Pacific Estates Culvert Improvement Project

Bog overhead capture.PNG

Project Description

The Pacific Estates Bog is located within the Pacific Estates neighborhood in Sammamish, Washington, near the cross streets of 229th Ave NE and NE 21st Pl.  This sphagnum bog accepts large amounts of stormwater from various streets, neighborhoods, and other ponds in the north half of the City of Sammamish, providing water quality treatment and storage.  The primary stormwater inlet to the bog, through which most of the water passes, is a 48-inch diameter corrugated metal pipe (CMP) culvert at the bog’s southwest corner.  The 48-inch CMP is approximately 155-feet in length. It originates from a stormwater catch basin in the intersection of 229th Ave NE and NE 21st Pl, traverses northeast, and outfalls into the Pacific Estates Bog. The pipe is located under a park which is owned by a local homeowner’s association; the City owns a utility easement through the property.

During heavy storm events, the ditch along the southwest corner of the intersection backs up and overtops NE 21st St due to an undersized conveyance pipe or a tail water condition. The water floods the intersection and flows onto an adjacent property where it ponds in the driveway and garage. The City wishes to address flooding in this area.

This project will utilize hydrologic and hydraulic modeling to investigate current and future stormwater inflows and culvert capacity and will design an appropriate solution to reduce the flooding in this area. Options to be explored may include, but shall not be limited to, replacement of the current 48-inch CMP with a larger-diameter pipe, installation of a second culvert in parallel with the 48-inch CMP, and/or drainage system optimization in the Pacific Estates neighborhood.  The consultant will then provide construction drawings, specifications and cost estimates to the City for the selected option.


Project Updates (updated July 2, 2018)

The City has selected Osborn Consulting, Inc., to assist with engineering design. We expect to kick-off the project in August 2018. 



April 2018 – City sends out Request for Qualifications (RFQs) to select consultants

May 23, 2018 – Statements of Qualifications (SOQs) due to the City

June 2018 – City interviews with consultants, contract and scope of work are finalized

July 17, 2018 – Contract award by City Council

August 2018 – Project Kick-off

Fall-Winter 2018 through Spring 2019 – Engineering design, permitting, and community outreach

Summer 2019 – Construction of culvert project


The estimated, combined design and construction costs for this project are between $200,000 and $250,000.


Staff Contact