The purpose of the North Cottonwood Neighborhood Stormwater Improvements project is to upgrade stormwater conveyance along both sides of Hazel Lane from Sunset Street to Maplecrest Avenue (1,200 linear feet) and down the east side of Maplecrest Avenue (200 linear feet) to Seaview Drive. This project will complete the stormwater improvements identified in the Birch Bay Central North Subwatershed Master Plan and the Birch Bay Comprehensive Stormwater Plan for this neighborhood. It will also provide the final contributing area to the water quality treatment swale installed in 2013, as a component of the Cottonwood Neighborhood Drainage Improvements Project.
The existing drainage system consists of open ditches, driveway culverts and some extended sections of buried pipe that drain from west to east. Total drainage area conveyed by the system is 4.9 acres. Stormwater on the south side of Hazel Lane runs off as sheet flow toward Seaview Drive, resulting in extended periods of ponding and saturated soils through much of the winter. Much of the buried pipe is failing and conveyance is sluggish due to improperly installed driveway culverts, extremely low gradient and a generally poorly designed drainage system.The upgrade to the drainage system will improve stormwater flows, reduce drainage-related impacts to private property and county road systems, provide roof/downspout connections to the upgraded system and improve water quality by safely conveying the Hazel Lane stormwater to the existing water quality treatment swale.
Key improvement objectives: