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Frequently Asked Questions

The information below is provided from studies and reports funded by the State of Washington and authorized by the Chehalis Basin Flood Authority.  The answers were prepared by the Flood Authority's subcommittee on outreach and education.

Q: 1. Why can’t the river be dredged?

A: It is not technically, environmentally, or economically feasible to dredge the entire Chehalis River for the purpose of mitigating Chehalis River flooding. The River has very little drop in elevation from Centralia to tide water and therefore, even if the River were dredged over this stretch it would do very little to lower flood levels. It would also be very costly to dredge the full length of the River, and it would be necessary to repeat the effort every few years. The environmental impacts of disturbing the streambed over long stretches of the River every few years is believed to be detrimental to fish and wildlife and not currently permitted by state and federal agencies. There is however the possibility of cleaning out certain localized gravel bars, log jams and debris which have built up over the years that could provide some minimal benefit to lower flooding in those areas. (Localized dredging is currently being done jointly by tribes, agencies, environmental and fishing groups on the Fraser River in Canada).

Q: 2. How much would upper basin water retention have lowered the 2007 flood levels for communities in the basin?

A: The water retention dam being studied by the Flood Authority and the State of Washington would, if built, be sited several miles above the Town of Pe Ell on the Upper Chehalis River. It would hold 80,000-acre feet of floodwater. That is enough water to cover 125 miles of land a mile wide and a foot deep. Hydrologists estimate that in the 2007 flood 300,000 acre feet of floodwater flowed past Grand Mound in Southern Thurston County on its way to Grays Harbor. That means that had the dam been in place in 2007 25% less water would have reached Grand Mound during the flood.

Hydrologic studies funded by the state and authorized by the Flood Authority show that had that facility been in place during the devastating flood of 2007 the peak of the flood would have been lowered over 8 feet in the Pe Ell/Doty area, 1.5 feet at Boistfort, over 3.5 feet at Adna, and 3.1 feet at Mellen Street in Centralia. The estimate of flood reduction at Grand Mound in southern Thurston County was 1.6 feet and 1.6 feet at Porter in eastern Grays Harbor county. Hydraulic modeling is being done now to answer the question as to flood level reductions along the rest of the Chehalis river to Aberdeen/Hoquiam.

Remembering that this is a reduction of flooding at the peak, when the water is spread out across a wide area, this would be a very significant reduction in the impact of the flood in these areas.

Q: 3. What were the results of the flood authority study of the geological stability of the proposed upper basin water retention facility? Has any state agency reviewed this study?

A: The geological study concluded that the upper basin water retention site was suitable for safely constructing an earthen dam. Both soil and rock and seismic conditions of the site and area were reviewed to determine suitability for construction of the dam. There are a number of engineering design features that would be included in the construction to make the dam meet state and federal dam safety requirements. The site has some historic loose slide material that would need to be excavated and removed prior to beginning construction. A grout curtain would need to be installed along the dam’s axis by pumping a cement to slurry into the ground rock formation to fill any voids also prior to beginning any earthen dam construction. If the decision is made to proceed with engineering and design of the earthen dam, addition geotechnical drilling would need to be conducted prior to completing the design.

The Washington State Department of Ecology’s dam safety division reviewed the report and concurred that the geologic study was consistent with dam feasibility standards at this stage of development.

Q: 4. Is the freeway going to be protected from flooding?

A: What is the Flood Authority Doing to Protect I-5?

Overview

The Chehalis Basin Flood Authority (FA) was created in response to the devastating flood of December of 2007. The flood, reported worldwide, devastated the homes and disrupted the lives of thousands of families. The FA commissioned a study which found the total economic loss caused by the 2007 flood was $938 million.[i] Of this total, over $300 million was lost to Washington State as a result of an extended closure of Interstate 5 (I-5). But most of the economic damage was borne by families, businesses, local governments, and communities in the Chehalis Basin.

The Chehalis Basin has experienced flooding since time immemorial. However, the floods are getting worse. The floods of 1990, 1996 and 2007 closed I-5 and, in turn, each caused more damage to families and communities in the basin.

The principal economic flood control interest of the state and federal governments is to protect I-5. Keeping that vital transportation corridor is imperative. Most citizens in the Chehalis Basin want a flood control plan that reduces the flood damage for their neighbors and communities between Pe Ell and Hoquiam. The best flood control plan will provide a basin-wide flood control benefit that both protects I-5 and reduces the level of flooding for families and communities along the Chehalis river.

The Governor and many state and local officials have called for a basin-wide solution to flooding. The Flood Authority’s stated purpose is to develop flood hazard mitigation measures throughout the basin and to identify and implement flood control projects in the basin.

Since being formed in 2008, the FA has sought input from every citizen in the basin and from tribal, local, state and federal agencies as to options for basin-wide flood control plans that will both meet the state and federal interest in protecting I-5 and provide a basin wide plan that will reduce the impact of devastating floods for people in the basin.

The Twin Cities Plan

After nearly four years of work by the FA, including dozens of public meetings only two measures have been proposed and studied that hold hope of protecting I-5 in future floods from the kind of enormous flooding that devastated the basin and closed I-5 .

The first plan, dating at least as far back as 1980, was the Army Corps of Engineer plan to build 11 miles of new levees in the Chehalis River floodway through Chehalis and Centralia.

In 1946 the Army Corps of Engineers was authorized by President Truman and Congress to reduce the impact of flooding in the Chehalis basin. Since the building of I-5 the Corps planning focus has been to protect the interstate. The Corps presented a design to build miles of new levees to the Centralia city commission in 1980[ii] and this basic plan was authorized, but not funded for construction, by Congress as the Centralia Flood Damage Reduction Project (“Twin Cities project”). The Twin Cities project proposed to build 11 miles of new levees to protect I-5.[iii]

Opposition to the Twin City project is extensive in the Chehalis Basin. The following municipalities and organizations passed Resolutions asking that the Twin Cities plan be shelved in favor of the study of upper basin water retention: Cities of Aberdeen, Montesano, Chehalis, Centralia, Pe Ell, Cosmopolis, Oakville, Ocean Shores, Westport, and Napavine. Grays Harbor PDA (Satsop), Grays Harbor Chamber of Commerce, Thurston County Farm Bureau, Chehalis Industrial Commission, Centralia-Chehalis Airport Board, Port of Centralia, Port of Chehalis, Boistfort Fire District #13, Lewis County EDC, Combined Lewis County (Pomona) Grange, Lewis County Board of Commissioners, Centralia-Chehalis Chamber, Mayors of Grays Harbor.

Work on the Twin City plan was shelved by the Corps in 2011 after the Corps determined that the proposed project would not have protected I-5 during the 2007 flood, would have increased flooding upstream and downstream and, costing over $200 million, does not pass the Corps cost-benefit test.[iv]

Upper Basin Water Retention

Four years after the devastating flood of 2007, this leaves only one option that has been proposed to protect I-5 and would provide a basin-wide solution to provide significant flood reduction for the families and communities in the basin. This option is to add water storage in the upper Chehalis River Basin. Specifically, the state has funded and the FA has approved studies of a dam and reservoir up-river from Pe Ell with the capacity to store 80,000-acre feet of flood water.[v] 80,000-acre feet is a volume of water that reaches 125 miles long, a mile wide and a foot deep.

A study by Northwest Hydraulic Consultants found that, had 80,000 acre feet of flood water been stored during the 2007 flood, that the peak level of flooding would have been reduced by more than 8 feet at Doty, 3.1 feet at Mellen Street,1.6 feet at Grand Mound and Porter in Grays Harbor county.

Other studies are being completed on water retention and an Environmental Impact statement would be needed before construction.

Natural Solutions

The Flood Authority retained Earth Economics to examine the potential for natural, non-man made solutions to flooding. Earth Economics also received a grant from the U.S. National Science Foundation to help underwrite their study. The mission of Earth Economics is to “meet the challenges of the 21st century achieving the need for just and equitable communities, healthy ecosystems and sustainable economies”.

This study[vii] concluded that “that the best investments for achieving flood protection are likely a combination of natural capital (such as floodplains) built capital (such as dams and levees) and social capital (land use planning, moving flood prone built assets, early warning systems).” Earth Economics found that 87% of the basin today is forested, with more land in agriculture and pasture than is “barren and developed”. Out of 1.9 million acres 96% of the basin’s land is undeveloped. 3.8% of the land in the basin is barren or developed.

Other studies are being completed on water retention and an Environmental Impact statement would be needed before construction.

[i] Chehalis River Flood Funding Study – Economic Benefit Analysis by FCS Group 2/7/11.

[ii] Levee Plan Stirs Little Enthusiasm by Audrey Lee – Chronicle Staff, 7/10/80 edition of the Daily Chronicle.

[iii] Corps Levee Map.

[iv] Centralia Flood Risk Management Project, DRAFT closeout report, September 2011 (this report is in draft form. The document is subject to changed pending additional technical review)

“Good Riddance to Army corps Levee Project” by The Chronicle Editorial Board in the 7/23/11 edition of the Chronicle.

[v] Chehalis River Water Retention Facilities Potential Study by EES Consulting, February 2009.

[vi] Chehalis River Upstream Storage Alternatives: Effect On Flooding, by Northwest Hydraulic Consultants, 1/23/09.

[vii] Flood Protection and Ecosystem Services in the Chehalis River Basin by Earth Economics, May 2010.

Q: 5. Who will pay for all the proposed flood-protection measures?

A: I-5 is a transportation artery of national and state importance. A Flood Authority study found that the 2007 flood caused over $938 million dollars of damage with over $500 million of that being borne by families and communities in the basin and more than $300 million because I-5 was closed. We believe that the federal and state government will contribute to a basin wide flood control plan for the Chehalis basin if that plan includes protection of I-5. Such a plan, if it includes other localized flood control elements will also, likely, need the support of local governments in the basin.

Q: 6. What was the conclusion of the Earth Economics study funded by the flood authority as to whether natural measures alone can significantly reduce flooding in the basin?

A: Natural Solutions

The Flood Authority retained Earth Economics to examine the potential for natural, non-man made solutions to flooding. Earth Economics also received a grant from the U.S. National Science Foundation to help underwrite their study. The mission of Earth Economics is to “meet the challenges of the 21 st century achieving the need for just and equitable communities, healthy ecosystems and sustainable economies.” This study concluded that “. . . that the best investments for achieving flood protection are likely a combination of natural capital (such as floodplains) built capital (such as dams and levees) and social capital (land use planning, moving flood prone built assets, early warning systems)." Earth Economics found that 87% of the basin today is forested, with more land in agriculture and pasture than is “barren and developed.” Out of 1.9 million acres 96% of the basin's land is undeveloped. 3.8% of the land in the basin is barren or developed. [Source = “Flood Protection and Ecosystem Services in the Chehalis River Basin” by Earth Economics, May 2010.]

Q: 7. What is the result of the Flood Authority study of the economic loss due to the 2007 flood?

A: The Chehalis Basin Flood Authority (FA) was created in response to the devastating flood of December of 2007. The flood, reported worldwide, devastated the homes and disrupted the lives of thousands of families. The FA commissioned a study which found the total economic loss caused by the 2007 flood was $938 million.[i] Of this total, over $300 million was lost to Washington State as a result of an extended closure of Interstate 5 (I-5). But most of the economic damage was borne by families, businesses, local governments, and communities in the Chehalis Basin.

The Chehalis Basin has experienced flooding since time immemorial. However, the floods are getting worse. The floods of 1990, 1996 and 2007 closed I-5 and, in turn, each caused more damage to families and communities in the basin.

Q: 8. I read about the Elwha dam removal, does that mean that new dams aren’t being built?

A: In the last 20 years, 213 new dams have been built in Washington, Oregon and California according to the National Inventory of Dams database. The ten largest of the recently built dams are listed below:

McGuire, Olivenhain, Pony Creek, and Diamond Valley Lake dams are all water supply/irrigation dams. Seven Oaks dam in California is a dam designed for flood control. Trask River Barney Reservoir and Los Vaqueros dam are both water supply reservoirs, and Cowlitz Falls and Echo lake dams are hydroelectric dams.

In addition to those that are newly built, the Federal Energy Regulatory Commission reports that new permits have been filed to build 15 additional new small hydro or pumped storage facilities in Oregon, Washington and California:

Here is a link on Google maps with all 25 of the above structures. Where you see blue dots are existing structures, and the yellow pins are the proposed structures: http://g.co/maps/t5r8h

Q: 9. Why is the Flood Authority not putting out for bids for facilitation? Shouldn't others have the opportunity to apply for the work that SBGH Partners and Gordon, Thomas and Honeywell are now providing?

A: Under Washington law, certain services are required to be opened to bid, including architectural and engineering services. Facilitation services, like those of attorneys and mediators, generally are not opened to bid because of the unique nature of the service. In this instance, the individual selected to facilitate for the Flood Authority, Ms. Lara Fowler, had attended the Flood Authority meetings for years, was known to and respected by all members, and understood the history and nature of the issues confronting the Authority at a critical point in time. She had previously worked with SBGH Partners, a local firm familiar to many members, and the Authority felt that they together provided an experienced and knowledgeable team that could immediately replace ESA, the former facilitator, when it gave notice of its resignation.