(Courtesy of Sparks Magazine)
Written by Eddy Haw, Electrical Crew Chief, Public Utilities & Jarrod Hamlin, Superintendent, Valley Electric
Chester Morse Lake is located in the upper region of the Cedar River watershed in Washington State. The lake is the major water supply storage reservoir for Seattle Public Utilities’ (SPU) which powers a 30-megawatt hydroelectric facility. In addition, it is the main source of water for the Cedar River which supports a large fish population and for which SPU has in-stream flow agreements to maintain certain flows to the river. The general operating scheme is to retain part of the high runoff during winter and spring so that the elevation of the lake rises to a maximum of 1,563 feet (above mean sea level) by the end of May. Typically, SPU withdraws water from the lake between early June and the end of October to deliver water to the regional water system and to maintain instream flows.
In 2002 the channel was dredged and the discharge dike rebuilt raising the elevation to 1,538 feet, which is now the lake elevation below of which pumping is required. Pumping during low reservoir levels conditions is presently accomplished with two barge-mounted pumping plants that have a total of 28 pumps and a combined pumping capacity of 240 mgd. These pumping plants were a temporary measure when installed in 1987 and have not been replaced. The pumps are driven by electric motors that are powered by shore-based mobile 1.5 MW generator sets. When it is determined that the reservoir elevation will decline below 1,538 feet, mobilization of the pumping plants is initiated. Mobilization involves towing the plants to established locations in the lake, anchoring them, connection to underwater discharge pipes and power supply cables, and installing stop logs at the discharge dike.
The goal of the new Chester Morse Lake Pumping Plant Project is to replace the old system to provide reliable access to water stored below the level at which gravity flow is not possible – currently elevation 1,538 feet. Seattle Public Utilities awarded the GCCM project to Orion Marine Group (Tacoma, WA) for the installation of an upgraded drinking water pump station on Morse Lake. Onsite construction was to begin in June of 2015. Valley Electric (Everett, WA) was the electrical contractor for the project, performing preconstruction and construction services for the duration of the project.
Team Collaboration & Ingenuity
On a hot June Thursday afternoon, in a 100 year-old house nestled up in the Cedar River Watershed, Valley Electric, SPU and the Orion Marine Group met for their weekly preconstruction meetings. The recently awarded 9-month project was about to begin, the permanent installation of a unique, new floating pump station 5 miles into the watershed, floating on the lake. SPU placed the project on hold until the end of the year! In 2015, Seattle was experiencing an unusual drought with water levels at a record low. With no snow pack from the previous winter, and water supply projected to drop without replenishment, it was forecasted the City of Seattle would be out of water by September 2015. A collaborative, temporary solution was needed to serve 1.25 million people in Seattle with 240 million gallons of water daily through the end of summer. SPU tasked the team to develop a creative design and installation plan which allowed for the watershed to pump water with their newly purchased pumps by mid-September 2015 to pump water to the city. (Several weeks later, the team was asked to get the (2) – 35 year old existing pump plants operational as well in support of the temporary pumping activities.) The SPU-Orion Marine-Valley Electric team was up for the challenge.
The floating pump station houses (4) – 4,160 volt 250 horsepower electric pump motors. To get power to the barge located 2,200’ into the lake, required (2) – large generators with (2) 50’ semi-trailers with electrical switchgear located close to 1000’ from shore in the Watershed Forest. The installation was complicated due to the wilderness topography of the lake and surrounding areas. The cooperative partnership created a practical design solution and installation plan for the temporary project. The final design consisted of (2) – 2M watt 480 volt generators, paralleled and connected to a 5,000 amp 480 volt switchgear. From there, (3) – breakers fed (3) – 480:4,160 volt step-up transformers. From each transformer Valley Electric installed 5,000 volt MC cables to each of the 3 barges. On the barge with the 4,160 volt, new pump motors, terminated to a disconnecting switch, then spliced to each of the (4) soft starts. For the other two barges, Valley Electric set up a 4,160:480 volt step-down transformer since the pumps and motors on those barges were 480 volt. The plan was set. The most critical milestone to execute the work before the existing water supply ran out – the lead-time and delivery for the cable and soft starts. To meet the short construction window of time, Valley Electric collaborated with their suppliers to acquire 10,000’ of rated 5,000 volt cable, delivered to the site within 1 week. The soft starts were locked-in and slated for delivery in 4 weeks.
The next challenge activity; installing the cable 2,200’ out and into the bottom of the lake, followed by an additional 1,000’ through the watershed’s forest steep slopes to the generator site. Orion Marine Group (OMG) developed a creative solution for this task. OMG weighed down the barge with ecology blocks on the stern side, allowing the bow able to get into 1’ of water. With one of the 9’ tall 6’ wide 14,000 pound spools loaded, on axels and jacks on the barge, the team drove the barge (with the help of a tug boat and two small skiffs) to the shore. From there, a wire feeder pulled the MC Cable from the spool and off the barge into 300’ of cable tray with cable rollers inside. There was an 8,000 pound tugger tied to a tree in the woods, energized by a portable generator, pulled the whole operation. Once the cable was pulled up to the location in the woods, we used the tug boat and skiffs to move the 50’ x 100’ barge backwards. This process was slow, but critical. The wire feeder had to match the pace of the boats. Not only to make sure that the cable wasn’t drug on the bottom, but to ensure it wasn’t spooled too fast, so to fall on itself and kink. Once the team arrived at the location, the cable was secured to large buoys to keep the ends out of the water while the temporary barges were still under fabrication.
While the barges were being prepped, Valley Electric focused attention on the power plant in the forest. The generators needed to be connected parallel to a 5,000 amp custom-made switchboard. With containers filled with 9,000’ of locomotive cable, the team had their challenges to meet the schedule. End connectors and cam lock splices needed to be installed along with termination ends. Once the generator site was ready, the work transition smoothly to the barges as they became available to work on. The crew then installed the soft starts, concrete vault (for splicing) and step down transformer. The entire project was completed and commissioned on-time, ahead of schedule for SPU to pump water to the City of Seattle. Work on the new project began after the peak water demands in October of 2015.
Chester Morris Lake Project Facts
Owner: City of Seattle (WA), Seattle Public Utilities
Electrical Contractor: Valley Electric – Everett, WA
General Contractor: Orion Marine Group – Tacoma, WA
Contract Vehicle: General Contractor/Construction Management (GC/CM)
Overall Project Value: $16 M | Electrical Contract Value: $2.5M
Temporary Project Duration: June 2015 – August 2015 (2 month duration)
New Project Duration: October 2015 – July 2016 (projected 9 month duration)