environment.  This project will remove some of those barriers by providing capacity to a Direct Discharge to the Puyallup River.  Basins that directly discharge to a flow control exempt waterbody (Puyallup River in this case) are exempt from flow control standards.  This will make redevelopment more feasible.  

The overall project is broken down into 5 phases (Phase N-1 through Phase N-5)