A Closer Look: Why the Proposed Dam Is Not Designed to Generate Power


Within a year following the catastrophic 2007 Chehalis Basin flood, hydrologists were retained by the Lewis County PUD to model the flows from that flood if 65,000 acre feet of water flowing out of the Willapa Hills above Pe Ell was stored behind a dam.  

The findings, which have been reviewed and updated several times by the state of Washington, show that storing that much flood water would reduce the flood peak across the Chehalis Basin from Pe Ell, through the Twin Cities, past Montesano in Grays Harbor County and all the way to Cosmopolis.  

Immediately, talk of a dam in the mainstem of the Chehalis River triggered a fight between those more focused on the problem of a declining fishery and those who wanted flood protection for families and communities across the basin.  

This battle has been fought for nearly a century in the Chehalis Basin.  

It has included lots of fighting with every little progress. The three largest floods in more than a century have occurred in the last 35 years with increasing flood damage while the key salmon and steelhead runs continue to decline.

The fighting prompted then-Gov. Chris Gregoire to form the Governor's Chehalis Basin Work Group composed of three people from each side of the fish vs. flood fight with a charge to come up with a single plan to address both problems with fish enhancement and flood protection.  

Slowly, fighting turned into collaboration, a process that has continued to receive support from Gov. Jay Inslee and legislators on a bipartisan basis.

One decision was made early in the process: we are not going to build another fish-blocking dam, like the Elwah, on the Chehalis River.  

That led to a worldwide search by experts hired by the state to determine the latest technology and engineering to make emergency flood water storage compatible with aquatic species, especially salmon runs. The result of that research is a proposal from the Lewis County Flood Zone District to build a flood facility that does not have a reservoir and does not block fish passage, but does provide the basinwide flood reduction benefit.

The open gates at the bottom of the proposed structure will allow fish to pass upstream and down.  It will also mean that there is no reservoir except for a few weeks every seven or more years during a catastrophic flood. Having no regular reservoir also means that the facility could not generate hydro-electricity.  

The flow of the upper Chehalis River above Pe Ell fluctuates greatly during the year, but in summer and early fall months, the flows there are low enough that even if a dam was built holding a reservoir only 2-4 megawatts of power could be generated. 

That level of electricity would not warrant the $400 to $500 million cost of the facility.


This is the second installment of a new series focusing on the proposed dam on the Chehalis River. Installments in the ongoing series will be published in the Saturday edition of The Chronicle.