Stormwater Facility Retrofit near 151st Pl SW (Hemlock Acres)

Description - Completed 2017

Snohomish County Public Works, Surface Water Management Division, replaced the existing detention facility located within the right-of-way of 151st Place Southwest within the subdivision of Hemlock Acres Number 16. The project replaced an existing 131-LF, 30-inch CMP detention pipe with a concrete vault having dimensions of approximately 161 feet long, 14 feet wide, and a 6-foot interior height. Portions of the pavement in 151st Place Southwest, including concrete curb and sidewalk, were removed and replaced to construct the vault. Existing landscape islands within the right-of-way were removed as part of the project to improve vehicular passage for emergency vehicles and large service vehicles.

The goal of the project was to replace the existing detention facility which was deteriorating and improve water quality and reduce flooding impacts in downstream portions of the watershed.

Additionally, Alderwood Water and Wastewater Division upsized the water main serving the fire hydrant within the subdivision to meet fire protection requirements. Alderwood Water & Wastewater contact and phone number: David McDonald (425-743-4605).


The project (PDF) was constructed in summer of 2017.


Signage and traffic control were provided to route traffic around the construction site.