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Henderson Bay Project


Henderson Bay Towers Flanking State Route 302

Tacoma Power is working to replace the towers and power lines that cross Henderson Bay and Burley Lagoon. The plan is to replace the four lattice towers in the water with one monopole transmission tower (a straight, sleek, tubular steel structure), and to replace four of the lattice towers on land with four monopole transmission towers. In addition, Tacoma Power will be finding a new nesting site for the osprey that has used the Tacoma Power tower for many years. 

UPCOMING ACTIVITY 

Although much of the work on the project, such as permitting and design, has been behind the scenes. you will start seeing our crews doing prep work related to the replacement. 

Between July and September, we will:Installing bird deterrents

  • Trim trees along maintenance roads and the transmission line.
  • Improve an existing osprey platform site near Purdy Drive.
  • Mow the area where we will install the new poles
  • Install temporary wood poles adjacent to the new on-land tower locations
  • Install bird deterrents on some of the towers we plan to remove, with the exception of those with active nests


PHOTO SIMULATIONS

Take a look at photos of the existing towers and simulations of what the same area looks like under the new plan.   

 
 

Q & A

Why do the existing towers need to come down?
The towers and foundations have far surpassed their expected design life. At 90 years old, they are the original towers for the Cushman lines at Henderson Bay. 

Has Tacoma Power completed any similar projects?
Yes. The Henderson Bay crossing is the third of three marine crossings on the Potlatch Transmission Line that Tacoma Power will replace. The Narrows and North Bay crossings were replaced by Tacoma Power in 2006 and 2014. All were part of the original Cushman Hydroelectric Project dedication by President Calvin Coolidge in 1926. The transmission line transmits electrical power to Tacoma Power and Peninsula Light Company.

What is the replacement plan in and around Henderson Bay? 
The two towers in Burley Lagoon and the two flanking Highway 302 on the Purdy Spit will be removed; they will be replaced with one tower. Only one new tower is required in Burley Lagoon to do the work of the four original towers. The two towers on the land on the west side of Burley Lagoon, near Goodrich Drive, and the two towers on land on the east side, near the Purdy Substation, will also be removed. They will be replaced with four new towers. The six existing conductors will be replaced with six new conductors.

Why was this option chosen?
This option offers the least impact to the environment, people in the area and ratepayers.

What other options were considered and why weren’t they chosen?
• A direct one-for-one replacement of the eight towers would have increased construction duration and imposed unacceptable risk to the environment. 

• Removing all the existing towers from the water to span wires across both Henderson Bay and Burley Lagoon required extremely tall towers on the shore.

• Replacing the towers with an underground system under the lagoon would have a substantial impact on ratepayers.

Where will the new towers be located? What are they made of and what do they look like?
All of the new towers will be located on existing Tacoma Power property. The new towers are a tubular, vertical structure made of tapered steel. This design is now standard in the power industry and balances the needs of construction, maintenance, safety and appearance. 

Will the height of the power lines that cross the water be increased?
Yes. We will meet the current National Electric Safety Code (NESC) and the Washington Administration Code (WAC), which will result in an increased line clearance from 30 feet to approximately 50 feet during high tide. 

Why are new towers taller than the existing towers?
Since the original installation, electrical clearance requirements over the water and roadways have increased, requiring additional height for any new towers. In addition, the plan to reduce the number of towers in the lagoon increases the height of the remaining towers to adjust for the large span of wire. Tacoma Power will require a zoning code variance from Pierce County for any new towers for the project.  

What’s the process of tearing down the old towers? Will the water and sea life be disturbed in the process?

We will use cranes mounted on barges to install and remove the towers.

We will be consulting with the Washington State Department of Fish and Wildlife, the National Marine Fisheries Service, the State Department of Ecology, the U.S. Army Corps of Engineers and Pierce County during the permitting process to limit and address impacts on aquatic life and marine habitat. 

What will happen to the osprey that nest on one of the towers and the eagles that perch there on occasion?
Osprey like a nest that’s high enough to provide a view of the water and is near the shoreline. We have found a viable site that meets those qualifications and are making progress on getting approval to install a new pole on top of which we hope the osprey will nest. The site is a piece of Pierce County Parks and Recreation property at the west end of the Purdy Spit. We plan to install the pole by early 2018, prior to the osprey returning from their migration south.

In addition, we will improve the current nest platform site near Purdy Drive as a backup. 

If we are able to establish a new nest site, the existing nest will be moved to the new location after the osprey leave the nest to migrate south during the fall of 2017.. We are not allowed to remove a nest when it’s active, which is from the time birds begin to build or rebuild a nest until the young have fledged the nest and are no longer dependent on it for survival.

We were successful at relocating an osprey nest from one of our towers at North Bay and hope to achieve similar success with this project in the Burley Lagoon.

What’s the project schedule? 
Tacoma Power has been submitting permitting documents to Pierce County, the U.S. Army Corps of Engineers, and other state and federal agencies. Permitting is expected to continue through the summer of 2017.

If permits are obtained, upland construction will likely start in late 2017 and finish in  early 2018. In-water construction will likely start in July 2018 and finish in September 2018.

Will State Environmental Policy Act (SEPA) documents be available to the public?
As part of the SEPA, Tacoma Power has evaluated the environmental consequences of the project. Impacts have been or will be mitigated through the requirements in local, state or federal regulations. Tacoma Power issued a Determination of Nonsignificance (DNS), SEPA File # LU16-0185, on August 25, 2016.

Notice of public comment periods included a legal notice in The Peninsula Gateway and signage posted along the project corridor. 

Will removing the old towers on the Purdy Spit damage the bridge or roadway?
We are planning to remove the tower foundations on the spit. We will be working with the Washington State Department of Transportation and Pierce County to determine how much to remove to ensure the existing infrastructure is not compromised.

What will the traffic impact of demolition and construction be?
We understand that traffic is an important issue to those driving through the Purdy area and will be working with WSDOT and Pierce County to minimize traffic impacts to the community during construction. The majority of the demolition and construction activities will be done from barges. Tacoma Power believes that plan will require no road closures or lane reductions.

Who receives power from the transmission line that crosses Henderson Bay?
The lines are owned and operated by Tacoma Power.  The line provides power to Tacoma Power's system from our Cushman Hydroelectric Project. In addition, the line provides power to Peninsula Light's substations, thus serving Pen Light customers as well. 

How will power be provided during construction?
The existing power lines will be maintained during construction. As the new structures are installed, the power will be transferred to the new lines and structures.

For more information, contact Chris Gleason  at (253) 502-8222 or cgleason@cityoftacoma.org