Dam Safety 2018: Masonry Dam and Cedar River Watershed Field Trip

When: Thursday, September 13; 12:00 pm - 6:00 pm

Registration Fees: $95 per person includes motorcoach transportation, guided facility tours, box lunch and beverages.

Background & Project Overview: The Cedar River Watershed and Masonry Dam are located 35 miles southeast of Seattle. The 90,638-acre watershed supports a diverse ecosystem and provides about 70% of the drinking water to 1.4 million people in the greater Seattle area. From the Cedar River Watershed, melting snow and rain drain to the Chester Morse Lake and the Masonry Pool reservoirs created by the Masonry Dam. Listed in order from upstream to downstream, the project facilities consist of a roller compacted concrete (RCC) dam (Overflow Dike), a 210 foot high cyclopean concrete gravity dam (Masonry Dam), and a power tunnel and penstocks for transport of water to the powerhouse located approximately 2 river miles downstream of the Masonry Dam. RCC dam, (overflow dike) splits the reservoir at lower water elevations between Chester Morse Lake and the Masonry Pool. This dam helps minimize water losses from the Masonry Pool due to seepage through the glacial moraine forming the right abutment during times when water storage is more important.

Below the powerhouse, the water is released back into the river and continues flowing to the Landsburg diversion dam. At Landsburg, a portion of the water is diverted from the river into two large pipelines which run over seven miles to Lake Youngs in Renton. From Lake Youngs, water is pumped a short distance to the Cedar Water Treatment Facility. At Landsburg the water is screened and chlorinated on the way into the pipelines. Seattle Public Utilities built a fish hatchery at Landsburg as part of the Habitat Conservation Plan.

This 2.5-hour bus tour includes driving through the historic townsite of Cedar Falls, walking across the Masonry Dam, seeing Chester Morse Lake, and visiting the RCC dam and the Morse Lake Floating Pump Stations, which are deployed in times of drought. Along the way, your guide will share stories and pictures. Ability to walk up to 1/4 mile across uneven surfaces is necessary on this tour.

Itinerary: 

12:00 pm – 1:00 pm Travel from WSCC to Cedar Falls Education Center. Attendees will eat box lunches on the bus during the drive.

1:00 pm – 1:45 pm Informal info session on history of the watershed development and points of interest.

1:45 pm Re-board motorcoach for facilities tour

2:00 pm – 4:45 pm Cedar Falls Watershed Facilities Tour, including Cedar Masonry Dam, City Light Powerhouse, floating Morse Lake pumping stations and more.

4:45 pm Return to Cedar Falls Education Center

5:00 pm – 6:00 pm Travel and return to WSCC

Safety and Security Requirements: Participants should wear sturdy walking shoes (no sandals) and long pants. The air temp in the watershed could be as much as 20 degrees warmer than in downtown Seattle, so please wear layers and bring sunscreen, sunglasses and hats.

Special thanks to our sustaining members